Abstract: An aircraft head-up unit includes a collimator that is automatically swung upwards out of the pilot's ejection envelope by an actuator, driven by gas pressure from an ejector seat mechanism. The collimator is supported by a first frame, and the actuator is supported by a second frame on which the first frame is pivotally mounted. The frames are held in position by spring detents, which can be overcome by an upward or downward impact. The collimator has a concave surface bearing a holographic element and is mounted below the pilot's line-of-sight, with a CRT display. A reflector, mounted above the line-of-sight, reflects a display image from the CRT display, through a combiner, to the collimator. The collimator reflects the display image to the combiner which directs it into the pilot's line-of-sight.