AD 91-06-03

91-06-03 BOEING: Amendment 39-6923. Docket No. 90-NM-152-AD.

Applicability: Model 747 series airplanes, line numbers 001 through 045, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent sudden cabin pressure loss, accomplish the following:

A. Within the next 500 flight cycles after the effective date of this AD, or prior to the accumulation of 12,000 total flight cycles, whichever occurs later, perform a detailed visual inspection for cracks of the Section 42 fuselage frame web at the stringer cutout from body station (BS) 540 to BS 920, Stringer (S) 8L to S-8R. Repeat this inspection thereafter at intervals not to exceed 3,000 flight cycles.

B. If cracking is found as the result of the inspections required by paragraph A. of this AD, prior to further flight, repair the fuselage frame web in accordance with the Boeing 747 Structural Repair Manual (SRM), Section 53-10-04, Figure 4 or Figure 35; or in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.

C. An alternate means 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), Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO.

D. 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.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington.

This amendment (39-6923, AD 91-06-03) becomes effective on April 8, 1991.