Peter Henley/TOULOUSE
Airbus Industrie has built up vast experience in the design and production of fly-by-wire commercial aircraft. A bedrock philosophy behind the consortium's ever-expanding family has been to achieve maximum commonality between cockpits. This means pilots can fly aircraft of the same family type - the single-aisle A319/A320/A321, for example - with a single type rating, while the transition training for changing between family types is minimal.
The A3XX follows this philosophy closely and Airbus estimates that pilots will require about the same - or less - time to transition to the A3XX from the A340 as is now required to convert to the A340 from the A320.
Much of the extensive research under way at Airbus' Toulouse facility has been dedicated to establishing the specification for the A3XX human/machine interface (HMI). A3XX cockpit simulation work has been carried out on Aerospatiale Matra's Epopée simulator, which has been used since the 1970s on developments such as the A310/A300-600 electronic flight instrumentation system (EFIS), A320 fly-by-wire flight control system and even the Hermes reusable spaceplane.
The fixed-base simulator fully represents the aircraft and its systems using four graphics workstations. It has been used for initial evaluation of the A3XX's HMI that is a fundamental component of the aircraft's design.
Between June and September, the simulator was "flown" by 21 pilots from 10 major international airlines, using operational scenarios followed by extensive discussion of their experiences. "We wanted to collect as much feedback as possible on our ideas," says A3XX cockpit HMI manager Christine Luneau. "The aim was to confirm that pilots will accept a new type of dialogue with the aircraft and to get all possible feedback on any modifications we should make to the human/machine interface. This aircraft will be in service for 50 years. We have to think very carefully about that."
The evaluation feedback has been positive, Luneau says: "All of the pilots supported and appreciated the new possibilities we are offering." To test this for Flight International, I "flew" the Airbus development simulator in Toulouse accompanied by Jacques Rosay, the engineering test pilot responsible for evaluating the HMI concept.
The baseline A3XX-100, planned for service entry in 2005, will be a nominal 556-seater with double-deck passenger cabins. Long-range, combi and freight versions are being considered simultaneously. A stretched 656-seat -200 is planned and a 480-seat shrink, the -50, has also been proposed.
The A3XX cockpit will follow closely the concept proven in earlier generations of fly-by-wire Airbuses. The sidesticks will be retained and the instrumentation will, at first glance, look much like those of earlier glass cockpits. Experienced Airbus pilots will immediately feel at home with it.
The system is built around eight large-format, fully reconfigurable display units (current Airbuses have six), a "pointing device" for each pilot on the pedestal and two keyboards for each to address onboard systems and interface with future developments such as free route air traffic control. One of the keyboards will be integrated with the table in front of the pilots - an innovation which Airbus says is possible only with sidestick control.
Displays remain the same
The functions of the multipurpose control and display units and the two data communication display units found on current Airbuses will be integrated into the main screens.
The primary flight and navigation displays will remain largely unchanged to minimise cross-crew qualification needs, and a deeper vertical format is used mainly to accommodate vertical flight information. Airbus says the aim is to have an intuitive pilot aircraft interface without compromising commonality with other Airbus types. This has meant the same design criteria being applied to the cockpit layout, system integration and automation, the "dark cockpit/push button" philosophy, and fly-by-wire flight and thrust controls. The same processes and crew discipline will apply for normal, abnormal and emergency procedures, and task sharing will be basically unchanged.
Airbus had a radical rethink of cockpit location. Because of the A3XX's double-deck configuration, one option was to mount the cockpit atop the nose, 747 style. But this carried significant penalties, says Robert Lafontane, vice-president for engineering and product development in Airbus' large aircraft division. "It was the worst position because of the noise and drag at high speeds, and the pilots' view of the ground would be limited."
Placing the cockpit low down would have interfered with cargo volume, says Lafontane.
The optimum position was therefore midway between the two, allowing a clean aerodynamic profile, reducing cockpit noise and giving the pilots a perspective little different from that in earlier Airbuses. Lafontane adds that pilots who have tested the location, which is accessed by four steps from the lower deck, say it is also far better for reaching the crew rest quarters, which will be designed into the area immediately behind the cockpit.
Extensive input for cockpit improvement has been gleaned from the 20 airlines that have contributed to the A3XX design, while improved flight safety has driven other considerations. Many suggestions are still being evaluated, but flight division vice-president Claude Lelaic says the final arbiter must be "added value" - not just introducing a different way of doing things because modern technology makes it possible.
New features being considered for the A3XX cockpit therefore fall into two categories - additional facilities and enhanced capability.
Taxiing camera
The broad heading of additional facilities includes a camera mounted beneath the aircraft to help with taxiing. At 79.8m long and a maximum of 79.5m wide (261ft) (in the -200 version), the aircraft is larger in both dimensions than a Boeing 747-400, but will have to use existing airport taxiways.
