Originally Posted by
Capn Bloggs
It's got nothing to do with pitch authority. One cannot "fly" an aeroplane, in the normal sense of the word, using the horizontal stabiliser alone. It doesn't react fast enough (unless it's an all-flying stab like a fighter).
Most trimmable horizontal stabs on modern airliners are all-flying, though. In fact the last-ditch control law on the Airbus FBW types is MAN PITCH TRIM ONLY, in which the pitch and rudder trim are the only way (other than differential thrust) to control the aircraft.
I've asked my friendly local aerodynamicist about the drag question - hopefully I'll get an answer shortly.
