Airworthiness Directive · Amendment 39-22062 · Engine controls
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, serial numbers 001 through 989, 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-6-1, DHC-6-100, DHC- 6-200, DHC-6-300, and 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 identifies the unsafe condition as binding of the rod end bearing connecting the lower fuel control unit (FCU) push rod assembly to the FCU power lever. This AD requires performing tests, inspections, and lubrication of the FCU push rod assemblies, and replacing them with improved parts as necessary. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 125 hours time-in-service (TIS) after the effective date of this AD or within 30 days after the effective date of this AD, whichever occurs first, test each affected FCU push rod assembly for binding and restriction in accordance with the Accomplishment Instructions, paragraphs A.1. through A.3., in Viking DHC-6 Twin Otter Service Bulletin No. V6/0063, Revision A, dated February 1, 2021 (Viking SB V6/0063, Revision A).
(i) If there is any binding or restriction, before further flight, remove both affected FCU push rod assemblies from service and install serviceable FCU push rod assemblies in accordance with the Accomplishment Instructions, paragraph A.4., in Viking SB V6/0063, Revision A, and the Accomplishment Instructions, Sections A through C, in Viking DHC-6 Twin Otter Technical Bulletin No. V6/00155, Revision NC, dated September 14, 2020 (Viking TB V6/00155, Revision NC).
(ii) If there is no binding and no restriction, before further flight, remove each affected FCU push rod assembly, clean the push rod ends, and inspect each affected FCU push rod assembly for corrosion and condition of the lubricant. Pay particular attention to the bearing ball and race.
(A) If there is no corrosion and the lubricant color and texture is normal, before further flight, lubricate each affected FCU push rod assembly in accordance with the Accomplishment Instructions, Section C, in Viking SB V6/0063, Revision A.
(B) If there is corrosion or if the lubricant is abnormal in color (too dark) or texture (too sticky), before further flight, remove both affected FCU push rod assemblies from service and install serviceable FCU push rod assemblies in accordance with the Accomplishment Instructions, paragraph A.4, in Viking SB V6/0063, Revision A, and the Accomplishment Instructions, Sections A through C, in Viking TB V6/00155, Revision NC.
(2) Repeat the requirements of this AD as follows until both affected FCU push rod assemblies are replaced.
(i) Test and lubrication: At intervals not to exceed 125 hours TIS or before further flight anytime the airplane has not been operated for a period of 30 days, whichever occurs first.
(ii) Inspection: At intervals not to exceed 1,500 hours TIS.
(3) As of the effective date of this AD, do not install an affected FCU push rod assembly on any airplane.
