Pilot Debrief

BELL HELICOPTER TEXTRON CANADA 429 near Port O'Connor, TX — 2015-08-21

Final reportCEN15LA395
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Date
2015-08-21
Location
Port O'Connor, TX, USA
Aircraft
BELL HELICOPTER TEXTRON CANADA 429
Registration
N429AR
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Hover

Probable cause

The fatigue failure of the tail rotor pitch change link spherical bearing housing as a result of corrosion pitting.

NTSB narrative

The commercial pilot reported that, during cruise flight in the helicopter, he felt a "slight vibration" and heard a "very faint bumping sound." A flight control check revealed no anomalies, and the pilot continued the flight to the destination heliport. While in a 4-ft hover, just before touching down, the helicopter began a slow, uncommanded right turn. The pilot applied full left anti-torque pedal, and the turn stopped. He then lowered the collective and landed without incident. A post-flight inspection of the helicopter revealed that one of the tail rotor outboard pitch change links (PCL) was broken. An examination of the failed PCL revealed fatigue fractures due to pitting corrosion between the spherical bearing and the bearing housing. The fatigue fractures propagated during operation until the PCL bearing housing fractured, separating the PCL from the blade pitch horn end spherical bearing, resulting in a loss of pitch control to the affected blade. The PCL was installed on the helicopter 12 days before the manufacturer issued an alert service bulletin (ASB) introducing a 50-hour recurrent inspection of the tail rotor PCLs for axial and radial bearing play. About 6 months later, the Federal Aviation Administration (FAA) subsequently issued an emergency airworthiness directive (EAD) based on the ASB. The tail rotor PCLs on the accident helicopter were inspected in accordance with the ASB and the EAD 9 days after the EAD was issued. The PCL failed 6.6 flight hours after the inspection. The EAD did not require an inspection of the bearing housing portion of the PCL for corrosion, and it could not be determined if the fatigue cracks were present when the inspection was performed. Following the accident, the manufacturer updated the original ASB to include inspections for bearing cracks, corrosion, and anti-corrosion sealant. The FAA also updated the airworthiness directive to reflect the additional inspections.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Inspection of tail rotor PCLs as per EAD before further flight was not conducted.

NTSB coding

Evidence available

  • 10 docket documents
View NTSB final reportView NTSB docket

Docket documents10

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