In the chain of aviation development, light aircraft are frequently the last link. We got glass-cockpits, FADECs, and composite airframes, but years after these technologies have been introduced in military or airline aircraft.

I can see a single advantage in this delay: it makes guessing the future much easier. So what do airliners and military jets have that light aircraft don’t have yet ? I can think of three things: electrical controls (fly-by-wire), auto-throttle, and head-up display.

Fly-by-wire is hardly applicable to light aircraft as they don’t have hydraulically controlled control surfaces. FADECs are probably the first step towards auto-throttle, but today’s topic is head-up displays, or HUDs.

The HUD principle is rather easy to understand: it displays flight related information on a transparent support in front of pilot’s eyes. A HUD could technically also display non-flight-related information, but this is of less interest…

This technique has been used for years in military aircraft, displaying artificial horizon, but also other aircraft, and some parameters. With this kind of “enhanced vision”, the pilot doesn’t has to permanently look in and out of the cockpit.

HUD is also available as an option on most modern airliners. They are normally flown by a crew of two. On short final, the “flying pilot” flies with reference to the instruments, and the non-flying pilot looks outside, and informs his colleague when the runway is in sight.

The transition from instrument flying to visual flying is one of the most critical phases of flight. Using a HUD makes the change easier. This would reveal particularly helpful for single pilot operation, where the pilot must fly the instruments AND look outside for runway visual contact.

Electronic flight data information (glass-cockpit) is obviously a pre-requisite to any HUD implementation. We now have that with the AHRS included in the glass-cockpit systems now available for light aircraft. The next step is kind of a projection system, and obviously certification.

I can imagine the G1000 PFD projected – in a single color – right in front of my eyes while flying and ILS down close to the minimums… looks good. I don’t know if Garmin, Avidyne or L-3 have plans in that direction… but I hope so. And if you read and want the idea…

When Googleing “HUD for light aircraft”, I found a US patent for the concept of a system using LEDs on the propeller blades as support for a HUD. The concept sounds interesting, but it would mean that any engine failure also leads to a HUD failure…

If you’re ready to bet on when HUDs will become available for light aircraft – or if you know any product already available today – let your opinion in a comment.

Update: Click here to read more and see an HUD in action.