AD 93-18-07

93-18-07 BOEING: Amendment 39-8692. Docket 93-NM-129-AD.

Applicability: Model 747 series airplanes equipped with General Electric CF6-80C2 or Pratt & Whitney PW4000 series engines, as listed in Boeing Alert Service Bulletin 747-26A2214, Revision 2, dated August 19, 1993; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To detect wear of the fire extinguishing discharge tubes and support clamps, which could prevent the engine fire extinguishing system from extinguishing an engine fire, accomplish the following:

(a) Within 60 days after the effective date of this AD, conduct a detailed visual inspection to detect damage, chafing, or scoring of the engine number 1 and engine number 4 fire extinguishing discharge tubes and support clamps in the strut-to-wing intersection areas, in accordance with Boeing Alert Service Bulletin 747-26A2214, Revision 2, dated August 19, 1993.

(1) If no damage, chafing, or scoringis detected, prior to further flight, replace the support clamps with clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993. Subsequent to replacement, repeat the detailed visual inspection thereafter at intervals not to exceed 5,000 flight hours. Replacement of the support clamps is required only after the initial inspection.

(2) If damage, chafing, or scoring is detected on any fire extinguishing discharge tube as a result of any inspection required by this AD, prior to further flight, accomplish either paragraph (a)(2)(i), (a)(2)(ii), or (a)(2)(iii) of this AD.

(i) Repair the fire extinguishing discharge tube, in accordance with Boeing Alert Service Bulletin 747-26A2214, Revision 2, dated August 19, 1993; and replace the support clamps with clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993. Subsequent to repair of the tube and replacement of the clamps, repeat the inspection thereafter at intervals not to exceed 1,600 flight hours. Or

(ii) Replace the fire extinguishing discharge tube with a new tube having the same tube dash number, in accordance with Boeing Alert Service Bulletin 747-26A2214, Revision 2, dated August 19, 1993; and replace the support clamps with clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993. Subsequent to replacement, repeat the inspection thereafter at intervals not to exceed 1,600 flight hours. Or

(iii) Replace the fire extinguishing discharge tube with a fire extinguishing discharge tube constructed of steel, and replace the support clamps with clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993. Accomplishment of these replacements constitutes terminating action for the inspection requirements of this AD.

(3) If damage, chafing, or scoring is detected on the support clamps as a result of any inspection required by this AD, prior to further flight, replace the clamps with a serviceable clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993. Subsequent to replacement, repeat the inspection thereafter at intervals not to exceed 1,600 hours flight hours.

(b) Replacement of the fire extinguishing discharge tubes with tubes constructed of steel, and replacement of the support clamps with clamps constructed of teflon, in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993; Revision 1, dated August 12, 1993; or Revision 2, dated August 19, 1993, constitutes terminating action for the inspection requirements of this AD.

(c) 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.

(d) 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.

(e) The inspection, repair, and replacement shall be done in accordance with Boeing Alert Service Bulletin 747-26A2214, dated May 6, 1993;or Boeing Alert Service Bulletin 747-26A2214, Revision 1, dated August 12, 1993; or Boeing Alert Service Bulletin 747-26A2214, Revision 2, dated August 19, 1993; 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. 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.

(f) This amendment becomes effective on November 3, 1993.