RANDOM DEVIATIONS FROM STABILIZED CRUISE ALTITUDES OF COMMERCIAL TRANSPORTS AT ALTITUDES UP TO 40,000 FEET WITH AUTOPILOT IN ALTITUDE HOLD

摘要

The random deviations from stabilized cruise altitudes of 19 commercial transports on scheduled, passenger-carrying flights at altitudes up to 40,000 feet have been evaluated from NASA VGH records. The airplanes represented 10 aircraft types of which 4were turbojets, 3 were turboprops, and 3 were piston engines. They were operated by nine United States airlines for a period of about 1 year over both land and ocean routes covering 9，950 hours of cruise time.nThe results of the "evaluation showed that the airplanes flew within 200 feet of their stabilized cruise altitude for at least 99.5 percent of the cruise time for operation with autopilot in altitude-hold control and for at least 94。5 per¬cent of the cruise time for operation with manual control. For 0.3 percent of the cruise time, the altitude deviations from stabilized cruise altitudes for operation with autopilot in altitude-hold control did not exceed 250 feet for any of the airplanes over the altitude range up to 40,000 feet.