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Vendredi, 29 Juillet 2011 19:30

Burt Rutan's Boomerang: Safety Through Asymmetry

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Burt Rutan's Boomerang: Safety Through Asymmetry

OSHKOSH, Wisconsin — The Boomerang, designed by aviation legend Burt Rutan, is one of those creations that draws a crowd due to its innovation, unmatched performance and unusual appearance. When word got out earlier this summer that a crew was working on the asymmetric airplane and would have it here at Airventure, it generated tremendous excitement.

Never mind that the design is more than 15 years old and has been here several times.

But the fact it is old news doesn’t matter. The unusual airplane still turns heads and, perhaps more often, leaves people scratching their heads. Rutan calls it his greatest accomplishment in general aviation.

The airplane was developed to create a safe and efficient twin-engine aircraft. Yes, traditional twin engine aircraft are considered safe because the second engine offers redundancy. But if an engine were to fail at a critical time, such as take off, there is added danger because of the resulting asymmetric power. If the pilot is not skilled, and well practiced in emergency maneuvers, there is a high risk of a crash because the airplane suddenly has tremendous drag on the side with the dead engine and thrust on the side with the working engine.

Burt Rutan's Boomerang: Safety Through Asymmetry

The pilot flies from the right seat of the Boomerang. The window on the right side slides back to allow the pilot to enter the airplane.

Rutan started with the basic design of a Beechcraft Baron, a popular twin engine airplane, and developed the Boomerang through a series of incremental changes. All of the asymmetry is there to eliminate the asymmetry experienced during an engine failure. If an engine were to fail in the Boomerang, the pilot doesn’t need to do much to maintain control. The airplane continues flying straight.

The pilot workload reduction can be felt during normal flight, says Tres Clements, the Scaled Composites engineer responsible for returning the airplane to flight-worthy status after years spent in storage. Clements says the rudder pedals are rarely touched during flight, something unheard of for most pilots, especially those who fly small twin engine airplanes.

“During takeoff, just put your feet on the floor,” Clements says. “You’re just going to screw something up. Best thing is to take your feet off the pedals and let it fly.”

Clements and a team of volunteers – including the airplane’s original test pilot and private astronaut Mike Melvill – put in more than 1,500 hours during the past several months getting the Boomerang ready to fly again. The airplane was pulled from a hangar in February after sitting for nine years. It flew by the end of March just before Rutan retired from Scaled Composites.

Burt Rutan's Boomerang: Safety Through Asymmetry

The passenger area in the Boomerang is sparse with seating for three. A plush interior was never a priority for Rutan.

For the first few flights, the Boomerang flew with the original 1990s-era Apple 5300C PowerBook used for the engines and systems monitor.

“We pulled this thing out and blew the dust off,” Clements says of the PowerBook. “We plugged it in and it made the old PowerBook chime when it loaded up.”

Clements says Rutan was excited that his old computer still worked, but obviously there’s been a lot of technological progress since then. Donations from a handful of companies provided new instrumentation for the cockpit, but Apple gets a nod with the addition of an iPad dock.

Clements says it’s been a lot of fun showing the airplane at Oshkosh, where you’ll find a crowd around the Boomerang all day long. People are amazed by the unusual craft because nothing is symmetrical. The right fuselage has the cockpit and passenger seats with a 210-horsepower engine. The left one is shorter and includes the baggage compartment and a 200-horsepower engine mounted five feet behind the right engine.

The right wing is 57 inches shorter than the left, the wings are attached at different angles (sweep). Even the tail is different on each side.

Burt Rutan's Boomerang: Safety Through Asymmetry

The Boomerang is asymmetric from tip to tail.

The pilot flies from the right seat. There is a control stick on the left, but no rudder pedals. And the performance is impressive. The Boomerang can cruise faster than a similar-sized twin while using about half the fuel. Max speed is just over 300 mph. Normal cruise speeds are around 250 mph, and if the airplane is slowed to its most efficient speed, it can fly more than 2,300 miles on a full fuel load of 168 gallons.

Clements plans to continue flying the Boomerang. The airplane will return to Mojave after Airventure, and there are still some modifications Clements is looking forward to.

Like many of Rutan’s creative designs, the Boomerang never saw production. It is literally one of a kind. But with the attention the airplane received at the world’s biggest airshow this week, many in the aviation community are hoping the unusual airplane might attract the attention of a potential customer who might take the Boomerang to the next phase of development.

Photos: Jason Paur/Wired.com

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