Plans for composite units delayed as first aircraft fly with aluminium versions
Honeywell and Dunlop Aerospace are preparing to deliver the first set of composite wheels for the Airbus A380 in time for the type's crucial rejected take-off (RTO) tests, after it emerged that the first aircraft is flying with conventional aluminium wheels.
The team of Honeywell and Meggitt-owned Dunlop won the sole-source contract to develop the A380 wheels and brakes in 2002, promising the world's first metal-matrix composite (MMC) wheels and high-density carbon brakes on a commercial transport.
Subsequently, however, it became apparent that the high-density carbon technology was insufficiently mature for implementation and, due to manufacturing issues, early A380s will have to be retrofitted with the MMC wheels at a later date.
Honeywell director A380 wheels and brakes Dan Szymanski says the two companies' complete system, including titanium torque tubes for the first time, among other advances, will save 400kg (881lb) per aircraft compared with conventional metal equipment. The MMC wheels alone give a 180kg advantage per shipset.
Szymanski explains that, early in the programme, Honeywell agreed with Airbus to design aluminium wheels as well as the MMC units as a "risk mitigation", following concerns that a new Dunlop manufacturing plant being built in Coventry – which would perform the work – would not be ready.
He says: "That site was not going to be ready for the A380, so we developed aluminium wheels to support the first four aircraft for flight tests, as well as early aircraft coming down the line."
The first MMC wheels are now undergoing qualification testing, ready for delivery in late July and retrofit to the first aircraft in time for the maximum-energy RTO test at the end of September. That test is important for the A380 because of its unprecedented 560t maximum take-off weight.
Szymanski says the plan now is to deliver another 11 aluminium shipsets, then to cut MMC wheels into the production line at A380 serial number 016 in October, and begin retrofitting earlier aircraft from January 2006, well before entry into service.
He adds: "The [problem with the new plant] was not apparent at proposal time but, very early on, as we began to lay out our plans. We could have had MMC delivered from a pilot plant, but that would have required us to requalify on the aircraft. So it was better to use conventional aluminium first. We have pretty much executed the plan as we jointly agreed with Airbus."
Regarding the brakes, he says: "We were working on an advanced friction material that ran into some technical hitches. That will not be available for the A380. It is still in research and development."
Instead, the brakes will incorporate Honeywell's existing Carbenix carbon, already used on Airbus and Boeing widebodies as well as many other types.
Source: Flight International