USN adopts V-12 engines: pros cons?

[wuzak]

The F2A and F4F-3A and F4F-4B used 1 stage, 2 speed blowers.

And they were replaced by the F6F and F4U.

 

[RCAFson]

And they were replaced by the F6F and F4U.

Well a single stage, 2 spd blower engine would be lighter and produce more power at lower altitudes since the SS blower would draw less power, with lower fuel consumption. Lighter weight would also imply lower stall speed, better manoeuvrability and better landing characteristics, so it is a trade-off. It seems to me, that the poor supercharger on the Allison might have been a factor in the USN rejecting liquid cooled engines.

 

[wuzak]

The two stage supercharger would require less power to drive....always.

The question is, is the extra weight worth it?

 

[wuzak]

When I say the 2 stage requires less power to drive "always", I mean for high boost, ie max power, situations.

At lower boost settings the 2 stage supercharger may drop off the efficiency map sooner. But in high boost situations the efficiency remains high over a wider range.

The 2 stage supercharger will give more power at all altitudes.

 

[tomo pauk]

For the US Navy to buy it it has to work off US Navy carriers. Both P-40s and Mustangs had longer take-off runs, higher take-off speeds and higher landing speeds than F4Fs.

Mustang had a laminar flow wing - great at high speeds, not that great at low speed - and such a wing was not a part of my proposal. The proposal does include a tad a bigger wing than for P-40.

Later carriers had heavier decks and upgraded arresting gear to handle heavier aircraft. Increasing the landing speed by 10% increases the amount of energy the arresting system has to handle by 21%. A 14% increase in landing speed ( and that is percent not mph or KPH or knots) increases the energy by 96%.

The increase of speed by 14% increases energy by 30%, not by 96%. The increase of speed by 40% will make those 96%.

The P-40 and mustangs had take-off runs around 300 ft longer than an F4F in calm wind. A P-40E with drop tank needs over 600ft even with a 30kt head wind, making deck parks and flying off without catapult difficult and/or tedious. Using Catapults for large group launches slows down the take-off rate and means that the first planes launched have to stooge around for 15-20 minutes (or more) until the last planes launch. Another reason the Navy wanted more fuel and why operational ranges varied so much from "book" or "Yardstick" ranges. Same problem on the return. If 20-30 planes arrive as a group how long does it take to get them down? They do not turn of the runway and taxi to dispersal under their own power. Any accident even small, can block landings for precious minutes leading to ditching.

Take off performance is more than just wing loading and power to weight ratio. The actual co-efficient of lift of the wing comes into play and that is part airfoil and other factors.

Hmm, I'm curious about your take wrt. the topic, even only about the fighter that fits here?

 

[Shortround6]

The P&W two stage used a fixed one speed gear ratio on the engine supercharger and a 2 speed drive with a neutral on the auxiliary stage. It took no power to drive until it was clutched in at around 8,000ft or so on some models.

two stage superchargers do take less power to reach the same level of boost as a single stage supercharger. Level of boost being a given pressure ratio and not a given pressure limit. You can't compare 48in MAP at 10,000ft to 48"map at 20,000ft because the supercharger has to do more work at 20,000 due to the thinner air.

 

[Siegfried]

The P-51H was considered suitable for carrier use and it seems it was on its way to being navalised. The lengthened tail combined with greater tail area had greatly improved its low speed handling. There were experimental lengthened tail versions such as the P-51F well prior to this. With carrier born P-51s the bloody invasion of Iwo Jima can be delayed and reduced to a starvation siege.

 

[davebender]

That won't help the USN during December 1941, when they need all the help they can get.

 

[wuzak]

That won't help the USN during December 1941, when they need all the help they can get.

Nobody specified 1941.

However, if the USN adopted the V-1710 they

a) wouldn't get many aircraft before December 1941 - presumably the AAF would get priority
b) would initially use single stage altitude rated engines, a la P-40. This may have given impetus in developing the single stage supercharger, particularly to get better altitude ratings
c) would have pushed Allison to develop the two stage engine earlier/faster. The V-1710 2 stage development began around the same time as the Merlin 2 stage development - but it took 2 or more years longer to get into a production airframe. With the Navy loath to use turbos the two stage engine may have been able to be deployed earlier, thanks to the additional funding and orders that Navy backing allows.

