Luftwaffe's Sturmoviks

[Tony Williams]

Stuka was an awsome dive bomber. I could place a bomb within 15m of aim point...thats like a lazer guided bomb interms of accuracy. Even the best level bombing is 700m CEP without instrument guidance.

Do you have a source for the Stuka accuracy? The figure which sticks in my mind was that a CEP of 30m by a good crew, but I can't recall where I read that. Still much better than the 100+m for a fighter-bomber, but not accurate enough to be a reliable tank-killer; if it were, the Luftwaffe wouldn't have bothered with the Ju 87G.

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[Tony Williams]

The penetration of AP projectiles decreased rapidly as the angle of attack decreased, and this particularly affected the German Hartkernmunition used in the MK 101/103 and BK 3,7 anti-tank guns.

At 60 degrees obliquity (from normal on the surface), the usual angle from which antitank planes attacked their targets, BK 3,7 could still penetrate 70-60mm of armor. BK 3,7 had no problems in penetrating the T-34s hull from any direction.

See the figures at the end of this message.

So to get a favourable angle of attack onto a tank's upper surfaces would have involved a very steep dive from above, which not even the Ju 87G could manage (the weight of the guns prevented recovery from a steep dive).

That's hardly the case. The usual dive angle from which tanks were atacked was a mild 30 degrees.

Er, yes - I know. That's why I said that it wasn't feasible to attack at a steep enough angle to penetrate the horizontal armour, even for the Ju 87G

I have posted an article on my website - 'Tankbusters: Airborne Anti-Tank Guns of WW2' - which gives details of the guns, their ammunition, their armour-piercing performance and the planes they were fitted to. Just scroll down the front page until you reach it.

I went there and I saw a mistake. You say about BK 3,7:

It mainly fired Hartkernmunition ammo, capable of penetrating up to 140 mm / 100 m / 90 degrees although this was halved at a striking angle of 60 degrees.

It's the usual confusion between 30 and 60 degrees, from the vertical on the surface or the horizontal.
If the reference is the horizontal then when you can say that it was capable of penetrating 140mm/100m/90degrees, aprox 120mm/100m/60degrees,
and aprox 70mm/100m/30degrees.

I found 120mm/100m/60degrees(from horizontal) penetration for 37mm APCR round in "Aggressors Volume 1: Tank Buster vs. Combat Vehicle", Alex Vanags-Baginskis and Rikyu Watanabe, Airlife, 1993.

No mistake. I have the official penetration curves for the 37mm H-Pzgr in front of me, which are a rather more authoritative source than any published book. Penetration at 100m went as follows:

90 degrees = 140mm
80 = 134mm
70 = 117mm
60 = 70mm
50 = 45-50mm

At 600m (a more typical firing distance) the figures were:

90 degrees - 95mm
80 = 85mm
70 = 65mm
60 = 45-50mm
50 = 35mm

As you can see, there is a rapid fall-off in penetration, particularly when you reach 60 degrees (which is equivalent to an attack on the side armour by a plane in a typical 30 degree dive). Of course, if the plane wasn't precisely in line with the side or rear of the tank, the effective angle of attack would be that much worse, as there would be a horizontal angle to exacerbate the vertical one.

Another factor which is not included in these figures is the effect of hitting anything in front of the armour. This had an effect on all AP projectiles as it tended to destabilise them (even penetrating a thin, light-alloy aircraft skin could reduce AP performance by 30 percent), and the H-Pzgr in particular were very sensitive to this. In fact, any kind of add-on plate like the German Schuertzen disrupted the H-Pzgr so much that conventional AP was recommended as more effective.

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[Uninen]

At 600m (a more typical firing distance) the figures were:

Have you seen gun camera / other footage of Hs 129 and Ju 87G's attacking a tank(s)? From all ive seen 100 to 300m is more like it..

[Tony Williams]

At 600m (a more typical firing distance) the figures were:

Have you seen gun camera / other footage of Hs 129 and Ju 87G's attacking a tank(s)? From all ive seen 100 to 300m is more like it..

