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FAA concerned about PA-31 wire chafing riskFAA concerned about PA-31 wire chafing risk

The FAA has issued a special airworthiness information bulletin (SAIB) to alert operators of certain Piper Aircraft PA-31T, PA-31T1, PA-31T2, PA-31T3, and PA-31P-350 twin-engine airplanes of a wiring condition at the floor-mounted circuit breaker panel that could lead to chafing, thermal stress, or arcing in the area directly below the panel.

The SAIB requests information and photos of aircraft in which the conditions exist, as detailed below. 

The SAIB says that “during inspections of multiple Piper Model PA-31T airplanes, several airplanes showed unacceptable wire separation from hydraulic lines and /or adjacent structure below the floor-mounted main power distribution CB (circuit breaker) Panel. The inspections also showed early signs of chafing, which can lead to thermal stress and arcing in an area where flammable liquids are routed. These conditions could sustain an uncontrollable fire in an inaccessible area below the pressurized deck.”

The SAIB lists several inspection and repair steps recommended to be taken at the next scheduled maintenance visit, and thereafter at annual inspections, as well as a functional test on any electrical systems that were disturbed during any inspection. Use Advisory Circular 43.13-1B, Acceptable Methods, Techniques and Practices–Aircraft Inspection and Repair, as guidance.

Image courtesy of FAA.

The FAA said reviews are ongoing, and the airworthiness concern has not been determined to be an unsafe condition that would warrant an airworthiness directive. However, the National Transportation Safety Board is investigating an accident involving a PA-31T in which “the pilot reported smoke in the cockpit and subsequently sustained an in-flight breakup and collision with tree-covered terrain near Arcata/Eureka Airport, McKinleyville, California. Evidence of thermal damage was present in the forward section of the fuselage,” it said.

The FAA requests that if you find any conditions where wires are in direct contact with hydraulic fluid lines, aircraft structure and/or any wiring condition that could lead to arcing, shorting, or other damage to the floor-mounted circuit breaker panel, please send details (registration number of the aircraft, total hours, inspection results, etc.) and photographs to Bryan Long, Aerospace Engineer, Atlanta ACO, 1701 Columbia Ave., College Park, GA 30337; or call 404/474-5578. Email is the preferred method of submission.

Topics: FAA Information and Services, Ownership, Maintenance

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