Rockwell Collins' Flight Dynamics subsidiary is testing a prototype surface guidance system (SGS) aimed at increasing the safety and efficiency of taxi operations at night or during bad weather.

The system extends the use of cockpit head-up displays to include pilot guidance for high-speed exit and taxi operations, according to Flight Dynamics president John Desmond. The company is launching the new SGS here, and says it can have initial capability available in late 2002.

SGS is envisioned as a software upgrade to existing Flight Dynamics' head-up guidance systems (HGS). Smiths Industries and Jeppesen Sanderson are partners in the project.

The SGS symbology is similar to current HGS takeoff, approach, landing and rollout guidance, and transitions seamlessly as rollout speed slows or the aircraft taxis onto the active runway for takeoff. Flight Dynamics is working on an associated real-time moving-map taxi path graphic to be displayed on a head-down display for the other pilot.

Desmond acknowledges that full-up SGS capability is dependent on appropriate installation of emerging differential GPS (D-GPS), ADS-B and control-to-pilot datalink communications (CPDLC) technologies. However, the basic system still can significantly contribute to airline safety and efficiency and could be used with pre-determined or "canned" taxi routes. And the benefits derived from SGS will encourage airlines and airports to install DGPS, ADS-B and CPDLS, he said.

A simulator-based "test flight" of SGS technology by Show News indicates that the system is indeed intuitive and easy to use. The demonstration assumed availability of DGPS and CPDLC technologies. It also assumed the expedient receipt and flight crew confirmation of appropriate ATC clearances and their automatic entry in the aircraft's flight management computer.

The simulated taxi test began on short final to a busy major hub airport similar to Atlanta Hartsfield. Shortly after touchdown, the head-up display's rollout symbology segued into the SGS dataset to accommodate an upcoming high-speed turnoff. The SGS screen instantly showed a series of conformal "cones" and small triangles to mark the runway and taxiway edges and centerlines, making for an easy path to follow. A simplified adaptation of conventional HUD symbology at the bottom and center of the screen provide more precise guidance, essentially requiring the pilot to keep the tip of a vertical trend vector in a diamond-shaped guidance cue. There also is a football-shaped symbol that helps the pilot achieve the optimal speed for an exit or taxiway-and to avoid jostling his passengers. It varies according to turn sharpness and is set to produce a 0.1-g turn rate.

Other text and symbology appearing around the edges of the HUD screen include groundspeed, target taxi speed, distance to the end of the cleared hold, and next turn direction and distance. Two non-conformal symbols indicate main gear location on the taxiway.

As the aircraft decelerated, speed was set as advised by the "football" symbol. Once onto the exit, the symbology shifted to the system's low-speed taxi dataset, which is similar but less cluttered. After that it is simply a question of following the artificial taxi path, which leads automatically around the field.

The system gives pilots confidence to taxi at optimum speed and thereby keep airport operations moving smartly, Desmond says. Although the field and "aircraft" were unfamiliar, the Show News test pilot found he could do just that. Even when visibility was brought to almost zero by a simulated "pea soup" fog, it was possible to maintain a respectable speed. SGS sets no minimum taxi speed, Desmond said, as the pilot decides what feels most comfortable.

The end of taxi clearance is indicated by a series of solid cones across the HGS display screen and appropriate text messages. The cones disappeared once further clearance was received. If the pilot passes the hold line, or otherwise deviates from the assigned taxi path, the text "excessive deviation" appears as a warning.

By Paul Proctor