XP-39 II - The Groundhog Day Thread

[GregP]

Hi P-39 Expert, let me try once here.

I am a volunteer at the Planes of Fame Museum in Chino, CA. We have a P-39 (static) and Fighter Rebuilders is located onsite, owned by Steve Hinton and son. They have built up a P-39 on at least one if not more occasions and I have looked pretty closely at the static P-39. None of what I am saying here is from Fighter Rebuilders or the Museum, it is my observations only. I mention the above only so you know that WWII fighters are very much present there all the time, not just on occasion. They operate WWII fighters VERY regularly, even several times per week ... that is ... pre-COVID anyway.

There isn't a lot you can remove from a P-39 that is not structural or in the wrong place, CG-wise, for removal. If you remove the nose guns, I assume you remove the ammunition, too. You have to do something to keep in CG. If you remove the nose guns, except the cannon, the ammunition, and the nose armor plate, the airplane WILL be lighter, but you can't fly it since the CG is out of limit aft. There is NOTHING heavy in the tail cone except maybe the radio, and nobody was going to let their radio be deleted. They might need it to communicate where they ditched in the ocean, if for nothing else. It wasn't going to "go away" without the pilots rebelling.

So, I fully support your contention that lightening the P-39 would have been a good thing. I'm just having a hard time trying to decide WHAT to delete that would make a difference while remaining flyable and maintaining combat effectiveness. See the image below.

The cutaway below is an early P-39 and had 30-cal guns, but later variants had 50-cal guns. I'll assume 50-cals.

The only thing I see that is removable behind the center of gravity, which is about 1/3 of the way back from the wing leading edge, is the radio receiver (#12 above), and it ain't going anywhere. The pilot's back armor is #28 above, and is about right on the CG (18.2 pounds). Most pilots would not remove it even though the engine is a pretty good armor by itself. You might remove the #74 wing guns (145 pounds) and #79 ammunition (186 pounds), but what else can you suggest that would effect a significant weight change aft of the CG? I may be blind, but I don't see it. There is no significant structure to get rid of.

If you DO remove the wing guns, you are lighter by 331 pounds but you also have only a cannon that jams easily and has few rounds anyway and two 50-cal nose guns. This ain't no German MG 151/20, it's an Oldsmobile jamming fool and, if it DOES jam, you are down to two 50-cal MG ... just mildly better than what a P-26 Peashooter had. I'd rather leave the armament, operate the engine beyond recommended limits for better performance, and play fighter below 12,000 - 15,000 feet.

You might only remove ONE gun (the outer one) and ammunition in each wing, and you'd save 165 pounds or so. But, is that going to make your airplane a noticeably-better fighter in a dogfight against your likely opponent? I think not. It might climb marginally better, but not enough to catch a Zero by LONG shot. The Zero had more than a little better climb rate at P-39 combat altitudes.

Kick me if you can see it differently, but all the structure behind the wing trailing edge seems necessary for flight and structural integrity to me.

I'd not remove the #17 oil tank armor for any reason whatsoever.

 

[Ivan1GFP]

There is no "best power" label but the mixture control can be adjusted between the settings.

You have said absolutely NOTHING with that statement. The process is the important part and what I and everyone else is telling you is that it is not something that can be done when maneuvering as in combat. With the constantly changing conditions of engine load, altitude, speed, how can the pilot decide whether the mixture needs to be leaner or richer? By the time he has observed and decided, the conditions have most likely changed.

Please stop telling me what I have read and what I haven't read. Keep the personal attacks to yourself.

This is not an attack but a simple statement of fact. You either did not read the note at the bottom of the report that I directed you to or you did not understand what you were reading.

That's the only Zero available to test. It was restored to the best available condition.

Hmmm..... You are contradicting your next statement below......
Just because it was the only aircraft available to test and that it was restored as well as the captors knew how doesn't mean that it was representative of the ones the enemy was currently using. Many if not most cases of captured aircraft tests are that way.
Another good example that came up in discussion recently was the La 5FN tested at Rechlin. Good for a handling evaluation, but worthless for a performance evaluation.

Other A6M2s were tested and the vast majority topped out at 330mph.

