Extensive research on human vision has led to the emergence of clear design requirements to insure that pilots of combat aircraft can best view new multifunction displays (MFDs). An illuminance profile of an F-16C was conducted by Tektronix, Inc., Beaverton, Oregon supplier of CRTs for the MFD, in an F-16C parked on the runway at General Dynamics, followed by flight tests at 40,000 ft. Human visual requirements (Table I) indicate that a series of tradeoffs must be made in the design of the CRT to optimize display luminance, contrast ratio, color differentiability and symbol legibility. On the ground it was found that only at a narrow angle of incidence can direct sunlight shine on the aircraft MFDs. In flight it was also found difficult to even maneuver the aircraft to a position where direct sunlight shown on the MFD. Even then it was required that the pilot assume an unusual sitting position to allow sunlight to flood the MFD. Based on these ambient illumination tests, it is suggested that the engineering design guidelines for the F-16C cockpit use a value of 5000 foot-candles as a worst-case ambient for the current MFD location, and 7600 foot-candles for worst-case anywhere within the cockpit, to insure maximum avionics display viewability.