AD/ENST 28/37 - Voltage Regulator (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

Enstrom F-28 Series Helicopters

AD/ENST 28/37 Voltage Regulator 13/97

Applicability: Model F-28A; 280; F-28C helicopters, with a serial number less than S/N 745; and Model 280C helicopters, with a serial number less than S/N 1502.

Requirement: 1. Determine if a Prestolite-manufactured voltage regulator, part number (P/N) VSF7203, or Prestolite-manufactured over-voltage relay, P/N X16799, P/N X17621, or P/N FOC-4002A, is installed. If any of these parts are installed, perform the following:

1. Determine if the alternator output is within the proper output voltage range (13.8 to 14.4 volts) and, if the alternator output voltage is not within the proper voltage range, adjust or replace the voltage regulator, and,

b. in accordance with paragraph 6.3.3 of Enstrom Helicopter Corporation SDB No. 0086, dated 31 March 1996, conduct an operational test of the over-voltage relay and replace the over-voltage relay if required.

2. If no over-voltage relay is installed:

1. Install an over-voltage relay, P/N FOC-4002A, in accordance with paragraph 6.3.4. of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0086, dated 31 March 1996.

OR

b. Install the transistorised voltage controller, P/N ECD-069-11, and modify the wiring in accordance with paragraph 6.4 of Enstrom Helicopter Corporation SDB No. 0086, dated 31 March 1996.

Note: The installation of the transistorised voltage controller is considered terminating action for the requirements of this AD.

3. Check the amp meter for readings within the normal operating range while the helicopter engine is operating at 2,200 revolutions per-minute (RPM).