# Spitfire MK.XIV and La-7



## Soren (Mar 12, 2005)

*Spitfire Mk.XIV*






Engine: Rolls-Royce Griffon 65.
Power: 2035 hp.
Max Speed: 437 mph.
Max Range: 457 miles.
Empty Weight: 2994kg. 
Max.Weight: 3856kg. 
Service ceiling: 13560m.
Wing Span: 11.23m.
Wing Area: 22.48m2. 
Armament: two 20mm cannons and four 7.7mm machine guns.

*Lavochkin La-7*





Engine: ASh-82FN.
Power: 1,850 hp.
Max speed: 422 mph.
Max range: 394 miles.
Empty Weight: 2,605kg.
Max. Weight: 3,265kg.
Service ceiling: 10,750m.
Wing Span: 9.80m.
Wing Area: 17.59m2.
Armament: three 20mm Beresin B-20 ShVak nose cannons.
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Wich one would you bet your money on in a Dogfight ?


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## mosquitoman (Mar 12, 2005)

I'd take the Spit but what were the speed of roll and turning circle like, they're important in a one on one dogfight


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## KraziKanuK (Mar 12, 2005)

There was a mock dogfight in Italy between a Spit (Mk unknown) and a Soviet (Yak ???) fighter that had flown there by a defecting pilot. The Spit got trounced.


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## cheddar cheese (Mar 12, 2005)

Id have to go with the La-7 on this one.


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## Soren (Mar 12, 2005)

They are probably both going to be turning on an equal rate, however one gets the roll-rate to its advantage. 

The Speed advantage goes to the Spit.XIV though. 

About armament, well I'll have to give the Spit.XIV the edge there aswell.

Climb-Rate also goes to the Spitfire.

To me the Spitfire XIV seems very much superior.


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## mosquitoman (Mar 12, 2005)

The only advantage that the La-7 has is that it has a radial engine so it could probably take a bit more damage in that area


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## the lancaster kicks ass (Mar 13, 2005)

not much use if you kill the pilot though or take off the tail.........


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## delcyros (Mar 13, 2005)

A hard choice. Well, acceleration would have gone to the La-7, but only slightly. Wingload would go to the Spit (but slightly, also). Durability to the La-7 thanks to the radial engine as mentioned by moskitoman (probably). Speed and climb would be on the Spit (especially) in higher altitudes. What about the weapons? The 23 mm Shvak was a great wepon, the La-7 concentrates much firepower in the nose, also. The Spit was a bigger target to aim at but probably the better energy keeper of both. I think it depends on the pilot.


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## Soren (Mar 13, 2005)

Well strictly talking the two machines, i think the Spit XIV is very much superior. 

The Spit XIV could dominate the fight, as it was faster and climbed better, and it also turned just as tightly if not tighter than the La-7 ! About roll rate, well im not sure about that one. 

Armament goes to the Spit, eventhough the La-7 had great armament itself, its doesnt beat the two Hispano's and four brownings on the XIV. The XIV could actually also carry two 50.cal's instead of the four .303 Brownings.

I don't see how the La-7 could ever win the fight over the Spit XIV, if both had equally skilled pilots flying them. (Except if the La-7 jumps it from above maby)


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## delcyros (Mar 13, 2005)

Well I don´t see why the Spit should win that easy against the La-7. Because it is a soviet plane? Nono... for such a clear statement you have to proof that:
1.) The Spit turns better at all speeds and in every altitude
2.) The Spit rolls better at all speeds and in every altitude
3.) The Spit has a speed and acceleration advantage in most circumstances
4.) The Spit is superior in climb and dive under all possible circumstances
5.) The Spit can take much more damage 
6.) The Spit has much more firepower
7.) The Spit has a much superior handling, esspecially at high speeds

So what? You don´t proof it, or am I wrong? 
The armament of the Spit is quite a good armament, but I understand that the La-7 has a comparable, if not a better one. It has three 23 mm guns all in the nose with enough ammunition (and not two 20 mm with a few seconds ammo). That concentration works for a better gun platform (remember they once wanted the Spit to carry four of the 20mm, but they had to reduce it to two, because it wasn´t stable enough) as well as a much more devastating punch. And for the agility: Wingload speaks (slightly) for the Spit, powerload (slightly) for the smaller La-7. Who wins?


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## DAVIDICUS (Mar 13, 2005)

The 20mm's that the La-7 carried had a higher rate of fire but fired lighter projectiles at a slower velocity. (Terminal basllistics are what count though and I don't know how much the 300 yard retained velocitywas for the 20mm's that both aircraft carried.) 

http://www.geocities.com/CapeCanaveral/Hangar/8217/fgun/fgun-pe.html

It doesn't appear that there's any significant difference between the lethality of these two aircraft. I do, however, think there's an advantage to having three 20mm's all housed in the nose.


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## Anonymous (Mar 14, 2005)

La7 below about 12,000 feet, Spitfire above about 16,000 feet, anybody's game from 12-16,000 feet.

The La7 (I assume we mean the -FNV model with 3 x B20 cannon) was tweaked for lower altitude performance, the Spitfire for higher altitude performance. The La7 defanitely outrolls the Spit at speed.

As far as guns go, they are about equal in my view. The Spitfire has a slight range advantage, and its 20mm are more devestating, but the LA has twice the volume of 20mm fire, but the Spitfire also has 2 x .50 BMGs, but the La7 guns are in the nose and are much more solidly mounted and have much less recoil (countering the Hispano velocity advantage somewhat)... who can say which is better?

At 300 yards the Hispano II velocity was about 673 m/s, about 76% of its 880 m/s initial velocity. The B-20 velocity at 300 yards was about 506 m/s, about 66% of its initial 770 m/s velocity. --- these figures are for sea level, at altitude velocity loss would be lower.

=S=

Lunatic


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## Soren (Mar 14, 2005)

Well the Spit has low wing-loading and speed to its advantage, plus it has better allround visibility from the cockpit.

The Spit will also climbs better, with its 2035hp engine and five-bladed propeller. 

The roll-rate goes to the La-7 at high speeds, but at slow-moderate speeds they are both going to be pretty equal. 

The turning capability of the Spit will probably be superior to the La-7's, although it is close. The German Bf-109F-G2 series could outturn the La-7 at slow-moderate speeds (However not in sustained turns of over 360 degree's). However because of its wing-slats the La-7 will probably be at an advantage over the Spit at slow speeds.

About armament, well I'd go for the Hispano's, as they are better suited for the Fighter vs Fighter role.


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## the lancaster kicks ass (Mar 14, 2005)

i'd go for the spit as well.........


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## Anonymous (Mar 14, 2005)

I seriously doubt the Spit has the power advantage at low altitude. I'll try to find some climb and speed charts to compare the two planes, but I suspect the La7 was noticably faster to 10,000 feet. Also, the La7 is the more aerodynically clean design - it had a very aerodymanic cowl design and the Spit XIV is pulling two HUGE scoops (lets call them air brakes) under its wings for cooling.

While the Spit may turn a little better (debateable), the La7 was definitely more responsive at speed.

The Hispano's are the better guns for bombers, not the B-20's. The reason is that the useful range against fighters is always much shorter, and less destructive capability is required to kill a fighter than a bomber. The La7 is twice as likely to land the first 20mm hit in a mutually aware dogfight and the .50 API (or Incendiary) are effectively ball ammo against wood.

Also, that 5 bladed prop is of no real advantage at lower altitides. The whole point of the thing is that it can turn at lower speed to avoid prop-mach issues at high altitude (where mach speed is lower). Down low, all that matters is the thrust generated by the prop, and 4 blades (or even 3) can be advantagous because they interfere with each other less. If more blades were all advantage, every plane would have had an 8 bladed prop right?

=S=

Lunatic


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## the lancaster kicks ass (Mar 14, 2005)

yes but at the same time the 5 bladed prop must have been better than the 3 and 4s, or we wouldn't have used them, we must have used them for good reason, we're not stupid..............


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## Anonymous (Mar 14, 2005)

the lancaster kicks ass said:


> yes but at the same time the 5 bladed prop must have been better than the 3 and 4s, or we wouldn't have used them, we must have used them for good reason, we're not stupid..............



Better for high altitudes. And even so it was somewhat questionable how much better it was.

The higher the plane goes, the lower the maximim RPM of a given diameter prop, otherwise the tip of the prop will go supersonic and create a shock wave and ruin performance (and maybe even be damaged). So you want to reduce either the RPM of the prop, or the diameter, or both. But this reduces the amount of thrust from the prop. So one solution is to add more blades. The down side of this is that the blades are closer together, which means the turbulence from one blade may interfere with the one behind it.

After lots of study, the generally accepted solution was a large four bladed prop with very wide blades - the "paddle prop", geared to a lower rpm. This gave good low altitude performance and good high altitude performance - but it required more torque to drive it - something that the merlin and griffon engines did not do so well (i.e. they had comparatively poor torque curves below peak rpm as compared to the R-2800 for example). The ability of the airframe to handle the torque was also an issue (so the plane does not rotate around the prop), and longer wider blades accentuate this.

Finally, on the Spitfire, a larger prop geared to a lower speed was not really an option, it lacked the ground clearance for such a prop.

=S=

Lunatic


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## pasoleati (Mar 20, 2005)

Do you any proof for the torque claims? Naturally the R-2800 has more torque as it has more power at slightly lower rpm but it is pure hogwash to speak about torque curves as they are meanigless with constant speed props. And remember, an engine having a reduction gear ratio of .25 and 2000 hp at 4000 rpm has the same torque available from propeller shaft as does an engine with reduction gear of .5 and 2000 hp at 2000 rpm (i.e. propeller runs at 1000 rpm in both cases).

And where do you get the claim that 4-blades is the absolute best?


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## Chocks away! (Mar 20, 2005)

I'd say the la-7 wins at low altitude, as it was proven better than any western piston engined fighter there. The spitfire was probably better at high altitude. Same when comparing the La with German planes. By the way, isn't the plane in the picture a lavochkin la-9 ?


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## Chocks away! (Mar 20, 2005)

RG_Lunatic said:


> the lancaster kicks ass said:
> 
> 
> > yes but at the same time the 5 bladed prop must have been better than the 3 and 4s, or we wouldn't have used them, we must have used them for good reason, we're not stupid..............
> ...


 as in the late bf 109 s correct?


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## cheddar cheese (Mar 20, 2005)

> By the way, isn't the plane in the picture a lavochkin la-9 ?



Youre right. It is an La-9


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## Anonymous (Mar 20, 2005)

pasoleati said:


> Do you any proof for the torque claims? Naturally the R-2800 has more torque as it has more power at slightly lower rpm but it is pure hogwash to speak about torque curves as they are meanigless with constant speed props. And remember, an engine having a reduction gear ratio of .25 and 2000 hp at 4000 rpm has the same torque available from propeller shaft as does an engine with reduction gear of .5 and 2000 hp at 2000 rpm (i.e. propeller runs at 1000 rpm in both cases).
> 
> And where do you get the claim that 4-blades is the absolute best?



Constant speed props are only constant speed at a given engine RPM. (As I'm sure you know) The idea is you increase the pitch of the prop to achieve more thrust, and increase the air/fuel flow to the engine to maintain the same rpm. My point was you could not reduce rpm on the merlin/griffon at high altitudes and still get strong performance from the engine/prop on a large paddle type prop, because the torque curve falls off more sharply below peak power.

Increasing the reduction gear ratio would indeed slow the prop relative to the rpm, but doing so would sacrifice low alititude performance in favor of high altitude performance. Since it was desirable on the Spit XIV to have good performance at all altitudes, it was desireable to have one prop RPM that would work well at both - thus the smaller radius prop with more blades.

I never said it the 4 bladed prop was the absolute best, just that it was the more generally used solution. On R-2800 powered planes, they could back off the rpm a little bit without much loss of torque. The Germans chose to use a 3 bladed prop with very fat paddles for their Ta-151H.

The truth is there were many tradoffs to be considered, and very little was known about high altitude performance. The 5 bladed prop was a good solution for the Spitfire XIV, give all the considerations - especially the lack of ground clearance for a larger radius prop. It is very clear the British were not entirely satisfied with this solution, they kept experimenting with different Spitfire prop setups till well after the end of the war.

My only point in this thread is that 5 blades are not necessarily better than 4, or even 3 blades.

=S=

Lunatic


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## pasoleati (Mar 20, 2005)

I simply don´t buy your theory of torque! I don´t know about Griffon, but max boost was allowable with the Merlin down to 2850 rpm (normal max rpm 3000). I am aware that in e.g. the P-61 pilot manual it is mentioned that speed will be better at very high altitude if the rpm is reduced from 2700 to 2600 (B-series engine), but this simply due to tip speed problems. Since most Griffon aircraft had smaller diameter props running at speed not higher than those of R-2800 powered aircraft, I don´t it was any problem with them. At least it is not reported in books like Spitfire the History that has huge amount of such data.

As for 5-bladers, the Sea Fury has one. In my opinion the best answer would have been contra-rotating props. Too many sources tend to claim that the performance increase was not worth extra complication. In my opinion, that is not the point. Consider the F4U, numerous aircraft and pilots were lost because of the torque roll at slow speed. With contra-props, this would be history. Also directional trim changes would a thing of the past. E.g. the British report on the Spitfire fitted with a contra prop mentions that it was possible to to fly from take-off the landing without touching the rudder bar at all. A most valuable feature, imho.


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## Anonymous (Mar 20, 2005)

pasoleati said:


> I simply don´t buy your theory of torque! I don´t know about Griffon, but max boost was allowable with the Merlin down to 2850 rpm (normal max rpm 3000). I am aware that in e.g. the P-61 pilot manual it is mentioned that speed will be better at very high altitude if the rpm is reduced from 2700 to 2600 (B-series engine), but this simply due to tip speed problems. Since most Griffon aircraft had smaller diameter props running at speed not higher than those of R-2800 powered aircraft, I don´t it was any problem with them. At least it is not reported in books like Spitfire the History that has huge amount of such data.



But that's exactly the point. The smaller radius 5 bladed prop of the Spitfire did not need to reduce rpm. My point is that a 15% reduction in rpm on the Griffon results in a larger loss of torque than on the R-2800, so it is desireable not to have to reduce the RPM. On the R-2800, you can reduce the RPM and increase the prop pitch and sustain higher thrust without bogging down the engine resulting in dropping RPM. Remember at peak power, horsepower and torque are synonomous. Below peak power however, they are not. More cubes means a better off-peak power torque/hp curve. That's why the constant speed props were so valuable in the first place - because the engine could be held at its peak power where the torque and hp curves meet.



pasoleati said:


> As for 5-bladers, the Sea Fury has one. In my opinion the best answer would have been contra-rotating props. Too many sources tend to claim that the performance increase was not worth extra complication. In my opinion, that is not the point. Consider the F4U, numerous aircraft and pilots were lost because of the torque roll at slow speed. With contra-props, this would be history. Also directional trim changes would a thing of the past. E.g. the British report on the Spitfire fitted with a contra prop mentions that it was possible to to fly from take-off the landing without touching the rudder bar at all. A most valuable feature, imho.



On this we are in total agreement. Contra-rotating props would have been far superior to adding more blades or larger paddle blades. They were however somewhat complicated and the kinks still had to be worked out of how to design the props so the front prop would not interfere with the back prop. These issues just didn't get resolved in time for WWII.

=S=

Lunatic

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## pasoleati (Mar 20, 2005)

Are you sure? Cubic capacity has no effect here as such. E.g. an engine producing 2000 hp from 36 litres at 2700 rpm produces exactly the same torque as one producing 2000 hp from 46 litres at 2700 rpm. Remember, torque is directly proportional to power but inversely proportional to rpm assuming constant MAP operation. I have examined dozens of aero engine handbooks and in none of them a torque curve has been presented.


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## Anonymous (Mar 20, 2005)

pasoleati said:


> Are you sure? Cubic capacity has no effect here as such. E.g. an engine producing 2000 hp from 36 litres at 2700 rpm produces exactly the same torque as one producing 2000 hp from 46 litres at 2700 rpm. Remember, torque is directly proportional to power but inversely proportional to rpm assuming constant MAP operation. I have examined dozens of aero engine handbooks and in none of them a torque curve has been presented.



Aero engines handbooks almost never go into any kind of torque curve info, since the power is always considered at peak power RPM.

I agree the 46 liter engine and the 36 liter 2000 HP 2700 rpm engines bouth produce the same torque at 2700 rpm. The torque curve issue comes in to play when you back off from the peak. The 46 liter engine will produce more torque at 2000 rpm than the 36 liter engine.

My experiance with this comes mostly from cars. Believe me, a chevy 327 can be made to put out the same 400-425 HP that the 396 or 427 could (though they could be pushed even futher) fairly easily. But the torque curves were entirely different. The 396 might make 400 HP at 6000 rpm, the 327 at 7500 rpm. But the 396 would make a lot more torque at 3000 rpm than the 327 did at 3750 rpm. The smaller displacement engines are more sensitive to the torque/hp curves.

=S=

Lunatic


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## pasoleati (Mar 23, 2005)

RG, your logic is utterly flawed here. You are comparing unspercharged car engines to supercharged engines which is way off the base. First, torque and power curves for can engines are done with full throttle, i.e. at constant MAP. In aircraft engines this is strictly no-no. They won´t tolerate full boost for much below max rpm. Therefore, with a supercharged aero engine the torque curve allways starts reducing with rpm as the MAP and therefore IMEP is lowered accordingly. I.e. the curve is completely different is shape in comparison with that of a unsupercharged car engine. 

And it is also a fact that bigger engine has no greater torque rise if all the other design parameters are the same. And to add to the insult, a two litre turbocharged engine giving 200 hp has greater torque and torque rise than a 4 litre unsupercharged engine giving 200 hp. 

Thse are the facts.


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## Anonymous (Mar 24, 2005)

pasoleati said:


> Your logic is utterly flawed here. You are comparing unspercharged car engines to supercharged engines which is way off the base. First, torque and power curves for can engines are done with full throttle, i.e. at constant MAP. In aircraft engines this is strictly no-no. They won´t tolerate full boost for much below max rpm. Therefore, with a supercharged aero engine the torque curve allways starts reducing with rpm as the MAP and therefore IMEP is lowered accordingly. I.e. the curve is completely different is shape in comparison with that of a unsupercharged car engine.
> 
> And it is also a fact that bigger engine has no greater torque rise if all the other design parameters are the same. And to add to the insult, a two litre turbocharged engine giving 200 hp has greater torque and torque rise than a 4 litre unsupercharged engine giving 200 hp.
> 
> Thse are the facts.



