Volpe Center: Human Factors Division

PROJECTS:

GPS Vertical Navigation Cockpit Displays

The goal of this project is to understand the human factors issues for Vertical Navigation (VNAV) displays, particularly relatively simple ones which might be incorporated in GPS area navigation equipment used by general aviation, air taxi, and regional airlines which lack full autoflight systems.

Judith Bürki-Cohen, Ph.D., Project Manager

Project Details

Global Positioning System (GPS) satellite based area navigation systems are revolutionizing air traffic control. Many aircraft are now equipped with GPS systems for enroute navigation in an earth-horizontal plane (HNAV), and for non-precision approaches, using conventional altimetry for descent. Even more accurate differential GPS systems are in development which eventually will replace the conventional precision Instrument Landing System (ILS). Aircraft accident research indicates that the incidence of Controlled Flight Into Terrain (CFIT) accidents is reduced if aircraft have both horizontal and vertical navigation capability, and ground proximity warning systems. However, generally only glass cockpit equipped airliners are so equipped today. The GPS navigation systems used by many aircraft have flexible electronic displays, updatable databases. The addition of VNAV functions could potentially make flying both easier and safer, provided that the human factors aspects of VNAV displays and controls have been properly considered at the design stage.

We are currently studying pilot performance and workload using displays which present aircraft position and velocity information in both the horizontal and vertical planes on a small instrument panel mounted multifunction computer (Avidyne) with a quarter VGA color screen. In the parlance of manual control engineering, these displays help pilots create "outer loop lead". The displays do not utilize attitude information, so they can be implemented in present generation systems simply by software changes. Displays are developed and tested in a Volpe flight simulator, and then functionally demonstrated in actual flight aboard a Volpe research aircraft.

As shown below, formats include a fully numeric display; a moving map with an altitude range arc; and a supplementary profile display which includes a vertical flight path predictor and shows range to altitude intercept. All displays automatically present information on minimum/maximum leg altitudes.

Screen capture of the fully numeric display

Numeric VNAV Display Format:

Altitude Clearance Limit at Next Waypoint