Other avionics include an autopilot and yaw damper. The flight crews then disengaged the autopilot and the yaw damper. It may also be used to engage or disengage both the autopilot and the autothrottle. The cockpit was provided with a modified Lear MC-1 autopilot. The basic type lacked features such as an autopilot, inertial navigation, or a radar. The control system was duplicated in flying control units which received pilot and autopilot demands. Each mission can be played with the aircraft on autopilot or manual control. The pilots felt a jolt, and the autopilot disengaged. Most F-111 variants included a terrain-following radar system connected to the autopilot. UAV software called the flight stack or autopilot. Airbus offers the option of an autopilot/flight director TCAS for automatic avoidance maneuvers. It needs a fail-passive autopilot. The Flight Data Recorder recorded an attempt to engage the autopilot. The system relies on most of the same hardware and software used in autopilot mode. The ability is available to those who have purchased Enhanced Autopilot or Full Self-Driving Capability.