Great Assertion! Now please back up your claim and provide your source for other A6M2 in good running order that were tested.
Test reports would be a good start.

Like overboosting the engine on takeoff? Risking engine damage or failure? What did takeoff run matter in these tests? More likely a novice pilot in an unfamiliar airplane.

The fellow was probably trying beat the A6M2 in a time to height race by any means that he could.
I suspect this pilot was quite experienced. Over revving the engine and running boost up past 70 inches Hg at low altitude was something that had been done with some P-40s with similar model engines in combat conditions.
It got to be bad enough that Allison wrote a memo about it.

I saw a documentary on TV once and the veteran surviving Japanese pilot said the top speed of the Zero was 308mph.

First question I should ask you since you actually saw the documentary is WHAT did the Japanese pilot actually say?
Was he speaking Japanese or English? If Japanese, did he have a translator?

Keep in mind that the Air Speed Indicator on the A6M series reads in Knots.
Saburo Sakai's statement about 345 MPH wasn't actually that but the equivalent in Knots.
Richard Dunn did the conversion and I have been using the number in MPH because outside of Naval Aviation, MPH was the more common unit used in aviation until the 1960's.

If he was saying 308 Knots, it sounds about right for a late model A6M5 at altitude.
If he really meant 308 MPH, it sounds pretty reasonable for a A6M5's maximum speed at Sea Level.

Who is the client? The AAF? Or the combat pilots? Who wouldn't want a faster climbing airplane? At the expense of four .30caMGs?
.....
According to which operators? The Russians certainly didn't agree.
.....
My only premise is that weight affects climb, all other things being equal. In other words if a plane is made lighter it will climb better, and the improvement in climb can be quantified by the amount of weight removed. Can you argue with that?

The client is the organization that is paying the bills.
.....
The operators, Boyd Wagner et al. stated that they wanted more armour.

The Russians were great believers in all central armament and very lightly armed fighters. The US were not.
To say that the Russians liked something and used an aircraft effectively so the US Army should do the same is not a good argument because the two nations did not operate their aircraft in the same way.
The Russians were quite satisfied with wearing out aircraft and engines quickly because the lifespan of their aircraft was measured in weeks.
.....
As you have been told MANY times, the real problem is keeping "all things equal". You have been told your "formula" doesn't work, WHY it doesn't work, been given a better formula (which still makes a few assumptions that nothing else is changing), and yet you stick with a formula that doesn't follow aerodynamic principles.

Here is an example of how your argument of weight reduction falls apart. Let's take the P-39F. It is pretty much the same as a P-39D but always had 37 mm cannon. Weight is no different. Flies about like any other early P-39 with a V-1710-35.

Now let's start reducing weight for ONE objective: to make it climb!
First remove the Cannon. There goes 240 pounds.
Next goes the ammunition for 60 pounds more.
Get rid of the Cowl MG for about 160 pounds.
No need for 120 pounds of .50 cal ammunition if the nose guns are not there.
Remove the 96 pound Gear Box armour.

Aircraft is now 676 pounds lighter and should seriously climb!
What do you think will REALLY happen?

- Ivan.

 

[Stig1207]

Show me a list of vetted kills. The only ones I know of are the USAAF Report 85 and Naval Aviation Combat Statistics - World War II, and people fight over those.

Even then they are not vetted against enemy losses, just in case someone should misunderstand.

 

[buffnut453]

So, I fully support your contention that lightening the P-39 would have been a good thing. I'm just having a hard time trying to decide WHAT to delete that would make a difference while remaining flyable and maintaining combat effectiveness.

And that's the nub of my comments pages ago that the USAAF operational users didn't remove weight from their P-39s, at least not the nose armour or the wing guns, which were the main items P39Expert was proposing to remove.

If the operational users couldn't identify such "obvious" changes, perhaps the operational benefits didn't outweigh (pun intentional) the risks?

Clearly, Wagner wanted the wing guns and, as you observe, MORE armour, not less. However, those points simply get ignored in this thread.

It seems we're expected to trust test reports but ignore operational users (including Wagner himself). I can tell you from experience that such an approach is a recipe for disaster but, since it doesn't fit the narrative that P39Expert is pushing, it gets ignored.

