AD 51-20-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | UH-12 | Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft |
| aircraft | Hiller Aviation | UH-12A | Airworthiness Directives; Hiller Models UH-12 and UH-12A Aircraft |
Unsafe Condition
Protrusion of the bushings from the collective pitch ballast system bracket P/N 31125-1, leading to reduced main rotor blade pitch range and restricted controllability.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Visually inspect the collective pitch ballast system bracket P/N 31125-1 for protrusion of bushings P/N 31120-1 as soon as possible but not later than September 1, 1951, and every 25-hour inspection period thereafter. If protrusion occurs, rework the assembly by installing set screws per United Helicopters Mandatory Bulletin No. 19. Discontinue inspections after rework is completed.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
As soon as possible but not later than September 1, 1951, and at each 25-hour inspection period thereafter
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Hiller Models UH-12 (Serial Numbers 105 to 135, Inclusive) and UH-12A (Serial Numbers 136 to 176, Inclusive, and 178, 180 and 181) with the Collective Pitch Ballast System.
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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