B-17 Saved By...

this page http://www.navweaps.com/Weapons/WNGER_20mm-65_c30.htm gives the maximum height of one of the German 20mm as 12,000 feet. Holding the weapon on target long enough to put 11 rounds in from a ground based AA seems really iffy to me though. Almost impossible to do without getting a lot of other hits around the tank. Although if it were at or a bit over "max altitude" that could explain the lack of penetration pretty well.

 

Just doodling with the numbers.

Assume 500 rounds per minute and 2000 feet/second velocity.

Thats .12 seconds between shots. 2000 ft/second x .12 seconds = 240 feet. So each projectile was 240 feet behind the one in front of it. The cannon was probably firing somewhat less than 500 rounds a minute and the velocity was probably higher so they would have actually been more widely spaced.

Say the plane was going 150 MPH, that's 220 feet a second.

So we have 11 shots, each 240 feet apart hitting a 5 foot square fuel tank moving at 220 feet a second.

That would be hard to do, I think

 

Hitting the area of a wing tank, without hitting other parts of the Fort would damn impossible even if the plane were close to the ground, say 2,000-3,000ft altitude. So, I say that theory is out.

The only thing I could think of to explain how this happened, IF it happened, was that a night-fighter with a "jazz music" installation infiltrated the bomber formation and fired its upward firing 20mm MG FF cannon at close range into the bottom of the plane's wing. How could this have happened, since ME-110s and JU-88s are rather conspicuous? It seems pretty far fetched but I know in the fall/winter/spring of 1944-45 the weather over the continent was unusually bad and sometimes it was bad enough that we had to use British blind bombing techniques. It just could be possible that a night-fighter, using clouds for cover snuck up on a bomber in a lower formation without being seen and gave the Tondelayo a squirt. (The MG FF cannon shells had a considerably less velocity than the later model of German 20mm cannon, the Mauser MG 15/20.)

However, also on further reflection, I have some trouble with the sabotage theory. Having a whole bunch of explosiveless shells in one batch could easily have been traced back to the point of manufacture. The result would probably have been a bunch of Czech workers decorating nearby trees. It would have been extremely risky for foreign workers to try the wholesale sabotage of HE projectiles.

 

I've seen this story a few times as well, but every time I read it in different places, it was ONE round in the gas tank, not 11. Perhaps a total of 11 throughout the aircraft.