P-38 vs P-51

[Ivan1GFP]

This excerpt has been posted so many times I'm surprised no one is collecting royalties. This was from the Rau memo and paints an EXTREMELY exaggerated worse case scenario. So what made this soooo different from the same P-38 driver in the PTO??? Maybe the tropical weather made them think and react faster?!?!?

Hello FlyboyJ,
Perhaps the different cruise altitudes in the PTO made for a less critical response. One thing that probably would not happen at lower altitudes is fuel falling out of suspension in the induction system.
The opposition also operated at much lower altitudes and with fewer land bases, being bounced was probably much less likely.
Tropical weather probably IS better for the pilots' reaction times than the cold encountered on a bomber escort mission in the ETO.

Wasn't the P-38's dive angle restricted because of the low Mcr and it accelerated well in a dive?

The dive flaps enabled steeper dives, but still not as steep as some of the single engine fighters.

Hello Wuzak,
In AHT, there is a mention of the dive angle without the dive flaps being restricted to about 15 degrees and to about 45 degrees with the dive flaps.

- Ivan.

 

[wuzak]

Hello FlyboyJ,Hello Wuzak,
In AHT, there is a mention of the dive angle without the dive flaps being restricted to about 15 degrees and to about 45 degrees with the dive flaps.

- Ivan.

Thanks Ivan.

I have AHT, but it just isn't available to me here at work....

 

[FLYBOYJ]

Hello FlyboyJ,
Perhaps the different cruise altitudes in the PTO made for a less critical response. One thing that probably would not happen at lower altitudes is fuel falling out of suspension in the induction system.

No Ivan - the process is the same and you're guessing about fuel in the induction system. The issues addressed in the Rau report involved the pilot's ability to configure their aircraft to address a combat situation

The opposition also operated at much lower altitudes and with fewer land bases, being bounced was probably much less likely.
Tropical weather probably IS better for the pilots' reaction times than the cold encountered on a bomber escort mission in the ETO.

Again you're guessing. If anything flying at a lower altitude gives you less options for evasive action. A frigid cockpit with layers of clothing vs. a sweltering cockpit with pilots sometimes flying in shorts, I'll give you that. Bottom line, by Rau's own admission, there were inadequately trained pilots flying the P-38 in the ETO at the time his report was written.

 

[michael rauls]

Hello Michael Rauls,
The placarded limits were 440 MPH @ 30,000 feet and 460 MPH @ 20,000 feet which corresponds to Mach 0.65 (from AHT).
Beyond that, there is gradual loss of control which sounds like a serious tactical limitation.
Is it a useful thing to be able to beat someone in a race to the ground and not have enough control to bring guns to bear?
I suppose it is useful if one is trying to escape.
My original point was really that the dive speed limitation really didn't get fixed at all. The dive speed limitation was there before and remained in place. With the dive recovery flaps, there was just a means of avoiding becoming a lawn dart.

- Ivan.

The point I was trying to make and perhaps I didn't articulate it clearly was that once the threat of " lawn dart" was removed with advent of dive brakes one was in effect simply left with a plane that could do 470 mph( mach .68) in a dive at 25,000 feet. Certainly not as fast as many but
really not that shabby.
I guess it depends on what one means by" solved" when referring to compresability.
Did it still put a cap on the p38s dive speed? Yes but alot of ww2 planes if not most were starting to run into various troubles in the high 400s/ low 500s.
In other words compresability being a problem on dive flap equipped p38s( most of them) simply meant it had a mediocre dive speed. Nothing more.
Of course it had alot of strengths like great climb to make up for it. No plane is great at everything.

 

[Ivan1GFP]

No Ivan - the process is the same and you're guessing about fuel in the induction system. The issues addressed in the Rau report involved the pilot's ability to configure their aircraft to address a combat situation

Again you're guessing. If anything flying at a lower altitude gives you less options for evasive action. A frigid cockpit with layers of clothing vs. a sweltering cockpit with pilots sometimes flying in shorts, I'll give you that. Bottom line, by Rau's own admission, there were inadequately trained pilots flying the P-38 in the ETO at the time his report was written.

Hello FlyboyJ,
The issue with fuel falling out of suspension with low manifold pressure and cold temperature is not a guess. I believe I still have the Airpower magazine it came from though I can't lay hands on it right now so I can't quote directly from it. That particular issue dates to the late 1970's.
As for the rest of the issue being mostly one of lack of training, there is no argument that that is what Rau's memo states.

- Ivan.

 

[FLYBOYJ]

Hello FlyboyJ,
The issue with fuel falling out of suspension with low manifold pressure and cold temperature is not a guess. I believe I still have the Airpower magazine it came from though I can't lay hands on it right now so I can't quote directly from it. That particular issue dates to the late 1970's.

