AD 81-18-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12 | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12A | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12B | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12C | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L4 | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E-L | Airworthiness Directives; HILLER AVIATION Model UH-12 Series Helicopters |
Unsafe Condition
Tail rotor skin cracks and loose rivets can lead to tail rotor failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Visually inspect tail rotor blades for cracks or loose rivets and replace with serviceable parts if found. Inspect four vent holes in tail rotor blades for obstructions, replace blade if root vent holes are blocked, and clear tip vent holes if unblocked. Conduct pre-flight visual checks of vent holes before each flight and take corrective actions if obstructions are found.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to further flight after the effective date of this AD
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Hiller Aviation and Siam Hiller Holdings, Inc. models UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12L, UH-12L4, UH-12E, UH-12E-L, including military models H-23F and OH-23G
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
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.