By max Kingsley-Jones in Toulouse
While chaos rules on the A380 production line as Airbus battles to overcome the latest delays to hit the A380 programme, one department where a few smiles can be seen is flight test, as the giant is progressing relatively smoothly towards certification at the end of the year.
The engineers and pilots are quietly confident that the A380 will meet, and in many cases exceed, all its planned performance targets. However, the test schedule has slipped by several months and some major parts of the test programme remain to be undertaken, including the somewhat destructive maximum energy rejected take-off (RTO) demonstration and the route-proving programme. With the world – especially launch customer Singapore Airlines (SIA) – watching to see if Airbus can achieve its stated aim of delivering an A380 in 2006, there is no margin for further slips to the revised test schedule.
Five Rolls-Royce Trent 900-powered A380-800s have flown since the first flight of MSN001 on 27 April 2005. Three of these aircraft are in flight test, while a fourth test aircraft is having its cabin installed in Hamburg alongside the first customer aircraft for Singapore Airlines (MSN003), which is the most recent A380 to have flown. By the middle of June, the fleet had accumulated just over 1,400 flight hours and 430 flights, says Airbus senior vice-president flight operations Claude Lelaie.
Two more A380s are in Toulouse being prepared for flight – a second aircraft for SIA, which will be flown to Hamburg for cabin installation and painting, and the Engine Alliance GP7200-powered test machine (MSN009), which should have flown several months ago but is now due to take to the air by the end of July.
Airbus aims to complete the flight-test and certification programme for the R-R Trent-powered version by the end of December to enable the first aircraft to be delivered to SIA this year as scheduled. However, the manufacturer still has around 1,000h of flight-testing to complete (assuming the 2,500h announced at the start of the test programme is still the target), including 300h of route-proving. The test team also has to cope with the unscheduled (and ongoing) distraction of carrying out additional flights to verify the A380’s wake vortex characteristics amid a row over the International Civil Aviation Organisation’s separation distances recommendation.
Slower approach
The good news is that Lelaie reports the A380’s CLMAX (the amount of lift generated by the wing) is better than expected, which has enabled approach speed at maximum landing weight to be around 4kt (7km/h) lower than expected at 138kt. “Take-off performance is also on target,” says Lelaie. The final VMCG (minimum control speed on the ground) tests were completed successfully at the flight-test airfield at Istres in southern France on 14 June.
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| MSN004 attended the Dubai air show last year in Emirates livery |
The A380’s maximum design speed (VMD/MMD) of Mach 0.96 was successfully demonstrated in December last year and the aircraft has turned out more slippery that expected. This should enable it to cruise faster than the nominal Mach 0.85 originally specified, says Airbus senior vice-president flight test Fernando Alonso: “It is comfortable at M0.855-0.86.”
During tests, the A380 has been flown at take-off weights far exceeding the 569t maximum set for production aircraft, as Airbus looks to test at weights planned for the heavier A380-800 Freighter, which will weigh in at 600t. “We’ve taken off at 596.5t and made a landing almost straight after when we were only a few tonnes lighter,” says Alonso.
MSN004, the second of the two fully instrumented test aircraft that do not have full cabin furnishings, headed off to Medellin, Colombia, in January to assess the performance of the engines and auxiliary power unit in hot and high conditions, as well as the air conditioning, electrical and hydraulic systems. Take-offs were carried out at an altitude of 7,000ft (2,135m) and a temperature of ISA +15°C (59°F) and the power systems behaved satisfactorily without any failures, says Lelaie.
Ahead of the full cold-weather campaign, which will be undertaken with the fully furnished MSN002, a test was carried out in Iqaluit, Canada using MSN004 to check system readiness and collect data for structural justification. “Our target was a temperature between -25°C and -30°C to see how all the equipment was working, and we had -29°C,” says Lelaie. “Then with the fully equipped aircraft we will go to Irkutsk in [Russian] Siberia where our target is -50°C.” These initial tests were largely successful, although one engine suffered an oil pump failure.
In May, five flights were undertaken to assess the A380 wing’s anti-ice behaviour in natural icing, says Lelaie: “We were very lucky because sometimes you can wait for many weeks to find natural icing conditions, but the day we went to fly the tests we had the perfect weather required.”
