Horatio Phillips and Cambered Wing Design

Horatio Phillips advanced the discipline of applied aerodynamics with his wind tunnel experiments in the early 1880s. These experiments quantitatively demonstrated George Cayley's theories relating to cambered airfoils—that cambered airfoils produce more lift than flat airfoils. Phillips used the results of his experiments to build three flying machines that, although they had only limited success, applied his theory of lifting surfaces.

Phillips used the results obtained in his wind tunnel experiments to design a series of cambered airfoils based on the shapes of birds' wings. He called these the "Phillips entry," or "blades for deflecting air." They had greater curvature on the top than on the bottom and were called "double-surface airfoils." In 1884, he obtained a patent for eight of these airfoil sections, which were of various widths and curvatures. The theory of lift that these wings demonstrated was based on the variation in camber between the upper and lower surfaces of the wing. If the curvature of the upper surface of a wing was greater than that of its under surface, according to this concept, the air would flow over the upper surface at a greater velocity and produce lower pressures than on the underside. Hence an upward force—lift—would be generated as the higher pressure under the surface sought to become equal with the lower-pressure air above the surface.

In 1891, Phillips filed a patent for another cambered wing section. In this patent, he described how the section reacted in the airstream. He stated that when the airstream moved over the curved upper surface of the airfoil, the air pressure would decrease. Therefore, the lifting action of the airfoil was due to a combination of the lower pressure exerted on the upper surface and the higher pressure exerted on the lower surface. By creating a double-surface airfoil with less camber on the lower surface than on the upper surface, the air pressure would be higher underneath and lower on the upper surface. This would create more lift. He concluded that force would be greater above, in the form of negative pressure than below, which was applied in the form of positive pressure.

Phillips' designs demonstrated the first truly modern airfoils. His findings were widely disseminated, and thereafter all serious flying-machine developers used cambered airfoils.

Using the knowledge he had acquired, Phillips in 1893 produced a flying machine that resembled an open venetian blind on wheels. Sources differ in their description of the flying machine, but its wings consisted of 50 slats, between 19 feet (5.8 meters) and 22 feet (6.7 meters) long by 1.5 inches (3.8 centimeters) wide that were mounted two inches (five centimeters) apart. The apparatus measured 9.5 feet (3 meters) high and rested on a long wooden frame 25 feet (7.6 meters) long. A coal-fired 6-horsepower (4.5-kilowatt) engine turned a single twin-bladed pusher propeller at a rate of 400 revolutions per minute. The entire machine weighed between 350 and 385 pounds (159 and 175 kilograms) and rested on a tricycle undercarriage. It was tethered on a circular track with a 628-foot (191-meter) circumference where it moved at some 40 miles per hour (64 kilometers per hour). The two back wheels, which supported most of the weight, rose from the track for a distance of 150 to 250 feet (46 to 76 meters).

His 1904 multiplane was another application of the theory of lifting surfaces. Again, the wings looked very much like the slats of a venetian blind. This apparatus had 20 lifting elements. It tail unit was in the shape of a cross and was supported by a three-wheeled undercarriage. The engine, built by Phillips himself, was a four-cylinder water-cooled in-line engine that produced 22 horsepower (16.4 kilowatts) and powered a wooden tractor propeller. It was 13 feet 9 inches (4.2 meters) long, 10 feet (3.1 meters) high, weighed 600 pounds (272 kilograms), and could move at 34 miles per hour (55 kilometers per hour). Its frame was made of spruce, ash, and steel tubing and was covered with a calico fabric.

The multiplane was tried out at Streatham, England, and managed a short "hop" of about 50 feet (15 meters).

Phillips' final effort at flight came in 1907. This aircraft was a larger version of his 1893 plane. This machine had four venetian-blind-wings in tandem and was powered by a 22-horsepower (16.4-kilowatt) engine that turned a tractor propeller. This plane flew some 500 feet (152 meters). It was the first powered flight in England. Although he did not continue building planes, he had clearly demonstrated that flying machines should always have cambered wings.

--Judy Rumerman

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