Why not PING me all the time?

[bluehedgehog]

In 3rd mission, destroyer chases me.

It pings me for some time, arrives over me, drops charges.
I evade and slip away.

But why doesn't the destroyer ping the sub all the time? Is there any downside to it?

Was that really the tactics in WW2?

How do you avoid pinging, e.g. lying close to bottom?

[olddriedseaweed]

Active sonar is directional. you need to be discovered passively and then the sonar operator pings your bearing to determine your depth to set the charges. As I understand it, active sonar limits the host warship to 15 knots, as above that speed the noise of the ship itself will drown out the return (wiser minds, please correct me if I am wrong) Also, there are blind spots in the active sonar array - 150 - 240 relative ????? Aft anyway, so after a run, the ship will lose you, regardless - hence the advantage of Hedgehogs.
While pinging away randomly may have some psychological advantages, it defeats the purpose.

[bstanko6]

You are correct seaweed. It is a useless measure to keep pinging. A ping takes time to travel to and from the uboat. If the escort is too fast, the return could be off quite a bit.

If there are two escorts, one will ping, while the other passively listens. If the other escort keeps pinging, it can throw off a listener, who is trying to identify machine noises in ambient sound.

And as you said, the device is directional, so at some point the ping is useless. The "pinger" will turn off his device, and let the "passive" listener keep track, so he can advise the next D/C runner if the uboat turned or is going fast, etc etc.