P-39 Tank Busters (1 Viewer)

[tomo pauk]

You want to check that:

Yes, you are right, my mistake.

 

[bf109xxl]

I guess that not everybody saw the memo that someone should have produced on that subject. When the RAF first came up with the Hurricane IID. equipped with two 40MM cannon for tank busting, the USAAF bragged that the 37MM in the P-39 could do the job. But the RAF did testing using an actual captured German tank and found that the 37MM in the P-39 could not penetrate German armor. The 37MM in the P-39 was not even the equivalent of the 37MM used in the Stuart tank. It was designed only for air-to air use and had not nearly the required velocity to punch through armor.

Was the probability of hitting a tank evaluated during testing? According to the results of Soviet tests of 37 mm cannons (111P) on LaGG and Yak aircraft, the results were completely disappointing: even the most experienced pilots demonstrated a probability of only a few percent, while less trained pilots failed to hit the target at all - and this was at a much higher RoF!
It hardly makes sense to discuss penetration when the probability of direct hitting the target is zero.

One P-39 pilot in the Med said that the 37MM did a nice job of clearing the decks of barges, but nobody talked about the round penetrating significant armor.

The Soviets widely used Cobras to attack ground targets and naval vessels, but only attacks on lightly armored or unarmored targets like cars, locomotives, aircraft on airfields, and unarmored ships were effective when the target could be damaged by fragments. At the same time, I cannot recall any complaints about low penetration: apparently, the Soviets understood that no miracles were to be expected - Il-2s dropping hundreds of PTABs on tanks in a single sortie were much more effective.

 

[MIflyer]

Was the probability of hitting a tank evaluated during testing?

No. They just tied down a P-39 and shot at a Panzer chassis. The point was to see if it could penetrate tank armor as good as the Vickers gun under optimum conditions. They did find out that the gun jammed every time they tried to fire more than one round and had to modify the ejector to fix that. I wonder how the P-39 even got out of the factory with that design defect?

 

[bf109xxl]

No. They just tied down a P-39 and shot at a Panzer chassis. The point was to see if it could penetrate tank armor as good as the Vickers gun under optimum conditions. They did find out that the gun jammed every time they tried to fire more than one round and had to modify the ejector to fix that. I wonder how the P-39 even got out of the factory with that design defect?

The Soviets noted the unreliable functioning of the 37 mm cannons on early Cobras. In addition, the trigger was awkward, making aiming difficult for the pilot - this drawback was initially improved directly in the units. But in general, Soviet pilots considered the weapons on the N and Q series as reliable.

 

[Greyman]

Was the probability of hitting a tank evaluated during testing? According to the results of Soviet tests of 37 mm cannons (111P) on LaGG and Yak aircraft, the results were completely disappointing: even the most experienced pilots demonstrated a probability of only a few percent, while less trained pilots failed to hit the target at all - and this was at a much higher RoF!
It hardly makes sense to discuss penetration when the probability of direct hitting the target is zero.

The Soviets widely used Cobras to attack ground targets and naval vessels, but only attacks on lightly armored or unarmored targets like cars, locomotives, aircraft on airfields, and unarmored ships were effective when the target could be damaged by fragments. At the same time, I cannot recall any complaints about low penetration: apparently, the Soviets understood that no miracles were to be expected - Il-2s dropping hundreds of PTABs on tanks in a single sortie were much more effective.

The US did testing at Eglin Field and claimed 60% hits in beam and frontal attacks vs. M3 light and M3 medium tanks. This was done in a manner similar to the British method; low-level and single, aimed shots (three per attack was found to be optimum).

I'd say this very high degree of accuracy makes sense with the Airacobra's centreline mounting, good handling characteristics for this type of work, and the very high accuracy of the M4 cannon itself.

For what it's worth the Soviets were also very impressed with the accuracy of the 40-mm Vickers guns in the Hurricane, noting that their similar weapons compared very unfavourably in that regard.

 

[bf109xxl]

Comparison of motor-cannons according to Soviet data:

Source: "Soviet Aviation Weapons: Aircraft Against Tanks" by Oleg Rastrenin, 2017

 

[bf109xxl]

The US did testing at Eglin Field and claimed 60% hits in beam and frontal attacks vs. M3 light and M3 medium tanks. This was done in a manner similar to the British method; low-level and single, aimed shots (three per attack was found to be optimum).

