AD 2021-24-18 Airworthiness Directives; Viking Aircraft Limited Airplanes

Models named: DHC-3. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Viking Air Limited Model DHC-3 airplanes, all serial numbers, certificated in any category.

Unless already done, do the following actions in paragraphs (f)(1) through (3) of this AD: (1) For all airplanes: Within 3 months after the effective date of this AD, determine and record the number of equivalent air time hours on each wing and tie-bar by doubling the total hours time-in-service (TIS) accumulated on each part. If the total hours TIS of a tie-bar is unknown or cannot be determined, use the total hours TIS of the wing strut lug fitting on the main spar. (2) For airplanes with a maximum certificated gross weight that has never exceeded 8,000 pounds: Remove from service each left-hand and right-hand wing strut fitting and tie-bar by following the Accomplishment Instructions in Viking DHC-3 Otter SB V3/0008, Revision NC, dated February 9, 2017, and the Replacement section of the Accomplishment instructions in De Havilland Aircraft of Canada, Limited DHC-3 Otter Service Bulletin Number 3/37, Revision B, dated October 8, 1982, at whichever of the following compliance times that occurs later: (i) Before the part accumulates 40,000 equivalent air time hours, or (ii) Within 12 months after the effective date of this AD. (3) For airplanes with a maximum certificated gross weight that has ever exceeded 8,000 pounds: Remove from service each left-hand and right-hand wing strut fitting and tie-bar by following the Accomplishment Instructions in Viking DHC-3 Otter SB V3/0008, Revision NC, dated February 9, 2017, and the Replacement section of the Accomplishment instructions in De Havilland Aircraft of Canada, Limited DHC-3 Otter Service Bulletin Number 3/37, Revision B, dated October 8, 1982, at whichever of the following compliance times that occurs later: (i) Before the part accumulates 32,200 equivalent air time hours, or (ii) Within 12 months after the effective date of this AD.

(1) The Manager, New York ACO Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the ACO Branch, send it to the attention of the person identified in paragraph (h)(1) of this AD. (2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

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 fatigue damage of the wing strut lug fitting components or the fuselage to wing strut attachment (tie-bar). The FAA is issuing this AD to identify and correct potential fatigue damage of the wing strut lug fitting components of the fuselage to wing strut attachment. The unsafe condition, if not addressed, could result in cracking and failure of the structural integrity of the wing or the tie-bar.

None.