Murray Hunter - University Malaysia Perlis
other concept had been dreamed about more than the ability of man to
undertake powered flight. Ever since the Greek Mythology of Icarus
and Daedalus, man has been on a great quest to discover the
secret of flight and when man finally managed to fly, this discovery was
to change the way he lived upon this Earth. Like the advent of the
automobile, powered manned flight was not a single invention but a
gathering together of necessary knowledge to allow flight to be
possible. This knowledge began being collected by the Chinese who flew
kites for the first time somewhere around 500 BC.
The kite was an important step in achieving powered
manned flight because it showed that something heavier than air could
stay aloft. The kite may have been the invention of the Chinese
philosophers Mozi and Lu Ban during the 5th
Century BC. Although not fully understood at the time, the kite showed
the basic laws of aerodynamics at work. Air flowing over a kite’s wing
will have a high pressure below the wing and a low pressure above the
wing, giving the kite lift. This lift also produces drag at the bottom
of the kite opposite to the oncoming wind. When the kite is tethered to
a guide-wire the forces of the wind against the tension from the
guide-wire forces the kite into the air along a vector opposed to the
tension of the guide-wire and wind. Some kites have tails to stabilize
the direction of the kite adding the force of drag to the equation
pulling on the tail, thus keeping the kite stable and upright.
A box kite design provides relatively high amounts of
lift and most of the early aircraft of the Twentieth Century were
inspired by this design. The box kite was invented by the Australian
inventor Lawrence Hargrave in 1893 in his attempts to develop his own
manned flying machine. Series of tandem box kites were able to lift
Hargrave 16 feet off the ground.
In 1738 a Dutch-Swiss mathematician published an
important aerodynamic principal in his book Hydrodynamica, which
stated that any air (or fluid) flow as speed increases will result in a
simultaneous decrease in pressure over a solid surface, which became
known as Bernoulli’s principal. Air running over the top of an
airfoil will run faster than the air running under the bottom of the
airfoil thus creating a decrease of temperature and pressure which
provides lift. The significance of this to flight is that Bernoulli’s
principal explains the concept of lift and allows lift to be
calculated on airfoils.
In 1799 Sir George Cayley was credited with formally
identifying the four aerodynamic forces acting upon flight – lift,
gravity, thrust and drag. Cayley believed that that any drag created by
a flying machine must be countered by thrust in order for level flight
to occur, which led to a better understanding that any design of a
flying machine must minimize drag. These discoveries led to the
development of cambered wings, which enabled them to create the force of
lift for an aircraft. According to a recent discovery of Cayley’s school
notebooks, he pondered over the problems like the angle of attack much
earlier than previously thought in his early years.
Cayley designed an efficient cambered wing with the correct dihedral
angle that provided lateral stability in flight, where he deliberately
set the centre of gravity below the wings for that purpose.
Cayley’s model gliders incorporated all these features, monoplane wings
with back horizontal stabilizers, looking similar to modern aircraft of
today. There was possibly a glider built by Cayley in 1853 that was
piloted by his grandson George John Cayley.
The propeller has a long history of development for
nautical use which had to be applied to flight. One of the major
challenges to the Wright Brothers in developing an airplane for their
first flight at Kitty Hawk was that there was no aircraft propeller
readily developed, so had to develop one on their own. They found that a
propeller is essentially a wing and therefore they utilized early wind
tunnel data on their wing experiments. They found that the relative
angle of attack of the propeller had to be different along the propeller
blade and therefore had to be twisted slightly.
The Wright brothers believed that the ability to fly
depended upon balance and control, rather than the power of an engine to
propel the airplane forward. This perhaps came from their background as
bicycle makers where balance was essential. Control in the air was an
important issue as there had been many deaths of aeronauts in gliding
and balloon accidents over a number of years.
The Wright brothers further believed they had enough
knowledge about wings and engines and decided it was important to
practice control in gliding before powered flight so the needs of
control could be understood.
They believed that previous practice used by Lilienthal of balancing and
controlling a glider through redistributing body weight was fatally
flawed. Many before them
including Langley and Chanute considered changing direction in midflight
would be like moving a ship’s rudder for steering while the aircraft
remained in straight and level flight.
Wilbur Wright observed that birds change direction in flight by changing
their angle at the end of the wings to make their body’s roll to the
left or right and he thought that this would also be a good way for an
aircraft to change direction by banking left or right by changing the
wing tilt through the use of a moveable airfoil on the sides of the
wing. Again this was something similar to a bicycle going at high speed
where a rider would distribute his or her weight to the side of a turn.
