Hi All,

The detonators in depth charges were pressure activated as opposed to timed.

For the first few years of the war ASDIC (sonar) could only tell the bearing & approximate distance to a target but not its depth. The depth charge settings were simply a guess and some charges were set deep, some in the middle & some shallow in order to have the best chance of actually coming close to the U-boat. They also sank at a known rate & the U-boat could hear them hitting the water & maneuver to avoid them. Also at the beginning of the war the depth charges couldn't be set to detonate at the deepest depths a U-boat could operate at.

Later in the war ASDIC was able to determine the target's depth. They also increased the depth they could detonate depth charges at and increased the rate of sinking to give the U-boat less time to maneuver to avoid them. Even later than that ASDIC was able to feed the depth info directly to the depth charges just before they were launched. I believe SQUID had the depth set automatically from sonar like this.

Regards,

Ken Dunn