SCHWEIZER 269C - UNDESIGNAT near Mesa, AZ — 2015-08-23

Probable cause

The disbondment of a main rotor damper, which resulted in the degradation of its damping action and led to excessive main rotor vibrations and oscillations that caused substantial damage to the helicopter in flight and led to a hard landing.

NTSB narrative

The commercial pilot reported that, after returning from a noneventful personal flight and during the approach for landing, he noticed erratic cyclic control movements. He attempted an emergency landing, but the cyclic continued to move erratically counter-clockwise, and the helicopter subsequently landed hard. Postaccident examination of the helicopter revealed that a main rotor damper had disbonded, which would have resulted in the degradation of its damping capability and excessive main rotor vibrations and oscillations. This would have caused substantial damage in the main rotor mast supporting structure and aft cabin bulkhead before the landing and the erratic cyclic control movements reported by the pilot. Further examination of the helicopter and engine did not reveal any additional evidence of a mechanical malfunction or failure that would have precluded normal operation.

Analysis

Primary failure mode

Mechanical failure

First missed decision gate

Pilot could have aborted the landing upon noticing erratic cyclic control movements.

NTSB coding

• Flight control sys malf/fail · Approach

Evidence available

• 5 docket documents

Docket documents5

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Release of Aircraft Wreckage, NTSB Form 6120.15form
• Statement of Party Representatives to NTSB Investigationinterview
• Inspection Logsother
• Airframe and Engine Examination Reportreport

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