AD 90-01-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Enstrom Helicopter Corporation, The | 280 | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280C | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280F | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280FX | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28 | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28A | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28C | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28C-2 | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28F | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280FX Series Helicopters |
Unsafe Condition
Loss of tail rotor thrust and directional control due to metal contaminants in the tail rotor gearbox containing spiral miter gear-set 'Boston Gear XR-137-2YR' and 'Boston Gear XR-137-2YL'.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within five hours' time in service, inspect tail rotor gearboxes for installed part numbers and metal contaminants. Replace gearboxes with 1,200+ hours' time since overhaul or exhibiting excessive metal particles. Conduct recurring inspections at intervals not exceeding 100 hours' time in service and mandatory replacement within 1,200 hours' time since last overhaul.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next five hours' time in service
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Enstrom Helicopter Corporation Models F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX Series Helicopters equipped with tail rotor gearboxes P/N 28-13500-1, 28-13525-1, -3, and -5 containing spiral miter gear-sets 'Boston Gear XR-137-2YR' and 'Boston Gear XR-137-2YL'.
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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