The curve is the same for supercharged engines. As long as you are comparing like to like there is no difference. Also, I'd love to see your source for a turbocharged 2L engine of giving greater torque than a normally aspirated 4L engine given the same peak HP.

=S=

Lunatic


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## pasoleati (Mar 24, 2005)

It is easy. Just go to some car maker site that has models with and without supercharging. Then calculate power/torque figures for both. You will see that the smaller turbocharged engines develop more max torque per hp (max hp).


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## Anonymous (Mar 24, 2005)

pasoleati said:


> It is easy. Just go to some car maker site that has models with and without supercharging. Then calculate power/torque figures for both. You will see that the smaller turbocharged engines develop more max torque per hp (max hp).



That is not the torque curve. The torque curve show torque vs. rpm at different rpm. And in this case we are really concerned with "unused torque", which represents the ability of the engine to rev up to higher rpm quickly, or to sustain rpm under a higher load.

Anyway, what would that matter, both aircraft engines under consideration are supercharged.

=S=

Lunatic


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## pasoleati (Mar 24, 2005)

Well, get a copy of Torque Meter issue 1, volume 3 and check page 26 (TM is the house journal of the "Aircraft Engine Historical Society"). On that page you can find a torque curve for the Allison V-1710-81A. The data is from "the demo runs Bud Wheeler did at Oshkosh and are probably the first set of performance curves on an Allison since the 1940s" according to Daniel Whitney, the leading authority on the Allison. This torque vs. rpm curve clearly shows a steadily DECREASING torque with decreasing RPM. The shape is completely different from your beloved V-8s. I don´t think there can be a better rebuttal of those silly torque claims of yours!


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## Anonymous (Mar 24, 2005)

Why is that? 

Normally the torque curve climbs early in the rpm band and then starts down, the HP curve climbs more slowly and continues to climb with rpm until it crosses the torque curve (and usually it does not turn down within engine rpm limits).

I never said torque would increase with RPM, only that more cubes equals more HP. Used torque always increases with RPM, but available torque (the ability to accelerate rpm) does not.

=S=

Lunatic


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## Iskandar Taib (Mar 25, 2005)

The thing though is.. why decrease RPM at all? If you want to use the paddle blader (and have the ground clearance) at a lower RPM, just use a lower gear ratio on the reduction gear. The torque below operating RPM doesn't matter, since you don't need to run below operating RPM anyway.


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## Soren (Mar 25, 2005)

RG i dont understand how you can say that the La-7 is more aerodynamic, as it is a Radial engined fighter !

Sure the intakes under the Spit's wings induce drag, but even more so does the big flat front nose of the La-7's radial engine. On the other hand the Spit Mk.XIV's nose section is very areodynamic !

The Spitfire Mk.XIV is actually a very areodinamicly clean aircraft:






About the five bladed propellar, well it was a big advantage at High alt, and it was also less noisy. 

The Spit Mk.XIV is superior to the La-7, no doubt, even at low alt. The Spit XIV is faster, climbs better at all altitudes, it most likely turns better, and it has equal roll rate. 

At sea-level the Spit XIV could climb with 4,800-5,200 ft/min depending on the type, something the La-7 couldnt hope to match. At best the La-7 would climb with 3,608 ft/min.

The Spit XIV was also noticably faster with 721 km/h vs the La-7's 680 km/h.

I know wich plane i would want to be sitting in, in a clash between these two.... The Spit Mk.XIV without doubt !


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## the lancaster kicks ass (Mar 25, 2005)

nice profile................


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## Anonymous (Mar 25, 2005)

Soren,

Yes the Spit 14 running on 150 octane fuel was about 10-12 mph faster than the La7-FN running on 95 octane fuel at about 6500 feet. It climbed a little better too. 

We have few figures for the -FN(V) version, but know it could sustain WEP power for 10 minutes, as opposed to 2 minutes for the -FN version. Reliable speed data is unavailable, but we know the standard (normal power) sustained speed was 660 kph (410 mph) at 6000 meters, 40 kph higher than that of the -FN versions which was 620 kph (385 mph) at that altitude. The maximum speeds you are using are for the La7-FN version, which was 655 kph (407 mph) at 6100 meters. Obviously the -FN(V) version would be faster, probably about 430 mph at 6100 meters. The La7-FN(V) was probably as fast as the Spitfire below 18000 feet, and faster below 12,000 feet.

As for climbs, the La7-FN(V) climbed from wheels up to 5250 feet (1600 meters) in 1 minute, an RoC of.... 5250 fpm. It climbed to 9843 feet (3000 meters) in 2.2 minutes, an RoC of 4474 fpm. It climbed to 13123 feet (4000) meters in 3.2 minutes, an RoC of 4100 fpm. It climbed to 16404 feet (5000 meters) in 4.3 minutes, a ROC of 3815 fps. So, at least below about about 16000 feet, the La7-FN(V) climbed every bit as well as the Spitfire - and it could sustain this for 10 minutes, as opposed to the 5 minutes of the Spitfire. Also, it was allowed 30 second boosts of 2600 rpm performance, giving even better climb and speed.

As for manuver, the La7 was a very manuverable plane. It was considered much more manuverable than both the 190 and the 109. Roll rate was very good at all speeds up to about 400 mph. Turn rates were also excellent and energy retention in a turn was quite good. The La7 could exceute a 225 mph 360 degree turn at 1000 meters in under 20 seconds in either direction with no loss of speed.

The La-7 had one of the most streamline cowls of any radial engined fighter of WWII. It was more streamlined than any of the FW/TA designs, and comperable to the P-47J and Tempest II. It certainly had a little more nose drag than the Spitfire, but it had no wingscoop drag.

The La-7 also had leading edge slats, I'd think you'd be in love with it Soren!

=S=

Lunatic


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## Iskandar Taib (Mar 25, 2005)

Yeah, a lot of people are fond of talking about radiator drag, but one has to remember that the inlet for cooling air for the radial engine produces at least as much drag, maybe even more. The Spitfire used the Meredith effect to recover some of the energy lost to the drag. and I don't see any evidence that the Lavochkin does so.

Note that for radial engined racers, they cut down on the cooling inlet to almost nothing. 2 inches in the case of Furias. See:

http://www.supercoolprops.com/ARTICLES/gwhite.htm


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## GermansRGeniuses (Mar 25, 2005)

Hmmm, I wonder if they use Nitro in the cooling inlets...


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## pasoleati (Mar 25, 2005)

RG_Lunatic said:


> Why is that?
> 
> Normally the torque curve climbs early in the rpm band and then starts down, the HP curve climbs more slowly and continues to climb with rpm until it crosses the torque curve (and usually it does not turn down within engine rpm limits).
> 
> ...



What are you babbling about "used" and "available" torque? Do you really understand what you write? Face this: if an engine is running at x rpm at full throttle, there is no "available" torque to accelerate anything unless the load is reduced!!! You are completely mixing part throttle and full throttle operation and inventing garbage like "available" torque. 

Now, in ordinary car engines the power decreases relatively steadily as the rpm is decreased from the full power rpm down. On the other hand, torque curve starts rising with decreasing rpm (from that full power rpm) until it reaches the peak at a certain point that is highly variable with each engine. All this at FULL THROTTLE, i.e. CONSTANT MANIFOLD PRESSURE. 
In supercharged aero engines the curve is of different shape as it CANNOT BE OPERATED AT CONSTANT FULL POWER MAP EXCEPT AT HIGH RPM. Get it???


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## Anonymous (Mar 26, 2005)

Iskandar Taib said:


> Yeah, a lot of people are fond of talking about radiator drag, but one has to remember that the inlet for cooling air for the radial engine produces at least as much drag, maybe even more. The Spitfire used the Meredith effect to recover some of the energy lost to the drag. and I don't see any evidence that the Lavochkin does so.
> 
> Note that for radial engined racers, they cut down on the cooling inlet to almost nothing. 2 inches in the case of Furias. See:
> 
> http://www.supercoolprops.com/ARTICLES/gwhite.htm



First off, the Spitfire did not use any significant "Meredith Effect". Just because it's a liquid cooled engine radiator does not mean it exploits the effect. To achieve any significant Meredith effect, the system must include an expansion chamber prior to the radiator, a compression chamber after the radiator, and a thrust regulating exhaust nozzel. And finally, the exhaust flow must be directed into the vacuum wake of the fuselage to cancel out some or all of the parasitic drag. The Spitfire (and 109) lacked any of these features. Look in detail at the cooling system of the P-51 (as outlined in other threads on this forum) or the Mosquito to see examples of cooling systems which do significantly exploit this effect.

Secondly, radial engines can exploit the effect, though I'm not sure exactly what the mechanism is. I know the Zero gained about 5-10 mph from the effect, and this part of the desing was stolen and transfered to the F4U Corsair for a gain of 10-15 mph. It may also have been exploited by the Soviets on the LA7 design. Also, the oil cooler looks like a very small P-51 radiator, some meredith effect may have been generated there (note this is a significant difference between the La5 and the La7). The Soviet's had the opportunity to examine the P-51 in 1943 and 1944, and both the Yak and La designs seem to have borrowed the snorkle scoop from it, maybe some meredth effect technology was also borrowed.

Thirdly, the La7 cowl cooling inlet is in fact very narrow just like that of the Tempest II and P-47J. It is exactly what you are describing when you say "cut down on the cooling inlet". The combination of a large bullet spinner feeding into a small cowl inlet was definitely a part of the La7 cooling system design. Take a look at the attached image - just how much more do you think the cooling inlet can be cut down?

=S=

Lunatic

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## Anonymous (Mar 26, 2005)

pasoleati said:


> What are you babbling about "used" and "available" torque? Do you really understand what you write? Face this: if an engine is running at x rpm at full throttle, there is no "available" torque to accelerate anything unless the load is reduced!!! You are completely mixing part throttle and full throttle operation and inventing garbage like "available" torque.
> 
> Now, in ordinary car engines the power decreases relatively steadily as the rpm is decreased from the full power rpm down. On the other hand, torque curve starts rising with decreasing rpm (from that full power rpm) until it reaches the peak at a certain point that is highly variable with each engine. All this at FULL THROTTLE, i.e. CONSTANT MANIFOLD PRESSURE.
> In supercharged aero engines the curve is of different shape as it CANNOT BE OPERATED AT CONSTANT FULL POWER MAP EXCEPT AT HIGH RPM. Get it???



Available torque is a measurment taken at less than FULL THROTTLE. Go back through this debate and you will see that the issue is available power at less than FULL THROTTLE.

So why are you babbling about FULL POWER MAP? That was not the issue we were discussing. We were discussing the ability of the engine to power up to FULL THROTTLE AND MAP when running at a lower rpm/power level, or to sustain good power levels at lower than peak rpm. And for this, AVAILABLE TORQUE is the relevant measure of that ability. 

Don't you remember the point behind all this? It was that the Spitfire XIV had a higher need to maintain full RPM to sutain good power output because at less than full RPM its available torque curve drops off more sharply than that of a larger displacement engine (i.e. R-2800). Simply put, the cost in actual available power of droping RPM on the Griffon is more severe than the same % drop in RPM on the R-2800. Therefore, a smaller diameter 5 bladed prop was more beneficial to the Spitfire than it would have been to a P-47.

Get it?

=S=

Lunatic

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## Iskandar Taib (Mar 26, 2005)

RG_Lunatic said:


> First off, the Spitfire did not use any significant "Meredith Effect". Just because it's a liquid cooled engine radiator does not mean it exploits the effect. To achieve any significant Meredith effect, the system must include an expansion chamber prior to the radiator, a compression chamber after the radiator, and a thrust regulating exhaust nozzel. And finally, the exhaust flow must be directed into the vacuum wake of the fuselage to cancel out some or all of the parasitic drag. The Spitfire (and 109) lacked any of these features. Look in detail at the cooling system of the P-51 (as outlined in other threads on this forum) or the Mosquito to see examples of cooling systems which do significantly exploit this effect.



The Spitfire radiator was indeed designed to take advantage of the Meredith effect. See Quill's book. The Meredith effect was discovered in 1935, at the RAE, and Supermarine must have known about it. Just because the Mustang did it better does not mean others didn't use it. 



> Secondly, radial engines can exploit the effect, though I'm not sure exactly what the mechanism is. I know the Zero gained about 5-10 mph from the effect, and this part of the desing was stolen and transfered to the F4U Corsair for a gain of 10-15 mph. It may also have been exploited by the Soviets on the LA7 design. Also, the oil cooler looks like a very small P-51 radiator, some meredith effect may have been generated there (note this is a significant difference between the La5 and the La7).



Yes, they can definitely use it. Same principle. Heat from the engine is used to expand air and produce thrust. I'd be very surprised if everyone wasn't using it to some degree or another by 1944. If you didn't, and the effect is as large as people say it is, then your fighters are going to be pretty slow compared to everyone else's. 



> Thirdly, the La7 cowl cooling inlet is in fact very narrow just like that of the Tempest II and P-47J. It is exactly what you are describing when you say "cut down on the cooling inlet". The combination of a large bullet spinner feeding into a small cowl inlet was definitely a part of the La7 cooling system design. Take a look at the attached image - just how much more do you think the cooling inlet can be cut down?



Who knows.. It certainly isn't two inches like it is on the Reno heavy metal, though indeed it might be optimal and can't be reduced any further. The point is that it exists and is non-zero, and MUST be causing some drag. Probably a HUGE amount of drag. 

We don't know how much drag the cooling inlets caused on either airplane, and we don't know how much of this was offset by thrust recovered from the engine heat on either airplane. So why do people fault the Spitfire for the radiators and ignore the cooling inlet for the Lavochkin? Silly, isn't it?


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## Anonymous (Mar 26, 2005)

Who's ignoring the cooling inlet of the La7? The point is that it was very streamline. You cannot really argue the Spitfire was more streamlined because it didn't have a radial engine - by this point advanced cowl designs were very aerodynamic and did not cause much if any more drag than wing scoops.

If you actually investigate the F. H. Meridith document, you will see that it does not really describe a usable system. It is a series of equations showing that the effect should be possible, that's about it. The whole Lee Atwood argument that he brought this info over from England and it was used to create the P-51 radiator thrust system is highly dubious - it appears to be one of several attempts by Atwood to claim credit for the P-51 design that he doesn't really deserve. If his claims were legitimate he would not have waited until after Edgar Schmued died more than 40 years after the end of WWII to make them. Atwood was always jelous of Schmued's acclaim and also probably upset that "Dutch" Kindleberg gave Schmued the P-51 project instead of giving it to him. Clearly Kindleburg knew who had the right stuff. Lee Atwood's project - the B-25, showed nothing but conservativism of design - practically no innovation. The P-51 on the otherhand...

Here, read part of Ed Horkey's rebuttal to Lee Atwood's claim to have imported the "meridith effect" technology from Britian, a few years after Edgar Schmued passed away:



> Atwood's article brought a rebuttal from aerodynamicist Ed Horkey, who had come to North American from the California Institute of Technology in 1938 to work under Schmued. The aft location, he said, was an obvious choice; there was no room for a suitable radiator anywhere else. Neither he nor Irv Ashkenas, another Caltech-trained aerodynamicist who worked on the Mustang, remembers Lee Atwood having had a role in that decision. Horkey dismisses the algebra that Atwood used to explain the Meredith Effect to the lay reader with the words, "We used calculus." The British Purchasing Commission, Horkey thinks, was impressed less by the Meredith effect than by Dutch Kindelberger's magnetic personality and Ed Schmued's German accent.
> http://www.airspacemag.com/ASM/Mag/Index/1996/AS/wmtm.html



Again, w.r.t. the meridith effect, without the compression and expansion chamber and a pressure regulated exhaust nozzel, there simply cannot be much if any effect. The system is a heat pump in reverse, and lacking the above features, it is not going to produce much thrust. It's like comparing a pressure cooker to a open pot. And also, it does not vent the expanding air into the parasitic drag wake of the Spitfire, again minimizing the overall effect.

Just because a plane has radiators does not mean it had any meaningful thrust from the system. The fact is the Spitfire was not considered to produce hardly any Meridith effect. This can be seen by the fact the Spit IX is compared to the P-51 to estimate the effect, which is attributed about 350 HP equivalent for the P-51 over the Spit at full level speed (not accounting anything to the Spit for its lighter weight, lower Coef of Drag, and lower Mach number).

=S=

Lunatic


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## pasoleati (Mar 26, 2005)

Lunatic, you don´t have a single piece of evidence to support your theory that Griffon´s torque would drop faster that that of the R-2800. It was you who started babbling about car engines and their torque. In short, please provide PROOF (e.g. maker´s torque curves) on the R-2800 vs. Griffon affair.

And anyway, what does this have to do with propeller blade count. If you want greater diameter without increasing tip speeds, just change the reduction gear ratio. It would be insane to permanently reduce engine max rpm just to keep tip speed down. It would just indicate a bad design error.


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## Soren (Mar 26, 2005)

> As for manuver, the La7 was a very manuverable plane. It was considered much more manuverable than both the 190 and the 109. Roll rate was very good at all speeds up to about 400 mph. Turn rates were also excellent and energy retention in a turn was quite good. The La7 could exceute a 225 mph 360 degree turn at 1000 meters in under 20 seconds in either direction with no loss of speed.



See now your relying on fairytales again ! The La-7 Wasnt noticable more maneuverable than either the 190 or 109, and the Germans had 'no' problem shooting them down, and they did it in masses.



> The La-7 had one of the most streamline cowls of any radial engined fighter of WWII. It was more streamlined than any of the FW/TA designs, and comperable to the P-47J and Tempest II. It certainly had a little more nose drag than the Spitfire, but it had no wingscoop drag.



OMG are you trying to tell me that the Spitfires intakes induce more drag than the La-7's front nose section ?! The Air that hits the Spitfire's intakes will run almost straight through, while the air that hits the La-7's front nose section just smashes straight into it going virtually nowhere=Alot of drag !

The La-7's front nose section has bigger surface area than the two intakes under Spit's wings combined !



> The La-7 also had leading edge slats, I'd think you'd be in love with it Soren!



