AD 2009-04-09
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Viking | Air Limited Model DHC-6-1 | Airworthiness Directives; Viking Air Limited Model DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 Airplanes |
| aircraft | Aviat | Various | Airworthiness Directives; Viking Air Limited Model DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 Airplanes |
Unsafe Condition
Inter-rivet cracking on several wing front spar adapter assemblies (P/N C6WM1027-1) on the horizontal and vertical flanges, caused by stress corrosion in the short transverse grain initiated by local riveting induced stresses.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install inspection holes in the left-hand (LH) and right-hand (RH) lower wing skins following Viking DHC-6 Twin Otter Service Bulletin Number V6/541. Initially inspect the LH and RH front spar adapter assemblies for cracks, and repetitively inspect all affected wing box part numbers at intervals not to exceed 1,200 hours time-in-service or 12 months, whichever occurs first.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 180 days after the effective date of this AD for Group 2 airplanes; within 180 days after August 5, 2008, for Group 1 airplanes.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Viking Air Limited Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes, all serial numbers, equipped with specific wing box part numbers (P/Ns) that incorporate a P/N C6WM1027-1 front spar adapter assembly with 10 or more years of service.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 4, 2026
Rights: U.S. Government Public Domain
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