What does the ALT knob on the Flight Guidance Panel (FGP) set?

The ALT knob on the Flight Guidance Panel (FGP) is used to set a reference altitude, which is typically indicated in cyan on the display. This function allows pilots to input their desired altitude for the aircraft to maintain during flight. By setting this altitude, the autopilot system can manage the vertical navigation and ensure that the aircraft climbs to, descends to, or maintains the specified altitude as necessary during various phases of flight.

In the context of aviation operations, having a clear and distinct reference altitude is crucial for maintaining safe separation from other aircraft and for complying with air traffic control instructions. The use of a cyan display helps pilots quickly identify the set altitude against other flight parameters to improve situational awareness.

The other choices represent different flight parameters that, while related to altitude control in some sense, are not specifically set with the ALT knob. Flight level refers to a specific altitude expressed in hundreds of feet, often used in air traffic control communication. Vertical speed measures the rate of climb or descent but is not set using the ALT knob; instead, it may be controlled by the autothrottle or other systems. Rate of climb specifically refers to how quickly an aircraft is gaining altitude and would be influenced by other flight management systems rather than directly set by