Aircraft Propeller
The
aircraft propeller looks like a simple mechanism to the uneducated individual.

To the educated, an aircraft propeller represents the highest sophistication in
aerodynamics, mechanical engineering and structural design. This report will
touch on the history of the propeller, from early pioneers/experiments,
advancement during/after the war, all the way up to current applications of the
propeller. The creation of the propeller can be traced back to Leonardo da

Vinci. Da Vinciís "helical screw" helicopter is believed to be the
ancestor of the air propeller and the helicopter rotor. The first idea of a
propulsive airscrew, however, belongs to J.P. Paucton, a French mathematician.

Paucton envisioned a flying machine that had two airscrews, one for propulsion
and the other for sustaining flight. The idea of using an airscrew for
propulsion was utilized during the late 1700ís to early 1800ís. Only after
experimentation did the inventors conclude that more propulsive power could be
obtained by merely straightening out the surface of the airscrew blades.

Attempts to utilize the "straight blade" propeller were made by balloonists.

These contraptions were quite strange and hardly fulfilled their purpose of
actually propelling the balloon. The basic propeller had evolved from the simple
concepts of da Vinci, and was slowly becoming an effective means of aerial
propulsion. To reach the next plateau of flight an increased knowledge of the
propeller would be needed, and the mysteries of the propeller and mechanical
power would need to be solved. These substantial tasks remained for aviationís
pioneers to tackle during the 19th century. Throughout the 19th century,
aviation pioneers explored and tinkered with the concepts of flight to design a
viable airship. Some pioneers tried to transform the balloons into navigable
cigar shaped airships by experimenting with sails, propellers, and paddlewheels
but all produced limited results. Other experimenters, who were convinced that
man flight should have wings, worked to establish basic principles in
aerodynamics, flight stability and control, as well as propulsion. Controlled
mechanical flight came on August 9, 1884. Charles Renard and A.C. Krebs flew the
airship "La France" on a closed circuit from Chalais-Meudon to Villacoublay
and back in 23 minutes. The airship "La France" was powered by a 9
horsepower electric motor that drove a 23ft diameter propeller and reached a
speed of 14.5 mph. This flight was the birth of the dirigible, a steerable,
lighter-than-air ship with adequate propulsion. Another important milestone in
aviation, was the understanding of aerodynamics. Sir George Cayley, a British
theorist, was acclaimed as the father of aerodynamics. He established a solid
foundation of aerodynamic principles that were essential to the success of other
pioneers. In 1875, Thomas Moy created a large model that had twin 12ft
propellers with 6 blades each! Interestingly enough these blades could be
adjusted to produce maximum thrust under certain conditions, an early
recognition of the need for changing blade pitch. Without a doubt, the most
expensive and spectacular project of its time was that carried out by Sir Hiram

Maxim. His numerous experiments with propellers, culminated in the construction
of a huge, four-ton biplane in 1890. This contraption was powered by two 180hp
steam engines that each drove propellers 17ft, 10inches in diameter and weighing

135lbs. The two-blade propellers, inversely tapered and squared at the tips 5 Ĺ
ft wide, were made of American Pine, planed smooth, covered with glued canvas
and stayed to the propeller shafts with steel wire to handle the high thrust
loads. These massive propellers produced 1,100lbs of thrust each during full
power while rotating at 425rpm. Maximís jumbo creation didnít last long
however, it jumped the test track and suffered extensive damage. Hands down, the
most influential aviation pioneers were the Wright brothers. They had concluded
that a propeller was simply a whirling wing, but didnít have the appropriate
information to consult when comprehending the fundamental principles of blade
shape and motion. This dilemma made designing the propeller one of the Wright
brothers most challenging problems. Despite the lack of previous information to
consult, the brothers were able to learn, through investigation and trial/error,
that large propeller diameters would produce high thrust for a given power
input. The brothers also determined that high torque produced by large, slow
turning blades adversely affected the flying qualities (p-factor). On their
first aircraft, they utilized 8 Ĺ ft propellers installed behind the wind to
minimize airflow disturbance, incorporated counter-rotating propellers to
eliminate the problems associated with torque, and gained thrust efficiency by
reducing the bladesí rotational speed using a chain and sprocket transmission.

The Wright brotherís propeller was 66% efficient which was much higher that
any other propeller of the time. The foundations of a disciplined approach to
propeller