P-38l

[TeeDog]

I've been doing some research on the P-38 and I found that the early P-38 had a problems with high speeds above 375 mph. But when the P-38L came out, it could dived to speeds in excess of 500mph. The reason for it was it had Hydraulic ailerons and Dive brakes.

Now AH has the P-38L in the game, and it can handle speeds greater then 375mph, but no way can you dive close to 500mph. It seems it might be alittle off.

P-38L Diving V-Max Speeds
15,000ft to 10,000ft 390mph
15,000ft to 5,000ft 495mph
10,000ft to 5,000ft 410mph
10,000ft to 1,000ft 500mph
5,000ft to 1,000ft 395mph

[OIO]

The AH 38L can dive to 510mph. It will never ever ever ever break the 510 mph, no matter if you dive from 48k with WEP on 90 degree dive.

[F4UDOA]

TeeDog,

The pilots hand book on the P-38L shows a 10,000FT dive restriction of 420MPH IAS which is 460TAS.

It says with the use of dive flaps do not exceed the limits by more than 20MPH.

I have this manual in electronic copy. I'll see if I can post the pages.

[OLtos]

It topped out at just over 510 for the same reason in compressed earlier than later model planes.  Drag.  As for the diver breaks, always remember they weren't really able to slow the plane down.  They just slowed down how FAST you accelerated going downhill.  The other effet was to shange the shape of the airflow around the wing at a critical point.  I don't understand all of it, but apparently it worked really well.

But, the compression thing in Aces High is not really that big a deal.  Just dial in some nose up trim and you'll pull out just fine.  Compression is not modeled to anywhere near its actual nightmareish fury.  Mos pilots did not survive a dive into full compression.  The wing stalls and the nose tucks under and you wind up disintegrating in a negative G outside loop at 500 MPH plus.  None of that will happen to you in Aces High.

[Captain Virgil Hilts]

The reason the P-38 suffered from compression was the shape of the wing. It was a thick high aspect ratio wing chosen for its ability to hold large fuel tanks and to give a very high climb rate. However the thickness and profile cause air to be accelerated to speeds in excess of the speed of sound at true ground speeds above 470 MPH, but the speed at which compression begins is varied by altitude and atmospheric conditions.

Early on, the fillets where the center wings join the cockpit nacelle did not have a large generous radius. This was changed in the early combat ready models.

The dive flaps (they were most certainly NOT brakes) had two functions. The first was to alter the shape of the wings and slow the speed of the air flowing over them down. The second was to provide a nose up pitch to counteract "mach tuck", the tendency for a plane to tuck its nose down when entering compression.

Kelly Johnson repeatedly requested time in the NACA wind tunnel in order to alter the shape of the wing slightly and test other modifications to raise the threshold of compression. However, NACA feared the high speeds Johnson needed to run would damage the wind tunnel, and Johnson's request was denied. Johnson was loathe to test the effects in the real world without first doing tests in the tunnel since one test pilot was killed during early testing (Johnson heard the crash as it happened from his office, said he'd never forget that sound).

P-38 ace and test pilot John Lowell said that you could avoid compression by doing a series of slow smooth barrel rolls while diving. He was able to dive the pre J model P-38's from altitudes of well over 28K feet this way repeatedly.

P-38 pilots I know say they had ZERO trouble with compression once the dive flaps were in use. They also say that below 20K, you could dive all you wanted and not compress.

Levier, Meyer, and Mattern (test pilots) all dove the P-38 in compression tests at speeds reportedly well in excess of 500 MPH (reportedly to around 550MPH). There were instances of the tail booms bending, and some sheetmetal panels coming off, but reported that the P-38 was quite safe in a dive provided common sense was applied.

[HoHun]

Hi Hilts,

>However the thickness and profile cause air to be accelerated to speeds in excess of the speed of sound at true ground speeds above 470 MPH, but the speed at which compression begins is varied by altitude and atmospheric conditions.