For me, this is an astonishing result. Either the tests involved particularly outstanding pilots, or I am underestimating the weakness of Soviet pilot training, or the Soviets used some special testing methodology... For me, it's a real mystery.

I'd say this very high degree of accuracy makes sense with the Airacobra's centreline mounting, good handling characteristics for this type of work, and the very high accuracy of the M4 cannon itself.

The LaGG and Yak also had centreline mounting, their cannons were quite accurate on their own, but when firing, the high recoil reduced both the accuracy and precision drastically. Perhaps the Cobra was a more stable platform, as well as the Hurricane.

For what it's worth the Soviets were also very impressed with the accuracy of the 40-mm Vickers guns in the Hurricane, noting that their similar weapons compared very unfavourably in that regard.

The Soviets highly rated the quality of the weapon's mounting in the wing, which minimized the moments that deflected the aircraft when firing. Additionally, the Hurricane was a stable weapon platform. The Soviets rated the gun itself very poorly.

 

[MIflyer]

But in general, Soviet pilots considered the weapons on the N and Q series as reliable.

I read a statement by a Soviet pilot saying that he liked the Q-5 best of all. This is puzzling to me, since a US pilot said that the Q with the underwing guns was less stable than the early models with the four .30 cal guns at high speed. The Soviet pilot also said that Q-5 was lighter and more maneuverable, which is also puzzling since the Q-5 was not one of the lighter versions. It leads me to wonder if he was flying a Q-5 with the wing guns removed, even though that was not one of the versions built without them.

For me, this is an astonishing result. Either the tests involved particularly outstanding pilots, or I am underestimating the weakness of Soviet pilot training,

At Eglin no one was shooting at them. In the 1980's the US Army found that accuracy for TOW missiles suffered quite a bit if you did nothing more than set off an unexpected explosion in the vicinity after the missile had been fired. Nobody even had to be shooting at the operator. I'll bet the Soviet pilots were being shot at quite a lot.

A USAAF P-39 pilot in the Pacific said that the key to shooting with the 37MM was to ONLY fire it under POSITIVE G's. While diving you usually have NEGATIVE G's. The answer he found was to dive steeply enough so that you could PULL UP a tad and put the sight on the target before firing.

 

[bf109xxl]

I read a statement by a Soviet pilot saying that he liked the Q-5 best of all. This is puzzling to me, since a US pilot said that the Q with the underwing guns was less stable than the early models with the four .30 cal guns at high speed. The Soviet pilot also said that Q-5 was lighter and more maneuverable, which is also puzzling since the Q-5 was not one of the lighter versions. It leads me to wonder if he was flying a Q-5 with the wing guns removed, even though that was not one of the versions built without them.

The main reason was that the aircraft could be lightened: the fuel capacity of the Q-5's internal tanks was reduced, a couple of wing machine guns and less vital armor (and even oxygen equipment and some radio equipment!) could be removed, which was widely practiced in Soviet air regiments. In later versions of the Q series, the fuel tank capacity was increased. Even a small weight reduction had a positive impact on performance, and the Q-5 turned out to be the lightest.

At Eglin no one was shooting at them. In the 1980's the US Army found that accuracy for TOW missiles suffered quite a bit if you did nothing more than set off an unexpected explosion in the vicinity after the missile had been fired. Nobody even had to be shooting at the operator. I'll bet the Soviet pilots were being shot at quite a lot.

Well, the tests were conducted at a proving ground where no one fired at the aircraft, however I don't know all the restrictions imposed on maneuvering, to be honest.

A USAAF P-39 pilot in the Pacific said that the key to shooting with the 37MM was to ONLY fire it under POSITIVE G's. While diving you usually have NEGATIVE G's. The answer he found was to dive steeply enough so that you could PULL UP a tad and put the sight on the target before firing.

During the Soviet tests, firing was carried out while diving at an angle of no more than 30°, with a distance of no more than 500 m, otherwise armor penetration could not be guaranteed. The sniper pilot achieved a probability of 12%, while for a simply experienced pilot it was 2%, and pilots with average training did not hit anything at all. And if the best pilot in training conditions achieved only 12%, then a mass pilot under anti-aircraft fire will achieve, at best, a vanishingly small percentage of hits. But perhaps the training of British pilots was incredibly high...