 

[XBe02Drvr]

I do wonder if the P-39 was originally designed to the lighter British standards, how would it have performed.

Suppose we take the P39 away from Larry Bell and give it to Reg Mitchell for a quick makeover, a la P51H? Rational weight distribution, a positive G airfoil, British stress standards, and a Merlin engine: the stuff of dreams!

 

[XBe02Drvr]

Keep in mind that the Air Speed Indicator on the A6M series reads in Knots.
Saburo Sakai's statement about 345 MPH wasn't actually that but the equivalent in Knots.

1 knot = 1.15 MPH. Sakai's 345 MPH comes out to 300 knots. "Surviving Veteran" (probably Harada) gives 308, which, if it is actually knots, (makes sense from the gauge) comes out to 354 MPH, more in keeping with what US combat pilots estimated. Makes a dent in that "40 MPH advantage".

 

[Peter Gunn]

P-39 Expert - I don't mean to pick on you but the statement:

"More likely a novice pilot in an unfamiliar airplane. "

Does not make sense to me. When flight testing ANY aircraft, they generally don't use novice pilots that don't know their airplane. Those are the kinds of statements you really should shy away from.

In fact, to me, it sounds like a rather highly proficient pilot that knows his airplane and is trying his best to come out on top, possibly even was told to try it by his superiors. Remember, they had to try to figure out the best way to get the better of the enemy plane.

 

[Ivan1GFP]

1 knot = 1.15 MPH. Sakai's 345 MPH comes out to 300 knots. "Surviving Veteran" (probably Harada) gives 308, which, if it is actually knots, (makes sense from the gauge) comes out to 354 MPH, more in keeping with what US combat pilots estimated. Makes a dent in that "40 MPH advantage".

Hello XBe02Drvr,

Despite the accusations from P-39 Expert, I don't believe the A6M2 was a particularly fast aircraft.
I believe 345 MPH is credible. I don't believe 354 MPH is credible for the A6M2.

For that matter, I don't even believe EVERY A6M2 was capable of that speed.
If you go back to the Japanese Wikipedia page, you will see that Nakajima continued to build the A6M2 long after Mitsubishi had switched to the A6M3.
The Nakajima aircraft had some "improvements". They were often equipped with the longer barreled Type 99-II long barrel 20 mm cannon and 100 round ammunition drums. Some of them even had a sheet of armour plate behind the pilot and a fire extinguishing system IIRC. These were mostly "Baku-Sen" or Bomber Fighters and carried bomb racks as well.
With that combination of changes, I don't believe they were quite as fast as earlier A6M2.

I believe that the reason that US combat pilots were estimated speed a bit higher than the A6M2 might have been capable of is that as shown in the testing of the Aleutian A6M2, it had a very good zoom climb and if it gained a little speed in a dive, it would retain it much longer than one might expect.

Pinning down the actual maximum speed for Japanese aircraft tends to be pretty difficult in general. They never seemed to care enough to test for maximum speeds in a manner comparable to Allied aircraft.

My OPINION based on a lot of reading and trying to fit things together in a way that makes sense is this:
The A6M3 series was only about 5 MPH faster than the A6M2 and probably even less than that.
The problem was that the engine wasn't really that much more powerful as shown by a Military rating that was only 30 HP higher. The advantage was that it was 5000 feet higher.
This was combined with an airframe that probably had a bit more drag even though it looked more sleek. The cowl was a bit bigger and there were often exposed cannon barrels in the wings and bigger bulges for the drums for the cannon.
I believe the TAIC numbers for the A6M5 at 351 MPH to 358 MPH are most probably correct and perhaps a touch generous on the high end.
The cowl is slightly different on the A6M5 but I don't believe that really makes any difference. I believe the biggest difference was a switch to ejector stacks for the engine.
This more or less fits with the "Japanese Veteran" if he was reading the gauge in Knots.

- Ivan.

 

[XBe02Drvr]

I believe that the reason that US combat pilots were estimated speed a bit higher than the A6M2 might have been capable of is that as shown in the testing of the Aleutian A6M2, it had a very good zoom climb and if it gained a little speed in a dive, it would retain it much longer than one might expect.

