AA vs Aircraft

[coe]

for some reason I heard that 7.62 wasn't that good in penetrating things like aircraft skin but I could be wrong

[JasonC]

coe - in the battle of Britain the planes were still quite poorly armored, and the German bombers basically remained so throughout the war. The Brits were using large numbers of .303 MGs on their fighters. This resulted in a very high portion of crew casualties to actual plane losses in the German force, because many bombers could make it home after taking significant .303 fire, but against unarmored planes - and especially all the exposed glass for the gunners and pilots - many crewmen took a bullet personally, without the plane itself going down.

Clearly it is less than optimal to use a weapon for AA that largely depends on hitting the actual pilot, a much smaller target than the whole plane.

To be sure, planes were knocked down by sufficient engine hits, and before they got improved fuel tanks, by wing fires caused by ignition of fuel by tracer rounds. But the anti-material ability of rifle caliber ammo is still very limited against large vehicles.

I've seen German studies of the median number of solid hits necessary to knock down heavy US four engine bombers later in the war. They found it took around 20 solid hits by 20mm cannon to bring one of them down, vs. only 3-4 30mm rounds, or a single round of 88 flak close enough. They didn't even bother counting the MG bullets that would be needed - it was too high to be practical, given actual hit rates in high speed engagements and such.

Vs. smaller fighters it would be easier to KO if you hit, but of course also harder to get hits in the first place.

The effective ground fire came from the dedicated light AA. And it was definitely effective - the average deployed light AA weapon probably accounted for at least one enemy fighter bomber over its operational life. They also had high survivability and long useful service lives.

The inefficiency of light AA is the need to deploy it all over, which means large portions of it remain inactive unless enemy air is very active and widespread.

The US put 50 cals on everything in anticipation of continual engagment with the Luftwaffe, given the accounts they had read of the importance of tac air to "blitzkrieg" methods. The armor and even the artillery formations were particularly "tricked out" with the things. The AAA establishment was downright huge, on top of this. The flying 50s had already done the job, though.

The Russians had a useful mix of AA, underrepresented in most wargames and in CM scenarios. They were short on it at the lowest echelons - a few 50 cal or 14.5mm AA MGs at battalion or regiment was about it. In CM, those won't even fire at aircraft. The main weapon was the 37mm AA, fielded in entire divisions (per army, typically). There were enough of these to put batteries of them in a continuous grid of "cells" on important battlefields. That discouraged lingering below 10,000 feet for long, within the Russian ground controlled zone.

The higher altitudes were more sparsely covered by 76mm and 85mm AA, but judging by German loss rates per sortie for their medium bombers, those weren't particularly effective. There are exceptions, though. For instance, trying to maintain the air bridge to Stalingrad, the Germans lost something like 700 aircraft, most of it to ground fire. The Russians could mass AA along the routes in and the planes had to descend etc.

[FAI]

The historical success of the Flak 88 in AT role is clear to everyone. I'm curious though, how well did it perform in AA role? I'm sure there are plenty of historical accounts of Flak 88 employed for it's originally intended purpose, can anyone point one to me?

[JasonC]

The difficulty is assigning losses on the receiving side. If you go by claims on the shooting side, it is going to be unreliable. We don't know if it will be a ground combat or air to air discrepancy like a factor of 2, or an air to ground like factor of 10 to 50, but it will be high.

One thing we can say with certainty - the chance of getting any kind of disabling hit with each individual round was extremely low. Vast quantities of flak ammunition were expended by huge parks of guns over extended periods of time, to get what hits were achieved.

US losses to enemy action in 8th air force were 6900 heavy bombers and 3600 fighters, for the war as a whole. If you go to all air forces world wide the totals become about 10,000 bombers and 8500 fighters. These aren't all losses - a whopping 12500 planes were lost in accidents and crashes of all kinds. We don't know the flak portion of the total. It might be as low as a third for the 8th air force, as the fighters over Germany remained thick through mid 1944 and were more effective. It might be half.

The Brits also lost planes of course, bombing at night and in their tac air. The Russians did less deep bombing but certainly lost planes to flak in the forward areas (more of it FBs to light flak probably). Overall, Flak might have taken out something like the scale of US losses above, taking all allied air forces into account. Call it 15k with a plus or minus 5k error bar.

To get that, the Germans fielded 14,000 88s, almost 20,000 37s, and by barrel count 120,000 20s (perhaps 50% of them in quad form, or 15k quads and 60k singles). So I have to revise my previous statement - the average Flak system did not account for an enemy AC over its entire service life. And 88 might have a 1/4 chance of doing so, up to 1/2 at the most generous estimate of Flak losses and relative effectiveness of heavy vs. light flak.

As a cross check, consider the experience of III Flak corps in Normandy. They claimed 462 AC, but as an own side claim that is not to be taken too literally without some kind of haircut. On the other hand, the targets were presumably lower altitude than was typical over Germany, for the most part, so the performance might have been above the whole war average.

