Folks,

German U-boats of WW2 DID have active sonar..they just did not use it and it was eventually removed.

The type VII was fitted with active sonar in the mid 40 time frame.It was a revolving
transducer like the KBT mount seen later in the war.The reasons that it was removed later on and that we don't hear of U-boats using active sonar are as follows:

1. It was a 'trainable' device not an 'array' like the GHG so it had relatively short range...only 3000-4000 meters under good conditions. The passive GHG could hear an individual ship at around 20000 meters and a convoy at approx 100nm
(again these are under ideal conditions). An active 'array' would have given much greater range (probably out to 15000 meters).

2. Allied escorts could hear the active pulses and home in on them from well beyond the sonars effective range.

3. It was not as sophisticated as the 'Neiubling' system on the type XXI and was not linked into the U-boats fire control system like the 'Neiubling' was. This meant that it took a relatively long time to figure out a targets course/speed etc using the sonar...all the time transmitting and letting the escorts know where you are.
The XXI soanar needed as few as 3 pings to determine target speed/course which was fed directley to the fire control system allowing the tactic called 'deep directed shooting'. The tactics which where devised by test group 'Sultan' for the XXI were these. The target would be located at long range by the GHG and teh U-boat positioned on a interceot course. As the strength of the contact on the GHG
increased and the GHG operator thought that the target was withing 10000 meters the 'Neiubling' was switched on to 'listen only' mode. The system had a cathode ray screen to diplay all contacts and in 'listen only' mode it displayed ocean noise. When the propellor noise of the ship/s could be seen on the screen (as a regular series of spikes across the bottom of the screen - the beats of the propellor blades - the set was switched to 'active' and several pulses sent out.

4. As the allies increasingly used radar to spot surfaced U-boats the U-boats started carrying radar warning devices. The associated electronics cabinets had to go somewhere and the space used by the little used active sonar seemed like the ideal place.


I hope this helps..

sniper.