 

[Greyman]

For me, this is an astonishing result. Either the tests involved particularly outstanding pilots, or I am underestimating the weakness of Soviet pilot training, or the Soviets used some special testing methodology... For me, it's a real mystery.

The LaGG and Yak also had centreline mounting, their cannons were quite accurate on their own, but when firing, the high recoil reduced both the accuracy and precision drastically. Perhaps the Cobra was a more stable platform, as well as the Hurricane.

Without knowing exactly how the Soviets did things, I can only guess. But just by the phrasing used it seems to me the Soviets were trying to hose the targets with full-auto bursts -- whereas the British and US method involved taking single shots, realigning the sights on target, firing another shot, and so on.

This was a highly specialized process, and the weapons & sight had to be very carefully harmonized for the precise conditions of the attack -- the British noting that varying the attack speed by more than 10 mph was enough to effect shooting. Perhaps the VVS didn't put in the same level of care re: harmonization and/or attack profile.

The Soviets highly rated the quality of the weapon's mounting in the wing, which minimized the moments that deflected the aircraft when firing. Additionally, the Hurricane was a stable weapon platform. The Soviets rated the gun itself very poorly.

I was going off of this article here: Испытано в СССР. Истребитель-штурмовик Hawker Hurricane IID - Альтернативная История

Зато у «Харрикейна» было другое преимущество. Рассеивание нескольких очередей при стрельбе в воздухе из пушек по полотнищам, расположенным на земле, у самолета «Харрикейн» оказалось примерно в 2-2,5 раза меньше, чем у самолетов ЛаГГ-3 и Як-9т с пушкой НС-37, и в 6-6,5 раз меньше, чем у самолета Ил-2 с пушками НС-37. Смещение центров группирования попаданий по отношению точки наводки прицела у самолета «Харрикейн» меньше, чем у Ил-2 с НС-37 примерно в 4-11 раз меньше.

Рассеивание при стрельбе в воздухе из пушек у самолета «Харрикейн» IID, по сравнению с рассеиванием при стрельбе на земле, возрастало в 10-18 раз, а у самолета Ил-2 — в 30-100 раз.​

via Google:

However, the Hurricane had another advantage. The dispersion of multiple bursts fired in the air from cannons at ground targets was approximately 2-2.5 times smaller on the Hurricane than on the LaGG-3 and Yak-9T with NS-37 cannons, and 6-6.5 times smaller than on the Il-2 with NS-37 cannons. The shift in the center of impact grouping relative to the aiming point of the gunsight was approximately 4-11 times smaller on the Hurricane than on the Il-2 with NS-37.

The dispersion of cannons fired in the air from the Hurricane IID, compared to the dispersion on the ground, was 10-18 times greater, while on the Il-2 it was 30-100 times greater. ​

It was my understanding that 'Service' ammunition never made it to Russia, and only 'ball' training rounds were at hand. The penetration figures given in the article and in your table seem to bear that out. This would certainly colour any appraisal of the weapon's suitability for the front line.

For what it's worth No.6 Squadron (flying the Hurricane IId in Egypt) was expected to achieve a hit rate of 50% and fully-trained pilots were getting 75%. This required a high level of training and practice.

 

[bf109xxl]

Without knowing exactly how the Soviets did things, I can only guess. But just by the phrasing used it seems to me the Soviets were trying to hose the targets with full-auto bursts -- whereas the British and US method involved taking single shots, realigning the sights on target, firing another shot, and so on.

The Soviet Air Force reasonably believed that in conditions of strong AA fire (the reality of the Eastern Front), pilots would not be able to strictly adhere to speed restrictions. During testing, firing was carried out both with single shots and with bursts of varying duration.

This was a highly specialized process, and the weapons & sight had to be very carefully harmonized for the precise conditions of the attack -- the British noting that varying the attack speed by more than 10 mph was enough to effect shooting. Perhaps the VVS didn't put in the same level of care re: harmonization and/or attack profile.

In the USSR, the combat use was optimized quite meticulously. During field tests, the most optimal solutions were usually found, but poorly trained pilots failed to apply them in practice.

It was my understanding that 'Service' ammunition never made it to Russia, and only 'ball' training rounds were at hand. The penetration figures given in the article and in your table seem to bear that out. This would certainly colour any appraisal of the weapon's suitability for the front line.