Part of the tests involved “flying directly into thunderstorms and then turning inside”, says Lelaie. “You have the green, yellow and red on the weather radar display and the target is to turn on the yellow part, which is the better place to find ice.”
During these tests, the A380 was exposed to more than 100 lightning strikes without any problems. Although the tests went well, they did turn up a problem with the A380’s ice detection system, which Lelaie says is “not satisfactory and is to be worked on”.
However, he says the tests show the A380’s wing anti-ice system may well be unnecessary and could be eliminated on production aircraft. The final decision will be taken after verification with further testing using artificial ice shapes, which was due to be carried out on MSN001 in late June. “The removal would eliminate the weight of the hot-air ducting and reduce complexity,” says Lelaie.
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| The A380 test fleet has accumulated over 1,400 flying hours |
Initial noise tests were carried out on MSN001 last October in Morón, Spain to confirm that external noise level objectives could be achieved with the current aircraft configuration. What Lelaie describes as “real noise measurements” began at Tarbes in western France in mid-June with MSN002, which is the first fully representative A380 as it is equipped with a full set of production-standard engines.
Airbus has also carried out tests to assess the behaviour of systems during negative g manoeuvres “because that is something that may be found in extreme turbulence”, says Lelaie. “We achieve this by climbing at a high pitch attitude then pushing the stick forward,” he says, adding that during these tests a negative g value of up to 0.5 could be achieved.
These tests began in May, initially with MSN001, which was used to verify handling qualities and load clearance as well as to carry out a systems check. MSN004 was used for a test in what Airbus calls a “standard representative configuration”. Systems checked include electrics, fuel, hydraulics and propulsion, as well as engine loads.
Virtual flight
MSN002 returned from Hamburg in May after installation of its fully furnished 474-seat cabin, and will be used to undertake the early long-flight (ELF) test programme in September – around three months later than previously planned.
Before leaving Hamburg, MSN002 was used for a virtual first flight of the cabin. “Before we started real cabin tests we wanted to have a feeling for the performance of the cabin on the ground, so we carried out a virtual first flight on the ground with 474 passengers on board,” says Lelaie. “We were a bit anxious before the test because the A380 has such a big cabin and is such a new concept. We had a nice surprise as we had a good result.”
September’s ELF programme will comprise four flights lasting 7h, 10h, 12h and 15h – one of which will be a night flight to ensure all conditions are covered. “About 300 of the passengers will be Airbus staff, and the remainder will be other guests,” says Lelaie. “We’ll evaluate comfort, temperature, in-flight entertainment, etc.”
Lelaie says the ELF programme was invented for the A340-600 after Airbus had some issues with the cabin on the original A330/A340. “We decided to perform several flights full of Airbus passengers to check the systems,” he says. “This enabled us to make all the necessary corrections before starting route-proving.”
Route proving
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| MSN004 was tested in Canada at temperatures down to -29°C |
The second fully furnished A380 (MSN007), will undertake a route-proving programme towards the end of the year. This aircraft is in Hamburg having a three-class cabin fitted, having previously been equipped with a high-density configuration for March’s successful cabin evacuation test when all 873 passengers and crew evacuated in less than 80s – 10s faster than the target time of 90s. “We were surprised by the result because nobody could have bet that we would make it,” says Lelaie.
Some 300h of route proving is a regulatory requirement for type certification “to demonstrate the maturity of the aircraft in an airline environment”, Lelaie says. These flights will be operated over a period of around four weeks with co-operation from A380 customers Lufthansa and SIA. “We can perform the route-proving without anybody in the cabin, but we have asked both companies to have a sufficient number of flights with a full passenger load to check how the cabin is performing,” says Lelaie.
One potentially destructive test still awaiting the A380 is the maximum energy RTO demonstration, in which the aircraft is brought to a halt from what would be its maximum V1 speed at its maximum take-off weight of 569t, using only wheel brakes (which must be 90% worn). The landing gear suffered severe damage when this test was carried out on the A340-600, so Airbus is taking a more cautious approach with the A380 and will perform the demonstration in two steps, says Alonso.
“We don’t want to risk losing an aircraft from the programme in the middle of testing, so we’ll do a high-energy RTO in around a month or so to clear the aircraft to carry out the route-proving,” says Alonso. “Then we’ll carry out the full test at the highest maximum take-off weight at the end of the test programme.”
Source: Flight International
