AD 76-08-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Viking Air Limited | DHC-3 | Airworthiness Directives; de Havilland Aircraft of Canada, Ltd Model DHC-3 (U-1A) Airplanes |
Unsafe Condition
Failure of the left hand upper exhaust pipe at a point immediately below the existing clamp bracket could result in engine compartment fire hazard due to overheating of the pump. Overheating of the fuel booster pump motor could lead to a fire hazard. Inadequate locking of the rear cargo door may allow door opening during flight. Excessive rivet spacing on the fuselage former cap strips may cause structural weakening. Inadequate current return path from the fuel booster pump motor may cause overheating and fire hazard. Inadequate attachment of rear cabin seats to the luggage compartment post may result in seat detachment. Displacement of the wing flap actuating jack head assembly sintered metal filter could cause marginal engagement between the filter internal retainer and seal holder. Aluminum rivets in the engine firewall may not provide fireproof integrity, increasing fire risk. Inadequate lubrication of the main landing ski axle pin may lead to premature wear and failure. Possible loss of tail wheel assembly in flight due to insufficient retention. Inadequate margin of safety in the event of an engine compartment fire due to improper breather pipe assembly and drain box. Inadequate locking of the rear cargo door may allow door opening during flight. Inadequate attachment of the rudder control system components may lead to system damage under ground gust conditions. Inadequate retention of the piston tube in the main landing gear compression strut may cause structural failure. Inadequate fireproof integrity of the engine firewall due to aluminum rivets may increase fire risk. Inadequate support for the rudder quadrant hub assemblies may lead to structural failure. Inadequate retention of the oil delivery line from the Constant Speed Unit may result in oil loss and engine failure. Inadequate clamping of exhaust pipes may cause failure and fire hazard.
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Required Actions
Install cable jumper per DeHavilland Technical News Sheet Series Otter No. 22. Replace breather pipe assembly part C3-E-3-5 and drain box part C3-L-11 with parts C3-E-3-22 and C3-L-21. Install two additional clamps part C3-EE-18 and support strut C3-EE-42 on exhaust pipes. Install improved oil line assembly per Engineering Bulletin Series O No. 68. Replace aluminum rivets with monel rivets and install sixteen additional steel bolts per Engineering Bulletin Series O No. 72. Inspect fuselage former cap strips and install additional rivets if necessary. Install straps P/N C3-FF-351 or C3-FF-361-5 for rear cargo door locking. Inspect rudder control system for damage after ground gusts. Install additional AN 456AD-4-14 rivets on rudder quadrant hubs and replace elevator quadrant hubs with P/N C3-CF-126-7. Remove sintered metal filter assembly from flap hydraulic jack per Engineering Bulletin Series O No. 38. Alter landing gear with Technical News Sheet Series Otter No. 23. Install AN 43-17A eyebolts for cabin seat attachment. Install new axle pin P/N C3U5286-3 and bushing P/N C3U5287-3. Install tail wheel assembly components per Technical News Sheet Series Otter No. 6. Ensure compliance noted in aircraft log book with AD number reference.
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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