Spitfire MK.XIV and La-7

[Anonymous]

*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 !

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.

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]

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]

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

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]

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

 

[Anonymous]

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



Lunatic

 

[Soren]

 

[the lancaster kicks ass]

 

[GregP]

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.

 

[Jank]

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]

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]

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]

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]

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]

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.

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

 

[Soren]

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

 

[Jabberwocky]

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.

 

[Soren]

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.

 

[Jabberwocky]

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.

 

[Twitch]

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.

 

[wmaxt]

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.

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