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ASN Wikibase Occurrence # 166005
Last updated: 18 November 2021
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Date:03-MAY-2014
Time:11:30
Type:Silhouette image of generic B407 model; specific model in this crash may look slightly different
Bell 407
Owner/operator:Classic Medical Inc
Registration: N407MH
MSN: 53100
Fatalities:Fatalities: 0 / Occupants: 3
Aircraft damage: Substantial
Category:Accident
Location:Lizard Head Pass, San Miguel County, CO -   United States of America
Phase: Landing
Nature:SU
Departure airport:Moab, UT (MOB)
Destination airport:Telluride, CO
Investigating agency: NTSB
Narrative:
The commercial pilot and two flight crewmembers were conducting a search and rescue mission for a local sheriff's department in the helicopter. The pilot reported that, after flying five or six lines of the search grid and while in a right turn to begin flying another line of the grid, the engine noise changed. Immediately thereafter and while the helicopter was 200 ft above ground level, the engine chip detector light illuminated, followed by a full authority digital electronic control degrade light. The pilot started to descend toward an open snow-covered meadow for landing, but the engine rpm degraded, so he initiated an autorotation. The helicopter touched down with little forward airspeed and bounced, and the left skid then became caught on an object under the snow. The helicopter rolled onto its left side and then came to rest.

A postaccident examination of the engine showed that the engine gas producer and power turbine drive train had continuity, but there was resistance to the gas producer and scraping of the power turbine when rotated. Further examination of the engine revealed that the gearbox cover had been modified by a repair, which included an insert being threaded into the oil delivery tube port. The insert was blocking the oil flow to the power turbine thrust (No. 5) bearing, which resulted in the bearing overheating and failing due to the lack of lubrication and the subsequent engine failure. No records were found regarding any repair to the gearbox cover oil delivery tube port.
Probable Cause: The failure of the power turbine thrust (No. 5) bearing due to overheating as a result of oil starvation, which led to the engine failure. Also causal to the accident was an undocumented repair to the gearbox cover oil delivery tube port during which an insert was threaded into the oil delivery tube port that subsequently restricted the oil flow to the power turbine thrust bearing.


Sources:

NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=407MH

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration:
Download report: Final report
Location


Revision history:

Date/timeContributorUpdates
05-May-2014 10:17 Útila Added
05-May-2014 10:18 harro Updated [Aircraft type, Location, Nature, Source]
05-May-2014 22:31 Geno Updated [Time, Registration, Cn, Operator, Total occupants, Phase, Source, Damage, Narrative]
06-May-2014 06:13 Anon. Updated [Total occupants]
08-Oct-2014 13:51 TB Updated [Operator, Location, Departure airport, Destination airport]
12-Aug-2016 17:54 Aerossurance Updated [Time, Operator, Location, Source, Narrative]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 14:22 ASN Update Bot Updated [Operator, Total occupants, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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