Commonwealth legislation

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

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Commonwealth

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legislative instrument

Plain English Summary

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This directive requires EMB‑120 operators to check that the movable backstop on the pitch‑trim control wheel sits properly in its spiral groove and that the trim tab travels correctly, and to fit a support/guide to retain the backstop — actions to be done per Embraer Alert Service Bulletin 120‑27‑A081 change 1.

Operators must do the inspection soon after the effective date and the modification within a slightly longer window; they bear the cost and operational downtime, while the rule aims to prevent autopilot disengagement and sudden pitch‑up events reported during descent.

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Current sections

Direct links to the current provisions in AD/EMB-120/21 - Elevator Pitch Trim System.

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

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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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.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

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