Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (1 Viewer)

GrauGeist · Mar 13, 2019

I should have also added was it a static test? If so, was the cannon elevated or at ground level?
If it was from a P-39 in a simulated attack, what was the closing speed, altitude at the start of the attack and how many times was the test done in order to create an average?

I am fully aware that there is an optimum angle for an attacking aircraft to use to fully exploit the projectile's ability to defeat certain armor.
But in combat, perfect angles are not always easy to achieve. Example: tank on the move across broken terrain versus a tank moving along a road. How high is the attacking aircraft when the tank is spotted, is the tank's rear presented or is it safe to go around in order to make an attack run before ground fire starts up?

Obviously, only megastar combat sim champs can hurl a cannon shell into the center of a engine vent (or a proton torpedo into a thermal vent the size of a Womp rat) but in reality, not every pass is going to offer the perfect formula for success.

MIflyer · Mar 14, 2019

Remember that initially the P-51B was designated the P-78. And you could make a good argument for the A-36 to have a P-51 designation and the B-50 to be a B-29 model. While the F-84F as produced had very little in common with the straight winged F-84 models.

As for the 37MM tests they must have been shooting at the front of the tank, in a static test. Rudel was careful to aim at the top or the rear engine cover but most people are happy to hit it anywhere.

Shortround6 · Mar 14, 2019

GrauGeist said:
I should have also added was it a static test? If so, was the cannon elevated or at ground level?
If it was from a P-39 in a simulated attack, what was the closing speed, altitude at the start of the attack and how many times was the test done in order to create an average?

I am fully aware that there is an optimum angle for an attacking aircraft to use to fully exploit the projectile's ability to defeat certain armor.
But in combat, perfect angles are not always easy to achieve. Example: tank on the move across broken terrain versus a tank moving along a road. How high is the attacking aircraft when the tank is spotted, is the tank's rear presented or is it safe to go around in order to make an attack run before ground fire starts up?

By the time the P-39 shows up in North Africa the British had been shooting at German tanks for well over a year with ground guns. They had a pretty good idea how thick the German armor was on the MK III and MK IV tanks and that was pretty much 30mm on the turret sides and rear and 30mm on the hull sides. The Front of the tanks was 30mm an the very oldest models (few left in service at this time?) with 50 mm being much more common on both and some MK IIIs had 60mm on the hull front (a 30mm layer added to the base 30mm) and some of the MK IIIs had thicker armor on the hull rear. When you get to the long barreled MK IIIs some had an extra 20mm plate spaced off the base 50mm turret front or drivers plate but stll had 30mm turret sides and rear and 30mm hull sides.
This was all well known from shooting at them (and capturing wrecks) with 2pdr AT guns, 25pdrs and assorted other guns.
Just like the US 37mm the British had a couple of different 2pdrs. The 2pdr ground AT gun (and tank gun) used a much bigger cartridge case to hold more powder and had a much higher velocity than the 2pdr AA gun which was the source of the ammo for the 2pdr Vickers S gun used in Hurricanes.

British had been using the cartridge on the right in the M3 Stuart tanks (and turret of the M3 grant), it should NOT take extensive, carefully conducted tests to figure out that the cartridge 2nd from the left is NOT going to go through armor that the one on the right won't go through at similar distances, even with 300-450 fps added to the ground velocity.

Likewise comparing the British 2pdr Vickers S gun and the American 37mm M4 used in the Airacobra should have clued people in that the American 37mm was NOT going to go through any where near as much armor without bothering with all sorts of firing trials/tests conducted by flying planes. Weight of shot, velocity of the shot and size of the hole you are trying to make. The two guns are not in same league.

It always helps to have a good margin of surplus gun power to make up for firing from less than ideal distances or angles even on the thinner parts of tanks. The 37mm M4 gun was only going to work under the most favorable of conditions it at all.

MIflyer · Mar 14, 2019

Despite the deletion of the turbo the USAAF was NOT focused on using the P-39 for ground attack, as some have claimed. The engine was set up for max speed at about 15K ft. Contrast that with the A-36A, which was set up for max speed at 5000 ft.

Thus the 37MM gun in the P-39 was designed for use in air-to-air combat. It was effective against some ground targets; one pilot reported it did a nice job on German barges in the Med. But tanks? No. VW beetles? Sure!

One of the really inexplicable things was that when the RAF fired the P-39's 37MM gun on the ground it always jammed after the first shot. They figured out that the extractor lever was too long, cut it down and then it worked Okay. Why the USAAF would have an airplane with that kind of design defect is unknown. Maybe it needed the airflow to eject the shells?

