AD 76-14-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Viking Air Limited | DHC-4 | DeHavilland Model DHC-4 Series Airplanes |
| aircraft | Viking Air Limited | DHC-4A | DeHavilland Model DHC-4 Series Airplanes |
Unsafe Condition
Failure of rivets attaching hinge plates to outboard hinge arms on inboard trailing flap assemblies could lead to flap malfunction. Rudder rib failure could result in loss of rudder control. Electrofilm bearings in flap hinge arms may fail, causing flap system malfunction. External skin cracks on root fore flaps may indicate rib damage leading to structural failure. Loose terminal lug attachment to aluminum electrical cable assemblies could cause fire hazard. Main landing gear failure to fully extend and lock may result in landing gear collapse.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect and alter rivets per Engineering Bulletin DHC-4 No. 11. Inspect and alter rudder ribs per Modification Bulletin 4/1101. Inspect electrofilm bearings and replace with sintered bronze teflon lined bearings per Modification Bulletin 4/1099. Inspect root fore flaps for cracks and damage, remove and alter if required per Modification Bulletin 4/1150. Inspect, test, and replace aluminum electrical cables per Engineering Bulletin DHC-4 No. 18. Install spacer sleeve P/N 5735-5 into main landing gear assembly per Modification Bulletin 4/1182.
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Compliance Time
Within the next 50 hours' time in service after the effective date of this AD for items 1, 4(a), and 6(a). Within 100 hours' time in service for items 2(a) and 6(a). Within 250 hours' time in service for item 3(a). Repeat inspections at intervals not exceeding specified hours' time in service as per AD requirements.
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Affected Aircraft
DeHavilland Model DHC-4 and DHC-4A airplanes with serial numbers 2 through 17 (item 1), 2 through 22, 24, 25 (item 2), 2 through 39 except 23 and 28 (item 3), 1 through 43, 45-59 excluding specific serials (item 4), 4 through 57 excluding listed serials (item 5), and 2 through 38 except 23 and 34 (item 6), certificated in all categories, not altered per specified bulletins.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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