AD 90-06-06

90-06-06 BOEING: Amendment 39-6490. Docket No. 89-NM-68-AD. Applicability: Model 747 series airplanes, listed in Boeing Document No. D6-35999, dated March 31, 1989, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent structural failure, accomplish the following:

A. Prior to reaching the incorporation thresholds listed in Boeing Document No. D6-35999, dated March 31, 1989 (hereinafter called "the Document"), or within the next 4 years after the effective date of this AD, whichever occurs later, except as noted in paragraph B., below, accomplish the structural modifications listed in Section 3 of the Document.

B. 1. Accomplish replacement of the trailing edge flap tracks in accordance with Boeing Alert Service Bulletin 747-57A2229, Revision 8, dated January 31, 1989, within the next 5 years after the effective date of this AD.

NOTE: For the purpose of complying with this AD, replacement of trailing edge flap tracks in accordance with Boeing Alert Service Bulletin 747-53A2229, Revision 8, dated January 31, 1989, is considered equivalent to replacement in accordance with either Boeing Alert Service Bulletin 747-57A2229, Revision 7, dated October 13, 1988, or Revision 9, dated November 2, 1989, or Boeing Service Bulletin 747-57-2146, Revision 3, dated May 9, 1986.

2. Incorporation thresholds expressed as "at next overhaul," shall be accomplished within the next 6 years after the effective date of this AD, or prior to the accumulation of 20,000 flights, whichever occurs later.

3. Accomplish the APU cutout reinforcement in accordance with Boeing Service Bulletin 747-53-2275, Revision 3, dated January 25, 1990, prior to the accumulation of 20,000 flights, or within the next 5,000 flights after the effective date of this AD, whichever occurs later.

4. If the 1241 bulkhead splice strap is cracked, replace the strap in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, within the next 4 years after the effective date of the AD, or prior to the accumulation of 20,000 flight cycles, or within 2 years of crack discovery, whichever occurs latest.

NOTE: For the purpose of complying with this AD, the incorporation of the terminating modification for the longitudinal floor beams contained in Boeing Service Bulletin 747-53-2224, Revision 6, dated July 27, 1989, is considered equivalent to the incorporation of the terminating actions contained in Service Bulletins 747-53-2176, Revision 3, dated December 15, 1978, and 747-53-2183, Revision 1, dated March 14, 1980.

NOTE: The modifications required by paragraphs A. and B., above, do not terminate the inspection requirements of any other AD unless that AD specifies that any such modification constitutes terminating action of the inspection requirements.

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, 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.

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.

The modifications shall be done in accordance with Boeing Document No. D6-35999, dated March 1989, "Aging Airplane Service Bulletin Structural Modification Program - Model 747." 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 Airplanes, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington; or at the Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington; or at the Office of the Federal Register, 1100 L Street, N.W., Room 8301, Washington, D.C.

This amendment (39-6490, AD 90-06-06) becomes effective on April 17, 1990.