But did it have anything to do with Rau's report? Can you quantify this to the poor performance of the P-38 during the period the Rau report was written?

I think there's overwhelming historical evidence that the P-38's poor ETO performance was mainly due to poor pilot training. Sure there were other issues, but this seems to be the cornerstone of the problem, again by Rau's own admittance. The article I posted shows the full context of Rau's report but it seems that many P-38 detractors mainly point to his criticism of the P-38 cockpit configuration.

Which brings up another point - more than likely the AAC actually dictated the cockpit configuration of the P-38 or accepted it's configuration during design acceptance. It seems that Rau (or his boss) missed this point.

 

[Ivan1GFP]

But did it have anything to do with Rau's report? Can you quantify this to the poor performance of the P-38 during the period the Rau report was written?

Hello FlyboyJ,
The contrast of ETO versus PTO performance and Tropical climates was not something *I* brought up. Since you brought it up to suggest that there was no difference in operating environment, I thought I would point out that there actually WERE some important differences such a Altitude / Temperature and Fuel supplies.

I think there's overwhelming historical evidence that the P-38's poor ETO performance was mainly due to poor pilot training. Sure there were other issues, but this seems to be the cornerstone of the problem, again by Rau's own admittance. The article I posted shows the full context of Rau's report but it seems that many P-38 detractors mainly point to his criticism of the P-38 cockpit configuration.

Which brings up another point - more than likely the AAC actually dictated the cockpit configuration of the P-38 or accepted it's configuration during design acceptance. It seems that Rau (or his boss) missed this point.

I actually don't count myself as a P-38 detractor. Every aircraft has its good points and its weaknesses. The P-38 is no exception.
Its role as a high altitude bomber escort was not the original mission it was designed for and it showed.
The P-38 like many of its contemporaries (such as the A6M as a notable example) had the engine performance to reach a fairly high operational ceiling. The problem was that although they could get up there, they were not intended to operate there for any length of time. On an intercept mission the power settings are fairly high and there isn't the issue of fuel falling out of suspension in a very long and cold intake system or TEL separating from the fuel in the intake manifold or not being able to maintain proper oil temperatures.
Keeping the pilot warm for hours on a long escort mission also wasn't considered.

I won't argue that the biggest issue was pilot training because even in Rau's memo, he qualifies his "average" pilot as only having about 25 hours experience.

- Ivan.

 

[bobbysocks]

And this human interface is overcome with TRAINING. 8 switches vs 6??? Sorry Tomo, this is a non-issue. If it's that mentally challenging for a pilot to activate a few extra switches, they shouldn't be flying airplanes!

in the heat of the moment when the opportunity to bounce an EA suddenly happens, brainfarts abound. at some point or another most of the pilots I talked to had that "Oh $#!T" moment when they dropped their tanks only to have their engines crap out because they forgot to switch tanks. Robin Olds jokingly claims he is the only known pilot to shot down an EA while gliding....cos it happened to him. other pilots have forgot to turn on guns/gun heaters, drop their tanks and other things.

 

[Shortround6]

Hello FlyboyJ,
The issue with fuel falling out of suspension with low manifold pressure and cold temperature is not a guess. I believe I still have the Airpower magazine it came from though I can't lay hands on it right now so I can't quote directly from it. That particular issue dates to the late 1970's.
As for the rest of the issue being mostly one of lack of training, there is no argument that that is what Rau's memo states.

- Ivan.

The issue was known before the fuel in question and engines made it into operational service. The trouble was compounded by a change in the formulation of 100/130 fuel that allowed a higher percentage of "heavy aromatic " compounds to be used to blend the fuel this allowed for higher production from the same tonnage of base stocks (crude or simple refined fuel) )
please note that not all refineries used the same amounts of these compounds and the actual amounts might vary from production to production batch at the same refinery. It was a juggling act to balance the amount/cost of the additives against the cost/supply of the suitable base stocks (first run refining?)

The short passageways of the airflow from the supercharger to the cylinders in the air cooled engines were much less of a problem. Allison designed a new intake manifold to help re-atomize the fuel called the madam queen manifold. By Dec of 1944 this manifold was being fitted to ALL new Allison engines regardless of supercharger type or intended airframe. Hundreds if not thousands were supplied ro retrofit.

going back to poor training, Allison and Lockheed both recommended cruising at low rpm and high boost even before this fuel blend problem came along but what did they know compared to the USAAF officers

The TEL separating out of the fuel may be a myth. The heavy aromatics had a higher anti knock rating than any straight run gas which is why they were used. They were also used because there was limit on how much TEL per gallon could be used. 4.6 CCs per US gallon. They were using a whole lot more heavy aromatics per gallon.
SO yes, you did have anti-knock compounds seperating out, wither it was TEL or how much TEL was separating out are different questions. Unfortunately some writers don't seem to know about any other anti-knock compounds than TEL.

