Applicability: All Model 737-100, -200, -200C, -300, -400, and -500 series airplanes; certificated in any category.

Effective date: June 17, 1999

Compliance: Required as indicated in FAA AD 99-08-23.

Remarks: Where applicable, the requirements of this AD must be integrated into the Aircraft's Logbook(s). 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.

99-08-23 BOEING: Amendment 39-11132. Docket 98-NM-337-AD.
Applicability: All Model 737-100, -200, -200C, -300, -400, and -500 series airplanes; 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 (e) 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 and correct fatigue cracking at certain fastener holes of the aft pressure bulkhead, which could result in rapid decompresssion of the fuselage, accomplish the following:

(a) Perform either inspection specified by paragraph (a)(1) or (a)(2) of this AD at the time specified in paragraph (b) of this AD.

(1) Perform a low frequency eddy current inspection from the aft side of the aft pressure bulkhead to detect discrepancies (including cracking, misdrilled fastener holes, and corrosion) of the web of the upper section of the aft pressure bulkhead at body station 1016 at the aft fastener row attachment to the "Y" chord, from stringer 15 left to stringer 15 right, in accordance with Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Section 53-10-54, dated December 5, 1998.

(2) Perform a detailed visual inspection of the aft fastener row attachment to the "Y" chord from the forward side of the aft pressure bulkhead to detect discrepancies (including cracking, misdrilled fastener holes, and corrosion) of the entire web of the aft pressure bulkhead at body station 1016.

(b) Perform the inspection required by paragraph (a) of this AD at the time specified by paragraph (b)(1), (b)(2), or (b)(3) of this AD, as applicable.

(1) For airplanes that have accumulated 40,000 or more total flight cycles as of the effective date of this AD: Inspect within 375 flight cycles or 60 days after the effective date of this AD, whichever occurs later.

(2) For airplanes that have accumulated 25,000 or more total flight cycles and fewer than 40,000 total flight cycles as of the effective date of this AD: Inspect within 750 flight cycles or 90 days after the effective date of this AD, whichever occurs later.

(3) For airplanes that have accumulated fewer than 25,000 total flight cycles as of the effective date of this AD: Inspect prior to the accumulation of 25,750 total flight cycles.

(c) Within 1,200 flight cycles after performing the initial inspection required by paragraph (a) of this AD, and thereafter at intervals not to exceed 1,200 flight cycles: Perform either inspection specified by paragraph (a)(1) or (a)(2) of this AD.

(d) If any discrepancy is detected during any inspection required by this AD: Prior to further flight, accomplish the actions specified by paragraphs (d)(1) and (d)(3), and paragraph (d)(2) if applicable, of this AD.

(1) Perform a high frequency eddy current inspection from the forward side of the bulkhead to detect cracking of the web at the "Y" chord attachment, around the entire periphery of the "Y" chord, in accordance with Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Section 51-00-00, Figure 23, dated November 5, 1997.

(2) If the most recent inspection performed in accordance with paragraph (a) of this AD was not a detailed visual inspection: Accomplish the actions specified by paragraph (a)(2) of this AD. If the inspection was a detailed visual inspection, it is not necessary to repeat that inspection prior to further flight.

(3) Repair any discrepancy such as cracking or corrosion or misdrilled fastener holes 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.

(e) 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.

(f) 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) The eddy current inspections shall be done in accordance with Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Subject 53-10-54, dated December 5, 1998; or Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Section 51-00-00, Figure 23, dated November 5, 1995; as applicable. These references contain the specified list of effective pages:

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.

(h) This amendment becomes effective on May 10, 1999.

FOR FURTHER INFORMATION CONTACT:

Nenita 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.