Airworthiness Directive · Amendment 39-22045 · Flight control system
Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes
This AD applies to Viking Air Limited (Type Certificate previously held by Bombardier, Inc. and de Havilland, Inc.) Model DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300, and DHC-6-400 airplanes, all serial numbers, certificated in any category.
The FAA is superseding Airworthiness Directive (AD) 89-24-06 R1, which applied to all Boeing of Canada, Ltd. and de Havilland (now Viking Air Limited) Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. AD 89-24-06 R1 required repetitively inspecting the elevator quadrant for damage and taking corrective action as necessary. Since the FAA issued AD 89-24-06 R1, Transport Canada, the aviation authority for Canada, revised its mandatory continuing airworthiness information (MCAI) to correct this unsafe condition on these products. This AD retains the actions required by AD 89-24-06 R1, extends the compliance time intervals for the repetitive inspections, adds Model DHC-6-400 airplanes to the applicability, and adds a fluorescent penetrant inspection requirement. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Visually inspect the elevator quadrant for indications of distortion (warping, buckling, or score marks) by following paragraphs III.A.2.(a) and III.A.2.(b) of the Accomplishment Instructions in Viking DHC-6 (Twin Otter) Service Bulletin 6-511, Revision A, dated June 22, 1990 (DHC-6 SB 6-511, Revision A) at the following applicable compliance times:
(i) For Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes, before further flight after the effective date of this AD or within 400 hours time-in-service (TIS) after the last inspection required by AD 89-24-06 R1, whichever occurs later, and thereafter at intervals not to exceed 400 hours TIS; or
(ii) For Model DHC-6-400 airplanes, before further flight after the effective date of this AD and thereafter at intervals not to exceed 400 hours TIS.
Note 1 to paragraph (g)(1): The elevator quadrant may be identified as part number (P/N) C6CFM1138-27 (Pre Mod 6/1394), P/N C6CFM1450-27 (Post Mod 6/1394 or production cut-in (PCI) serial number (S/N) 331, Pre Mod 6/1678), or P/N C6CFM1450-29 (Post Mod 6/1678 or PCI S/N 602), and is referred to as assembly P/N C6CF1137-1, -3, -5, or -7.
(2) If any indication of distortion is found on the elevator quadrant during any inspection required by paragraph (g)(1) of this AD, before further flight, replace the elevator quadrant with a serviceable part and inspect the elevator quadrant support bracket assembly for cracks by following paragraphs III.B.1. through III.B.4.(b) of the Accomplishment Instructions in DHC-6 SB 6-511, Revision A. This AD requires that you do a fluorescent penetrant inspection as the type of required dye penetrant inspection. If a crack is found in the elevator quadrant support bracket, before further flight, replace with a serviceable part by following paragraphs III.B.5 through III.B.12 of the Accomplishment Instructions in DHC-6 SB 6-511, Revision A.
(3) For Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes: Within 400 hours TIS after the effective date of this AD, unless already done within the preceding 12 months before the effective date of this AD, inspect the elevator quadrant support bracket assembly for cracks by following paragraphs III.B.1. through III.B.4.(b) of the Accomplishment Instructions in DHC-6 SB 6-511, Revision A. This AD requires that you do a fluorescent penetrant inspection as the type of required dye penetrant inspection. If a crack is found in the elevator quadrant support bracket, before further flight, replace with a serviceable part by following paragraphs III.B.5 through III.B.12 of the Accomplishment Instructions in DHC-6 SB 6-511, Revision A.
