AD 97-23-09 Airworthiness Directives; de Havilland DHC-6 Series Airplanes

Models named: DHC-6- 1, DHC-6-100, DHC-6-200, DHC-6-300. Read the applicability below — it usually turns on serial or part numbers too.

Models DHC-6- 1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes (serial numbers 1 through 411), certificated in any category, that do not have Modification Nos. 6/1461 and 6/1462 incorporated. Note 1: Modification No. 6/1461 introduces fuselage side frames manufactured from material having improved stress corrosion properties at Fuselage Station (FS) 218.125, and Modification No. 6/ 1462 introduces fuselage side frames of this material at FS 219.525. Note 2: 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 (e) 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 already accomplished. To prevent failure of the fuselage because of cracks in the fuselage side frames, which, if not detected and corrected, could result in loss of control of the airplane, accomplish the following: (a) Within the next 200 hours time-in-service (TIS) after the effective date of this AD, unless already accomplished (compliance with AD 78-26-02), and thereafter as indicated below, inspect the fuselage side frames for cracks at FS 218.125 and FS 219.525, as applicable (see chart below) in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland Service Bulletin (SB) No. 6/ 371, which incorporates the following pages: ------------------------------------------------------------------------ Pages Revision level Date ------------------------------------------------------------------------ 1, 2, 5, through 10, 13, 14, 19, Original Issue.... June 2, 1978. 20, and 23. 3, 4, 11, 12, 15, 16, 17, 18, Revision A........ May 18, 1979. 21, and 22. ------------------------------------------------------------------------ Utilize the following chart to determine which fuselage stations are affected: ------------------------------------------------------------------------ Fuselage stations Serial No. Modification 6/ affected (both 1553 incorporated sides) ------------------------------------------------------------------------ 1 through 395................... No................ 218.125 and 219.525. 1 through 395................... Yes............... 219.525 only. 396 through 411................. N/A............... 219.525 only. ------------------------------------------------------------------------ Note 3: Modification 6/1553 incorporates fuselage side frames of improved stress corrosion resistant material at FS 218.125. (1) If any crack is found during any inspection required by this AD, prior to further flight, accomplish one of the following: (i) Repair the cracks in accordance with the ACCOMPLISHMENT INSTRUCTIONS: REPAIR: section of de Havilland SB No. 6/371. Reinspect thereafter at intervals not to exceed 600 hours TIS until the modification specified in paragraph (b) of this AD is incorporated; or (ii) Replace the cracked fuselage side frame in accordance with the ACCOMPLISHMENT INSTRUCTIONS: REPLACEMENT: section of de Havilland SB No. 6/371. Reinspect any fuselage side frame not replaced at intervals not to exceed 600 hours TIS until the modification specified in paragraph (b) of this AD is incorporated. (2) If no cracks are found, reinspect thereafter at intervals not to exceed 600 hours TIS until the modification specified in paragraph (b) of this AD is incorporated, provided no cracks are found during an inspection. If cracks are found, prior to further flight, repair or replace and reinspect as specified in paragraph (a)(1) of this AD. (b) Within the next 4,800 hours TIS after the effective date of this AD, incorporate Modification Nos. 6/1461 and 6/1462 in accordance with the ACCOMPLISHMENT INSTRUCTIONS: REPLACEMENT: section of de Havilland SB No. 6/371. This consists of replacing all fuselage side frames required as specified in the following chart: ------------------------------------------------------------------------ Fuselage stations Serial Nos. Modification 6/ affected (both 1553 incorporated sides) ------------------------------------------------------------------------ 1 through 395................... No................ 218.125 and 219.525. 1 through 395................... Yes............... 219.525 only. 396 through 411................. N/A............... 219.525 only. ------------------------------------------------------------------------ (c) Incorporating Modification Nos. 6/1461 and 6/1462 as specified in paragraph (b) of this AD is considered terminating action for the inspection requirement of this AD. The modifications may be incorporated at any time prior to the next 4,800 hours TIS after the effective date of this AD, at which time they must be incorporated. (d) 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. (e) An alternative method of compliance or adjustment of the initial or repetitive compliance times that provides an equivalent level of safety may be approved by the Manager, New York Aircraft Certification Office (ACO), FAA, 10 Fifth Street, 3rd Floor, Valley Stream, New York 11581. (1) The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, New York Aircraft ACO. (2) Alternative methods of compliance approved in accordance with AD 78-26-02 are not considered approved as alternative methods of compliance with this AD. Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO. (f) The inspections and modifications required by this AD shall be done in accordance with de Havilland Service Bulletin (SB) No. 6/ 371, which incorporates the following pages: ------------------------------------------------------------------------ Pages Revision level Date ------------------------------------------------------------------------ 1, 2, 5, through 10, 13, 14, 19, Original Issue.... June 2, 1978. 20, and 23. 3, 4, 11, 12, 15, 16, 17, 18, Revision A........ May 18, 1979. 21, and 22. ------------------------------------------------------------------------ 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 de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5 Canada. Copies may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., 7th Floor, suite 700, Washington, DC. (g) This amendment (39-10197) supersedes AD 78-26-02, Amendment 39-3370. (h) This amendment (39-10197) becomes effective on December 22, 1997. Issued in Kansas City, Missouri, on October 31, 1997. James E. Jackson, Acting Manager, Small Airplane Directorate, Aircraft Certification Service. [FR Doc. 97-29534 Filed 11-7-97; 8:45 am] BILLING CODE 4910-13-U