A flight test system for the determination of the stability and control derivatives of a general aviation aircraft

Abstract

This volume documents the research effort which provided a flight test system and flight data to determine the stability and control derivatives for the Rockwell Commander N700AE aircraft. The presented research was conducted from June 1994 to May 1995. A set of data sensors was installed on the aircraft which measured time histories of aircraft states. These states included airspeed, altitude, relative-wind orientation, control surface deflections, linear accelerations, and angular velocities. The required sensors were designed or purchased and then installed, in-house. Calibration and testing of the sensors were performed. Existing avionics sensors were not "tapped" for data. A system for acquiring and processing the flight data was developed: a laptop computer was used which could interface with the data acquisition cardsand data sensors through a PCMCIA connection. Flight tests were performed to determine the response of the aircraft to different control inputs, atmospheric conditions and flight modes. Maneuvers were performed that would yield the most useful data for determining stability and control derivatives. Flight tests were performed for various airspeeds, altitudes, and aircraft configurations. Takeoff, landing, cruise and engine-out configurations were considered. Time histories of the aforementioned aircraft states were recorded for each of the proposed flight modes. Flight test data suitable for the extraction of stability derivatives was obtained on May 15 and May 19, 1995. Data acquisition throughput rates better than 145 samples/sec/chan were achieved. Relative-wind and control surface deflections were measured to an accuracy better than 0.17' and 0.09', respectively. Drift in flights lasting three hours was less than 0.2' for all relative-wind angles and all but one control surface angle (1.2' drift in rudder deflection angle). Noise levels were less than 1.3% of full scale angles. Linear accelerations were measured with an accuracy of 0.0007 g's with drifts less than 0.01 9 for all but one sensor (0.04 g for x-axis accelerometer). Acceleration noise levels ranged from 0.2% to 6. 1% full scale. Angular velocities as fine as 0.07'/sec were measured and drifted less than 0.12'/sec. Angular velocity noise levels less than 1% of full scale were observed. All these noise levels were based on raw measurements; no filtering was performed. The flight test system developed was reliable and robust with the exception of the pitot-static system. The data acquired was suitable for derivative extraction. Future efforts should include repair and calibration of the pitot-static system, installation of additional sensors, estimation of mass and inertial properties, and stability derivative extraction.