Airworthiness Directive · Amendment 39-21921 · Time limits
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) 80-13-10, AD 80-13-12 R1, and AD 2008-03-01, which applied to certain de Havilland (type certificate now held by Viking Air Limited) Model DHC- 6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. AD 80-13-10 required repetitively inspecting the main landing gear (MLG) legs for cracks and corrosion. AD 80-13-12 R1 required repetitively inspecting each engine nacelle lower longeron for cracks and buckling. AD 2008-03- 01 required incorporating inspections, modifications, and life limits of certain structural components into the aircraft maintenance program. Since the FAA issued those ADs, new and more restrictive airworthiness limitations have been issued for certain structural components. This AD requires incorporating into maintenance records new or revised life limits, modification limits, and inspection or overhaul intervals. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 30 days after the effective date of this AD, incorporate into the maintenance records required by 14 CFR 91.417(a)(2) or 135.439(a)(2) for your airplane the life limits, modification limits, and inspection or overhaul intervals in Viking Air Limited DHC-6 Twin Otter PSM 1-6-11, Airframe Airworthiness Limitations Manual, Revision 9, dated April 30, 2018 (Viking Air Limited PSM 1-6-11, Revision 9).
(2) Before further flight after revising the maintenance records as required by paragraph (g)(1) of this AD, except as allowed under paragraph (h) of this AD, remove from service each part that has reached or exceeded its life limit and modify each part that has reached or exceeded its modification limit.
(3) Before further flight after revising the maintenance records as required by paragraph (g)(1) of this AD, except as allowed under paragraph (h) of this AD, inspect or overhaul each part that has reached or exceeded its inspection or overhaul interval.
The following phase-in periods are allowed to comply with the initial tasks in Viking Air Limited PSM 1-6-11, Revision 9.
(1) Task 27-007: For any pulley that has been in service for 48 or more months on the effective date of this AD, replace the pulley within 12 months after the effective date of this AD.
(2) Tasks 32-001 and 32-002:
(i) For any main landing gear (MLG) leg that, on the effective date of this AD, has not been marked with a new serial number as specified in Viking DHC-6 Twin Otter Technical Bulletin V6/00063: Within 6 months after the effective date of this AD, inspect and serialize the MLG leg. The absence of a serial number indicates that the initial inspection of the landing gear leg has not previously been accomplished.
(ii) For all other MLG legs, overhaul the MLG leg within 60 months after the last overhaul.
(3) Tasks 57-006, 57-007, 57-010, 57-011, 57-013, and 57-014:
(i) For any wing that on the effective date of this AD has accumulated more than 16,000 hours total TIS or 32,000 total flight cycles but less than 17,000 hours total TIS or less than 34,000 total flight cycles, accomplish the task within 1,000 hours TIS or 2,000 flight cycles, whichever occurs first after the effective date of this AD.
(ii) For any wing that on the effective date of this AD has accumulated 17,000 or more hours total TIS or 34,000 or more total flight cycles, accomplish the task before accumulating 18,000 hours total TIS or 36,000 total flight cycles, or within 60 months after the effective date of this AD, whichever occurs first.
(4) Tasks 57-018, 57-019, 57-022, 57-023, 57-026, 57-027, 57-030, and 57-031:
(i) For any wing that on the effective date of this AD has accumulated more than 11,000 hours total TIS or 22,000 total flight cycles but less than 12,000 hours total TIS or less than 24,000 total flight cycles, accomplish the task within 1,000 hours TIS or 2,000 flight cycles, whichever occurs first after the effective date of this AD.
(ii) For any wing that on the effective date of this AD has accumulated 12,000 or more hours total TIS or 24,000 or more total flight cycles, accomplish the task before accumulating 13,000 hours total TIS or 26,000 total flight cycles or within 60 months after the effective date of this AD, whichever occurs first.
(5) Tasks 57-039 to 57-041 inclusive: For any wing that on the effective date of this AD has more than 20 years since the date of manufacture and has not previously been inspected in accordance with Viking Service Bulletin V6/0018, inspect the wing upper surface within 120 days after the effective date of this AD.
After the maintenance records have been revised as required by paragraph (g) of this AD, no alternative actions (e.g., inspections) or intervals may be used unless the actions or intervals are approved as an alternative method of compliance (AMOC) in accordance with the procedures specified in paragraph (j)(1) of this AD.
