An avionics system for a mechanically-controlled aircraft configured to provide envelope protection for deterring a pilot from flying outside of acceptable flight parameter limits for flight parameters such as banking angle, pitch attitude, g loading, proximity to terrain and/or obstacles, angle of attack, and/or airspeed. The avionics system may comprise at least one servo actuator and a computing device. The computing device may engage envelope protection by engaging the at least one servo actuator if the aircraft reaches a maximum or minimum limit for any of the flight parameters, such that the at least one servo actuator provides a force to urge a flight control device in a direction to bring the aircraft back within the acceptable flight parameter limits. The servo actuator may be disengaged when the aircraft flight parameters reach an end value corresponding to the start value that triggered envelope protection to engage.