Final answer:
In a complex airplane, the throttle controls the engine's power output, which affects the speed and altitude of the airplane.
Step-by-step explanation:
In a complex airplane, the throttle controls the engine's power output. The throttle is a lever or a knob that the pilot can push forward or pull backward to adjust the amount of fuel going into the engine.
By increasing or decreasing the fuel flow, the throttle controls the speed of the engine and, consequently, the speed and altitude of the airplane.
For example, when the pilot pushes the throttle forward, it increases the fuel flow into the engine, causing the engine to produce more power. This results in the airplane accelerating and gaining altitude. Conversely, when the pilot pulls the throttle backward, it reduces the fuel flow and decreases the engine's power, causing the airplane to slow down and descend.
In a fly-by-wire system like the one used in the Boeing 777, the throttle inputs from the pilot are converted into electrical signals that control the engine's power output. These electrical signals are then transmitted to actuators that adjust the fuel flow and engine settings accordingly.