A Piloted Evaluation of Damage Accommodating Flight Control Using a Remotely Piloted Vehicle

Abstract

Toward the goal of reducing the fatal accident rate of large transport airplanes due to loss of control, the NASA Aviation Safety Program has conducted research into flight control technologies that can provide resilient control of airplanes under adverse flight conditions, including damage and failure. As part of the safety program's Integrated Resilient Aircraft Control Project, the NASA Airborne Subscale Transport Aircraft Research system was designed to address the challenges associated with the safe and efficient subscale flight testing of research control laws under adverse flight conditions. This paper presents the results of a series of pilot evaluations of several flight control algorithms used during an offset-to-landing task conducted at altitude. The purpose of this investigation was to assess the ability of various flight control technologies to prevent loss of control as stability and control characteristics were degraded. During the course of 8 research flights, data were recorded while one task was repeatedly executed by a single evaluation pilot. Two generic failures, which degraded stability and control characteristics, were simulated inflight for each of the 9 different flight control laws that were tested. The flight control laws included three different adaptive control methodologies, several linear multivariable designs, a linear robust design, a linear stability augmentation system, and a direct open-loop control mode. Based on pilot Cooper-Harper Ratings obtained for this test, the adaptive flight control laws provided the greatest overall benefit for the stability and control degradation scenarios that were considered. Also, all controllers tested provided a significant improvement in handling qualities over the direct open-loop control mode.

Analysis of Control Strategies for Aircraft Flight Upset Recovery

“…In contrast to the fixed-point controller, C 1 ; the gainscheduled controller, C 2 ; attains good command tracking in all axes. A similar tracking performance was observed throughout the [2,28] degree range of angle of attack. For larger angles of attack, good V command tracking is not possible due to the reduced control authority resulting from a saturated throttle input.…”

“…Each of the fixed-point controllers comprising the gain scheduled controller attains good tracking performance near the corresponding linearization point. Furthermore, they make the equilibrium manifold shown above locally stable at each point in the [2,30] angle of attack degree range. The controller designed for 4.2 degrees used by both gain scheduled controllers is the very same C 1 .…”

“…Figure 1 shows the flight test article and its concept of operations. References [2,3,4] provide details on the vehicle's configuration and characteristics and the flight experiments. The aircraft is piloted from a ground station via radio frequency links by using onboard cameras and synthetic vision technology.…”

Subscale Flight Testing for Aircraft Loss of Control: Accomplishments and Future Directions

“…A summary of that evaluation task and the algorithms that provided damage-accommodating control is covered in Ref. 8. System identification and aerodynamic modeling studies have also been an important part of the research conducted with AirSTAR.…”

Nonlinear Dynamics of Aircraft Controller Characteristics Outside the Standard Flight Envelope

“…References [8,15,16] provide details of the vehicle's configuration and characteristics and the flight experiments. The aircraft is piloted from a ground station via radio frequency links by using onboard cameras and synthetic vision technology.…”