A laboratory test facility has been developed to apply full-scale lightning and EMP fields to safety-critical digital flight control systems early in the development process. Such testing enables relatively low-cost evaluation of system susceptibility, allows in-depth study of the effects of disturbances, and provides essential feedback to system engineers attempting to harden the design. Results indicate that: ○ Proper design practice results in systems that can tolerate fields associated with lightning strikes or EMP to levels projected within a metal-skinned aircraft. ○ Lightning/EMP tests do uncover design faults and are of value early in the development process. ○ Optical data bus mechanization outperformed a conventional wire bus in high-level transient fields, as expected.