P-38 Question

[Marshall_Stack]

Why is that the P-38 had so many problems in the European theater but not in the Aleutians (as far as I know). I know that the British fuel was improperly blended but is that the only reason? Does using different RPM and manifold pressure settings account for the turbochargers problems?

 

[FLYBOYJ]

Good questions and yest to be answered especially by the ETO folks. Perhaps the Aleutians were so miserable that the heater situation didn't matter to the pilots?!?

You second question is correct. There were definitely operator difference in each theater of operation and IMO is the reason why the P-38 performed so well in the Pacific and was considered sub-par (by some) in the ETO.

 

[ccheese]

I think the fuel probably played a part in it. If you recall the Italians
"killed" the P-38 they captured intact by their poor fuel. It destroyed
the engines.

Charles

 

[renrich]

I believe that the P38 was operated at higher altitudes in the ETO which exacerbated the turbo problems and they also had the problem that at higher altitudes in a dive they would get into compressibility more quichly and lose control. Even though air temps were low in the Aleutians at the altitudes the P38s operated at they were not as low as in the ETO.

 

[drgondog]

I believe that the P38 was operated at higher altitudes in the ETO which exacerbated the turbo problems and they also had the problem that at higher altitudes in a dive they would get into compressibility more quichly and lose control. Even though air temps were low in the Aleutians at the altitudes the P38s operated at they were not as low as in the ETO.

Renrich dead on

The ETO temps at 30,000 feet were frequently in the 60-70 below zero range and played havoc with the superchargers as well as unpressurized cockpits nearly freezing the pilots to death.

As you noted compressibility major problem. was just a few knots above top speed at that altitude and absent the dive brakes for the 38L it went into compressibility quickly after start of dive.

At medium altitudes the 38 was a beast in climb, turn and dive - so was well suited to MTO and PTO. 12th and 15th operated at lower altitudes in the MTO plus a lot more escort to medium bombers. Aleutians was all medium altitude also.

IMHO, if the first P-38 had not been destroyed in the crash landing after the speed run - the compressibility and turbo problems would have been discovered and fixed in time for the P-38 to be a major player in long range escort much earlier than the P-51. That stunt sent the P-38 program back two years at least (prototype with no production tooling)..

 

[Marshall_Stack]

"IMHO, if the first P-38 had not been destroyed in the crash landing after the speed run - the compressibility and turbo problems would have been discovered and fixed in time for the P-38 to be a major player in long range escort much earlier than the P-51. That stunt sent the P-38 program back two years at least (prototype with no production tooling).."



The XP-38 crashed because of carbeurator icing. I know they fixed this problem (carbeurator heater?).

Would they have needed to use the British fuel to find the problem. From what I have read, the British fuel was improperly blended and the lead would come out of suspension from the extreme cold weather and too-efficient turbocharger intercoolers.

 

[drgondog]

The report Kelsey wrote after the crash noted that he suspected Carb icing - but the combination of bad brakes, forced to land at low speed and high drag put him under the power curve - and engines didn't resond to increased throttle..he stated that 9 possibilities existed and he had eliminated five before the crash"

He noted that the problem was solved with a combination of fuel supply and carburator redesign - but I don't believe the precise root cause was determined.

Having said that, the future high altitude supercharger problems were not carburator icing but low/freezing lubrication issues mostly solved with redesign of intercooler from leading edge to radiator core-types with manual control available in cockpit.

I will check on that bold statement..

 

[SoD Stitch]

Yeah, it probably came down to the altitudes at which the aircraft was employed. Although the P-38 had turbo-supercharged engines, it actually performed better at low to medium altitudes, whereas the Merlin, with a 2-speed supercharger, performed better at higher altitudes, which is where a lot of the air combat in the ETO took place, particularly in the later stages of the War.

The P-38 also had a fairly high wing-loading compared to other single-engined fighters of the period (50 lbs.+ per square foot, versus about 30-40 lbs. per square foot); this would make it much less maneuverable at altitude, though a very stable gun platform at lower altitudes for strafing.

The reason it did so well in the Aleutians (IMHO) was due to the fact that it had exceptional range for the time period (no other fighter of the time could fly further), which was necessary considering the vast distances they had to patrol. It also had two engines, which was a considerable safety factor when most of your flying is done over the vast expanses of the North Pacific and the Bering Sea; I have no idea how many P-38's limped home to Unimak after losing an engine, but I'm sure it must've happened occasionally.

