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RTCA to use NASA's analysis of aircraft-to-aircraft encounters to develop Minimum Operational Performance Standards for Unmanned Aircraft Systems
June 4, 2015

NASA's Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) project has been a key contributor to the consortium of government, industry, and academic institutions—RTCA Special Committee-228 (SC-228)—that is charged with developing regulations that establish Minimum Operational Performance Standards (MOPS) for safe and routine operation of UAS in the NAS. In particular, the Separation assurance/Sense and avoid/Interoperability (SSI) sub-project recently completed the most comprehensive study to date of aircraft-to aircraft encounters. The analyses, which captured the complexities of the aircraft encounters that exist in the current airspace and what could exist with the introduction of UAS, are necessary to perform an accurate evaluation of the level of safety that a Detect-and-Avoid (DAA) system must provide in order for UAS to safely and routinely operate in the NAS. NASA delivered its findings to the RTCA SC-228 Safety sub-group in May 2015 and the results will be included in an Appendix to the draft MOPS that is scheduled to be released in July 2015.

NASA researchers analyzed 21 days of aircraft-to-aircraft encounters (defined as events in which the proximity of two aircraft cause a pilot and/or DAA system to take action in order to maintain well-clear separation) originating from air defense radar data collected by the 84th Radar Evaluation Squadron (RADES) that cover both the interior and the perimeter of the continental United States. The radar data were replayed in the Airspace Concept Evaluation System (ACES), a NAS-wide simulation platform developed at NASA, which also modeled a set of proposed UAS missions that were developed jointly with industry and academic partners. Approximately 20,000 UAS flights were modeled per 24-hour period, covering eighteen different UAS mission types (e.g., cargo transport, fire monitoring, atmospheric sampling). The results establish the frequency with which a UAS DAA system may have to manage UAS well clear separation due to intruders, and also determines the types of encounter situations (e.g., converging, diverging, level) that may need to be mitigated, and their respective frequencies. Both types of results are necessary components being used by RTCA SC-228 to establish standards for UAS DAA systems. (POC: David Thipphavong, Marcus Johnson)

Motion Cueing Experiment at the Vertical Motion Simulator
June 4, 2015

The majority of commercial pilot training is performed in hexapod motion flight simulators (see Figure 1). Hexapod motion systems' performance parameters are often configured based on pilot opinion and can vary greatly between simulators of the same aircraft type. In addition, the Federal Aviation Administration (FAA) motion simulator certification is also subjective based on pilot opinion. To address these issues, the FAA and NASA have planned a series of experiments to develop objective motion cueing criteria for hexapod simulators.

Photo of the exteriors of the two hexapod motion simulators at CVSRF.
Figure 1: Typical Hexapod Motion Simulator

Photo showing the top view of the Vertical Motion Simulator and its motion platform.
Figure 2: Vertical Motion Simulator

From April 6 to May 29, 2015, the Motion Cueing 2015 Experiment (MCue2015) development was performed at the Vertical Motion Simulator (VMS) in preparation for the third MCue experiment, aimed at defining motion cueing guidelines to improve ground-based pilot training. The purpose of these studies are to define the boundary for acceptable hexapod system motion cueing based on three important flight maneuvers: 1) stall at high altitude, 2) one engine failure on takeoff, and 3) side step approach and landing. The large motion envelope, high fidelity motion and flexible system architecture make the VMS an ideal platform for motion cueing research (see Figure 2). A generic mid-sized twin-engine transport aircraft math model will be used for the upcoming study. The researchers intend to collect simulation flight data, performance data and pilot comments to help develop the FAA hexapod motion criteria to be provided to industry. (POC: Steve Beard)

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