This work is sponsored by the Air Force under Air Force Contract No. FA8721-05-C-0002. The views expressed in this article are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government. The U.S. Air Force's RQ-4 Global Hawk unmanned aerial vehicle (UAV) is a high altitude, long endurance aircraft used for surveillance and reconnaissance. Because of the potential for close proximity to manned aircraft in civil airspace, collision avoidance is a major concern, and the Air Force is seeking to equip Global Hawk with the Traffic Alert and Collision Avoidance System (TCAS) to reduce the probability of mid-air collision. Currently, Global Hawk is equipped with a Mode S transponders and uses chase aircraft, ground observers and/or ground radar contact to comply with the collision avoidance requirement. In order to evaluate TCAS effectiveness, a fast-time simulation tool has been developed at MIT Lincoln Laboratory that computes the mean probability of a near mid-air collision for a large number of close encounters between two aircraft. Airspace encounter models enable sets of encounters to be simulated that are statistically representative of the aircraft encounters that actually occur in the airspace. The TCAS logic is implemented in the simulation tool and the aircraft responses during the encounters, with and without TCAS, are simulated in parallel. By observing measured vertical miss distance at the closest point of approach between the two aircraft, it is possible to quantify the reduction in collision risk provided by TCAS, termed the risk ratio. Global Hawk's flight characteristics differ from a conventional aircraft. Its mission profile through civil airspace includes slow, steep climbs and descents, and shallower turns than a conventional aircraft. Its vertical acceleration and climb rate limits can hinder its response to a TCAS resolution advisory (RA).
Safety Analysis of TCAS on Global Hawk Using Airspace Encounter Models
2006
67 pages
Report
No indication
English
Aircraft , Navigation Systems , Drones , Collision avoidance , Simulators , Quick reaction , Operational readiness , Mission profiles , Climbing , Transponders , Acceleration , Theses , Long range(Time) , Aerodynamic characteristics , Global hawk drone , Rq-4 drone , Tcas(Traffic alert and collision avoidance systems)
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