Pilot Debrief

RAYTHEON COBRA near Whetstone, AZ — 2008-09-24

Final reportDEN08IA160
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Date
2008-09-24
Location
Whetstone, AZ, USA
Aircraft
RAYTHEON COBRA
Registration
N602RN
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

A total off of engine power resulting from an overheated piston, and the pilot's subsequent failure to send a proper command to the UAS. Contributing to the accident was the operation of the engine at high power for an extended period with a lean fuel setting.

Contributing factors

Contributing to the accident was the operation of the engine at high power for an extended period with a lean fuel setting.

NTSB narrative

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 DEN08FA160. An unmanned aerial system (UAS) was flying a pre-programmed flight profile to test a mapping camera and telemetry package when it lost engine power. During the subsequent attempt to force land the aircraft on the runway, the UAS entered a commanded right banking turn and the aircraft descended,impacted desert terrain, and was destroyed. The aircraft had flown for approximately 39 minutes. During approximately 30 minutes of the flight, the aircraft's engine was operated at a high constant power setting of 5,300 RPM. An examination of the engine showed that one of the pistons overheated, expanded and rubbed against the cylinder wall, stopping the engine. The needle valves on the carburetor were set at a very lean fuel mixture which would contribute to the damaged piston. An examination of the autopilot software showed that during the attempt to put the vehicle into automatic landing mode, an improper command was sent by the operators.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Switching to manual control instead of following autopilot commands.

NTSB coding

  • Loss of control in flight · Landing

Evidence available

  • Photos
  • 21 docket documents
View NTSB final reportView NTSB docket

Docket documents21

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