Some PA-46 Models May Develop Cracks In Engine Mount Where NLG Attaches

The FAA has issued a Special Airworthiness Information Bulletin pertaining to certain Piper Models PA-46-310P, PA-46-350P, PA-46R-350T, and PA-46-500TP airplanes. The SAIB indicates that the airplane may develop cracks in the engine mount where both the nose landing gear (NLG) trunnion and the NLG actuator attach. This condition is addressed in Piper Service Bulletins (SB) 1103 and 1154 and Piper Service Letter (SL) 1001. This SAIB emphasizes the importance of compliance with Piper service information.

This SAIB does not address PA-46-310P and PA-46-350P aircraft modified by STC ST00541SE, conversion from piston to turboprop propulsion.

This revision to this SAIB provides:

• Updated service information;
• A revised recommendation to incorporate a new engine mount that relieves the repetitive inspections;
• A change to the point of contact information; and
• Other changes that address format and editorial content.

This SAIB is a result of reported cracks being found in the engine mount, both where the actuator for the nose landing gear attaches and at the pivot where the NLG trunnion attaches.

The first type is cracking around the circumference of the “foot” (the metal tube where the actuator bolt attaches). The “foot” cracks occur on some early engine mounts where the “foot” is made up of two parts; a metal disk welded to a metal tube. The cracks have been found in the welded area between the disk and tube. Some aircraft have a one-piece machined foot and have not experienced this problem.

The second type of cracking is in the actuator cluster weld, which attaches the “foot” to the engine mount tubing, and is the subject of service bulletins 1103 and 1154. This second type of cracking occurs in the welded joints where the foot attaches to the engine mount tubes (cluster weld). This type of cracking is independent of whether the foot is welded or machined.

Piper Service Bulletin 1154 and Service Letter 1001 both address cracking in the engine mount where the NLG trunnion attaches.

Forty-nine reports of damaged engine mounts and/or collapsed nose landing gear were identified as of late 2007. These reports came from the National Transportation Safety Board’s accident database and the Federal Aviation Administration’s Service Difficulty and Accident-Incident databases. Of these, 12 appeared to be associated with damage in the area of the NLG actuator attachment and nine in the area of the trunnion pivot. Twenty-four contained insufficient information to determine any relationship to this SAIB, and the remainder did not apply.

After reviewing the relevant data, the FAA recommends inspection of the engine mount where the nose landing gear trunnion and actuator attach. The agency also recommends replacement of the mount with a new mount that relieves the repetitive inspection, where applicable. The inspection and replacement should be performed following the appropriate Piper service information SL 1001, SB 1103, and/or SB 1154 for the model and serial number of your aircraft and the configuration of your engine mount.

(Illustration provided by the FAA)

FMI: SAIB