Glider · Mar 14, 2019

MIflyer said:
Despite the deletion of the turbo the USAAF was NOT focused on using the P-39 for ground attack, as some have claimed. The engine was set up for max speed at about 15K ft. Contrast that with the A-36A, which was set up for max speed at 5000 ft.

Thus the 37MM gun in the P-39 was designed for use in air-to-air combat. It was effective against some ground targets; one pilot reported it did a nice job on German barges in the Med. But tanks? No. VW beetles? Sure!

One of the really inexplicable things was that when the RAF fired the P-39's 37MM gun on the ground it always jammed after the first shot. They figured out that the extractor lever was too long, cut it down and then it worked Okay. Why the USAAF would have an airplane with that kind of design defect is unknown. Maybe it needed the airflow to eject the shells?

There were a number of defects in the P39 which should have been identified well before they reached the RAF. Unfortunately this was quite common in other aircraft such as the early B17's.

Peter Gunn · Mar 14, 2019

drgondog said:
IIRC, the P-51H shared zero assemblies with the P-51D/K, was longer, thrust line different, wing different, empennage different, lower cooling system cowl different , scoop design different, ~13 common parts (brackets, switches, plates), tires smaller, tall tail, wing area greater, airfoil different, plan form of wing different -easier to maintain, faster, climbed better, higher ceiling - but the name remained Mustang.

Good to know I haven't lost ALL my marbles, was worried there for a while.

Also, the H was as beautiful as any of the breed, an excellent standard bearer to carry the name.

P-39 Expert · Mar 14, 2019

wuzak said:
Why would the British, who were in desperate need for front line fighters, reject an aircraft which out-performed the Spitfire?

The Spitfire V had a higher critical altitude, so it is not surprising that the P-39 lightweight special out-climbed it at low altitude.

Money. By the time the P-300s were coming off the line the British 1. no longer needed them and 2. Couldn't (didn't want to) pay for them.

Glider · Mar 14, 2019

P-39 Expert said:
Money. By the time the P-300s were coming off the line the British 1. no longer needed them and 2. Couldn't (didn't want to) pay for them.

You do of course have evidence for this statement don't you?

pbehn · Mar 14, 2019

Glider said:
You do of course have evidence for this statement don't you?

He didn't last time, its like groundhog day.

Shortround6 · Mar 14, 2019

Does anybody really know how many the British did pay for?

From Joe Baugher's site.

"By the time this decision was made, production of British-contract Airacobras had reached four a day at Bell's Buffalo plant. The initial contract for 170 planes (RAF serials AH570 thru AH739) had been completed before the end of September, and all but six of these planes had actually been shipped to Britain. However, many of them remained in their crates and were shipped directly to the Soviet Union without being opened. Somewhere between 80 and 100 Airacobras were assembled and flown in Britain by the end of 1941. They were gathered at maintenance units for final modification before being re-crated and shipped to the Soviet Union during 1942. In all, the Soviet Union received 212 of the British Airacobras (some of them shipped direct from the USA), but 49 more were lost at sea en route. "

and

"After Pearl Harbor, the USA found itself in desperate need of aircraft to stem the Japanese onslaught in the Pacific. Consequently, nearly 200 of the British direct-purchase Airacobras still in the USA were promptly requisitioned by the USAAC. Although they were similar to the USAAC's P-39Ds, they were not identical and were known by the USAAC under the non-standard designation of P-400. "

"The P-400s also saw some use closer to Britain. 179 of the Airacobras sent to Britain were re-acquired by the USAAF and were sent to North Africa to join the Twelfth Air Force. "

This seems a bit confusing and needs clarification. It also appears that unless the Americans refunded the money the British had paid up front for the P-400s Britain didn't get out of the contract.

Another book on "lend-lease" aircraft may confuse the British cash purchase with lend lease. It lists the Martin Marylander as lend lease including the ex french ones.

In any case for the Airacobra out of 678 aircraft There are 5 batches of aircraft.

Out of the first batch of 170 planes (serial numbers AH570-739) about 80 were used by the RAF, some were used by the USAAF and 94 are confirmed (with serial numbers listed) as going to Russia.

The next batch of 121 aircraft ( serial numbers AP264-384) was taken over by the USAAF, 12 were lost at sea in transit, 20 went to Russia.

3rd batch of 84 aircraft (serial numbers BW100-183) was delivered but but many handed over to the USAAF, others shipped to Russia BW114 went to the RAF.

4th batch of 300 aircraft (serial numbers BX135-424) Majority taken over by the USAAF, others shipped to Russian at least 17 lost at sea.

