The flight envelope of an aircraft is the range of speeds and altitudes at which the aircraft is able to fly safely. The system can be operated manually or automatically, and can control all or part of the flight envelope.
Automatic systems are typically used for flying in controlled airspace, such as near airports. They help to keep the aircraft within a safe operating range by automatically controlling its speed and altitude. Manual systems may be used in uncontrolled airspace, such as over open ocean, where there are no set limits on speed or altitude. In these cases, the pilot must use their judgment to stay within a safe operating range.
The flight envelope protection system is a safety feature that is designed to prevent the aircraft from being operated outside of its safe operating limits. It is usually made up of sensors and computerized controls that monitor the speed and altitude of the aircraft. If the sensors detect that the aircraft is approaching or exceeding its operational limits, they will activate the appropriate control surfaces or engines to bring it back into a safe range.
While most modern aircraft are equipped with some form of flight envelope protection system, they are not infallible. Pilots must still exercise caution when operating near the edge of their aircraft's performance capabilities. In some cases, such as during severe weather conditions or when flying in mountainous terrain, it may be necessary to disable the system in order to maintain control of the aircraft.