Abstract: An altitude preselect apparatus for use with or incorporation into an automatic flight control system combines the incremental altitude signal from a pneumatic encoding altimeter with a vertical speed computation to generate a smooth, continuous instantaneous altitude signal. A vertical speed reference signal is generated to control the vertical flight path of the aircraft when the instantaneous altitude reaches a prescribed proximity to a desired flying altitude which is manually selected by the pilot. The apparatus initiates a capture sequence to hold the aircraft at the desired altitude once it is reached.

Abstract: Apparatus for use with an area navigation system wherein the craft is maintained on a predetermined vertical flight path. Specifically, a pitch command signal for controlling the vertical flight of the craft, which is substantially free of discontinuities, is produced by summing a signal indicative of the vertical displacement of the craft from the flight path with a damping signal representative of the vertical deviation rate of the craft from the vertical velocity required to maintain the craft on the flight path. Additionally, the vertical displacement signal is limited to a maximum amplitude to compensate for discontinuities therein, with respect to passage of the craft through the vicinity of a VOR/TAC station.