Microwave induced upset of digital flight control systems

Recent tests of flight control system components show that digital flight control systems are vulnerable to microwave signals, but only at very high power levels, well above that produced by commercial radar installations. Test results of sensors, computers, data busses, and actuators reveal that long standing fears of inherent fly-by-wire flight control system vulnerability to microwave radiation are unfounded. Some components, such as sensors and data busses, aren't affected at all. Others, such as the digital computers, fail at high power levels. The tests show that as long as the component shielding remains intact, component vulnerability is minimized. Good EMI design will give a harder system than simply relying on supposedly "EMI Proof" technologies, such as fiber optics. Testing revealed that inadequately designed fiber optic systems can actually reduce the system hardness to EMI. One conclusion is that the system shielding should be design controllable, that is, distributed between the airframe and component. >