Remarks: The compliance of this AD must be recorded in Aircraft Logbook, where applicable the requirements of this AD must be integrated into Aircraft Technical Documentation. Address inquiries concerning this AD to: Civil Aviation Authority, Airworthiness Division, Ruzyne Airport, 160 08 Prague 6, Czech Republic, tel: 420 2 33320922, fax: 420 2 20562270.

2000-08-08 BOEING: Amendment 39-11694. Docket 2000-NM-88-AD.

Applicability: 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.

Compliance: Required as indicated, unless accomplished previously.

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.

(b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(c) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(d) Except as required by paragraph (a)(2) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 737-57-1253, dated December 16, 1999. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207.

Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on May 9, 2000.

FOR FURTHER INFORMATION CONTACT:
Nenita Odesa, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2557; fax (425) 227-1181.

Issued in Renton, Washington, on April 14, 2000.
Charles D. Huber, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.