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.