 

[Ivan1GFP]

Hello Shortround6,
Thanks for the additional information.

It seems like the early P-38 would have had the worst situation because of very long routing for the "intercooler" in the leading edge of the wing. With no real heat exchanger, the volume would have to be pretty large.

The description I was reading about additives separating in the intake manifold mentioned that separated TEL was causing some plugs to foul but other plugs were not fouling. This doesn't sound like something that would be happening with separation of aromatics.

- Ivan.

 

[FLYBOYJ]

Hello FlyboyJ,
The contrast of ETO versus PTO performance and Tropical climates was not something *I* brought up. Since you brought it up to suggest that there was no difference in operating environment, I thought I would point out that there actually WERE some important differences such a Altitude / Temperature and Fuel supplies.

Differences in operating environment, absolutely, no difference in "operating." Sorry If I didn't make myself clear.

I actually don't count myself as a P-38 detractor. Every aircraft has its good points and its weaknesses. The P-38 is no exception.
Its role as a high altitude bomber escort was not the original mission it was designed for and it showed.
The P-38 like many of its contemporaries (such as the A6M as a notable example) had the engine performance to reach a fairly high operational ceiling. The problem was that although they could get up there, they were not intended to operate there for any length of time. On an intercept mission the power settings are fairly high and there isn't the issue of fuel falling out of suspension in a very long and cold intake system or TEL separating from the fuel in the intake manifold or not being able to maintain proper oil temperatures.
Keeping the pilot warm for hours on a long escort mission also wasn't considered.

I won't argue that the biggest issue was pilot training because even in Rau's memo, he qualifies his "average" pilot as only having about 25 hours experience.

- Ivan.

I think we're in general agreement

 

[FLYBOYJ]

in the heat of the moment when the opportunity to bounce an EA suddenly happens, brainfarts abound. at some point or another most of the pilots I talked to had that "Oh $#!T" moment when they dropped their tanks only to have their engines crap out because they forgot to switch tanks. Robin Olds jokingly claims he is the only known pilot to shot down an EA while gliding....cos it happened to him. other pilots have forgot to turn on guns/gun heaters, drop their tanks and other things.

I think that happened (or could happen) in any aircraft/ any era. The only way to mitigate is through training

 

[P-39 Expert]

The P-38 couldn't dive and the P-47 couldn't climb. Neither turned well. Both were enormously expensive. In hindsight, both should have had a shorter production run, if any. Just my opinion. Doesn't make me a commie or anti-P-38 or P-47.

 

[tomo pauk]

The P-38 couldn't dive and the P-47 couldn't climb. Neither turned well. Both were enormously expensive. In hindsight, both should have had a shorter production run, if any. Just my opinion. Doesn't make me a commie or anti-P-38 or P-47.

It was unfortunate that all of the three best US Army fighters have had a rocky start - XP-38 crash and YP-38 running late, the XP-47B mirroring Hawker Typhoon problems very much, and Army's disinterest with (X)P-51 that almost saw no P-51s for the AAF.
US goverment was very much willing to pay the bill if the piece of gear works, and P-38 and P-47 worked. There was a cure for P-38 compressibility problems (suggested by NACA), installing combat-worth drop tanks on P-47 was specified by AAF almost too late, and AAF being a bit more warmed up for XP-51 would've seen AAF P-51s already for North Africa. Rectifying just two of the above woud've spelled doom for LW already in 1943.

 

[Shortround6]

The P-38 couldn't dive and the P-47 couldn't climb. Neither turned well. Both were enormously expensive. In hindsight, both should have had a shorter production run, if any. Just my opinion. Doesn't make me a commie or anti-P-38 or P-47.

Somebody might want to tell that to some test pilots. With the big prop and water injection a P-47 could outclimb a FW 190 at low altitude (lets not even mention high)
the dividing line for turning seemed to be 250mph, below that the FW 190 could out turn the P-47, above that it couldn't .

Of course neither the P-39 or P-40 could do what the P-38 and P-47 could do even if they weren't quite as good as the P-51.

 

[wuzak]

Hello Shortround6,
Thanks for the additional information.

It seems like the early P-38 would have had the worst situation because of very long routing for the "intercooler" in the leading edge of the wing. With no real heat exchanger, the volume would have to be pretty large.

The description I was reading about additives separating in the intake manifold mentioned that separated TEL was causing some plugs to foul but other plugs were not fouling. This doesn't sound like something that would be happening with separation of aromatics.

- Ivan.

I believe that the fuel falling out of suspension happened on P-38 versions with the core type intercooler. ie the P-38J and P-38L.

