AD 97-20-15
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12A | Airworthiness Directives; Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12B | Airworthiness Directives; Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12C | Airworthiness Directives; Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters |
Unsafe Condition
Cracks in the head area of the outboard tension-torsion (T-T) bar pin could result in loss of in-plane stability of the main rotor blade and subsequent loss of control of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the alignment of the outboard T-T bar pin and adjust if necessary; inspect the head of the outboard T-T bar pin for cracks using dye penetrant or magnetic particle inspection; install shims between the inboard end of the drag strut and the outboard T-T bar pin. Report inspection results to the FAA within 7 working days if cracks are found.
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Compliance Time
Within 25 hours time-in-service (TIS) after the effective date of this AD, or at the next 100 hour inspection, whichever occurs first. Thereafter, inspections must be repeated at intervals not to exceed 100 hours TIS.
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Affected Aircraft
Hiller Aircraft Corporation Model UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E helicopters, certificated in any category.
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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