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Thursday, June 1, 2000

Avionics for a Colossus

What will be in the cockpit of the giant A3XX? Actually, it will appear little different from the systems in other, smaller Airbus models–but with a new twist or two.

Ian Parker

Cockpit commonality has been the cornerstone for cockpit design in Airbus aircraft, and the gargantuan A3XX will be no exception. This, despite the fact that the European manufacturer plans to implement new avionics technology in the 500+ passenger jet. In fact, in many ways the advanced avionics makes the commonality possible, particularly from the handling and display points of view.

Apart from the earliest Airbus aircraft–the A300 and A310–all other models have common cockpits, making conversion training easy. For example, conversion from the A320 to the A340 takes nine days instead of up to 25 days for conversion to a dissimilar type. Conversion from the A340 to the A330 takes just one day. The A319, 320 and 321 can all be flown with a single type rating. Airbus Industrie plans to make conversion from the A340 to the A3XX similar to that from the A320 to the A340.

This approach allows mixed fleet flying where pilots fly more than one type regularly. For example, over a number of days a Cathay Pacific pilot might fly an A340 from Paris to Hong Kong, then fly an A330 around the region, and then an A340 back to Paris.

"Having similar cockpits is a powerful advantage," Airbus tells Avionics Magazine. "The pilots get more variety of flying. It helps them keep up their number of landings," the manufacturer adds, referring to the most critical–but for some long-haul pilots, the least practiced–phase of flight.

To assure cockpit commonality, Airbus likely will select the major components for the A3XX, leaving such items as radios and navigation to the customer’s choice. As yet, however, the manufacturer’s equipment selection has not been made.

The Vertical Cut

Regardless, Airbus will not allow the quest for cockpit commonality to stifle its flight deck developments. For example, vertical navigation (Airbus calls it "vertical cut") information will be included on the bottom of the A3XX’s vertically elongated liquid crystal displays (LCDs). This allows the crew to evaluate their vertical situation, as well as their horizontal position. A line running left to right shows the aircraft’s projected path relative to safety altitudes and terrain. It can contribute to safety by helping predict, and therefore avoid, a controlled flight into terrain (CFIT) accident.

To provide the vertical cut, an extensive, accurate worldwide terrain database will be continuously combined with the aircraft’s position. The crew will be constantly aware of the terrain ahead, out to about 19 miles (30 km). Aeronautical chart information will be included, so zone infringements can be avoided.

En route terrain clearance will be available at all times, a useful feature during, say, an emergency descent following pressurization loss. Today, crewmen must consult en-route charts.

More typically, the vertical cut will allow the crew to better plan their vertical navigation. For example, an air traffic control (ATC) clearance will often specify crossing a reporting point at or above of, not below, a level or altitude. The vertical cut display enables the pilot to more easily manage the climb or descent to meet the clearance.

Three-dimensional imagery of local terrain may become displayable over the next few years. Airbus says its LCDs will be capable of displaying such imagery, but this will be incorporated only if it proves to be easier for the pilot to interpret.

Eight identical LCD screens will grace the A3XX cockpit panel, and pilots will use a qwerty keyboard and pointing device to interact with the aircraft, including with the flight management system (FMS), rather than today’s ABC keyboard.

Airbus plans to substitute printed checklists for ones available on screen. During abnormal and emergency operations, entire procedures will be shown on the screens along with aircraft status information.

The functions of the multipurpose control and display units and the two data communication display units on current Airbus types will be integrated into the A3XX’s main screens. The primary flight and navigation displays will remain largely unchanged to minimize conversion training needs.

Move Cursor, Change Waypoint

Changes to a flight plan can be made much more readily. The pilot can use the mouse to put the cursor over a waypoint on the navigation display. He or she can then cancel the waypoint, then move the cursor to select another waypoint. The name, code or coordinates of the new waypoint are not required. Even if the new waypoint is a random location, the computer is still able to define and accept it. Arrival times, tracks, speeds and altitudes are updated simultaneously. This interactive control of flight management functions is designated by Airbus as FMS Second Generation.

Since Airbus aircraft have side sticks and not conventional yokes, tables can be positioned before each pilot, providing room for an integrated keyboard. Each table will have a pointing device (mouse) for screen selection and operation within that screen. Airbus has yet to choose the pointing device’s configuration, but its officials assure it will be user-friendly and pilot-intuitive.

Airbus says it does not plan to fit the A3XX with head-up displays (HUDS), explaining that "HUDs don’t add much to our airliners." Virtually all operations are to ILS-equipped airports, and the A3XX will be certificated for Cat IIIB approaches, so adding HUDS is of limited benefit, Airbus claims.

The pilot computer terminals can be used for communication with other terminals and printers on the aircraft or the airline’s ground facilities.

Because of the A3XX’s large size, Airbus also has addressed the challenge of maneuvering the aircraft on the ground. It will install suitably pointed external cameras, which will present video images on the cockpit LCDs. To further combat the growing problem of runway incursion, particularly at night, the A3XX will also present an airport map on a screen.

Engine thrust will be displayed directly, not derived from N1 (low-pressure spool speed) or EPR (engine pressure ratio) as it is on current types. N1 and EPR are affected by ambient conditions and do not give a precise indication of thrust, Airbus officials assert.

The A3XX engines will have full authority digital electronic control (FADEC), with automatic start and automatic abort sequences. Two engines can be started at once. The power levers have detents, so they are easy to set at TOGA (takeoff/go around), climb and other power settings. TOGA will be 100% power, or less if conditions permit. A readout at the top of the engine display will confirm the selected power.

Monitoring Takeoffs

A study currently is under way on monitoring takeoff performance automatically. For example, if engine acceleration appears to be less than expected, the system will flag this situation early, so a rejected takeoff can be made as soon as possible. This feature also should reduce the number of unnecessary rejected takeoffs (RTOs)–when the pilot thinks a problem warrants an RTO, but it really does not.

Airbus is mindful not to overload the crew with information during the takeoff roll, so the monitoring system will not provide a continuous evaluation of takeoff performance. It will take a "snapshot" of the situation at, say, 80 knots with a V1 (decision speed) of about 130 knots. The system will remain silent if acceleration is okay. If not, the pilot receives a caution well below V1, allowing a much less time-stressed decision to be made.

Cockpit comfort will be paramount for the A3XX. Its mid-level position (rather than on top as in the Boeing 747) will keep airflow noise levels low and the pilot’s view for taxiing optimum. Airbus employed Aerospatiale Matra’s Epopee simulator for definition of the human-machine interface (HMI). The company has used simulators since the 1970s on developments such as the A310/A300-600 electronic flight instrument system (EFIS) and the A320 fly-by-wire control system.

Last year, 21 pilots from 10 major carriers "flew" the simulator, to provide Airbus with their input on how best to develop the cockpit. A3XX cockpit HMI manager Christine Luneau wanted airline pilots to evaluate "a new type of dialogue" with the aircraft. She claims the pilots’ feedback has been positive.

Airbus is keeping the "dark-cockpit/push-button" philosophy in the A3XX–lights illuminated only when things need attention. Fly-by-wire flight and thrust controls also will be retained.

Cost and Availability

Production deliveries of the 555-seat Airbus A3XX-100 could start in late 2005 if airlines express sufficient support by this summer for the manufacturer’s supervisory board to commit to a launch. A freighter variant (the -100F) will be launched at the same time for service entry by 2007.

The A3XX-100 is priced at around $230 million. The go-ahead is expected this year, spawning a family of aircraft (initially including the 656-seat -200 and the 480-seat -50).

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