Sure, but the Spit XIV had a new and larger wing. As for the leading-edge-slats well, first of they were VERY small on the La-7, and the La-7 had alot of weight to carry around with those small wings. Its wing span was only 9,8m.

Lastly where did you get those wild Climb rate numbers from ?? The Russians never gave it such wild climb rate stats !


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## KraziKanuK (Mar 26, 2005)

> Sure, but the Spit XIV had a new and larger wing.



I did not know the Spit IX at 242sqft was smaller than the 242sqft of the Spit XIV.


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## Soren (Mar 26, 2005)

KraziKanuK said:


> > Sure, but the Spit XIV had a new and larger wing.
> 
> 
> 
> I did not know the Spit IX at 242sqft was smaller than the 242sqft of the Spit XIV.



Oh wasnt the Spit's wing larger than the La-7's maby ??  

Spit= 22.48 m2 vs La-7=17.5 m2.

I dont have the Root profile for the La-7's wing, but it wasnt thick thats for sure.


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## Iskandar Taib (Mar 26, 2005)

The Spit XIV started out as a Spit VIII. The Spit VIII was a Spit V with a two stage Merlin, some added tankage, tropicalized, a retractable tail wheel, and couple other refinements. The IX was basically a Mark V with a two stage Merlin in the nose, and was supposed to be a stop-gap measure. It ended up equipping most of Fighter Command's Spitfire squadrons while the more advanced Mark VIII was sent overseas (you hear about them in India and Burma, mostly). As far as I know, the wing was unchanged in all of these versions. 

The new wing came with the Mark XX.


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## Soren (Mar 26, 2005)

Iskandar Taib said:


> The new wing came with the Mark XX.



Don't you mean the XXI ?


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## Anonymous (Mar 26, 2005)

pasoleati said:


> Lunatic, you don´t have a single piece of evidence to support your theory that Griffon´s torque would drop faster that that of the R-2800. It was you who started babbling about car engines and their torque. In short, please provide PROOF (e.g. maker´s torque curves) on the R-2800 vs. Griffon affair.



If only I could. This info is not available.

Look, it's always true that, unless the larger engine is very poorly designed by comparision with he smaller one, that if they have equal peak HP that the larger engine will have a more favorable torque curve below peak power. That is a truism of engines within the size we are talking about (much bigger than about 5.5" diameter pistons starts becomming inefficient).



pasoleati said:


> And anyway, what does this have to do with propeller blade count. If you want greater diameter without increasing tip speeds, just change the reduction gear ratio. It would be insane to permanently reduce engine max rpm just to keep tip speed down. It would just indicate a bad design error.



Grrr....

Reducing prop RPM makes the thrust output less efficient. Even thicker blades are needed, which makes torque roll even more of a problem.

They don't "perminently reduce engine max. rpm", they reduce rpm at very high altitudes. This reduces the prop-tip speed at very high altitudes where that speed is approaching mach. It's a trade-off between more optimal performance in the expected combat altitude range vs. peak performance at very high altitude - where little actual combat occures. With the R2800, a reduction in RPM at high altitude means much less of a drop off in available torque, so if the plane tips its nose up it will not bog the engine so easily as it would a smaller engined plane running at similar reduced rpm.

=S=

Lunatic


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## Iskandar Taib (Mar 26, 2005)

Hmm.. You might be right. I could've sworn there was a Mark XX pictured in Quill's book, but I'll have to go get it out of storage. The Spitfire Society's web page shows no such Mark.


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## pasoleati (Mar 26, 2005)

So where is the source for this "truism"? It is interesting that of the numerous engine related books none has ever mentioned this "truism". Honestly speaking, your truism is simply illogical!

As for "reducing prop RPM makes the thrust output less efficient". Please prove this with primary sources. Again a purely illogical claim on your behalf. 

Perhaps we should ask Graham White, the leading authority on the R-2800, what he thinks about it. Be warned, he don´t suffer fools gladly.


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## Soren (Mar 26, 2005)

Iskandar Taib said:


> Hmm.. You might be right. I could've sworn there was a Mark XX pictured in Quill's book, but I'll have to go get it out of storage. The Spitfire Society's web page shows no such Mark.



Im sure it was the XXI, never heard the XX having it thats for sure.


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## Anonymous (Mar 26, 2005)

Soren said:


> > As for manuver, the La7 was a very manuverable plane. It was considered much more manuverable than both the 190 and the 109. Roll rate was very good at all speeds up to about 400 mph. Turn rates were also excellent and energy retention in a turn was quite good. The La7 could exceute a 225 mph 360 degree turn at 1000 meters in under 20 seconds in either direction with no loss of speed.
> 
> 
> 
> See now your relying on fairytales again ! The La-7 Wasnt noticable more maneuverable than either the 190 or 109, and the Germans had 'no' problem shooting them down, and they did it in masses.



Well, this is not what either the Russians or the Germans report.



Soren said:


> > The La-7 had one of the most streamline cowls of any radial engined fighter of WWII. It was more streamlined than any of the FW/TA designs, and comperable to the P-47J and Tempest II. It certainly had a little more nose drag than the Spitfire, but it had no wingscoop drag.
> 
> 
> 
> ...



Ahh but you are forgetting that the nose of the Spitfire is not drag free either. For the Spitfire, you have to add the nose drag plus the scoop drag to come up with a comparable figure for the La7's nose/cooling drag. And, I would bet that the inlet area on the La7 is significantly smaller than the scoop inlet area on the Spit XIV (remember, it's scoops were over-large to compensate for boundary layer injestion). Look for yourself - those Spit XIV scoops are HUGE!:






www.warbirdphotos.net





www.btinternet.com





Soren said:


> > The La-7 also had leading edge slats, I'd think you'd be in love with it Soren!
> 
> 
> 
> Sure, but the Spit XIV had a new and larger wing. As for the leading-edge-slats well, first of they were VERY small on the La-7, and the La-7 had alot of weight to carry around with those small wings. Its wing span was only 9,8m.



The wingslats on the La7 were a 35% of the length of the leading edge of the wing, as compared to about 45% for the Bf109 (with squared off wingtips, it'd probably be closer to equal for the round tiped 109 wings).

The La7-FN(V) had a wingloading of 37.7 lbs/sq-foot, as compared to the Spitfire XIV's wingloading of 35.7 lbs/sq-foot. Yes the Spit has a little advantage here, but it's not huge., a difference of only 5.6%. On the other hand, the Spitfire's 11.23 meter wingspan is 14.6% wider than that of the La7, a disadvantage for high speed manuver and for rolling.



Soren said:


> Lastly where did you get those wild Climb rate numbers from ?? The Russians never gave it such wild climb rate stats !



http://www.btinternet.com/~fulltilt/Perform.html

These are Russian test results, specifying the serial number of the actual planes tested.

=S=

Lunatic


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## Anonymous (Mar 26, 2005)

pasoleati said:


> So where is the source for this "truism"? It is interesting that of the numerous engine related books none has ever mentioned this "truism". Honestly speaking, your truism is simply illogical!



You must not have much engine experiance. I worked for a major engine analyser company for a year. More cubes = more avialable torque.



pasoleati said:


> As for "reducing prop RPM makes the thrust output less efficient". Please prove this with primary sources. Again a purely illogical claim on your behalf.



To give the same thrust at a lower rpm the blades have to be wider. Isn't that obvious?



pasoleati said:


> Perhaps we should ask Graham White, the leading authority on the R-2800, what he thinks about it. Be warned, he don´t suffer fools gladly.



Go right ahead. Ask him the question: "Why didn't the P-47 or F4U-4 use a 5 bladed prop like the Spit XIV?"

=S=

Lunatic


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## Soren (Mar 26, 2005)

> Well, this is not what either the Russians or the Germans report.



Your kidding me right ?! The La-5's and La-7's were shot down in masses, the 109 had a really good kill ratio against these two aircraft ! 

Leykauf said he never had problems with the Yak's or Lagg's, and found the Spitfire to be a MUCH tougher opponent ! (And that is what you'll hear from about every other 109 pilot) 

Also you will find that the Germans saw their 109 as a better T&B fighter !(Yeah thats right, and even some Russian La pilots claim the same)



> Ahh but you are forgetting that the nose of the Spitfire is not drag free either. For the Spitfire, you have to add the nose drag plus the scoop drag to come up with a comparable figure for the La7's nose/cooling drag. And, I would bet that the inlet area on the La7 is significantly smaller than the scoop inlet area on the Spit XIV (remember, it's scoops were over-large to compensate for boundary layer injestion). Look for yourself - those Spit XIV scoops are HUGE!:
> 
> 
> 
> ...



You couldnt find a more illustrative picture of the scoops, maby one where they not at thier largest !  

You see here's a better picture, and they are not HUGE:





Now thats is a HUGE nose:








> The wingslats on the La7 were a 35% of the length of the leading edge of the wing, as compared to about 45% for the Bf109 (with squared off wingtips, it'd probably be closer to equal for the round tiped 109 wings).



I'd say its more like 32-33%, but could be 35%. Still this is very small, and WW2 Russian fighters aint known for their mechanical reliability, so those slats would most most likely Jam alot !



> The La7-FN(V) had a wingloading of 37.7 lbs/sq-foot, as compared to the Spitfire XIV's wingloading of 35.7 lbs/sq-foot. Yes the Spit has a little advantage here, but it's not huge., a difference of only 5.6%. On the other hand, the Spitfire's 11.23 meter wingspan is 14.6% wider than that of the La7, a disadvantage for high speed manuver and for rolling.



Well its more a matter of lift-loading, and here IIRC the Spitfire is for once superior. The La-7's wings were thin !




> http://www.btinternet.com/~fulltilt/Perform.html
> 
> These are Russian test results, specifying the serial number of the actual planes tested.



These are Official 'Russian' specifications for the La-5FN and La-7:

*La-5FN:*
_Maximum speed: 648 km/h (405 mph) 
Range: 765 km (478 miles) 
Service ceiling: 11,000 m (36,080 ft) 
Rate of climb: 1,000 m/min (3,280 ft/min) _


*La-7*
_Maximum speed: 680 km/h (425 mph) 
Range: 990 km (618 miles) 
Service ceiling: 9,500 m (31,160 ft) 
Rate of climb: 1,100 m/min (3,608 ft/min) _

Source: "Lavochkin's Piston-Engined Fighters"


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## Anonymous (Mar 26, 2005)

Soren said:


> > Well, this is not what either the Russians or the Germans report.
> 
> 
> 
> ...



LOL - Lagg's.. he probably faced Lagg-3's, they were known as "wooden coffins".



Soren said:


> Also you will find that the Germans saw their 109 as a better T&B fighter !(Yeah thats right, and even some Russian La pilots claim the same)



Not that I've seen. I've watched lots of interviews and none say what you're saying. Lets see some of these claimed comments.



Soren said:


> > Ahh but you are forgetting that the nose of the Spitfire is not drag free either. For the Spitfire, you have to add the nose drag plus the scoop drag to come up with a comparable figure for the La7's nose/cooling drag. And, I would bet that the inlet area on the La7 is significantly smaller than the scoop inlet area on the Spit XIV (remember, it's scoops were over-large to compensate for boundary layer injestion). Look for yourself - those Spit XIV scoops are HUGE!:
> >
> >
> >
> ...



"at their largest" - ummm, they came in one size for the great majority of production.

You see here's a better picture, and they are not HUGE:





Look huge to me! 



Soren said:


> Now thats is a HUGE nose:



Your not being serious here. The inlet size is tiny by comparison. The nose appears huge only because the taper toward the rear is not visible, it's about the same as the Spitfire nose from a similar view. And this photo also obviously is distorted to make the nose look "fatter" than it really is because the camera is too close to the plane. The photo's I provided were of the two planes from very similar angles and distances. Be fair about your choice of images please.



Soren said:


> > The wingslats on the La7 were a 35% of the length of the leading edge of the wing, as compared to about 45% for the Bf109 (with squared off wingtips, it'd probably be closer to equal for the round tiped 109 wings).
> 
> 
> 
> I'd say its more like 32-33%, but could be 35%. Still this is very small, and WW2 Russian fighters aint known for their mechanical reliability, so those slats would most most likely Jam alot !



By the La7 they'd had pleanty of experiance with them and they probably didn't jam much more than the German slats.



Soren said:


> > The La7-FN(V) had a wingloading of 37.7 lbs/sq-foot, as compared to the Spitfire XIV's wingloading of 35.7 lbs/sq-foot. Yes the Spit has a little advantage here, but it's not huge., a difference of only 5.6%. On the other hand, the Spitfire's 11.23 meter wingspan is 14.6% wider than that of the La7, a disadvantage for high speed manuver and for rolling.
> 
> 
> 
> Well its more a matter of lift-loading, and here IIRC the Spitfire is for once superior. The La-7's wings were thin !



I don't think so, but I'd have to look up the NACA profiles to be sure.



Soren said:


> > http://www.btinternet.com/~fulltilt/Perform.html
> >
> > These are Russian test results, specifying the serial number of the actual planes tested.
> 
> ...



Well jeeze, so the Soviets use a more realistic method of specifying rate of climb than the most nations, which use initial rate of climb as the climb figure, which is totally misleading. The La7-FN(V) climbed to 6000 meters in 5.45 minutes, which is a climb rate of 3612 ft/min. The figure you've given is probably the 20,000 foot climb figure.

The P-51D had an initial rate of climb of 3,475 fpm, which would mean a 5.75 minute climb to 20,000 feet. Surely you are not suggesting this is a realistic assesment of the P-51D climb?

=S=

Lunatic


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## Soren (Mar 26, 2005)

> LOL - Lagg's.. he probably faced Lagg-3's,



Lagg's a La's look similar, also the Germans always refered to them as Lagg's.



> they were known as "wooden coffins".



By the Russians, yes.



> Not that I've seen. I've watched lots of interviews and none say what you're saying. Lets see some of these claimed comments.



Certainly !:

*Interview with Major Kozhemyako, who mostly flew the La-5:*

_"The Me109 was exceptional in turning combat. If there is a fighter plane built for turning combat , it has to be Messer! Speedy, maneuverable,(especially in vertical) and extremely dynamic."_

And there's more where that came from.



> "at their largest" - ummm, they came in one size for the great majority of production.



Look at the picture at the bottom of the page.



> Look huge to me!



Well it doesnt look HUGE to me.



> Your not being serious here. The inlet size is tiny by comparison.



The nose-inlet on the La-7 is 360* remember.  



> The nose appears huge only because the taper toward the rear is not visible, it's about the same as the Spitfire nose from a similar view. And this photo also obviously is distorted to make the nose look "fatter" than it really is because the camera is too close to the plane. The photo's I provided were of the two planes from very similar angles and distances.


 
 The picture of the Spitfire I presented is WAY closer than the picture I presented of the La-7 !  



> Be fair about your choice of images please.



And thats comming from you !!! Im not the one who presents a picture of a Spitfire with _white painted_ fully open Radiator's ! ( Yes that _does_ make'em look bigger ! )




> By the La7 they'd had pleanty of experiance with them and they probably didn't jam much more than the German slats.



Russian aircraft were very unreliable, also late war La's ! Mostly because of the Russian industry's culture of production was much inferior to that of
the Germans. Btw, the La-7 used alot of Wooden parts !  



> Well jeeze, so the Soviets use a more realistic method of specifying rate of climb than the most nations, which use initial rate of climb as the climb figure, which is totally misleading. The La7-FN(V) climbed to 6000 meters in 5.45 minutes, which is a climb rate of 3612 ft/min. The figure you've given is probably the 20,000 foot climb figure.
> 
> The P-51D had an initial rate of climb of 3,475 fpm, which would mean a 5.75 minute climb to 20,000 feet. Surely you are not suggesting this is a realistic assesment of the P-51D climb?



Were talking Max. Climb rate here RG !


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## Soren (Mar 26, 2005)

The Radiators aint at all HUGE:


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## the lancaster kicks ass (Mar 26, 2005)

great pics though.........


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## Soren (Mar 26, 2005)

Profiles:


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## Anonymous (Mar 26, 2005)

Soren said:


> > Your not being serious here. The inlet size is tiny by comparison.
> 
> 
> 
> The nose-inlet on the La-7 is 360* remember.



Sure, but even so the total inlet area is relatively small. You have to subract out the bullet spinner. There is perhaps a 3 inch gap between the bullet spinner and the cowl, probably less but without actual measurments it is hard to say. The Spit has two huge square radiator openings. It's like dragging 5 gallon buckets under each wing.



Soren said:


> > The nose appears huge only because the taper toward the rear is not visible, it's about the same as the Spitfire nose from a similar view. And this photo also obviously is distorted to make the nose look "fatter" than it really is because the camera is too close to the plane. The photo's I provided were of the two planes from very similar angles and distances.
> 
> 
> 
> The picture of the Spitfire I presented is WAY closer than the picture I presented of the La-7 !



I don't think so, I think both are a bit distorted, but the Picture of the La is more fish-eyed than the one of the Spit. The pictures I gave are from about the same angle and distance - and far enough away to avoid fish-eye.



Soren said:


> > Be fair about your choice of images please.
> 
> 
> 
> And thats comming from you !!! Im not the one who presents a picture of a Spitfire with _white painted_ fully open Radiator's ! ( Yes that _does_ make'em look bigger ! )



The color does not make them look bigger. The "fully open" does not matter, that's at the back. I assumed you'd only look at the opening in the front.



Soren said:


> > By the La7 they'd had pleanty of experiance with them and they probably didn't jam much more than the German slats.
> 
> 
> 
> ...



By the late model La7-FN(V), Soviet production quality was pretty darn good. These planes went to the aces of Stalin's Gaurd unit, every care was taken that they be of the highest quality.

Wood is not really that much of a disadvantage other than the increase in weight. In some respects it is more easily damaged, in others it is less easily damaged. Also, it tends not to trigger many types of ammo fuses, so HE and incendiary rounds may not go off. On the La-7, it was mostly wood, but the cowl was duraluminum, as were the leading edges of the wings and tail.



Soren said:


> > Well jeeze, so the Soviets use a more realistic method of specifying rate of climb than the most nations, which use initial rate of climb as the climb figure, which is totally misleading. The La7-FN(V) climbed to 6000 meters in 5.45 minutes, which is a climb rate of 3612 ft/min. The figure you've given is probably the 20,000 foot climb figure.
> >
> > The P-51D had an initial rate of climb of 3,475 fpm, which would mean a 5.75 minute climb to 20,000 feet. Surely you are not suggesting this is a realistic assesment of the P-51D climb?
> 
> ...



