Flight Evaluation AN/APN 191 Radar Altimeter.

Abstract : A flight evaluation of the AN/APN 191 radar altimeter was conducted to determine its accuracy and suitability as a test instrument. The testing consisted of 9.7 flight hours with the altimeter system installed in a UH-1C helicopter. Results show that the AN/APN 191 altimeter system has a large random error and is not as accurate as present altitude determination methods. Therefore, this altimeter is unsatisfactory as a test instrument. The indicator scale and sensitivity were excellent; and the accuracy was not affected by attitude, vertical speed, or airspeed variations. (Author)