Fatigue Cracking Discovered In The Main Wing Spar Of One Airplane
The FAA has issued a Special Airworthiness Information Bulletin (SAIB) for certain Piper Aircraft, Inc. (Piper) Models PA-46-310P, PA-46-350P, PA-46R-350T, and PA-46-500TP airplanes following the discovery of fatigue cracking in the wing main spar lower cap near wing station (WS) 79 on one airplane.
According to the FAA, during routine inspection of a Piper Model PA-46-350P airplane, a 1.53-inch crack was discovered in the main spar lower cap (See Figures 1 through 3 to better identify the damage location). The damage was confirmed to be a standard fatigue crack by metallurgical lab evaluation. The crack discovery was at 5,273 hours time-in-service (TIS) versus the type certificated life limit of 15,580 hours TIS.
No single cause has been identified for the cracking. However, several individual contributing factors researched in this area include not applying existing Service Bulletin (SB) 796B, severe aircraft operating environment, and non-conforming fastener installations. Piper has issued several SBs related to the damage area and contributing factors.
The FAA recommends the following for Piper SBs on Piper Models PA-46-310P, PA-46-350P, PA-46R-350T, and PA-46-500TP airplanes and recommends following the applicability and compliance times included in the SBs.
SB 796B – Lower Wing Rivet Replacement (PA-46-310P, PA-46-350P)
SB 1204 – Re-calculation of Wing Structure Life Limit due to Unique Usage (PA-46-310P, PA-46-350P, PA-46R-350T, PA-46-500TP)
SB 1271 – Wing Spar Inspection (PA-46-310P, PA-46-350P, PA-46-500TP)
The Piper SBs are available at http://www.piper.com.
Damaged components should be repaired or replaced. Piper Aircraft, Inc. has experience with repairs and rework in this area.
It is also recommend damage be reported to the FAA as a Malfunction/Defect Report (MDR) or Service Difficulty Report (SDR) at http://av-info.faa.gov/sdrx/.
(Images provided by the FAA)
