Raytheon COBRA incident near Whetstone, Arizona, September 24, 2008
On September 24, 2008 at about 3:41 pm local time, a Raytheon COBRA, registered N602RN, was destroyed in an incident during landing near Whetstone, Arizona (Unmanned Vehicles Intl airport). It was a flight test under general aviation rules (Part 91). No one was hurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 24, 2008 · about 3:41 pm local time
- Place
- Whetstone, Arizona · Unmanned Vehicles Intl · map
- Type
- Incident
- Injuries
- No one was hurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Raytheon COBRA
- Registration
- N602RN · no longer on the register · serial 002
- Damage
- Destroyed
- Flight
- Flight test · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (total) during enroute (descent)
- Attempted remediation/recovery during emergency descent
- Loss of control in flight during landing defining event
- Collision with terrain or object (not controlled flight into terrain) during landing
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › (general) › Failure
- cause Personnel issues › Action/decision › Action › Incorrect action selection › Pilot
- factor Aircraft › Aircraft power plant › Engine fuel and control › Fuel control/carburetor › Incorrect use/operation
- factor Aircraft › Aircraft power plant › Engine (reciprocating) › (general) › Incorrect use/operation
- Personnel issues › Task performance › Communication (personnel) › CRM/MRM techniques › Flight crew
Flight instructor
- Certificate: commercial pilot
- Ratings: single-engine land; instrument: airplane; rotorcraft: glider
- Flight time: 4,000 hours in all; 60 in this make and model
- Medical certificate: Class 2 (without waivers/limitations)
- Injury: no injuries
The aircraft
- Airframe total time: 26 hours
- Last inspection: condition inspection, January 31, 2008; 16 hours since
- Maximum gross weight: 110 lb
- Landing gear: fixed
- Engine: Desert Aircraft DA-150 (piston); 0 hours total
- Operator: Raytheon Company
The flight
- Departed from: Whetstone AZ at 3:09 pm
- Destination: Whetstone AZ
- Flight plan: none
- Runway 17, 2,500 ft by 50 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: at 1 knots
- Visibility: 70 statute miles
- Temperature: 70°F (21°C), dew point 41°F (5°C)
- Altimeter: 30.20 inHg
- Observation at 2:55 pm from KFHU, 10 miles away
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.