95-23-06: Inspect Forward Firewall

95-23-06 BRITISH AEROSPACE REGIONAL AIRCRAFT LIMITED, AVRO INTERNATIONAL AEROSPACE DIVISION (Formerly British Aerospace, plc; British Aerospace Commercial Aircraft Limited): Amendment 39-9426. Docket 95-NM-206-AD. Applicability: Model BAe 146-100A, -200A, and -300A airplanes, and Model Avro 146-RJ70A, -RJ85A, and RJ-100A airplanes; on which British Aerospace Modification HCM36019A is installed; certificated in any category. NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 use the authority provided in paragraph (d) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafecondition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD. Compliance: Required as indicated, unless accomplished previously. To prevent leakage of hot exhaust gases and subsequent cracking of the forward face of the forward firewall of the auxiliary power unit (APU) bay, which could damage the wiring to the APU fire bottle and result in failure of the APU fire bottle to discharge in the event of an APU fire, accomplish the following: (a) Within 7 days after the effective date of this AD: Perform a close detailed visual inspection to detect cracking and evidence of exhaust leaks in the forward face of the central panel of the forward firewall of the APU bay, in accordance with British Aerospace Service Bulletin S.B.26-35, Revision 1, dated August 30, 1995. NOTE 2: Inspections accomplished prior to the effective date of this AD in accordance with British Aerospace Service Bulletin S.B.26-35, dated May 17, 1995, are considered acceptable for compliance with the applicable action specified in this amendment. (1) If no crack or evidence of gas leakage is found, repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 200 landings, except as provided by paragraph (b) of this AD. (2) If any crack is found, but no evidence of gas leakage is detected, repeat the inspection required by paragraph (a) of this AD thereafter at daily intervals. Within 14 days after detecting any crack, accomplish the replacement specified in paragraph (c) of this AD. (3) If any crack is found and evidence of gas leakage is detected, prior to further flight, accomplish the replacement specified in paragraph (c) of thisAD. Operation of the APU is prohibited (either when the aircraft is on the ground or in flight) until the replacement is accomplished. (b) Installation of a protective aluminum alloy shield on the vertical stiffener (left-hand) next to the exhaust aperture of the forward firewall of the APU bay (Modification HCM36179B), in accordance with British Aerospace Service Bulletin SB.26-36-36179B, dated June 22, 1995, increases the interval for repetitive inspections required by paragraph (a)(1) of this AD from 200 landings to 400 landings. (c) Replacement of the central panel of the forward firewall of the APU bay with a new panel (Modification HCM36179A), in accordance with British Aerospace Service Bulletin SB.26-35-36179A, dated August 4, 1995, 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, Standardization Branch, ANM-113, 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, Standardization Branch, ANM-113. NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113. (e) Special flight permits may be issued in accordance with sections 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 British Aerospace Service Bulletin S.B.26-35, Revision 1, dated August 30, 1995; British Aerospace Service Bulletin SB.26-35-36179A, dated August 4, 1995; and British Aerospace Service Bulletin SB.26-36-36179B, dated June 22, 1995. 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 British Aerospace Holding, Inc., Avro International Aerospace Division, P.O. Box 16039, Dulles International Airport, Washington DC 20041-6039. 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. (g) This amendment becomes effective on November 29, 1995.