AD/EMB-120/21 - Elevator Pitch Trim System (Cth)

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

Embraer EMB-120 (Brasilia) Series Aeroplanes

AD/EMB-120/21 Elevator Pitch Trim System 1/98

Applicability: All models EMB-120 aircraft.

Requirement: Action in accordance with Embraer Alert Service Bulletin 120-27-A081 change 1:

Part I: A check to verify the proper installation of the movable backstop into the spiral groove on the pitch trim right control wheel, and the correct travel of the pitch trim tab surface.

Part II: Installation of a support/guide to maintain the moveable backstop inside the spiral groove, on the control pedestal structure.

Note: CTA AD 97-09-08R1 Amdt 39-811 refers.

Compliance: For Part I: Unless already accomplished in accordance with the initial issue of the Requirement document, within 20 hours time in service after 1 January 1998.

For Part II: Unless already accomplished, within 75 hours time in service after 1 January 1998.

This airworthiness directive becomes effective on 1 January 1998.

Background: Reports were received of occurrences of a sudden reversion of the elevator pitch trim tab, during the descent phase, with the automatic pilot engaged in descent mode. The reports indicated that, when the trim control wheel reached the pitch down stop, the auto pilot disengaged and the aircraft suddenly reverted to a pitch up attitude, requiring prompt pilot action to control the aircraft.