Pilot Debrief

ENSTROM F-28C-2 near Blair, NE — 2011-06-23

Final reportCEN11LA414
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Date
2011-06-23
Location
Blair, NE, USA
Aircraft
ENSTROM F-28C-2
Registration
N5694A
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The failure of a tail rotor pitch change link due to the retaining bolt becoming separated in flight. Contributing to the accident was the pilot’s inadequate preflight inspection.

NTSB narrative

The pilot was conducting an aerial observation flight in a helicopter when he felt a high vibration in the tail rotor system in conjunction with a sharp jerk in the anti-torque pedals. The pilot autorotated to a wet field and the helicopter subsequently rolled over. A postaccident examination of the helicopter revealed that a pitch link retaining bolt had come loose from the pitch link attachment horn. The bolt and its associated hardware separated in flight and the bolt hole where the pitch link attached was elongated. According to the helicopter’s preflight inspection checklist, the pitch link should have been checked before flight for binding or looseness; however, the pilot could not recall if he actually checked it. The helicopter underwent a 100-hour maintenance inspection two weeks before the accident. At that time, the maintenance manual required an inspection in which the pitch links would have to be disconnected then reassembled. Since the pitch link retaining bolt and its associated hardware were never recovered, it could not be determined if the pitch link assembly had been properly installed or torqued at the last inspection. The pitch link failure occurred about 14 hours after this inspection. The Federal Aviation Administration reported that they were not aware of any instances prior to this accident where the tail rotor pitch link assemblies became loose and failed prematurely after proper installation.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot should have checked the tail rotor pitch links during pre-flight inspection.

NTSB coding

Evidence available

  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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