Is there a difference? Yes.
In basic terms it (VNAV) does what it says on the tin:
VNAV SPD: the elevators control the pitch attitude of the aircraft to control speed.
VNAV PTH: the elevators control the pitch attitude of the aircraft to follow a programed vertical path, (e.g. to cross a waypoint at a altitude/Flight Level programmed into the FMC).
Last edited by wiggy; 10th Jul 2009 at 06:44.