In support of NASA's Unmanned Aircraft Systems Integration in the National Airspace System project and RTCA Special Committee 228, an analysis has been performed to provide insight in to the trade space between detect and avoid (DAA) Well Clear definition threshold variations, which could affect DAA sensor range and alerting requirements.
I. NomenclatureCPA = closest point of approach deg = degrees = range in the x-dimension = range in the y-dimension dh = vertical separation DMOD = distance modifier ft = feet h = vertical separation threshold HMD = horizontal miss distance KCAS = knots calibrated airspeed KTAS = knots true airspeed r = horizontal range ̇ = horizontal closure rate sec = second = time to closest point of approach (CPA) ℎ = time to achieve vertical separation = modified tau = relative velocity in the x-dimension = relative velocity in the y-dimension
II. IntroductionThe integration of unmanned aircraft systems (UAS) into the U.S.' National Airspace System (NAS) is highly desirable to many stakeholders across government, industry, and academia; maintaining the same level of safety as is currently in the NAS requires a means of replacing the manned aircraft pilot's obligation to see-and-avoid other aircraft [1]. RTCA Special Committee 228 (SC-228), a federal advisory committee consisting of public and private stakeholders, is developing minimum technical requirements for a detect-and-avoid (DAA) system to be used in lieu of a manned aircraft pilot's see-and-avoid capability. A DAA system uses a suite of sensors, trackers, detection algorithms, and display to provide the remotely located pilot with sufficient awareness to avoid a loss of separation with other aircraft. SC-228's recently published minimum operational performance standards (MOPS) for DAA systems are outlined in , while the accompanying MOPS for air-to-air radar are outlined in . To make the problem more manageable, DO-365 and DO-366 were necessarily developed to support a limited set of UAS performance and operations. Ongoing work is intended to enable more types of UAS and support more complete operations.