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.

2000-05-29 BOEING: Amendment 39-11639. Docket 98-NM-58-AD.

Applicability: Model 737-100, -200, -300, -400, and -500 series airplanes; having line numbers 1 through 2737 inclusive; certificated in any category.

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 (d) 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 detect fatigue cracking of the forward pressure bulkhead, which could result in rapid decompression of the airplane fuselage, accomplish the following:

(a) Prior to the accumulation of 20,000 total flight cycles, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, perform inspections of the center web, vertical chords, and side chord areas of the forward pressure bulkhead for fatigue cracking, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1173, Revision 2, dated January 15, 1998, or Revision 3, dated May 6, 1999. Thereafter, repeat the inspections at intervals not to exceed 6,000 flight cycles until the preventive modifications specified by paragraph (c) of this AD have been accomplished.

(b) If any crack is found during any inspection required by paragraph (a) of this AD, prior to further flight, repair the area in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53A1173, Revision 1, dated April 25, 1996, or Boeing Alert Service Bulletin 737-53A1173, Revision 2, dated January 15, 1998, or Revision 3, dated May 6, 1999; 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 basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings; except, where the alert service bulletin specifies that the manufacturer may be contacted for repair instructions, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(d) 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 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(e) 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.

(g) This amendment becomes effective on April 24, 2000.

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

Issued in Renton, Washington, on March 10, 2000.
Donald L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.