AD 97-20-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Enstrom Helicopter Corporation, The | 280 | Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, 280 and 280C Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | 280C | Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, 280 and 280C Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28A | Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, 280 and 280C Helicopters |
| aircraft | Enstrom Helicopter Corporation, The | F-28C | Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, 280 and 280C Helicopters |
Unsafe Condition
Failure of the Prestolite-manufactured voltage regulator, part number VSF7203, or over-voltage relays, part numbers X16799, X17621, or FOC-4002A, could result in an electrical overload and overheating of system wiring and components, leading to an inflight fire and forced landing.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within 5 hours time-in-service, inspect the voltage control system for Prestolite components and test over-voltage relay operation. Before each flight, check amp meter readings. At each annual or 100-hour inspection, test alternator voltage and over-voltage relay. Replace or adjust components as needed. Install over-voltage relay if missing. Terminate by replacing the voltage control system with a transistorized system (P/N ECD-069-11).
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Compliance Time
within 5 hours time-in-service
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Affected Aircraft
Enstrom Helicopter Corporation Model F-28A, 280, F-28C (serial number less than 745), and 280C (serial number less than 1502) helicopters.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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