470 mph equals Mach 0.65 - the P-38's critical Mach number - at about 15000 ft. Above that, 470 mph means even higher Mach numbers.

>P-38 ace and test pilot John Lowell said that you could avoid compression by doing a series of slow smooth barrel rolls while diving.

Which means that he kept the dive slow, which is of limited tactical value.

>P-38 pilots I know say they had ZERO trouble with compression once the dive flaps were in use.

Obviously, this must have been because the dive flaps enabled them to avoid regions of the envelope where they would have encountered big trouble even with the dive flaps. Critical Mach number was raised to 0.685 by those, which still leaves the red lantern with the P-38.

>They also say that below 20K, you could dive all you wanted and not compress.

At 15000 ft, an indicated airspeed of 450 mph equals Mach 0.785 - a speed a P-51, a Spitfire, a Me 109 or a Fw 190 can handle, but far more than you could survive in a P-38.

>Levier, Meyer, and Mattern (test pilots) all dove the P-38 in compression tests at speeds reportedly well in excess of 500 MPH (reportedly to around 550MPH).

Speeds reports like these are generally the result of airspeed indication errors. The P-38 was one of the first fighters equipped with a Mach meter for testing to eliminate these errors, so meaningful test results for the P-38 will probably be stated in Mach numbers.

For comparison: 550 mph TAS at 15000 ft equal Mach 0.76, clearly out of reach for the P-38.

Regars,

Henning (HoHun)

[Captain Virgil Hilts]

Believe whatever you will Hohun, you've followed me around for over 3 years arguing with me. I'm not going to waste time arguing with you. I know what I was told by highly decorated pilots who haven't the slightest reason to lie. Whatever you choose to believe is fine with me.

Have a nice day.

[HoHun]

Hi Hilts,

>Believe whatever you will Hohun, you've followed me around for over 3 years arguing with me.

I've not "followed you around for over 3 years arguing with you", I've just used some of the same public message boards as you to add my 2 cents to yours on a few occassions.

>I know what I was told by highly decorated pilots who haven't the slightest reason to lie. Whatever you choose to believe is fine with me.

It's not what "I choose to believe", but what the documented facts are. Kelly Johnson himself counted the low limiting Mach number towards the main disadvantages of the P-38. Do you want to call him a liar, too? :-)

(If you lack the background to understand the difference between providing precise technical information and calling someone a liar, you should at least try to become aware of that.)

Let me clarify: I'm convinced that your highly decorated pilots told the truth about having "ZERO trouble with compression" - simply because they avoided fast dives. It was the smart thing to do. It just doesn't tell you anything about how fast the P-38 could go in a dive.

You provided fuzzy statements, I provided the context that's necessary to draw the correct conclusions about these statements.

You choose to play the "honour of the veterans" card? Fine with me, just try and point out where I'm contradicting the veterans.

If you shrink away from that - well, lame bluff then.

Regards,

Henning (HoHun)

[Flyboy]

in AH the p38 DOES lock at high speeds around 500mph (TAS)

allso at around 400+ there is a long lag from the move of the stick to the start of the roll itself although the roll is very fast

anyone care to explain?

[Angus]

The honor of the veterans is hard not to step on, when the veterans don't all agree.....

[Captain Virgil Hilts]

Hohun, you have flat out stated on multiple occaisions
that the fight that Galland and Lowell described at
the "Gathering of Eagles" never occured. Now, Joe Foss published it in his book "Top Gun", Gabby Gabreski, John Lowell,
and Adolph Galland all acknowleded it was true. But that is not good enough for you. Now, they were there, they said it happened, you say it didn't. Are you calling them liars, idiots, morons, or senile?

The difference between talking about technical issues and saying that four decorated veterans are lying about something they say happened (they were there and you were not) is pretty clear to me.

No, the pilots I spoke with didn't say they did slow dives, they said they pushed over and followed their enemy right on down. After getting the P-38's with dive flaps. And below 20K before dive flaps.

