AD/AMD 20/12 - Horizontal Stabiliser Trim Control Switch Connections

This safety rule requires operators of specific Falcon 20 business jets to correct a wiring issue with the aircraft's pitch control system.

Who it affects Owners and operators of AMD Fan Jet Falcon 20 series aircraft that are equipped with an automatic pilot (autopilot) or optional circuits connecting to the horizontal trim control switch wiring.

What it requires Operators must carry out technical actions in accordance with AMD Service Bulletin 568, Revision 2 to ensure the horizontal stabiliser trim control switch connections are properly configured. This specifically addresses electrical circuits connected to the "normally closed" contacts of the trim switches — the wiring that should be complete when the trim button is not being pressed.

Why it matters Faulty connections in the trim control system could cause unexpected trim movement or autopilot malfunctions, potentially compromising the aircraft's controllability and flight safety.

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

View image in the official source AMD Fan Jet Falcon (Falcon 20/Mystere-Falcon 200) Series Aeroplanes

AD/AMD 20/12 Horizontal Stabiliser Trim Control

Switch Connections

4/77

Applicability: All models fitted with an automatic pilot or any optional circuit that connects to horizontal trim control switch normally closed contacts.

Requirement: Action in accordance with AMD SB 568, Rev. 2 (27-74).

Note: Bureau Veritas 76-219-13 (B) refers.

Compliance: Within 200 hours time in service after 30 April 1977.