Airworthiness Directive · Amendment 39-22002 · Aircraft fuel 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-6-400 airplanes, serial numbers 845 through 957, certificated in any category.
The FAA is adopting a new airworthiness directive (AD) for certain Viking Air Limited (type certificate previously held by Bombardier Inc. and de Havilland, Inc.) Model DHC-6-400 airplanes. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as corrosion of the fuel system components located in the fuel gallery due to inadequate corrosion protection. This AD requires repetitively inspecting the fuel gallery for corrosion, rectifying any deficiencies, and accomplishing modifications to the fuel gallery system. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 50 hours time-in-service (TIS) after the effective date of this AD or within 3 months after the effective date of this AD, whichever occurs first, and thereafter at intervals not to exceed 125 hours TIS, do the following actions:
(i) Remove all fuel gallery covers and rinse the fuel gallery with water.
(ii) Inspect the fuel gallery for corrosion and, if there is any corrosion, take all necessary corrective actions before further flight by following Item D.15(2) of Special Inspection 3 in Temporary Revision No. 241, dated July 27, 2021, to the Viking DHC-6 Inspection Requirements Manual, PSM 1-6-7.
(2) Within 12 months after the effective date of this AD, install the modifications applicable to your airplane serial number by following the Accomplishment Instructions, sections A. through E., in Viking DHC-6 Twin Otter Service Bulletin No. V6/0044, Revision B, dated September 13, 2021 (Viking SB V6/0044, Revision B).
Within 12 months after the airplane is modified to operate on floats, regardless of whether the landing gear is later modified back to non-float landing gear, install the modifications applicable to your airplane serial number by following the Accomplishment Instructions, sections A. through E., in Viking SB V6/0044, Revision B.
