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Old 31st May 2005, 18:22
JoeB JoeB is offline
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JoeB
Re: Just how good was German Flak

Quote:
Originally Posted by Jon
One further question on Proximity fuses, how close to the target did they have to be for the fuse to detect and detonate?
The VT fuzes of WWII worked on prinicple of doppler shift continuous wave signal. IOW they didn't directly measure the distance to the target like a pulsed radar. The main tuning variable for distance was sensitivity. When the shell got near a target the doppler shifted return signal superimposed on the o outgoing signal would form a "chirp" in the circuit that triggered the fuze. But the reflectivity of the target also mattered.

Empirical tests were used to set the sensitivity. The first generation 5"/38 fuze Mk.32 which entered combat in Jan 1943 had that done by subscale tests. Full scale tests (against various real planes suspended from cables, the B5N "Kate" was mostly used but Allied bomber types were tested too) were done after those fuzes entered service. The typical bursting distance was 70-100' in practice. From "Deadly Fuze" by Baldwin.

The VT fuze raised the effectiveness of USN AA fire an estimated 3 fold in 1943 over time fuzes, later fuzes (similar to the ones used in 3.7" and 90mm AAA in Europe) 4 fold. And USN directors and radars were pretty sophisticated at least equal to German in late war period (so were Army ones), and the main naval weapon a high ROF 5" probably more effective as a basic AA gun than all but the German 128mm, which was rare. And of course the USN had plenty of experience shooting at planes by later war. IOW the best late war Allied heavy AAA was probably several times more effective than German. Had German AAA been as effective it would have been a major problem.

OTOH postwar when evidence of Soviet VT fuzes was detected, very similar to early US ones, a fuze jammer was rapidly developed, likely the same if Germans introduced it, and another ECM/ECCM seesaw would have ensued, though German VT fuzes still would have been bad news without doubt. VT was used against German manned a/c fairly infrequently and late, and their operations research function of detecting new enemy weapons wasn't (obviously) as strong as the Allies, so AFAIK they never realized it. The Japanese had VT fired at them for 2-1/2 years and apparently never realized it.

The Westermann book also points out how very widespread fitting of active jammers to USAAF bombers, though it didn't happen till the fall of 1944, had a big impact on the flak arm, interestingly not so much reducing losses as forcing the Germans to radically increase shell consumption and barrage fire.

Joe
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