5th Batch was the 3 ex USAAF P-39C aircraft sent to England for evaluation/training/familiarization. These last 3 planes were lend lease.

So again, how many did the British wind up paying for or were they given credit for the planes the USAAF wound up getting?

BiffF15 · Mar 14, 2019

Shortround6 said:
Does anybody really know how many the British did pay for?

From Joe Baugher's site.

"By the time this decision was made, production of British-contract Airacobras had reached four a day at Bell's Buffalo plant. The initial contract for 170 planes (RAF serials AH570 thru AH739) had been completed before the end of September, and all but six of these planes had actually been shipped to Britain. However, many of them remained in their crates and were shipped directly to the Soviet Union without being opened. Somewhere between 80 and 100 Airacobras were assembled and flown in Britain by the end of 1941. They were gathered at maintenance units for final modification before being re-crated and shipped to the Soviet Union during 1942. In all, the Soviet Union received 212 of the British Airacobras (some of them shipped direct from the USA), but 49 more were lost at sea en route. "

and

"After Pearl Harbor, the USA found itself in desperate need of aircraft to stem the Japanese onslaught in the Pacific. Consequently, nearly 200 of the British direct-purchase Airacobras still in the USA were promptly requisitioned by the USAAC. Although they were similar to the USAAC's P-39Ds, they were not identical and were known by the USAAC under the non-standard designation of P-400. "

"The P-400s also saw some use closer to Britain. 179 of the Airacobras sent to Britain were re-acquired by the USAAF and were sent to North Africa to join the Twelfth Air Force. "

This seems a bit confusing and needs clarification. It also appears that unless the Americans refunded the money the British had paid up front for the P-400s Britain didn't get out of the contract.

Another book on "lend-lease" aircraft may confuse the British cash purchase with lend lease. It lists the Martin Marylander as lend lease including the ex french ones.

In any case for the Airacobra out of 678 aircraft There are 5 batches of aircraft.

Out of the first batch of 170 planes (serial numbers AH570-739) about 80 were used by the RAF, some were used by the USAAF and 94 are confirmed (with serial numbers listed) as going to Russia.

The next batch of 121 aircraft ( serial numbers AP264-384) was taken over by the USAAF, 12 were lost at sea in transit, 20 went to Russia.

3rd batch of 84 aircraft (serial numbers BW100-183) was delivered but but many handed over to the USAAF, others shipped to Russia BW114 went to the RAF.

4th batch of 300 aircraft (serial numbers BX135-424) Majority taken over by the USAAF, others shipped to Russian at least 17 lost at sea.

5th Batch was the 3 ex USAAF P-39C aircraft sent to England for evaluation/training/familiarization. These last 3 planes were lend lease.

So again, how many did the British wind up paying for or were they given credit for the planes the USAAF wound up getting?

How the heck did the accountants keep up with who owed how much to whom, and who got paid and how / when? What a mess...

Cheers,
Biff

Kevin J · Mar 14, 2019

BiffF15 said:
How the heck did the accountants keep up with who owed how much to whom, and who got paid and how / when? What a mess...

Cheers,
Biff

This is my take on deliveries (includes lost at sea) to Russia but correct me as I may be wrong:-

P-39D-1 336 Lend-lease
P-39D-2 50 Lend-lease
Cobra I 212 British purchase
P-39K 50 Lend-lease
Total = 648 So 27 short of total British order of 675

Plus,
P-39N 1097 Lend-lease
P-39Q 3291 Lend-lease

So,
Grand Total = 5036 so figure that one out.

Interestingly, Australia got,

P-39D-2 12 Lend-lease ?
P-39F 10 Lend-lease ?

and Britain got,
P-39C 3 Lend-lease

Add these last 3 numbers to the 648 and you get 673, almost the original number ordered by the Brits. Is there any accounting connection here.

P-39 Expert · Mar 15, 2019

Glider said:
You do of course have evidence for this statement don't you?

Need: The P-400 was ordered by France in 1940. After France fell the contract was assumed by the British. The British won the Battle of Britain in the fall of 1940. That meant there would be no invasion of Britain so they no longer needed those planes that started being delivered in 1941.

Ability to pay: Britain had been standing alone against Germany since the fall of France. The war was very expensive for them. This was in 1941 before Pearl Harbor and the US being actively involved.

pbehn · Mar 15, 2019

BiffF15 said:
How the heck did the accountants keep up with who owed how much to whom, and who got paid and how / when? What a mess...

Cheers,
Biff

It all became academic, at the end perfectly good aircraft were scrapped or thrown off carriers so they didn't have to be paid for with the full agreement of the USA.

