NTSB Identification: DCA12CA023
14 CFR Non-U.S., Non-Commercial
Accident occurred Monday, December 19, 2011 in McMurdo, Antarctica
Probable Cause Approval Date: 04/03/2013
Aircraft: UNIVERSITY OF KANSAS MERIDIAN, registration: None
NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.
On December 20, 2011, at 1517 local time (0317, December 19, Coordinated Universal Time (UTC)), an experimental Meridian unmanned aerial system (UAS), built, owned, and operated by the University of Kansas under a National Science Foundation grant, crashed on final approach to the Pegasus Ice Runway at McMurdo Station, Antarctica. The aircraft was substantially damaged, and there were no injuries or ground damage.
The aircraft was returning from a flight test in which the airplane was controlled via an over-the-horizon satellite (Iridium) control link. Approximately 60 seconds prior to the accident, the pilot took over direct control of the aircraft via 72MHz radio control (similar to a model airplane). On final approach, as the aircraft was commanded low power and nose down pitch, the aircraft lost the 72MHz link, and as programmed the flight control system switched to an autopilot Manual (Assisted) mode. The Manual (Assisted) mode commanded the aircraft to predefined “failsafe” settings of 100 knots airspeed and neutral controls, resulting in about 27 degrees of nose up pitch change. After about one second, the control mode was changed from the failsafe setting to the Home mode, which was inadvertently left latched due to a functionality test earlier in the flight. The Home mode commanded the airplane to climb toward the home waypoint, which was over the runway, and enter an orbit. The airplane was well below the home altitude and at low airspeeds for approach. The command resulted in a power-on stall and steep nose down descent. Radio control link was re-established but too late to recover from the stall. The airplane impacted the ice runway and was substantially damaged.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: an aerodynamic stall induced by an inadvertent autopilot Home command. The Home command was entered following a loss of the direct radio link due to improperly set failsafe settings, and an unintentional latching of Home mode from an earlier functionality test. Full narrative available
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