AD 81-17-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12 | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12A | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12B | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12C | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L4 | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E-L | Airworthiness Directives; HILLER AIRCRAFT Model UH-12 Series Helicopters |
Unsafe Condition
Failure of the main transmission due to magnetic chips or gold colored flecks in the oil filter and chip detector.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the main transmission oil filter and chip detector per Hiller Service Notice No. 23-2. If chips or gold flecks are found, open transmission, inspect planetary system, replace worn parts, clean filter, replace parts, and logbook entry. Inspect every 25 or 50 hours depending on engine type. Replace P/N 23586-3 spacers within 1200 hours or next 100 hours.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 25 hours' additional time in service from the effective date of this AD for initial inspection. Subsequent inspections every 25 hours' time in service for turboshaft and 50 hours for reciprocating engine aircraft. Replace spacers prior to 1200 hours' time in service or within the next 100 hours after the effective date.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Hiller Aircraft Model UH-12 all series helicopters with Main Transmission P/Ns 23500-3 and 23700-3, -5, -7 or -9, including Soloy Conversions STCs SH177WE and SH178WE.
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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