WEEK 13
H2F brings you the ‘helicopter mayday of the week’ with a short accident report summary. I tell you what happened. You think more about why it happened. We all learn from it. Because that’s what accident reporting is for.
TITLE
Engine failure and failed autorotation.
WHAT?
A Bell UH-1H helicopter operated by the Bernalillo County Sheriff’s Department was returning to base after conducting firefighting missions. While cruising westbound at about 500ft, the helicopter entered a descent that rapidly increased to more than 5,000 ft per minute and impacted terrain in a tail-low attitude.
WHERE?
Near Chapelle, New Mexico, in high desert terrain.
WHEN?
July 16, 2022, close to sunset.
HOW?
The helicopter was flying level at 133 knots before entering a rapidly increasing descent. Witnesses observed it descend and impact the ground without turning. 17 flight hours before the accident, an engine chip had occurred. Maintenance personnel drained and flushed the oil system but no laboratory analysis was done to find the source of the metal. On this flight, the single engine helicopter suffered total engine power loss and entered autorotation, but the descent continued without a flare or check, culminating in ground impact.
CONDITIONS?
Weather was VMC with 10-mile visibility and light winds, however, the density altitude was over 9,000ft. At 500’, the aircraft was operating at relatively low height, reducing available time to respond to a sudden engine failure. Furthermore, the flightpath was into the setting sun, which may have affected visual cues during the short autorotation.
OUTCOME?
The helicopter was destroyed on impact. The pilot, two tactical flight observers, and a rescue specialist sustained fatal injuries. No post-impact fire occurred.
WHY?
- Examination revealed that the starter-generator input gear failed due to fatigue, shearing a driveshaft and seizing the accessory gearbox, leading to a total loss of engine power.
- Failure to use lab analysis troubleshoot a previous engine chip event.
- Poor maintenance monitoring practices of the deteriorating component.
- Pilot’s unsuccessful autorotation following the engine failure. (The pilot had accomplished autorotation training during his previous annual flight check but not in this type).
- Environmental factors complicated the autorotation, including high density altitude and flight into setting sun.
REFERENCE?
National Transportation Safety Board. (2024, June 12). Aviation investigation final report: Accident number CEN22FA317 (Bell UH-1H, N911SZ). National Transportation Safety Board. https://data.ntsb.gov/Docket?ProjectID=105488
https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105488/pdf
Note:
Accident reports selected from the following open source databases: US NTSB; UK AAIB; Flight Safety Foundation’s Aviation Safety Network; Australia’s ATSB. Ireland’s AAIU; Taiwan’s TTSB; France’s BEA; Spain’s CIAIAC. Germany’s BFU.
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