 

[davebender]

What's wrong with that?

Me-109 is arguably the most successful fighter aircraft ever built. It was powered by a V12 engine with single stage supercharger.

 

[wuzak]

What's wrong with that?

The Allison single stage supercharger, at least in the early war years, was kinda breathless at altitude.

Me-109 is arguably the most successful fighter aircraft ever built. It was powered by a V12 engine with single stage supercharger.

The DB engines were also of larger capacity, used higher compression ratios and a variable speed supercharger. And even then Daimler-Benz evolved a few 2 stage variations to help with altitude performance - though they never made it to production.

 

[Shortround6]

What's wrong with that?

Me-109 is arguably the most successful fighter aircraft ever built. It was powered by a V12 engine with single stage supercharger.

And the 1940-41 versions of the DB 601 had critical altitudes of???????

the 109 in it's early versions ( and even for most of the later ones until 1944) got it's "altitude" performance from being light, not because the DB engine was all that hot at over 6000 meters despite it's supercharger drive and design.

 

[Denniss]

The 40/41 DB 601 had a static critical alt of 4.5km (601A) and 4.8/4.9km (601N/E).

 

[Tante Ju]

And the 1940-41 versions of the DB 601 had critical altitudes of???????

the 109 in it's early versions ( and even for most of the later ones until 1944) got it's "altitude" performance from being light, not because the DB engine was all that hot at over 6000 meters despite it's supercharger drive and design.

Yes, true, but also true that the Bf 109 was light exactly because the DB 601 complete system was light and efficient on fuel... meaning less fuel needed to be carried. This approach may be not appropriate for naval fighters though, which generally required larger airframes.

 

[tomo pauk]

Bf-109 was light because it was conceived around 700 PS/500 kg engine, 2/3/4 LMGs, and ~300 L of fuel. Not because the 601/605 was an early incarnation of Citroen AX's motorization.

 

[Shortround6]

Yes, true, but also true that the Bf 109 was light exactly because the DB 601 complete system was light and efficient on fuel... meaning less fuel needed to be carried.

The 109 was light because, for the most part, it carried crap for armament and was never intended to have long endurance. The DB 601 (and the whole 600-605 series) were decent engines that did things in a different way than the Allison and Merlin. They were better at somethings and not so good at others. Given the fuel situation the Germans had the could not use the same solutions to get power that the Americans and British could use after 1941/42.

16 US gallons of fuel is only 96lbs. That is a 15% increase in fuel for the 109. granted you need a bigger fuel tank. I doubt that the DB engines were 15% more efficient in cruise than the allied engines.
96lbs is a little over 300 rounds of linked .50 cal ammo.

The early 109s (A-D) with Jumo 210 engines carried 2-4 7.9mm machine guns and around 2000 rounds of ammo did they not? and about 250 literes of fuel? The installation of the DB 601 was a interesting and well done job. But except for the E with the 20mm guns in the wing ( and those were light weight, low powered and limited in ammo) the 109 doesn't get good armament unless it is a gunboat until the MK 108 arrives and that gun is a mixed blessing. The 109G-6 with the hub 20mm and the two 13mm guns is about one of the two times the 109 carried close to parity armament with it's contemporaries. And it doesn't show up in numbers until the NA campaign is almost over.

The Americans were handicapped by the .50 cal mg. A 109G-6 without under wing guns is carrying less than 1/2 the weight of guns and ammo the P-40E is. A 109F-4 is carrying even less, 39%. Please note that I am talking about the weight of the armament as a "payload" of the plane and not discussing the effectiveness of the armament.
Claiming the 109 was greatly superior at altitude because it's supercharger setup was so much better is drawing a false conclusion. Yes it was a bit better but there are a lot of other factors that also come into play.

 

[Tante Ju]

The 109 was light because, for the most part, it carried crap for armament and was never intended to have long endurance.

