AD 75-26-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Viking Air Limited | DHC-6-1 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-100 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-200 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-300 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
Unsafe Condition
Contact welding of the reverse current relay(s), Hartman part number A700AP or A700AAP, may cause electrical fire hazards.
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Required Actions
Inspect reverse current relays for overheat, pitting, corrosion, or surface damage; replace unserviceable relays before further flight. Install a placard prohibiting cross generator engine starting except in emergencies. Conduct bench tests for relays with over 2400 hours time in service. Comply with specific timeframes based on relay usage.
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Compliance Time
Compliance required within specified timeframes: 25 hours time in service for certain relays, 100 hours for bench tests, and 10 flight hours for placard installation. If inspections are not done, flight under FAR 21.197 is allowed to reach a maintenance base.
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Affected Aircraft
De Havilland Model DHC-6 Series Twin Otter aircraft certificated in all categories, including models DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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