By J. Mac McClellan, EAA Director of Publications
For many years a head-up display (HUD) was only available to military fighter pilots. But Rockwell Collins brought HUD technology to civilians, and the results are safer flying in the worst conditions of darkness and low visibility.
A HUD is a magical piece of glass mounted between a pilot's eyes and the windshield. All types of information and symbols can be displayed on the HUD combiner glass, but you can still clearly see the real world ahead through the windshield.
I have no idea how this is possible, but the information on the HUD is focused at infinity. Think about that for a moment.
Here is a display of flight guidance located inches in front of you, but you can look through the glass and clearly read the information on the HUD while still maintaining focus on the runway that may be miles ahead.
The beauty of a HUD for a fighter pilot is that he can see aircraft performance information such as attitude, altitude, airspeed, and such - plus weapons targeting information - while never shifting eye focus away from the enemy aircraft.
In civilian flying we have no other airplanes trying to shoot us down, but we do have the very real threat of flying into terrain while maneuvering near the ground on approach or shortly after departure. A HUD shows you all necessary data to fly the airplane along the desired path with eyes up and out of the cockpit.
The first HUDs in civilian airplanes were actually duplicates of the cockpit instruments projected onto the HUD glass. You could look through the HUD and still see attitude and airspeed, and your track along the approach guidance, while looking for the runway ahead. It worked great.
The Rockwell Collins system was so good it was approved for Category III instrument approaches, meaning visibility could be as low as 700 feet. Many years ago I landed a Boeing 727 using only information on the HUD because the windshield ahead was covered.
The HUD that Rockwell Collins builds is more accurately called a heads-up guidance system (HGS) because the information projected onto the HUD glass is much more precise than conventional attitude and instrument approach guidance.
The HGS uses inertial and GPS data to determine actual flight path. Flight path is where the airplane is going at the moment, as opposed to attitude indication showing merely where it is pointed.
Because of the precision of the HGS the guidance of the commands on the glass are expanded compared to normal cockpit instruments. As a pilot you find yourself making almost continuous small corrections to keep the flight path within a couple feet of perfect. Tiny deviations that nobody could see or correct for on normal flight instruments are instantly apparent on the HGS.
Several years ago Gulfstream pioneered enhanced vision system (EVS) that uses an infrared camera to peer through darkness and visibility obscuration to show the runway and terrain ahead. The EVS picture is projected onto the HUD so when you are flying you see both the guidance commands and the infrared image of terrain, lights on the ground, other aircraft, and even large animals such as deer.
The EVS on the HUD is so effective that Gulfstream pilots can continue the approach down to 100 feet above the runway instead of the normal 200 feet based on the EVS view of the runway. I have had the chance to land a Gulfstream with the windshield on the left side covered and looking only at the EVS/HUD display. May have been some of my best landings.
Now Rockwell Collins is working to combine computer-generated synthetic vision system images (SVS) of terrain on the HUD along with EVS and the necessary flight guidance. That way you can see a more complete synthetic view of the terrain far from the airport, see an EVS view in close, and always see data you need to fly the airplane.
Rockwell Collins, which is the presenting sponsor for the daily air show here, has a HUD simulator in its display near exhibit Hangar C. Stop by and try flying an approach using the HUD, and I know you will be as impressed as I am.
It's darn close to magic.