How good a plane was the P-40, really?

[Wild_Bill_Kelso]

I don't know if the peculiarity of Allison engines was already mentioned here (I'm just too lazy to look for it). Soviet aviation technicians noted that the engine sound changes little when the supercharging increases above the allowed limits - unlike other engines. Thus. the pilots did not hesitate to use it in flight. It is clear that the engine lifetime was reduced several times, and the maximum speed of many Kittyhawks after this ruthless exploitation was below 400 km/h.

Yeah they burned out the engines fast, I think it was mainly to do with the cleanliness of the oil in field conditions. Many Soviet pilots referred to this as 'oil culture'. They worked a lot of these problems out with the P-39 before putting into the field.

 

[Wild_Bill_Kelso]

I was trying to keep the individual lines short, and I got "lucky" in that the weight breakdowns kept saying 720lbs for fuel until the near end, Which is one reason that some of the service tests change. For some reason the US and Curtiss agreed that 120US gal was "standard" despite what the tanks actually held. The 52 gal drop tank was an attempt to make up for the reduction from 181 gallons in the P-40 to under 150 gallons in the P-40B.

There was a smallish internal tank in the fuselage, behind the pilot, I forgot how many gallons. It was often not filled during shorter missions, because it posed some of the same stability problems as the fuselage tank in the P-51. If it was filled (either for a longer ranged mission or an anticipated long-duration patrol flight) they would try to use that fuel first, even before the external tank.

The key factor though was that they would rarely fight with that tank full.

Incidentally almost all Allied fighters available were sometimes readied for scramble with half fuel in the South Pacific, for better climb performance. I don't know if they did that anywhere else. I think they started doing that in Malaysia and Java.

Curtiss themselves say for the P-40D
15,000ft at military power, 359mph without tank and 330mph with tank
15,000ft at 1000hp(normal) power, 345mph without tank and 324mph with tank. which doesn't track well to be but.........
15,000ft at 600hp (60% normal), 285mph without tank and 266mph with tank.

This means with the external tank? Maybe that is what the Wikipedia numbers are based on.

The D was supposed to have 175lbs of armor and glass together, some times the weights are separate.

Most of the specifications list take-off speeds and most give take-off and landing distances, sometimes for both runway and over 50ft obstacle. The P-40 was not a Spitfire or Hurricane here although much better than a lot of other American fighters.

Those high lift wings causes some issues, especially the Hurri one, but they did give you near STOL capability

Speed obviously didn't change much but climb took a real hit due to the increase in weight.

Some of the British/Commonwealth climb tests are going to be quite different than the US climb tests depending on test procedures. Standard British procedure was to use the "normal" rating (2600rpm/1000hp) for the entire time so climb really suffered in the first 5 minutes compared to American testing.
They test their own planes the same so all the British pilots had some understanding of what was going on.

Makes sense. They wouldn't be climbing at high power normally, unless it was a scramble. That would greatly reduce range if they did, as you know.

 

[Shortround6]

Yeah they burned out the engines fast, I think it was mainly to do with the cleanliness of the oil in field conditions. Many Soviet pilots referred to this as 'oil culture'. They worked a lot of these problems out with the P-39 before putting into the field.

It may also depend on which engines they were using, Beating up on the Tomahawks was not going to end well. They for sure did not have the nitrided crankshafts nor the better crankcases (less flex) so better oil culture could only do so much. Some of the early British planes (Tomahawk Is) may not have had the shot peened crankshafts. Over revving/over boosting those could really shorten the life.
The Better engines showed up part way through the P-40E/Kittihawk production so how many early ones did the Russians get?

 

[bf109xxl]

Yeah they burned out the engines fast, I think it was mainly to do with the cleanliness of the oil in field conditions. Many Soviet pilots referred to this as 'oil culture'. They worked a lot of these problems out with the P-39 before putting into the field.

"Oil culture" was another factor. I don't know which one was more important.

 

[Wild_Bill_Kelso]

It may also depend on which engines they were using, Beating up on the Tomahawks was not going to end well. They for sure did not have the nitrided crankshafts nor the better crankcases (less flex) so better oil culture could only do so much. Some of the early British planes (Tomahawk Is) may not have had the shot peened crankshafts. Over revving/over boosting those could really shorten the life.
The Better engines showed up part way through the P-40E/Kittihawk production so how many early ones did the Russians get?

