Tiltrotors for the Rest of Us

The latest evangelist for a civilian vertical-takeoff-and-landing craft is aeronautical engineer Abe Karem, designer of the Predator unmanned aerial vehicle. His company, Karem Aircraft, with offices in Lake Forest, California, and Fort Worth, Texas, is developing the TR53 AeroTrain, which it describes as a “VTOL 737.”

The AeroTrain would be similar to the V-22 Osprey, a tiltrotor now in military use in Iraq and Afghanistan, but much larger. In addition to vertical takeoff, it would be capable of cruise flight at 400 mph, while featuring the Boeing 737’s passenger capacity. The AeroTrain aims to cut down on flight delays by eliminating some of the time and real estate that fixed-wing aircraft operations require. The idea is to avoid the need for runways and for thousands of passengers congregating at an airport, where  everyone boards different airplanes to different destinations—an inefficient system that produces traffic jams on the ground and in the skies.

While helicopters have been an essential part of civil aviation for decades, they’re good only for slow, short flights carrying a few passengers—hardly practical for ferrying business travelers or tourists between cities. But tiltrotors can combine the range and speed of fixed-wing aircraft with the VTOL capability of a helicopter. A tiltrotor can land pretty much anywhere with a relatively small, flat surface—a parking lot or even the top of a skyscraper—take on passengers, and be on its way.

The TR53 derives from an aircraft Karem designed for the U.S. Army’s VTOL Joint Heavy Lift requirement and from the unmanned Optimum Speed Tilt Rotor A-160 Hummingbird, which he designed for the Defense Advanced Research Projects Agency. When Boeing bought Karem’s Frontier Systems in 2004, and with it the Hummingbird OSTR technology, Karem kept the rights to apply the technology he developed for the UAV to a manned vehicle. “We’re hard at work on the TR53,” Karem says, “including analyses on the schedule-critical subsystems, mainly the tilting propulsion system.” During that system’s development, the AeroTrain will use the same engines as the V-22 Osprey: 6,200-shaft-horsepower Rolls-Royce AE 110Cs. Karem hopes to start production in 2018.

Two prototypes of the nine-passenger Bell/Agusta BA609, the first civilian tilt­rotor, have logged hundreds of test-flight hours. But the possible $15 to $20 million price tag is giving pause to corporate flight departments and other potential buyers, who might ultimately decide that, for roughly the same price, they’re better off with a new bizjet. The BA609 has yet to enter production, although Bell/Agusta has taken some preliminary orders.

NASA test pilot Warren Hall recalls his first flight, in the early 1980s, in the Bell XV-15 tiltrotor, the experimental predecessor of the V-22 and BA609: “Right after I got out of the airplane, I thought everybody ought to have one,” he says. “The BA609 is essentially the XV-15 turned into a much bigger V-22. I’m sold on it.” But Hall is doubtful about scaling up the concept to airliner size: “As the aircraft get bigger, you have to have more room” for landing.

Still, with airline traffic and delays getting worse, the appeal of VTOL flight grows. It’s now mostly a question of convincing passengers, the government, and the aviation industry that compared with conventional airline travel, these unusual hybrids could be more practical and economical.

Mark Wolverton is a frequent contributor.