Pilot Debrief

PIPER PA 46-350P near Flagstaff, AZ — 2011-06-26

Final reportWPR11LA313
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Date
2011-06-26
Location
Flagstaff, AZ, USA
Airport
FLG
Aircraft
PIPER PA 46-350P
Registration
N9246M
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Landing

Probable cause

Fatigue failure of an engine mount attachment foot, which resulted in collapse of the nose landing gear during landing. Contributing to the accident was the failure of the owner/operator to adhere to the manufacturer's suggested engine mount inspection schedule.

NTSB narrative

After touchdown, the airplane veered to the left when the nose gear was lowered to the runway. The pilot attempted to maintain directional control; however, the airplane continued to veer to the left and departed the runway. Examination of the airplane revealed that the nose landing gear had collapsed, and the engine mount was fractured at one of the two attachment feet for the nose landing gear actuator. Metallurgical examination of the fractured attachment foot revealed that it had failed as a result of fatigue cracking that initiated at the intersection of two welds that joined two of the engine mount’s support tubes to the right attachment foot. The fatigue cracking progressed along the toe of the weld that joined the forward support tube to the attachment foot. The location of the fatigue fracture was consistent with bending loads caused by a force directed aft by the nose gear actuator. About 9 years prior to the accident, the airframe manufacturer issued a service bulletin requiring an inspection of the engine mount attachment feet at the first regularly scheduled maintenance event after the engine mount reached 290 hours time-in-service and thereafter every 100 hours. If cracks were observed, a new engine mount must be installed. The service bulletin also states that, despite the replacement of the engine mount, the inspections should continue. As part of the inspection procedure, the paint is removed from and around the attachment feet. After the inspection is complete, the area is covered with a corrosion prevention compound. The airframe manufacturer considers performance of the service bulletin mandatory. On April 8, 2010, the National Transportation Safety Board (NTSB) issued Safety Recommendation A-10-44, which asked the Federal Aviation Administration (FAA) to require repetitive inspections of the engine mount feet. On December 22, 2011, based on the FAA’s response that the safety risk is not sufficient to warrant issuance of an airworthiness directive to require the repetitive inspections, the NTSB classified the recommendation Closed-Unacceptable Action. Review of the airframe maintenance records indicated the airplane’s total time at its most recent inspection was about 2,238 hours, and no entries were found indicating replacement of the engine mount or compliance with the manufacturer’s issued service bulletin. Additionally, paint was observed on and around the attachment feet, which indicates that the inspection had never been performed.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Failure to comply with mandatory inspections for engine mount cracks.

NTSB coding

Evidence available

  • Photos
  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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