Maybe you are. I never go by initial climb rate, it's often deceptive. Time to altitude is the much more meaningful figure. Usually, time to 20,000 feet is the figure to be compared, but in some cases, time to another altitude is more relevant.

=S=

Lunatic

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## pasoleati (Mar 26, 2005)

RG_Lunatic said:


> You must not have much engine experiance. I worked for a major engine analyser company for a year. More cubes = more avialable torque.
> 
> Lunatic



So, are you claiming that a 5-litre engine developing 200 hp (P) at 4000 rpm has more torque (T in lbs.ft)) than a 2.5-litre engine developing 200 hp at 4000 rpm? Since

T=(P x 33,000)/(2 x Pi x RPM), how do you explain it? Remember, both develop the same power at same RPM.


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## Anonymous (Mar 27, 2005)

pasoleati said:


> RG_Lunatic said:
> 
> 
> > You must not have much engine experiance. I worked for a major engine analyser company for a year. More cubes = more avialable torque.
> ...



NOOOO! That is the actual HP/Torque output, or the work being done, and of course it is equal for an equal rpm.

I am claiming that at 2500 rpm the 5 liter will have more AVAILABLE torque than the 2.5 liter. I.e., it will be able to sustain 2500 rpms better under an increasing load, or it will be able to increase rpm more quickly under a load, than the 2.5 liter. So the 5 liter will handle a hill better (or in a plane a climb) than the 2.5 liter. In the smaller engine, it's more important to maintain peak power rpm (where available and used torque are synonomous) than it is for the larger engine.

=S=

Lunatic

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## Soren (Mar 27, 2005)

> I don't think so, I think both are a bit distorted, but the Picture of the La is more fish-eyed than the one of the Spit. The pictures I gave are from about the same angle and distance - and far enough away to avoid fish-eye.



Well the picture I presented of the Spitfire's Radiators was WAY closer, fish-eyed or not.



> The color does not make them look bigger.



It is well known that the color "white" makes things look bigger, especially when ist white and black stripes toghether, wich enlightens the white area and makes it look bigger. Im surprised you don't know that !



> The "fully open" does not matter, that's at the back. I assumed you'd only look at the opening in the front.



It doesnt matter because now i have given other pictures and profiles of the Spitfire where the Radiators look their right size.



> By the late model La7-FN(V), Soviet production quality was pretty darn good. These planes went to the aces of Stalin's Gaurd unit, every care was taken that they be of the highest quality.



Absolutely untrue ! Have you read the book " Lavochkin's Piston-Engined Fighters" ? If so, you will find that you are very wrong about your current assessment ! 



> Wood is not really that much of a disadvantage other than the increase in weight. In some respects it is more easily damaged, in others it is less easily damaged. Also, it tends not to trigger many types of ammo fuses, so HE and incendiary rounds may not go off. On the La-7, it was mostly wood, but the cowl was duraluminum, as were the leading edges of the wings and tail.



Hmm.. funny the Germans didnt complain that the La-7 was difficult to shoot down, rather that it caught flames quite easely after a few 20mm rounds.




> Maybe you are. I never go by initial climb rate, it's often deceptive. Time to altitude is the much more meaningful figure. Usually, time to 20,000 feet is the figure to be compared, but in some cases, time to another altitude is more relevant.



Well I was talking Max. Climb rate.


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## the lancaster kicks ass (Mar 27, 2005)

yeah but most fighters would go down after a few 20mm hits........


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## Anonymous (Mar 27, 2005)

Yep!


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## Soren (Mar 27, 2005)

the lancaster kicks ass said:


> yeah but most fighters would go down after a few 20mm hits........



Well it was easely shot down according to the Germans, and apparantly an easy target aswell as they had no problem hitting it with their 20mm Mk108 cannon.


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## Anonymous (Mar 27, 2005)

Soren said:


> the lancaster kicks ass said:
> 
> 
> > yeah but most fighters would go down after a few 20mm hits........
> ...



That's just silly. First off the MK108 is a 30mm cannon.

Secondly, the La7 was a highly manuverable plane. As I've said, it was considered more manuverable than either the 190's or 109's it faced. Multiple sources make this claim, and interviews with German pilots _who actually distinguish _between the Lagg-3 and the La5 and La7 support this.

=S=

Lunatic


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## Soren (Mar 27, 2005)

> First off the MK108 is a 30mm cannon.



Why do i always have a habbit of callling it the Mk108 !  "MG151/20" is what i meant obviously. 

Been talking about Me262 too much lately i guess. 



> Secondly, the La7 was a highly manuverable plane. As I've said, it was considered more manuverable than either the 190's or 109's it faced.



By who ? Not the Germans ! They shot it down without to much trouble. Sure it was maneuverable, but the 109 could easely hold its own against one. Most German aces started their carrieer in 43 where the La-5 had appeared, and steadily worked their way up.

Had the La's been superior they wouldnt have been shot down in the masses that they were. And had the 109 been inferior it wouldnt have given birth to as many German aswell as Finnish aces as it did.



> Multiple sources make this claim, and interviews with German pilots



Well then let us see them, I've already given alot of quotes. (Even from Russian fighter pilots.)




> who actually distinguish [/i]between the Lagg-3 and the La5 and La7 support this.



And as I've tried to tell you the Germans called both types Lagg's ! Only when getting real close could they distinguish them from each other.


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## Anonymous (Mar 27, 2005)

Soren said:


> > Secondly, the La7 was a highly manuverable plane. As I've said, it was considered more manuverable than either the 190's or 109's it faced.
> 
> 
> 
> ...



I suggest you goto the Luftwaffe' aces site and see just how few La5's and La7's were actually a part of the German Aces kills. It's amazing how many are Yak-1's and Lagg-3's, how few are Yak-3's, Yak-9's, La-5's, and La7's.



Soren said:


> > Multiple sources make this claim, and interviews with German pilots
> 
> 
> 
> Well then let us see them, I've already given alot of quotes. (Even from Russian fighter pilots.)



One Russian pilot, time period unkown. And your German quotes involve pilots who do not distinguish between a Lagg-3 and a La5 or La7.



> who actually distinguish [/i]between the Lagg-3 and the La5 and La7 support this.





Soren said:


> And as I've tried to tell you the Germans called both types Lagg's ! Only when getting real close could they distinguish them from each other.



What? The Lagg-3 was an inline engined fighter, the La5 and La7 had radials. Easy to tell the two types apart!

I'll try to dig up some pilot quotes soon. Most I've seen are in live interviews, but I'm sure I can find some on the web. I don't have time at the moment to do any searching - working on something else at the moment.

=S=

Lunatic


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## Soren (Mar 27, 2005)

> I suggest you goto the Luftwaffe' aces site and see just how few La5's and La7's were actually a part of the German Aces kills. It's amazing how many are Yak-1's and Lagg-3's, how few are Yak-3's, Yak-9's, La-5's, and La7's.



I've got the books, and yes its amazing how many "Lagg's" and "Lagg-"5"'s there has been shot down !  

Btw almost every Yak shot down was called a Yak-1, when ifact it was a Yak-3 or Yak-1B. 

You'll be amazed how many "Yak-1's" that were shot down in 44 !  Infact they were almost all Yak-3's.




> One Russian pilot, time period unkown.



Period: Do you remember the Kursk battle ?  And btw he was just talking about the 109 in general.



> And your German quotes involve pilots who do not distinguish between a Lagg-3 and a La5 or La7.



Yes they do, but they mostly called all La's "Lagg's, Lagg-5's". Late in the war they sometimes called them La-5's.



> What? The Lagg-3 was an inline engined fighter, the La5 and La7 had radials. Easy to tell the two types apart!



You'll find alot have been called either just "Lagg" or "Lagg-5". And the wing shape of the Lagg and La's are very similar, wich is why almost all La's were called Lagg's.

The La-7's were called either "Lagg's" or "La-5's" by the Germans, but this was the late war period, and therefore they were refered to more as La-5's.


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## Soren (Mar 27, 2005)

Alot of "Lagg-5's"  were noted as kills in the period of 44-45. Infact they were all La's, either La-5's or La-7's.

Also you will note that almost 'NO' La-5 shot down in 43- mid 44, was called "La-5", no they were called "Lagg-5's". 

The Germans called almost all La's "Lagg's", and thats a fact !


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## GermansRGeniuses (Mar 29, 2005)

Here are some simple notations I made...

Both have the same amount of "Drags," but you will find the majority of those on the LA-7 are less protuberant or large...


Though it is a radial-engined plane, the Lavochkin has a MUCH smoother fuselage...


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## the lancaster kicks ass (Mar 29, 2005)

nice little diagrams........


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## Soren (Mar 29, 2005)

You forgot that the is radial engined fighter, so it has a BIG 360 degree front nose section wich causes alot of drag !


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## the lancaster kicks ass (Mar 29, 2005)

this is true, however it caused allot less drag than a P-47 for example............


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## Anonymous (Mar 29, 2005)

Soren said:


> You forgot that the is radial engined fighter, so it has a BIG 360 degree front nose section wich causes alot of drag !



He did account that. This is counter balanced by the two huge wing scoops of the Spit 14, which caused a lot of drag!

Why do you think the nose inlet causes more drag than the wing scoops. All that matters is the inlet size. Clearly the Spit 14 has more cooling inlet area than the La7, and therefore more cooling system drag!

Drag from the wing scoops is also more detrimental to performance than drag from the nose inlet, which starts off being 20% reduced by the influence of the prop. The fan may further negate cowl inlet drag.

=S=

Lunatic


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## Soren (Mar 29, 2005)

RG_Lunatic said:


> Drag from the wing scoops is also more detrimental to performance than drag from the nose inlet, which starts off being 20% reduced by the influence of the prop. The fan may further negate cowl inlet drag.



20% less drag because of the prop ? lets hear how you figured that out...? 

It is very well known that radial engined aircraft have to deal with alot more drag than inline engined aircraft.


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## Anonymous (Mar 29, 2005)

Soren said:


> RG_Lunatic said:
> 
> 
> > Drag from the wing scoops is also more detrimental to performance than drag from the nose inlet, which starts off being 20% reduced by the influence of the prop. The fan may further negate cowl inlet drag.
> ...



Because the air is already slowed down 20% by passing through the prop. Also, the La7's cowl fan is going to reduce the drag effect of the air flowing into it, for a further reduction in drag.



Soren said:


> It is very well known that radial engined aircraft have to deal with alot more drag than inline engined aircraft.



Not really. This was the belief in the pre-war years, when the blunt nose of a radial was simply stuck into the wind. But during WWII advancements in cowl and spinner design showed that radial designs could be just as streamlined as liquid cooled designs. Look at all the fastest props of WWII - except for the P-51H (which has significantly improved radiator thrust over the B/D), they are all radial type designs. Even the TA-152 is, for all intents and purposes, a radial type design.

=S=

Lunatic


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## Soren (Mar 29, 2005)

> Because the air is already slowed down 20% by passing through the prop.



RG may I ask, how did you calculate that ??

Also wasnt the prop normally developed to 'cut' through the air, and 'accelerate' it backwards at an even faster rate =Thrust ?  

(Your in deep now RG, and your about to sink  )




> Not really. This was the belief in the pre-war years, when the blunt nose of a radial was simply stuck into the wind. But during WWII advancements in cowl and spinner design showed that radial designs could be just as streamlined as liquid cooled designs. Look at all the fastest props of WWII - except for the P-51H (which has significantly improved radiator thrust over the B/D), they are all radial type designs. Even the TA-152 is, for all intents and purposes, a radial type design.



Does this look like a Radial engine to you ?





Fw-190D-9 *liquid-cooled inline engine*.


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## wmaxt (Mar 29, 2005)

Soren said:


> > Because the air is already slowed down 20% by passing through the prop.
> 
> 
> 
> ...



Surprisingly it is propellar drag that limits Prop planes to subsonic speeds.

It was Luftwaffe practice to utilize Anular radiators to maintain the shape of an aircraft designed originaly for radial engines so they could go back if needed. It was also convienent because it limits plumbing and radiator modifications to a minimum. The Ju-88 was another example of this kind of thinking.


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## Soren (Mar 29, 2005)

wmaxt said:


> Surprisingly it is propellar drag that limits Prop planes to subsonic speeds.
> 
> .



Yes if you reach the max rpm for the engine (Depending on prop design), it will cause prop-drag, as then the propeller can't accelerate the air backwards no-more.


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## GermansRGeniuses (Mar 29, 2005)

RG_Lunatic said:


> Even the TA-152 is, for all intents and purposes, a radial type design.



He's not saying it HAS a radial, he's stating it basically is one, due to its annular radiator which gives it a radial shape.


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## wmaxt (Mar 29, 2005)

Soren said:


> wmaxt said:
> 
> 
> > Surprisingly it is propellar drag that limits Prop planes to subsonic speeds.
> ...



The limit is in the Propellar itself - ever wondered why all aircraft limiting RPM's are around 3,000rpm? When the tip of the prop exceeds the speed of sound it becomes a brake and produces no lift/thrust. Depending on diameter of the prop (the larger diameter of the prop the faster the tip speed is in relation to the RPM) that speed is around 3,000rpm.

A ducted fan helps in relation to the shock wave at the tip but is very cumbersome. The high bypass jet engine is an example of how the highspeed ducted fan can work.


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## Soren (Mar 29, 2005)

wmaxt said:


> The limit is in the Propellar itself - ever wondered why all aircraft limiting RPM's are around 3,000rpm? When the tip of the prop exceeds the speed of sound it becomes a brake and produces no lift/thrust. Depending on diameter of the prop (the larger diameter of the prop the faster the tip speed is in relation to the RPM) that speed is around 3,000rpm.
> 
> A ducted fan helps in relation to the shock wave at the tip but is very cumbersome. The high bypass jet engine is an example of how the highspeed ducted fan can work.



There's no disagreement on that.


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## Anonymous (Mar 29, 2005)

Soren said:


> > Because the air is already slowed down 20% by passing through the prop.
> 
> 
> 
> RG may I ask, how did you calculate that ??



I didn't calculate it. It comes from a study I read of the FW190 and Tempest cooling system. Part of the reason for the bullet spinner and the fan is to counter the 20% drop in airspeed caused by the prop.



Soren said:


> Also wasnt the prop normally developed to 'cut' through the air, and 'accelerate' it backwards at an even faster rate =Thrust ?



Not really. The purpose of the Prop is to cut into the air and pull the plane forward. The "thrust" is really just a byproduct. But also, props generally don't have much blade down that close to the spinner, and even if they did that'd be the least effective part of the prop since it is moving so much slower than the outer part. 



Soren said:


> (Your in deep now RG, and your about to sink  )



Not at all. You do your best to prove me wrong, and then I'll spend the time to locate the document describing the 20% loss of airflow through the prop. 8) 




> Not really. This was the belief in the pre-war years, when the blunt nose of a radial was simply stuck into the wind. But during WWII advancements in cowl and spinner design showed that radial designs could be just as streamlined as liquid cooled designs. Look at all the fastest props of WWII - except for the P-51H (which has significantly improved radiator thrust over the B/D), they are all radial type designs. Even the TA-152 is, for all intents and purposes, a radial type design.





Soren said:


> Does this look like a Radial engine to you ?
> 
> 
> 
> ...



So what, it is mounted such that it has all the negative drag characteristics of a radial engine, right? Or do you believe there is something magical about the liquid cooled engine that makes its cooling system not make drag?

=S=

Lunatic


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## Soren (Mar 29, 2005)

> Not really. The purpose of the Prop is to cut into the air and pull the plane forward. The "thrust" is really just a byproduct. But also, props generally don't have much blade down that close to the spinner, and even if they did that'd be the least effective part of the prop since it is moving so much slower than the outer part.



As Newton stated, "actio est reactio". For the propulsion problem, this means that a device accelerating air or water in one direction, feels a force in the opposite direction. A propeller accelerates incoming air particles, "throwing" them towards the rear of the airplane, and thus feels a force on itself - this force is called *thrust* ! 



> Not at all. You do your best to prove me wrong, and then I'll spend the time to locate the document describing the 20% loss of airflow through the prop. 8)



Go ahead, dispute what i just said above, if you can ! I am looking forward to seeing the "20% loss of air-resistance behind the prop" theory ! 



> So what, it is mounted such that it has all the negative drag characteristics of a radial engine, right? Or do you believe there is something magical about the liquid cooled engine that makes its cooling system not make drag?



Not at all, but the front nose section is MUCH smaller than that on the La-7, as a result of the Inline engine.


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## Anonymous (Mar 30, 2005)

Soren,

The blades create pulses of high speed turbulent air followed by periods of practically no airflow. Turbulent air is not good for cooling, requiring baffles, and of course no airflow = no cooling. Here are some sources:

http://www.geocities.com/donshoebridge/h-stab.html

http://www.ch601.org/resources/cooling_systems2.htm

http://www.bewersdorff.com/wankel/radiator/CoolingSystems1.html <== the definative source, is no longer online  

You can also read through various NACA reports (<-- click) on the subject. In particular look at page 377 of the http://naca.larc.nasa.gov/reports/1943/naca-report-771/ document, which conviently is available as a sample in .gif form:

http://naca.larc.nasa.gov/reports/1943/naca-report-771/index.cgi?page0007.gif

As you can see, in this experiment they were only able to recover about 75% of "free stream" airflow, though later improvements got as high as 80%. That leaves 20% loss.

This cooling loss was why the P-40 and Typhoon/Tempest V needed such huge chin scoops.

Anyway, the partial solution for radials (and the Dora/Ta) was the large bullet spinner, which accelerates the airflow into the cowl opening enough to overcome the loss of ~20% of cooling flow efficiency created by the prop, but over a much smaller inlet area. This provided sufficient cooling for climb and cruise conditions.

The problem with the large bullet spinner is that at high speeds it generates very high speed air into the cooling system, which is not good for cooling either - it becomes highly turblent on striking the cooling vanes and does not sustain long enough contact for good heat transfer. The best solution is to slow down the air entering the cooling system without creating turbulence or periods of no airflow - as far as I know only the P-51 and to a lesser degree the Mossie achieved this in WWII.