For a long time I thought that they never overboosted the Tomahawks, but it turned out that at least the AVG did.

In this case I'm referring to Kittyhawks though. I believe most of the Tomahawks being used by the Soviets were done-in by the first winter. Soviet aircraft have little drain plugs for ALL fluids so that they can be drained out in the winter. This includes things like oil in the prop hub and wheel bearings etc. The Tomahawks did not have this (or manuals or mechanics instructions) so they had to improvise, which included 'crowd sourcing' silver from nearby peasants farms (probably dowry silverware) to use as solder. IIRC I think they lost about 80% of their Tomahawks the first winter, and they lost a bunch more the next.

Most of the Tomahawks and many of the early (i.e. P-40D/E) Kittyhawks they got were ones that had already 'seen action' with the British, such as in North Africa, and this no doubt meant that the engine time was already substantially reduced. Some were noticeably 'clapped out' when they arrived. Still better than an I-16 or a half-built LaGG-3 I guess. Later when they got many P-40K and M from the US directly and some of these had special 'winterization' packages designed for Alaska IIRC. So these worked a lot better. Most of the Soviet Aces on P-40s flew P-40K.

Like twice HSU Nikolai Fedorovich Kuznetsov here...

 

[pbehn]

I t looks like it's about to hurl.
Or belch.

Fancy going into a fight with just 8 rockets 4 x 20mm cannon and a shark mouth, no wonder ground troops laughed so much at the sight.

 

[Wild_Bill_Kelso]

"Oil culture" was another factor. I don't know which one was more important.

Well, considering that we know they overboosted up to 72" Hg (nearly twice the stated limits in the early manual) in Australia / the South Pacific and the Middle East already in 1942, I'd say it was some kind of maintenance issue.

As noted, the Soviets had far less problems with the later P-40K and M, which arrived less worn out, and with much more spare parts and 'consumables'.

 

[Wild_Bill_Kelso]

Au Contraire.View attachment 760300

It looks hyperaggressive, like some kind of Hindu demon

 

[bf109xxl]

Well, considering that we know they overboosted up to 72" Hg (nearly twice the stated limits in the early manual) in Australia / the South Pacific and the Middle East already in 1942, I'd say it was some kind of maintenance issue.

As noted, the Soviets had far less problems with the later P-40K and M, which arrived less worn out, and with much more spare parts and 'consumables'.

I do not see any contradiction. The young pilots did not realize that they were killing the engine by overboosting for too long - they did not feel much difference in the engine sound. For other engines, the difference was more noticeable, so they were operated under more gentle conditions. But the quality of oil (and maintenance generally) was undoubtedly poor - at least for the first three years of the war. Moreover, not only oil filtration was necessary to improve the situation - Allison required lubricates with other characteristics than the Soviet engines (e.g.., more viscose). The Soviets needed to optimize the composition of the lubricant.

 

[Wild_Bill_Kelso]

I do not see any contradiction. The young pilots did not realize that they were killing the engine by overboosting for too long - they did not feel much difference in the engine sound. For other engines, the difference was more noticeable, so they were operated under more gentle conditions. But the quality of oil (and maintenance generally) was undoubtedly poor - at least for the first three years of the war. Moreover, not only oil filtration was necessary to improve the situation - Allison required lubricates with other characteristics than the Soviet engines (e.g.., more viscose). The Soviets needed to optimize the composition of the lubricant.

I believe they were using Anglo-American supplied lubricants, filters, spark plugs, and fuel. They just struggled to grasp the very high requirements to keep dust and dirt out of the oil for Western engines, since the Soviet engines were engineered with wider tolerances.

I was not there, but your theory that the pilots did not know they were overboosting the engines does not hold water for me, because Soviet pilots noted that they overboosted the engines (and, according to some, increased RPM) and they knew that this potentially shortened the engine life.

A US colonel noted in a letter to the War Dept that British pilots flying Allison engined Mustangs were flying at 72" Hg for up to 40 minutes at a time. "War Emergency" five minute rating was 57-60" depending on specific variant. This is with the same engine (V-1710-73) used in the later model Kittyhawks.