Good point! Guess it's time to pull out Reardon and re-read him. Thanks, Ivan!

 

[P-39 Expert]

Hi P-39 Expert, let me try once here.

I am a volunteer at the Planes of Fame Museum in Chino, CA. We have a P-39 (static) and Fighter Rebuilders is located onsite, owned by Steve Hinton and son. They have built up a P-39 on at least one if not more occasions and I have looked pretty closely at the static P-39. None of what I am saying here is from Fighter Rebuilders or the Museum, it is my observations only. I mention the above only so you know that WWII fighters are very much present there all the time, not just on occasion. They operate WWII fighters VERY regularly, even several times per week ... that is ... pre-COVID anyway.

There isn't a lot you can remove from a P-39 that is not structural or in the wrong place, CG-wise, for removal. If you remove the nose guns, I assume you remove the ammunition, too. You have to do something to keep in CG. If you remove the nose guns, except the cannon, the ammunition, and the nose armor plate, the airplane WILL be lighter, but you can't fly it since the CG is out of limit aft. There is NOTHING heavy in the tail cone except maybe the radio, and nobody was going to let their radio be deleted. They might need it to communicate where they ditched in the ocean, if for nothing else. It wasn't going to "go away" without the pilots rebelling.

So, I fully support your contention that lightening the P-39 would have been a good thing. I'm just having a hard time trying to decide WHAT to delete that would make a difference while remaining flyable and maintaining combat effectiveness. See the image below.

The cutaway below is an early P-39 and had 30-cal guns, but later variants had 50-cal guns. I'll assume 50-cals.




View attachment 600127

The only thing I see that is removable behind the center of gravity, which is about 1/3 of the way back from the wing leading edge, is the radio receiver (#12 above), and it ain't going anywhere. The pilot's back armor is #28 above, and is about right on the CG (18.2 pounds). Most pilots would not remove it even though the engine is a pretty good armor by itself. You might remove the #74 wing guns (145 pounds) and #79 ammunition (186 pounds), but what else can you suggest that would effect a significant weight change aft of the CG? I may be blind, but I don't see it. There is no significant structure to get rid of.

If you DO remove the wing guns, you are lighter by 331 pounds but you also have only a cannon that jams easily and has few rounds anyway and two 50-cal nose guns. This ain't no German MG 151/20, it's an Oldsmobile jamming fool and, if it DOES jam, you are down to two 50-cal MG ... just mildly better than what a P-26 Peashooter had. I'd rather leave the armament, operate the engine beyond recommended limits for better performance, and play fighter below 12,000 - 15,000 feet.

You might only remove ONE gun (the outer one) and ammunition in each wing, and you'd save 165 pounds or so. But, is that going to make your airplane a noticeably-better fighter in a dogfight against your likely opponent? I think not. It might climb marginally better, but not enough to catch a Zero by LONG shot. The Zero had more than a little better climb rate at P-39 combat altitudes.

Kick me if you can see it differently, but all the structure behind the wing trailing edge seems necessary for flight and structural integrity to me.

I'd not remove the #17 oil tank armor for any reason whatsoever.

Sorry for the confusion. Never advocated removing any guns in the nose. Don't understand where you got that.

Remove the wing .30calMGs, their ammunition, mounts heaters and chargers like the Russians did. They were ineffective anyway, especially with a 37mm cannon and two .50s.

Remove the nose armor plate and any armor on the oxygen bottles. No other planes armored the nose reduction gear or the oxygen bottles. Move the radio (#12) up over the engine right behind the turnover bulkhead to restore balance. Lots of P-39 photos show a radio in this position. That's all I have ever advocated removing. Save about 300lbs, increase climb about 360fpm.

 

[glennasher]

"
Now let's start reducing weight for ONE objective: to make it climb!
First remove the Cannon. There goes 240 pounds.
Next goes the ammunition for 60 pounds more.
Get rid of the Cowl MG for about 160 pounds.
No need for 120 pounds of .50 cal ammunition if the nose guns are not there.
Remove the 96 pound Gear Box armour.

Aircraft is now 676 pounds lighter and should seriously climb!
What do you think will REALLY happen?

- Ivan. "

Well, since it doesn't have any guns (except in the wings), it pretty much forfeits it's whole reason for existing, which was as an interceptor, right?

