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4-3 Autothrottle

The autothrottle master switch is turned off when the TRC Auto mode is selected.
Speed Mode (SPD)
When the SPD mode is active, the autothrottle controls the engines to maintain the airspeed, selected in the SPD/MACH window.
The SPD mode automatically activates when any of the vertical modes is selected and the autothrottle (A/THL) master switch is on.
Mach Mode (SPD)
The Mach Hold Mode can be enabled by pressing the round button right of the SPD Select window.