Definition of "glideslope"

The constant angle of descent technique requires pilots to maintain a predetermined constant angle and constant rate of descent, which is generally calculated to be about 3°, except when terrain or an obstacle necessitates a steeper descent. When a ground-based glideslope signal is absent, pilots can fly the constant angle of descent approach by using flight management system (FMS) and GPS equipment for electronic guidance.

2000, National Transportation Safety Board, “1.17.4.2 Flight Crew Actions and Callouts During Nonprecision Approaches”, in Aircraft Accident Report: Controlled Flight Into Terrain, Korean Air Flight 801, Boeing 747-300, HL7468, Nimitz Hill, Guam, August 6, 1997‎, archived from the original on 18 February 2021, page 64