Now the wraps have come off the A380, an intense flight-test schedule awaits the world's biggest airliner before certification next year
Airbus's unveiling of the A380 before 4,500 invited guests at a ceremony at the Jean-Luc Lagardère final assembly line in Toulouse this week is a necessary but potentially frustrating interruption for engineers and test pilots involved in the ongoing process to prepare the giant airliner for flight and service entry.
By the time the first flight-test A380 manufacturer's serial number (MSN) 001 is ready to fly, it will be almost 10 months since structural assembly of the aircraft began on the Toulouse production line in May last year - assuming it takes to the air as scheduled by the end of March. The ensuing time has been taken up by completion, fitting out and verification of the flight-test instrumentation (Flight International, 23-29 November 2004).
Registered F-WWOW, MSN001 is one of four A380s that will be dedicated to the 13-month flight-test and certification programme for the initial Rolls-Royce Trent 900-powered version, the others being MSN002, MSN004 and MSN007. As reported, Airbus has had to complete a series of tests and procedures involving MSN001, MSN002 and the static test airframe "ES" (located adjacent to the A380 line) to clear the aircraft for first flight.
The first two A380s (MSN001 and MSN004) will bear the brunt of the flight-test programme and will be heavily instrumented. They are fitted with 20t (44,100lb) of flight-test instrumentation, plumbed with 335km (210 miles) of electrical cables carrying 70kVA of electricity. The equipment can take 6,000 measurements and monitor 150,000 parameters. Other special equipment includes a trailing cone (for air data gathering) and water ballast system (to simulate payload weights and positions), and a tail bumper with damping actuator. There are also load benches to simulate electrical loads. An escape system will enable the crew to exit the aircraft via a jettisonable cargo door, and parachute to safety. This will be available during initial test flights and early stall trials.
For testing, the flightdeck has a test-flight engineer station from where the aircraft's configuration will be managed throughout every flight. There are three flight-test engineer stations in the cabin - two on the main deck and one on the upper. These stations will be occupied by specialist engineers who will be responsible for flight preparation, evaluation and validation of the specific system or function under test, and the design follow-up.
The bulk of the data analysis and processing will be conducted by engineers monitoring telemetry from the ground at the A380 engineering site in Toulouse. Specialist engineers for the specific systems under test will monitor the flight and data in real time. Support engineers will be tasked with following up issues that arise from flight tests by interfacing with the design office and vendors.
Simulator development
In parallel with the preparations involving actual aircraft, the flight-test team has been working on the development of simulators at the A380 development site adjacent to Toulouse Blagnac airport. Dubbed "Aircraft Zero" when connected to the A380 iron bird, which is co-located on the same site, these simulators have been used to hone the A380's flight-control software to the point where it can be loaded on to the real aircraft for flight test.
"If the real aircraft behaves like the simulator does, then it would be ready to go into service now," jokes Airbus chief test pilot Jacques Rosay. "But it will not be like that when we test the computers on the real aircraft. We will have to adjust for reality."
Airbus revealed late last year that the first flight will be operated by a crew of six. Rosay will be at the controls for the take-off accompanied by senior vice-president flight operations Claude Lelaie. They will share the flying duties, with Rosay expected to handle the take-off, and Lelaie the landing.
Airbus flight-test director Fernando Alonso will occupy the test-flight engineer seat on the flightdeck, while Gerard Desbois, Manfred Birnfeld and Jacky Joye will man the flight-test engineering stations in the cabin.
With most of its outfitting completed, MSN001 left the hangar in early December to undertake outside tests - dubbed Station 18 in the build sequence. Here it has been undergoing a series of fuel and pressurisation tests, including the calibration of the fuel tanks, checking of expansion volumes, refuel rates, and measurement of the unpumpable, undrainable fuel to establish the maximum usable quantity. Surge fuel pressure tests and centre-of-gravity targeting are also being undertaken. Cabin pressurisation tests will comprise air leak and overpressure tests, and a check of the outflow valve/safety valve operation.
Paint job
MSN001's Station 18 phase was recently interrupted for it to be moved into the hangar and painted ahead of this week's "reveal" ceremony - and adorned with Airbus's new logo, which has been kept under wraps. Once these formalities are completed it will be back to Station 18 to complete tests in preparation for flight.
