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HEAD-UP GUIDANCE SYSTEM FOR LUFTHANSA CITYLINE

Lufthansa CityLine is the third airline worldwide and the first in Europe to equip its fleet of Canadair Jets with a new precision approach system. Head-up guidance is the new magic formula which is to allow Lufthansa's regional daughter flight operations even under the most adverse weather conditions.

Bad weather approaches according to category IIIa with a decision height of 15 meters and a runway visual range of 200 meters are not new in the large-airliner business. However, what fits easily into the autoland and autothrottle system of a 747 or A340 airliner, is much too spacious, too heavy, and too expensive for a 50-seat regional jet ñ in short: not economical. Furthermore, the Canadair Jet´s General Electric engines are not suited by manufacture for the option of a fully automatic throttle control (autothrottle), such excluding the above mentioned design option of the large airliners. Due to this fact, the new head-up guidance system (HUGS), which CityLine plans to have integrated in all of its regional jets by the end of the year, seems to be the more practicable solution for small airliners.

After the two US carriers Alaska Airlines and Horizon Airlines, Lufthansa CityLine is the first airline in Europe to integrate the new system which is made by the electronics designers of Flight Dynamics.

Instead of a fully automated approach, the head-up guidance system allows the pilot to fly a manual instrument approach in CAT III conditions. This is possible due to the system's degree of precision. Furthermore, when flying with head-up guidance, the pilot does not look at the primary flight display on the instrument panel, but looks through a holographic window at eye-level. The virtual picture of all relevant flight data overlays the reality of the environment. The pilot's eyes focus in infinity, allowing the pilot to follow the system commands while simultaneously monitoring the outside and, in the final phase of the approach, the runway and airport environment. This omits the necessity for the pilot to switch from instrument flying to visual flying at the decision height. "The entire approach is flown with one head/eye position", says CityLine´s safety pilot, Arno Reichert.

The system's six-times higher precision, as compared to conventional flight director systems, is achieved through a second computation. While normally the data received from the instrument landing system (ILS) are used for flight guidance, the head-up guidance system computes its own guidance through inertial navigation, compares the two sets of data, and generates an continuously optimized flight profile. The additional input of runway elevation and approach path angle assures the continuation of the approach with high precision even beyond the loss of ILS signal strength close to the ground.

This process of computation is the main difference of HUGS to a conventional head-up display (HUD). HUDs only repeat the data presented on the cockpit displays and are not CAT III capable. Only the higher sensitivity of the head-up guidance system gives the capability that is needed for official CAT III certification.

For CityLine training captain, Raimund Neuhold, the new head-up guidance system's real achievement is the regained role of the pilot: "Due to HUGS the pilot is moved from his solely controlling position, as a manager of a fully automated process, a little more back into the center of the action. The cockpit crew, again, becomes what it should be: An integral part of the loop in the aircraft."

From page30 of FLUG REVUE 10/96