In a complex airplane, what does the throttle control?

The throttle in a complex airplane primarily controls the engine manifold pressure. Manifold pressure is a measure of the pressure of the air-fuel mixture entering the engine's cylinders and is crucial for determining engine power output. When the throttle is advanced, more air and fuel are allowed into the engine, increasing manifold pressure and consequently raising engine power. Conversely, reducing the throttle decreases the manifold pressure, leading to reduced engine speed and power.

In complex aircraft, which often feature high-performance engines with more sophisticated management systems, the throttle control is integral to managing engine performance effectively during various phases of flight. Understanding this relationship is essential for pilots, as it enables them to optimize engine settings for fuel efficiency, performance, and safety.

The other options reflect different concepts associated with flying, but they are not directly governed by the throttle control. Engine speed is affected by manifold pressure, but it is not the direct function of the throttle itself. Airframe efficiency relates more to aerodynamic design and flight attitudes rather than throttle control. Altitude stability concerns the overall aircraft performance and control but is not influenced directly by the throttle positioning like manifold pressure is.