Blended Wing Body

Developing a Blended Wing Body BWB is more risky than designing a conventional aircraft. But if the risks are high, so too are the rewards. David Windle reports.

For several years Dr. Howard Smith of Cranfield University has been leading an investigation into an unconventional large aircraft concept. Some indication of how seriously his work is taken is the involvement of the Phantom Works, aerospace giant Boeing’s R&D unit.

The focus of Smith’s study is the Blended Wing Body (BWB). The contours of its wings and fuselage flow together to form an integrated lifting structure that resembles a flying wing. Strong, lightweight composite materials feature extensively and to drastically reduce noise its three engines are spaced around its centre line, on or just above the upper surface of its tail-less trailing edge.

While engineers and academics have been exploring the potential benefits of the BWB as a next-generation passenger and cargo carrier, their work has presented plane makers with a thorny question: in a climate of uncertainty, should they invest in a radical new type of aircraft, or should they continue to develop new conventional products with incremental improvements?

Despite its futuristic looks, the BWB Smith has designed will fit into the all-important 80m box with a landing gear track width compatible with existing airports.

Smith’s interest in the BWB is based on his belief that fundamental change in aircraft design is inevitable – and must be revolutionary rather than evolutionary.

‘The aerospace industry has for many years focused on one solution, which has now been refined to the point of diminishing returns,’ he said.

‘From the point of aerodynamic and propulsive efficiency there is little scope for improving the classic civil airline configuration.’

Since the tube-with-wings airliner was developed the world has changed. Air travel is commonplace, demand for seats shows no sign of letting up and pressure on air traffic control systems is intensifying. This has prompted calls for very high-capacity planes to move more people with fewer aircraft movements.

Competition between carriers has become increasingly ferocious. Add to these economic pressures demands for greater reductions in emission and noise levels and the realities of modern air travel are brought into focus.

It is against this backdrop that the BWB flies to the rescue. A twin-deck passenger-carrying BWB would seat 650-900, yet due to its highly efficient aerodynamics, reduced weight and the need for fewer, less powerful engines, it is predicted to use around 20 per cent less fuel than an equivalent conventional aircraft. The operating costs are projected to be reduced by around 15 per cent with weight down by 10-15%.

Developing a BWB is more risky than a conventional aircraft. Smith stresses the central role that risk-reduction techniques, computer modelling and sub-scale demonstrators play in his approach. Critical issues identified so far include: the pressurisation of non-tubular passenger cabins, flight-control characteristics and engine/airframe integration; plus how passengers would respond to fewer windows and the use of display screens to provide a view of the outside. No one is glossing over these design questions.

But if the risks are high, so too are the rewards. Smith summed it up: ‘He who finds the nerve to leap the chasm will win the future. Everyone will benefit, of course, but only those at the forefront stand to profit commercially.’

So what will become of the BWB? I believe it will happen. Most likely, major funding will come initially from military sources who recognise its potential as a multi-role, long-range, high-capacity aircraft.