Airbus is conscious that the first flight is the most eagerly awaited European airliner debut since Concorde's almost 36 years ago, and has been at pains to limit media pressure by being unspecific on the timing of the first flight. When Concorde had its formal roll-out in Toulouse in December 1967, the manufacturer was confident that it would be airborne within a few months, but it was 15 months before the aircraft flew.
The official word from Airbus on the A380's first flight has always been "early 2005", with March seen as the realistic target. Rosay says only that the A380 will fly "when we are ready".
The next few weeks should see MSN001 undergoing the final checks and upgrades ahead of leaving the ground. Non-flight-rated items installed during the build process are being replaced, along with changes resulting from ground testing.
After final checks of radios, thrust reversers, oxygen system etc, the aircraft will be pass into the hands of the flight-test division, which will carry out engine runs, taxi and accelerator/stop tests.
Certification process
When the MSN001 does finally take to the air it will mark the start of a 2,100 flying hour test programme for the Trent 900-powered passenger version, which should culminate in certification 13 months later.
Lelaie says that, as with previous first flights of fly-by-wire (FBW) Airbus aircraft, the A380 will initially be operated with the FBW controls in direct law (which unlike "normal law" has no envelope-protection or trim bias for configuration changes). "Generally on the first flight we open up the flight envelope in direct law and fly up to 350kt [650km/h], then decelerate to progressively introduce normal law," he says. "We check it is reacting normally and then accelerate to maximum speed and repeat at high altitude before switching back to direct law for landing."
MSN001 and 004 will each contribute 600h to the flying programme, and their test schedules are broken into six and five phases respectively.
MSN001's first task will be the initial exploration of the flight envelope to confirm VD/MD (the design air speed/Mach number) to enable the A380's aerodynamic configuration to be frozen. Rosay says that these early evaluation flights will take around two months and will enable the test pilots "to get to know" the aircraft as they check out handling qualities. The first A380 will also be tasked with measurement of cruise performance and initial evaluation of systems, such as the autopilot and brakes.
"We will try to quickly identify issues and items requiring upgrade," says Rosay, who expects the flying rate to be high right from the start, as "everything is urgent". Other early trials include external noise identification tests and cockpit noise evaluation.
MSN001's second phase will see it undertaking initial development flights over a six-week period. Structural loads will be evaluated and structural dynamic responses identified during flutter testing. Handling qualities will also be explored, with the aircraft tasked with defining the FBW system's take-off rotation law. MSN001 will carry out the spectacular VMU minimum unstick speed tests at Istres military airbase in southern France, which involves the crew deliberately dragging the aircraft's rear fuselage along the runway with protection provided by an abrasive block. Braking performance will also be analysed and the anti-skid system developed.
Autopilot and autoland development flights will be flown, along with tests to prove the hydraulics, electrics, fuel and air conditioning systems.
The aircraft will then begin a three-month programme of initial certification work. This will include dry air tests; flights with artificial ice shapes on the wing to simulate icing (for both development and certification purposes) ; further development of handling qualities, radio navigation, autopilot and autoland systems; VMCA/VMCL/VMCG (minimum control speed) trials; establishing braking performance for certification and landing performance for the flight manual; and emergency electrical configuration.
Maximum energy
As phase three finishes, MSN001 will be around half-way through its programme and it will be tasked with another of the spectacular tests - the maximum energy acceleration/stop trial. Again, this will be carried out at Istres and involves an aborted take-off at maximum take-off weight and V1 - such trials have previously often ended with burst tyres and wheels on fire, and with the A380-800's 569t (1.25 million lb) maximum take-off weight making it by far the heaviest airliner ever certificated, clearance of this requirement will be a major milestone.
MSN001 should quickly move on to phase five, which involves the certification effort. At this point, natural icing tests will be conducted - if conditions had not been found to enable these to be completed earlier in the programme. Rosay says these tests will probably flown in northern Europe.
The aircraft will also carry out tests to certificate handling qualities and various systems, including autopilot/autoland and the radio navigation equipment.
