Evaluation of Barometric Altimetry at Low Altitude

摘要

An evaluation was conducted to determine the mean and standard deviation of errors in determining a height of 100 feet above the runway by utilizing the barometric altimetry systems aboard the Federal Aviation Agency Boeing 720 (N-113) and Convair 880 (N-112) on Instrument Landing System (ILS) approaches. Operational altimetry system errors were determined by taking the difference between altimeter indicated height recorded by airborne cameras and aircraft altitude recorded by phototheodolites. Corrections for the altimeter setting error and the flight manual value of the error of the static system were applied to the operational altimetry system error to obtain the calculated altimetry system error. Based on the results of the evaluation, it was concluded that a height of 100 feet could have been determined during descent to an average standard deviation of 5.2 feet and 7.7 feet for the Boeing 720 and the Convair 880 respectively, and during level flight to an average standard deviation of 6.5 feet and 8.4 feet for the Boeing 720 and the Convair 880 respectively, provided the barometric altimetry systems were corrected by the amount of the mean error for each case. (Author)