Developing a case for the implementation of a control augmentation system to improve flying qualities in the EA-6B aircraft

The EA-6B aircraft was designed and built in the late 1960s by the Grumman Aerospace Corporation for the United States Navy and Marine Corps to be used as a tactical electronic warfare (EW) platform. High losses of U.S. attack aircraft to surface-to- air missiles (SAMs) in Southeast Asia led to the requirement for a carrier-based tactical aircraft capable of providing EW support in the form of electronic jamming in support of strike aircraft. The EA-6B became the aircraft that fulfilled the EW requirement. Forty years have passed since the introduction of the EA-6B and the demand for the tactical EW capability continues to increase. Meeting these requirements has taken a toll oh the aircraft\u27s wing fatigue life, and has produced a shortage of the aircraft\u27s Automatic Flight Control System (AFCS) computer. The replacement computer contracted to correct the current problem of the aging analog AFCS computer is an up-to-date digital flight control computer (Model EA-6B Aircraft Program, 1995). The implementation of this computer will allow greater processing power and should be used to the full extent of its capability. An up-to-date flight control computer will cost less to repair, be readily replaceable, and will improve mission readiness and safety of flight. This thesis will build a case to use the additional processing power of the replacement digital flight control computer to improve flying qualities through a Control Augmentation System (CAS) that should have the effect in the following areas; 1. Limit accelerations during flight and thereby control the current problem of Fatigue Life Expenditure (FLE). 2. Improve flying qualities, specifically in the landing configuration with an emphasis to improve shipboard operations. With the current SAS the aircraft demonstrates less than satisfactory flying qualities in all axes (lateral, directional, and longitudinal) and configurations. 3. Limit Angle of Attack (AOA) in certain abnormal configurations, that are commonly encountered in the EA-6B, due to the aging airframe. The configuration that is particularly dangerous is the no slat-flaps down approach. This approach requires the pilot to maintain AGA precisely. The consequences of slowing one degree (equivalent to approximately 2 KIAS) below the recommended approach AGA will result in an uncontrollable pitch up (longitudinal instability) and subsequent departure from controlled flight (mandatory ejection criteria in this configuration) (EA-6B NATOPS Flight Manual, 1997). 4. Improve departure resistance by limiting angle of attack and controlling side-slip. Jamming pods are on all wing stations when the airplane is in the normal configuration. Departures that develop into spins frequently result in loss of the aircraft due to large inertia, forces, caused by the weight of the stores carried on the wings stations, which can not be overcome by the aerodynamic forces required for recovery