1903: Airplane - The book of science

Airplane
Toy helicopter
Kites and gliders
Controls
Data
Wing
Propeller
Engine
Instability
Commercial
Dreams of flying
Commentary

Wilbur Wright, Orville Wright aerodynamics

Airplane

Wilbur and Orville Wright
demonstrated the first
heavier-than-air
powered
sustained
controlled flight
on 17 December 1903.

Toy helicopter

Alphonse Pénaud was the first
to power a model flying machine
with a rubber band.
In 1870, his helicopter featured
two counter-rotating propellers with leaf-like blades,
one above and one below the spinning rubber band.
In 1878, the Wright brother’s father gave them one
and they began to build their own.
They called them bats
and dreamed of building one
big enough to carry them both.

Kites and gliders

Considering a kite
sailing in the air, Wilbur figured
the tension on the kite string
was the sum of its lift and drag—
the lift pulling vertically
against gravity,
the drag horizontally
along with the wind—
and the angle of the string
directly reflected
the balance of forces.
The brothers measured wind speed
using a French, hand-held anemometer.
They measured the tension of the kite string
using a spring scale tied to the line
and measured the angle
using a surveyor’s inclinometer.
With the tension and the angle,
Wilbur calculated the lift and drag
of this triangle of forces
using elementary trigonometry.
This is why at Kitty Hawk
they flew their gliders as kites.
Instead of risking their lives
from the top of a hill,
they could calculate lift and drag
of their machines in flight
and thereby tell whether
it performed as they expected—
whether it would support
a man in flight.

Controls

The Wright brothers realized
Lilienthal had died in 1896 because
he couldn’t control his glider.
They studied birds in flight.
Soaring birds
adjusted roll, pitch, and yaw
with graceful shifts of wing and tail.
Roll, pitch, and yaw
skewed a glider dangerously
in flight.
One by one, the brothers
developed mechanisms and skills
to control their path in flight.
*
When a bird elevates its tail
its body tilts up.
On their flyer, the Wright brothers
placed the elevators
two movable horizontal wings
in front of the wings.
*
To roll, birds adjust their wings
like the vanes of a windmill.
How to do this with a biplane
was unclear
when the mechanism had to be
both simple and light
until Wilbur, absent-minded,
squeezed opposite corners
of a slim inner-tube box
and noticed that squeezing one way
tilted the right side up
and the left side down,
while squeezing opposite corners
reversed the warping.
With a set of cables
the brothers could twist the wings
of their glider to roll either way
to control lateral movements.
Warping the wings acted
on exactly the same principle
as raising and lowering ailerons
on opposite fixed wings.
*
Warping wings to steer into the wind,
their glider tended to skid to the side.
The wing with the highest angle of attack
presented more surface to the wind,
which skewed the flyer
away from their intended turn,
so the brothers replaced the fixed tail
with a rudder rigged to turn
in the opposite direction of the yaw.
*
Warping the wings
controlled the roll.
Moving the elevator
controlled the pitch.
Turning the rudder
controlled the yaw.

Data

Their 1901 glider did not produce the lift
the brothers thought it should
during their tests at Kitty Hawk,
so they began to doubt
Otto Lilienthal’s
lift and drag data.
*
To separate lift from drag
George Spratt had suggested
a simple apparatus.
The brothers attached a horizontal wheel
at the front of a bicycle
and on this wheel they mounted a curved plane,
a miniature wing,
and ninety degrees from the wing
they mounted a flat plane.
They set the wing at the angle of incidence
indicated by Lilienthal
and they set the flat plane
perpendicular to direction of movement.
Lilienthal’s data showed that
lift should equal drag
so that the lift of the curved wing
should balance the drag from the flat plane,
but, peddling to get their wind,
drag exceeded lift
and the wheel turned
instead of balancing in the wind.
*
To more accurately test
Lilienthal’s data,
they built a wind tunnel
and developed testing techniques.
They invented a balance
to accurately determine
the lift and drag
of their miniature wings.
With the wind tunnel
they discovered
that Lilienthal’s data
was nearly correct
but John Smeaton’s
coefficient of air pressure,
which Lilienthal used to calculate lift,
was way off.
*
The camber of Lilienthal’s wing
was the section of a circle.
Using their wind tunnel,
the Wrights found
a parabolic section
provided better lift.

Wing

The Wright brothers called their flying machine a flyer
and they called its wings aeroplanes,
the word being derived from ancient Greek
meaning “wandering in the air,”
so we now name the airplane after its wings.

Propeller

Since nothing on a flyer stood still
it was difficult to imagine how to make a propeller.
“It was apparent,” the brothers realized,
“that a propeller was simply an aeroplane
traveling in a spiral course.”
after hatchet and hacksaw
they made a propeller whose cross section
was curved like a wing.

Engine

An engine for the Wright flyer
had to be both powerful and light.
They were not able to buy an engine
that weighed 180 pounds or less
and delivered at least 8 horsepower,
so, with Charlie Taylor, they made their own,
a four-cylinder water-cooled engine
with an aluminum crankcase
that produced 12 horsepower.

Instability

The Wright brothers knew
a bicycle without a skilled
rider and a means to steer
was laterally unstable.
No rider, no pilot
can walk, let alone run,
without temporarily tilting
his or her body out of balance.
No reason to suppose
a flying machine would
differ except in having more
dimensions of instability.

Commercial

Commercial airlines
take the magic
out of flight.
Too fast, too high,
too protected
from the wind.
A good thing
to serve the needs
of a corporation.
But I’ll make a kite;
I’ll find plans for a glider
and make my own.
If I work hard,
maybe I’ll discover
the incantation
and there’ll be
no seat belt or air bag
on my magic carpet.

Dreams of flying

indicate overreaching
trying something risky
something trying
to strain the shackles
expand the boundaries
and the possibility of failure.
One seldom fails in dreams
though often for real
and must continue to dream.

Wilbur and Orville Wright were scientists as well as inventors. They were the first to measure the performance of a full-sized flying machine in flight. They built their wind tunnel to test the results of Otto Lilienthal for understanding lift and drag, and corrected the coefficient of air pressure that Lilienthal used, 0.005, given by John Smeaton. The correct value is 0.00327; the Wright brothers derived the value of 0.033.