Ian Sheppard/LONDON

American Airlines has selected GEC-Marconi Avionics to supply its HUD 2022 head-up-display (HUDs) system for 75 new Boeing 737-800s the carrier has on order.

The contract secures the UK company's place as a leading supplier of civil HUD systems for the Next Generation 737 family alongside Flight Dynamics, which had threatened to dominate the market with its head-up guidance system following major orders from Delta Air Lines and SAS.

At one stage it looked as though Flight Dynamics had secured the deal. American's concerns over GEC's ability to certificate its HUD on the 737-800 before the airline receives its first aircraft in January 1999 were finally overcome, however, by last-minute changes to the UK company's proposals (Flight International, 14-20 January). Several hundred more systems are expected to be ordered by American.

GEC principal systems engineer Paul Wisely believes that its new HUD design is less bulky, easier to install and more "future-proof" than those of its rivals, as it is the first to use all-digital electronics and a novel "synthetic" hologram. He claims that, although existing HUD systems enable aircraft to land in Category IIIa conditions at Cat I-equipped airfields, the 2022 will also be ready to "plug in" to automatic-landing systems under development, creating a "hybrid Cat IIIb" capability.

Current systems use analogue electronics driving holographic technology, which relies on a combiner glass with a bandwidth which GEC considered too narrow for civil use. The synthetic hologram, or "rugate", uses a curved meniscus reflector allowing the image to be viewed from a greater range of angles, and to fade away at oblique angles rather than simply disappearing - "-the refractive index varies sinusoidally with depth".

At only 0.227kg, this combiner is also relatively light. "It does not need a heavy lump of glass in front of the pilot's eyes," says Wisely. Instead the material is a metal oxide dielectric, "harder than glass" and better seals the reflective layer, which is prone to decay in moisture.

The overhead projector is also "slimline" because of its Gulfstream V heritage and the fact that, being fully digitally driven, the circuitry is all built into the combiner unit. "The advantage of the new Boeings is that they have a duplex EFIS [electronic flight- instrument system] computer which can directly drive the symbol generator in the overhead unit - the HUD picks the mode straight off the EFIS," says Wisely, who adds that the user "-can overlay any type of imagery" on the new display, "including future perspectives [e.g, three-dimensional]".

Another advantage of the all-digital design is the "far lighter wiring looms", allowing Honeywell's display-guidance computer to "be fitted anywhere", allowing for simpler retrofits.

Although GEC expects retrofit sales, the goal had always been certification on new-build aircraft, particularly the new 737 variants.

Source: Flight International