P-38 Question

[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

[Soren]

The P-38 operated successfully in the PTO because it was loads faster than its opponents, in the ETO however it was faced with faster and more nimble single engined fighters and therefore did poorly in this theatre.

[JoeB]

Back to Aleutians, here's how small the air combat effort there was: One squadron, the 54th FS, flew the P-38E, later some G's. The official USAAF list has 15 aerial victories between August 1942 and May 1943: 2 Mavis (Type 97 Flying Boat, H6K), 6 Rufe (Type 2 Float Fighter, A6M2N, 'float Zero'), 2 Jake (Type 0 Recon Seaplane, E13A), 5 Betty (Type 1 Land Attack Plane, G4M).

The credits correlate as follows with Japanese accounts ("The Fighting Floatplanes of the Japanese Imperial Navy", Air Enthusiast 31 detailed account of Rufes in Aleutians, Japanese Monographs and USSBS interviews cover Mavis/Betty claims, no known source to verify Jake aerial claims):
Aug 4 1942: credited 2 Mavis, first P-38 credits ever. Japanese account of the Mavis detachment on Kiska details all losses and none were in air action; on one undated occasion enemy fighters attacked and damaged one Mavis, since this was only encounter recorded by US probably the same one.
Sep 13: credited 1 Rufe, 1 P-38 lost. Rufes claim 1 P-38, no loss.
Sep 14: 2 P-38's collide while fighting Rufes.
Sep 28: credited 1 Rufe, P-39's 2 Rufes, lose 1 P-39. 1 Rufe lost, 2 dam, clm 1
Oct 3: credited 1 Rufe, 1 Jake; P-39's 1 Rufe, 2 Jakes. 2 Rufes lost, Jakes?
Nov 9: claim 8 Rufes strafed on water. 6 Rufes and 3 Jakes, some dest in a storm, rest wiped out by strafing P-38's.
Dec 30: P-38's surprised by new contingent of Rufes, 2 P-38's lost.
Feb 13: credited 3 Rufes, 1 Jake. Rufes clm 1 P-38 w/o loss, Jakes?
May 23: credited 5 Betty's from Kuriles, 1 P-38 lost. 2 Betty's downed outright, 1 ditched on return, 1 'heavily damaged' on landing, claim 3 P-38's.

So, P-38's downed 1-1/3 Rufes if prorated with overlapping P-39 claim, for the loss of the 5 P-38's in combat with Rufes, 3 not counting the collision. Plus 3-4 Betty's and perhaps 2 Jakes for another P-38. 11th AF P-39's and P-40's were credited with 10 Rufes and actually downed 7-2/3 for loss of 1 P-39 to a Rufe. Small sample but still interesting advantage by the P-39/40 compared to P-38 v the Rufe.

Joe

[FLYBOYJ]

Originally Posted by JoeB

So, P-38's downed 1-1/3 Rufes if prorated with overlapping P-39 claim, for the loss of the 5 P-38's in combat with Rufes, 3 not counting the collision. Plus 3-4 Betty's and perhaps 2 Jakes for another P-38. 11th AF P-39's and P-40's were credited with 10 Rufes and actually downed 7-2/3 for loss of 1 P-39 to a Rufe. Small sample but still interesting advantage by the P-39/40 compared to P-38 v the Rufe.

Joe

Interesting information - perhaps going into combat for the first time with a twin engine fighter or just shear bad luck for the P-38 vs. the Rulfe?

[FLYBOYJ]

Originally Posted by Soren

The P-38 operated successfully in the PTO because it was loads faster than its opponents, in the ETO however it was faced with faster and more nimble single engined fighters and therefore did poorly in this theatre.

It's kill to loss ratio was a hair over 1 to 1 depending on who's numbers you want to believe (I know Joe B might chime in here). I could agree the Luftwaffe had better fighters but it surely didn't do poorly....

[Marshall_Stack]

Originally Posted by evangilder

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

Great write-up. This document states/shows that the turbocharger is superior to the two stage two speed supercharger. I wonder if this is just theory that can be offset by many real world factors.

[syscom3]

Originally Posted by Soren

The P-38 operated successfully in the PTO because it was loads faster than its opponents, in the ETO however it was faced with faster and more nimble single engined fighters and therefore did poorly in this theatre.

So no P38's ever shot down a -109 or -190?

[renrich]

Some interesting stats on P38s in Europe and I believe this includes N Africa. Sorties-129,849 Losses-1758 sorties/loss-74. This compares to 85 sorties/loss for P51s and 138sorties/loss for P47s.

[Hop]

Great write-up. This document states/shows that the turbocharger is superior to the two stage two speed supercharger. I wonder if this is just theory that can be offset by many real world factors.

The two big disadvantages of turbochargers was the loss of exhaust thrust and the size and drag associated with the turbocharger.

From a lecture by Cyrill Lovesey (head of RR Merlin development) to De Havilland in 1945, available on WWII Aircraft Performance

I should point out that before the decision was made to adopt a two-stage mechanically drive blower, full consideration was given to the application of exhaust turbos and extensive analysis was made of this project. While it was attractive in respect of giving lower specific fuel consumptions under cruising conditions it had very little advantage in maximum power performance, particularly when one considers that with a turbo system we should lose practically the whole of our ejector exhaust effect which we know to be quite
efficient at high speeds. This, of course, only holds good when we use simple ejector exhaust manifolds. The exhaust turbo system had a lot of disadvantages in respect of the installation in a fighter aircraft like the Spitfire. It came out heavier than the mechanically driven supercharger and the drag was estimated to be higher due to various cooling ducts supplied for the turbine. The system of control of the turbo blower was also a difficult one. It was quite evident that with regard to the Spitfire, which was the aeroplane under consideration at that time, the job of improving its performance could be done much better by means of a mechanically driven two-stage blower.

I believe turbos make much more sense in bombers, which tend to have more space available, and fly at lower speeds, so both the reduction in exhaust thrust and increase in weight/drag are less important than in a fighter.

[Soren]

Originally Posted by syscom3

So no P38's ever shot down a -109 or -190?

Come on Syscom3 !

Didn't the Finnish shoot down russian fighters in their Brewster Buffalo's ? Didn't F4F's shoot down A6M2 Zeke's ?

For christs sake...

[syscom3]

Originally Posted by Soren

Come on Syscom3 !

Didn't the Finnish shoot down russian fighters in their Brewster Buffalo's ? Didn't F4F's shoot down A6M2 Zeke's ?

For christs sake...

I bet it was a complete shock for the LW to start loosing fighters to those inferior P38's.