Also, if you look at them from the front, the La7's nose profile is not much if at all larger than the Spit XIV's.

=S=

Lunatic


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## Soren (Mar 31, 2005)

After reading all your sources, I still see nothing to back up your "20% loss of air-resistance behind the prop" theory !

The job of a propeller is to accelerate incoming air backwards=Increasing airflow. (The density of the air might be decreased, but thats another matter)

Also: 
_Propellers have also been called airscrew in the past, but this term may be misleading, because a propeller* does not move like a mechanical screw through a rigid medium.* You don't call a wing knife or slicer because it also does not slice through the air in the direction of its inclined mean line. Each section of a propeller (or of a wing) has a certain angle of incidence and is moving through the air at its unique angle of attack - both are independent. On the other hand, a mechanical screw or a knife moves through a rigid material exactly in the direction which is given by its pitch or angle of incidence - a screw with different pitches along its radius would get stuck, a propeller does not._

So thrust is *NOT* a by-product !

Thrust is what drives the airplane forward ! The planes propeller does not eat its way through air, like was it some kind of rigid structure. No a propeller accelerates incoming airflow/inflow backwards at an even higher rate creating *Thrust* wich drives the airplane forward.

There will be a point in high speed flight, where the propeller can't ceate thrust nomore, thus the prop acts more like a brake. 

For a typical, fixed pitch propeller, the largest induced velocity(Thrust) occurs under static conditions, where the efficiency is small. It decreases with increasing flight speed, until it reaches zero= no thrust is generated. When the flight speed is increased even more (e.g. by diving), the propeller acts like a windmill= it tries to turn the engine, which might be fatal for the engine. This is why piston-engined aircraft don't reach beyond subsonic speeds.


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## Anonymous (Mar 31, 2005)

Soren said:


> After reading all your sources, I still see nothing to back up your "20% loss of air-resistance behind the prop" theory !



Ummm... It's not my theory. I've read that figure when studying aircraft cooling systems 2 years ago. And if you don't see that in the NACA document then what can I say. It clearly shows that pressure drops by over 25% even with the best of the 4 cowls tested, as compared to "free-stream" airflow.

Did you not read the following:



> The Germans thought that if the radiator was moved to a point right up behind the propeller, that the cooling capacity of the radiator would increase and they could keep the engine cool. What they found is totally opposite. The radiator had to be moved farther away from the propeller, not closer. The reason this problem occurred in the first place is because each time that a propeller blade passed by the radiator, the radiator would see a pulse of high velocity air, but the dwell time between blades, where there was very little flow, negated the high velocity air flow.
> http://www.geocities.com/donshoebridge/h-stab.html





Soren said:


> The job of a propeller is to accelerate incoming air backwards=Increasing airflow. (The density of the air might be decreased, but thats another matter)



The density of the air is what matters when the air is measured by such a sensor, which is measuring an average. A higher air-flow would mean higher pressure reading. Less air molecules means less cooling.



Soren said:


> Also:
> _Propellers have also been called airscrew in the past, but this term may be misleading, because a propeller* does not move like a mechanical screw through a rigid medium.* You don't call a wing knife or slicer because it also does not slice through the air in the direction of its inclined mean line. Each section of a propeller (or of a wing) has a certain angle of incidence and is moving through the air at its unique angle of attack - both are independent. On the other hand, a mechanical screw or a knife moves through a rigid material exactly in the direction which is given by its pitch or angle of incidence - a screw with different pitches along its radius would get stuck, a propeller does not._
> 
> So thrust is *NOT* a by-product !
> ...



Let me be more clear. The explusion of air to the rear, which is what we normally call thrust, is not what drives the aircraft forward. That is the equal and opposit reaction to the prop pulling the plane forward through a gasous-liquid medium.

=S=

Lunatic


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## Soren (Mar 31, 2005)

RG we are talking "*Air-resistance*" Not "*Cooling properties*"

The Air-resistance is NOT decreased by 20% behind the prop, that is nonesense ! 

Here, read how a propeller works: http://www.grc.nasa.gov/WWW/K-12/airplane/propeller.html

Fact is a spinning propeller sets up a pressure lower than free stream in front of the propeller, and higher than free stream behind the propeller.

If NASA aint right, then who is ?


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## Anonymous (Mar 31, 2005)

Soren said:


> RG we are talking "*Air-resistance*" Not "*Cooling properties*"
> 
> The Air-resistance is NOT decreased by 20% behind the prop, that is nonesense !
> 
> ...



Stop being obtuse. We are not talking about the whole area behind the prop, we are talking about the small area of the prop in front of the cowling. At this point, most props don't even have much blade to them to drive air and they are moving at a slow rate compared to out by the tip. 

You are trying to compare the effect of the whole prop to the inner 6-12 inches. In that inner zone, the air resistance is reduced by the prop behind the prop. Of course, it is encounterd by the prop itself so it all balances out.

=S=

Lunatic


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## Soren (Mar 31, 2005)

Sure the inner part of the propeller doesnt spin as fast as the outer part, but it still sets up a pressure lower than free stream in front it, and higher than free stream behind it.

Also have a look at this Tropicalized Spitfire, it has an intake very close to the inner propeller, the same does the A6M "Zero".


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## the lancaster kicks ass (Mar 31, 2005)

great pic...................


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## delcyros (Mar 31, 2005)

cool pictures, indeed.
Hmm, I checked some books, too. 
First of, I found no proof that the La-7 was inferior compared to any Luftwaffe fighters. A few are even credited with Me-262 kills.
There is a difference between "german pilots did not feel inferior to soviet planes" and the fact that La-7 killed experienced Luftwaffe units (including ace units). And I think the La-7 kills are partly bouncings and partly because of the superior tactics of energy fighting (look at Hartmann). Very few Luftwaffe pilots tried to outmanouvre a soviet plane, in general it was even forbidden in the most common altitudes (esspecially against Yak-3 and later La-fighter).


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## Anonymous (Mar 31, 2005)

Soren said:


> Sure the inner part of the propeller doesnt spin as fast as the outer part, but it still sets up a pressure lower than free stream in front it, and higher than free stream behind it.



Well, think about your previous logic. At lower speeds the prop pulls the plane by creating a low pressure area in front of the prop and a high pressure area behind it. But the prop is not of uniform effect - the outer part of the prop moves more air than the inner part.

Let's consider a prop turning at 1000 rpm (makes the math easy).

At a point measured 1 foot off the axis of the prop, which for simplicity we will assume is entirely blocked by the spinner, the circumfrence of the sweep is 2 x Pie x 1 ft = 2 x 3.14 = 6.28 feet. At 1000 rpm this means the prop at that point is turning at 6280 fpm = 1.19 miles/min = 71 mph. Since _2 x Pi x r_ is a simple linear equation we can see that the speed at 2 feet is about 142 mph, at 3 feet it is 213 mph, at 4 feet it is 284 mph, and at 5 feet it is 355 mph.

Again to keep things simple, lets assume the spinner blocks off the inner most foot of the prop blade. Then lets divide up the props sweep into 1 foot thick curcles and assume the thrust for that region is the average of the inside and outside boarder speeds. Rather than bore you with the math, I've made the following diagram:






So by your own previous statement...



> There will be a point in high speed flight, where the propeller can't ceate thrust nomore, thus the prop acts more like a brake.
> 
> For a typical, fixed pitch propeller, the largest induced velocity(Thrust) occurs under static conditions, where the efficiency is small. It decreases with increasing flight speed, until it reaches zero= no thrust is generated. When the flight speed is increased even more (e.g. by diving), the propeller acts like a windmill= it tries to turn the engine, which might be fatal for the engine. This is why piston-engined aircraft don't reach beyond subsonic speeds.



... isn't it obvious that as the speed of the plane increases the thrust generated nearer the center of the prop will diminish to zero and then go negative, and that this phenomna will expand outwards along the prop from the root toward the tip as speed increases? Won't this create a low pressure area around the cowl, reducing both the effectiveness of cowl inlet cooling systems and reducing the drag of the aircraft cowling?



Soren said:


> Also have a look at this Tropicalized Spitfire, it has an intake very close to the inner propeller, the same does the A6M "Zero".



That's not a cooling intake, that's an air intake for the engine. Just bad design is all - it was an improvisation intended to resist injestion of dirt more than anything else. The loss of engine power from such a design was probably noticable but fairly minor. Also, they probably blamed the power loss on filters rather than the true cause. Lots of planes have the air intake up near the prop - it's a convienient place to put it.

=S=

Lunatic


----------



## wmaxt (Mar 31, 2005)

I've read that the loss was fairly significant and yes they did blame it on the filters.


----------



## Soren (Apr 1, 2005)

RG you can't just math it up like that, you've not even taken into considderation the inner prop design or how its formed ! 
The amount of thrust created is depending on the AoA of the prop blades, and as we all know those blades are twisted, so the thrust created is about the same on the inner prop as on the outer prop despite the speed difference. 

Each section of a propeller has a certain angle of incidence and is moving through the air at its unique angle of attack. The angle of attack of the airfoils at the tip is lower than at the hub because it is moving at a higher velocity than the hub. Also the lower airfoils at the hub are thicker, creating more lift/thrust pr revelution.





Also as the speed of the aircraft increases, different pitch settings can be made to gain more thrust at high speed. 
(The "Fixed pitch" propeller can't do this, but most WWII fighters inc. the La7 used the "Controllable Pitch" Propeller ) 

If it was as simple as you put it RG, then there would be planes flying in 1803 or even sooner !  

RG why don't you take a look at this: http://www.grc.nasa.gov/WWW/K-12/airplane/propth.html


----------



## Anonymous (Apr 1, 2005)

Soren said:


> RG you can't just math it up like that, you've not even taken into considderation the inner prop design or how its formed !
> The amount of thrust created is depending on the AoA of the prop blades, and as we all know those blades are twisted, so the thrust created is about the same on the inner prop as on the outer prop despite the speed difference.
> 
> Each section of a propeller has a certain angle of incidence and is moving through the air at its unique angle of attack. The angle of attack of the airfoils at the tip is lower than at the hub because it is moving at a higher velocity than the hub. Also the lower airfoils at the hub are thicker, creating more lift/thrust pr revelution.
> ...


----------



## Soren (Apr 1, 2005)

> I know this Soren, but it still does not change the overall effect. Yes the prop has some twist to it, but the difference in overall angle of attack is not enough to equal out the difference in speed.



Wrong. Look at the picture below, it illustrates the airflow trough the prop.



> Also, the inner part of the prop is of a somewhat laminar flow design, generating little or no airfoil lift - and it is thicker not to provide more lift, but rather for strength.
> 
> Look at your image - the inner two cross-sections have no lifting foil to them at all! And the inner 6 inches (assuming a 5' prop) or so is ROUND! 8)



No its not, I just presented a bad sketch then, heres a more illustrative one:






Btw if it was round, then it is quite common knowledge that airflow has no problem getting around a circular surface=Air pressure equal to "Free Airstream", but no thrust. 



> Also, if you're going to post a link, post one that goes somewhere meaningful, not just to the image you've arleady presented



I never posted that pic !  



> As for planes flying in 1803... no engines means no self powered planes - period.



Ever heard about the "bicycle", runs on the "Human" engine


----------



## Anonymous (Apr 1, 2005)

Soren said:


> > I know this Soren, but it still does not change the overall effect. Yes the prop has some twist to it, but the difference in overall angle of attack is not enough to equal out the difference in speed.
> 
> 
> 
> ...



This is a low-speed prop, like you might find on a cessna. Hardly relevant to this discussion.

Why don't you figure out the thrust difference for the angle of twist involved (and prop area, which is smaller for the inner part of the blade), and you will see that at high speed this part of the prop is not producing positive thrust.



Soren said:


> Btw if it was round, then we both know that air has no problem getting around a circular surface.



Say what? A round surface is an airfoil just like any other. It is really just a laminar airfoil with super extreme thickness. Of course the air has a hard time getting around it.



Soren said:


> > Also, if you're going to post a link, post one that goes somewhere meaningful, not just to the image you've arleady presented
> 
> 
> 
> I never posted that pic !



You changed the link, when I replied, it went to the .jpg you'd already posted. No problem, I've done that kind of thing myself.



Soren said:


> > As for planes flying in 1803... no engines means no self powered planes - period.
> 
> 
> 
> Ever heard about the "bicycle", runs on the "Human" engine



LOL - no plane built in the 1900's or earlier was going to run off of human power. It took spaceage materials and an extreme athelete to do it in the late 80's or early 90's.

=S=

Lunatic


----------



## Soren (Apr 1, 2005)

> This is a low-speed prop, like you might find on a cessna. Hardly relevant to this discussion.



Still the same shape ! This one just hasnt got the ability of controllable pitching, but the propeller airfoil is still the same shape.



> Why don't you figure out the thrust difference for the angle of twist involved (and prop area, which is smaller for the inner part of the blade), and you will see that at high speed this part of the prop is not producing positive thrust.



What do you think prop-pitching is for ??? 



> Say what? A round surface is an airfoil just like any other. It is really just a laminar airfoil with super extreme thickness. Of course the air has a hard time getting around it.



You don't get it... 



> LOL - no plane built in the 1900's or earlier was going to run off of human power. It took spaceage materials and an extreme athelete to do it in the late 80's or early 90's.



It didnt take space age equipment to help it fly, how then to you think a simple glider flies(By added speed to the wings offcourse, wich can be achieved by running !) Anyway my point was that the opportunity was there !


----------



## the lancaster kicks ass (Apr 1, 2005)

> It didnt take space age equipment to help it fly, how then to you think a simple glider flies(By added speed to the wings offcourse, wich can be achieved by running !)



running will aid take off however by gliding you're not using human power to stay airborn...........


----------



## Anonymous (Apr 1, 2005)

Soren said:


> > This is a low-speed prop, like you might find on a cessna. Hardly relevant to this discussion.
> 
> 
> 
> Still the same shape !



No they are not. The inner part of the prop design is different for high speed props. For low speed props, they maintain the shape further down because strength is not such an issue and production is easier.



Soren said:


> > Why don't you figure out the thrust difference for the angle of twist involved (and prop area, which is smaller for the inner part of the blade), and you will see that at high speed this part of the prop is not producing positive thrust.
> 
> 
> 
> What do you think prop-pitching is for ???



But at high speeds even at maximum pitch the inside of the prop cannot produce as much thust as the outside, even given the twist involved in the overall prop.



Soren said:


> > Say what? A round surface is an airfoil just like any other. It is really just a laminar airfoil with super extreme thickness. Of course the air has a hard time getting around it.
> 
> 
> 
> You don't get it...



Sure I do. You are claiming a round surface has no drag? Clearly bullet design proves this is WRONG.



Soren said:


> > LOL - no plane built in the 1900's or earlier was going to run off of human power. It took spaceage materials and an extreme athelete to do it in the late 80's or early 90's.
> 
> 
> 
> It didnt take space age equipment to help it fly, how then to you think a simple glider flies(By added speed to the wings offcourse, wich can be achieved by running !) Anyway my point was that the opportunity was there !



And simple gliders were flying back in the 1800's. Success was limited because the science of lift was lacking, and materials did not allow a light enough frame of sufficient strength for "hang" type gliders.

=S=

Lunatic


----------



## Soren (Apr 1, 2005)

> No they are not. The inner part of the prop design is different for high speed props. For low speed props, they maintain the shape further down because strength is not such an issue and production is easier.



Yes they are ! And a low speed prop also runs at the same max revolution-rate of about 3000rpm, so why should it be any less strong ?? (The centrifugal forces are the same !)

Proof at the bottom of the page...



> But at high speeds even at maximum pitch the inside of the prop cannot produce as much thust as the outside, even given the twist involved in the overall prop.



Proof please ! 

(About the circular surface; Im getting you a link.)



> And simple gliders were flying back in the 1800's. Success was limited because the science of lift was lacking, and materials did not allow a light enough frame of sufficient strength for "hang" type gliders.



I guess you don't know that it has been proved not so long ago, that even Leonardo da vinci's designs from the 17th century would have flown. (Yes it was tried in practice aswell, and it worked)


Anyway, look at this P-51's prop below:


----------



## Anonymous (Apr 2, 2005)

Soren said:


> > No they are not. The inner part of the prop design is different for high speed props. For low speed props, they maintain the shape further down because strength is not such an issue and production is easier.
> 
> 
> 
> Yes they are ! And a low speed prop also runs at the same max revolution-rate of about 3000rpm, so why should it be any less strong ?? (The centrifugal forces are the same !)



No, the props on typical private aircraft do not turn at anywhere near the typical ~1250-1500 rpm maximum of a fighter.



Soren said:


> Proof at the bottom of the page...



Umm, what is that supposed to prove. That's an H&S standard prop and does not have the same inner profile as used on radials like the LA7.

The prop becomes increasingly efficient the futher toward the tip, as long as it does not exceed mach, because it traveling faster and therefore further per rotation. Because of this, the pitch at maximum thrust is optimimized for the outer part of the blade, not the inner part of the blade, which is given more pitch to try to compensate. Because WE KNOW the outer part of the blade produces the most thrust, and because we know that at some speed the plane will ride the prop, we know that at some speed prior to this the inner part of the prop must stop generating postive thrust before the outer part.

The NACA document I already gave you shows that pressure for cooling is reduced by 25% compared to free-stream airflow, because of the prop.



> The best helix angle is as if the blade was a wing producing much more lift than drag, roughly 45° in practice. However due to the shape of the propeller only part of the blade can actually be operating at peak efficiency, the outer part of the blade produces the most thrust and so the blade is positioned at a pitch that gives optimum angle to that portion. Since a large portion of the blade is therefore at an inefficient angle the inboard ends of the blade are subsumed into a streamlined spinner to reduce the resistance torque that would otherwise be created.
> http://encyclopedia.lockergnome.com/s/b/Propeller#Aircraft_propellers



Now if the inner part of the prop is at an inefficent angle, they cannot produce as much thrust as the outer part. Right?

Or are you trying to say that the inner part of the prop produces as much thrust as the outer part?

=S=

Lunatic


----------



## Soren (Apr 2, 2005)

*sigh*

Well atleast we moved from "the air is already slowed down 20% by passing through the prop." to "the air is already slowed down 20% by going through the _inner_ part of the prop at _high speed_" Now we just need to leap over to the coclusion that the air _really _isnt slowed down at all.




