I my opinion, the only way to use sonar autocrew is with TMA auto also, because the AI marks EVERYTHING (sometimes even things that you are unable to see), and if you make manual TMA with sonar autocrew you will become cracy merging and dropping contacts.
And worst of it: that ship classified by the AI as a freighter... sudently is a submarine! general quarters, general quarters!! all hands... wait... no, is a fishing boat... no, an Oscar!!... no... a torpedo??...
I agree with LuftWolf about using autocrew only on active intercept and radar.
