AD 92-24-51

92-24-51 BOEING: Amendment 39-8439. Docket No. 92-NM-212-AD. Supersedes AD 92- 21-51 R1, Amendment 39-8414.

Applicability: All Model 747 series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

NOTE: Paragraphs (d) and (f) of this AD require inspections from both ends of the nacelle strut midspar fuse pins, whereas AD 92-21-51 R1, Amendment 39-8414 (57 FR 53546, November 12, 1992), which is superseded by this AD, required inspection from only one end of the fuse pins. As allowed by the phrase, "unless accomplished previously," paragraphs (d) and (f) of this AD do not require that the inspections performed previously from one end of the fuse pins in accordance with AD 92-21-51 R1 be repeated. For those fuse pins, only the end of the fuse pin not inspected previously must be inspected to comply with the initial inspection requirements of this AD.

To prevent failure of the nacelle strut midspar fuse pins, accomplish the following:

(a) Within 30 days after the effective date of this AD, remove all old style nacelle strut midspar fuse pins and replace with new style fuse pins, in accordance with Boeing Service Bulletin 747-54-2063, Revision 9, dated April 23, 1992. When an old style fuse pin is removed, the engine must be removed in accordance with the Boeing Model 747 Maintenance Manual, Section 54-10-03; or supported in accordance with the service bulletin; or supported in a manner approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(b) As of 30 days after the effective date of this AD, no person shall install an old style nacelle strut midspar fuse pin on any airplane.

(c) Perform the inspection required by paragraph (d) of this AD at the times specified in paragraph (c)(1), (c)(2), or (c)(3) of this AD, as applicable.

(1) For airplanes equipped with Pratt and Whitney or Rolls Royce engines on which the new style nacelle strut midspar fuse pins have accumulated 5,000 or more landings as of the effective date of this AD: Inspect inboard engine positions 2 and 3 within 30 days after the effective date of this AD; and inspect outboard engine positions 1 and 4 within 60 days after the effective date of this AD.

(2) For all other airplanes equipped with Pratt and Whitney, Rolls Royce, or General Electric engines having new style nacelle strut midspar fuse pins, other than those identified in paragraph (c)(1) of this AD: Inspect inboard engine positions 2 and 3 at the later of the times specified in paragraph (c)(2)(i) or (c)(2)(ii) of this AD.

(i) Prior to the accumulation of 3,000 landings on the fuse pin or within 3 years since installation of the fuse pin, whichever occurs first; or

(ii) Within 60 days after the effective date of this AD.

(3) For all other airplanes equipped with Pratt and Whitney, Rolls Royce, or General Electric engines having new style nacelle strut midspar fuse pins, other than those identified in paragraph (c)(1) of this AD: Inspect outboard engine positions 1 and 4 at the later of the times specified in paragraph (c)(3)(i) or (c)(3)(ii) of this AD:

(i) Prior to the accumulation of 3,000 landings on the fuse pin or within 3 years since installation of the fuse pin, whichever occurs first; or

(ii) Within 90 days after the effective date of this AD.

(d) In accordance with the compliance times specified in paragraph (c) of this AD, perform a detailed visual inspection to detect corrosion of the new style nacelle strut midspar fuse pins from each end of the fuse pin with the insert removed, in accordance with Boeing Alert Service Bulletin 747-54A2150, Revision 1, dated November 13, 1992. When a new style fuse pin is removed, the engine must be removed in accordance with the Boeing Model 747 Maintenance Manual, Section 54-10-03; or supported in accordance with the service bulletin; or supported in a manner approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(e) If corrosion is detected as a result of the inspection required by paragraph (d) of this AD, prior to further flight, accomplish the following:

(1) If the amount of corroded material that must be removed exceeds the 0.010-inch limit on the fuse pin inner diameter specified in the service bulletin, replace the fuse pin with a new style fuse pin. Thereafter, accomplish the actions required by this AD on the newly-installed fuse pins.

(2) If the amount of corroded material that must be removed is more than light, and equal to or less than the 0.010-inch limit on the fuse pin inner diameter specified in the service bulletin, rework the fuse pin in accordance with the service bulletin instructions, or replace the pin with a new style fuse pin. "Light" corrosion is characterized by discoloration or pitting to a depth of not more than 0.001-inch maximum. Thistype of corrosion can be removed normally by light hand sanding. A fuse pin that has been reworked in accordance with Boeing Alert Service Bulletin 747-54A2150, dated October 5, 1992; or Revision 1, dated November 13, 1992, must be replaced with a new fuse pin prior to the accumulation of 3,000 landings on the fuse pin, or 3 years since the pin was reworked and reinstalled, whichever occurs first.

(3) If the corrosion is light, remove the corroded material in accordance with the service bulletin. Thereafter, repeat the inspections required by paragraph (h) of this AD.

(f) Following accomplishment of the actions required by paragraphs (d) and (e) of this AD, if the fuse pin has been found to be corrosion free, or if the pin has been reworked on the airplane to remove light corrosion, prior to further flight, perform an ultrasonic inspection to detect cracks in the fuse pin from each end of the fuse pin with the insert removed, in accordance with Boeing Alert Service Bulletin 747-54A2150, Revision 1, dated November 13, 1992. When a new style fuse pin is removed, the engine must be removed in accordance with the Boeing Model 747 Maintenance Manual, Section 54-10-03; or supported in accordance with the service bulletin; or supported in a manner approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(g) If any crack is found as a result of the inspections required by paragraph (d) or (f) of this AD, prior to further flight, replace the pin with a new style fuse pin in accordance with Boeing Alert Service Bulletin 747-54A2150, Revision 1, dated November 13, 1992. Thereafter, accomplish the actions required by this AD on the newly-installed fuse pins.

(h) Thereafter, repeat the actions required by paragraphs (d), (e), (f), and (g) of this AD at intervals not to exceed 500 landings.

(i) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(j) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

(k) The inspections, replacement, and rework shall be done in accordance with Boeing Alert Service Bulletin 747-54A2150, Revision 1, dated November 13, 1992; and Boeing Service Bulletin 747-54-2063, Revision 9, dated April 23, 1992; as applicable. 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. Incorporation by reference of Boeing Service Bulletin 747-54-2063, Revision 9, dated April 23, 1992, was approved previously by the Director of the Federal Register as of November 27, 1992 (57 FR 53546, November 12, 1992). Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124- 2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

This AD 92-24-51 supersedes AD 92-21-51 R1, Amendment 39-8414, which superseded AD 86-22-01, Amendment 39-5437, and AD 91-09-01, Amendment 39-6970.

(l) This amendment becomes effective on January 4, 1993, to all persons except those persons to whom it was made immediately effective by telegraphic AD T92-24-51, issued on November 13, 1992, which contained the requirements of this amendment.