System identification of a small UAS in support of handling qualities evaluations

As small unmanned aircraft systems (sUAS) have moved from the domain of the hobbyist to the defense and commercial sectors, new procedures are required to quantify vehicle performance for a designated mission. This includes consideration of the verification, validation, and certification methods that will enable a safe introduction of the UAS into the National Airspace System (NAS). A significant portion of any certification effort in the traditional manned vehicle arena includes the evaluation of handling qualities, i.e., the stability and control traits that define the ability of a pilot to safely and effectively conduct the designated mission. In the context of sUAS, aircraft may be controlled by a remote human pilot, a semi-autonomous system with remote human oversight, or a fully autonomous system. Assessing the handling qualities of a vehicle, manned or otherwise, requires both an analytical evaluation process that predicts mission performance and a flight test process that verifies mission performance. As part of the analytical evaluation, vehicle models are examined using metrics that predict handling qualities. Flight tests are then conducted to verify and validate the predicted handling qualities. When discrepancies exist, model updates are made, based on the collected flight test data. In support of an ongoing UAS handling qualities development effort led by Systems Technology, Inc., system identification focused flight test data were collected for a small fixed-wing UAS. Multiple test conditions and excitation inputs were considered, and the resulting test responses were compared against analytical models. These models were then updated based on the flight test data analysis results. Finally, the revised model responses were compared to short duration input responses from the flight test sorties.