 

[buffnut453]

Remove the wing .30calMGs, their ammunition, mounts heaters and chargers like the Russians did. They were ineffective anyway, especially with a 37mm cannon and two .50s..

The wing .30 cals were ineffective? According to who?

YET AGAIN...Buzz Wagner didn't want them removed. Clearly HE thought they weren't ineffective. But let's not get the operational pilot's combat experience get in the way, right?

 

[P-39 Expert]

You have said absolutely NOTHING with that statement. The process is the important part and what I and everyone else is telling you is that it is not something that can be done when maneuvering as in combat. With the constantly changing conditions of engine load, altitude, speed, how can the pilot decide whether the mixture needs to be leaner or richer? By the time he has observed and decided, the conditions have most likely changed.

Don't need to adjust the mixture in combat. Simply push the throttle forward, move the propeller control to 3000rpm, and adjust the mixture control one time. All set for combat. Much easier than on a P-38.

This is not an attack but a simple statement of fact. You either did not read the note at the bottom of the report that I directed you to or you did not understand what you were reading.

Please don't concern yourself with what I have read and what I haven't. I understand what I read very well. Don't worry about me at all.

Hmmm..... You are contradicting your next statement below......
Just because it was the only aircraft available to test and that it was restored as well as the captors knew how doesn't mean that it was representative of the ones the enemy was currently using. Many if not most cases of captured aircraft tests are that way.
Another good example that came up in discussion recently was the La 5FN tested at Rechlin. Good for a handling evaluation, but worthless for a performance evaluation.

It was the only plane we had at the time. Why wouldn't it be representative of other planes of the same model?

Great Assertion! Now please back up your claim and provide your source for other A6M2 in good running order that were tested.
Test reports would be a good start.

I'm not going to list all the test reports that I have seen that show the top speed of the A6M2 to be 330mph or less. Most all of them show 330mph or less.

The fellow was probably trying beat the A6M2 in a time to height race by any means that he could.
I suspect this pilot was quite experienced. Over revving the engine and running boost up past 70 inches Hg at low altitude was something that had been done with some P-40s with similar model engines in combat conditions.
It got to be bad enough that Allison wrote a memo about it.

The P-39D-1 did not yet have an automatic boost control. I suspect the pilot was new to this model or he would know not to overboost the engine on takeoff risking damage or engine failure. It was a test, not a race.

First question I should ask you since you actually saw the documentary is WHAT did the Japanese pilot actually say?
Was he speaking Japanese or English? If Japanese, did he have a translator?

He spoke English. I remember thinking that was a lot lower than I had seen quoted.

Keep in mind that the Air Speed Indicator on the A6M series reads in Knots.
Saburo Sakai's statement about 345 MPH wasn't actually that but the equivalent in Knots.
Richard Dunn did the conversion and I have been using the number in MPH because outside of Naval Aviation, MPH was the more common unit used in aviation until the 1960's.

If he was saying 308 Knots, it sounds about right for a late model A6M5 at altitude.
If he really meant 308 MPH, it sounds pretty reasonable for a A6M5's maximum speed at Sea Level.

Clearly he said 308mph.

The client is the organization that is paying the bills.
.....
The operators, Boyd Wagner et al. stated that they wanted more armour. He asked for that piece or armor plate behind the oil tank, which was added to the P-39.

The Russians were great believers in all central armament and very lightly armed fighters. The US were not. The Russians had engines that would accomodate a nose cannon firing through the propeller. The US did not. If you believe wing armament to be superior to nose armament, then why didn't later jets have guns out on the wings?
To say that the Russians liked something and used an aircraft effectively so the US Army should do the same is not a good argument because the two nations did not operate their aircraft in the same way. The AAF would have been wise to reduce the weight of the P-39 to improve climb and ceiling like the Russians did.
The Russians were quite satisfied with wearing out aircraft and engines quickly because the lifespan of their aircraft was measured in weeks. That has nothing to do with this discussion.
.....
As you have been told MANY times, the real problem is keeping "all things equal". You have been told your "formula" doesn't work, WHY it doesn't work, been given a better formula (which still makes a few assumptions that nothing else is changing), and yet you stick with a formula that doesn't follow aerodynamic principles. There is absolutely nothing aerodynamic about reducing the weight of a particular model airplane to improve climb and ceiling. The aerodynamics were the same. Only difference was the weight. When 836lbs extra internal weight was added to the P-39D the climb rate went down by 1000fpm. There is no argument to that statement.

