Event Description
At the end of the landing rollout, the pilot experienced a loss of control. The airplane veered off the left side of the runway and impacted a snow bank, after which the nose landing gear collapsed.
Examination Findings
An examination of the nose gear revealed that the rear actuator bolt had failed due to overload during the event sequence. The engine mount was found bent near the nose gear actuator attach feet.
Historical Context
Following the identification of a number of cracked engine mounts, several Piper service bulletins were issued and the original engine mount was redesigned. The redesign process included finite element model analysis and other testing programs that were not incorporated in the original mount design.
During a postaccident examination of a similar accident in Steamboat Springs, Colorado, in 2006, investigators found compliance (flexibility) in the original engine mount actuator attach feet structure, which sometimes resulted in cracks in the engine mount at the actuator feet. The NTSB’s investigation of that accident determined that compliance was sometimes exacerbated at some speeds, resulting in a high shimmying effect and a subsequent uncommanded left or right turn of the nosewheel during takeoff or landing.
Subsequent to the Steamboat Springs investigation, evidence was received of bulkhead damage immediately behind the engine mount found on a PA-46-310P in Greeley, Colorado. The Steamboat Springs accident airplane was reexamined in 2008, and similar firewall damage was found. The mechanical damage and marks were consistent with the engine mount contacting the bulkhead periodically before the accident.
Corrective Action
The new engine mount, which the manufacturer subsequently replaced under warranty on all PA 46-500TP airplanes, incorporates a heavy-duty, reinforced one-piece design at the actuator attach point. This design eliminates the two-piece design, which was previously produced in two-weld and subsequent single-weld versions. The reinforced, one-piece design provides a less compliant structure, which prevents relative motion between the two feet in the original engine mount design.