Today, a boy begins what the Wrights will finish. The
University of Houston's College of Engineering presents
this series about the machines that make our civilization
run, and the people whose ingenuity created them.
Sir George Cayley was born in
1773, in Yorkshire. He was studious from the start, and
determined to solve the old riddle of human flight. He
was 10 when the French invented hot air balloons, but
they weren't good enough. Cayley knew that serious flying
machines would eventually have to be heavier than air.
By his early twenties, he'd built a laboratory at his
ancestral home of Brompton Hall. He was doing
sophisticated aerodynamic studies. He also had the wits
to hang out in a local watchmaker's shop -- studying
mechanics at the same time he read Newton.
Cayley made several important discoveries. He realized
the secret of flight wasn't to be learned from birds'
flapping wings, but by watching birds glide with their
wings fixed. He identified the three forces acting on the
weight of any flying object -- lift, drag, and thrust. He
conceived the idea of a lifting airfoil.
In a remarkable burst of insight, he saw that trout have
the ideal, minimum-resistance, body shape for an
airplane. Why a trout and not a bird? A century later
we'd have rules of dynamic similitude. They show that a
small fish in water behaves more like a large machine in
the air than a small bird in the air does.
By 1799 he had the basic shape of a modern airplane with
a fuselage, wing, and tail. By 1804 he was flying model
gliders. In 1809 and 1810 he published a series of
articles on his theories and experiments. He also showed
how to scale up his models to make controllable
Cayley scrupulously backed everything up with
calculation. Newton had proposed a simple theory of lift
which Cayley correctly took to task. Newton's theory
makes sense only at speeds far greater than sound. It
wasn't used for anything until after WW-II.
Cayley had brilliantly analyzed two of the three forces
needed for aerial navigation -- lift and drag. The third
force was thrust, and all we had were steam engines. They
were still far too large and heavy. So Cayley put aside
his studies and took up Whig politics. He became a member
But others read his principles and followed steam engine
improvements. By mid-century the now-aging Cayley could
no longer dodge his legacy. In 1853 he built a full-size
glider and ordered his coachman, John Appleby, to test
it. An eager crew towed it into the sky. Appleby glided
safely down a hill.
Appleby felt plenty of fear and little sense of history.
He immediately tendered his resignation. Cayley died soon
after without ever creating successful powered flight.
But neither did anyone else until 1903 -- 50 years later.
Of course the Wright brothers read Cayley's work and
were, by then, able to build an aluminum
internal-combustion engine. So we forget Cayley, but make
no mistake, his ghost finally rode with the Wrights, at
I'm John Lienhard, at the University of Houston, where
we're interested in the way inventive minds work.