Thanks for this. Yes the 412 has no heading hold. My thought process was that the SAS works on providing a opposite force to a roll / pitch rate induced due to wind or (pitch and roll on deck) to try and minimise disc movement caused due to this external stimulus. The ATT mode on the other hand holds the disc attitude in position. But on deck which is heaving, does one want the AFCS in SAS mode to provide these opposing forces to minimise the roll/pitch rate ? Why not just let the force trim do its job of holding the disc. Why allow the AFCS to provide inputs to the disc
Not so much an opposite force in pitch/roll but a rate damping effect between pilot control input and the AFCS output to the rotor to improve handling qualities.
Having said that, the gyros don't know the difference between the aircraft movement and the boat movement so you are probably better off taking out the AFCS if the deck is moving a lot and you will be on it for more than a few seconds.
Just don't forget to put it back in before take off!!
