Boeing's decision to make the 787 out of carbonfibre was the right choice at the time. It was also a kick-in-the-teeth wake-up call for a company that for decades had expected its products to be the foundation of every new aircraft.

As Tony Morales, global aerospace and defence marketing director of Alcoa - the one-time Aluminum Company of America - puts it, Boeing's move to slash aircraft weight with a radical composite fuselage and wing construction pushed Alcoa technology development into overdrive.

And, he claims, Alcoa engineers have responded with new alloys and construction techniques that are ready to fly - and can meet or beat carbonfibre on every performance measure throughout the build-fly-maintain-recycle aircraft lifecycle.

A combination of third-generation aluminium-lithium alloys and weight-saving selective reinforcement techniques promise to come in 10% lighter than composite-intensive aircraft. They also promise to produce aircraft that are 30% cheaper to manufacture, operate and repair than composite-intensive designs. And, says Morales, the "new" aluminium can match a carbonfibre fuselage for 787-style passenger comfort features, like higher cabin pressure and humidity, and large windows.

New alloys and construction techniques can also produce the slim, low-drag wing sections being achieved in carbonfibre and, says Morales, the "new" aluminium still offers inherent lightning-strike protection that has to be added via copper mesh or other conductors in a carbon structure.

Aluminium also matches carbonfibre for ease of inspection, but offers superior repairability. The only metric it cannot beat composites on is part count, says Morales.

Another key advantage of sticking with aluminium, he adds, is the avoidance of a range of programme risks that loom over any change to new technology. An airframer working in aluminium, he says, can stay with its existing certificated supply chain, and assembly workers do not need to learn new skills.

Easing the development process also cuts the financial risk associated with programme delays stemming from the introduction of new technologies, as well as the spillover effect on other programmes as engineers are pulled off of development projects to address unforeseen problems. "That risk has been greatly escalated on the last couple of airplane programmes," says Morales, indicating Airbus's and Boeing's A380 and 787 travails.

For airlines, he says, the fact that advanced aluminium skins and structures can be repaired using standard techniques is an advantage that reduces the worry that an aircraft may be stranded someplace for want of local repair capability.

Finally, he says, there is no trumping one of aluminium's strong suits, which given current technology is a severe weakness for carbonfibre: recyclability.

Clearly, with Airbus and Boeing wrapping up their twin-aisle A350 and 787 development programmes, Alcoa is jockeying for position on the next single-aisle programme and promises to have its technology package mature and ready for aircraft set to be delivered from 2015. In the single-aisle category, Morales believes aluminium holds two trump cards.

One is its durability, including resistance to the "ramp rash" these aircraft get from rough treatment in ground handling. New aluminium-lithium alloys are less dense than standard aerospace alloys, but allow for thinner skins which, with selective reinforcement of bonded fibre-metal laminates and other laser-welded reinforcement still provide better damage tolerance than current-generation aircraft.

And, aluminium-lithium alloys are significantly more corrosion resistant than the aluminium alloys they will replace. As a result, Alcoa is promising 12 years between heavy checks for a single aisle.

To illustrate the assembly concept - and support Alcoa's claim that new technologies can be produced using existing infrastructure - a fuselage panel developed by Alcoa and Spirit AeroSystems is on display at the Alcoa exhibit.

Globally, aluminium consumption is rocketing, and should double by 2020, driven in part by an expected doubling of automotive industry consumption. The push to reduce weight in aircraft and soaring rates of aircraft production will ensure that aerospace is using more aluminium than ever by the end of the decade, so Alcoa will not be dropping out of the aerospace business any time soon.

But if the engineers and sales people at this Pittsburgh-headquartered company that pioneered use of a remarkable structural metal in the 19th century get their way, aluminium will still be the main story of the second century of flight.

Source: Flight Daily News

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