Sciatica, Facebook, Aviation themed pages and a claim about B17 and Avro Lancaster...

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SplitRz

Senior Airman
377
598
Feb 6, 2021
Just an idle pondering whilst recovering from two weeks of horrendous sciatica.... (I'm lying one handed on my back holding the laptop over my head!)

It seems like Facebook has taken over from pulpy books and youtube as the new source of aviation mythologies. Stuck in bed a lot of the day, drifting between sleep and pain relief, it seems like the dreaded Meta algorithm has cottoned on t0 my interests and I'm now being bombarded by articles on my FB feed. So many are simply dreadful.

This question pertains to an otherwise really interesting picture of a ruptured Blenheim - its rear fuselage blown up almost like a burst balloon during testing of German 30mm 'mine shells'. The piece then went on to announce how effective these were against allied bomber aircraft and said something along the lines of:

"two or three shells were capable of bringing down a B17. They were even more effective against the less solidly build Avro Lancaster or Handley Page Halifax".

A statement not backed by anything I've ever read. All three aircraft were particularly solidly built. And there's nothing I can see in their similar respective laden and unladed weights that would indicate a lighter construction of the latter than a B17. I did question the post, but alas, can't seem to track it down now to give you the link.

Any thoughts or discussion to distract from from my flaming aches and pain??!
 
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The way of attack would have to do with the results. Night fighter tended to attack from below trying to hit the fuel tanks. Minen geschoss would do an excellent job. B-17 in combat boxes protected by pesky fighters was a different story.

Hope you get well soon.!.
 
SplitRz said:
Just an idle pondering whilst recovering from two weeks of horrendous sciatica....
Click to expand...

Hope you're getting better

As far as I know, German wartime materials didn't differentiate between specific 4 engine bombers. They just calculated that about 500g of HE was necessary to down a 4 engine bomber, and then designed ammunition to deliver this as effectively as possible.

There might be some clues in this:
The Development of German Aircraft Armament to 1945

There are also wartime and immediately post-war studies on fighter armament effectiveness which may contain more clues - but I don't have time to track them down at the moment. I can find reference to Mauser research on 20mm and 30mm effectiveness vs heavy bombers as well as one performed at Bad Eilsen (where Focke-Wulf had a design centre) on hit likelihoods. There was also references to a post war Project RAND study on hit/kill probabilities for fighter weapons.
 
tomo pauk said:
(my bold)
That would be or, not and?
IIRC Germans thought that five 30mm shells is required for a B-17.
Click to expand...
From a discussion posted here somewhere, as I remember it the discussion during WW2 also involved how many rounds a fighter could be expected to hit a bomber with making a high speed pass with escorts present. The question being in a given space of time say 2 seconds (as an example) are you more likely to get 5 hits with a 30mm cannon or 20 hits with 20mm bearing in mind there will be fewer 30mm with a lower rate of fire and poor ballistics.
 
Short of a C130 any aircraft having a 30mm mine shell exploding in it's fuselage would sustain serious damage, but as you pointed out you have to hit it first, I remember reading that the 30mm had to be used from very close range for best results.
 
PAT303 said:
Short of a C130 any aircraft having a 30mm mine shell exploding in it's fuselage would sustain serious damage, but as you pointed out you have to hit it first, I remember reading that the 30mm had to be used from very close range for best results.
Click to expand...

Germans noted that a single MK 103 have had about the double chance to hit the target than a single MK 108, when firing the same 330 g Mine shell. Muzzle velocity difference was staggering; depending what one reads it was 860-900 m/s for 103, vs. 500-520 for the 108.
Problem with the MK 103 was that it was not 'platform-friendly' weapon due to it's bulk, weight and recoil, so the MK 108 ended up being used much more on the fighters. Of course, problem with the MK 108 were it's bad ballistics.
 