The camera image will be presented on one of the cockpit screens to help the pilot keep the main wheels on the taxiway - particularly when negotiating corners and intersections. The camera will not have an infrared capability to aid ground manoeuvring in fog because, says Lafontane, "it would cost a lot of money for a limited return". Three years' experience on an A340 test aircraft has shown that A3XX pilots will soon become used to the perspective from the cockpit and learn to allow for the bulk of their aircraft, he adds. The Boeing 777-300 has similar cameras, so it may be that operational experience shows them to be an asset.
A more obvious bonus is the ability to call up the ground plan of any airport on a display screen, with the image of the A3XX imposed upon it. As the aircraft moves, so the image reflects its progress. This will ease day and night taxiing on extensive and complex airports and will reduce the risk of inadvertently violating holding points. This function therefore seems to meet the value-added criterion.
Another likely enhancement is take-off acceleration monitoring. Here the challenge is to help the pilot's decision-making and not to confuse it, with the aim of reducing the number of unjustified rejected take-offs (RTOs). The decision to continue or reject a take-off is made against the decision speed (V1) for the conditions. The V1's validity, however, could be undermined by, say, a dragging wheel brake or reduced thrust from a faulty engine. V1 might then be reached further along the runway than the take-off calculations predicted. A decision at V1 to reject the take-off could result in the aircraft over-running the runway.
The idea is that the automated monitoring of take-off acceleration would give the pilot confidence that the A3XX was accelerating as expected. The last thing any pilot wants, though, is another parameter to absorb during take-off in addition to airspeed and engine power. In any case, information generated in real time and to be taken into account as the aircraft approached V1, would be unrealistic.
Airbus' thinking is for the monitoring computer to generate a warning at a "snapshot" point during take-off - say at (80kt) 150km/h against a V1 of about 130kt. If acceleration was normal, the monitoring would be silent; if acceleration is below par, an alert will caution the pilot comfortably before the aircraft reaches V1. As conceived, this would appear to be a significant value-added safety factor.
The flight safety value of Airbus' proposed vertical navigation display is obvious. This is a subsidiary display across the bottom of the lateral navigation display (ND) which Airbus describes as a "vertical cut". It portrays the aircraft's vertical flight profile directly above its projected track over the terrain.
Situational awareness
A basic vertical navigation (VN) display is an optional addition to the Honeywell Primus displays fitted to the latest business jets, such as the Bombardier Global Express or Gulfstream V. This display aids vertical situational awareness, particularly in climb or descent. If an ATC clearance specifies crossing a reporting or way point "at or above" or "not below" a specified level or altitude, the VN display enables the pilot to manage the climb or descent to meet the ATC clearance. The projected profile can be programmed, to be displayed as a projected flight path. The aircraft symbol can then be flown to the profile, and the traditional guesswork is eliminated from the task.
The Airbus proposal introduces a quantum leap, however. The "vertical cut" can display a terrain profile using extensive, accurate world-wide terrain databases, the "smart" ability of, for example, Honeywell's Enhanced Ground Proximity Warning System (EGPWS), aeronautical chart information on safety altitudes and powerful on-board computers. With a magenta line, it will show instantaneously en-route or local safety altitudes. Through this, the pilots are constantly aware of the terrain beneath their aircraft, and beneath its predicted track for, say, 30km (16nm) ahead. The en route safety altitudes used for computation are derived from charts and airport vicinity safety altitudes from approach plates. This makes it almost impossible to commit mistaken or illegal infringements of safety altitudes.
En route terrain clearance is available at all times and does not have to be found from an en-route chart during a rapid descent following a pressurisation failure or other emergency. The only minimum not protected is MVA (minimum vector altitude) because this information is published only for the benefit of ground radar controllers and is not in the "public domain". The MVA applies only to a specific sector and only to an aircraft that has been radar identified and is under the control of an area or terminal radar controller. There is no technical reason why MVA safety altitudes should not be included in the A3XX database, but the legal or regulational aspects of obtaining and using the data would have to be resolved first.
The avionics industry is on the threshold of offering technology that would allow three-dimensional "pictures" of local terrain to be generated and displayed. Airbus will consider this for use in the A3XX, although Lelaic says: "It might, however, be the case that the current diagrammatic form of the vertical cut proves to be easier for pilot interpretation than a 3-D display. If that were the case, we would keep the vertical cut." Lafontane adds: "The basic liquid crystal display could do it. Our cockpit is ready to incorporate it when the market is ready, but we don't think it will be around for the first flight date."
Airbus is evaluating several concepts under the broad heading of enhancements. The Airbus fly-by wire (FBW) family (A320 family and A330/A340) flightdeck already has a sophisticated EFIS, system monitoring - electronic centralised aircraft monitor (ECAM) - and a flight management system (FMS). In the A3XX, quick access to the primary cockpit function is being sought, along with a much broader databank of on-board information. Changes have been incorporated into the ECAMto reflect the increased complexity of the A3XX and eliminate the need for a paper checklist. During abnormal and emergency operations, the entire procedure will be shown on the screens, elaborating the aircraft status and providing notes on action lines. There will be enough space on the larger screens to display further information if needed.