And, finally, the opposition (Japanese) aircraft tended to be inferior to the P-38; there weren't very many Zeros operating in the North Pacific, most of them were sent to the Phillipines and the South Pacific. What was left in the North Pacific were mostly flying boats and bombers, so the P-38 didn't have any real opposition.

 

[Cub Driver]

Because of the high-ranging "German 88" flak gun, bombers over Germany had to fly at higher altitudes than anywhere else in the world, at least until B-29s began operating over the home islands of Japan.

Japanese planes especially tended to fly at at medium altitudes--14,000 feet in the case of bomber formations over Rangoon in the winter of 1941-1942. That's why the P-40 was an effective fighter in the Pacific theater, months and even years after the RAF had turned it down as inadquate for the defense of England.

It seems to me that bombers, not fighters, determined the altitude at which combat took place.

My two cents (pennies, pfennig, yuan, sen) anyhow!

Blue skies! -- Dan Ford

Coming August 21: Flying Tigers: Claire Chennault and His American Volunteers, 1941-1942

 

[JoeB]

...it probably came down to the altitudes at which the aircraft was employed. Although the P-38 had turbo-supercharged engines, it actually performed better at low to medium altitudes,

...The reason it did so well in the Aleutians (IMHO) was due to the fact that it had exceptional range for the time period (no other fighter of the time could fly further)

...And, finally, the opposition (Japanese) aircraft tended to be inferior to the P-38; there weren't very many Zeros operating in the North Pacific

I agree with all those points. I'd add that there were no landplane Japanese fighters ever within range of P-38's in the Aleutians. When the Japanese invaded Kiska their occupying force included a detachment floatplane Zero's (A6M2N, 'Rufe'), that detachment and reinforcements were it for fighters. The Japanese never built operational airfields on Attu and Kiska before losing and abandoning those islands respectively. The float Zeroes actually had some successes v P-38's, but soon the Allies (including one Canadian P-40 sdn) had bases from which P-40's and P-39's could also strike Kiska, heavily outnumbering the Japanese floatplanes, and the floats also slowed a Zero down quite a bit, and the Japanese suffered their own heavy operational losses to the Aleutian weather like the Allies (in the two months from July 1942 16 Rufes lost operationally, 6 in combat including bombed/strafed on the water). So, air opposition dwindled to almost nothing long before the islands were retaken in 1943. The first P-38 claims ever were 4 August 1942 against 2 of 3 'Mavis' flying boats attacking Atka, but Japanese accounts indicate just one a/c was hit and none lost (the first P-38 kill confirmed in opposing accounts was later in August, an Fw200 off Iceland). Later on when US bases were extended further west, P-38's downed some unescorted Betty's flying all the way from the Kuriles. The situation in the Aleutians was overall just not very comparable to 8th AF operations over Germany.

Joe

 

[Marshall_Stack]

Another question somewhat related...

I have heard that at high altitude the P-47 was the queen of the sky with its turbocharger. But, I saw on TV a Tuskegee airman saying that the P-47 was only good at medium altitude, maybe up to 28,000 ft and then the P-51 was better.

Which is true?

 

[drgondog]

Another question somewhat related...

I have heard that at high altitude the P-47 was the queen of the sky with its turbocharger. But, I saw on TV a Tuskegee airman saying that the P-47 was only good at medium altitude, maybe up to 28,000 ft and then the P-51 was better.

Which is true?

The P-51/Packard Merlin 1650-7 was designed for peak speed and performance at 25,000 feet whereas the P-47D and M were targeted for peak performance at 30,000 feet.

He was wrong in the context of P-47 performance 'falling off' at 28,000 feet.

As to Better, in my opinion the Mustang was a better air superiority fighter than the P-47 or P-38 and on par with an F4U. The Mustang had far better results aginst the Luftwaffe.

 

[renrich]

What youall are saying is interesting to me because the tubocharger was supposed to give better high altitude performance at high altitudes( above 25000 feet or so) and apparently it did with the P47 but perhaps not with the P38. Somewhere on this site there was a report published which showed that in tests conducted in Australia a Spit 9 with a 2 stage supercharger had a higher Vmax at 30000 ft than a P38. The turbochargers on the P38 must not have been very effective.