Peter Gunn · Mar 15, 2019

All this P-39 talk brings to mind a book I have written in the early 1980's about the Eagle Squadrons, I'll have to dig it out this weekend. There were a bunch of interviews and such in it and at one point I think there were about a dozen pilots from said Eagles tasked with transporting some P-39's slated for duty in Africa I believe. Not sure like I said, I'll have to dig up the book, but as I recall, they were less then enthusiastic about the P-39 after flying combat ops in Spitfires.

Peter Gunn · Mar 15, 2019

Glider said:
You do of course have evidence for this statement don't you?

P-39 Expert said:
*SNIP*

Ability to pay: Britain had been standing alone against Germany since the fall of France. The war was very expensive for them. This was in 1941 before Pearl Harbor and the US being actively involved.

I don't mean to be picky P-39, but that's not evidence...

wuzak · Mar 15, 2019

P-39 Expert said:
Need: The P-400 was ordered by France in 1940. After France fell the contract was assumed by the British. The British won the Battle of Britain in the fall of 1940. That meant there would be no invasion of Britain so they no longer needed those planes that started being delivered in 1941.

Ability to pay: Britain had been standing alone against Germany since the fall of France. The war was very expensive for them. This was in 1941 before Pearl Harbor and the US being actively involved.

The real reason was that Britain had the P-39 fitted with the necessary equipment for fighter operations in the ETO, as experience showed them, and found the performance wanting.

Actually, it was shit.

Shortround6 · Mar 15, 2019

P-39 Expert said:
Need: The P-400 was ordered by France in 1940. After France fell the contract was assumed by the British. The British won the Battle of Britain in the fall of 1940. That meant there would be no invasion of Britain so they no longer needed those planes that started being delivered in 1941.

Ability to pay: Britain had been standing alone against Germany since the fall of France. The war was very expensive for them. This was in 1941 before Pearl Harbor and the US being actively involved.

Hardly evidence.

as noted before, the British took delivery and paid for all the other aircraft they ordered during the same time period.

You have yet to show any evidence that

1. The British got out of the contract.
2. The British refused delivery of the aircraft.
3. The British got any of their money back.

Now there is a bunch of pure malarkey in books and on the internet Like "Still, the British needed a high-altitude fighter and dumped their P-39s on the USAAC; the rest of the order was cancelled. "

Now as we have seen, the orders (pural) were not canceled, the recipient's changed but the orders were not canceled (the planes were built, sometimes with different details and designations)

The British were busy dumping their P-39s on the Russians, not the the USAAC.

Then we have one of my favorite explanations to a lot of things, TIMING, by the end of Dec 1941 the USAAC had taken delivery of 404 P-39Ds (Birch Mathews book) which is a considerable number BUT, according to AHT (Dean) Bell built 926 Airacobras in 1941 total and 191 of them were in Dec.
There had only been about 20 Airacobras built in the first 4 months of 1941 and those were the P-39Cs and one or two of the British aircraft (including the Special). Bell managed to get production up to 50 aircraft in July and then went to triple digits for the rest of the year.

However we have a real discrepancy in the numbers. 926 Airacobras minus 20 C leaves 906. 675 British planes plus 404 P-39Ds is 1079 planes. We are off by 173 planes.
Either there aren't anywhere near as many P-39Ds as Mathews claims or the British orders are not complete at this time.
Some of these figures may not be accurate as even the same books do not agree with themselves. AHT (Dean) claims in a different chapter that as of Pearl Harbor 600 P-39s had been built for the US Army. They equipped 5 fighter Groups, not

AHT (Dean)also claims that as of Dec 31st 1941 Bell had built 926 Airacobras. 429 P-39Ds and 229 P-39Fs. These numbers leave just 238 British Airacobra Is built in 1941?????

The British didn't need to "dump"their now unwanted P-39s on the USAAC, the USAAC was scrambling for just about every airplane it could get.

Shortround6 · Mar 15, 2019

wuzak said:
The real reason was that Britain had the P-39 fitted with the necessary equipment for fighter operations in the ETO, as experience showed them, and found the performance wanting.

Actually, it was shit.

I would note that the US fitted pretty much the same equipment to the P-39D (ordered in the spring of 1940) got pretty much the same weight gain and pretty much the same drop in performance. Only thing is the US Army knew it, and the Army and Bell negotiated the contracts to suit after a long and sometimes contentious negotiation.
So far there is no evidence the British added anything the USAAC didn't. In fact they used a lighter cannon.

P-39 Expert · Mar 15, 2019

The British never got out of the contract because the Japanese bombed Pearl Harbor and the AAF needed all the planes they could get, including the P-400s that Britain didn't want.

Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (1 Viewer)

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