Interesting reading about P-38s (long)

[Mister Fork]

Rumors of my demise were greatly exaggerated. Cancer did not get me.

Glad you're better Hilts

[drgondog]

Well, here is the flight test in July 1944 to evaluate 44-1 at 3000/70"MP.

http://www.wwiiaircraftperformance.org/p-38/p-38-28392.html

Top Speed = 419mph at 19.8K, at limit speed 26,800 RPM for Turbo. 3000RPM @70" MP.

At critical alttude of 24K top speed was 413mph at 60"MP

The primary advatage was a higher rate of climb  with a corresponding trade off of a.)  lower speed at escort altitudes, b.) lower ceiling and c.) lower critical altitude.

There NEVER was a 20-25mph increase in top speed for the jump between 130 and 150 octane. Additionally the usual 10-15mph boost of top speeds (17mph in above report) came with a corresponding lower critical altitude. The issue for the P-38 was the turbo limits.  Note also that the P-38J-15 for this test was flown in clean (no wing pylons) condition - as most P-38 tests were flown compared to P-51 testing, where most, including the associated 44-1 flight tests were flwn with racks - a 12mph drag penalty but inclusive of all ETO/MTO escort conditions.

Also - the 'potential horsepower available' for each succeeding model was never the issue - it was always the intercooler and turbo issues - not to mention the poor quality 'leaking' ducting design which seems to be mentioned in nearly every P-38 flight test I have seen when 'issues' are discused. Life followed art as that was a constant maintenance write up in ETO

[drgondog]

Another bump of this ancient thread, but since you guys speak of the 479th I thought it would be interesting to mention that the 479th P38s likely operated with 150 octane fuel. This would have allowed them to use 65-75 inches manifold over the standard 60 inches, giving the P38 a 20-25mph speed boost at max power.

They were operating at 70"MP from July forward in ETO, IIRC 9th AF didn't switch until November-December. There was no increase of 20-25mph as the turbo rpm was the limiting factor - not to mention the drag rise due to lower Mcrit of the P-38


From the page below, the 479th operated at Station 377 Wattisham, England from 15 May 1944 - 23 November 1945. They converted from P38s to P51s in the time period between October-December 1944.
 
The 479th first 'mixed bag' meeting was escort on disastrous Sept 27 Kassel mission where 445th was clobbered. Olds was on that mission and called to testify at the investigaion board afterwards. 

Now in the second document, you see 150 octane fuel deliveries starting June 10th, 1944 to Station 377 (Wattisham), at least 4 months before their conversion to P51s began. Meaning they probably had 4-6 month operating time with P38s while being supplied with 150 octane fuel.

Quibbling but ~ 3 1/2 mo. The transition began in early September, first combat with mix was either Sept 26th or 27th.

Anyways yeah I just thought this was interesting, since many people believe P38s were only tested for 150 octane use and never used in combat with it.

All three (P-38, P-47, P-51) were cleared in April 1944 by Materiel Command, all three were operational in ETO (8thAF at 3" below MC authorization in late June 1944.
 

VIII Air Technical Services lowered the US fight test ceiling for permissible 5 minute limit (continuous) boost for 150 octane fuel.

[fd ski]

i remember reading somewhere that cost of p38 in terms of build as well as maintenance was prohibitive when compared with P51. For all it's advantages, cost did not justify them.

 

[Brooke]

The P-51 was excellent in terms of cost/performance.  It was one of the less-expensive US fighters.

Fighter costs in 1944 (Air Technical Service Command, Budget and Fiscal Office, http://www.au.af.mil/au/afhra/aafsd/aafsd_pdf/t082.pdf):

P-38, $97,000
P-47, $86,000
P-51, $52,000
P-39, $51,000
P-40, $45,000

From America's Hundred Thousand, by Dean, p. 520 (1944 F4U-1D):

F4U, $75,000

Supposedly from A History of the United States Air Force 1907-1957, Alfred Goldberg, editor or from Victory Roll, by William Wolf:

F6F, $63,000
FM2, $50,000

[Captain Virgil Hilts]

Well, here is the flight test in July 1944 to evaluate 44-1 at 3000/70"MP.

http://www.wwiiaircraftperformance.org/p-38/p-38-28392.html

Top Speed = 419mph at 19.8K, at limit speed 26,800 RPM for Turbo. 3000RPM @70" MP.

