If I am zipping along in TC and I get a Radar warning, TC will drop out to normal time (or sometimes 8x depending on the situation), if I choose to ignore it and recrank up TC and bash on, guaranteed I'll get nailed by an aircraft almost everytime. In this case it is not the game's fault but mine as I ignored the preliminary warning. I've learned to go to periscope depth if I get more than one Radar warning in a short space of time, if hydro doesn't pick up anything then it'll probably be an aircraft and I'll continue my cruise underwater until dark (accelerated TC).
Short answer therefore is: Ignore Radar warnings at your own peril, if you're zipping along in TC.
