AD 72-11-04

72-11-04 ENSTROM: Amdt. 39-1452. Applies to Model F-28A (Serial Numbers 1 through 83) helicopters.

Compliance: Required as indicated, unless already accomplished.

To prevent failure of tail rotor drive taper pins with subsequent loss of directional control, accomplish the following:

A) Unless Paragraph B has been accomplished, within 10 hours' time in service after the effective date of this AD visually inspect the 2 forward and 3 aft AN386 taper pins installed in the tail rotor drive shaft assembly for looseness. Prior to further flight replace all loose taper pins with AN386-2-8A taper pins acquired from either the Enstrom Factory Customer Service Department, or Enstrom Dealers in accordance with Enstrom Service Note No. 0011 dated March 29, 1972, or by any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Great Lakes Region.

NOTE: Loose pins can be detected by:

1. Wiggling the pin with the fingers.

2. Grasping the tail rotor drive shaft with the hand and rotating the shaft back and forth while observing the movement of the pin in the mating hole.

3. Examining for loss of paint on the pin at the edge of the mating hole.

4. Examining for formation of a burr at the edge of the hole.

B) Within 25 hours' time in service after the effective date of this AD, replace all AN386 taper pins installed in the tail rotor drive shaft assembly with AN386-2-8A taper pins acquired from either the Enstrom Factory Customer Service Department, or Enstrom Dealers in accordance with Enstrom Service Note No. 0011 dated March 29, 1972, or by any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Great Lakes Region.

This amendment becomes effective June 1, 1972.