Night visual approaches: Pilot performance with and without a head-up display

Simulated night visual approaches were flown into two airports with and without a head up display (HUD) in a transport aircraft. The HUD featured pitch stabilized vertical scales which displayed the glide slope angle to the runway aim point and a horizontal bar which aided the pilot in his control of the aircraft flight path angle. One airport was located on flat terrain with numerous foreground lights, the second airport had no foreground lights and the terrain sloped up behind the airport. With the HUD glide slope tracking precision was equally good for either runway. With no HUD glide slope tracking was about three times worse with the flat airport and about eight times worse with the airport with no foreground lights and up-sloping terrain beyond the runway.