Airbus concedes that the A340-500/600 family had a less than perfect introduction, and lays much of the blame on the aircraft's ambitious development programme, and partly on the late changes made to some systems.
"The dispatch reliability at entry into service was not what we would have hoped it would be. There were a number of issues which affected that," says John Grother, vice-president A330/A340 customer services.
"We set off to build a derivative aircraft, but over the course of a fairly extended period with the customer focus groups, the aircraft grew quite considerably, such that the -500/600 represents a 100t increase in maximum take-off weight over A340-300," he says.
"More changes were made than we originally considered and that probably led us in several areas to late developments."
A330/A340/A350 programme manager Olivier Andries says that there were more system changes than originally expected: "Compared to the A340-300, two thirds of the -500/600 is new by part number. Any system change will create a risk in terms of maturity and operational impact."
The large number of changes was compounded by the fact that, for this programme, the focus on maturity came after the suppliers had been selected, says Andries. He adds that, although suppliers – especially those of systems and buyer-furnished equipment – were aware of Airbus's maturity focus, "they were already selected, so the leverage on them was weaker than desirable. The lesson is that the maturity requirements have to be set right at the very beginning and as part of the supplier selection."
When the problems came to a head at launch operator Virgin Atlantic, Grother says Airbus "sat down with the airline and determined an action plan of what we could do to improve the reliability". This resulted in the installation of a dedicated "meet and greet team" at Heathrow. "Their job was to download the maintenance post-flight report that looks back at all failures during the flight and gives indications of what action needs to be taken by maintenance," says Grother.
The new galley cooling system developed for the -500/600 "gave us quite a few difficulties with early operators", says Grother, and had to undergo a significant upgrade.
"Rather late during the development of the aircraft we decided to install a galley that would meet future performance requirements – that trolleys should be chilled to 4°C compared to the earlier standard of 8°C. A remote galley cooling system was developed with a US vendor, but we all underestimated the complexities of such a system."
Grother says this meant that the development was "rather late" and the design "was not as mature as we wanted at service entry. We have completed a retrofit programme with the vendor and now have something that is working satisfactorily."
An example of a new system/new supplier combination is the fuel system, which has suffered ongoing problems with spurious fault messages, and came under increased scrutiny this year when a Virgin Atlantic A340-600 was forced to divert to Amsterdam after an engine failed due to a fault with the automated fuel management.
"Pilots have been being annoyed by having to ignore and reset spurious fault messages," says Grother. "The fault has been driven largely by a software problem in the FCMC – the computer that controls the fuel system – and the command and monitoring ‘com/mon' logic."
Airbus has recently completed a successful in-service evaluation of a new software standard that Grother says removes most of the spurious fault messages. "Last month we launched the campaign retrofit on the entire fleet."
However, this does not address the fault that caused the Amsterdam diversion, says Grother. "The combination of the fuel not being moved as expected, and some collector cells going to a low contents level without an announcement, had not been seen before. This will be addressed by another software standard that should be ready by June."
Grother says that the integrated drive generator (IDG) has suffered problems "for a couple of years. We've already had one retrofit, which proved to be inadequate."
He says the problem is with a diode pack that is part of the AC/DC rectification in the IDG, "which we're still micro-managing with Hamilton Sundstrand. Basically the diodes fail, which effectively makes the IDG inoperative.
"We've found a particular phenomenon if the IDG is engaged when the oil is extremely cold (ie -30-40°C). The more viscous oil can physically damage the diode pack," says Grother. "There is also a negative impact on the diodes with low-conductivity oils."
Over the 2004-5 northern winter there were a "significant number" of IDG failures, says Grother. "We've come out of the winter and there have been no failures."
Although the A340's minimum equipment list (MEL) allowed for a dispatch with one IDG failed, Airbus temporarily withdrew this allowance to prevent the possibility of a second failure down the line.
Hamilton Sundstrand has developed a new diode pack with much larger diodes and these are being evaluated in service. "In June we will asses the result and will take a decision whether to retrofit the entire fleet before the next winter," says Grother.
Although Airbus concedes the high number of service bulletins issued to fix problems has not been ideal, it believes this is indicative of its efforts to put things right.
Grother says Airbus has sought to minimise the burden on airlines by dealing with various fixes in parallel and using Airbus working parties to apply the modifications without charge. "We customise the packages for each airline to make sure we don't need dedicated downtime and work within existing maintenance schedules."
Andries is confident the -500/600 fleet can achieve its dispatch reliability target of 98.5% by the end of the year, compared with the current level of around 98%, an improvement on the initial 18-24 months in service, when it averaged 97-97.5%.
"We want to bring all the fixes that the airlines will have to implement together by mid-year, so by the end of this year we should see the results in the statistics," says Andries. "Our objective is to get 98.5% by the end of 2005."
Grother says that, in comparison, the A330 fleet is running at 99.1%, while the A340-200/300 fleet "varies wildly, but is between 98% and 98.5%".
MAX KINGSLEY JONES/TOULOUSE
Source: Flight International
