The Defiant has one engine in the front and another in back; such centerline-thrust designs enable an airplane to continue flying safely if either engine shuts down. Centerline thrust, however, has drawbacks. “When you have a pusher-propeller aft of the wing, it vibrates and creates noise,” Rutan says.
Rutan flew the Defiant as his personal aircraft for years, but he wanted an aircraft that had the range to go to Australia or Europe. He began thinking of a long-range twin at about the time the Catbird won the 1988 CAFE 400 race for efficiency, fuel economy, speed, and payload capacity. The Catbird still holds two speed records.
“I decided that I’m going to do a twin with the same type of attention to performance that I had put into the Catbird,” Rutan says. “My plan was to design the lowest-drag light twin that I could, and while I was at it have a lot of fuel, make a lot of range, and of course have the Defiant, or better, engine-out characteristics.”
At a presentation for the Society of Experimental Test Pilots, Rutan explained the Boomerang’s performance by walking his audience through a list of incremental changes to a traditional twin-engine design—a Beechcraft Baron, in fact. The series of changes transformed the conventional twin into an airplane that could fly symmetrically on two engines or one (see diagram, p. 42). In both the Catbird and the Boomerang, Rutan reduced drag by using a dolphin-shaped fuselage that narrows between the cabin and the tail. He modified airfoils used on his early craft, like the Voyager, to create an efficient, low-drag airfoil for the Boomerang’s wings.
Rutan knew he wanted a turbocharged airplane, like the Catbird, because it would enable him to fly at much higher altitudes, where, in thinner air presenting less resistance, the airplane could fly faster, or farther, using less fuel.
Built of lightweight composites, the Boomerang can carry five people, their luggage, and 171 gallons of fuel almost 1,900 miles (1,652 nautical). Running its two Lycoming engines (210 horsepower on the fuselage; 200 on the nacelle) at 75 percent power, a pilot can cruise that distance at 302 mph. Reducing the power settings to 37 percent will stretch the range to more than 2,960 miles cruising at 215 mph and 20,000 feet.
For six years, beginning in 1996, Rutan flew everywhere in the Boomerang. In 2002, a series of heart surgeries limited his flying. When he announced his retirement from his company, Scaled Composites, in late 2010, he planned to donate the airplane to a museum, but the more he thought about the idea, the less he liked it. Instead, he began looking for “someone who could enjoy its features and would work to restore it and keep it flying indefinitely.”
At the time, Tres Clements, a 28-year-old engineer who had been at Scaled Composites for a year and a half, was one of several volunteers working at night and on weekends on the last aircraft Rutan designed before he retired: a twin-boom, roadable aircraft known as the Bipod. (It’s not uncommon to find lights on in the Mojave Airport hangars late into the night as dozens of aircraft designers and builders work on their personal projects.) When Clements asked Rutan what he planned to do with the Boomerang, Rutan answered, “I don’t know. Do you want it?” At first, Clements thought he was joking, but that’s how he became the caretaker of the historic aircraft. Clements spent the next four months restoring the Boomerang, with the help of a team that included former Scaled test pilot Mike Melvill and engineer Ryan Malherbe. In July 2011, Clements, Malherbe, and Bob Morgan, the project engineer for mothership WhiteKnightTwo, flew the restored Boomerang to Oshkosh for a tribute to Rutan and his extraordinary airplanes.
Flying the Boomerang
“The first time I pulled an engine back, I was like, Wow, I can’t believe it actually flies like this,” Clements says. “It’s not doing what you’d expect. It’s flying really nicely when it should be flying really bad.” Last October, when Clements flew the airplane from Mojave to Oregon Aero, a company north of Portland that had offered to install a new interior, I hitched a ride.
Getting into the Boomerang’s cockpit isn’t easy. There isn’t a traditional door. Instead, there is a large oval window, which is on a rail and slides back to provide a wide space to climb through. The window is unlatched by a lever on the fuselage that folds down to double as a foothold.