Single axis autopilot: This type of autopilot can only automate the roll axis of the aircraft. They keep the level of the wing constant hence stabilizing the altitude and direction of the aircraft.They keep the aircraft in a single line of motion and cannot handle a complex flight path.
Two Axis Autopilot:
A two-axis autopilot is somewhat more utilitarian when compared to a single axis autopilot as it can control both the pitch and roll of the aircraft. It can also be connected to an onboard radio guidance system and can efficiently fly the aircraft shortly after and before landing. They cannot aid a pilot in landing and take.
A three-axis autopilot system can control the pitch, roll, and yaw of the aircraft in real time and is used for long-haul aircraft which fly complex routes and have a greater flight time.
In a modern aircraft chances of having a three-axis autopilot are great. Three-axis autopilot system can control most of the stages of a flight and is an integral part of overall flight management system. This can also be termed as the modern autopilot system as its function is divided into many stages.