> No, the props on typical private aircraft do not turn at anywhere near the typical ~1250-1500 rpm maximum of a fighter.



RG a single-piston-engined Cessna 210, has a Prop RPM of 2700  Most single-piston-engined Cessna's run at over 2500 in prop RPM.



> Umm, what is that supposed to prove. That's an H&S standard prop and does not have the same inner profile as used on radials like the LA7.



What do you think its supposed to prove ?! You said "High speed props" doesnt have airfoil-profile all the way down, but they DO, and I proved it to you ! 



> The prop becomes increasingly efficient the futher toward the tip, as long as it does not exceed mach, because it traveling faster and therefore further per rotation. Because of this, the pitch at maximum thrust is optimimized for the outer part of the blade, not the inner part of the blade, which is given more pitch to try to compensate. Because WE KNOW the outer part of the blade produces the most thrust, and because we know that at some speed the plane will ride the prop, we know that at some speed prior to this the inner part of the prop must stop generating postive thrust before the outer part.



*Sigh* 

Didnt you read ANYTHING at the NASA site ??!



> The NACA document I already gave you shows that pressure for cooling is reduced by 25% compared to free-stream airflow, because of the prop.



Listen here.. NACA documents are good for flight specification and aircraft specifications, but they are too bloody old for beeing of any real use when talking advanced aerodynamics ! (We have come a far way since those documents !)

Sure the base of the prop moves slower than the tip of the prop, but thats why the prop is twisted, and has a thicker airfoil shape at the base. As the speed increases the thrust decreases, but not from the base of the prop out to the tip, it gradually decreases on the whole span of the prop. At high speeds the fighters of WW2 had the opportunity of prop-pitching, wich greatly improved the the thrust of the propeller at high speed.

The most thrust is offcourse at the tip of the prop, but it isnt much. The whole point is that even at high speed, the inner part of the prop still sets up a pressure lower than free stream in front of it, and higher than free stream behind it. 




> > The best helix angle is as if the blade was a wing producing much more lift than drag, roughly 45° in practice. However due to the shape of the propeller only part of the blade can actually be operating at peak efficiency, the outer part of the blade produces the most thrust and so the blade is positioned at a pitch that gives optimum angle to that portion. Since a large portion of the blade is therefore at an inefficient angle the inboard ends of the blade are subsumed into a streamlined spinner to reduce the resistance torque that would otherwise be created.
> > http://encyclopedia.lockergnome.com/s/b/Propeller#Aircraft_propellers
> 
> 
> ...



From the NASA site:

_The blades are usually long and thin, and a cut through the blade perpendicular to the long dimension will give an airfoil shape. Because the blades rotate, the tip moves faster than the hub. So to make the propeller efficient, the blades are usually twisted. The angle of attack of the airfoils at the tip is lower than at the hub because it is moving at a higher velocity than the hub._

And incase you missed it the last time, here's a picture of the airflow behind a working propeller, from base to tip:


----------



## Anonymous (Apr 2, 2005)

Soren said:


> *sigh*
> 
> Well atleast we moved from "the air is already slowed down 20% by passing through the prop." to "the air is already slowed down 20% by going through the _inner_ part of the prop at _high speed_" Now we just need to leap over to the coclusion that the air _really _isnt slowed down at all.
> 
> ...



Okay, I'll take your word for it. But the props are no where near as large as WWII aircraft, which had to limit prop RPM to about 1600 rpm. Smaller props mean less stress, less torque, less vibration, and higher allowable tip speeds.



Soren said:


> > Umm, what is that supposed to prove. That's an H&S standard prop and does not have the same inner profile as used on radials like the LA7.
> 
> 
> 
> What do you think its supposed to prove ?! You said "High speed props" doesnt have airfoil-profile all the way down, but they DO, and I proved it to you !



No, the P-51 is an inline, and it uses the US HS prop. Look at the soviet props, the german props, and even many british props, they all have a smaller thicker shaft area near the base. US prop design was years ahead of the rest. And even on US radials, you see the same thing, or you see cuffs on the inner part of the prop to try to improve cooling.

But it really does not matter. Even with the airfoil, the lower speed and less than optimal angle of attack mean the inner portion of the prop will become inefficient when the outer portion of the prop is delivering peak thrust at high airspeed.



Soren said:


> Didnt you read ANYTHING at the NASA site ??!



Yes I read the whole thing. What there supports your position?



Soren said:


> > The NACA document I already gave you shows that pressure for cooling is reduced by 25% compared to free-stream airflow, because of the prop.
> 
> 
> 
> Listen here.. NACA documents are good for flight specification and aircraft specifications, but they are too bloody old for beeing of any real use when talking advanced aerodynamics ! (We have come a far way since those documents !)



We are talking about WWII designs. The NACA tests were valid then, and they are still valid now, unless proven mistaken, which in this case has not happened.



Soren said:


> Sure the base of the prop moves slower than the tip of the prop, but thats why the prop is twisted, and has a thicker airfoil shape at the base. As the speed increases the thrust decreases, but not from the base of the prop out to the tip, it gradually decreases on the whole span of the prop. At high speeds the fighters of WW2 had the opportunity of prop-pitching, wich greatly improved the the thrust of the propeller at high speed.



No, it has a thicker airfoil shape at the bottom mostly for strength. Peak thrust peformance is obtatined at about 45 degrees static, at speed, this rises to about 65 degrees. Minimum drag performance is achieved at angles greater than 45 degrees/65 degrees at speed. The typical WWII prop allows a max coarse pitch of about 65 degrees at 75% of the prop span, corresponding to about 80-85 degrees near the hub. Because the inner part cannot rotate fast enough to generate postive thrust, the concern becomes minimizing drag.



Soren said:


> The most thrust is offcourse at the tip of the prop, but it isnt much. The whole point is that even at high speed, the inner part of the prop still sets up a pressure lower than free stream in front of it, and higher than free stream behind it.



But the NACA documents and other sources I've given you clearly show that pressure at the cowl is below free-stream!

If the inner part of the prop were able to still make positive thrust, it means the outer part of the prop could make more thrust than it is and propell the plane faster. As long as increasing the pitch of the outer part of the prop will create more thrust than is lost at the inner part then it makes sense to do so.

You are saying that a mere 25 degree (maximum) increase in pitch and a doubling of chord is making up for more than 3x difference in speed. That's absurd. If this were the case, shorter thicker props with higher angles of attack would have been used.



Soren said:


> > > The best helix angle is as if the blade was a wing producing much more lift than drag, roughly 45° in practice. However due to the shape of the propeller only part of the blade can actually be operating at peak efficiency, the outer part of the blade produces the most thrust and so the blade is positioned at a pitch that gives optimum angle to that portion. Since a large portion of the blade is therefore at an inefficient angle the inboard ends of the blade are subsumed into a streamlined spinner to reduce the resistance torque that would otherwise be created.
> > > http://encyclopedia.lockergnome.com/s/b/Propeller#Aircraft_propellers
> >
> >
> ...



Making the prop "efficient" does not mean that it produces postive thrust along its whole span. This paragraph does not say what you imply it does.

=S=

Lunatic

PS: All this is mute - time and again in your ref'd sources they point out that during WWII it was proven that radial designs did not have inherantly more drag than inline designs. And that was the point you made that started this whole digression.


----------



## Soren (Apr 2, 2005)

> No, the P-51 is an inline, and it uses the US HS prop. Look at the soviet props, the german props, and even many british props, they all have a smaller thicker shaft area near the base.



Look at the bottom at the page, and you will see that you are very wrong.



> US prop design was years ahead of the rest.



Im seeing strong signs of Bias, cause thats just silly !



> But it really does not matter. Even with the airfoil, the lower speed and less than optimal angle of attack mean the inner portion of the prop will become inefficient when the outer portion of the prop is delivering peak thrust at high airspeed.



The tip of the propeller hardly creates more thrust than the lower part of the propeller, as its AoA is different.

Also we have yet to see any info on what prop design NACA's "Theory" is based on ! (Remember some props arent twisted !)



> What there supports your position?



Every last bit of it !



> We are talking about WWII designs. The NACA tests were valid then, and they are still valid now, unless proven mistaken, which in this case has not happened.



Well they HAVE been proven mistaken ! And as i said before, we don't even know what the propeller-design used in these tests were, it could just as well have been an untwisted prop as not.



> No, it has a thicker airfoil shape at the bottom mostly for strength.



*Sigh* No no no no...



> But the NACA documents and other sources I've given you clearly show that pressure at the cowl is below free-stream!



Propeller design ?



> If the inner part of the prop were able to still make positive thrust, it means the outer part of the prop could make more thrust than it is and propell the plane faster. As long as increasing the pitch of the outer part of the prop will create more thrust than is lost at the inner part then it makes sense to do so.



Ever heard of DRAG ? There is a certain point where the prop can't propell the plane forward because it has to deal with drag, and if the thrust isnt sufficient to counter this drag, then the plane won't move.



> You are saying that a mere 25 degree (maximum) increase in pitch and a doubling of chord is making up for more than 3x difference in speed. That's absurd. If this were the case, shorter thicker props with higher angles of attack would have been used.



And as you've seen the inner part of the prop is a thick short airfoil.




> PS: All this is mute - time and again in your ref'd sources they point out that during WWII it was proven that radial designs did not have inherantly more drag than inline designs. And that was the point you made that started this whole digression.



Show where that is stated 

You've got ot understand that the prop blades are shaped like a wing, and therefore, eventhough the inner part isnt spinning as fast, it still creates a low air-pressure infront of it and high air pressure behind it. It works just like a wing does, this is just in the vertical plane instead. And as I've proven to you the prop airfoil IS thicker at the base, thus creating more lift pr revolution.


----------



## the lancaster kicks ass (Apr 3, 2005)

i feel this conversation will long be remembered on the site asone of the all time greats, well done and kepp it up..........

great pics as well...........


----------



## Anonymous (Apr 3, 2005)

Soren said:


> > No, the P-51 is an inline, and it uses the US HS prop. Look at the soviet props, the german props, and even many british props, they all have a smaller thicker shaft area near the base.
> 
> 
> 
> Look at the bottom at the page, and you will see that you are very wrong.



LOL - you use a late model Spitfire as your example, one which has benefited from access to the NACA PRT research. Let's look at some relevant examples:


































Soren said:


> > US prop design was years ahead of the rest.
> 
> 
> 
> Im seeing strong signs of Bias, cause thats just silly !



No, it is a fact. The Germans (and the Soviets and even the Brits until very late in the war) all made several errors in prop design. The most significant was tapering of the trailing edge to an eliptical form, which robs thrust with no real benefit. Only the USA had the necessary research wind tunnels to truely optimize the props as was done in the NACA PRT research, which yeilded what are still the basis of optimized high-speed props today.

I'll reply to the rest of your argument soon. The math is interesting, but being the weekend I have miminal time for it and the associated graphics are quite an effort for me (learning a new paint program).

=S=

Lunatic


----------



## Soren (Apr 3, 2005)

Pic 2 and 6 clearly shows airfoil shape all the way down. And the Fw-190 has smaller fans behind the Prop, to create the extra pressure needed.



> LOL - you use a late model Spitfire as your example, one which has benefited from access to the NACA PRT research. Let's look at some relevant examples:



And why do you think I am ? your showing pictures of "Old" fighters, while were talking the late-war Spit XIV and LA-7 here !  

Have you ever seen a prop blade from a Spit XIV ? Airfoil all the way !!



> Only the USA had the necessary research wind tunnels



Thats a lie ! Germany made lots of wind-tunnel tests throughout the war, and if you'd read about Project-X then you would know this !

Germany werent lacking behind at all, if your using the Fw-190's prop as an example, then you should note the fans behind it !

Btw Britain had Wind-tunnel's aswell, and the Spit already had a fully airfoil shaped prop in late 41. (Pic below) 






The prop-airfoil is thicker at the base and pitched at a lower AoA, thus creating more lift, while the tip of the prop-airfoil is thin and pitched at a higher AoA, thus creating less lift. 




> but being the weekend I have miminal time for it and the associated graphics are quite an effort for me (learning a new paint program).



Don't use your own graphics RG, we need real aerodynamic research graphics from reliable sources, or else were gonna get nowhere.


----------



## Anonymous (Apr 3, 2005)

Soren,

Here are the problems with your "equal thrust through higher AOA and airfoil thickness" argument.

----------------------------------------------------

Let's consider two points on a prop, one at 5 feet and one at 2 feet from center, rotating at 1000 rpm. Therefore, as shown earlier, the rotational speed of the prop at the 5 foot mark is 355 mph, and at the 2 foot mark is 142 mph. Lets assume the maximum speed of the aircraft is about 355 mph and the pitch of the prop at 5' is 45 degrees.

Therefore, after accounting for the forward speed of the plane the airspeed across the prop airfoil at 5 feet is 505 mph, and at 2 feet it is 382 mph. So the air flows across the prop airfoil at 5 feet 31.4% faster than it does at 2 feet. In order for the airfoil at 2 feet to generate as much lift as the airfoil at 5 feet its upper surface will have to be 31.4% longer, as depicted below:






Clearly this is an absurd difference in chord, the 2 foot chord being impractically steep and producing far more drag than it would lift!

But there is another problem still...

Let's ignore the impracticallity of the chord thickness needed, and assume the 2 foot airfoil can generate as much lift at 382 mph as the 5 foot airfoil can at 505 mph. Lets further assume the drag at these relative speeds is equal (which they would not be).

Airfoils generate lift perpendicular to the airflow through which they pass, and drag in the same direction as the airflow. Using vectors I've depicted this in the diagram below, the 5' section shown on the left:





As is clearly shown, even making the above assumptions, the 2' airfoil point does not generate nearly the thrust made at the 5' airfoil point. And if you think the angle I've depicted for the 2' section is contrived to make it look bad, quite the reverse is true. While the 5' point angle is (obviously) 45 degrees, at the 2 foot point it would be over 79 degrees, which is steeper than that depicted.

The fact is the inner part of the prop cannot generate as much lift as the outer part, and no chord thickness is going to overcome this. At high speeds, the AOA is going to become extreme at the inner part of the prop, and very little of what lift is generated is going to result in usable thrust. Pressure will build in front of it (and thus diverge to the outside), and pressure behind the inner part of the prop will be less than the free stream airflow.

=S=

Lunatic


----------



## Anonymous (Apr 3, 2005)

Soren said:


> Pic 2 and 6 clearly shows airfoil shape all the way down. And the Fw-190 has smaller fans behind the Prop, to create the extra pressure needed.



You must be blind. The only "airfoil" shape at the root of these props is leftover from that above. What do you expect them to have done - made them square? Abruptly made them round? LOL



Soren said:


> > LOL - you use a late model Spitfire as your example, one which has benefited from access to the NACA PRT research. Let's look at some relevant examples:
> 
> 
> 
> And why do you think I am ? your showing pictures of "Old" fighters, while were talking the late-war Spit XIV and LA-7 here !



Well, we got a bit off topic to prop efficiency issues. But the point, except for the British and the USA, the airfoil characteristics near the root are relatively mimimal. But that does not really matter, as I've shown in my previous post, their is still a loss of pressure behind the inside of the prop rotation at high speed.



Soren said:


> Have you ever seen a prop blade from a Spit XIV ? Airfoil all the way !!



Sure, but that's because they were privy to the NACA PRT research.



Soren said:


> > Only the USA had the necessary research wind tunnels
> 
> 
> 
> Thats a lie ! Germany made lots of wind-tunnel tests throughout the war, and if you'd read about Project-X then you would know this !



You have not researched windtunnles much. If you do you will see that the NACA wind tunnels were far superior to those in the rest of the world. No one else had the 500 mph closed loop or +20 atmousphere windtunnels to do the this kind of research.



Soren said:


> Germany werent lacking behind at all, if your using the Fw-190's prop as an example, then you should note the fans behind it !



Sure, because they had to deal with the lack of cooling caused by the low pressure area immeadiately behind the prop.



Soren said:


> Btw Britain had Wind-tunnel's aswell, and the Spit already had a fully airfoil shaped prop in late 41. (Pic below)



They got full access to the NACA PRT research as it was happening in the very late 30's and early 40's. The Brit wind tunnels were insufficient for such research. They simply lacked millions of $ to spend on wind tunnels.



Soren said:


> The prop-airfoil is thicker at the base and pitched at a lower AoA, thus creating more lift, while the tip of the prop-airfoil is thin and pitched at a higher AoA, thus creating less lift.



That's pure poop.



Soren said:


> > but being the weekend I have miminal time for it and the associated graphics are quite an effort for me (learning a new paint program).
> 
> 
> 
> Don't use your own graphics RG, we need real aerodynamic research graphics from reliable sources, or else were gonna get nowhere.



My graphics simply superimpose multiple graphics from such sources to more clearly illistrate the point. If you like, I can reference the original sources.

=S=

Lunatic


----------



## Soren (Apr 4, 2005)

> You must be blind. The only "airfoil" shape at the root of these props is leftover from that above. What do you expect them to have done - made them square? Abruptly made them round? LOL



What are you talking about here ?



> Well, we got a bit off topic to prop efficiency issues. But the point, except for the British and the USA, the airfoil characteristics near the root are relatively mimimal. But that does not really matter, as I've shown in my previous post, their is still a loss of pressure behind the inside of the prop rotation at high speed.



Kind of funny how you changed it from "20% loss of airflow through the propeller" to "20 % loss of airflow through the _inner_ propeller at _high speeds_", whats next ?

Anyway Im gonna need reliable sources who specifically says that twisted pitchable props are not creating thrust near the hub at high speed.



> You have not researched windtunnles much. If you do you will see that the NACA wind tunnels were far superior to those in the rest of the world. No one else had the 500 mph closed loop or +20 atmousphere windtunnels to do the this kind of research.



Im going to need a very specific Source on that !! As in the department of aerodynamics, the Germans were ahead of the Allies ! 



> Sure, because they had to deal with the lack of cooling caused by the low pressure area immeadiately behind the prop.



And as you have seen(If you've ever been up close), they are all airfoil shaped thus creating the extra pressure. 



> They got full access to the NACA PRT research as it was happening in the very late 30's and early 40's. The Brit wind tunnels were insufficient for such research. They simply lacked millions of $ to spend on wind tunnels.



