AD 53-12-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | UH-12 | Airworthiness Directives; Hiller Models UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B Helicopters |
| aircraft | Hiller Aviation | UH-12A | Airworthiness Directives; Hiller Models UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B Helicopters |
| aircraft | Hiller Aviation | UH-12B | Airworthiness Directives; Hiller Models UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B Helicopters |
Unsafe Condition
Fatigue failure of the horizontal stabilizer spar due to short spar inserts or absence of spar inserts in stabilizer assemblies P/N 37001.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace horizontal stabilizer assembly P/N 37001-9 (short spar inserts) after 300 hours total time with P/N 37001-14. Replace P/N 37001-7 (without spar inserts) after 1,600 hours total time with P/N 37001-12. Use stabilizers with long spar inserts (10.29 inches) attached via two AN 174-17 bolts.
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Compliance Time
Compliance required as indicated below: (a) 300 hours total time for P/N 37001-9; (b) 1,600 hours total time for P/N 37001-7.
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Affected Aircraft
Hiller Models UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B helicopters incorporating horizontal stabilizers with short spar inserts or without spar inserts.
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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