Picture a small jet taking off with a perfectly ordinary straight wing. Then, in the air, the whole wing slowly pivots — not sweeping symmetrically back on both sides like a fighter, but rotating flat around its centre, until one tip points forward and the other trails behind, the wing lying diagonally across the fuselage like a scissor blade. It looks like something has gone badly wrong. It had not. It was the whole point.

This was the NASA AD-1, and between 1979 and 1982 it flew 79 times to prove one of the strangest good ideas in aeronautics: the oblique wing.

The scissors wing

The idea came from Robert T. Jones, a largely self-taught but brilliant NASA aerodynamicist. His calculations and wind-tunnel work suggested that at high speed a single wing set at an angle across the aircraft — oblique rather than swept — would generate far less drag than conventional wings. For a supersonic airliner, he estimated, the payoff could be enormous: up to twice the fuel economy. Jones knew exactly how odd it looked, and he had a ready answer for the sceptics.

The little demonstrator

To test the concept without betting a fortune, NASA built something deliberately cheap and slow: the AD-1, a tiny fibreglass jet barely bigger than a home-built, pushed along by two small turbojets. The oblique-wing concept was Jones’s; the actual little airframe was designed by Burt Rutan — the same maverick behind the Voyager and the asymmetric Boomerang — and built by Ames Industrial Corporation.

On 21 December 1979, NASA test pilot Thomas McMurtry lifted it off the lakebed at Edwards Air Force Base for the first time, wing straight, in a gentle 45-minute hop. It was the first flight of a piloted oblique-wing aeroplane in history.

Straight to sixty degrees

Over the next two years the team crept the wing round in careful steps — 15 degrees, 20, 45 — and on 24 April 1981 finally swung it all the way to the 60-degree design angle, proving that an oblique-wing aircraft really could be flown. But it was not pleasant. As the angle increased, the aircraft’s handling grew steadily worse, its motions cross-coupled and awkward; one pilot reportedly likened flying it to pushing a shopping cart with a bad wheel. The concept worked, but taming its quirks on a full-size airliner would demand sophisticated computer flight control that did not yet exist.

Why we still don’t fly oblique

The oblique wing never quite dies. NASA and Northrop later studied full-size oblique flying wings, and the Pentagon has periodically funded fresh looks at the idea, always drawn by that promise of low supersonic drag. But the combination of demanding flight control, structural headaches, and the simple fact that it looks alarming has kept it on the ground. The AD-1 itself now sits quietly in a museum, its wing straight.

Still, it did something few experimental aircraft manage: it turned a genuinely bizarre theory into a real aeroplane that flew, and flew safely, 79 times. Like Rutan’s lopsided Boomerang, the AD-1 is proof that in aviation, symmetry is a habit — not a law of nature.

Sources: NASA (“Thinking Obliquely,” Bruce I. Larrimer); NASA Armstrong/Dryden fact sheets; Wikipedia; Hiller Aviation Museum.