But thats not what you said ealier, no no.. "_Only the U.S. had those kind of props_" and "_The Germans (and the Soviets and even the Brits until very late in the war ) all made several errors in prop design._" !  



> That's pure poop.



 Your going to regret saying that !

Fact is, that a thinner airfoil that is at a high AoA will generate less lift than a thicker airfoil at a lower AoA. If your going to deny this aswell, then you really have no clue what your talking about !



> My graphics simply superimpose multiple graphics from such sources to more clearly illistrate the point. If you like, I can reference the original sources.



Sure, lets hear them.


----------



## Anonymous (Apr 4, 2005)

Soren said:


> > You must be blind. The only "airfoil" shape at the root of these props is leftover from that above. What do you expect them to have done - made them square? Abruptly made them round? LOL
> 
> 
> 
> What are you talking about here ?



Your claim that the airfoil of the prop is extended to the root on the photo's I provided.



Soren said:


> > Well, we got a bit off topic to prop efficiency issues. But the point, except for the British and the USA, the airfoil characteristics near the root are relatively mimimal. But that does not really matter, as I've shown in my previous post, their is still a loss of pressure behind the inside of the prop rotation at high speed.
> 
> 
> 
> Kind of funny how you changed it from "20% loss of airflow through the propeller" to "20 % loss of airflow through the _inner_ propeller at _high speeds_", whats next ?



When I said 20% loss through the prop, the context was clearly concerning the fuselage/nose section, not the whole of the prop. That'd be stupid - if the airflow behind the prop were 20% lower than the free-stream airflow across the whole prop, the plane would go backwards! We were talking about the nose of the plane and we were talking about high speeds.

Please don't try to put my statements in this conversation out of context.
Anyway Im gonna need reliable sources who specifically says that twisted pitchable props are not creating thrust near the hub at high speed.



Soren said:


> Anyway Im gonna need reliable sources who specifically says that twisted pitchable props are not creating thrust near the hub at high speed.



Where is your "reliable source" who specifically says they are?



Soren said:


> > You have not researched windtunnles much. If you do you will see that the NACA wind tunnels were far superior to those in the rest of the world. No one else had the 500 mph closed loop or +20 atmousphere windtunnels to do the this kind of research.
> 
> 
> 
> Im going to need a very specific Source on that !! As in the department of aerodynamics, the Germans were ahead of the Allies !



Ummm.. In about 1936 this was true. Then the US government allocated about $10 million for wind-tunnel construction and research projects, specifically in reaction to the German wind tunnel built I believe in 1935. You can find the sources for this easily - just research windtunnels, I suggest you start here:

http://www.hq.nasa.gov/office/pao/History/SP-440/contents.htm

And notice the following quote:



> [27] The resulting 8-foot high speed tunnel was unique, something no other country possessed. Since World War II was right around the corner, the tunnel had strategic value. The first tests, in fact, evaluated the effects of machine gun and cannon fire on the lift and drag properties of wing panels. This led logically to checking the effects of rivet heads, lapped joints, slots, and other irregularities on drag. Such tests demonstrated drag penalties as high as 40 percent over aerodynamically smooth wings. Aircraft manufacturers quickly switched to flush rivets and joints.
> http://www.hq.nasa.gov/office/pao/History/SP-440/ch3-5.htm





Soren said:


> > Sure, because they had to deal with the lack of cooling caused by the low pressure area immeadiately behind the prop.
> 
> 
> 
> And as you have seen(If you've ever been up close), they are all airfoil shaped thus creating the extra pressure.



As I've shown you, they don't. The inner part of the prop produces positive thrust at low airspeeds and (relatively) low angles of attack. This is good for climb. At high airspeeds, the inner part of the prop is just a necessary evil, and is turned sharply into the airstream to minimize drag and negative torque effects.



Soren said:


> > They got full access to the NACA PRT research as it was happening in the very late 30's and early 40's. The Brit wind tunnels were insufficient for such research. They simply lacked millions of $ to spend on wind tunnels.
> 
> 
> 
> But thats not what you said ealier, no no.. "_Only the U.S. had those kind of props_" and "_The Germans (and the Soviets and even the Brits until very late in the war ) all made several errors in prop design._" !



Even though the Brit's had access to the NACA wind tunnel data from the PRT, they still persisted in making the trailing edge of the prop somewhat eliptical in shape until very late in the war. This robs thrust for no appreciable benefit. No conflict here.



Soren said:


> > That's pure poop.
> 
> 
> 
> ...



To a degree yes, but you cannot push that to extremes, if you could, every wing would be hemispherical in shape. A thicker airfoil also creates more drag, and (in extreme cases) will encounter mach effects at a very low speed.

The pressure differential of an airfoil is calculated as the difference in air pressure above and below the wing. The air above the airfoil is at a lower pressure because it must travel further to reach the back of the airfoil than the airflow below the airfoil. As I have clearly shown, the required increase in thickness for the inner part of the prop airfoil to achieve the same "lift" as outer part is beyond reasonability. Look at the image I gave you!



> My graphics simply superimpose multiple graphics from such sources to more clearly illistrate the point. If you like, I can reference the original sources.



Sure, lets hear them.[/quote]

http://www.auf.asn.au/groundschool/propeller.html
http://www.geocities.com/donshoebridge/h-stab.html
http://www.hq.nasa.gov/office/pao/History/SP-445/ch4-1.htm
http://encyclopedia.lockergnome.com/s/b/Propeller#Aircraft_propellers
http://mesun4.wustl.edu/ccm/galscifi.html
http://www.grc.nasa.gov/WWW/K-12/airplane/propeller.html
http://www.allstar.fiu.edu/aero/Propulsion1.htm
http://home.att.net/~historyzone/Fisher.html

=S=

Lunatic


----------



## Soren (Apr 4, 2005)

> When I said 20% loss through the prop, the context was clearly concerning the fuselage/nose section, not the whole of the prop.



On the La-7 the fuselage covers alot of prop area RG !



> That'd be stupid - if the airflow behind the prop were 20% lower than the free-stream airflow across the whole prop, the plane would go backwards!



Thats right !



> We were talking about the nose of the plane and we were talking about high speeds.



We were NOT talking high speed ! And there is ansolutely NOTHING that implies we did.



> Where is your "reliable source" who specifically says they are?



You see im not the one who needs one, cause im not the one making claims !  

Anyhow I've provided many sites with pictures that illustrated the airflow through the intire prop-span. (And you just linked one of mine !  )




> Ummm.. In about 1936 this was true. Then the US government allocated about $10 million for wind-tunnel construction and research projects, specifically in reaction to the German wind tunnel built I believe in 1935. You can find the sources for this easily - just research windtunnels, I suggest you start here:



But you were suggesting that the Germans, British, and the Russains didnt build a Windtunnel research center ! And that fully airfoiled props werent used on German a/c's, wich is downright untrue ! (Proof below)





Also did the U.S. ever have jets in WW2 ? NO ! Or did they have something like this: (NO) 
http://www3.sympatico.ca/slavek.krepelka/gismos/fooger1.jpg

Face it, we were lacking compared to the Germans in that department !



> As I've shown you, they don't. The inner part of the prop produces positive thrust at low airspeeds and (relatively) low angles of attack. This is good for climb. At high airspeeds, the inner part of the prop is just a necessary evil, and is turned sharply into the airstream to minimize drag and negative torque effects.



Untrue, at high speed the inner part of the prop still creates higher than free-stream airflow behind it. 



> Even though the Brit's had access to the NACA wind tunnel data from the PRT, they still persisted in making the trailing edge of the prop somewhat eliptical in shape until very late in the war. This robs thrust for no appreciable benefit. No conflict here.



And an example would be good, show us a late war UK fighter with these inferior props.



> To a degree yes, but you cannot push that to extremes, if you could, every wing would be hemispherical in shape. A thicker airfoil also creates more drag, and (in extreme cases) will encounter mach effects at a very low speed.



Your example has nothing to do with what im talking about, your "Graphically Displayed" airfoil was only "thicker" than the thinner airfoil, but not wider ! 

You've got to understand the the tip of the prop isnt very wide, and that the base is both wider and thicker, thus creating much more lift than the thinner and shorter tip.



> The pressure differential of an airfoil is calculated as the difference in air pressure above and below the wing. The air above the airfoil is at a lower pressure because it must travel further to reach the back of the airfoil than the airflow below the airfoil. As I have clearly shown, the required increase in thickness for the inner part of the prop airfoil to achieve the same "lift" as outer part is beyond reasonability. Look at the image I gave you!



As I explained above your imaged is totally unrealistic, and the thicker airfoil shape you presented wasnt even wider than the tip airfoil next to it !!

At the bottom of the page is an accurate depiction of the difference between the tip of the prop airfoil, and the base of the prop airfoil. 




> http://www.auf.asn.au/groundschool/propeller.html
> http://www.geocities.com/donshoebridge/h-stab.html
> http://www.hq.nasa.gov/office/pao/History/SP-445/ch4-1.htm
> http://encyclopedia.lockergnome.com/s/b/Propeller#Aircraft_propellers
> ...



RG I provided the NASA site, and it doesnt agree even ONE bit with your claim ! And neither does any other source up there worth mentioning.

The German experiment only showed that when moving the Radiator up close to the prop, the airflow was too "Turbulent" to be any effective for "Cooling", but the airflow was still higher than free stream behind the prop.


----------



## Anonymous (Apr 5, 2005)

Soren said:


> > When I said 20% loss through the prop, the context was clearly concerning the fuselage/nose section, not the whole of the prop.
> 
> 
> 
> On the La-7 the fuselage covers alot of prop area RG !



Compared to other radial designs, the La7 has one of the slimest nose/cowl contours of any WWII plane.



Soren said:


> > We were talking about the nose of the plane and we were talking about high speeds.
> 
> 
> 
> We were NOT talking high speed ! And there is ansolutely NOTHING that implies we did.



Of course we were. We were talking about drag from the nose - drag grows exponentially with speed, so it is not much of an issue at anything but high speed!



Soren said:


> > Where is your "reliable source" who specifically says they are?
> 
> 
> 
> You see im not the one who needs one, cause im not the one making claims !



That's pure BS. I've given you sources showing a 20-25% loss in pressure behind the prop feeding into the cowling. Your assertion is that this was not due to the prop - you have to prove this.



Soren said:


> Anyhow I've provided many sites with pictures that illustrated the airflow through the intire prop-span. (And you just linked one of mine !  )



And not one of "your" sources (as if you own them! ) shows the pressure differences within the thrust stream of the prop, they treat the whole of the prop as a single vector for simplicity. If you look at the sites I gave you, you can see on the one with the math plots that the pressure is not at all uniform.




Soren said:


> > Ummm.. In about 1936 this was true. Then the US government allocated about $10 million for wind-tunnel construction and research projects, specifically in reaction to the German wind tunnel built I believe in 1935. You can find the sources for this easily - just research windtunnels, I suggest you start here:
> 
> 
> 
> But you were suggesting that the Germans, British, and the Russains didnt build a Windtunnel research center ! And that fully airfoiled props werent used on German a/c's, wich is downright untrue ! (Proof below)



They had lots of examples of correct prop designs to examine. But it was hit-or miss. Look at the photos below. Some of the German airfoils were better than others, but reguardless they were never even as good as the Brit prop designs. They still used an eliptical leading and trailing edges on almost all their props.

None of the other countries in WWII had wind-tunnels capable of doing high speed prop reasearch of any significance. To do so you need a full scale 500 mph tunnel, and you also need a high-pressure tunnel so you can study the aerodynamic issues at reduced scale and speed. The 20 atmosphere tunnel allowed 1/20th scale tests at 1/20th the speed. No one else had tunnels like these.



Soren said:


> Also did the U.S. ever have jets in WW2 ? NO ! Or did they have something like this: (NO)
> 
> Face it, we were lacking compared to the Germans in that department !



The USA was about winning a war - not making industrialists rich and political/military leaders rich off the kickbacks. As I've said many times before - the German jet program hurt them in WWII, it did not help them. Look at the huge investment in both materials and manpower to construct ~2500 Me262 frames, ~1600 completed airframes, only to field something around 300 combat aircraft in a project that lasted 4 years.

Besides, by the end of WWII the USA had pretty much caught up with the Germans in the jet department. Given another year, the USA would have had the lead. And unlike German, the USA could build what it designed.



Soren said:


> > As I've shown you, they don't. The inner part of the prop produces positive thrust at low airspeeds and (relatively) low angles of attack. This is good for climb. At high airspeeds, the inner part of the prop is just a necessary evil, and is turned sharply into the airstream to minimize drag and negative torque effects.
> 
> 
> 
> Untrue, at high speed the inner part of the prop still creates higher than free-stream airflow behind it.



No it does not! I've shown you why it doesn't, explain how I'm wrong.



Soren said:


> > Even though the Brit's had access to the NACA wind tunnel data from the PRT, they still persisted in making the trailing edge of the prop somewhat eliptical in shape until very late in the war. This robs thrust for no appreciable benefit. No conflict here.
> 
> 
> 
> And an example would be good, show us a late war UK fighter with these inferior props.



I already have. They have elipitical forms, especially along the trailing edge. This is ineffecient. Take a look at these photos:






This is an efficient prop design derived from the PRT program. Notice it does not have an elpitical form on either the leading or trailing edge.






Notice the elipitical form, especially on the trailing edge. This is inefficient.






Notice on this FW190D-13 the elipitical form on both the front and trailing edge where it is particularly pronounced! This is even less efficient.






Here's a view of a collectors FW190A-9 prop section. Horribly inefficient.



Soren said:


> > To a degree yes, but you cannot push that to extremes, if you could, every wing would be hemispherical in shape. A thicker airfoil also creates more drag, and (in extreme cases) will encounter mach effects at a very low speed.
> 
> 
> 
> ...



Only on an inefficient prop design is this true, as shown above. And in most such cases where the prop does narrow out toward the tip, the prop is still at its widest at the mid point and narrows from there to the hub, though admittedly only sligthly on the later model Spitfires.

So by this logic, the outer part of the prop should be made inefficient and give up some of the thrust it could otherwise make so that the inner part of the prop can generate positive thrust? That's ludicrous!



Soren said:


> > The pressure differential of an airfoil is calculated as the difference in air pressure above and below the wing. The air above the airfoil is at a lower pressure because it must travel further to reach the back of the airfoil than the airflow below the airfoil. As I have clearly shown, the required increase in thickness for the inner part of the prop airfoil to achieve the same "lift" as outer part is beyond reasonability. Look at the image I gave you!
> 
> 
> 
> As I explained above your imaged is totally unrealistic, and the thicker airfoil shape you presented wasnt even wider than the tip airfoil next to it !!



Ummm... I did not show a "tip airfoil", I showed a segment taken at 5' from center. As you can see on the P-51D above, at the 5 foot mark on the over 6 foot long prop blade the airfoil is actually wider than it is down at the 2 foot mark. Only inefficient prop designs get narrower as they proceed from the mid-point to the tip.



Soren said:


> At the bottom of the page is an accurate depiction of the difference between the tip of the prop airfoil, and the base of the prop airfoil.



LOL - yes, for an inherantly badly designed prop! That prop is horribly innefficient. And even so, section A of your diagram about the same width as section G!

=S=

Lunatic


----------



## Soren (Apr 5, 2005)

*Sigh* Man im getting tired of this...

Anyway by the end of this week I will send a E-mail to Tom Benson, a NASA areodynamic researcher, so we will have our answer soon.

My whole point is that the inner prop still generates thrust at high speed.

Anyway lets look at your starting arguement....

You started this arguement by saying that the big front nose section on the LA-7 didnt matter, because 20% of the airflow will be lost through the prop(Because according to you, the blades arent airfoiled all the way). Ok fine.. but how does this support your claim that the La-7 was more aerodynamicly clean than the Spit XIV ? 
If there is 20% loss of drag behind the La-7's prop, then that 20% drag just sits on the prop instead = Zero loss of drag !

The Spit XIV had fully airfoiled prop-blades, meaning no inner prop drag, but higher than free-stream pressure behind the inner prop.


----------



## Anonymous (Apr 5, 2005)

Soren said:


> *Sigh* Man im getting tired of this...
> 
> Anyway by the end of this week I will send a E-mail to Tom Benson, a NASA areodynamic researcher, so we will have our answer soon.
> 
> ...



Because the same 20% sits on the Spit prop, so the drag of a well designed radial cowling is only mimimally higher than that of an inline. By the time you factor in the added drag from the radiators, the inline has no real advantage at all. The only exception is if the cooling system can generate thrust like on the P-51, to cancel out the drag the radiators create.



Soren said:


> The Spit XIV had fully airfoiled prop-blades, meaning no inner prop drag, but higher than free-stream pressure behind the inner prop.



Just because they are airfoils all the way down does not mean there is no drag. There is always drag for any object moving through air. The thicker the airfoil section and steeper its frontal incline, the higher the drag.

And again, I've clearly shown why at the inside of the prop at high speed there is a pressure loss behind the prop. As soon as the thrust vector is exeeded by the drag vector's projection along the thrust line, this is always going to be the case.

=S=

Lunatic


----------



## Soren (Apr 5, 2005)

RG_Lunatic said:


> Just because they are airfoils all the way down does not mean there is no drag. There is always drag for any object moving through air. The thicker the airfoil section and steeper its frontal incline, the higher the drag.



RG the blade has "Airfoil" shape, wich means that when the blade rotates the blade creates high pressure behind it, and low pressure infront of it !

Like a wing, wich when moving through the air creates low pressure above itself and high pressure below itself = Lift


----------



## Anonymous (Apr 5, 2005)

Soren said:


> RG_Lunatic said:
> 
> 
> > Just because they are airfoils all the way down does not mean there is no drag. There is always drag for any object moving through air. The thicker the airfoil section and steeper its frontal incline, the higher the drag.
> ...



No, the airfoil of the prop creates lift just like a wing, meaing that it is perpendicular to the lower surface of the airfoil, which depends on it's orientation. If it is pitched 60 degrees from the rotational axis, the "lift" will be at -30 degrees to the rotational axis. The drag will be at -120 degrees to the rotational axis. There is no gaurantee that the component of the lift vector at 90 degrees to the rotational axis (i.e. "forward") will exceed the compoent of the drag vector at -90 degrees to the rotational axis. Once the angle of attack exceeds 45 degrees, the drag effect is excentuated, and the lift effect is diminished. And drag of an airfoil increases with thickness faster than lift does.

