What is the correct pecking order for operation of the stab trim from highest to lowest?

• A. Pilot, Co-Pilot, Autopilot, Auto trim, Mach trim
• B. Pilot, Autopilot, Co-Pilot, Mach trim, Auto trim
• C. Co-Pilot, Pilot, Autopilot, Auto trim, Mach trim
• D. Auto trim, Pilot, Co-Pilot, Autopilot, Mach trim

Answer: (A)

Stab trim is controlled by multiple sources, and the system is designed so the most direct human input takes precedence. The captain’s trim input has the highest priority, so any trim requests from the pilot override other trim commands. If the captain isn’t actively trimming, the copilot’s trim input is the next in line. When there’s no manual input from either pilot, the autopilot’s trim commands take effect. If the autopilot isn’t providing trim, the automatic trim system then takes over to reduce the crew’s workload. Mach trim is the lowest priority, kicking in only to adjust trim in response to changes in Mach number and will not override manual or autopilot trim. This ordering ensures pilots retain control, automated systems assist without overriding manual input, and specialized Mach-based adjustments remain a fallback.