Abstract: This invention relates to pressure indicators, and more particularly to an improved pressure indicator whose use is especially advantageous in sensitive pressure altimeters in which high resolution and low friction are important.

Abstract: There is disclosed an annunciator for verbalizing altitude-related messages during the descent of an aircraft. Announcements such as "nine hundred," "eight hundred," etc. are made as the aircraft descends through respective "hundreds" levels; such announcements are not made during an ascent. In addition, the word "terrain" is heard when the aircraft descends through the 2,000-foot and 1,000-foot levels, and the word "minimum" is heard when the aircraft drops below a "decision height" selected by the pilot. Lastly, the word "glideslope" is out-putted in response to the detection of a glideslope deviation, the frequency of this announcement as well as its volume being a function of the magnitude of the deviation.

Abstract: An aircraft instrumentation having inherent self-checking features. Radar and barometric altitude information are displayed on the dial face of a single instrument. A cooperating dial and first pointer displays barometric altitude. A manually settable indicator "bug" cooperates with the dial to provide a presentation of the height of the airstrip relative to sea level. A second indicator "bug" of a different shape from the landing field bug is servo-driven from both radar and barometric altitude signal inputs to provide a presentation of aircraft altitude relative to the terrain beneath the aircraft. The angle between the barometric altitude pointer and servoed radar altitude "bug," measured counterclockwise, constitutes the distance of the aircraft above the airstrip or other terrain which the aircraft is passing over. Upon touchdown both "bugs" should be in exact coincidence, thereby serving as a self-check upon accuracy of the instrumentation.