AD 92-02-01

92-02-01 BOEING: Amendment 39-8137. Docket No. 91-NM-103-AD.

Applicability: Model 747 series airplanes, line number 001 through 113, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent sudden decompression of the airplane, accomplish the following:

(a) Within the next 500 flight cycles after the effective date of this AD, unless previously accomplished within the last 1,500 flight cycles, perform an initial high frequency eddy current inspection of the doorstop support fittings at the forward edge of the number 5 main entry doors, in accordance with Boeing Alert Service Bulletin 747-53A2326, dated December 20, 1990, to determine material type, if not known, and accomplish the following prior to further flight:

(1) For doorstop support fittings which have been determined to be made of 7075-T73 aluminum: No further action is required under the inspection requirements of this AD.

(2) For doorstop support fittings which have been determined to be made of 7079-T6 aluminum: Visually inspect the fittings for cracking in accordance with Boeing Alert Service Bulletin 747-53A2326, dated December 20, 1990. Repeat this inspection thereafter at intervals not to exceed 2,000 flight cycles.

(b) If cracking is found as the result of the inspections required by paragraph (a) of this AD, prior to further flight, replace the cracked doorstop support fittings with doorstop support fittings made of 7075-T73 aluminum, in accordance with Boeing Alert Service Bulletin 747-53A2326, dated December 20, 1990. Continue to reinspect any remaining doorstop support fittings made of 7079-T6 material in accordance with paragraph (a)(2) of this AD.

(c) Replacement of all doorstop fittings made of 7079-T6 material in accordance with Boeing Alert Service Bulletin 747-53A2326, dated December 20, 1990, constitutes terminating action for the repetitive inspection requirements of this AD.

(d) An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO.

(e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

(f) The inspection and replacement shall be done in accordance with Boeing Alert Service Bulletin 747-53A2326, dated December 20, 1990. 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. Copies may be inspected at the FAA,Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington, or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, D.C.

(g) This amendment (39-8137, AD 92-02-01) becomes effective on March 23, 1992.