I have a harmonisation diagram for the Ju 87G which shows the aiming point as either 400 or 450m (I forget which offhand). However, I do know that Rudel ended up harmonising his guns at around 100m, probably because the targets toughened up (a KV was a much tougher nut than a T-34).

I'm not sure what the attack speed of a Ju 87G or Hs 129 would have been, but if we assume around 350 kph, this is equivalent to around 100 m/s. So at 100m they would have been just one second away from slamming into the tank. Obviously, a highly skilled pilot like Rudel could get away with it, but it must have required uncommon judgment.

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[richardrli]

Just a quick question for Tony, which had better penetration, the 37mm on the Il-2 or JU-87? I think they were the similar.

[Paul Lakowski]

Exactly right! I calculated 37mm penetration at angles of ~ 70°-80° and concluded that later model T-34 could not be penetrated effectively. The 50mm PAK 38 on the other had should penetrate the top armor of just about any WW-II tank from that angle using steel ammo since WC is unlikely from 1943 on. Pak 40 is right out due to its heavy weight and adverse effect on plane stability....unless your firing from a Ju-88?

Have you considered that APCR ammunition for your calculations?
.

Every source I've read says that APRC is out after 1942 due to material shortages, although exceptions are made in 1943 for 50mm Pak gun [and maybe this 37mm BK gun]. So the main round for the last part of the war would be all steel.

Tony is right about the fall off from APRC ...I think at 60° its something like 1/5 of the penetration of vertical penetration figure . The strike angle is 70-80° for most straffing attacks since they come in at low angle. Thats very shallow dive. At that angle most ammo will simply ricochet away unless it overmatches the armor thickness with a relatively flat nosed penetrator.

If it overmatches is 1:1 then richocet occurs at 60°, if 0.5:1 then the ricochet is about 70° and at 0.25 its ~ 75°. So a 50mm steel APC penetrator should work upto...
50mm @ 60°
25mm @ 70°
13mm @ 75°

At these angles ricochet should occur so you want to attack at angles above those levels to ensure projectile 'can' penetrate and not ricochet off the armor...ofcourse if the projectile hits the glacis or rear hull plates, these are at angle so the adjusted straffing impact angle should be ~50°-40°.

[Tony Williams]

Just a quick question for Tony, which had better penetration, the 37mm on the Il-2 or JU-87? I think they were the similar.

The 37x195 ammo for the NS-37 was actually more powerful than the 37x263B for the BK 3,7 so given the same ammo type it would have performed better. However, they did not seem to use any APCR (although details of an APCR round for this ammo have recently been discovered), so they were limited to a lower maximum penetration.

The NS-37 gun was much superior to the BK 3,7 being smaller, lighter, faster-firing and belt-fed.

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[Tony Williams]

Every source I've read says that APRC is out after 1942 due to material shortages, although exceptions are made in 1943 for 50mm Pak gun [and maybe this 37mm BK gun]. So the main round for the last part of the war would be all steel.

You are correct that the BK 3,7 was an exception to the general ban on APCR. So was the 30mm MK 103.

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[kfbr392]

I'm not sure what the attack speed of a Ju 87G or Hs 129 would have been, but if we assume around 350 kph, this is equivalent to around 100 m/s. So at 100m they would have been just one second away from slamming into the tank. Obviously, a highly skilled pilot like Rudel could get away with it, but it must have required uncommon judgment.

I'd say a Hs 129 would be more like 70m/s = 250km/h when tank hunting. Reason: Top speed at great altitude is just above 400km/h for the "fliegender Büchsenöffner". Top speeds are almost twice as much as one reaches when twisting and turning, even if one does swallow dives... (someone playing flight sims will confirm this )

In P. Carell's "Verbrannte Erde" it says that during their July 1943 baptism of fire Hs 129B-1/R2 fired about 3 rounds at a time from the MK 101, that takes less than a second.


P.S:
I greatly enjoyed reading this thread.

