Paris, France-Except for the Concorde, one could
argue that the last big change in the airliner business was in 1969 when the
Boeing 747 entered service. There have been successive, but minor, improvements
since to engines, aerodynamics, capacity, and performance but evolution has
generally been the rule in airliner technology for thirty years. Now, there is
the promise of a step function in capacity with the introduction of the Airbus
Industrie A3XXa double deck design that could lead to aircraft with a thousand
At the Air Show here in June, Airbus Industrie revealed further details of
its A3XX design, claimed to be the world's first twin aisle, twin deck aircraft.
With 40% more space available than on today's largest aircraft, a high level of
passenger comfort can be offered. The cargo deck is also full height, permitting
it to be used for passenger utilities such as toilets, if required.
Concept layouts show a spacious entrance area with wide staircases leading to
the upper cabin, reminiscent of those on a cruise liner. These allow distinct
passenger flows and Airbus claims that turn round times on an A3XX would be
similar to that on a Boeing 747.
(A3XX-100 with Rolls Royce Trent 900 engine)
This comparison is typical of the overall approach to design of the new
airplane. The B-747-400 now provides the airline industry with a benchmark
against which performance of similar large machines is measured. According to
Vincent Cassigneul, responsible for A3XX at Aerospatial Matra, "Airbus aims to
reduce direct operating costs (DOC) to at least 15% below those of the B-747-400
by a combination of improved techniques and the productivity gains of increased
capacity and range".
The first version, A3XX-100, will have a capacity of 555 passengers with a
range of 14,200 km (7,650 nautical miles). With this range any destination in
the world, apart from Australia, could be reached from London or Paris. Tokyo
would be within reach of every airport except those in South America or Southern
Africa. A series 200 would have the same range but with 656 seats or 950 seats
in a full economy configuration. Extended range aircraft would offer an extra
2,000 km. Combi and freight versions may also be built.
During 1998, Airbus Industrie and airline specialists in a wide range of
disciplines met to ensure the aircraft would meet the requirements of operators
as regards maintenance, systems, cabin design, ground handling, cockpit design
and engines. "The essential configuration elements were frozen in January 1999,"
"It is Airbus Industrie's intention for 40% of the value of the program to be
taken by risk-sharing partners," explains David Velupillai of Airbus Industries.
Agreements have already been signed with nine subcontractors, mainly involved in
airframe manufacture, with others due to follow.
Design features. Rolls Royce made an early commitment to develop the Trent
900 engine for the aircraft. Specifications include a swept fan, second
generation aerodynamics in the low-pressure and high-pressure compressors, and a
counter-rotating HP spool. Later an agreement was made with the Engine Alliance
(a joint venture formed by GE Aircraft Engines and Pratt & Whitney) to
develop the GP7200 engine for the A3XX. As a four-engined design, each engine
will have less thrust than those of current two-engine designs and will be some
Wind tunnel tests have been performed as part of a comprehensive wake vortex
study and to measure aerodynamic drag. A free flying 1:35 scale model has been
used to measure far-field dynamics of the vortices. The aim is to ensure that
take off and landing separation between aircraft shall be no worse than that
currently in place for the B747-400.
Drag coefficients may be improved by the use of riblets, embodied in a
plastic coating on flying surfaces. These have been tested in airline service on
A340 aircraft with promising results.
The Constant Speed Drive (CSD) has been a feature of commercial aircraft
electrical systems for decades, delivering constant frequency from a variable
speed engine. It is complex and expensive equipment. A simpler, variable
frequency power system is used on military and smaller aircraft. Airbus is
studying the compatibility of such a system with existing electrical loads on
the aircraft. Variable frequency generators are smaller and deliver greater
output at lower temperatures.
The A3XX landing gear has been configured in the simplest possible way. Oleo
length has been reduced with a consequent saving of 1.8 tons of weight. By
integrating the undercarriage into the aircraft structure, sufficient cargo
space has been created to carry two standard LD3 containers.
Compatible systems. From a ground operations point of view, the A3XX will be
accommodated within the infrastructure of modern international airports. The
airframe will fit within a virtual 80m square "box" defined by the International
Civil Aviation Organization (ICAO) and Airports Council International
recommendations. It will be able to maneuver on existing runways and taxiways
and be serviced by present-day ground support equipment.
Flight operations will also be simplified with great attention paid to the
findings from the Human Machine Interface workshops. These events have been run
to gain input from airline pilots. Larger display screens are among the new
features planned for the cockpit. There will be tail fin- and belly-mounted
cameras to assist in taxiing, enhanced airport navigation aids, and better rest
facilities for the crew.
The flight deck layout will continue the philosophy of commonality with other
Airbus aircraft. This assists Cross Crew Qualification and minimizes type
conversion times, particularly relevant for airlines flying mixed fleets. The
tradition of fly-by-wire will be continued.
Discussions with national air certification agencies have covered safety and
in particular emergency evacuation. Airbus believes standard evacuation times
can be achieved with the 16 exits that are available (four each side for each
deck). "With sufficient independent escape chutes that do not interfere with
each other on deployment or in use, the target times can be met," says
A3XX sales activity will commence at the end of 1999 to gain customer
commitments during the following 12 months. Engineering definition of the
aircraft will be finalized at the end of 2001. The first flight is targeted for
2003 with the aircraft entering airline service the following year.
