AD 63-21-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; Hiller Models UH-12D and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; Hiller Models UH-12D and UH-12E Helicopters |
Unsafe Condition
Fatigue cracking and brazed doubler separation of main rotor blades, Parsons P/N's 2253-1101-02 and 2253-1101-03, near the outboard end of the steel doubler brazed to the leading edge spar.
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Required Actions
Inspect top and bottom surfaces of each blade with a 4 to 6-power magnifying glass within 10 hours' time in service from the effective date and daily thereafter. Conduct dye penetrant inspections within 10 hours' time in service after October 15, 1963, and at intervals not exceeding 25 hours (for blades Serial Number 1269 and below) or 100 hours (for blades Serial Number 1270 and above) from the last inspection. Inspect for cracks in the main rotor blade fork bolt hole and adjacent surfaces via dye penetrant if unusual vibration occurs, replace cracked forks before flight. Remove blades with cracks or separation from service before further flight.
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Compliance Time
Compliance required as indicated.
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Affected Aircraft
Hiller Models UH-12D and UH-12E Helicopters with main rotor blades Parsons P/N's 2253-1101-02 and 2253-1101-03.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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