NTSB Identification: SEA07IA237
14 CFR Part 91: General Aviation
Incident occurred Friday, August 24, 2007 in Whetstone, AZ
Probable Cause Approval Date: 12/20/2007
Aircraft: Raytheon Co Cobra, registration: N605RN
Injuries: 3 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

Note: This case was reclassified from an accident to an incident as a result of applicable revisions to 49 Code of Federal Regulations Part 830.2, as amended at 75 FR 51955, Aug. 24, 2010. The case was previously identified under accident number SEA07LA237.

The unmanned aircraft system (UAS) was operating at a private airstrip used for UAS testing. The operation involved a ground-based flight crew of three pilots: a flight instructor, a student pilot, and a supplemental pilot. Additionally, an observer was present. The student pilot, who was being supervised by the flight instructor, was controlling the aircraft using the Pilot Console, which is a computer-based interface. Alternatively, the aircraft can be controlled through a Manual Pilot Console. While the accident aircraft was orbiting on autopilot, the Manual Pilot Console was used to control another aircraft that was involved in ground testing. In order to control the other aircraft using the Manual Pilot Console, the pilot address of that specific aircraft was entered using the Pilot Console. Also, the mode switch on the Manual Pilot Console, which switches between automatic and manual aircraft control, was placed in the manual position. Following the ground testing, the Manual Pilot Console was placed on a table with the switch still in the manual position and the pilot address still set for the other aircraft. All evaluations were completed, and the accident aircraft was readied for landing due to low fuel and approaching rain. Using the Pilot Console, the student pilot initiated the automatic landing sequence. The flight instructor's attention was distracted from the primary flight display by a request from the observer. Meanwhile, the student pilot noticed that the pilot address for the Manual Pilot Console was still on the address of the other aircraft. Without verifying that the mode switch was in the automatic position, he changed the pilot address to the address of the accident aircraft. Changing the address with the mode switch in manual position resulted in a disconnect of the accident aircraft's autopilot. Before the supplemental pilot could pick up the Manual Pilot Console and assume control, the aircraft, now in manual mode with the autopilot disconnected, rolled to the left, entered a vertical dive, and impacted the ground. As a result of the accident, the operator incorporated a software/hardware fail-safe making it impossible to change the pilot address for the Manual Pilot Console if the mode switch is in the manual position. The switch must now be moved to the automatic position prior to making the pilot address change.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The student pilot's failure to follow proper procedures, specifically not verifying that the mode switch was in the automatic position before changing the pilot address, which resulted in a loss of aircraft control. Contributing to the accident was the flight instructor's inadequate supervision of the student pilot.

Full narrative available

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