You're not hearing the Betty on sonar, you are hearing the torpedo they dropped at you!...
SJ could detect some air contacts, if they got low and close enough. The "band" is a pinch wide in SH4, but it has to be, since the game doesn't do the pitch and roll and "aiming" with the radar so well. We could narrow the band down more, so that it would be more like "real life", but then we would get complaints of "my SJ isn't working!" because as you go through the waves, the angle of the radar band going our shoots higher or lower from where the "targets" are...