Airbus Industrie is owned by four leading European aerospace companies
DaimlerChrysler Aerospace of Germany with 42.1% (after acquiring Spain's CASA
along with its share), Aerospatiale of France with a 37.9% share, and British
Aerospace with 20%. The partners have dual roles as shareholders and industrial
participants: carrying out the design and manufacture of the aircraft under the
co-ordination and management of Airbus Industrie. Here are some of the partners'
COMPUTER AIDED DESIGN
The Airbus partners have integrated project teams (design, production,
purchasing, and support) in their aircraft programs including the A3XX. The
development program is underway using the Airbus Concurrent Engineering (ACE)
process, which has been used to great effect on the A340 series. It uses
three-dimensional rendering of the aircraft to verify structures, systems, and
equipment. This is believed to be the first large scale industrial application
of a shared CADD S.5 CAD/CAM method. The CAD PDM system is supplied by
Parametric Technology Corp. together with dVISE visualization software from
Division Ltd. Engineers can simulate the passenger cabin and crew environment,
ground handling, and maintenance techniques. Instead of the time and cost of
building a physical mock up of the aircraft, an electronic version can be seen
and manipulated on a computer screen. Integration of CAD and visualization
ensures that design changes are immediately reflected in the simulation. "Our
key users will be able to visualize and interact with a virtual mock up as it
develops under the PDM," explains Steve Tothill of British Aerospace. "We can
conduct daily project design reviews and verify that the products are right."
"The commonality of the CAD/CAM system with the earlier aircraft designs will
enable accelerated design of the A3XX," explains Jean-Claude Bernodat of
Aerospatiale Matra. Electronic networking of all participants in the project18
companies in different countries also radically improves efficiency of the
Airbus has been using composites on the stabilizers of its aircraft for some
time. The A340-500 and -600 will go a step further than this by using composites
on the rear pressure bulkhead and keel beam. This part is 16m long, weighs 1.6
tons, and is the first use of carbon fibre in such a major structural element of
an airframe. The A3XX will utilize these developments and add to them. Most
probably the outer wing will be made in carbon fiber which will achieve a 20%
savings in weight.
Investigation of new materials for structures is underway, and Airbus
Industrie partners are heavily involved in the development of new processes that
will provide a stronger, lighter weight airframe. GKN Westland, for example,
produces large composite structures like under-carriage fairings and control
surfaces in composite. "We can also offer resin transfer molding (RTM) which may
be suitable for A3XX," explains Tony Roden. "This has previously been labor
intensive but cost improvement has been made with machines that can knit a shape
together from CAD software while resin is being impregnated into the form."
"Primary carbon fiber has been robust in service," says David Velupillai of
Airbus, "But different formats of sandwich construction have been tried to
optimize performance." Detailed examination is being made of glass laminated
reinforced epoxy (GLARE) and carbon fiber reinforced plastics (CFRP). In
evaluating new materials, Airbus is not only concerned with cost and weight but
availability, how readily they can be introduced in the manufacturing process,
how safely they mix with other materials, and their maintainability through the
aircraft's life. Daimler-Chrysler Aerospace has already started development work
on wing and fuselage components made from CFRP.
"The avionics will constitute a major system to be integrated by Airbus with
a central computer rather than separate processors," thinks Kenneth Estelle of
Smiths Industries which is working with Sextant Avionique on a flight management
system (FMS). Airbus is still soliciting various approaches to technology but
inclines towards an Ethernet architecture that can offer data transfer rates of
100 Mbytes/sec, many times higher than present systems. The concept is called
Avionics Full Duplex Switched (AFDX) Ethernet and will use slightly different
protocols from commercial Ethernet. The processor is likely to be commercially
available unit, not a special design.
The "interactive cockpit" is pushing avionics technology to new limits.
"Today level 1 security for commercial aircraft is 1 in 10-9 but this
level is likely to be higher in the A3XX," says Estelle.
The FMS will be one area where accuracy contributes to better DOC. It allows
an aircraft to take advantage of routes equipped with air traffic management
facilities. Flying a more accurate course can make a difference of some percent
to fuel used, for example.
Commercial aircraft hydraulic systems have been standardized on 3,000 psi
(207 bar) since the DC4 Skymaster in 1942. Most high-performance military
aircraft have 4,000 psi (276 bar) and this was the pressure selected for
Concorde. A few military aircraft such as the French Rafale have moved to a
5,000 psi (345 bar) system and the same is being considered for the A3XX.
Increased pressure means a smaller system: narrower gauge conduit, smaller
actuators, and less fluid volume so smaller reservoirs. Overall there could be a
weight saving, of 1.5 tons.
Yet if conventional axial piston pumps are used these would have to be bigger
and better, according to Wolfgang Jung of Parker Aerospace, division of Parker
Hannifin Corp. Depending on system design, there may be 4 or 8 pumps, electric
or engine driven.
Further tests will be necessary to determine whether Skydrol®the standard,
fire-resistant hydraulic fluid used today-will work in a higher-pressure system.
Electro-hydraulic actuator (EHA) technology is being studied. EHA would
provide an autonomous emergency back up instead of tripling the conventional
hydraulic system. It would save some weight by reducing the level of redundancy
in the existing system a development not favored by all.
The basic A3XX will have a maximum take off weight of (MTOW) of 540 tons.
Consideration of the effects on pavement is being validated by a series of tests
to measure real loads exerted by four- and six-wheel bogies. Another element of
this research is to test different pavement structures to destruction by fatigue
through simulated heavy aircraft use. In each test area strain gauges that
measure cumulative stress are installed.
Airbus has initiated its own Pavement Experimental Program but, in addition,
other agencies are also interested. The recent ceremonial opening of the
National Airport Pavement Test Facility (NAPTF) in New Jersey, U.S., marked the
start of a new era in airport pavement design. This is predicated on the
expectation of large capacity aircraft such as A3XX-entering service early in
the 21st century.
Airbus is studying the feasibility of boarding and deplaning passengers
direct to the upper deck. This would speed up turn around but would require new
types of airport passenger piers.