an option midway between fully automated flight and manual flying is control wheel steering (cws). although it is becoming less used as a stand-alone option in modern airliners, cws is still a function on many aircraft today. generally, an autopilot that is cws equipped has three positions: off, cws, and cmd. in cmd (command) mode the autopilot has full control of the aircraft, and receives its input from either the heading/altitude setting, radio and navaids, or the fms (flight management system). in cws mode, the pilot controls the autopilot through inputs on the yoke or the stick. these inputs are translated to a specific heading and attitude, which the autopilot will then hold until instructed to do otherwise. this provides stability in pitch and roll. some aircraft employ a form of cws even in manual mode, such as the md-11 which uses a constant cws in roll. in many ways, a modern airbus fly-by-wire aircraft in normal law is always in cws mode. the major difference is that in this system the limitations of the aircraft are guarded by the flight computer, and the pilot cannot steer the aircraft past these limits.