The research done indicated the average of 18 to 20 hits of 20mm cannon to bring down a heavy bomber, or 2 to 3 30mm hits, is via causing structural failure, that is no fire. US firing trials at Aberdeen using German 20mm incendiary rounds versus 40% full B-17 fuel tanks showed the chance of causing a fire per hit was 10% at 50 metres dropping to 2% at 2000 metres. Apparently a 13mm round's chance of starting a fire was 40% of the 20mm. Meaning the average number of hits to bring down a B-17 (and by implication other 4 engined types) would have been under the 18 to 20 figure, given the ones lost to fires.

The majority of B-17s lost were the result of engine failures, usually combat induced. Note the Luftwaffe gun combat footage showing the aiming point being on the wing. There was close to no armour around the engine or fuel tanks, just some protection for the oil cooler. And shooting at the wing reduced the chances of exploding the bomb load with the fighter too close.

The heavy armament fitted to the Luftwaffe night fighters is a powerful argument all the 4 engined types were harder to shoot down than their lighter counterparts.
 
Hitting an aircraft in a formation by head on attack without actually hitting the aircraft yourself gets more difficult as you think about whats involved. Wing mounted harmonised guns are not pointed in the direction of the aircraft longitudinal axis. In round figures a closing speed of 600MPH means 178 yards per second, you have to be aligned on the correct path before you can actually discern an individual target. Getting one hit is difficult, getting the required estimates of 3 x 30 mm or 20 x 20mm is close to impossible.
 

Target Berlin covered this in its recounting of the head-on attack on a formation of the 100th Bomb Group (although in that case the attack was highly successful).

Of course, a couple of 20mm or a 30mm shell into the cockpit, nose compartment, or front of an engine, is going to cause some trouble for that bomber.
 
Personally I don't have time for a lot of those video's simply because they are heavily biased towards entertainment instead of facts, a 30mm mine shell would cause at the very least a mission kill on a fighter but imagine trying to hit a Spitfire sized aircraft maneuvering hard at anything further than ramming distance.
 
Here's some background - the text which accompanied that photo on FB's 'PlaneHistoria' (I fianlly found it!)


'The incredible power of the German MK 108 30 mm autocannon is shown here on this Blenheim IV light bomber, which was hit by the weapon during British tests. Even the stoutly-constructed and rugged B-17 Flying Fortress was known to disintegrate when hit with as little as four MG 108 rounds, and the more lightly constructed RAF Lancaster and Halifax heavy bombers were even more susceptible to fatal battle damage from this weapon.'

To which I replied:

'can I see some evidence to back up the claim that the Lancaster was more lightly constructed than a B17? I find this slightly difficult to accept without clarification'

Reply
Rod Wylie
plenty of evidence around.
The Lanc was built light so as to carry large bomb loads.
Good read would be Lancaster Men by Peter Rees.


Me
Rod Wylie and yet it has an unladen weight almost the same as a B17 and is slightly smaller in all dimensions...? I'm crying BS


Jon Chapman
it was built differently, using a geodesic tubular steel design which had a very high strength/weight ratio, and was more spacious and could vary a higher volume as well as weight.


Rod Wylie
Or maybe'Big week' by James Holland

Me
Rod Wylie instead of digging yourself in even deeper, find me an extract from either book which refers to the Lancaster being 'lightly built' or more vulnerable to battle damage than contemporary four engined bombers.

Rod Wylie
Jeez , I'm a busy man.
Cant you read them yourself ?

Me
No, because there don't seem to be any [references online]. Someone with your self declared level of expertise and certainty should easily be able to dig those references out, eh?



... y'all know - the usual social media descent into snippy comments and replies (mea culpa!). But in all seriousness, has anyone ever heard anything to support this claim? As others have noted, Lancaster vulnerability would seem to be because of the nature of night fighting and context, NOT the airframe per se. As for 'lightly built', surely that is indeed just boll0c£s?
 
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PS - in addition to the above... I'm sure I remember reading somewhere that part of the Lancaster's strength derived from the original spec which included the capability of being catapult launched (I think this relates to short airfields rather than for naval employment and at a period when the RAF hierarchy were increasingly unsure how these ever heavier aircraft would get into the air unless runways were massively increased in length )

Is that false memory on my behalf, or maybe a since disproven myth?
 
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