AD 92-08-02

92-08-02 BOEING: Amendment 39-8213. Docket No. 90-NM-181-AD. Supersedes AD 88-16-01, Amendment 39-5983.

Applicability: Model 747 airplanes listed in Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the body station (BS) 1241 bulkhead forging, which could lead to loss of cabin pressure or the inability of the airplane to withstand fail-safe loads, accomplish the following:

(a) For airplanes Group 1 through Group 8 (as defined in Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989) on which a replacement bulkhead splice strap has not been incorporated in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, accomplish the following:

(1) Perform an eddy current inspection of the BS 1241 bulkhead splice strap at the aft hole and visually inspect the aft edge of the strap in accordance with the service bulletin at the later of the times indicated in subparagraph (a)(1)(i) or (a)(1)(ii), unless previously accomplished within the last 6,000 landings:

(i) Within the next 1,000 landings after the effective date of this AD, or

(ii) Prior to the accumulation of 10,000 total airplane landings.

(2) If no crack is found, repeat the inspections required by paragraph (a)(1) of this AD thereafter at intervals not to exceed 7,000 landings.

(3) If a crack is found on the aft edge of the bulkhead splice strap or at the aft hole, prior to further flight, perform an eddy current inspection for cracks in the bulkhead splice strap and forging at the adjacent forward hole, in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989.

(i) If no crack is found or if a crack is found only in the bulkhead splice strap, repeat the inspection required by paragraph (a)(3) of this AD at the forward hole thereafter at intervals not to exceed 3,000 landings.

(ii) If a crack is found in the bulkhead forging, repair as follows:

(A) If the crack found in the forward hole of the forging does not exceed the forward hole rework limits specified in Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, and the forward hole coldwork has not been previously accomplished, repair prior to further flight, in accordance with the service bulletin, and continue to reinspect in accordance with paragraph (a)(3) of this AD at intervals not to exceed 3,000 landings.

(B) If the crack found in the forging exceeds the forward hole rework limits, or if the hole coldwork has been previously accomplished, prior to further flight, repair in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.

(b) For airplanes Group 9 through Group 18 (as defined in Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989) on whicha replacement bulkhead splice strap has not been incorporated in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, accomplish the following:

(1) Perform an eddy current inspection of the BS 1241 bulkhead splice strap at the aft hole and visually inspect the aft edge of the strap at the later of the times indicated in subparagraph (b)(1)(i) or (b)(1)(ii), unless previously accomplished within the last 6,000 landings:

(i) Within the next 1,000 landings after the effective date of this AD, or

(ii) Prior to the accumulation of 10,000 total landings.

(2) If no crack is found, repeat the inspections required by paragraph (b)(1) of this AD at intervals not to exceed 7,000 landings.

(3) If a crack is found on the aft edge of the bulkhead splice strap or at the aft hole, prior to further flight, perform an eddy current inspection for cracks in the bulkhead splice strap and forging at the adjacent forward hole in accordance withBoeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989.

(i) If no crack is found or if a crack is found only in the bulkhead splice strap when inspecting the forward hole, repeat the inspections required by paragraph (b)(3) of this AD at the forward hole thereafter at intervals not to exceed 3,000 landings.

(ii) If a crack is found in the bulkhead forging, prior to further flight, repair in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.

(c) For airplanes Group 1 through Group 18 on which a replacement bulkhead splice strap has been incorporated in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, accomplish the procedures specified in subparagraph (c)(1) and (c)(2) of this AD.

NOTE: Boeing Service Bulletin 747-53-2283, Revision 3, references Boeing Service Bulletin 747-53-2219 for an alternative method of accomplishing the replacement of bulkhead splice straps; either method is acceptable for the purposes of this AD. Therefore, airplanes on which splice strap replacement previously has been accomplished in accordance with Boeing Service Bulletin 747-53-2219, Revision 2, or later FAA-approved revisions, are eligible to defer the initial eddy current inspection required by this paragraph to the 10,000-landings threshold, as specified in paragraph (c)(1).

(1) Perform an eddy current inspection to detect cracks in accordance with the service bulletin at the later of the times indicated in subparagraph (c)(1)(i) or (c)(1)(ii), unless previously accomplished within the last 9,000 landings:

(i) Within 1,000 landings after the effective date of this AD, or

(ii) Prior to the accumulation of 10,000 landings after the replacement of the bulkhead splice strap.

(2) Repair all cracks prior to further flight, in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.(d) For airplanes Group 1 through Group 18, accomplish the following: Compliance with this paragraph terminates the requirement for the inspections contained in paragraphs (a) and (b) of this AD.

(1) Perform an eddy current inspection or ultrasonic inspections (as applicable and as specified in the service bulletin) of the forward and aft holes to detect cracking in the splice strap and bulkhead forging, in accordance with the "Aging Fleet Flight-Safety Inspection Program" specified in Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, at the latest of the times indicated in subparagraph (d)(1)(i), (d)(1)(ii), or (d)(1)(iii), unless previously accomplished within the last 2,000 landings:

(i) Prior to the accumulation of 20,000 landings on any unmodified, or modified bulkhead splice strap; or

(ii) Prior to the accumulation of 20,000 landings after replacement of the bulkhead splice strap; or

(iii) Within the next 1,000 landings after theeffective date of this AD.

(2) If no crack is found in the bulkhead splice strap or bulkhead forging, repeat the inspection required by paragraph (d)(1) of this AD thereafter at intervals not to exceed 3,000 landings.

(3) If a crack is found in a bulkhead splice strap not yet modified in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989, replace the bulkhead splice strap in accordance with the service bulletin within the next 4 years after April 17, 1990 (the effective date of AD 90-06-06); or prior to the accumulation of 20,000 total airplane landings; or within 2 years after crack discovery; whichever occurs latest. If a crack is found in the bulkhead forging, prior to further flight, repair in accordance with the service bulletin. Repeat the inspections required by paragraph (d)(1) of this AD thereafter at intervals not to exceed 3,000 landings.

(4) If a crack is found in a modified or replacement bulkhead splice strap or bulkhead forging, prior to further flight, replace the bulkhead splice strap in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989.

(i) Prior to the accumulation of 10,000 landings thereafter, perform an eddy current inspection to detect cracks, in accordance with the service bulletin. Repair all cracks, prior to further flight, in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.

(ii) Prior to the accumulation of 20,000 landings after such replacement, reinspect in accordance with the provisions of this paragraph.

(e) 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.

(f) 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.

(g) The inspections and modification shall be done in accordance with Boeing Service Bulletin 747-53-2283, Revision 3, dated November 1, 1989. 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, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington 98055-4056; or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, DC.

(h) This amendment becomes effective on May 19, 1992.