We are superseding an existing airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28C, F-28C-2, F- 28F, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters to add another trim relay to the applicability and to revise the modification instructions. This AD is prompted by the discovery that another part- numbered trim relay, inadvertently omitted from the current AD, may contain the same unsafe condition. These actions are intended to prevent failure of the cyclic trim system and subsequent loss of control of the helicopter.
Agency Contact: Gregory J. Michalik, Enstrom Program Manager, FAA, Chicago Aircraft Certification Office, 2300 East Devon Avenue, Room 107, Des Plaines, Illinois, 60018; telephone (847) 294- 7135; email: firstname.lastname@example.org.
This rule is final. Its effective date is July 3, 2012.