During normal operations, the flightcrew will be presented with all normal checklists, along with routine actions, and will be able to review or revise abnormal and technical procedures and limitations, such as speedbrake limits for particular flight conditions.
Electronic documentation
The A3XXonboard information system will provide computerised access to onboard electronic documentation, allow for computation of flight preparation, weight, balance and performance, and enable access to the electronic logbook. Communication between the aircraft and the ATC environment and between the aircraft and the airline will become far more agile and comprehensive.
By using the pointing device (the final form of which is not finalised), the pilot can move a cursor between screens and manage the information presented on them. Appropriate menusare displayed and the specific display or information is selected via the pointing device and cursor.
This method of controlling displays and accessing information is much quicker than current press-button selections, and was convincingly demonstrated on Airbus' development mock-up. The pointing device and cursor were used to program an extensive change to the flight plan route. The navigation display (ND) showed the flight plan route via several waypoints. To schedule the change, the cursor was transferred to the ND and moved over the existing waypoint to cancel it, then to the new waypoint to select it. There was no need to feed in the name, code or co-ordinates of any way point. If it was a designated point, the computer recognised it; if it was a random point on the landscape, the computer was still able to define and accept it. The adjacent CDU showed "ACTIVE F PLN" as an electronic page listing waypoints, arrival times, tracks, speed and altitude, and was updated simultaneously. As long as a design is found eventually for the pointing device so that it is easy and quick to move with precision, the A3XX will enjoy considerable value-added benefit from this interactive control of FMS functions - designated by Airbus as FMS 2nd Generation.
The keyboards used for this interactive control allow ready access to on-board information such as minimum equipment lists (MEL), performance, weight and balance or chosen technical information for fault tracing. These pilot terminals can also be used for communication with other terminals and printers, either on board or at the airline's data-processing centre on the ground.
The last A3XX cockpit feature to be evaluated was the display of engine power parameters. Airbus says modern displays of engine N1 (rotational speed of the low-pressure compressor, expressed as rpm or percentage) or EPR (engine pressure ratio) do not adequately advise the pilot of how much power the engine is producing. The Airbus solution is to display thrust as a percentage - 100% for maximum available, 0% for a shut-down engine. The claimed advantages are that the display of thrust is more user-friendly and intuitively easier to interpret, remaining engine power is always shown, thrust is not as sensitive to ambient conditions as N1 and EPR, and thrust will mean the same thing whatever the engine type. These claims are persuasive, at least academically.
I put them to the test in the simulator, which uses software to represent the A3XX engine indications as defined by Airbus' ACUTE (Airbus Cockpit Universal Thrust Emulator) concept.
It has a "standard" Airbus fly-by-wire layout with sidesticks and EFIS displays, is fixed base, but has excellent visual capability.
Engine parameters
The cockpit centre display shows five parameters for each of the four engines. The least critical parameter, fuel flow, is shown digitally in kg/h at the foot of the display. Above this, N1 is portrayed digitally, and above that, EGT (exhaust gas temperature), in íC, is shown both digitally and by an analogue arc with limits in red. At the top of the display, the most critical parameter, thrust, is shown as a percentage digitally and by an analogue arc, again with its limits in red. The display is therefore in a format common to most modern glass cockpit aircraft. The difference is in the use of thrust as the primary parameter for engine health.
The A3XX engines will be equipped with full authority digital engine control and will have automatic start sequences with automatic abort should a malfunction occur. Engine starting is therefore initiated by a switch, after which the pilot's role is finished. Two engines can be started simultaneously.
For take-off, either 100% thrust or a reduced value can be used, as conditions permit. The Airbus power levers have clearly defined detents, so are easy to set to TOGA (take-off and go-around) or CLIMB, for instance. A legend at the top of the engine display panel reflects the thrust selected by the power lever position, for example TO 100%.
I found the ACUTE system worked well in practice. Firstly, the layout of the display is familiar - the only difference from other modern displays is that thrust is displayed as the primary engine parameter instead of N1 or EPR. Secondly, thrust is a precise means of expressing engine power, so situational awareness of power management is improved significantly. Expressed in non-aviation parlance, this means that the engine power being used, available if required, or remaining if an engine is ailing, is displayed accurately and in a measure (%) that is universally understood. The ACUTE concept depends entirely on the technical ability to measure engine thrust instantaneously and accurately. Airbus claims this is the case.
Flying the A3XX development simulator showed clearly the value added by the concepts that Airbus is investigating. Although the ideas are geared primarily to defining the cockpit for the A3XX, many of them will be applicable to other members of the Airbus family.
Source: Flight International
