AD 99-04-11 Airworthiness Directives; Boeing Model 737-600, -700, and -800 Series Airplanes

Models named: 737-600, -700, -800 series. Read the applicability below — it usually turns on serial or part numbers too.

Model 737-600, -700, and -800 series airplanes, line numbers 1 through 64 inclusive, certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Required as indicated, unless accomplished previously. To prevent damage of the aft strut insulation blankets, which could result in exposure of the lower surface of the strut to extreme high temperatures, consequent creation of a source of fuel ignition, and increased risk of a fuel tank explosion and fire, accomplish the following: (a) Within 500 flight hours since date of manufacture of the airplane, or within 30 days after the effective date of this AD, whichever occurs later, perform a visual or borescope inspection to detect damage (cracks greater than 2.00 inches and/or separation of the face sheet) of the aft strut insulation blanket, part number (P/ N) S315A213-42, in accordance with Boeing Alert Service Bulletin 737-54A1038, dated May 7, 1998, as revised by Notice of Status Change 737-54A1038 NSC 01, dated June 18, 1998. Thereafter, repeat the visual or borescope inspection at intervals not to exceed 250 flight hours. (b) If damage (cracks greater than 2.00 inches and/or separation of the face sheet) of any aft strut insulation blanket is detected during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish either paragraph (b)(1) or (b)(2) of this AD. (1) Replace any damaged insulation blanket having P/N S315A213- 42 with a new insulation blanket having P/N S315A213-42, in accordance with Boeing Alert Service Bulletin 737-54A1038, dated May 7, 1998, as revised by Notice of Status Change 737-54A1038 NSC 01, dated June 18, 1998. Thereafter, repeat the visual or borescope inspection required by paragraph (a) of this AD at intervals not to exceed 250 flight hours. Or (2) Replace any damaged insulation blanket having P/N S315A213- 42 with a new, improved insulation blanket having P/N S315A213-47, in accordance with Boeing Alert Service Bulletin 737-54A1038, dated May 7, 1998, as revised by Notice of Status Change 737-54A1038 NSC 01, dated June 18, 1998. Accomplishment of this replacement constitutes terminating action for the repetitive inspection requirements of this AD. (c) Within 18 months after the effective date of this AD, replace any aft strut insulation blanket having P/N S315A213-42 with a new, improved insulation blanket having P/N S315A213-47, in accordance with Boeing Alert Service Bulletin 737-54A1038, dated May 7, 1998, as revised by Notice of Status Change 737-54A1038 NSC 01, dated June 18, 1998. Accomplishment of this replacement constitutes terminating action for the requirements of this AD. (d) 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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (e) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. (f) The actions shall be done in accordance with Boeing Alert Service Bulletin 737-54A1038, dated May 7, 1998, as revised by Notice of Status Change 737-54A1038 NSC 01, dated June 18, 1998. 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 [[Page 6793]] Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (g) This amendment becomes effective on March 18, 1999. Issued in Renton, Washington, on February 4, 1999. John J. Hickey, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-3188 Filed 2-10-99; 8:45 am] BILLING CODE 4910-13-P