 

[SoD Stitch]

What youall are saying is interesting to me because the tubocharger was supposed to give better high altitude performance at high altitudes( above 25000 feet or so) and apparently it did with the P47 but perhaps not with the P38. Somewhere on this site there was a report published which showed that in tests conducted in Australia a Spit 9 with a 2 stage supercharger had a higher Vmax at 30000 ft than a P38. The turbochargers on the P38 must not have been very effective.

I'm not an aircraft powerplant engineer, but I do know two things:

1. The turbo-superchargers on the P-38 were first-generation turbo-superchargers (we just call them turbochargers nowadays, but back then the word "turbocharger" had not been invented yet, so they were originally called exhaust-driven superchargers, as opposed to the mechanically-driven superchargers on the Merlin) developed by General Electric. GE was approached to develop them because GE had experience in building high-temp steam-driven turbines for industrial powerplants. As I said, these were first-generation turbochargers, so they probably weren't very efficient.

2. The Allison V-1710 engines were not originally designed to operate with a turbo-supercharger bolted onto them; every other application of the Allison engine up to the P-38 was in naturally-aspirated form (meaning no forced-injection of the air/fuel mixture). In fact, the P-38's that got shipped to the UK in '41 didn't have any turbochargers on them per Britain's request (dumb move). The Merlin, on the other hand, was designed from the outset to operate with a supercharger.

 

[renrich]

Thanks Stitch, good info. Makes sense.

 

[Hop]

Almost all fighter engines had a supercharger, the Allison and Merlin were no different in that respect.

What differed is that RR added a second mechanical supercharger stage, to make the 2 stage Merlin 60 series and above. The P-38 used a turbocharger as the second stage.

But both engines were designed for forced induction from the outset, and I don't know of any major application where the Allison was used without it's mechanical 1st stage supercharger.

As to the fuel, the vast majority of the aviation fuel used in Britain during the war came from the US. Neil Sterling got the following from the British archives, concerning the change in the blend of fuel being supplied by the US in 1943:

As you may know, the U.S. authorities recently decided without further reference to us, that all supplies of 130 grade would, as from August 10th, be leaded up to 5.5 cc. per Imperial gallon as compared with 4.8 cc. previously. So rapidly has this decision been implemented that there are at present two cargoes of the new base material (to be leaded in this country) on the high seas and a further three loadings for this country are anticipated very shortly.
It now transpires that the increase in lead content is likely to cause serious disturbances on a variety of American engines fitted to British machines, or American machines taken over by R.A.F. This is particularly true of heavy engines used by Costal Command and Allison engines for Fighter Command. The details are given on the attached minute by M.A.P. which was considered at a meeting today of all concerned, including the Americans.
It was assumed by the meeting that the American decision cannot have left out of account the difficulties now feared in the U.K. and that therefore the results of tests are available in U.S.A. which will point the way to the steps to be taken to overcome these obstacles. M.A.P. and Colonel Johnson are immediately telegraphing to Washington to renew requests for such information, and it has been agreed that we will defer asking the U.S. authorities to discontinue shipping the new material, until the results in particular of Colonel Johnson's telegram are received. It has been necessary to protect his position to some extent as he was a strong protagonist of the new fuel during his visit to Washington and, indeed, largely helped to push the decision through on the basis that the British agreed and that the increase in potential production was indispensable.
As regards the two cargoes which will arrive very shortly in the U.K. with the new material, it has been decided that Petroleum Board should

(a) as far as possible segregate the material

or

(b) will blend it in with old specification material I.
subject to the stipulation that the resulting lead content will not exceed 5 cc.

The carrying through of the above decision may, I fear, result in the delaying of one or other of the two tankers as they may need to be moved to a different port of discharge. It is the prime purpose of this minute to advise you of this, and I am also sending a copy to Mr. Wackcrill at Ministry of War Transport so that he should be fully informed.
The troubles are feared as much or more in the Overseas
Commands such as the ME and North Africa.

1. All British engines are cleared for this fuel;
The following table summarises the petition with American engine types :-

Wright and P W:
British Plugs - Probably OK
US Ceramic Plugs - No definite information
US Mica - No information

Allison:
British plugs - Severe fouling after 20 hours
US Ceramic - No information
US Mica - Not approved for combat ratings on 4.8

It cannot yet be said that British plugs will make all Wright Pratt Whitney engines satisfactory on 5.5 co fuel although the evidence obtained to date is encouraging. Tests are continuing,

We have no evidence to show suitability of America ceramic type plugs on 5.5 cc fuel. Tests are in progress on Double Cyclones and Double Wasps, If these tests are satisfactory, it will be assumed those plugs arc equally suitable for Cyclones and Twin Wasps,

British plugs have failed in the Allison engine in Mustang aircraft; no information is available as to the suitability of American ceramic plugs on this engine except that on 4,8 cc fuel the British plugs were not inferior to American plugs.

