Students at the UK's Cranfield University have unveiled the A-9 Dragonfly, their concept for a "lighter and greener" 270-seat airliner with a joined wing - sometimes called a box wing.Photo: Cranfield University
The A-9 is the work of 66 Aerospace Vehicle Design MSc students at Cranfield. Last year's design was the A-8 Hummingbird, a fuel-efficient short take-off and landing regional airliner.
The main feature of the A-9 is its box wing. This comprises front and rear wings joined at their tips by vertical surfaces. The structural bracing this provides allows use of thin, high-aspect-ratio wings for reduced drag and weight.
Lockheed Martin and NASA studied joined wings in the 1990s, the company flying a scale model of a proposed box-wing airlifter.