1. AI do this automatically - i dno't know details. I know only:
- AI can launch helicopter when detect threat themself or from link
- Helo will land automatically when low fuel or take any damages (even 1%)
- AI can repeat helo launching
(but i test it long time ago so i cannot confirm this for current RA version)
2. Use active ping
Second option is to use HF sonar - for some submarines range is 3 nmi.
Third option is to use UUV or MOSS/Korund
I don't use TB-29 because i prefer higher tactical speed and aggresive style of playing. High speed gives you better chances for torpedo evasion. Aslo if you ping - enemy sub probably launch toprdo at you - so speed will also help you to avoid attack.
Of course TB-29 could be handy for slow ELINT missions - but i don't like this kind of scenarios. In MP sessions staying long time in the same place (or moving very slowly) is deadly option - especially if you play against player on surf + helo or MPA. Dececting slowly moving sub is only matter of time.