Here is an example of how your argument of weight reduction falls apart. Let's take the P-39F. It is pretty much the same as a P-39D but always had 37 mm cannon. Weight is no different. Flies about like any other early P-39 with a V-1710-35. P-39D always had the 37mm. D-1 and P-400 switched to the 20mm. D-2 switched back to the 37mm for all subsequent models.

Now let's start reducing weight for ONE objective: to make it climb!
First remove the Cannon. There goes 240 pounds.
Next goes the ammunition for 60 pounds more.
Get rid of the Cowl MG for about 160 pounds.
No need for 120 pounds of .50 cal ammunition if the nose guns are not there.
Remove the 96 pound Gear Box armour. I have never advocated removing any of the nose armament. Only removing the wing .30s and the nose armor and restore balance by moving the radio in the tail up to above the engine right behind the turnover bulkhead.

Aircraft is now 676 pounds lighter and should seriously climb!
What do you think will REALLY happen? The tail would be sitting on the ground and the nose would be pointed up in the air. Takeoff or flight would be impossible.

- Ivan.

 

[P-39 Expert]

P-39 Expert - I don't mean to pick on you but the statement:

"More likely a novice pilot in an unfamiliar airplane. "

Does not make sense to me. When flight testing ANY aircraft, they generally don't use novice pilots that don't know their airplane. Those are the kinds of statements you really should shy away from.

In fact, to me, it sounds like a rather highly proficient pilot that knows his airplane and is trying his best to come out on top, possibly even was told to try it by his superiors. Remember, they had to try to figure out the best way to get the better of the enemy plane.

A highly proficient pilot would not overboost his engine causing detonation in any situation. He was risking engine damage or failure. And he would know that the D-1 did not have an automatic boost control meaning he could not firewall the throttle on takeoff, but must use the manifold pressure gauge to not exceed the maximum takeoff boost.

 

[GregP]

It won't increase the climb by that amount. Covered that already.

I mentioned the nose guns just to address all the guns. The nose guns need to stay there for CG. If you have a later P-39 and the wing guns are 50s, I'd rather have them than another 75 - 150 fpm of climb. No way I'd move a tube radio above a running engine. The tubes make enough heat on their own and moving a spark ignition closer a radio than it HAS to be is not smart!

 

[Ivan1GFP]

Don't need to adjust the mixture in combat. Simply push the throttle forward, move the propeller control to 3000rpm, and adjust the mixture control one time. All set for combat. Much easier than on a P-38.

You just described setting the mixture control to Auto Rich which is what we have been trying to tell you was the correct approach all this time.
In case you forgot, you were advocating using manual mixture controls to tune for best power in combat.....

It was the only plane we had at the time. Why wouldn't it be representative of other planes of the same model?
.....
I'm not going to list all the test reports that I have seen that show the top speed of the A6M2 to be 330mph or less. Most all of them show 330mph or less.

Because it was not in the same condition as ones in service or operated the same way.
.....
Listing just ONE test report for PROOF would be good. Without the proof, this is just Hearsay and not deemed to be not even as reliable as a "Hangar Story".

He spoke English. I remember thinking that was a lot lower than I had seen quoted.
Clearly he said 308mph.

Did he give the conditions?
Context is important.

He asked for that piece or armor plate behind the oil tank, which was added to the P-39.

For Boyd Wagner to ask for a piece of armour to be installed in the P-39 when it ALREADY came as STANDARD would have been interesting. You do know that the Oil Tank armour came as standard on every production Airacobra after the P-39C, right?

The Russians had engines that would accomodate a nose cannon firing through the propeller. The US did not. If you believe wing armament to be superior to nose armament, then why didn't later jets have guns out on the wings?

The Russian philosophy was simply different, and no, many of their engines did not allow a gun firing through the propeller.
Radial engines have a bunch of things in the middle which get in the way of a gun.
Jets are a whole different story. You can start a different discussion if you want to go there.

