The integrated flight control system integrates and merges  various systems into a system operated and controlled by one  principal component.  Figure 5-41  illustrates key components  of the flight control system that was developed from the  onset as a fully integrated system comprised of the airframe,  autopilot, and FDS. This trend of complete integration, once  seen only in large commercial aircraft, is now becoming  common in general aviation. An autopilot is a mechanical means to control an aircraft  using electrical, hydraulic, or digital systems. Autopilots can  control three axes of the aircraft: roll, pitch, and yaw. Most  autopilots in general aviation control roll and pitch.  Autopilots also function using different methods. The first  is position based. That is, the attitude gyro senses the degree  of difference from a position such as wings level, a change  in pitch, or a heading change. Determining whether a design is position based and/or rate  based lies primarily within the type of sensors used. In order  for an autopilot to possess the capability of controlling an  aircraft’s attitude (i.e., roll and pitch), that system must be  provided with constant information on the actual attitude  of that aircraft. This is accomplished by the use of several  different types of gyroscopic sensors. Some sensors are  designed to indicate the aircraft’s attitude in the form of  position in relation to the horizon, while others indicate rate  (position change over time).  Rate-based systems use the turn-and-bank sensor for the  autopilot system. The autopilot uses rate information on  Figure 5-43  is a diagram layout of a rate-based autopilot by  S-Tec, which permits the purchaser to add modular capability  form basic wing leveling to increased capability.  two of the aircraft’s three axes: movement about the vertical  axis (heading change or yaw) and about the longitudinal  axis (roll). This combined information from a single sensor  is made possible by the 30° offset in the gyro’s axis to the  longitudinal axis.  Other systems use a combination of both position and rate- based information to benefit from the attributes of both systems  while newer autopilots are digital.  Figure 5-42  illustrates an  autopilot by Century. Integrated Flight Control System  Autopilot Systems Figure 5-42. An Autopilot by Century. Figure 5-41. The S-TEC/Meggit Corporation Integrated Autopilot installed in the Cirrus. 5-25