Just how good was German Flak

[Jon]

Thanks Joe for the full answer.

So were Shells with proximity fuses still set to detonate at a given altitude but would overide and explode lower if they passed and aircraft.

[JoeB]

Originally Posted by Jon

So were Shells with proximity fuses still set to detonate at a given altitude but would overide and explode lower if they passed and aircraft.

They just had the proximity feature and a self destruct switch: a centrigually operated switch that opened a circuit when the shell started spinning at firing, charging up a capacitor, then closed when the shell's rotation speed decreased sufficiently, discharging the capacitor and detonating the shell. It was factory set according to assumed flight time before the shell got dangerously close to the ground. When VT fuzes were used around Antwerp over populated areas (usually fired out to sea defending England), the switch settings had to be changed at the factory to prevent proximity bursts against the ground when firing at the lower altitude flight profile the V1's adopted at that time. In naval use the fuzes would frequently detonate on sea return if they missed low altitude targets, before the self destruct activated.

A common USN practice was to fire mixed salvo's with some time fuzed shells, even after there were plenty of VT fuzes, to detect gross errors in the fire control solution if the time bursts were visibly far from the target.

Joe

[Jim Oxley]

The details below don't necessarily provide a guide to how effective German Flak was, but it certainly does give a guide to how thick it was.

In June 1944 the Flak regiments located within the borders of Germany deployed 8,876 guns of dreaded 88mm gun; 25,000 pieces of 20mm and 30mm cannon and were manned by 900,000 men.

That was a result of the bombing campaign by the RAF Bomber Command and 2nd Tactical Air Force, and the 8th and 9th USAAF.

To put those figures into perspective Rommel only had 35 x 88mm guns when he attacked the British in the Desert in 1941. The German Army in France only numbered 500,000 men at the time of the Normandy invasion.

[ArtieBob]

The basic WWII USN fire control system was the Mk 1, which was a mechanical analog computer. Solutions were good whether the inputs were from optics or radar and the aircraft true velocity was less than 400 knots. There were several problems, optical data on angular position could be very accurate, but optical ranging, particularly with a fast moving target was not as precise. Early radars because of the wavelength and lobe dimensions was sort of the opposite, more accurate in range, less accurate for angular position. So the best inputs were to use optical angular tracking if conditions permitted and radar ranging. But even with radar ranging, the margin for error in fuse setting is great because on a 5”/38 mount the fuse is set before the round is manually loaded. On the standard 5”/38 dual mount, this is done in the shell elevator which brings the projectile up from the lower handling room. If I remember correctly, the maximum firing rate for the twin mount is something less than 20 rounds per minute, or a cycle time of about 6 seconds per gun reloading, add to this the time in the elevator and the time of flight and you will end up with a 15 to 20 second lag between the setting of the fuse and detonation. If the target is manuevering, a time error of .1second would probably render the shell ineffective. If you have ever had the chance to see the movies of kamikaze attacks during WWII, the sky is obliterated by overlapping AA bursts, yet the aircraft just keep coming. The VT fuse eliminated the timing errors. IIRC in my gunnery classes, the USN felt the effectiveness was increased by a factor of 5.

Best regards

Artie Bob (ex-second loader 5”/38 mount (lower handling room)