A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

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pinsog said:
Thank you
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This is the other memo about overboosting the V-1710-39 on Allison engined Mustangs at up to 72" Hg with no apparent problems. As Shortround said, the Mustang may have gotten a little big more Ram, but there is no reason to assume that a slightly lower but still very high boost rating (like the 70", 66" and 60" Hg mentioned in the Allison memo) would be a problem for a Kittyhawk with the same engine, and of course other sources corroborate this. What we don't unfortunately have is a speed test for a Kittyhawk running at 66" or 70" boost, although the boost would only work at lower altitude, it seems to have contributed to a useful escape manuever / disengagement option for P-40 pilots.

E-GEH-16

The Mustang I incidentally, would have been a viable low altituide fighter but for problems with the ailerons which were corrected in the packard-merlin V-1650-3 engined P-51B and later versions.
 

My terminology is probably off -- maybe I should have said 77 degrees. Here is a quick n' rough sketch of the 10-swg armour (Hurricane's was similar) protecting the petrol tank from return fire. The engine would obviously afford most of the protection in that instance.



EDIT: Though I said otherwise above -- I should mention that this armour was actually meant to protect the pilot from rounds going around the engine and through the petrol tank. Any incidental protection to the tank was just a bonus.
 

Any extra protection is better than nothing, and 77 degrees of deflection would make it a bit better even just using duralumin, but I would call that 'glancing blow' or 'bullet resistent' protection rather than true bullet proof. For the latter you need a steel plate of about 6mm, or tempered steel of about 4mm, maybe a bit less with sloping... just to protect against rifle caliber bullets at ~ 200 meters. During WWII they started with the former and eventually kind of 'rediscovered' the latter. They also experimented with some steel alloys adding vanadium and molybdenum and so on to make stronger and therefore lighter aircraft amor. On the other hand steel core or tungsten core bullets which cold punch through even thick airplane armor were also widely used.

For comparison to the above, on a Sturkmovik the 'bathtub' armor was 4-8mm and the armor plate behind the pilot was 13mm. I don't know if that was steel or tempered steel.
 
'Glancing blow' it may be, but that's the target presented to a Heinkel. And from a gunner's perspective it's a centre-of-mass direct hit that would have potentially killed the pilot.

 
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Schweik said:
For comparison to the above, on a Sturkmovik the 'bathtub' armor was 4-8mm and the armor plate behind the pilot was 13mm. I don't know if that was steel or tempered steel.
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"Bathtub" - homogeneous tempered steel. The one behind the pilot - so called "cemented" steel of different composition, at least until 1943. It was probably changed later.
 

We obviously have different sources of information. Based on 50 aircraft per squadron for every 6 months in front line then:-
635 Tomahawk IIb's should last 12 months in 6 squadrons so 1941/42
1000 Kittyhawk I/Ia's should last 12 months in 10 squadrons so 1942/43
Etc
 
Kevin J said:
We obviously have different sources of information.
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In what sense? All of the squadrons I listed flew Tomahawks in 1941, that is not hard to verify from a variety of sources.
Based on 50 aircraft per squadron for every 6 months in front line then:-
635 Tomahawk IIb's should last 12 months in 6 squadrons so 1941/42
1000 Kittyhawk I/Ia's should last 12 months in 10 squadrons so 1942/43
Etc
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I think the 50 aircraft per squadron for 6 months is just a rule of thumb, there is nothing hard and fast about it.

Obviously the rate aircraft were actually used in the war depended on a lot of factors like attrition from combat, maintenance and accidents; training and other needs; availability of spare parts (whether some planes have to be cannibalized etc), availability of fuel, ammunition and pilots (which will affect the sortie rate) and so on. Do you think 50 aircraft lasted 6 months in Malta? Or during the BoB? Or over Stalingrad? A lot of units in the Western Desert had quite high attrition rates too.

By contrast a unit doing coastal patrol from say, Panama, Vancouver or Durban, had a much lower attrition rate (at least from combat losses).
 

My source was an Osprey book on the British P-40's. So the American Cobra's were one of the safest aircraft to fly as they were restricted mainly to coastal patrols in the Med and rear area air defence in the Pacific, so yes agreed on that one. As for the Yak-1/7, riding shotgun as an Il-2 escort as it's main task no doubt was the major contributing factor in the paucity of high scoring aces.
 
Just read Subject: Production of P51 Fighter airplane production from WWIi aircraft performance...
In the NNA memorandum...
It was talking about increasing blower ratings on the P51 Mustang.
"Allison is preparing to bring out a two speed engine which will increase speed substantially
more than 400 mph at at least 21000 ft"

So they knew this !
 
Schweik said:
But they made a really crude, oversized one without all the important bits you need to prevent detonation like intercoolers
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If you are responding to Dan Fahey, he was talking about a 2 speed supercharged engine, not a 2 stage supercharged engine.

Generally speaking, 2 speed, single stage supercharged engines did not use an aftercooler/intercooler.

