A comparison of the use of classical and modern control design techniques for improving the lateral-directional powered approach flying qualities of the F-14 aircraft

Due to the limitations of its analog flight control system, the F-14 aircraft exhibited several major flying qualities deficiencies. To correct these deficiencies, the Department of the Navy instigated a program to replace the analog system with digital flight control computers incorporating enhanced control laws. A new control law was designed for the powered approach configuration (landing phase) using classical control techniques, and demonstrated greatly improved flying qualities in piloted simulator testing. To determine if further increases in system performance were realizable, an advanced multivariable control system was designed. Although the multivariable control law design resulted in excellent flying qualities, a significant improvement was not realized over the classically designed system and therefore should not be considered for implementation into the actual flight control software.