A system is provided for increasing autopilot control authority in a vehicle, such as aircraft including mechanical control systems. The system includes an autopilot system, a control element and an autopilot supplement assembly. The autopilot system can automatically control the vehicle by applying a variable autopilot force to control surfaces. The control element can control the vehicle by applying a variable control force to control surfaces, where the control force acts counter to the autopilot force. The autopilot supplement assembly can measure the control force and, in turn, determine a variable supplemental force. Thereafter, the autopilot supplement assembly can apply the supplemental force to the control surfaces such that the sum of the supplemental force and the autopilot force is greater than the control force. Thus, the system may provide the benefits of systems that require full control authority to vehicles such as aircraft that include mechanical control systems.