Description: Both autopilot systems and human pilots, particularly human pilots operating in instrument meteorological conditions, rely heavily on sensor feedback to safely control aircraft. The loss of reliable information for even a single state feedback signal can easily initiate a chain of events that leads to an accident. Even when hardware redundancy is employed, common-mode failures are a significant hazard that can make hardware redundancy ineffective for achieving the desired system reliability. For example, multiple pitot tubes can experience a common-mode failure during an icing event, depriving the pilot of vital airspeed information. The proposed virtual redundancy approach can significantly improve flight safety by identifying failed sensors and estimating the correct output values as replacements for those failed sensors. Estimates are based on a rigorous statistical formulation that makes optimal use of all available information including feedback from all remaining physical sensors, nonlinear models of vehicle dynamics, and models of actuator and sensor responses. The proposed research will also develop strategies for enabling pilots to make effective use of the virtual sensor outputs, including guidance algorithms that identify a trajectory that maximizes the likelihood of maintaining safety of flight and cueing techniques that allow the pilot to follow the resulting trajectory while minimizing the increase in workload.

Benefits: The proposed innovation directly addresses several key needs identified under the Aviation Safety Topic, particularly with regards to safety assurance under unanticipated conditions. The proposed technology is designed to assure the integrity of information required for safe aircraft operation in the presence of multiple sensor failures. It utilizes information from all available sensors and high-fidelity models of the aircraft system to detect, isolate, and mitigate sensor failures in real time. In addition, it incorporates real-time flight safety management components to evaluate flight safety risks associated with the particular failure scenario, determine an optimal response to ensure a margin of flight safety, and provide pilot cueing to enforce those safety margins.

For potential non-NASA commercialization, Barron Associates will pursue additional development funding from other agencies and DoD to help further advance the technology. Then, once high TRLs are achieved, we will team with industry partners, makers of unmanned air systems, large airframers, and sensor manufacturers to develop integrated software/hardware sensor suites that include the developed virtual sensor tools. This will lay the foundation to pursue marketing avenues of the technology in the aerospace industry, including manufacturers of unmanned aircraft, military aircraft, and both commuter and large commercial transport aircraft. At the same time, we will pursue other industries where application of fault detection, isolation and recovery are critical for ensured safety of operations, such as the nuclear power industry, mass transit control, and medical devices and systems.