Delta Wing Phoenix VI B Jr.

In 1973 and 1974, Bill Bennett and his hang glider designers experimented with several variations of the standard Rogallo wing. He then incorporated the results into a new line of hang gliders called the Phoenix series. On these gliders, Bennett increased the leading-edge convergence angle from 80 to more than 95 degrees. Total wing surface area was slightly less than standard Rogallo models, but the aspect ratio (wingspan to wing chord ratio) increased substantially. The first Phoenix hang gliders flew with a long fantail, a device thought to improve stability. As Bennett continued to develop the Phoenix series, he increased the leading-edge convergence angle even further, and removed the fantail after flight experience showed that it did not increase stability. The docile handling characteristics and good stability of the Phoenix VI made it a popular trainer at hang glider flying schools. More experienced pilots also favored this model type because it flew relatively fast, had good rough air penetration and handling characteristics, and the glider could soar on updrafts far better than earlier standard Rogallo designs. This success encouraged Bennett to develop the Phoenix series further, and variations continued to appear well into the 1980s.

In the next variant, the Phoenix VI.B, Bennett and Boone made 'deflexor' cables mounted on the wing leading edges a standard feature. Pilots could tighten or loosen these wires to change the wing’s shape for better flying performance and increased stability. During assembly at the factory, technicians rigged and tuned the glider to fly with a tendency to pitch up in high-speed flight. This built-in auto-recovery mode helped pilots recover safely from high-speed dives. The VI.B also used wing tip battens arranged in a radial pattern. This technique made the tips stiffer, reducing drag and improving roll response. The keel of the 'VI.B was shortened and Bennett added additional battens that extended all the way from the wing leading edge to the trailing edge. With these modifications, performance improved at low and high speeds.

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 their hang gliders framework 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. Their range of movement was limited because the pilot was positioned at the center of the wing. 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 braced it with wires attached to the wing tips. From the hanging strap positioned just behind the control bar, 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 beneath the wing, 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-type wing with Dickenson control appealed to the freewheeling sport leisure culture of the late 1960s, and across America, Bennett's kites grew in popularity.

In 1973 and 1974, Bennett and his designers experimented with variations on the standard Rogallo wing, and then used what they learned to design a new line of hang gliders called the Phoenix series. Bennett increased the leading-edge convergence angle from 80 to more than 95 degrees. This change reduced the sweep angle of the wing and increased the span. This reduced the wing surface area but increased the aspect ratio (wingspan to wing chord). Bennett also added a longer keel tube called a fantail, a feature thought to improve stability. As Bennett continued to develop the Phoenix gliders, he increased the leading-edge convergence angle even further and removed the fantail after flight experience showed that it did not increase stability.

By January 1975, Bennett and chief designer Richard Boone had completed the Phoenix IV. This variant used more rounded wing tips to improve the glider’s stability, but the modification made the glider more difficult to turn and reduced stability in turbulent air. Bennett and Boone solved this problem when they introduced the Phoenix VI. They made pockets in the sail to hold metal tubes called battens. The battens curved up slightly at the wing trailing edge to reduce the wing angle of attack at the wing tips. This design feature reduced stall speed and helped prevent one wing tip from stalling, a condition that could result in loss of control. Batten tips also kept the center of lift point closer to the center of gravity, improving overall control of the glider.

The docile handling characteristics and good stability of the Phoenix VI made it a popular trainer at hang glider flying schools. More experienced pilots also favored this model because it was capable of higher speeds and handled well in rough air. The glider flew better in ridge lift and in thermals than earlier standard Rogallo designs.

The success of the Phoenix VI encouraged Bennett to develop the model further, and variations continued to appear well into the 1980s. The next variant was the Phoenix VI.B. Bennett and Boone retained the same 'deflexor' cables mounted on the Phoenix VI wing leading edges to further stiffen and shape the wing for better performance and increased stability. During assembly at the factory, technicians rigged and tuned the glider to pitch up in high-speed flight. This built-in auto-recovery mode was aimed at helping pilots recover from high-speed dives. The designers shortened the keel of the Phoenix VI.B and added more battens to the wing to stiffen it further and improve performance across a broader speed range.

Bennett offered the Phoenix VI.B in three sizes, Junior, Standard, and Senior. Pilots who weighed from 63.5 - 90.7 kg (140 - 200 lb) selected the Junior. The Standard was designed for pilots weighing 68 - 95.3 kg (150 - 210 lb), and the Senior for pilots weighing 72.6 - 108.9 kg (160 - 240 lb).

By the mid-1970s, many hang glider enthusiasts were making cross-country flights. The technological innovations that Bennett and Boone had designed into the Phoenix VI.B made it a good choice for flights in the varying wind conditions that might be encountered when flying cross-country. The deflexor cables and battens made the wing stiff enough to improve handling in rough air. Several Phoenix VI.B pilots set records for distance and altitude.

Delta Wing Kites and Gliders ceased producing gliders in 1989. Bill Bennett donated a Phoenix VI and a VI.B Jr., along with four other Delta Wing hang gliders, to the National Air and Space Museum in 1984. The flight history of the Phoenix VI.B Jr. on display is not known.