So based on that, IMO, and given that the Soviet fighter bases were typically very close to the front and most missions probably wouldn't exceed 40 minutes, even if they were unusually oblivious, I doubt very much that they would have burned out their engines from overboosting if there were not also serious maintenance problems.

Also, boosting above 50" Hg would leave a big scorch mark down the side of the aircraft, which mechanics were trained to look for.

 

[Shortround6]

A US colonel noted in a letter to the War Dept that British pilots flying Allison engined Mustangs were flying at 72" Hg for up to 40 minutes at a time. "War Emergency" five minute rating was 57-60" depending on specific variant. This is with the same engine (V-1710-73) used in the later model Kittyhawks.

A Mustang was about 40-50mph faster than a P-40 at sea level and could generate a bit more RAM (higher pressure going into the supercharger).
Depending on temperature the air pressure and density of the air could both be higher in Europe than in Africa or the tropics. This is sort of triangle, A higher intake air temperature can increase the risk of detonation but the lower air density may reduce (by a few percent ) the amount of power.
Trying to get 72" Hg out a P-40 may very well require 3200rpm or higher while the Mustang may only require 3000rpm.
The use of the Mustang information helps justify the increased boost to 60" or perhaps even 66". 70-72" in a P-40 may be cutting things too thin.
the -73 engines had all the good parts.

 

[bf109xxl]

I believe they were using Anglo-American supplied lubricants, filters, spark plugs, and fuel.
I was not there, but your theory that the pilots did not know they were overboosting the engines does not hold water for me, because Soviet pilots noted that they overboosted the engines (and, according to some, increased RPM) and they knew that this potentially shortened the engine life.

A US colonel noted in a letter to the War Dept that British pilots flying Allison engined Mustangs were flying at 72" Hg for up to 40 minutes at a time. "War Emergency" five minute rating was 57-60" depending on specific variant. This is with the same engine (V-1710-73) used in the later model Kittyhawks.

So based on that, IMO, and given that the Soviet fighter bases were typically very close to the front and most missions probably wouldn't exceed 40 minutes, even if they were unusually oblivious, I doubt very much that they would have burned out their engines from overboosting if there were not also serious maintenance problems.

View attachment 760347
Also, boosting above 50" Hg would leave a big scorch mark down the side of the aircraft, which mechanics were trained to look for.

Western supplies of lubricating oils were insufficient (at least until 1943), so it was necessary to use the available ones. Many P-40s fought on the northern sector of the front, where the dust was not so important factor, but the problems remained the same. Moreover, many of P-40 (or even the most of them) were moved to the second line in 1943.
I read an interview with a Soviet pilot where he talked about the constant use of overboosting on the P-40 throughout the flight. Memoirs are less reliable sources than documents, the latter are unavailable unfortunately. The misuse of overbusting on P-40s was mentioned also in the book "Aviation Lend-Lease" by Kotelnikov.
Many Cobra pilots mentioned the big difference in engine lifetime between early and late series of the 39Qs.
I just found this particular property of Allison engines unusual. I won't say it was the major reason for all the Soviets' troubles with Allison, but it did contribute.

 

[Shortround6]

A lot can depend on the overboost being used. There is a lot of room between 44" (7lbs boost?) and 60"(15lbs)?) , it is not one or the other.
It also the difference between around 130 US gallons a hour and around 170 US gallons a hour or .5-.66 extra gallons a minute. More than 60" means even more fuel per minute.

 

[Wild_Bill_Kelso]

A Mustang was about 40-50mph faster than a P-40 at sea level and could generate a bit more RAM (higher pressure going into the supercharger).
Depending on temperature the air pressure and density of the air could both be higher in Europe than in Africa or the tropics. This is sort of triangle, A higher intake air temperature can increase the risk of detonation but the lower air density may reduce (by a few percent ) the amount of power.
Trying to get 72" Hg out a P-40 may very well require 3200rpm or higher while the Mustang may only require 3000rpm.
The use of the Mustang information helps justify the increased boost to 60" or perhaps even 66". 70-72" in a P-40 may be cutting things too thin.
the -73 engines had all the good parts.

All I brought it up for was to point out they apparently overboosted the (Allison) engines routinely for a really long time.

