ASN Wikibase Occurrence # 293304
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| Date: | Sunday 24 July 2005 |
| Time: | 11:25 LT |
| Type: |  Brantly Helicopter B-2B |
| Owner/operator: | |
| Registration: | N9018Y |
| MSN: | 2002 |
| Total airframe hrs: | 191 hours |
| Engine model: | Lycoming O & OV-360 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Plymouth, Massachusetts -
 United States of America
|
| Phase: | Unknown |
| Nature: | Private |
| Departure airport: | Plymouth Municipal Airport, MA (KPYM) |
| Plymouth Municipal Airport, MA (KPYM) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While at a hover, the helicopter made an uncommanded sharp turn to the right, which could not be arrested with a left pedal application. When the helicopter completed approximately 3/4 of a rotation, the pilot "chopped the power" to stop the spin. The helicopter descended, struck the left skid on the ground, and then rolled over onto its left side. Examination of the intermediate tailrotor gearbox revealed that the tailrotor driveshaft was fractured at the input side of the gearbox. A portion of the fractured driveshaft remained in the flanged bushing of the gearbox. The fractured pieces of the driveshaft displayed significant mechanical damage from the driven end of the driveshaft after the fracture occurred. The driveshaft section recovered from the intermediate gearbox input bevel displayed multiple fatigue fractures with multiple origins around the attach-bolt holes. The fractures propagated from the attach-bolt holes in the direction of rotation, and opposite the direction of rotation. Fractured tail rotor vertical driveshafts from two previous events in the same make and model displayed almost identical modes of failure. As a result of those examinations, the FAA issued Airworthiness Directive 2006-08-07 on May 2, 2006, to help prevent fatigue cracking and subsequent failures of the vertical shaft.
Probable Cause: Fatigue failure of the intermediate tailrotor driveshaft, which resulted in a loss of directional control at a hover.
Accident investigation:
 |
|
Sources:
NTSB IAD05LA107
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 09-Oct-2022 18:30 | ASN Update Bot | Added |
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