Low-Altitude Flight Performance as a Measure of Flight Simulator Fidelity

Abstract

Low-altitude flight performance was used to evaluate the effectiveness of the texture density cues used in high fidelity flight simulators. Observers were asked to maintain a constant above ground level (AGL) altitude over textured terrain whose elevation was varied. All combinations of two texture densities (0.13 and 0.43 elements/meter) and three airspeeds (50, 150, and 300 m/sec) were tested. Observers maintained a higher AGL altitude as speed increased, suggesting that higher optical flow rates interfered with the ability to maintain the target AGL altitude. However, when a single airspeed was used in a given block of trials, the effect of airspeed was eliminated, indicating that the original airspeed effect was due to perceptual averaging of the optical flow rate at each airspeed tested. Texture density was a significant factor only in the blocked-airspeed condition, suggesting that the blocking procedure eliminated measurement error that initially obscured the effect of this factor on altitude maintenance.