AD 90-17-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Enstrom Helicopter Corporation, The | 280 | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280C | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280F | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280FX | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28A | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28C | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28C-2 | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28F | Airworthiness Directives; ENSTROM HELICOPTER CORPORATION Model F-28F, F-28A, F-28C, F-28C-2, 280, and 280C Series Helicopters |
Unsafe Condition
Tail rotor drive shaft coupling failure due to wear and improper hardness could result in loss of directional control and possible loss of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Determine if splined couplings P/N 28-13609-1 are installed and logbook entries. Replace couplings with 1200+ hours' time in service before flight. Disassemble and inspect couplings with less than 1200 hours for wear, hardness, and cracks, then lubricate and reassemble. Repack couplings every 100 hours. Inspect and lubricate annually. Replace all P/N 28-13609-1 couplings before 1200 hours' time in service.
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Compliance Time
Within 5 hours' time in service after the effective date for initial determination; before further flight for removal and replacement actions; at intervals not to exceed 100 hours' time in service for repacking; and at each annual inspection for annual inspections.
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Affected Aircraft
Enstrom Helicopter Corporation Models F-28A, F-28C, F-28C-2, 280, 280C, F-28F (serial numbers 506, 507, 509-515, 517, 527, 700-704), and 280F (serial numbers 1212 and 1500).
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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