 

[Wild_Bill_Kelso]

During long engagements US pilots described in detail (in excerpts I have posted to this forum in the past) overboosting up to 60" and then going back down to military power for a few minutes to cool the engine off, then back to overboosting, over and over through the course of long running fights lasting up to an hour.

 

[Shortround6]

During long engagements US pilots described in detail (in excerpts I have posted to this forum in the past) overboosting up to 60" and then going back down to military power for a few minutes to cool the engine off, then back to overboosting, over and over through the course of long running fights lasting up to an hour.

That is another thing, the book 5 minute limit was subject to the temperature (both oil and coolant) staying within limits. If the temperature went over limit sooner the pilot was supposed to reduce boost. Sometimes the performance tests say an engine wouldn't be in limits at military power, although they sometimes gave an extra 5-10 degrees at WEP power levels. Running at high boost may have been easier in cold weather.

 

[BobB]

During long engagements US pilots described in detail (in excerpts I have posted to this forum in the past) overboosting up to 60" and then going back down to military power for a few minutes to cool the engine off, then back to overboosting, over and over through the course of long running fights lasting up to an hour.

Running military power for an hour, you'd better be defending your home base or you'll run out of gas on the way home.

 

[Greyman]

For a long time I thought that they never overboosted the Tomahawks, but it turned out that at least the AVG did.

Remember that US fighters didn't have automatic boost control until later, so exceeding Allison's boost guidelines (and by how much) was completely up to the pilot -- whether through negligence, desperation, or ... willful disobedience.

 

[Jabberwocky]

The RAAF operated the P-40E, P-40N and Spitfire Vs during 1943-45 in Papua New Guinea.

The Spitfires were seen as the premier fighter - and much superior to the P-40E at altitudes above about 15,000 ft. As a result, Spitfires were generally assigned roles as interceptors and flew top cover for bombers/fighter-bombers or roaming escort for bombers.

The P-40s were more used in roles at low level intruders, including as intruders, close bomber escorts for mediums (less common for heavies), and as fighter bombers. The RAAF did a lot of fighter-bomber operations with P-40s in 1942 through 1945. There are accounts of them operating P-40Ns with four guns and payloads of 1 x 500 and 2 x 300 lb bombs, and P-40Es with as many as 6 x 250 lb or 3 x 500 lb bombs.

Somewhat counter-intuitively, the P-40s were used for standing combat air patrols more than the Spitfires (at least in 1943/1944). The P-40s were seen as too slow to get to 20,000 ft and so needed a bit of a headstart if they were to intercept Japanese bombers at 25,000 ft or above. The Spitfires were seen as a bit fragile with too few spares available to be used up on standing patrols.

The RAAF had some notable reliability problems with their Kittyhawks.

The .50s were prone to stoppages. The P-40Es had manual clearing handles in the cockpit so the problem wasn't so bad. However, the 'lightweight' P-40N deleted this feature. The RAAF official history notes that on some missions, Kittyhawks often came home with more guns jammed than working. The issues were attributed to a combination of poor gun heating (already a familiar story with the Hispanos on the RAAF's Spitfires) and the lubricating oil becoming fouled and heavy (likely by the combination of dust, humidity, salt air and the poor heating).

The P-40's electrical system did not get on well with the hot, humid, wet climate of PNG and had a tendency to fail or short out. The instruments, gunsights and lighing system, along with the hydraulics for the landing gear, flaps & trim and automatic propeller govenor on the P-40 were all driven by an electric pump (most other aircraft had a motor driven pump). On the P-40N, only the landing gear had a back-up hand pump, which meant if the electrics stopped working the aircraft would have become incredibly difficult to fly.

P-40E and some P-40Ns had fuel system quirks. The linings of the fuel tanks on P-40Es and some P-40Ns delivered to the RAAF broke down when using high octane fuel. So, lots of RAAF Kittyhawks were plauged with leaky fuel tanks after a certain amount of time.

 

[GrauGeist]

The linings of the fuel tanks on P-40Es and some P-40Ns delivered to the RAAF broke down when using high octane fuel. So, lots of RAAF Kittyhawks were plauged with leaky fuel tanks after a certain amount of time.

If the lining deteriorated, than the free material also most likely clogged the fuel filters.