In 1900 the Wright brothers after researching the best
place to do glide tests and taking advice from Octave Chanute went to
Kitty hawk, North Carolina. The area had a good breeze coming onshore
from the Atlantic, a soft sandy ground to land on, and was relatively
remote for privacy. The first glider was based more on the work of
previous pioneers and resembled the Chanute-Herring glider which flew
well near Chicago back in 1896 and some aeronautical data that
Lilienthal had published. The wings were cambered according to the
theories of Sir George Cayley. The Wrights placed a horizontal elevator
in front of the wings as they believed this would help them stop any
nose dives that killed Lilienthal
and did not build a tail for the glider as at this stage as they thought
it unnecessary. Most of the glider tests were unmanned with the glider
held by ropes so glide characteristics could be studied.
The second glider in 1901 had its wings greatly enlarged
in an attempt to increase lift. Approximately 100 flights were made at
varying distances from 50 to 400 feet. The glider stalled a number of
times but “pancaked” out and landed flat
due to the forward elevator. This changed the brothers thinking towards
the canard design, which they
used until 1910. In general the second glider was very disappointing as
it failed to yaw adequately to the wing ailerons, where the nose of the
glider pointed away from the turn as the wings produced differential
drag and didn’t have the lift that they had expected. This left the
Wright brothers feeling very down about the prospects of manned flight.
The Wright brothers discovered that the equation that
Lilienthal had been using to calculate lift was incorrect. Lilienthal
and the Wright brothers both used the “Smeaton coefficient” in
the lift equation which had a constant of 0.0054, overstating lift. The
Wright brothers believed and determined through some bicycle tests that
the coefficient was more like 0.0033 and adjusted their designing
accordingly. Knowing that building gliders was expensive and trial and
error was very time consuming they built their own wind tunnel so they
could test models to speed up their experimentation and learning. These
experiments proved to be very fruitful and they made an important
discovery that longer and narrower wings (i.e., larger aspect ratio)
would provide a better lift to drag ratio than broader wings. They also
reduced the camber of airfoils which made them more efficient for
banking. They totally discarded Lilienthal’s calculations and relied
solely on their own data.
The third glider had some other design changes including
a rear fixed vertical rudder which would assist in turning. The brothers
flew the third glider unmanned like the first two trials. The glider
gave the expected lift and allowed tighter turns without the amount of
differential wing drag that occurred on the earlier gliders. However the
rudder caused a new problem. When in a tight turn and trying to level
back out again the glider failed to respond to the airfoil corrections
and persisted in a tighter turn where the glider would slide towards the
lower wing. The brothers found that by making the rudder movable this
problem did not reoccur so with a movable rudder and wing airfoils the
pilot had to control both the airfoils and rudder when maneuvering the
glider. This enabled the brothers to make very controlled turns.
The three-axis control for the glider was a major
breakthrough for controlled flight. It made the aircraft very
controllable in flight and was the result of almost 1,000 test glides at
Kitty Hawk. Some aeronautical historians believe that this is where the
airplane was really invented.
The powered Wright Flyer I constructed of spruce and
covered with muslin. The engine was built with an aluminum block by the
brothers. The Wrights decided on twin pusher counter rotating propellers
to cancel out the torque. They suffered many delays at Kitty Hawk with
broken propeller shafts. After a number of attempts the brothers finally
got the airplane off the ground on 17th
December 1903 with a flight distance of 120 feet. The first flights
received little publicity. Over the following year the second aircraft
the Wright Flyer II made many flights at Dayton with many hard landings
and minor mishaps. Much progress was made in 1904 with some longer
flights lasting a few minutes but the airplane was still very difficult
In 1905 the brothers made all the controls independent of
each other so pitch, roll, and yaw could be controlled separately of
each other. After a nearly fatal crash the brothers rebuilt the flyer
with a much larger rudder and forward elevator placed further away from
the wings. This made control much easier and led to a number of much
longer flights. Ironically the media had ignored this story that Wilbur
and Orville Wright made the first flights with a powered flying machine
and later would become national heroes at their own doorstep.
The brothers believed that they now had a flying machine
with practical utility that they could sell. They were finally granted a
patent in 1906 and in 1907 went to Europe to sell their airplane. In
early 1908 the Wright brothers finally signed contracts with a French
company and the US Army. Wilbur made a number of demonstration flights
showing advanced maneuvers during 1908 which captured the attention and
admiration of the world.