They used 161 88s and on the order of 300 medium or light systems, counting replacements. So own side claims are approaching unity, without all the guns lost - but need to be reduced for overclaiming etc. They expended 209,000 rounds of 88 ammunition (1300 rounds per gun) and nearly 3 million rounds of light (most of it 20mm).

Which means it must have taken at least 1000 rounds of 88mm to down one plane, and more likely several times that figure. For the light AA, add a zero. Fire enough and you occasionally hit something.

[Guest Mike]

Rifle calibre armament for fighters was recognised as insufficient even before the war - the British fielded a squadron of experimental 20mm armed Spitfires in the BoB in 1940, but had considerable problems with the guns and mounts.

RC bullets have little trouble penetrating a/c skins - they do have a lot of trouble doing significant damage to internal structure though. The round holes they make in skins are not significant sources of stress (for causing cracks and structural failure), and the much thicker internal structures are too heavy for them (skins might be as thin as 0.032" - about 1/2mm - main internal structures could be up to 1/2" or 6mm without much bother - possibly thicker in some areas)

I have an account of a chap who flew Buffalo's in Singapore and Burma - one of his colleagues was killed by a rc bullet from a Ki-27 "Nate" that passed through where the armour plate at he back of the seat shold have been - the a/c had been supplied without it although it was part of the specification.

[coe]

1000 rounds of 88mm - does that equal the mass of the plane?

to the extent of armored planes as none being armored at the beginning - we often hear of the Zero being unarmored only - was it less armored compared to others at the begining of the war?

What mystifies me is that in the later parts of the war the Germans didn't start putting .50 calibre type machine guns on their tanks or pretty much any vehicle...of course there is a question of making them!

Conan

[Guest Mike]

Germany didn't make that many HMG's - they did have a tripple 15mm mount on an Sdkfz-251 as the 251/21 , but they figured that 20mm were better value, as did almost everyone else except the yanks.

[JasonC]

Well a B-17 empty weighs about as much as 1400 88 shells. A P-47, about as much as 500 of them. Some estimates of the shells by heavy bomber kill over Germany (as opposed to any AC, at the front as well), run up to 3500. So yeah, you basically had to throw about twice the weight of the AC into the air to take it out, probably.

20% of German ammo production and 30% of gun production in 1944 was for AA.

[Guest Mike]

You'll find some onfo on USN experience of the effectiveness of AA fire here.

also note that in one attack in October 1944 720 USAAF a/c bombed Hamburg through cloud - the flak fired blind and shot down 1 a/c....expending almost 25,000 rounds to do so!

[Other Means]

Originally posted by Stalin's Organist:

You'll find some onfo on USN experience of the effectiveness of AA fire here.

also note that in one attack in October 1944 720 USAAF a/c bombed Hamburg through cloud - the flak fired blind and shot down 1 a/c....expending almost 25,000 rounds to do so!

I wonder what damage all that falling flak did. It's a lot of metal isn't it?

[Broompatrol]

Re: Coe's question on Japanese planes. My understanding is that the Japanese philosophy was to strip planes of "nonessential" equipment to increase range. The aircrews themselves participated in this, too. They would even strip out gauges from the instrument panel but I couldn't tell you what was considered useful or extraneous.

[michael kenny]

Originally posted by JasonC:

The Brits also lost planes of course, bombing at night and in their tac air.

Some 9000 bombers for the whole war.

Originally posted by JasonC:

As a cross check, consider the experience of III Flak corps in Normandy. They claimed 462 AC, but as an own side claim that is not to be taken too literally without some kind of haircut.

2nd TAF losses.

June 302

July 219

August 265.

A total of 786 to all causes for sure but when you add in 8th AF losses

the figure easily rises well over the 1000 mark.

[JasonC]

Of course, the III flak corps was not remotely the only German AA in Normandy.

The US naval info is interesting, particularly for the ratios (more likely to be right than the raw figure) between the weapon types. E.g. 20mm 3 times as effective as 50 cal per round, 40mm (or 37mm, certainly) about 3-4 times as effective as 20mm, and heavy AA (can't be much difference between 5 inch and 88) about 2 times more again.

If the raw figures had been true for Normandy then the III flak corps expenditure would have been sufficient for 685 planes, 50% more than they claimed. Probably it is a lot easier to hit targets at sea closing with the firing platform, than general targets over land.

[RockinHarry]

Originally posted by Other Means:

</font><blockquote>quote:</font><hr />Originally posted by Stalin's Organist:

You'll find some onfo on USN experience of the effectiveness of AA fire here.

also note that in one attack in October 1944 720 USAAF a/c bombed Hamburg through cloud - the flak fired blind and shot down 1 a/c....expending almost 25,000 rounds to do so!

I wonder what damage all that falling flak did. It's a lot of metal isn't it? </font>