Abstract: A terrain advisory system for an aircraft (A) comprises a processor (11) which compares terrain information, accessed from a memory (13) according to data from a navigation system (12), with dynamic flight parameters from a monitor (14) for the aircraft. The processor (11) also generates a trajectory signal and a pull-up signal to indicate, on a display (15), current aircraft trajectory relative to a line constructed from notional pull-up trajectories for the aircraft which avoid a predetermined clearance height without exceeding a predetermined acceleration acting on the aircraft during a pull-up maneuver.