The Wright brothers’ patent was challenged vigorously in
the law courts for a number of years and Wilbur Wright also challenged
any other flyer who infringed them. This took up a lot of time and it
prevented the brothers from developing new aircraft designs. By 1911 the
Wright airplanes were considered inferior to many of the new European
designs. Wilbur passed away in 1912 and the brothers won their court
case against Curtiss which had been going on for a few years. With the
arrival of the First World War, the US Government found that American
technology was behind the European builders and encouraged companies to
cross license their technologies.
Businesswise the invention of the airplane did not lead
to a great number of aircraft sales and the brothers formed an
exhibition team which was later disbanded due to a number of team member
deaths. Between 1910 and 1916 the Wright Company operated a flying
school at Huffman Prairie, Dayton, training more than 100 pilots. In
addition with the large number of airplane accidents and deaths the
safety of the plane came into question by the US Army. Orville Wright
sold the Wright Company in 1915 and took on public service as an elder
aviation statesman becoming director of the National Advisory Committee
for Aeronautics (NACA), which he served for 28 years. It was only after
the First World War when airplanes made a contribution to field warfare
as a reconnaissance, fighter and bomber, and larger airplanes could
carry passengers and cargo with much better safety that the aviation
industry started to boom from the 1920s onwards.
So what are the lessons we learn from the invention of
What we see is that an invention cannot occur until all
relevant knowledge that makes it possible exists. There must be no
knowledge gap, or else any idea is a fantasy. For example, Jules Verne’s
imaginative novel From the Earth to the Moon in 1865 could only
become reality with the Apollo Moon landing in 1969 when all necessary
technology actually existed.
However the inventor must go the final step and either
synthesize all previous knowledge or incrementally enhance what
knowledge already exists to complete the invention. This often requires
having the confidence to disregard previous generally accepted knowledge
with your own generated knowledge obtained through your trials and
What we also see is that any invention that does not
fulfill the present needs of consumers or industry will not initially be
commercially viable. In the cases of the early automobiles and aircraft,
they were not at an advanced enough state for potential users to accept
them because of the primitive state of the invention and social
situation surrounding it, i.e., early automobiles not practical due
to faults and UK laws had to be amended to make the invention acceptable
an means of transport.
Inventions can only be commercially successful is if a
use is found for it, i.e., early aircraft could be utilized in a war
situation during the First World War. The story of the development
of the airplane shows how essential trial and error or learning by doing
is essential to the successful development of any invention.
Notes and References
Hudson, S.W. & Ruhen, O. (1977). Lawrence Hargrave: Explorer, Inventor and
Aviation Experimenter, Cassel, Sydney.
Dee, R. (2007). The Man Who Discovered Flight: George Cayley and the First
Airplane, Toronto, McClelland and Stewart.
Ackroyd, J.A.D. (2002). Sir George Cayley, the father of aeronautics, Notes
Rec. R. Soc., Vol. 56, No, 2, pp. 161-181.
Dee, R. (2007). "The Man Who Discovered Flight".
Crouch, T.D. (2003). The Bishop’s Boys: A life of Wilbur and Orville Wright,
New York, W.W. Norton & Company.
Tobin, J. (2004). To Conquer the Air: The Wright Brothers and the Great Race
to Flight, New York, Simon & Schuster, P. 53.
This was a very different attitude to other pioneers at the time like Ader,
Maxim, and Langley who believed that after attaching an engine to an airframe
they could just go out and fly it without any experience.
Crouch, T.D. (2003). The Bishop’s Boys: A life of Wilbur and Orville Wright,
New York, W.W. Norton & Company.
Tobin, J. (2004). "To Conquer the Air"
Jakab, P. L. (1997). Visions of a Flying Machine: The Wright Brothers and the
process of invention, Washington, DC, Smithsonian.
Canard is French for duck and in aeronautic refers to a wing configuration where
the forward wings have a smaller area than the back wings, which adds to lift.
Langewiesche, W. (1944). Stick and Rudder: An explanation of the art of
flying, New York, McGraw-Hill.
Tobin, J. (2004). "To Conquer the Air", P. 211.
However the Wright Brothers themselves can be part of the blame for this as they
discouraged media attention in fear of competitors stealing their ideas and they
would not be able to get a patent.