FLUG REVUE December 2004: A380 nears first flight

A380 PREPARES FOR ITS ROLL-OUT

By Sebastian Steinke

It is full house at Station 30 in the A380 assembly hangar at Airbus's Toulouse site: with its nose by the gate, as if it were about to roll out at any moment, prototype MSN 001 stands parked, flanked by MSN 002 and MSN 004 in the dock. When FLUG REVUE visited at the end of October, the first flying prototype, still with its green primer coat, was in the process of having engines two and four fitted. Next to a set of brand-new tyres, the elongated fairings for the flap drive units were waiting to be assembled. On the giant A380, they are about as big as phone boxes. MSN 001 will spend about another four weeks here so that, in addition to two other Trent 970 engines, the auxiliary power unit in the stern, the air-conditioning system and the fold-out ram air turbine (RAT), which feeds the emergency power system, can be assembled.

After that, for safety reasons, the prototype will go outside and spend between four and six weeks at external Station 18, where the tank system (initially with helium) and then the pressure cabin will be tested for the first time. Following a short intermezzo in the flight operations hangar, where MSN 001 and MSN 004 are exceptionally being painted instead of in Hamburg, the premier jet will revert to Station 18 after the ceremonial roll-out of the A380 on 18 and 19 January adorned in the future house colours of Airbus.

The maiden flight will probably take place in the first half of February, but before then Airbus has planned in another spell on Station 22 so that the latest software updates and equipment changes which have come about during the assembly period can be installed for the first flight. Finally, to prepare for the maiden flight, the entire aircraft will move back to Station 17, where it will be handed over to the in-house test flight organisation. Now the radio equipment will be checked, and the reverse thrust and RAT will be deployed on a test basis. The oxygen system will also be checked. As soon as engines and APU are running on the stand, the taxi trials and brake tests can commence. From a low speed, the prototype will then accelerate at full tempo along the Toulouse runway to decision speed V1. One to two days after this phase, the prototype will be ready for its maiden flight, assuming that A380 chief engineer Robert Lafontan has signed the clearance for flight.

“Structurally, the A380 looks very good,” says Charles Champion, Executive Vice President A380 programme, assessing the current production status of his new giant. There are no fundamental problems, says the young-looking engineer, just the usual “minor problems” on the production side, such as production tolerances and new systems. “It runs better than expected. Naturally you get a lot of Problem Reports (PRs) on any completely new aircraft, including ours.” For example, current issues include power distribution with novel, electronic load management, cabin communications and even systems which, although proven on other aircraft, have to be re-certificated for the A380 against the latest and in many cases more stringent regulations.

To ensure that the above procedure runs smoothly and on schedule through to the A380 maiden flight, the MAP (“Mise au point”) department is taking charge. This is headed by Marc Cousin of the UK, who already has to worry about MSN 002 even before the maiden flight of MSN 001. “We need the second aircraft for the ground vibration tests that have to be carried out before the first flight. At issue here are the vibration characteristics and the vibration damping on the real aircraft, as opposed to the theoretical results of the flutter calculation.” The ground vibration tests entail attaching inconspicuous vibration generators to the jacked-up aircraft and measuring the accelerations. However, as Cousin explains, “It is not a violent vibration test. You would not see much on a film.”

The static test fuselage MSN 5000 with its wings is also needed before the maiden flight: it is used to calibrate the sensitive measuring devices for the structural loading which are to be installed on board MSN 001. The test fuselage is already parked in its “stretch bed” in the test hangar. As if one were dealing with a huge puppet, a complex structure consisting of 300 movable mountings with 2,000 force application points, through which aerodynamic loads can be induced, hangs down from a scaffolding constructed out of 1,000 tonnes of steel, the height of a house and almost opaque, which extends up to the ceiling. Initially the test engineers will concentrate on the “normal” limiting load, raising the A380 wingtips by up to four metres, but eventually, the ultimate load will finally be ascertained here by brutally yanking the wingtips of MSN 5000 upwards by ten metres. In a separate control room with 20 display workstations, it is possible to monitor 8,000 parameters during these tests. As well as these tests, the last piece of the rear fuselage section of MSN 5000, constructed out of carbon fibre, will undergo structural investigation in Hamburg. For this purpose, the massive rudder fin will be laid flat at 90 degrees in a hangar in Finkenwerder.

The director in charge of the A380 structure is the German Jan Stüben. He explains that the design of the A380 has been calculated “conservatively” and has additional safety tolerances built in to it. “We start on the safe side and then optimise the weight,” he says, explaining his strategy. “It is an interplay between strength and weight. The more test results we have, the more we can improve the structure. That was also the case with the A340-600.”

Despite the complicated selection, Stüben is convinced by the mix of materials used on the A380. “It may be unusual, but it is the best for the required tasks.” The attachment of the wing he sees as the biggest design challenge. “With the conventional configuration, we are coming up against a limit. The forces on the bolts are becoming enormous.” In his view, it is difficult to imagine any aircraft significantly bigger than the A380, at least in the classic configuration used today.

However, the A380 family, which was designed with growth in mind from the start and will later be supplemented by versions for higher take-off weight (HGW) and higher capacity (A380-900), is well within the limits of what is technically feasible. The precursor to those variants will be the heavier A380-800F, a freight carrier capable of carrying a 150 tonne payload, over whose detailed design the engineers are poring, now that the A380-800 design work is complete.

Robert Lafontan, Senior Vice President Engineering for the A380 programme talks of a new accent in material selection. “We decided in the middle of October to use more components out of aluminium lithium in future instead of carbon fibre reinforced plastic (CFRP). We can use that for the outside skin and also build stringers with it. Moreover, today we have ever better GLARE applications. This decision is not restricted to the A380, but applies across the company.”

Even if the recent weighing of the first real assemblies did not flag up any actual weight problem on the A380, reworking some of the components would make it possible to lose “hundreds of kilograms” (Lafontan) on the fuselage alone. The assemblies designed for the reinforced A380-800F cargo plane should therefore be adopted into the other A380-800 production at the latest from the first A380-800F production number, MSN 035, according to the chief engineer. Already today work is in progress on individual components for twenty A380-800's.

Lafontan explains the slight scepticism at Airbus over the material of CFRP, which stands in strong contrast to the Boeing concept for the 7E7, in terms of the lack of weight advantages in some cases. “Many component parts do not get any lighter when you build them out of carbon fibre.” Lafontan plans to retain the extremely strong, but relatively expensive CFRP for the outer part of the A380 wing. “For some tasks, carbon is the best solution. But for certain shock loads you have to take precautionary design measures. In our industry one has to consider the risk.”

To avoid the risk of any structural surprises, Airbus shipped a second winged A380 test fuselage with the internal factory number of MSN 5001 out to IABG in Dresden for dynamic structural testing at the beginning of October. At present the final assembly team, who have travelled in specially from Toulouse, are assembling fuselage segments and wings there in order that the test programme can commence in September 2005. Using hydraulic and pneumatic jigs, the aircraft can be exposed to the stresses and strains of 5,000 simulated flight cycles. The accelerated wear programme ranges from bumpy taxiing over poor runways through to the toughest turbulence, and should be completed in time for type certification in 2006.

From FLUG REVUE 12/2004

Last updated 11 November 2004

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