At critical alttude of 24K top speed was 413mph at 60"MP

The primary advatage was a higher rate of climb  with a corresponding trade off of a.)  lower speed at escort altitudes, b.) lower ceiling and c.) lower critical altitude.

There NEVER was a 20-25mph increase in top speed for the jump between 130 and 150 octane. Additionally the usual 10-15mph boost of top speeds (17mph in above report) came with a corresponding lower critical altitude. The issue for the P-38 was the turbo limits.  Note also that the P-38J-15 for this test was flown in clean (no wing pylons) condition - as most P-38 tests were flown compared to P-51 testing, where most, including the associated 44-1 flight tests were flwn with racks - a 12mph drag penalty but inclusive of all ETO/MTO escort conditions.

Also - the 'potential horsepower available' for each succeeding model was never the issue - it was always the intercooler and turbo issues - not to mention the poor quality 'leaking' ducting design which seems to be mentioned in nearly every P-38 flight test I have seen when 'issues' are discused. Life followed art as that was a constant maintenance write up in ETO

False. The chin mounted intercooler resolved the issues with performance due to boost limits. The turbocharger RPM limit was never raised, but the critical altitude incurred was still over 26,000 feet. None of the tested listed the performance at WEP, a noticeable error. The P-38J and P-38L had considerably more HP, and only slightly more drag incurred by the chin mounted intercooler. To expect a 15-25 MPH reduction in top speed, with a 250-450 horsepower increase is absurd, even given the low efficiency of the Curtiss props.Even comparing the P-38J to the P-38L, there are claims of a slower speed for the P-38L, in spite of a 100-150 horsepower increase, per engine. There was no substantial weight difference, it was under 200#, which is not significant for performance.

[Randy1]

the 440mph is probably a typo.
I've only seen max speed of 414mph TAS quoted.

keep in mind that the LW was fighting the P-38 at high altitudes where the lightnings allison engines and superchargers produced more power when functioning properly than the merlin engined and LW a/c. it ate the 190 up and gave the 109 nightmares.

but great stuff.
the only real maneuvering/dogfighting disadvantage of the real p38's was the low critical mach.

 .  . .theres only a few things I still hope for on the AH P-38L:



2. dive flaps ability to pitch the nose up 10-15 degrees at low speed. this does not happen in AH. c. .  . .

This is several years old but thought I might correct this thought on the L's dive flap.
 
The Dive flap was used to break laminar flow on the bottom side of the wing when high speed air during a dive, and body configuration distributed laminar flow on top of the wing.  When this happened, the wing went from a pure lifting force to a downward force.  The point being the dive flap did not lift the nose.  The dive flap simply made the bottom of the wing airflow disrupted worse than the top of the wing.   It would have no ability to lift the nose in low speed as well.  The dive flap  may have however disturb the airflow over the elevator at slow speed  giving the horizontal stabilizer a bit of a downward force thus lifting the nose.   That I do not know.

[Mongoose]

This is several years old but thought I might correct this thought on the L's dive flap.
 

This is a wonderful video tour of the P-38.  At 4:05, there is a quick shot of the dive flaps being deployed.

https://www.youtube.com/watch?v=smydUC9ssaI

[Captain Virgil Hilts]

This is several years old but thought I might correct this thought on the L's dive flap.
 
The Dive flap was used to break laminar flow on the bottom side of the wing when high speed air during a dive, and body configuration distributed laminar flow on top of the wing.  When this happened, the wing went from a pure lifting force to a downward force.  The point being the dive flap did not lift the nose.  The dive flap simply made the bottom of the wing airflow disrupted worse than the top of the wing.   It would have no ability to lift the nose in low speed as well.  The dive flap  may have however disturb the airflow over the elevator at slow speed  giving the horizontal stabilizer a bit of a downward force thus lifting the nose.   That I do not know.

Actually, according to Kelly Johnson, designer, Tony LeVier, chief test pilot, and a half dozen P-38 pilots I knew personally, the dive flaps DO induce a "pitch up" as an intentional function of the design. And the tail was redesigned to cause the plane to naturally pitch up with the elevator in the "neutral" position, to help it naturally recover from a dive. So much so that an additional reinforcement was added to allow the tail to withstand the additional force.

The dive flap was introduced as a factory installation on the P-38J-25-Lo, the final version of the "J" model. The boosted ailerons were on the P-38J-20-Lo. Both would have actually been on all J models in the theater, as part of the "Blackjack" program, were it not for the infamous "friendly fire incident".