Delta Wing Phoenix Viper 175

Bill Bennett founded Delta Wing Kites and Gliders in 1969 to build and market boat-towed kites, such as the Delta Wing Model 162 (see NASM collection), flown by water skiers. Bennett fitted these gliders with flexible wings evaluated at NASA by Francis M. Rogallo. Hang gliders equipped with Rogallo wings spread around the world because they flew reasonably well, cost little to build, and were easy to transport. By the late 1970s, Bennett had started to modify the early Rogallo wing designs to improve safety and performance. Skilled pilots flying these new gliders, including the Phoenix and Mariah series (see NASM collection), could perform loops and wingovers.

In 1980, Bennett introduced the Viper with a stiffer and more aerodynamically efficient high-aspect ratio wing structure but without a significant increase in weight. He designed the Viper to appeal to pilots who had earned a 'Hang 3' glider pilot classification, an advanced skill rating. The lower wing fabric now extended from the leading edge more than half-way to the trailing edge and covered 57 percent of the lower wing surface area. Bennett devised new methods to stiffen the leading edge and he abandoned the cumbersome, drag-inducing leading edge ‘deflexor’ cables seen on earlier models such as the Phoenix VI and VI.B (see NASM collection). Bennett also omitted the drooped wingtips seen on the Delta Wing Mariah (see NASM collection). The Viper flew with other modifications including a new, lighter sail material, and a split keel. Despite all these changes, a pilot could assemble the Viper as rapidly and easily as pervious Bennett designs. The designation '175' refers to the area of the wing in square feet. Bennett sold the Viper in 1981 for $1,795.

Bill Bennett's Phoenix series of hang gliders is part of the second generation of late twentieth century hang glider designs. Bennett founded Delta Wing Kites and Gliders in 1969. He played a key role in making hang gliding popular in the United States when he developed Rogallo wing ski kites such as the Model 162 (see NASM collection) into gliders that pilots could launch on foot from the ground. Bennett continuously refined his designs to make them safer and to improve their performance. His work helped to grow the sport during the 1970s.

Australian John Dickenson gets too little credit for his monumental breakthrough to invent the technology that allowed pilots to precisely control a hang glider. Early in 1963, the Grafton Water Ski Club in New South Wales, Australia, asked Dickenson to build a kite for an upcoming water ski festival. Dickenson studied the classic flat pentagonal-shaped ski kite and noted its dangerous lack of control and stability. After exploring several ideas, he probably saw drawings of NASA’s Rogallo wings published widely in the popular press. NASA had found no reliable way to deploy the Rogallo wing from a spacecraft, but the wing’s simplicity, low cost, and flight stability may have encouraged Dickenson to choose it for his new ski kite. He made and tested models of a Rogallo-type wing and they showed improved stability, but control was little better than the classic ski kite.

Since Lilienthal’s first flights in 1891, pilots had clung to the framework of their hang gliders and tried to influence the direction of flight by swinging their legs and body to shift their weight in the direction they wanted to go. The pilots were positioned at the center of the wing and their range of movement was limited by the airframe enclosing them. Control was feeble at best.

While swinging his daughter sideways on a swing set in 1963, Dickenson had the flash of insight that gave pilots precise control and transformed the hang glider. Dickenson’s idea was brilliant and simple, and added little weight. It consisted of a control bar and a seat or harness suspended from the keel tube by a strap. He bolted the control bar directly to the overhead keel tube of the glider and just behind the control bar, and braced it with wires attached to the wing tips. From the hanging strap, he suspended the pilot’s seat. The strap supported the pilot like a pendulum and allowed him or her to shift their weight with ease, pushing and pulling the control bar to make the glider climb, dive, or turn.

Dickenson tested the controls on a half-size flexible Rogallo-type wing too small to fly. The tests were promising so Dickenson built a kite large enough to lift a person. On September 8, 1963, as John Dickenson looked on, a ski boat towed his friend Rod Fuller aloft for the first flight of a Rogallo-type wing ski kite with the improved Dickenson control system. By 1966, Dickenson was selling his adaptation of the Rogallo-type wing ski kite fitted with his new control system, and in 1967, he introduced fellow Australian Bill Bennett to the booming sport of flying ski-kites. Bennett quickly set altitude records in hang gliders equipped with Dickenson's control system. By 1969, Bennett had moved to California to sell commercial models under the Delta Wing Kites and Gliders brand name. The excitement of flying and the ease of access to flight provided by the Rogallo wing with Dickenson control appealed to the freewheeling sport leisure culture of the late 1960s, and across America, Bennett's kites grew in popularity.

Throughout the 1970s, Bennett designed and sold a succession of popular hang glider models, including the Phoenix and Mariah series (both gliders in NASM collection), and the Lazor. In 1980, Bennett introduced another upgraded hang glider, the Viper, with a stiffer, more aerodynamically efficient wing structure but without a significant increase in overall airframe weight. A pilot could assemble the Viper as rapidly and easily as pervious Bennett designs. Bennett designed the glider to appeal to competition pilots and individuals with a 'Hang 3' hang glider pilot classification, an advanced skill rating. The lower wing fabric now extended from the leading edge more than halfway to the trailing edge and covered 57 percent of the lower wing surface area. Bennett devised new methods to stiffen the leading edge and he abandoned the cumbersome, drag-inducing leading edge deflexor cables used on earlier models such as the Phoenix VI.B Jr. (see NASM collection). Bennett also did not use the rounded and drooped wingtips seen on the Mariah. The Viper flew with other innovations including a new lighter sail material and a split keel. The designation '175' refers to the area of the wing in square feet. Bennett sold Vipers in 1981 for $1,795 apiece.

By the mid-1980s, Bennett's hang gliders were no longer keeping up with the performance of gliders sold by other manufacturers. Delta Wing Kites and Gliders ceased operation in 1989. Bennett donated a Viper and five other Delta Wing models to the National Air and Space Museum in 1984 but nothing is known about the flight history of the Phoenix Viper 175 on display.