The first part makes a fine arguement but what about the facts? Gunboat 109s hardly lacked armement effectiveness or weight for that matter, but all it took 215 kg extra to carry that armament plus ammo. The P40E carried what, 550 liters compared to 400 liters on the 109G, or about 1/3 more? That's 150 liters of difference or about 114 kg extra only, and 330 kg with all the guns and extra fuel - let's make it 350 kg for the fuel tank enlargement etc.

Now the 'everyday' 109G weighted about 3050 kg in it's normal state, but it would weight no more than 3400 kg even with a rather potent battery of 3 x 20 mm cannons and as much fuel a P-40E would carry. And the P-40 is still 1000 lbs heavier and still much slower, and now it has considerably less firepower too. So where's all that 1000 lbs went for, I wonder? I doubt it all be in the airframe, after all, the airframes themselves were always are very, very light, a couple of hundreds of kilograms, or a ton at worst. Most of it was the fuel, and engine and things that came with the engine.

So the usual argument that it was simply so easy to get the thing that fast by cutting back on armement and/or fuel simply does stand up to the examination of the facts. Being lighter, smaller, and less draggy was actually achieved with good engineering practice, propose built (lightweight and effective) aircraft guns, and engines that had very high installation efficiency. Under installation efficiency I mean that for a given weight and drag, after substracting the power required to balance out the weight of the complete engine installation, that is: weight and drag of the propellers, radiators and other such devices, the weight of fuel carried in climbing or level flight condtions etc. - what power remains to actually drive the airplane..

Essentially the P-40's problem was that it was way too large of an airframe for a SE fighter with limitated intended mission capacity. It's airframe was simply sub-optimal.

The DB 601 (and the whole 600-605 series) were decent engines that did things in different way than the Allison and Merlin. They were better at somethings and not so good at others. Given the fuel situation the Germans had the could not use the same solutions to get power that the Americans and British could use after 1941/42.

I think did not need to use the same solutions is a better choice of word. Having choosing - correctly - and engine with much larger displacement from the start meant that their engineers did not have to go through all the trouble Merlin and Allison engineers did have to. Developing a new engine during the war was hardly an option, it took at least 4 years for anyone. Even those large displacement engines that design was intiated at the start of the war or before did not make it into service in meaningful numbers until the end the of war. See Griffon, DB 603 etc.

And of course one of the great pros of the DB series compared to the Merlin or Allison was that it was capable of mounting weapons between the cylinder banks. That alone made bulky and very weight inefficient wing armament redundant, it made unneccessary to increase the size of the wings - and greatly increase drag - just to make space for guns you cannot mount in the fuselage, where everybody would have mounted them in the first place, had they had a choice. If you can have a cannon that is twice as effective when installed in the centerline, you do not need to install two cannons in the wings instead of it. Effectively, the weight of one cannon and ammo was spared.

This was further aggrevated that US aircraft designers did not have proper gun for aircraft to rely on. Under 'proper' I mean compact, lightweight and capable of electric syncnronisation. If it's not compact, the wing has to be a larger than optimal size, thicknes where the bulkier gun and ammo will fit. If it can't be syncronized it will suffer a great reduction of rate of fire as US cowl mounted .50s did, neccessiating to place the guns in the wings (and always more since single assymetric installations in wings are inpractical). This leads to further increase in size of the wing, and again more increase in wing size and drag. Concentration and fire effectiveness will be smaller, and to get the same number of hits on target during the same time period, the number of guns has to be further increased. This again leads to more bulk since wing installations are far more complicated and bulky overall - proper, heavy duty fixings are needed in the wings since you can't just lay the gun against the light alumium skin, and heating must be provided (neither much of an issue with wing mounted guns).

At this point the same powered engine will invariable lead to inferior performance in wing gun aeroplane which it has to compensate by more power, more fuel and bulkier engine system auxilarry systems carried (bigger radiators, intercoolers, heavier propeller blades etc.).

