The Utility of Analog Vertical Velocity Information During Instrument Flight with a Head-Up Display (HUD)

Abstract : The United States Air Force (USAF) is attempting to create a standard symbol set for use with the HUD as a primary flight reference. As part of that effort, eight HUD-experienced pilots and twelve non-HUD-experienced pilots participated in a study that examined the effects of variations in vertical velocity indicators (VVI) for use under instrument flight conditions in a simulator. Five configurations were assessed: digital readout, boxed digits with tape, dial, altimeter arc, and altimeter arc with digital readout. The results clearly indicated that the altimeter arc with digital readout, and the altimeter arc alone, resulted in significantly more accurate maintenance of flight parameters (i.e., vertical velocity and altitude) than did the digital readout alone, the boxed digits with tape, or the dial. Subjective data supported the objective findings, in that pilots preferred either configuration that included the altimeter arc. These findings suggest that analog vertical velocity information is useful on the HUD, particularly when it is located in close proximity to the altimeter.