THINK about it, aircraft don’t look much like birds. But should they?
This question is one a pair of engineers in California and South Africa inadvertently answered when they set about re-thinking the ubiquitous tube-and-wings aircraft structure from scratch, in order to make airplanes more fuel efficient.
The modern aircraft works well, but from a fuel efficiency standpoint, could they be designed more aerodynamically in order to reduce drag and increase lift?
Geoffrey Spedding, an engineer at the University of Southern California, and Joachim Huyssen, of Northwest University in South Africa, felt they could, in theory, but lacked experimental evidence. Now they have found it.
They have made a simple modular aircraft in three configurations: a flying wing alone, wings plus a body and wings plus a body and tail.
It turns out that they had independently redesigned a bird shape, but without specific reference to anything bird-like.
They started with the entire plane as one big wing.
Then they added a body designed to minimise drag and, most critically, a small tail, which essentially serves to undo aerodynamic disturbances created by the body.
Airflows were examined at various relative angles for the wings, body and tail, as part of a search to achieve greater lift, to carry more cargo, and lower drag, to improve fuel efficiency.
The duo made the stipulation that for any given mission, the best plane is the one that generates the least drag.
The flying wings alone provide an ideal, albeit impractical, baseline, since it’s hard to carry people or cargo in such a shape.
The presence of a body, unfortunately, immediately reduces lift and increases drag.
It was found that the addition of just the right kind of tail, however, can restore lift and reduce drag, occasionally to nearly wing-only levels.
A few years ago a glider with the modest tail design enjoyed a successful test flight, but larger and commercial test prototypes have not yet been tried.
Spedding recognises that the design of real aircraft is a compromise of many engineering, economic and psychological constraints.
Nevertheless, he believes much can be done to make these machines more energy efficient.
“The most important point is that we may be wasting large amounts of fossil fuel by flying in fundamentally sub-optimal aircraft designs,” he said.
“At the very least, we can show that there exists an alternative design that is aerodynamically superior.
“One could well argue that there is now an imperative to further explore this and perhaps other designs which could very well make a significant difference to our global energy consumption patterns.”