It has only 1 mode only, it is for landings and that is all. UA/PA does not change it, what it does is holds AoA not speed. Cruise is an odd place to use Auto-throttle.(it was not designed for that, but it is an interesting use for it) Flaps should always be full for landings, you set your AoA with gear down, hook down and full flaps, then engage Auto throttle and it should hold the AoA for the approach. Its performance should be identical to the F-14 in DCS Auto throttle where on approach it holds AoA and the pilot can make small stick inputs for the landing. It works extremely well in DCS F-14.