L-1011 Autoflight: Glideslope Capture and Track (22-31)

Glideslope capture cannot be initiated until after localizer capture is initiated, but localizer track status is not a pre-capture requirement. Nearly simultaneous capture of localizer and glideslope is poossible. The glideslope is normally captured from below the beam, but it can also be captured from above using vertical speed as pitch pre-capture guidance. When glideslope capture starts, the GS ARM annunciation changes to GS, and the pre-capture pitch mode is released, removing its annunciation on the AFCS MODES panel. A glideslope capture timer also start with initiation of glideslope capture.

When 25 seconds have elapsed on the glideslope capture timer and the glideslope deviation is 1/6 dot or less, the status changes from glideslope capture to glideslope track. This change in status it not annunciated. When these conditions have been satisfied, a glideslope gain change takes place reducing sensitivity of the autopilot/flight director system by 75 percent. This gain change is to partially compensate for glideslope beam convergence as the airplane approaches the transmitter.

Direct Lift Control (DLC) becomes active when the flap handle is moved through the 30 degree position.