The early 109s (A-D) with Jumo 210 engines carried 2-4 7.9mm machine guns and around 2000 rounds of ammo did they not? and about 250 literes of fuel? The installation of the DB 601 was a interesting and well done job. But except for the E with the 20mm guns in the wing ( and those were light weight, low powered and limited in ammo) the 109 doesn't get good armament unless it is a gunboat until the MK 108 arrives and that gun is a mixed blessing.

Good armement is not the number of guns. Good armament is a mix of guns, ammo capacity and effectiveness of delivering fire and it's effect on impact. There may have been two MG FFs, which in their bare weight weighted about 56 kg and fired 120 20mm rounds in 7 seconds (with lower MV though), but it's difficult to see how that was supposedly a better armement than a 42 kg cannon firing 200 20mm rounds in 16 seconds. The Germans certainly did not see it that way, otherwise they would have kept the two MG FFs in the wings.

The 109G-6 with the hub 20mm and the two 13mm guns is about one of the two times the 109 carried close to parity armament with it's contemporaries. And it doesn't show up in numbers until the NA campaign is almost over.

It depends - the USN rather conservatingly estimated one 20 cannon to worth three .50 mgs, and centerline armament is much more effective - some say twice as much, but let's be conservative and say 50% more effective. Based on that - USN based - estimate, basically any Bf 109G had a basic armament equivalent to about six .50s. Pretty avarage, but quite sufficient. What is getting forgotten that six .50s was about the max the P-40 could carry, but any 109 could just pull the other hand from behind the back and mount an extra pair of cannon, which - if we go again with the USN's formula: 3x20mm= 1x3x1.5 + 2x3 = 10.5 .50 plus the change of cowl MG/HMGs for about 1 and a half fifties worth.. so if my math is correct and the USN got in about right, which 109 contemporary carried an equivalant of TWELVE .50 machine guns...?

The Americans were handicapped by the .50 cal mg. A 109G-6 without under wing guns is carrying less than 1/2 the weight of guns and ammo the P-40E is. A 109F-4 is carrying even less, 39%. Please note that I am talking about the weight of the armament as a "payload" of the plane and not discussing the effectiveness of the armament.

Well both the F-4 and G-6 were quite easily capable of tripling that payload. I have never particularly got why you go on with these 'weapon payload' figures, as they are completely meaningless. Sometimes I get the feeling you have also forgot why it's so darn important to carry heavy but less effective guns. I am pretty sure that a 109 could carry five .50s in the place of it's cowl/hub/gondola weapons, plus a 100 lbs piece of lead whereever you want to place that.. or more. The real question is - why on Earth anybody would want to do that?

Claiming the 109 was greatly superior at altitude because it's supercharger setup was so much better is drawing a false conclusion. Yes it was a bit better but there are a lot of other factors that also come into play.

I agree it was important. Though the supercharger setup was important - other single speed engines either had to sacrifice low or high altitude performance because of the inflexibility of such setup. They could not have both. The Spitfire V seems to have to sacrificed low altitude capability. The P-40 appears to have sacrificed high altitude capabilty.

 

[davebender]

DB engines were larger capacity, higher compression ratios and a variable speed supercharger

DB601 accomplished this with a weight and bulk roughly similiar to the Allison V-12.

The solution here is obvious. The USN rejects the Allison V-1710 for poor performance and searches for another V12 engine solution. That could be an improved Allison V12 or it could be a different engine.

 

[wuzak]

DB601 accomplished this with a weight and bulk roughly similiar to the Allison V-12.

The lightweight construction of the DB 601 probably limited its development and the power it could produce. Hence the development of the DB 605.

The solution here is obvious. The USN rejects the Allison V-1710 for poor performance and searches for another V12 engine solution. That could be an improved Allison V12 or it could be a different engine.

Or they could push for better superchargers and development. The additional funding could have definitely helped Allison with resourcing, and additional priority would have been attached to higher altitude rated superchargers, multi-speed superchargers and 2 speed superchargers.

Or they could do what they did historically - keep with radials.

 

[gumbyk]

But, the premise is that they have rejected radials, and gone the V-12 route.
I would think that the extra money available would accelerate V-12 development. IMO, you would see better super/turbo-charging.