Applicability: Model 737-100, -200, and -300 series airplanes, line numbers 1 through 1485 inclusive; certificated in any category.

Effective date: April 22, 1999

Compliance: Required as indicated in FAA AD 99-04-23.

99-04-23 BOEING: Amendment 39-11048. Docket 98-NM-148-AD.

Applicability: Model 737-100, -200, and -300 series airplanes, line numbers 1 through 1485 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 (c) 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 broken bolts that attach the terminal support fittings to the upper part of the Body Station (BS) 1088 bulkhead, which could result in reduced structural integrity of the vertical fin installation and possible loss of the vertical fin, accomplish the following:

(a) Within 18 months after the effective date of this AD, perform an ultrasonic inspection to detect broken bolts that attach the terminal support fittings to the upper part of the BS 1088 bulkhead, in accordance with Boeing Service Bulletin 737-53-1107, Revision 3, dated August 26, 1993; as revised by Notice of Status Change 737-53-1107 NSC 3, dated June 9, 1994, and Notice of Status Change 737-53-1107 NSC 4, dated September 22, 1994; or Boeing Service Bulletin 737-53-1107, Revision 4, dated February 8, 1996.

    (1) If no broken bolt is found, repeat the ultrasonic inspection thereafter at intervals not to exceed 18 months.

    (2) If any broken bolt is found, prior to further flight, perform the actions specified in paragraph (b) of this AD.

(b) Prior to the accumulation of 20 years since date of manufacture of the airplane, or within 18 months after the effective date of this AD, whichever occurs later, remove all 16 H-11 steel alloy bolts that attach the terminal support fittings to the upper part of the bulkhead, and perform an eddy current inspection to detect cracking or corrosion of the bolt holes, in accordance with Figure 2 of Boeing Service Bulletin 737-53-1107, Revision 3, dated August 26, 1993; as revised by Notice of Status Change 737-53-1107 NSC 3, dated June 9, 1994, and Notice of Status Change 737-53-1107 NSC 4, dated September 22, 1994; or Boeing Service Bulletin 737-53-1107, Revision 4, dated February 8, 1996.

    (1) If no cracking or corrosion is found, prior to further flight, oversize all 16 bolt holes and install new Inconel bolts, in accordance with Figure 2 of the service bulletin. Accomplishment of this installation constitutes terminating action for the repetitive inspection requirements of this AD.

    (2) If any corrosion is found, prior to further flight, oversize the bolt hole within the limits specified in Figure 2, Step 4, of the service bulletin, and install a new Inconel bolt, in accordance with Figure 2 of the service bulletin. Accomplishment of the installation for all 16 bolt holes constitutes terminating action for the repetitive inspection requirements of this AD. If corrosion does not clean up within the limits specified in Figure 2, Step 4, of the service bulletin, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

    (3) If any cracking is found, prior to further flight, oversize the bolt hole within the limits specified in Figure 2, Step 5, of the service bulletin, and perform another eddy current inspection to ensure cracks have been removed, in accordance with Figure 2 of the service bulletin.

        (i) If, after oversizing, no cracking is found, prior to further flight, oversize the bolt hole again, and install a new Inconel bolt, in accordance with Figure 2 of the service bulletin. Accomplishment of the installation for all 16 bolt holes constitutes terminating action for the repetitive inspection requirements of this AD.

        (ii) If, after oversizing, any cracking is found, prior to further flight, repair in accordance with a method approved by the Manager, Seattle ACO.

NOTE 2: Replacement of all H-11 steel alloy bolts accomplished prior to the effective date of this AD, in accordance with Boeing Service Bulletin 737-53-1107, dated October 15, 1987; Revision 1, dated June 22, 1989; or Revision 2, dated September 10, 1992; is considered acceptable for compliance with the applicable actions specified in paragraph (b) of this AD.

(c) 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.

(d) 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.

(e) Except as provided by paragraphs (b)(2) and (b)(3)(ii) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 737-53-1107, Revision 3, dated August 26, 1993; as revised by Notice of Status Change 737-53-1107 NSC 3, dated June 9, 1994, and Notice of Status Change 737-53-1107 NSC 4, dated September 22, 1994; or Boeing Service Bulletin 737-53-1107, Revision 4, dated February 8, 1996. 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.

(f) This amendment becomes effective on March 29, 1999.

FOR FURTHER INFORMATION CONTACT:
Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.