Airworthiness Directive · Amendment 39-16900 · Main rotor control
Enstrom Helicopter Corporation Helicopters
Superseded. A later AD replaced this one: AD 2012-11-05. Comply with the one in force.
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) KUP14D55-472, M83536/10-015M, or M83536/10-024M, certificated in any category.
Note 1: 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 adopting a new 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 with certain trim relays to require modifying and testing the lateral and longitudinal cyclic trim actuator assemblies. This AD was prompted by four failures in the cyclic trim system on certain Enstrom model helicopters that resulted in reduced controllability of the helicopter. 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 TIS inspection, whichever comes 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 3, dated July 6, 2011 (SDB No. 0110 R3), 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 (e)(1) or (e)(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.