The 600h to be flown by the other heavily instrumented A380 - MSN004 - will be compressed into 12 months, as it is due to fly a month after MSN001. The second aircraft will be more focused on testing performance and will be tasked with engine calibration at low and high speeds, as well as take-off and climb performance (for the flight manual) and stalls. It will also undertake development of the propulsion system, full-authority digital engine control (FADEC), auxiliary power unit (APU) and fuel system, as well as contributing to the development of the autopilot and autoland.
Hot and high
Midway through its test programme, MSN004 will begin to make its full contribution to the certification programme when it will be used to test brake and antiskid performance, as well as water ingestion tests on a flooded runway at Istres. It will also be used to evaluate acoustic fatigue, engine/APU fire detection and extinguishing, and will undertake the "hot and high" campaign. "This is usually at La Paz in Bolivia," says Rosay. MSN004 will later undergo the cold soak tests - these are usually in Canada or Siberia.
Rosay says that, as part of the evaluation of take-off and landing performance, "abuse cases" will be tested with the A380 being rotated at speeds below VR and approach and landings flown at speeds up to 5kt lower than the correct landing speed (VLS).
Around 10 weeks before type certification is due, MSN001 and MSN004 will begin their final phase, which covers additional certification, such as clearance of further autoland capabilities; an expansion of crosswind operations and 15kt tailwind performance; as well as approval of three engine-ferry flights. "We'll be taking crosswind operations up to something approaching 40kt," says Rosay, who adds that these tests are usually flown at Keflavik in Iceland, as it has two perpendicular runways.
A380 MSN002 - the third to join the programme - will contribute 500h to flight testing and will be the first of two equipped with a representative cabin seating around 510-520 passengers. The aircraft is undergoing ground vibration testing ahead of being repositioned to Hamburg Finkenwerder for the interior installation. These tests enable Airbus to identify frequency and damping responses of the real aircraft structure, and to validate models used for flutter clearance.
MSN002 will start flight testing seven months after the first flight of MSN001, and tests will concentrate on developing the cabin systems such as air distribution and temperature control, cargo compartment ventilation, lighting, public address, noise tests, water and waste, and in-flight entertainment (IFE) - in this case the Thales TopSeries I-5000 system. The aircraft will be equipped with heated passenger dummies to enable the cabin environment to be fully understood. It will also be used to evaluate the cabin under negative g conditions.
Around a month into its test programme, MSN002 will spend two weeks operating the so-called early long flight (ELF) programme, which will comprise four sectors with full passenger loads using staff volunteers. Airbus first adopted the ELF philosophy for the A340-600 programme.
"We'll operate four ELF flights, starting with a 4h sector and finishing with a maximum of 15h," says Rosay. "It enables us to see how the cabin behaves in real conditions and quickly identify any issues, and gives us time to incorporate changes during the test programme."
MSN002 will then spend two weeks undergoing external take-off and landing noise certification at the airbase in Moron near Seville, Spain. Wake vortex trials will also be flown.
The last four months of MSN002's test programme are to be spent on certification duties and final verification of systems. The aircraft will be used to test the cabin in various extreme weather conditions - cold soak as well as hot and humid - and to undergo electromagnetic interference tests. The aircraft will also visit some of the key airports where the A380 will soon be operating to demonstrate compatibility.
The fourth and final aircraft involved in the initial test programme is MSN007. It will join the programme around nine months after first flight and like MSN002 will focus on cabin development. Before it starts flying, it will be equipped with a special 853-seat interior to enable Airbus to complete the evacuation test and certificate the exit limit capacity for the aircraft.
Demonstration flights
MSN007 will incorporate cabin modifications that come out of MSN002's ELF programme, and will also operate customer demonstration flights. The aircraft is to be equipped with the alternative IFE system - Matsushita Avionics Systems' EX2.
Around six weeks before certification is due, MSN007 will be tasked with flying the A380 route-proving programme.
All being well, in little over a year from now, Airbus should be closing on certification of the world's largest airliner, enabling launch customer Singapore Airlines to put the aircraft into revenue service as scheduled in the second quarter of 2006. By then, Airbus will already be turning its attention to the next task - test and certification of the General Electric/Pratt & Whitney Engine Alliance GP7200-powered A380, due towards the end of next year.
MAX KINGSLEY-JONES / TOULOUSE
Source: Flight International
