AD 99-17-02 Airworthiness Directives; Boeing Model 777 Series Airplanes

Models named: 777 series. Read the applicability below — it usually turns on serial or part numbers too.

Model 777 series airplanes listed as Groups 1 and 2 airplanes in Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999; 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 (h) 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 detect and correct wear of the safety spring wear plate doublers on the auxiliary power unit (APU) firewall, which could result in a hole in the APU firewall, and consequent decreased fire protection capability, accomplish the following: Initial Inspection (a) Perform a visual inspection of the two safety spring wear plate doublers on the APU firewall, and measure any wear of the doublers, in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999, at the time specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD, as applicable. (1) For airplanes that have accumulated 6,000 total flight hours or less as of the effective date of this AD: Inspect and measure prior to the accumulation of 6,300 total flight hours. (2) For airplanes that have accumulated more than 6,000 but less than 10,000 total flight hours as of the effective date of this AD: Inspect and measure within 30 days after the effective date of this AD. (3) For airplanes that have accumulated 10,000 total flight hours or more as of the effective date of this AD: Inspect and measure within 10 days after the effective date of this AD. Note 2: Inspections, repairs, and modifications accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 777-53A0018, dated June 29, 1998, are considered acceptable for compliance with this AD, provided that the actions required by paragraph (f) of this AD, as applicable, are accomplished in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999. [[Page 44112]] Repetitive Inspections (b) If, during the inspection required by paragraph (a) of this AD, the wear on each doubler measures less than 0.045 inch, repeat the inspection and measurement required by paragraph (a) of this AD thereafter at intervals not to exceed 60 days, in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999; until paragraph (g) of this AD has been accomplished. (c) If, during the inspection required by paragraph (a) of this AD, the wear on either doubler measures greater than or equal to 0.045 inch, but does not penetrate into or through the APU firewall: Repeat the inspection and measurement required by paragraph (a) of this AD thereafter at intervals not to exceed 30 days, in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999; until paragraph (g) of this AD has been accomplished. Corrective Actions (d) If, during the inspection required by paragraph (a) of this AD, any wear penetrates through either doubler and into or through the APU firewall: Within 20 days after detection of the wear, accomplish either paragraph (d)(1) or (d)(2) of this AD in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999. (1) Install a temporary stainless steel patch on both doublers, and within 4,000 flight cycles after installation of the temporary patch, accomplish the requirements of paragraph (e) of this AD. (2) Accomplish the requirements of paragraph (e) of this AD. (e) For airplanes on which wear is detected that penetrates through either doubler and into or through the APU firewall: Accomplish the requirements of paragraphs (e)(1) and (e)(2) of this AD at the time specified in paragraph (d) of this AD, as applicable. (1) Repair the damage to the APU firewall in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. (2) Replace both existing wear plate doublers of the APU firewall with new stainless steel wear plate doublers in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999. Such replacement constitutes terminating action for the repetitive inspection requirements of paragraphs (b) and (c) of this AD. One-Time Inspection (f) For airplanes having L/N 001 through 037 inclusive that have been modified prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 777-53A0018, dated June 29, 1998: Within 4 years after the effective date of this AD, perform a one- time visual inspection to detect improper clearance between the safety spring wear plate doublers and the APU firewall, in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999. (1) If the doublers are not in contact with the chemically milled pocket of the APU firewall, no further action is required by this paragraph. (2) If the doublers are in contact with the chemically milled pocket of the APU firewall, prior to further flight, install shims between the safety spring wear plate doublers and the APU firewall, in accordance with Part 6 of the Accomplishment Instructions of the service bulletin. Optional Terminating Action (g) Replacement of the existing wear plate doublers of the APU firewall with new stainless steel wear plate doublers, in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999, constitutes terminating action for the repetitive inspection requirements of paragraphs (b) and (c) of this AD. Alternative Methods of Compliance (h) 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 ACO. 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 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. Special Flight Permits (i) 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. Incorporation by Reference (j) Except as provided by paragraph (e)(1) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 1999. 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. (k) This amendment becomes effective on September 17, 1999. Issued in Renton, Washington, on August 4, 1999. D. L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-20501 Filed 8-12-99; 8:45 am] BILLING CODE 4910-13-P