Airworthiness Directives; Enstrom Helicopter Corporation Model F- 28A, F-28C, 280 and 280C Helicopters

This amendment adopts a new airworthiness directive (AD) that is applicable to Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280 and certain serial-numbered F-28C and 280C helicopters. This action requires an inspection of the voltage control system and an owner/ operator (pilot) cockpit check of the amperage of the electrical system. If certain Prestolite-manufactured components are installed, additional tests and actions are required before further flight and at each pre-flight run-up and annual inspection thereafter. A terminating action is provided by replacing the existing voltage control system with a transistorized system. This amendment is prompted by 14 reports of voltage control system problems, including one incident in which smoke emanated from the radio panel during flight, forcing the pilot to make an emergency landing. The actions specified in this AD are intended to prevent an electrical overload and a failure of the voltage regulator and over-voltage relay, that could result in an inflight fire, and subsequent forced landing of the helicopter.