AD 52-01-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | UH-12 | Airworthiness Directives; Hiller Models UH-12, -12A and -12B Helicopters |
| aircraft | Hiller Aviation | UH-12A | Airworthiness Directives; Hiller Models UH-12, -12A and -12B Helicopters |
| aircraft | Hiller Aviation | UH-12B | Airworthiness Directives; Hiller Models UH-12, -12A and -12B Helicopters |
Unsafe Condition
Failure of the main rotor blade collective pitch incidence arms (P/N 31114-1) due to possible minute cracks in the circumferential area of the flange radii.
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Required Actions
Inspect main blade incidence arms (P/N 31114-1) to determine if chrome plated arms are installed. If installed, remove and magnaflux or magnaglow inspect each arm for cracks. Replace arms immediately if cracks are found; reinspect at 100 hours service if under 100 hours, or comply with inspection intervals as specified.
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Compliance Time
Not later than the next 25-hour inspection or February 1, 1952, whichever occurs first.
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Affected Aircraft
Hiller Models UH-12, -12A, and -12B helicopters, serial numbers 104 and up, with chrome plated main rotor blade incidence arms P/N 31114-1.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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