ASN Wikibase Occurrence # 45991
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| Date: | Wednesday 28 February 2001 |
| Time: | 10:24 |
| Type: |  Bell 412SP |
| Owner/operator: | Care Flight |
| Registration: | N412SM |
| MSN: | 33197 |
| Year of manufacture: | 1989 |
| Total airframe hrs: | 5481 hours |
| Engine model: | P&W Canada PT6T-3B |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Grand Junction, CO -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Test |
| Departure airport: | Grand Junction, CO (29CO) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During a test flight, following maintenance on the helicopter, which required a functional flight check for vibration and autorotation, the helicopter was observed by witnesses to enter a rapid descent. During this maneuver, the rotor system was observed to slow down and the rotor blades to "fold" over the top of the helicopter. Pieces, which were later identified as fragments from the transmission cowling, were observed exiting the helicopter when the rotor system slowed down. The helicopter descended into the ground in a right hand turning maneuver. Examination of the wreckage revealed no evidence of either a structural or system failure or malfunction. According to the helicopter's manufacturer, as the main rotor system slows while under aerodynamic load, the main gear box can "walk" (horizontal orbital movement) on its mounting structure, which can result in contact between the transmission cowling and the main rotor control rod ends. Examination of the engines revealed evidence that engine power was applied when the rotor system was at low rotational speed. No evidence of preimpact engine failure or malfunction was found. According to available information, the pilot had received no training from the operator regarding the conduct of a maintenance test flight, not does the FAA require such training.
Probable Cause: the pilot's failure to maintain rotor speed during an intentional autorotation, which resulted in a loss of control.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20010320X00611&key=1
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 28-Oct-2008 00:45 | ASN archive | Added |
| 13-Aug-2010 15:07 | Alpine Flight | Updated [Operator, Other fatalities, Location, Nature, Departure airport, Destination airport, Source] |
| 06-Nov-2013 16:32 | TB | Updated [Operator, Source] |
| 21-Dec-2016 19:24 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 10-Dec-2017 10:32 | ASN Update Bot | Updated [Operator, Nature, Destination airport, Source, Narrative] |
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