AD 90-06-12

90-06-12 BOEING: Amendment 39-6531. Docket No. 89-NM-195-AD.

Applicability: Model 747 series airplanes, line position 676, 679, 685, and 690 through 699, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent cracking of the bulkhead splice strap, accomplish the following:

A. Within the next 1,000 flight cycles after the effective date of this AD, perform an interim modification of the body station 1241 bulkhead in accordance with Boeing Service Bulletin 747-53-2299, Revision 1, dated June 29, 1989.

B. Within the next 5,000 flight cycles after the effective date of this AD, perform an eddy current inspection for cracks of the splice strap in accordance with Boeing Service Bulletin 747-53-2299, Revision 1, dated June 29, 1989.

1. If no cracking is found, prior to further flight, perform permanent modification in accordance with Boeing Service Bulletin 747-53-2299, Revision 1, dated June 29, 1989.2. If cracking is found, prior to further flight, repair in accordance with method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

C. Accomplishment of paragraph B., above, within the next 1,000 flight cycles after the effective date of this AD, is an acceptable alternative to the interim modification required by paragraph A., above.

D. 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, FAA, Northwest Mountain Region.

NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment, and then send it to the Manager, Seattle Aircraft Certification Office.

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.

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 Airplanes, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington.

This amendment (39-6531, AD 90-06-12) becomes effective on April 13, 1990.