The leading edge intercoolers on earlier versions restricted the power available because they didn't cool the air sufficiently,so it is unlikely that these were the versions that had the fuel falling out of suspension.

 

[wuzak]

Its role as a high altitude bomber escort was not the original mission it was designed for and it showed.

Was there any WW2 fighter designed as a high altitude long range bomber escort that saw extensive production?

 

[GreenKnight121]

Plenty of strong points on both machines, but also some important 'negatives', especially for P-38. Also, plenty of missed opportunities.

P-51: quick development cycle, good performance even on modest power, excellent performance on good power, almost no 'issues', apart from faulty HMG installantion and, sometimes, not having a positive lock of U/C cover (remedied in winter of 1943/44), long/very long range. Lack of hi-alt performance until Merlin was installed; no drop tank facility early on. Reasonable firepower, if light per UK/Germans standards sometimes.

You forgot a few very important and deadly issues with the P-51.

1. On early models (B/Cs), ammunition doors & landing gear doors sometimes opened under high-gee conditions (frequently during high-speed dives) - this often then overstressed the wings, with several aircraft losing a wing and crashing (witnessed by other pilots). This was eventually resolved. You mentioned this in passing without mentioning its deadly effect. There was at least one P-51B lost to this in April 1944*, so not completely solved as per your date.

2. Starting with late-production P-51Bs, a 322-liter (85 US gallon) tank that fit between the pilot's seat and the radio. The new tank gave the Mustang the necessary range, solving one problem, if at the expense of creating another. The new fuel tank was added without concern for its effect on the Mustang's center of gravity. With a full fuel load, getting the fighter off the runway was downright dangerous (a number of pilots lost control on takeoff, crashing on the runway or shortly after, when they tried to climb too steeply and the aircraft's tail dropped too low and it stalled at low altitude), and the aircraft was only marginally controllable for the first hour or so that it took to drain the tank. Ultimately, the USAAF was forced to limit the amount of fuel pumped into the fuselage tank to 246 liters (65 US gallons).

3. The P-51 (especially -Ds) were touchy - it had high stick forces under combat maneuvers. Worst of all, under such maneuvers it gave no warning of stall and could fly abruptly and wildly out of control (even after fitting the "fillet" at the front of the vertical stabilizer to lessen its yaw instability). However, it seems that regaining control wasn't hard - if you weren't being shot at at the time.

4. One that was less-deadly was the frequent jamming of the wing .50mgs in the -A/B models when fired during high-turns - the guns were canted over on their sides, and the ammunition belts would jam. This was not fully fixed until the guns were re-aligned in the -D (with a power belt feed added in later -D production) - the guns were set vertically, which not only straightened the feed path, but also allowed 3 guns per wing instead of 2. You did mention this, but again without noting how serious it could be to be without working guns in the middle of a fight.


* Tommy Hitchcock, who had done much to promote the Merlin Mustang, was killed over England in a P-51B in this way in April 1944.

 

[MiTasol]

Kind of funny though - if you look at a P-51 cockpit at the center pedestal there is a fuel selector valve. Look at a P-38 right side below the throttle - same valves, except there's TWO!!!

Somewhat over simplified to say the least.

My only memory of working in the cockpit of a P-38 (F-5B) was a rh windscreen change in 1972 and it is not a happy memory. I found the cockpit very cramped (I weighed around 150lb at the time) and the large control spectacle and its mast got in the way all the !@#$% time.

I could not remember where the fuel selectors were in the cockpit so had to check the -1 manual.

The location on the floor below the window winder, radio controls, cockpit lights and in the narrow slot beside and below the seat it does not look at all user friendly to me. I do remember the selectors were connected to the valves by cables and pulleys and that arrangement usually makes the valve a lot stiffer to operate. So my guess is that the P-38 fuel controls were not that user friendly given the tight cockpit, especially if you had to contort your body to reach them.

Seeing that the later P-38 aircraft starting at J-15 had a totally different (much taller) handle that was easier to grab and provided more leverage I would say that my guess is right on the mark.

Having a multiple of fuel configurations to remember if not flying the same aircraft all the time was conducive to errors as well.

Having to reduce power when changing off drop tanks while you are being shot at is also not what I would call "user friendly".

The P-51 fuel selector on the other hand is in an easy to access position and the valve is directly connected to the handle by a shaft so there is nothing in the system to increase the torque the pilot must apply to turn the valve from detent to detent.

 

[MiTasol]

The only way to mitigate is through training

And the application of what is now called ergonimics to make fuel selectors easy to operate etc and by putting all the controls used during take-off and landing in close proximity - unlike the Brits and the P-38 (where that !#$ obtrusive handle that was such a pain when changing the RH windscreen was the flap lever).