POWER ASSIST CONTROLS

In the early days of flight, the aerodynamic controls (ailerons, elevators, rudder) were directly connected to the cockpit via cables, and the pilot had to use physical force to operate these controls. As the speeds of airplanes increased, the aerodynamic forces became larger and required more physical force from the pilot to operate the controls. With the advent of high-speed jet flight, these forces
became too large for the pilot to overcome, and hydraulically boosted controls were introduced (much like power steering in your automobile). For the X-15, the power assist controls that gave force amplification to the pilot were effective; they were used by the pilots when the aerodynamic forces were high at the lower altitudes.

The power assist controls were used throughout by some of the pilots who did not use the conventional center stick and who only used the force amplification controls. The MH-96 also blended this control with the rocket controls, which were used when the air density was so low that the aerodynamic controls were ineffective because of the high altitude and resulting low dynamic pressure. It made the transition from aero control to rocket automatic. For use in future hypersonic aircraft, and in the Space Shuttle that actually followed, it simplified the piloting when flying in these varied regions of aerodynamic force. The X-15 demonstrated that airplanes in these regions, even while rapidly traversing from one region to another with high accelerations and decelerations, could be flown safely by trained pilots.