ASN Wikibase Occurrence # 222635
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| Date: | Tuesday 5 March 2019 |
| Time: | 12:10 LT |
| Type: |  Hughes 369D |
| Owner/operator: | Rotor Blade LLC |
| Registration: | N89ZC |
| MSN: | 1098D |
| Year of manufacture: | 1981 |
| Total airframe hrs: | 13667 hours |
| Engine model: | Rolls-Royce 250-C20B |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Talking Rock, Pickens County, GA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Agricultural |
| Departure airport: | Talking Rock, GA |
| Talking Rock, GA | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter pilot was using an aerial saw to trim trees along power lines. A witness reported that the pilot performed one pass, then returned for the second pass when the helicopter began to spin counterclockwise around its main rotor mast. During the second rotation, the helicopter impacted trees and terrain before coming to rest on its right side. Postaccident examination revealed a fracture of the overrunning clutch outer race and cracks on three of the engine mounts. While two of the three engine mounts cracks were likely a result of impact forces, the cracks on a third engine mount were likely present prior to the accident. The failure of the overrunning clutch subassembly outer race resulted in a loss of power to the main rotor system. Given the helicopter's low altitude and airspeed at the time of the loss of power, the pilot was likely unable to successfully initiate and perform an autorotative landing.
Before its installation onto the helicopter, the overrunning clutch subassembly had been repaired, which included the installation of a new outer race. The accident helicopter operated with the overrunning clutch subassembly for about 33 flight hours until the accident occurred. Examination of the fracture surfaces revealed signatures consistent with fatigue and subsequent overload. The orientation of the crack in the circumferential plane was consistent with an anomalous bending load, such as an angular misalignment of the drivetrain, that drove fatigue crack initiation.
Directionality of the deformation and fracture of the center engine mount was primarily in the vertical direction and the fracture surfaces exhibited evidence of oxidation, indicating that the cracks were present before the accident. Therefore, it is likely that the damaged center engine mount was the source of the anomalous bending loads that led to fatigue crack initiation and subsequent failure of the overrunning clutch outer race.
The 100-hour/annual inspection of the engine mounts could be performed with the engine installed on the airframe, and the operator had done so; however, the presence of the engine could present difficulties for a mechanic in performing a visual inspection, particularly of the forward side of the center engine mount, where the cracks were located. Maintenance records indicated that, in the 9 months preceding the accident, the engine mounts were inspected six times with no anomalies observed. However, when the engine mount cracks may have developed and whether they would have been visible during any of the previous inspections could not be determined based on the available information..
Probable Cause: A fatigue failure of the overrunning clutch subassembly due to abnormal bending loads due to cracks on the center engine mount, which resulted in an inflight loss of power. Contributing to the accident was the helicopter's low altitude and airspeed when the loss of power occurred, which precluded the pilot from successfully performing an autorotation.
Accident investigation:
 |
|
Sources:
NTSB ERA19FA118
History of this aircraft
Other occurrences involving this aircraft
| 6 November 2009 | N89ZC | 0 | Baxley, Georgia | |
sub | |
| CFIT | ||||||
| 29 July 2014 | N89ZC | Rotor Blade LLC | 0 | Logan County, between West Liberty and Bellefontaine, Ohio | |
sub |
| Fuel exhaustion | ||||||
| 22 August 2018 | N89ZC | Rotor Blade LLC | 0 | Ridgeway, Pennsylvania | |
sub |
Location
Images:
Photo: NTSB
Media:
First video from Pickens County helicopter crash courtesy sheriffs office. Pilot air lifted to hospital. He apparently collided with a tree. Updates to come. pic.twitter.com/oJEaD7tEcs
— Tom Regan (@tomreganWSB) March 5, 2019
4th accident to this H369D proved fatal. #NTSB identify that undetected prior engine mount damage led to clutch failure while using an aerial saw at low level. https://t.co/y1F6PFiBdn #helicopter #accident #flightsafety #aviationsafety pic.twitter.com/Dca35dpMsV
— Aerossurance (@Aerossurance) February 27, 2021
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 06-Mar-2019 07:41 | gerard57 | Added |
| 06-Mar-2019 07:57 | gerard57 | Updated [Narrative] |
| 06-Mar-2019 08:23 | RobertMB | Updated [Aircraft type, Registration, Cn, Operator, Location, Source, Narrative] |
| 08-Mar-2019 03:19 | Aerossurance | Updated [Embed code] |
| 22-Mar-2019 18:23 | Heloguy | Updated [Time, Operator, Source, Embed code, Narrative] |
| 27-Feb-2021 10:30 | Aerossurance | Updated [Time, Source, Embed code, Narrative] |
| 27-Feb-2021 10:31 | Aerossurance | Updated [Embed code, Narrative] |
| 29-Mar-2021 18:45 | ASN Update Bot | Updated [Time, Other fatalities, Nature, Departure airport, Destination airport, Source, Embed code, Damage, Narrative, Category, Accident report] |
| 29-Mar-2021 18:57 | harro | Updated [Nature, Source, Embed code, Narrative, Photo] |
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