Southwest Airlines

SWA is concerned with paragraph (c). Boeing Service Bulletin 737-55-1090 applies to 737-600, -700, -800, -900 airplanes line numbers 379-1556 and 737-700C airplanes line numbers 496-1548. The effectivity does not account for the possibility of horizontal stabilizers moving from one airplane to another. Example #1: SB 737-55-1090 paragraph 1.A.1. indicates that airplane line number 379 is effective to the actions in the Service Bulletin. If the horizontal stabilizers are moved from airplane line number 379 to line number 378 the Service Bulletin is not longer effective to those horizontal stabilizers. Is the intent of the proposed AD to not perform the Service Bulletin actions on horizontal stabilizers that have been moved from effective airplanes? Example #2: SB 737-55-1090 paragraph 1.A.1. indicates that airplane line number 1557 is not effective to the actions in the Service Bulletin. If horizontal stabilizers are moved from airplane line number 1557 to line number 1556 the Service Bulletin would now be effective to those horizontal stabilizers. Is the intent of the proposed AD to perform the Service Bulletin actions on horizontal stabilizers that were originally delivered on airplanes that are not effective to Boeing Service Bulletin 737-55-1090? SWA believes that the intent of the proposed AD is to perform the actions in Boeing Service Bulletin 737-55-1090 on horizontal stabilizers delivered from Boeing on airplanes indicated in Boeing Service Bulletin 737-55-1090 paragraph 1.A.1. In order to accurately apply the actions required by the proposed AD to the correct components, SWA suggests two possible solutions: Possible Solution #1: Replace the proposed paragraph (c) with a list of the applicable horizontal stabilizer serial numbers. Possible Solution #2: Reword the proposed paragraph (c) to state “This AD applies to horizontal stabilizers delivered on The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes.