alex ford
I have never flown the F27. But I have flown a very nice jet that had airspeed hold.
The autopilot will change pitch in order to maintain selected airspeed. It has no control over the throttles.
A good use for this is climbing at a selected airspeed. At some point you will climb so high that if you selected a rate of climb, the plane would stall.
So, you select a speed and at some point in the climb you would not climb anymore but you wouldn't stall.
While You would NOT select airspeed hold in level flight you could , but the ride would be an oscillation and has no good reason UNLESS you are trying to hold rough air speed and are willing to be off altitude. And in really rough air I would use PITCH hold if you have it.
You would select airspeed hold if both engines quit and you wanted to maintain the best glide speed.
You could close the throttles and descend at a selected airspeed and the rate of descent would vary in order to maintain the speed.
The F27 is an old plane. Think old and you will see why so many old pilots hand flew so much! And they got good at it.
If you lost one engine and had to maintain V2, speed hold might help (I am not sure what your limitations section allows).
So, again. NO throttles. ONLY pitch and that's all she wrote.
OH, on my older plane we also had MACH hold for the times we were in mach land, but I have a feeling the F27 never got close to mach land