[Tony Williams]

In P. Carell's "Verbrannte Erde" it says that during their July 1943 baptism of fire Hs 129B-1/R2 fired about 3 rounds at a time from the MK 101, that takes less than a second.

Yes, but if you're flying straight at a tank you have to allow time for (1) pulling back the stick, and (2) the plane responding to that sufficiently to change direction to climb above the tank. So you would have to decide to pull up before the last 100m!

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[M.Rausch]

Every source I've read says that APRC is out after 1942 due to material shortages, although exceptions are made in 1943 for 50mm Pak gun [and maybe this 37mm BK gun].

Sorry, but then not any of these sources have ever seen any original German ammunition production and storage sheet from the "Chef der Heeresrüstung und Befehlshaber des Ersatzheeres, Stab IIc (Rüst)".

While most Pzgr. 40 types were no longer produced after 1942, the numbers in storage were enough to last till beginning of 1944 and longer.

3.7 cm Pzgr. 40 for the 3.7 cm Kw.K.: 270,000 rounds in storage on December 1943, no production.
5 cm Pzgr. 40 for the 5 cm Kw.K.: 298,000 rounds in storage on December 1943, no production.
5 cm Pzgr. 40 for the 5 cm Kw.K. 39: 32,000 rounds in storage on December 1943, occasional production about equal to usage.
7.5 cm Pzgr. 40 for the 7.5 cm Kw.K. 40: 15,000 rounds in storage on December 1943, production of about 50% of the usage.

3.7 cm Pzgr. 40 for the 3.7 cm Pak: 680,000 rounds in storage on December 1943, no production.
5 cm Pzgr. 40 for the 5 cm Pak 38: 207,000 rounds in storage on December 1943, occasional production.

The start of the production of Pzgr. 40 types can be read in detail in one of my articles:

http://www.beim-zeugmeister.de/zeugmeis ... ?id=40&L=1

I hope to find the time to expand the article to cover the whole production and storage till 1945.

[Epaminondas]

One thing people are forgetting is that two engines are MUCH better then one, when incoming fire is hitting you.

Do you REALLY want an engine hit that redlines an engine in a Stuka?

two engines on a close air support is good.

[Paul Lakowski]

This is interesting articles no doubt, but what it really shows is how restricted the ammo use was. From Hahns production figures 50mm AP 40 shots resulted in 1.25 million AP 40 shots produced from 1941-1943 , while about 1.3 million 37mm AP40 shots were produced from 1940-1942. At the end of that period your figures suggest maybe ~ 300k 50mm AP-40 rounds & 680K 37mm AP-40 rounds left in inventory ,when 1943 50mm AP-40 production was only 226K rounds. Sounds like the rounds were severly restricted. Other 50mm ammo production was 12 million rounds during this period.

Now maybe they can husband these rounds only for the ground attack squadrons but their slanted penetration and accuracy at even short range is not that great anyway...that and they wore the barrels out too much.

[Paul Lakowski]

One thing people are forgetting is that two engines are MUCH better then one, when incoming fire is hitting you.

Do you REALLY want an engine hit that redlines an engine in a Stuka?

two engines on a close air support is good.

This is true if you look at things from a tactical point of view, however by the time these planes came on line, quantity was far far more important than quality. So you could not afford to waste two engines on a mere ground attack plane. Made more sence to fund twin engined night fighters and tactical bombers than another AT system.

[kfbr392]

So you could not afford to waste two engines on a mere ground attack plane. Made more sence to fund twin engined night fighters and tactical bombers than another AT system.

The engines were not "wasted" on the Hs 129, they were after all captured french engines. That means they were looted ... and thus free!
They were too weak to power single engined warplanes (then again one could have opted for a "Hs 129 light": a 1941 Hs 123 with one Gnôme & Rhône 14 M engine) so putting two into a small armored attack plane was a great idea.

The more I read on the Hs 129 the more I come to believe that is one of the most underrated and most successfull planes of WW2..