=S=

Lunatic


----------



## Soren (Apr 6, 2005)

RG there is absolutely nothing above of wich i said that is untrue !


----------



## Anonymous (Apr 6, 2005)

Then you can clearly see that the inner part of the prop may not produce positive thrust at high speeds right?

 

Lunatic


----------



## Soren (Apr 6, 2005)




----------



## the lancaster kicks ass (Apr 7, 2005)




----------



## GregP (Jun 5, 2006)

Let's look at some specifics:

Supermarine Spitfire XIV
Empty Weight: 2994 kg. Loaded weight: 3856 kg. Wing Loading: 171.5 kg/m2. Power: 1529 kW. Power Loading: 2.5 kg/kW. Effective Aspect Ratio: 5.6. Ceiling: 13560 m.

Lavochkin La-7
Empty Weight: 2638 kg. Loaded Weight: 3280 kg. Wing Loading: .186.5 kg/m2 Power: 1380 kW.Power Loading: 2.4 kg/kW. Effective Aspect Ratio: 5.5. Ceiling: 10750 m.

Focke-Wulf Fw-190A3
Empty Weight: 3200 kg. Loaded Weight: 3893 kg. Wing Loading: 212.7 kg/m2. Power: 1268 kW. Power Loading: 3.1 kg/kW. Effective Aspect Ratio: 6.0. Ceiling: 11300 m.


The best wing loading and ceiling go to the Spitfire XIV, meaning probably a tighter turn radius, but the XIV does not beat the La-7 by much. The 190A3 is 15% worse.

Power loading goes to the La-7, meaning best acceleration. The XIV has a better rate of climb at all altitudes, but not by too much. The Fw-190A3 outclimbs the La-7 above 17,000 feet or so, but we knew the La-7 wasn’t a high-altitude type anyway.

Best aspect ratio is about a wash between the XIV and La-9, meaning that at altitude (OK, a lower altitude for the La-7), they were very close in weight-lifting capability.

All in all, there is no roll data above, but it can be found. The Fw-190 is better than either the XIV or the La-7 until 450 mph, at which time the La-7 is better. The La-7 is better than the XIV in roll at all speeds above 280 mph or so (sorry the graph is in mph). See: http://kingcat.hihome.com/rollrate.html.

So I can say that the Spitfire or the La-7 were better dogfighters than the Fw-190A3 except in roll rate. In armament, the Fw was probably near the top.

Tough choice. I’d take any of them with the best pilot in the cockpit.


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## Jank (Jun 5, 2006)

Greg, I wouldn't put much faith in that computer program concerning roll rates if I were you. You know, garbage in - garbage out.

Pilots who flew both the P-51 and P-47 remarked that the P-47's roll rate was noticeably superior to the P-51. That program puts them at about equal.

It also puts the F4U-1 roll rate superior to the P-47. That wasn't the case.


----------



## wmaxt (Jun 6, 2006)

Jank said:


> Greg, I wouldn't put much faith in that computer program concerning roll rates if I were you. You know, garbage in - garbage out.
> 
> Pilots who flew both the P-51 and P-47 remarked that the P-47's roll rate was noticeably superior to the P-51. That program puts them at about equal.
> 
> It also puts the F4U-1 roll rate superior to the P-47. That wasn't the case.



If they got the F4U prototype roll rate specs it might have been faster than the P-47. The F4U-1 had a slower roll rate than the prototype.

wmaxt


----------



## PipsPriller (Jun 8, 2006)

As good as the La.7 was, I would have to go with the Spitfire Mk.XIV. The Griffon engined Spitfires were simply far superior to all piston engined aircraft - bar perhaps the Ta.152. And even the Ta's advantages were slight.

But against the La.7 the Mk. XIV enjoyed decided advantages in speed, acceleration, climb, quality of production and fire power (see http://www.quarry.nildram.co.uk/WW2guneffect.htm for excellent details of relative fire powere merits) and was at least equal if not superior in turn and dive.

The only clear advantage of the La.7 would be a slightly superior roll rate.


----------



## PipsPriller (Jun 8, 2006)

Jank said:


> Pilots who flew both the P-51 and P-47 remarked that the P-47's roll rate was noticeably superior to the P-51. That program puts them at about equal.
> 
> It also puts the F4U-1 roll rate superior to the P-47. That wasn't the case.



At the Joint Fighter Conference, Naval Air Station Patuxent, held in Cotober 1944, a large group of combat and test pilots evaluated certain characteristics of all America's front line fighters. The finding were ranked by a number of categories (24 in total).

The aircraft rated with the fastest roll rate was the F4U-1a; followed by the P-51D and P-38L, with the P-47D fourth.


----------



## Jank (Jun 8, 2006)

Pips, I have read the Report of Joint Fighter Conference, NAS Patuxent River, MD 16-23 Oct. 1944. In fact, it is sitting three inches from my right elbow as I write this.

*Nowhere does it say that.* If you disagree, please cite the page for me.

The only place such rankings would be found is in the "Summary of Questionnaires" section where, for instance, the P-47 was considered the "Best fighter above 25,000ft" over the P-51, F4U-1, F6F, F4U-4, Seafire and P-38 in that order of preference. As for below 25,000ft, the P-47 didn't even register in the pecking order. (hardly a surprise) 

On a semi-related note, another myth concerning this particular publication is that in it, the USAAF admitted that the Corsair is more rugged than the Thunderbolt. Again, nowhere does it say that.


----------



## wmaxt (Jun 8, 2006)

Jank said:


> Pips, I have read the Report of Joint Fighter Conference, NAS Patuxent River, MD 16-23 Oct. 1944. In fact, it is sitting three inches from my right elbow as I write this.
> 
> *Nowhere does it say that.* If you disagree, please cite the page for me.
> 
> ...



From other sources show Roll rates as follows

Plane -- 250mph --- 350mph --- 400mph 

P-47D - 83deg 
P-47N - 102deg
P-51B - 81deg ---- 85deg ------ 80deg
P-38L - 71deg ---- 92deg ------ 95deg
Spit 47 ------------------------70deg
Fw-190A 125deg - 81deg ------- 70deg

Its my understanding that the F4U production aircraft had their roll rates reduced to approximately those of the P-51 because the prototype "rolled to fast". In that era roll rates were tailored for a specific "Feel" esp in the landing pattern where high roll rates were considered dangerous. I'm not sure I understand this because at the time the P-40s/P-51s/P-47s not to mention the Corsair had severe torque issues when on the ground and the Corsair even in landing situations. I picked this up in a book I no longer have about the development of the Corsair. 

There are a lot of P-38 pilots who flew all three (P-38, P-47, P-51) that would dispute those findings.

wmaxt


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## Soren (Jun 8, 2006)

The Fw-190A would roll 360 degree's in 2 sec = 180 deg/sec.


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## Jabberwocky (Jun 9, 2006)

The best figure I've seen quoted for the Fw-190 from any sort of testing is 171 deg/sec. Average seems to be about 155 in most tests.

The best thing about the FW-190 was that the alieron control was done with solid bars, not wires, so the aircraft wouldn't get 'sloppy' in the rolling plane with use like many others of its era. Spitfires used to have huge variations in roll rates if the control cables weren't properly adjusted.

Incorrect adjustments of the FW-190s alierons could have a dramatic effect on roll rate though. Hence you get some screw tesing results, like the USN test of the FW-190A5 which has the Corsair outrolling the Wurger, something that wouldn't be possible with a properly maintained FW-190.


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## Soren (Jun 9, 2006)

Jabberwocky said:


> Incorrect adjustments of the FW-190s alierons could have a dramatic effect on roll rate though. Hence you get some screw tesing results, like the USN test of the FW-190A5 which has the Corsair outrolling the Wurger, something that wouldn't be possible with a properly maintained FW-190.



The improper adjustment of the FW190's ailerons affected mostly the turn rate, causing premature stalling in turns.


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## Jabberwocky (Jun 9, 2006)

It could also cut roll rate by more than 40%. The USN tests had a maximum rate of roll of abour 90 degrees a second. British tests with the same machine maxed out at around 160 degrees a second.

There was a bit of too'ing and fro'ing between the USN and the RAE about FW-190 roll rates, i'll see if I can dig up the sources.


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## Twitch (Jun 9, 2006)

As I see there is 'another one of these' going and the dialogue has pointed to roll rate so please factor in the following. While roll rate is a nice buzz phrase it is no more the ultimate decisive factor in air combat than is any other one factor of performance.

An aircraft performing a snap roll in front of an opponent is simply doing aerobatics by rotating his machine on the horizontal axis. After all, the crate ends up in the same attitude as when the maneuver began. IE., he's gonna get his *** shot off if he thinks it's an evasion maneuver.

The ability to roll with some verve is valuable when measured in coordination and combination with other maneuvers. A split S could be performed quicker with a good roll rate. A "wings vertical" elevator turn could be performed rapidly in that the ship could maneuver into the wings vertical position quickly due to fast aileron response in a partial roll.

Allegedly the opposing aircraft in the 6 o'clock position with a somewhat slower roll rate would be unable to follow these snappy maneuvers dependent on aileron response. Yes and no. At what range is the trailing opponent?

If the pursuer is 50 yards behind the ability to "roll" as such could be a decisive factor. This is going back to a WW I-style "dogfight." 

Most of the success or lack thereof lies in relative distance of the 2 planes apart. If the quarry is 4-500 yards/meters away and begins performing rolling maneuvers he is simply throwing away his distance advantage. It is a simple matter to dial in the proper lead based on the relative distance of the pursuer. Minor control input changes the attitude of the nose to the necessary degree to be ahead of the quarry with a gun solution at all times.

The quarry's violent thrashing diminishes his range advantage and simply allows the pursuer to cut the distance easily keeping his guns on target. Thunderbolt pilots were able to "outroll" opponents on a daily basis like this and due to the circular "barrel roll" maneuver. The Jug had a very decent roll rate to begin with and following 109s and 190s which began tight turns allowed the P-47s to use the barrel roll in the direction of the German's turn to come out ahead still holding lead. We're not talking about 100 meters apart because a good deal of gunnery was commenced at 500 meters behind an enemy target often. 

As a dfensive maneuver a barrel roll is useful only when the pursuer is pretty close and moving fast, as the intent is to make him overshoot by using a lateral movement to shorten the distance you cover in a straight line. It will ruin his gun lead because he can't compensate quickly enough if he is close. Attempting to minic the maneuver by the trailing pursuer will also ensure the quarry in the lead that the opponent will not be attempting to fire unless he is a novice.


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## wmaxt (Jun 9, 2006)

Twitch said:


> As I see there is 'another one of these' going and the dialogue has pointed to roll rate so please factor in the following. While roll rate is a nice buzz phrase it is no more the ultimate decisive factor in air combat than is any other one factor of performance.
> 
> An aircraft performing a snap roll in front of an opponent is simply doing aerobatics by rotating his machine on the horizontal axis. After all, the crate ends up in the same attitude as when the maneuver began. IE., he's gonna get his *** shot off if he thinks it's an evasion maneuver.
> 
> ...



I pretty much agree. Add to that a trailing aircraft doesn't want to roll as fast as the lead aircraft or he risks overshooting the next maneuver. Another aspect is that unnecessary rolling just slows the aircraft down, again adding to the advantage the trailing aircraft.

A fast roll can give a momentary advantage and if followed up by an appropriate maneuver can be extended into a break away.

wmaxt


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## lesofprimus (Jun 11, 2006)

> An aircraft performing a snap roll in front of an opponent is simply doing aerobatics by rotating his machine on the horizontal axis. After all, the crate ends up in the same attitude as when the maneuver began. IE., he's gonna get his *** shot off if he thinks it's an evasion maneuver.


If the pilot is using the roll as a defensive manuever, he's gonna kick full rudder, slam the stick foward upon 75% of the roll, drop power ect ect....

As many gun camera footages show, many a -190 used this same move to get an Allied fighter off his ***...


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## zipo (Dec 11, 2006)

Didnt the XIV have 4x 20mm hispano cannons (config C) maybe i missed someone mentioning it ? also im sure the max speed is 447mph not 437mph


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## Chingachgook (Dec 11, 2006)

My 2cents... late war aircraft leave me cold. Too much torque effect. I don't think I'd like to fly a Spit 14, La7 or late 109s - sort of over developed pigs if you ask me... (ok, ok, you didn't ask me!) US airframes seemed to fit their engines better at this timeframe (?) Ta-152 seems like it might be ok too (big wingspan) (?)


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## Soren (Dec 13, 2006)

That makes no sense Chingachgook, and you can be sure that no right-minded fighter-pilot will agree with you. 

You're making torque sound like a huge problem, yet in reality it isn't. The speed of the rotating prop is what creates the gyro effect, however the speed of the prop didn't change significantly from type to type, only the ability to keep up the RPM's when drag/resistance increased or prop efficiency decreased. 

Remember the prop isn't spinning at engine RPM's.

PS: Talking about torque, think about what WWI pilots had to deal with !


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## Chingachgook (Dec 13, 2006)

I am just going on what I have read. Hinton also backed this up (is he right minded?). He said planes like XIV had serious torque effect and were very difficult to fly - said doing a tail chase was near impossible. He did say Bearcat was not bad (not sure why - big vert stab?). He said Buchon was hopeless too. 
I have read of many combat pilots who complained of late war aircraft having issues with torque effect, many P-38 pilots said they like their plane for exactly this reason (no torque effect).
I thought that it was just an issue at take-off - Hinton said no - he said was always a problem on some planes.
Wasn't ww1 plane issue with rotory engines? Entire engine rotates...


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## Glider (Dec 13, 2006)

I think you will find that torque was mainly a problem on take off. If you are not ready for it the plane had a tendancy to swing which had to be controlled by rudder. Once in the air it wasn't a serious problem as the airflow over the fin and fuselage would control it. On take off of course the speed isn't sufficient for these to have effect.

Feel free to comment on this as Gliders don't have these problems, so I lack hands on experience.


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## Matt308 (Dec 13, 2006)

I think Chingachook is one to something. Everything that I have read indicates that on some airframes torque was either a help or a hindrance. I specifically recall reading fighter tactics indicating roll tactics to be expected by Japanese Zeros since roll rate was so severely limited in the direction counter to torque.

Torque being a serious issue in the more powerful airplanes was personally confirmed on numerous occasions by an older gent in the office who flew Spads. And that was a BIG plane!


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## Chingachgook (Dec 13, 2006)

Hey Soren...

PPPPPPPPPPFFFFFFFFFFFT!!!


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## twoeagles (Dec 14, 2006)

You guys are right. I can tell you from personal experience that torque
is most noticed with big power advances, but it is also an issue when 
rolling...You can always roll easiest away from the prop and you can really
feel rolling into the prop. Those Griffon powered Spits, with the exception
of the contra-rotating Sea Fires, required hard over aileron on takeoff
roll, too, because as power was advanced, the oleo would almost completely
compress. The only time torque is not an issue is when you are cleaned
up, trimmed, and in a comfortable cruise.


I turned away a chance to fly a Buchon because when I tried high speed
taxiing, it was an out of control monster - there was not sufficient rudder
available to make me feel comfortable. It scared me, I shut down and got
out. And that was all about torque and insufficient surfaces to control it.


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## Sgt. Pappy (Dec 14, 2006)

Jabberwocky said:


> Incorrect adjustments of the FW-190s alierons could have a dramatic effect on roll rate though. Hence you get some screw tesing results, like the USN test of the FW-190A5 which has the Corsair outrolling the Wurger, something that wouldn't be possible with a properly maintained FW-190.



With this in mind, I was wondering if the Corsair could outturn the Spitfire IX (and/or XIV which turns almost identically according to RAF tests) or La-7 in a flat turn - when using flaps, of course. In Aces High II, that apparently can be done, but I don't understand as to why. Both power loading and wing loading seem to aid the Spitfire IX, but, somehow, those Hog flaps still do it. 

Some say it's the bent wing (that is, if it really was possible) that allowed the F4U-(1A, 1D, 4)to outturn the Spitfire IX. Others don't buy that, and most, if not, many AHII players find that the Corsair is overmodelled - even those who are great at flying it and like it alot.


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## Soren (Dec 15, 2006)

As stated the Torque is most noticed on take off, as the more powerful the engine the more quickly you'll be able to throttle up. (Quickly building up momentum) However mid-air the difference in the gyro effects on early war to late war planes wasn't that pronounced.

Now that a plane rolls faster to the left than right is another issue, and depends fully upon the direction of the spinning prop - all WWII fighters suffered from this. 

*Sgt.Pappy*,

The Corsair wouldn't be able to outturn the Spitfire, its simply to heavy and draggy by comparison.

And about the gull wing, well the only reason for it was to gain clearence for the larger prop, it had a slightly negative effect on lift though because of the angle.

Still the Corsair was an amazing airplane though.


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## twoeagles (Dec 15, 2006)

Oddly enough (well maybe not odd) even when I had access to fly 
some old aircraft like the FG-1, P-51D, P40N, etc. it never occurred to me
to see just how tightly I could turn. For one thing, you always worry about
load factors on old airframes, and I don't like doing anything beyond five
g's anymore. So it is really fun reading these threads - I am learning
a awful lot about WW2 aircraft. Thanks, guys!!! Keep up the great 
arguments!!!


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## Sgt. Pappy (Dec 15, 2006)

I know, Soren, that the Corsair's heavy frame and draggy shape could not allow it to turn tighter than a Spitfire VIII,IX,XIV (all of which turn almost identically according to RAF test)... but how about with FLAPS deployed? 

According to Aces High II, the all F4U's will turn tighter than the Spitfire when they drop at least 20 degrees of flaps (which can only be dine under 250 mph in the game). Even when both a/c fly under full flap, the Hog will STILL turn tighter, but will have a worse turn rate (meaning that it will turn tighter, but not fast enough to circle behind the Spit). I'm assuming that the Hog is therefore overmodeled.


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## banderson (Mar 10, 2011)

cheddar cheese said:


> Youre right. It is an La-9



Wrong, Sir. The picture unfortunately is of an la-5, the la-7 being an improved version of the la-5FN (e.,. metal spars). The stats below the picture are for an la-7. la-5 and la-7 wings were made of laminated birch. The la-9 was all metal, did not see service in WWII but did see service in Korea.


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