Southwest Airlines

SWA requests that the FAA consider a different compliance time for airplanes that have accomplished Service Bulletin 737-53A1177. Since the likelihood of multi- element damage does not exist for airplanes that have accomplished Service Bulletin 737-53A1177 at stringer 14 left or right, SWA recommends to align the initial grace period and repeat intervals at the same frequency as defined in Service Bulletin 737-53-1216 section 1.E, i.e. 9,000 flight cycles after issuance of AD and repeat inspections thereafter every 9,000 flight cycles. This will align the interior access and inspection requirements with both SB 737-53-1261 and SB 737-53-1216 frame inspection requirements. The 9,000 cycle interval would also allow each aircraft to reach a heavy maintenance opportunity therefore having the aircraft in an appropriate setting for the required inspections and repairs if required. SWA requests clarification with respect to paragraph (h) and (i). Particularly, if an SRM repair is considered a repair option to inspection findings of SB 737-53-1261 as indicated in paragraph (h), then paragraph (i) of the AD should specify that SRM repairs would be an Alternate Method of Compliance and terminating action to the inspections of SB 737-53-1261. SWA confirms that we have had several crack findings on airplanes over 50,000 flight cycles and therefore can not consider the Boeing findings an anomaly. However, based on our experience with the inspections and findings on several airplanes, the Cost of Compliance identified in the NPRM per airplane base ($3,040) is underestimated. Based on our experience with several 737-300 configuration 3 airplanes, the inspection, repair of crack findings, and terminating action on uncracked frames is close to 1,200 labor hours. At an average labor rate of $80 per work hour, the cost per airplane is closer to $96,000. This estimate does not include access to the interior as these airplanes were in a heavy maintenance environment.