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- Feb 15, 2012
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[From the POS site]
The NTSB responded to the Proposed Piper Wing Spar AD and said it would like some clarifications and changes made.
While the affected airplanes all have a similar main spar design in the wing attach-point area where the fatigue cracking was found, engineering data presented by Piper separately to the FAA and the NTSB showed that the localized stress level can vary significantly depending on airplane gross weight, cruising speed, and amount and location of fuel in the wings. The data also showed that the airplanes at greatest risk for fatigue cracking are the PA-28-235 model airplanes, all PA-28R series airplanes, and the PA-32-260 and PA-32-300 model airplanes. The NTSB supports the inspection requirements of the proposed AD for these airplanes.
However, the NTSB notes that the data showed that the risk of fatigue cracking on all affected PA-28 series airplanes other than the PA-28-235 is significantly lower over their assumed useful life. We are concerned that the risks associated with disturbing the joint to complete the inspection may outweigh the risk of fatigue cracking in all affected PA-28 series airplanes other than the PA-28-235 and urge the FAA to reexamine the applicability of the proposed AD.
The NTSB responded to the Proposed Piper Wing Spar AD and said it would like some clarifications and changes made.
While the affected airplanes all have a similar main spar design in the wing attach-point area where the fatigue cracking was found, engineering data presented by Piper separately to the FAA and the NTSB showed that the localized stress level can vary significantly depending on airplane gross weight, cruising speed, and amount and location of fuel in the wings. The data also showed that the airplanes at greatest risk for fatigue cracking are the PA-28-235 model airplanes, all PA-28R series airplanes, and the PA-32-260 and PA-32-300 model airplanes. The NTSB supports the inspection requirements of the proposed AD for these airplanes.
However, the NTSB notes that the data showed that the risk of fatigue cracking on all affected PA-28 series airplanes other than the PA-28-235 is significantly lower over their assumed useful life. We are concerned that the risks associated with disturbing the joint to complete the inspection may outweigh the risk of fatigue cracking in all affected PA-28 series airplanes other than the PA-28-235 and urge the FAA to reexamine the applicability of the proposed AD.
