Airworthiness Directive · Amendment 39-17068 · Main rotor control
Enstrom Helicopter Corporation Helicopters
This AD applies to the Enstrom Model F-28C, F-28C-2, F-28F, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters with a trim relay, part-number (P/N) KUP14D55-24, KUP14D55-472, M83536/10-015M, or M83536/10-024M, certificated in any category.
Note to paragraph (a) of this AD: This AD does not apply to the specified helicopters with a reversible trim motor, P/N 28-16621 (Ford Motor Company C1AZ-14553A) or P/N AD1R-10 (Signal Electric).
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.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
Within 5 hours time-in-service (TIS) or at the next annual or 100 hour TIS inspection, whichever occurs first:
(1) For the Enstrom Model F-28C, F-28C-2, F-28F, 280C, 280F, and 280FX helicopters, modify the lateral and longitudinal trim actuator assemblies using the cyclic trim assembly kit (modification kit), P/N 28-01063-1, in accordance with the instructions in paragraph 6.1 of the Enstrom Service Directive Bulletin (SDB) No. 0110, Revision 4, dated January 23, 2012 (SDB No. 0110 R4), except when the instructions specify using “Aeroshell 22 grease” or “VC-3 Vibra-tite thread locker,” you may use an equivalent product.
(2) For the Enstrom Model TH-28, 480, and 480B helicopters, modify the lateral and longitudinal trim actuator assemblies using the modification kit, P/N 4230045-1, in accordance with the instructions in paragraph 6.1 of the Enstrom SDB No. T-039, Revision 3, dated July 6, 2011 (SDB No. T-039 R3), except when the instructions specify using “Aeroshell 22 grease” or “VC-3 Vibra-tite thread locker,” you may use an equivalent product, and you are not required to contact Enstrom Customer Service.
(3) After modifying the lateral and longitudinal trim actuator assemblies in accordance with paragraphs (f)(1) or (f)(2) of this AD, before further flight, operationally test the trim limits in accordance with paragraph 6.2. of the SDB for your model helicopter, and determine during a flight test whether there is appropriate trim authority in accordance with paragraph 6.3. of the SDB for your model helicopter.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