The position regarding the utilisation of 5,5 cc fuel by the RAF, is therefore,

a. British engines O.K.
b. Allison engines cannot use it and tests so far conducted indicate that the engine itself cannot digest 5.5 cc fuel. Considerable further test data is therefore required both on engine and plugs,
c. Wright and Pratt Whitney engines - no decision can be taken until flight tests under 3 and 4 above are completed. In view of the encouraging preliminary results on British plugs, adequate production of these types should be provided.

SO the Allison certainly had problems with the new type of fuel supplied by the US in the summer of 1943, but it's a bit unfair to blame the fuel, as the other engine types had little problem with it. I don't know how long 5.5 cc was used for 100/130 fuel, I believe later in the war less TEL was used.

 

[FLYBOYJ]

There was also a cooling problem with the rear pistons and I think it was limited to one engine. This was due to the baffling around the engines. I believe I read a paper by Hal Hibbard who stated this. maybe someone else has information on this....

 

[renrich]

Upon rereading my best reference, it as apparent that all fighter a/c in US in WW2 used supercharged engines, the simplest being a single stage one speed type which caused the critical altitude to be reached at about 15000 ft. The Allison engines in the P38 used a mechanical supercharger as well as turbo charging as has already been pointed out. A possible cause of of any reliability problems in the P38 engines was that General Motors who owned Allison was a johnny come lately in aircraft engine design and the V1710 was the first engine of theirs to be produced in any quantity.

 

[evangilder]

I have to disagree with that assessment. The V-1710 dated back to 1931 and was used in several different aircraft, including the P-40. The problem with the Allison in the P-38 was not the engine, but the venting and cooling systems used in the P-38. Look at early models versus older model P-38s. Notice the vents in the rear part of the fuselage booms. Those were opened and closed when needed. They were left closed early in the flight to allow the engine to get to proper operating temperature while climbing to the cool operating altitude. The problem with the early P-38s was without that venting, the engines were not operating at optimum temperature before reaching altitude. They were actually running too cold, which created a host of problems with the Allisons.

Here is an excerpt from an article that I wrote about the P-38:

Every Lightning in the European theater had at least one set of engines changed during it's service life. The Allisons were problematic, but the redundancy of 2 engines helped to bring back many aircraft. The problem with the Allison engines were not entirely due to the design of the engines. The cooling system that was initially installed was not adequate and the lack of cowl flaps exasperated the problem. The original intercooler system led the airflow from the turbosuperchargers to the wingtip and back, which was a less than ideal situation. Later models resolved this problem. Temperatures at high altitudes above Europe were often 40 degrees below zero, which did not allow the engines to warm properly for correct oil cooling. Additionally, at the fuel octane and lead separated at that temperature, causing valve failures and backfires that would fire through the intercooler ducts, sometimes warping the leading edge of the wing. Engine fires were also experienced due to broken connecting rods. These problems were corrected for the most part in later models with the changes made to the intercoolers and the addition of the rear ducts.

US aircraft had supercharged engines, turbocharged engines and engines with turbosuperchargers. The P-38 went through a number of designs of turbosuperchargers.

For more info on turbosuperchargers, look here:
The Turbosupercharger and the Airplane Power Plant

 

[dominiusq]

I havant read that much on this subject, however from what I have, I am lead to believe that there were many factors causing the "unhealthy attitude" toward the p-38 in europe. Compressionablity was claimed to eliminate the positive aspects of the aircraft alongside with incorrect intercoolers. However given that there was limited knowledge at the time on compressionablity (infact much that was known was a direct result of the p-38's development) and the fact that the p38 was not originally designed to generate the hp that the later models produced. I have also read somewhere that inexperianced pilots could also be blamed for the lack of success in europe. I find odd though that the problems in europe increased with the release of the p38 j model. However this model was supposed to be the model that solved the cooling problems with the core radiator beneath the engine. This was also the model that had new improved heating systems installed in the cockpit. This eliminated another theroy I heard about the pilots being extremely cold at high altitudes and therefore limiting their focus and effectiveness.

However as I am new to all this please feel free to rip apart my thread