There is absolutely nothing aerodynamic about reducing the weight of a particular model airplane to improve climb and ceiling. The aerodynamics were the same. Only difference was the weight. When 836lbs extra internal weight was added to the P-39D the climb rate went down by 1000fpm. There is no argument to that statement.

You have yet to prove the aerodynamics are EXACTLY the same. Many knowledgeable people have been trying to convince you of that.

A highly proficient pilot would not overboost his engine causing detonation in any situation. He was risking engine damage or failure. And he would know that the D-1 did not have an automatic boost control meaning he could not firewall the throttle on takeoff, but must use the manifold pressure gauge to not exceed the maximum takeoff boost.

Many highly proficient pilots did indeed over boost their engines staying below the limits for detonation. This was documented with the P-40 models using the V-1710-39 which was similar to the -35 engine in the P-39D-1 and when using V-1710-73 engines similar to the P-39's -63 engines.
Have you ever seen the Allison memo on the subject?

- Ivan.

 

[XBe02Drvr]

Move the radio (#12) up over the engine right behind the turnover bulkhead to restore balance.

Do you know why the radio is way back in the tailcone? It's to get it as far as possible away from the vibration, heat, and ignition interference from the engine. You're proposing to put it "right in the lion's den". Same reason they didn't put it in the only other logical place, up in the nose by the guns. I've never been up close and personal with an Oldsmobile 37MM cannon, but I have with 20MM and .50 cal, and I can tell you it's an earth shaking experience. Have you ever disassembled an old fashioned vacuum tube radio? Even "ruggedized" for airborne use their tolerance for vibration and heat is pretty limited. One of the failures of the Zero was the inability of its voice radio to cope with the (supposedly shielded) electronic noise from the engine.

A highly proficient pilot would not overboost his engine causing detonation in any situation. He was risking engine damage or failure.

Did it ever occur to you that that boost limit could be an arbitrary number with considerable safety margin built in, set by conservative engineers wary of the exuberance of testosterone driven young pilots? And that the pilot selected for the test might be proficient enough and knowledgeable enough to realize he could shave those margins a bit without too much risk, considering he may have been under pressure not to let the Zero show him up too badly? Your faith in the incorruptibility of pilots is touching.

 

[P-39 Expert]

The wing .30 cals were ineffective? According to who?

YET AGAIN...Buzz Wagner didn't want them removed. Clearly HE thought they weren't ineffective. But let's not get the operational pilot's combat experience get in the way, right?

Wagner actually said that the pilots preferred the .50s to the less effective .30s. And he said that the .30s were less reliable than the .50s. He may not have advocated their removal, but he clearly said they were less effective and less reliable. Remember he said all this about two weeks after their first combat.

 

[P-39 Expert]

It won't increase the climb by that amount. Covered that already.

I mentioned the nose guns just to address all the guns. The nose guns need to stay there for CG. If you have a later P-39 and the wing guns are 50s, I'd rather have them than another 75 - 150 fpm of climb. No way I'd move a tube radio above a running engine. The tubes make enough heat on their own and moving a spark ignition closer a radio than it HAS to be is not smart!

Lots of photos of radios in that exact spot. Just because you don't agree with the climb numbers doesn't mean they are wrong.

 

[buffnut453]

Wagner actually said that the pilots preferred the .50s to the less effective .30s. And he said that the .30s were less reliable than the .50s. He may not have advocated their removal, but he clearly said they were less effective and less reliable. Remember he said all this about two weeks after their first combat.

And "less effective" is not the same as "ineffective". You're inserting your own interpretation and passing it off as fact.

YET AGAIN you keep banging on about Wagner's report being after 2 weeks of combat. However, the P-39s remained in combat for MONTHS. Did they remove the "useless" 30 cals at any time? NO. Other than "I don't know", you don't have an answer for why that might be.

I'd really appreciate it if you'd stop hitting the reset button and acknowledge that the operational crews maybe...just maybe...had a clue about what they were doing and kept the 30 cals because, despite being "less effective" they were still deemed mission critical for the sorties flown over PNG and Guadalcanal.