I never said that the P-38 did not have a dive weakness, and you'll never be able to make an honest quote of me saying such, especially regarding the early models. I did say it was not nearly the issue everyone seems to make of it. No, I'm not calling Kelly Johnson a liar either. I'll leave the calling of people who flew planes in combat or designed them liars to you, you seem to have it down pat.

No one ever said you had to go 500+ MPH in a dive in combat to be effective anyway. After the first turn in air to air combat in piston engine prop fighters you aren't going that fast anyway.

I stick by my statement that Art, Stan and others said they could push over at 25K in a P-38 and follow a 109 or a 190 without problem, they were there, they said they did it, and no one else who was there has said otherwise. They said compression was not an issue below 20K in combat, I'll have to take their word, I wasn't there. Why lie? They never said "I pushed over at 450MPH and followed a German in a 600 MPH terminal dive". They said "Several times a 109 or a 190 would split S and I would drop my speed boards and follow him right on down".

You will never believe it, nothing I or anyone else says will make you believe it. So for pilots who were there and say they did do it, they must be stupid, fools, or liars. Most of them had at least 1000 hours of flying time, did in excess of 60 missions (many over 100), so if they said "I was on the tail of a 109 and he rolled over, pulled a split S, and I followed him down from 25K and shot him up" I figure they know what they are talking about. If you don't, that's fine. I have better things to do than argue with you every time someone makes a post about a P-38 and you cannot deal with the fact that it was a superior aircraft and not the cripple you wish to believe it was. I'd say a 4-6:1 kill ratio over enemy aircraft says all that needs saying.

have a nice day.

[HoHun]

Hi Hilts,

>Hohun, you have flat out stated on multiple occaisions
that the fight that Galland and Lowell described at
the "Gathering of Eagles" never occured.

That's not even on topic in this thread :-) And where's the quote, anyway?

>I never said that the P-38 did not have a dive weakness

You seem to be highly sensitive to others saying just that, though.

>They said compression was not an issue below 20K in combat, I'll have to take their word, I wasn't there.

Do you have their word that they exceeded Mach 0.75? If you have, then it's a case of HoHun vs. The Veterans. If not, it's just a case of HoHun vs. Hilts.

>I have better things to do than argue with you every time someone makes a post about a P-38 and you cannot deal with the fact that it was a superior aircraft and not the cripple you wish to believe it was.

Hilts, the low Mach limit of the P-38 is a fact. It's not even Mach 0.75, but I'm allowing for a generous margin of error.

Do you mean to suggest the low Mach limit didn't exist? You'd be pretty lonely defending that position.

Do you mean to suggest that a low Mach limit wasn't significant in combat?

Then you should have no issue with me pointing out that the P-38 was inferior in that regard to every other WW2 fighter for which I've ever seen a Mach limit stated.

So what's your point? :-)

Regards,

Henning (HoHun)

[F4UDOA]

The P-38L dive limit chart from the POH.

http://home.comcast.net/~markw4/p38dive.pdf

For comparison the FW190A5 from the Navy test. The chart was posted in the cockpit.

[HoHun]

Hi F4UDOA,

Thanks for the great information! :-)

The revised P-38 dive placard (figure 25A) gives the following limits, converted to Mach numbers:

30000 ft: Mach 0.65
20000 ft: Mach 0.65
10000 ft: Mach 0.63

If you correlate the IAS and TAS values provided by figure 25A, you can verify that the airspeed indicator gives errenously high readings as I pointed out above. That effect was not unique to the P-38 and was normal for all airspeed indicators of the period.

The Fw 190 values are uncorrected and not directly comparable as they'd have to be adjusted down somewhat, but at least they give a general impression:

25000 ft: Mach 0.77
16400 ft: Mach 0.76
10000 ft: Mach 0.74

Regards,

Henning (HoHun)

[F4UDOA]

HoHun,

Indeed the CAS chart shows a large gap in the IAS to TAS.

At 350MPH it reads 17MPH to high and 12 MPH to high at 300MPH.

I will post it too. I have an electronic copy of the P-38L manual.

No time right now.