Vertical Flight

Able to operate freely from nearly any place on earth, helicopters come closer than any other aircraft to achieving the birdlike freedom humanity has always envied. However, the same technology that makes this possible also prevents the helicopter from achieving the speeds and payload capacity of airplanes performing similar functions.

The Autogiro, which used unpowered rotors to provide most of its lift, was the first successful rotary-wing aircraft. The first decades of the 20th century yielded helicopters that could fly, but only marginally. In World War II, refined versions performed medical evacuation and antisubmarine warfare. During the Korean and Vietnam wars, the helicopter finally emerged as an invaluable, and then essential, military tool. Notable technological innovations have occurred since then, and today helicopters are widely used in civilian roles as well.


Bell XV-15 Tilt Rotor Research Aircraft at the Udvar-Hazy Center

Bell XV-15 TRRA (Tilt Rotor Research Aircraft), Ship 2
The XV-15 Tilt Rotor technology demonstrator was the culmination of efforts begun in the early 1950s to produce an aircraft that could takeoff, land, and hover like a helicopter, but with the speed of an airplane. The rotor pylons tilt from vertical to horizontal to eliminate the speed barriers imposed on conventional helicopters by retreating-blade stall and allowed the XV-15 to operate at speeds of 550 kph (345 mph TAS).

This is the second of the two XV-15s built by Bell under a joint NASA/US Army program. It served from 1979 through 2003, demonstrating operations under a wide range of conditions and logged 700 hours in testing. Its success encouraged Bell and the US Marine Corps to develop a scaled-up Tilt Rotor, the MV-22, as a replacement for Marine transport helicopters. In association with Agusta Aerospace, Bell also developed the Model 609 civil Tilt Rotor with experience gained from the XV-15 program.

More information: Bell XV-15 TRRA (Tilt Rotor Research Aircraft), Ship 2

Bell 47B

Bell 47B
In 1946, the U.S. Civil Aeronautics Authority awarded the first civil helicopter certification to the Model 47. It was the first Bell helicopter type to enter production. Although initial sales failed to meet Lawrence Bell's expectation of a post-World War II civil aviation boom, later versions saw significant service in the Korean War and other conflicts, and it became a highly successful commercial model with some logging over five decades of service.

The two-seat Model 47B was the first commercial evolution of Bell's pioneering Model 30, also designed by talented engineers Arthur Young and Bartram Kelley. This example, the 36th built, served over a period of 40 years as a factory demonstrator for Bell, newsgathering helicopter, crop duster, trainer, and performed power line patrols and aerial photography missions. In 1989, Douglas Daigle purchased the helicopter, had it restored, and set the world's hovering record of fifty hours, fifty seconds. Its last flight occurred in December 2004 - more than 57 years after its first flight, making it the longest-flying helicopter in history.

More information: Bell 47B

Autogiro Company of America AC-35 at the Steven F. Udvar-Hazy Center

Autogiro Company of America AC-35
Developed for a Department of Commerce competition to create an aerial "Model T," the innovative two-seat AC-35 Autogiro could takeoff and land in 52 m (173 ft). After folding back the rotors, the pilot could switch engine power to the rear drive wheel, allowing street speeds of 40 kph (25 mph). The AC-35 initially suffered from stability problems, but further experimentation resulted in an aircraft that was safe and relatively easy to fly.

The AC-35 prototype performed well, but the $12,500 price tag was several times the average family income of 1936, and did not meet the goal of an affordable $700 aircraft for the suburbanite. Harold Pitcairn's Autogiro Company of America built only one AC-35 but continued work on an improved version. The beginning of World War II and the advent of the practical helicopter spelled an end to Pitcairn's hopes for quantity production of the type.

More information: Autogiro Company of America AC-35