P-38 fuel endurance question

[Guppy]

In case anyone thinks that Lindbergh's technique only worked for P-38s, here's an excerpt from a 39th FS pilot's recollections. It starts after, in an idle moment, he got hold of a copy of the P-47 tech manual and started to read it:

"I turned to Hodge (Idon M. Hodge), my best buddy, and said, 'Look at this, Hodge, it says here that for maximum endurance you fly at 1400 rpm!' This seemed unbelievable to us, who had been trained to fly at 2350 rpm.

A 350-mile radius of action was about all that we could manage as a squadron. So the secret Grosshuesch/Hodge plan to reduce the rpm to less than everybody else was formulated... On two occasions, when weather was socking in and everyone was flailing around with minimum fuel, Hodge and I were real cool with skads of fuel."

(Lee Grossheusch, quoted in squadronmate Wayne Rothgeb's book "New Guinea Skies: A Fighter Pilot's View of World War II.")

[Captain Virgil Hilts]

Until Lindbergh convinced the guys in the 5th AF to do otherwise, the P-38 was flown at low (about 16-18") MAP/autorich/2600RPM. This not only caused excessive fuel consumption, but also fouled plugs. Another problem it created was that it dropped cylinder head and oil temperatures well below proper operating levels. This caused the engines to run rough and hesitate when the throttles were advanced upon entering combat. It also caused the turbos to overspeed because the oil was congealed in the turbo regulators. This was yet another area where the USAAC and Lockheed dropped the ball.

The incident that caused Lindbergh to attempt to convince the 5th AF to use his fuel method was an prettythang chewing he got from a flight leader for taking too long to clear the runway as planes running out of fuel were waiting to land.

Lindbergh told the guys in the squad he was flying with to try flying at 36"MAP/autolean/1600RPM. The mechanics went nuts, swearing the Allisons would be junk in one flight. However, Mac MacDonald, the CO, set about testing the idea out. After a few flights, they found fuel consumption was dramatically reduced, and that the engines actually ran smoother and responded much better to the throttles. The mechanics removed the engines from the plane and found they were in excellent shape, better than the engines in any other plane.

Unfortunately, this information was never adopted by the 8th AF. It would have made a big difference in many ways. They'd have had a lot more fuel to fight with (in most deep penetration escort mission profiles there was less than 5 minutes of WEP allowed if you wanted to have fuel to get home), and the problems of fouled plugs, burnt valves, dropped valves, dropped valve seats, chucked rods, ruptured intercoolers, and shattered turbos would have been nearly non existent.

The biggest drawback to using the Lindbergh settings was that it required you to do more switching  and adjusting when entering combat. You had to switch to autorich,and increase your RPM, BEFORE slamming the throttles open. Add that to having to turn on both the gunsight and the gun heaters, and having to reset the radiator and oil cooler doors, not to mention switch the fuel selectors and drop the tanks if running on external, and you get real busy real fast. If the flight leader made the call to go combat ready before you engaged, that was okay, but if you got bounced, it was touch and go.

The fuel capacity increase in the J-5-Lo and later P-38s was 110 USG. Changing the intercoolers to the core type and placing them in the fuselages instead of using the leading edges of the wings as complex intercoolers allowed the engines to make more power, and the space freed up made room for a 55 USG tank in the leading edge of each outer wing.

[chunder']

The AH P-38's fuel endurance is not affected by RPM changes, the only thing you'll accomplish by reducing your RPMs is to fly slower or reduce drag if you are gliding.  In my opinion the best cruise settings for a decent speed and longer endurance are in the 32-42" manifold pressure range.

[leitwolf]

No biggie hazed, I still love ya

Those settings are most definitely for a P-38L (with no external load). You should be able to maintain an IAS of 178 mph.

I triple checked this - the AH P-38L will not even hold 150 mph IAS. (1600rpm,25" and 15k alt). Speed gradually drops down to stall speed levels and you have a hard time maintaining altitude - always at the edge of a stall. I tested this with internal fuel only, no external loads (I even emptied all guns and burned off both aux tanks).
Anyway, even if it turns out AH might be off in this respect it's pretty much a non issue for it's typical use in the MA.
The lack of a good cruise setting to nurse your plane home, however, hurts more imho. And as it looks now your fuel is consumed "Lightning" fast even when it should not - in cruise.
A wild guess is that this is a compromise to factor in the workload to achieve low fuel consumption and that real pilots often flew with an inefficient setting to be able to react quickly. (Which is what we can in here)

[Guppy]

Originally posted by Captain Virgil Hilts
Unfortunately, this information was never adopted by the 8th AF. It would have made a big difference in many ways.

Interesting commentary from a 1st FG (MTO) pilot, who met his counterparts in the 55th (ETO) for a short period while ferrying their old P-38Hs to his unit (to replace their even older P-38F/Gs):

"The 55th had been flying P-38s for several months and were constantly getting their butts kicked. After talking with their pilots for a short time, we understood why. They were flying at power settings that guzzled fuel at an incredible rate. They were cruising at 38 to 40 inches manifold pressure and 2,600 RPM. We used that kind of power for climbing. Our cruise power was closer to 30 inches and 2,000 RPM. When we got to our target area, we would have plenty of fuel should we make contact with the enemy. They were so short of fuel that, at times, they had to desert friendly planes that were greatly outnumbered by the enemy. With drop tanks, they were running short of fuel after less than two hours of flight. They couldn’t believe we were flying missions that were more than six hours."

[flakbait]

Short answer: we have no mixture control at all, so we can't run lean of the peak exhaust temp to reduce engine temps and fuel flow. Flying the long-ass missions without running lean-of-peak impossible.


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Flakbait [Delta6]
Delta Six's Flight School
Put the P-61B in Aces High

[Captain Virgil Hilts]

Originally posted by Guppy
Interesting commentary from a 1st FG (MTO) pilot, who met his counterparts in the 55th (ETO) for a short period while ferrying their old P-38Hs to his unit (to replace their even older P-38F/Gs):

"The 55th had been flying P-38s for several months and were constantly getting their butts kicked. After talking with their pilots for a short time, we understood why. They were flying at power settings that guzzled fuel at an incredible rate. They were cruising at 38 to 40 inches manifold pressure and 2,600 RPM. We used that kind of power for climbing. Our cruise power was closer to 30 inches and 2,000 RPM. When we got to our target area, we would have plenty of fuel should we make contact with the enemy. They were so short of fuel that, at times, they had to desert friendly planes that were greatly outnumbered by the enemy. With drop tanks, they were running short of fuel after less than two hours of flight. They couldn’t believe we were flying missions that were more than six hours."

Exactly. Art (Heiden) told me that they often had less than five minutes of fuel to fight with, then they just had to run. He said he was convinced that a large number of planes that failed to return actually fought too long and simply ran their tanks dry on the way home. He said he also knew that some of the guys realized that they had used up so much fuel fighting that they'd never get home, and simply stayed in the fight until they ran their guns dry or got shot down, or both.

What's really sad is that they (the 8th AF) had guys like Jack Ilfrey who flew in North Africa and knew how to fix all the problems the 8th had with the P-38, but he was ignored by most.

The command staff of the 8th AF screwed the pooch all the way up until Doolittle took over. By then, far too many planes were lost and too many men had died. Air superiority over Germany should have been secured by mid 1943 instead of mid 1944.