An aircraft revolution on the horizon

Engineerblogger
March 29, 2012

Artist's rendering of D-Dalus. Image: Grapham Murdoch

You've got planes, helicopters, blimps, and balloons. Throw in the gyrocopter, a powered paraglider, and a few other odd-ball inventions, and you've pretty much covered the ways we can fly. Not since Sikorsky started mass producing helicopters in 1942 has there been a real revolution in aviation.

However, if the makers of the airfoil- and rotor-free D-Dalus manage to tame their prototype, the latest upheaval may be just around the corner. As conceived, it will be able to take off vertically, fly in any direction, hover in the worst weather imaginable, and turn on an airborne dime, making it the ideal drone. "We don't really want to see this used as a weapons platform," says project leader David Wills. "But we're businessmen and we want money."

The aircraft is the product of the mind of Meinhard Schwaiger, "A charismatic little guy—five-foot-four, shock of white hair, and a bow tie," as Wills describes him. Schwaiger holds some 150 patents and made his first killing in plastics extrusion. The concept for D-Dalus first came to him while he was in Moscow watching "a tedious documentary about helicopter crashes," says Wills. In trying to imagine an aircraft capable of hovering with greater ease and safety, he turned his mind to the Voith Schneider propellers that give tugboats the strength and near-instantaneous maneuverability necessary to haul water vessels many times their size.

Designing the D-Dalus

Schwaiger sketched the idea down on a pad and assumed it would wind up in the rubbish bin in the cold light of day. But when, the next morning, he ran a CAD model of the engine, he realized that the only thing stopping such a contraption from getting in the air was time, money, wherewithal, perseverance, frustration, marketing, tinkering, mistakes, recoveries, and a whole lot of thought.

D-Dalus is made of four axles each with a series of carbon fiber disks that spin at 2,200 rpm. Surrounding the disks are blades that redirect the thrust. Working in concert they will give the craft 360 degrees of mobility. To do so they need to be able to handle about 1,000 Gs, a force the needle bearings in Schwaiger's initial prototype could not withstand. "Most would have said 'Oh, that's why no one else has done this before,'" says Wills. "Instead, he sat for a year and a half designing a fiction-free bearing." The result was akin to a beer keg topped by a glass table topped by a beer keg. Stand on the table and you'll feel an easy rock between the barrels.

D-Dalus is made of four axels with a series of carbon fiber disks that spin at 2,200 rpm.

The current prototype has only made its way through a few of those 360 available degrees. It's managed to get off the ground and take a sharp horizontal turn. But just before its public debut at the Paris Airshow, it did a bit more than that. "We were hanging on to the beast with a safety rope, but we didn't hang on strong enough," says Wills. "It lurched and started fighting the rope aggressively. It really was like Frankenstein on the end of the rope, bits were flying at 2,000 rpm, and they're pretty expensive bits too." The breakdown was the result of a number of factors: An engine less powerful than expected; bolts that could not withstand high vibration; engine placement that made the craft act as a pendulum; a racecar driver at the controls who was not used to maneuvering in more than two dimensions.

The damage meant that untold dollars and hours were down the drain. Not enough to ground the project, though. "You ought to see some black and white footage of Sikorsky sitting on his helicopter almost having his head lopped off," notes Wills. "I said 'These things happen.'"

D-Dalus at the Paris Air Show.

The New Look
The latest assemblage has a new engine, its weight is down to less than 400 pounds, and it is merely awaiting the careful hand of renowned stunt helicopter pilot Rudiger Feil to operate its joystick.

If the aircraft proves itself worthy, it will soon be performing feats impossible to its airborne-brethren. "Imagine them looking for Somali pirates, or Iranian missile launchers," says Wills. "They could work together in a swarm. If you need to use the same port you were bombing 10 minutes ago—the same thing that was throwing lifeboats on the back of the ship early on can act as a crane."

Voith Schneider Propellers have been working in water for the better part of a century, so one might wonder why a D-Dalus-like vehicle hasn't already popped up to take care of Somali pirates and the like. "There are lots of people who have gotten close," says Wills, "It's just that my little Einstein has solved all the things at once."

Source: ASME