As for size, a 2 speed engine shouldn't be much bigger than the single speed engine, except in Allison's case where the impeller of the eventual 2 speed engine was 10.25" in diameter, compared with the regular 9.5" for the regular single speed engines.
 
From the timing of that Memo they may have been talking about the first batch of engines that used 9.60 gears for the 15,000ft altitude. about 25 were made for P-40s and 25 for P-39s, numbers differ as while that was the planned number they ran into the gear failure problem pretty quick and a number of the engines were converted back to the 8.80 gears. It took Allison almost a year to actually get the 9.60 gears into service. Allison may have hoped to develop and put into service a 2 speed engine with a bigger basic supercharger, but other stuff kept getting in the way, Like the two stage engine program. The Army had placed a contract for one two stage engines (not two speed) in Dec of 1940. a contract for 3 two stage remote gearbox engines (P-39?) was placed in June of 1941.
Everybody knew what the problem/s were. Finding a solution with the limited engineering manpower Allison had (and many other companies) was the roadblock to rapid development.

Just fixing the existing basic engine during 1940-41 took up a lot of time and effort. A lot of people deride the backfire screens but the "solution" was multi pronged.

It included switching the intake manifolds to a heavier aluminium one instead of a very light weight magnaismum one which was know to burst open on occasion (in flight) when the engine backfired and sometimes resulted in the loss of the plane, the manifold itself actually catching fire on occasion.

All of the changes that affected this problem (and others?) needed hundreds of hours of test stand time and in the air time. Getting the existing engines to work took priority of future engines.
 

Yeah my bad, I misread that I thought he was talking about their two stage engine. I gather part of the problem was that the single speed supercharger was integral to the V-1710 engine so putting in a geared one like the Merlin XX had or a hydromatic one like in the DB 600 series would have required changing that. Maybe they could have borrowed some technology from Pratt and Whitney... the R-2800-8 had two stages and two speeds and seeemed quite reliable.

Even just a two speed Allison would have been a nice asset to have - just look at how much better P-40F performance was over P-40E. I understand that Allison had limited engineering manpower and were very busy in 1940-41 but by 42 or 43 I would think they could have come up with something. Seeing how P-40s were still in use through the end of the war (and P-39's too, at least in Russia) and the Allison engined ones especially remained plagued by their altitude limitation. It could have come in handy.

I think the issue is that all the focus in the US leadership was on turbos, which did eventually work out, it's just unfortunate it took so long to get them sorted out and that they ended up being so big. This is often a thing in US military procurement, particularly for planes. They want to take a quantum leap past everyone else but often take on very expensive and difficult technical challenges that don't pan out initially. It went this way with air to air missiles, mach 2, stealth, etc.
 
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The V-1710's supercharger was "integral" in that it was fitted to the rear of the engine and driven off the back of the crankshaft via a gear set that increased the shaft speed.

What the supercharger lacked, compared to the Merlin XX, was a second set of ratios and a system to decouple each of the ratio sets.
 


For Yak 1 and 7 specifically, in part any 'paucity' of high scoring aces would be due to the incredibly desperate circumstances and dire straits for the Soviet Air forces in general in the early war. However that said, there seem to be quite a few high scoring Yak aces - the Osprey book on them has two pages of aces starting with 52 victory claims on the top of the first page and ending with 24 victory claims on the bottom of page two.

Unfortunately it doesn't break it down by type but from looking at the units names, many started with Yak 1, then got Yak 7, then Yak 1B or 7B, then Yak 9 and etc. A few also flew Lend Lease types or Illuyshin / Lavochkins in the early war.

Bottom line is to me it seems like there were quite a large number of Yakovlev fighter aces, their top 3 got more than all Anglo-American Aces and they had considerably more with 30 or more claims than the US and Britain combined. Looks like the counting Commonwealth / colonials RAF had 5 (per wikipedia- Roland Stanford Tuck, Buzz Buerling, Johnnie Johnson, Cherry Vale, and Pady Finucane) with 30 or more victory claims, and the US had 3, (Bong, McGuire, and David McCampbell). The Osprey book on Yak Aces lists 19 with 30 or more victory claims. So I think the Yak looks pretty damn good actually. Probably most of those are Yak 9s and Yak 3s, but plenty are also with earlier marks.
 
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Agreed, but if you look at the Osprey book for the Yak-1/7 aces it makes for pretty grim reading. Basically, like the Spitfire V they were outclassed by the Bf 109F-4/G-2's, more so than was the case with the Spitfire V.
 
Just curious !
The early P51's with the Allison engine...the Brits them working reliably at 70 inches.
One of the admiring aspects was it ability to fly at very low RPM in economy mode.

But that plane had to be fast at low and medium altitude.
Just no documentation how fast they got it.

Does any one have a calculated guess.
The Brits claim it was never chased down from planes that had an altitude advantage.

D
 

It's all on wwiiaircraftperformance.org, somewhere around 370/380 mph at ground level IIRC.
 
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