Airworthiness Directive · Amendment 39-11694 · Boeing Model 737-600, -700, and -800 Series Airplanes
Boeing Model 737-600, -700, and -800 Series Airplanes
Model 737-600, -700, and -800 series airplanes; certificated in any category; line numbers 1 through 321 inclusive.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-600, -700, and -800 series airplanes. This action requires a one-time inspection to detect cracking of the rear spar stiffeners in the wing center section; and modification of crack-free stiffeners, or repair of cracked stiffeners. This amendment is prompted by a report of severed rear spar stiffeners of the center wing, which resulted in cracking in the adjacent keel beam structure. The actions specified in this AD are intended to prevent failure of the keel beam structure.
To prevent failure of the keel beam structure, accomplish the following:
(a) Prior to the accumulation of the total number of flight cycles specified by Table 1, “Compliance Thresholds,” as applicable, of Boeing Service Bulletin 737-57-1253, dated December 16, 1999; or within 60 days after the effective date of this AD, whichever occurs later: Perform a one-time high-frequency eddy current inspection to detect cracking of the rear spar stiffeners that are located at the left and right buttock lines 6.15 of the wing center section, in accordance with the service bulletin.
(1) If no cracking is detected in either stiffener: Prior to further flight, install the preventive modification on that stiffener, in accordance with the service bulletin.
(2) If any cracking is found in either stiffener, prior to further flight, repair that stiffener in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.