Taking into account that ~60 Hurricane IIDs and several dozen (?) Hurricane IVs were delivered to the USSR (since August, 1943), which even took part in combat in 1944 (246th IAP), albeit sporadically, I find it difficult to imagine that their ammunition consisted exclusively of training rounds. Based on the test results, the Hurricane IID was considered unsuitable for ground-attack missions by the Soviets, despite the high accuracy and precision of its cannons. Ironically, the Soviets finally deployed it for air defense. Pilots in combat units begged to be transferred to Soviet fighters from Hurricane IIDs, which was done fairly quickly.

For what it's worth No.6 Squadron (flying the Hurricane IId in Egypt) was expected to achieve a hit rate of 50% and fully-trained pilots were getting 75%. This required a high level of training and practice.

A weak cannon with low recoil (compared to Soviet ones), good weapon mounting, a stable platform, no strong anti-aircraft fire, and highly trained pilots may have contributed to such a high performance.

In addition: I read the article at the link - it's actually a reprint of an article by Oleg Rastrenin. Once again, I was convinced that the absurdity of Soviet reality can exceed all expectations. And yes, only training rounds were delivered to the Soviets, and the 246th IAP never made any combat sorties. Thanks for the reference!

 

[ThomasP]

The following are excerpts from the Operational Records of No.6 Squadron RAF (North Africa) 1942, while flying the Hurricane Mk IID:

"On sighting the target the formation goes down to 15/20 feet and approximately 1,000 yards away. . . . The approach is made at a speed of 240 mph, since the datum line is then 2° down, sights being set parallel. Variation of 30 mph will affect the accuracy of the shooting. Fire is opened at 700 yards closing to 200 yards, and both Brownings and 'S' Guns are used. The Brownings and 'S' Guns are harmonised at 500 yards. After each burst of one shell per gun the sights are realigned on the target. Normally about 5 bursts can be got in on each attack. The break away is made before reaching the target if possible, to avoid being hit by splinters, and the area is cleared by low flying weaving. If the tanks are isolated up to 3 attacks can be made. . . ."
. . .
"The latter (large groups of M.T.) were always avoided if possible, as the German M.T. seemed to carry a very large amount of very effective light A/A."
. . .
No.6 Sqn flew 162 sorties from June-November 1942, with 25 aircraft casualties, 10 category I (repairable at the unit level), 9 category II, and 6 category III (1 missing, 4 abandoned on the ground and lost to the enemy). Only 1 pilot was lost (the pilot of the missing plane) and presumed KIA.

The following is an excerpt from a report by Operational Research Unit testing in the Far East:

['S' gun] "tests in the Far East showed a high level of accuracy in the field, with an average of 25% of shots fired at tanks striking the target. Attacks with HE were twice as accurate as with AP, possibly because the ballistics were a closer match with the .303 cal Browning used for sighting. . . . By comparison, the practice strike rate of the 60pdr RPs fired by fighter-bombers was only 5% against tank-sized targets."

NOTE
1. The pilots were highly experienced in both Army Cooperation and in ground attack with their Hurricane Mk IID.
2. There were 3 different AP rounds issued during the 40mm 'S' gun's operational life:
Mk I - 2.437 lb AP shot (no penetrating or ballistic cap)
Mk II - used only in small quantities, replaced by Mk V
Mk V - 3 lb AP shot (no penetrating or ballistic cap)

MV with 3 lb Mk V AP was 1875 ft/sec static + 350 ft/sec (due to 240 mph forward flight speed of the Hurricane) = 2225 ft/sec when fired from the Hurricane at 240 mph (350 ft/sec). Penetration against I.T.80 class armour at 0°/20°.
74/66mm at 200 yds
66/58mm at 400 yds
51/45mm at 700 yds

The 3 lb AP Mk V entered service in late spring of 1942 (I think).

 

[tomo pauk]

No.6 Sqn flew 162 sorties from June-November 1942, with 25 aircraft casualties, 10 category I (repairable at the unit level), 9 category II, and 6 category III (1 missing, 4 abandoned on the ground and lost to the enemy). Only 1 pilot was lost (the pilot of the missing plane) and presumed KIA.

That low pilots' loss rate is simply amazing.