Williams Helicopter CORP UH-1H accident near Grand Canyon, Arizona, November 15, 2011
On November 15, 2011 at about 3:37 pm local time, a Williams Helicopter CORP UH-1H, registered N502AW, was substantially damaged in an accident during enroute (cruise) near Grand Canyon, Arizona (Valle Airport). It was an other work-use flight under general aviation rules (Part 91). 1 person was seriously injured. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
The loss of main rotor power due to a main rotor transmission failure from a lack of lubrication.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 15, 2011 · about 3:37 pm local time
- Place
- Grand Canyon, Arizona · Valle Airport · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Williams Helicopter CORP UH-1H · all UH-1Hs on the register
- Registration
- N502AW · registry record · serial 69-15340
- Damage
- Substantial damage
- Flight
- Other work-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
According to the pilot, the helicopter was about 500 ft above ground level (agl) when he saw the master caution warning light illuminate; he then saw that the low transmission oil pressure light was also illuminated. He immediately maneuvered away from power lines and set up an approach to land. While descending, the helicopter yawed left and right, and, about 10 ft agl with the airspeed almost at 0, the main rotor speed slowed and then stopped, and the helicopter subsequently fell to the ground. The pilot reported that the engine continued to operate for about 15 seconds after impact. An on-scene examination revealed that both main rotor blades remained intact with no leading edge damage. Examination of the helicopter revealed a band of discoloration around the circumference of the transmission case near the main rotor reduction gear assembly; localized paint peeling was also noted. There were no oil stains or residue on the transmission case. During the subsequent transmission disassembly, the mast was found coated in metal debris along its length, and the mast bearing was found coated in oil. Molten metal pieces were found in the upper planetary gears, ring gear, and sun gear, consistent with insufficient lubrication. The lower planetary gears sustained significant damage from the molten metal pieces. There was no damage to the transmission oil pump, oil was present in the oil pump cavity, and some debris and scoring were evident on the housing. Examination of the passages within the transmission oil manifold revealed medium-to-high density particles in several of the passages, but none of the passages were blocked; particles were also found in the chip detector. The particles were identified as being generally composed of metals commonly used in gears, housings, and bushings. The damage to the transmission indicated that it likely seized as a result of an overtemperature condition due to a lack of lubrication. Due to the severity of the damage, the reason for the lack of lubrication could not be determined.
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
- Sys/Comp malf/fail (non-power) during enroute (cruise) defining event
- Off-field or emergency landing during emergency descent
- Hard landing during landing
The NTSB's findings
- cause Aircraft › Aircraft propeller/rotor › Main rotor system › (general) › Failure
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: helicopter; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 27,000 hours in all
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: unk
- Injury: serious injuries
The aircraft
- Seats: 15
- Landing gear: fixed
- Engine: Lycoming T53-L-13 (turboshaft); 0 hours total
The flight
- Departed from: 40G Grand Canyon AZ at 3:37 pm
- Destination: Supai AZ
- Flight plan: not recorded
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: a few clouds at 500 ft
- Temperature: 27°F (-3°C), dew point 25°F (-4°C)
- Altimeter: 30.09 inHg
- Observation at 3:03 pm from GCN, 25 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flig | 1 |
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number WPR12LA039.