thrust in aviation development

After Cayley, the development of the airplane proceeded along two lines: one was to design a wing configuration that would permit controlled and sustained flight, and the other was to develop the means of providing an aircraft with thrust. Although propellers had been used successfully to propel balloons (and were an element in many of Cayley’s designs), Cayley doggedly stuck to paddles and flaps, while others looked to propellers. Propellers had appeared on hot-air balloons even before 1800, but these were all hand-driven and ineffective in providing control in even the slightest wind. In most instances, the propellers used were taken off ships and often looked like small windmills.

A ship might go slower or faster depending on the efficiency of the propellers and the power of the engine, but a plane simply doesn’t get off the ground until it is propelled at a sufficiently high speed. As with many elements of flight, the Wright brothers, expecting to use marine propellers and finding them inadequate, created the technology themselves. One of the great achievements of the Wrights (mainly Wilbur), was to increase the efficiency of the propeller by fifty to seventy percent.

The way they did it was to look at the propeller not merely as a device for blowing the air one way so that the propeller (and the craft attached to it) would move in the opposite direction, but to regard the propeller as an airfoil turned sideways. As the blades of the propeller turned, in addition to screwing into the air and moving it to the rear (from which the other name for a propeller—”airscrew”—derives), the blades may be cambered so that the air pressure in the rear is greater than that against the forward surface, resulting in a net force forward. The Wrights further refined the propeller by varying the camber—decreasing it toward the tip—so that the aerodynamic force on the faster-moving outer part of the propeller would be the same as on the slower inner part. This design was to influence all future propellers used on aircraft.

The engine—or "power plant”—was also some time in coming. Cayley considered the steam engine and rejected it as too heavy, but, unlike the stubborn blind spot lie seemed to have had about propellers, he was very open-minded about engines, he considered using gunpowder and even attempted to construct an engine of his own that was a relativeof the internal combustion engine. Henson, on the other hand, believed that steam engines would improve and become lighter in time; the machines he designed were thus known as aerial steam carriages.”

The development of the internal combustion engine by Nikolaus August Otto 1876 changed everything, and one of the first to realise this was Samuel Pierpont Langley, secretary of the Smithsonian Institution. In spite of a frustrating and controversial career in aviation, Langley was a sophisticated and perceptive researcher who saw the potential of the gasoline-burning engine. He tried to contract for an engine that would deliver I 2 horsepower and weigh under one hundred pounds (45.5kg). but the manufacturer fell far short.

Fortunately, Langley had as his assistant Charles Manly, an engineering student from Cornell. Using a radial engine similar to that designed by Lawrence Hargrave in 1887, he built a power plant that weighed 208 pounds and produced an astonishing 52.4 horsepower. The \X/rights, also disappointed with available automobile engines, built their own engine with the help of their bicycle shop mechanic, Charles Taylor. It was not nearly as well designed as Manly’s; it produced only 12 horse-power and weighed one hundred pounds (45.5kg). It would not have been adequate for Langley’s machine or even for the Wrights’ had they not improved the efficiency of the propeller. Ignoring propeller design entirely, then, may have been the critical factor in Langley’s losing the race to be the first to fly.