Hopefully by now you have viewed the "Why Fly One?"
page and are cautiously enthused and hungry for information, so you
are ready for a little of the "nuts and bolts" of what exactly are
gyroplanes, where did they come from, how do they fly, where can I get one, and
why am I not crazy for even thinking about flying one? Since much has
already been written about these subjects, we would like to utilize words of
various friends around the world.
What is a Gyroplane?
A gyroplane is an aircraft that uses a spinning set of
rotor blades to provide lift similar to the fixed wing of an airplane. A gyroplane looks somewhat similar to a
helicopter, but unlike a helicopter it has no motor powering the rotor
blades. The blades spin, and generate lift, due to air flowing through
them as they are pushed through the air. Forward momentum is provided by a motor driven propeller
thrusting the aircraft forward.
Control for accent, decent, and left or right turns, is
accomplished by tilting the rotor blades and adding or reducing thrust. A rudder is also
used to point
the gyro into the wind.
History of Gyroplanes
Let's take a brief journey through
history and observe the development and technical advances of the gyroplane
Spanish inventor Juan de Ia Cierva built the first "Autogyro" in
1923 by combining a conventional fixed wing aircraft's engine and fuselage
with an overhead mast and three bladed rotor system. The Autogyro also
retained a short section of wing about six feet in length, presumably to
enhance in-flight stability. This first aircraft, and the two that followed,
were less than successful because they lacked the two most important factors
- stability and predictable direction control.
These problems were solved on Cierva's fourth aircraft, dubbed the "0-19
Autogyro," through the addition of a flapping hinge point near the rotor hub
which would allow for the rotor blades to equalize the lift between the
advancing and retreating blades. The C-19 Autogyro was first demonstrated in
England in 1925 for a group of military officers who were impressed with The
aircraft's performance and maneuverability.
1928 found Cierva giving demonstrations of the 0-19 and selling the
manufacturing rights to representatives from around the world. The American
rights were purchased by Harold Pitcairn who made a few design changes but
retained the basic design principles and features found on Cierva's machine.
Pitcairn used a more modern fuselage with better aerodynamic qualities for
his PCA-2 gyroplane, and offered two engines for use in the aircraft. Both
were radial aircraft engines mounted in the usual tractor configuration: the
first produced a massive 300 horsepower, the second a awesome 420! Pitcarin
also utilized a four-bladed rotor system with Cierva's flapping hinge.
Pitcairn produced and sold 24 of his PCA-2 gyroplanes over the next few
years. They showed the versatility and practicality they had been designed
for by carrying the mail over a federally contracted route, being used to
reach the scene of the news and for aerial photography by the "Detroit News"
daily newspaper, and by setting new world records. Amelia Earhart flew a
PCA-2 to the record altitude of 18,415 feet over Willow Grove, Pennsylvania
on April 8,1931.
Focke-Achgelis, the German aircraft company, became licensed by Cierva to
manufacture his patented components. For a number of years before the
outbreak of World War II, Focke-Achgelis produced the C-19 Autogyro, and
they drew heavily from the knowledge and experience gained from Cierva's
design to rapidly advance the development of their FA-61 helicopter. This
aircraft became the first fully controlled helicopter when it flew in 1937.
Autogyros were used briefly by the Germans during the course of the second
World War as aerial observation post for the U-boat attack submarines. Towed
behind the submerged submarines by a long cable, the glider pilots had a
broad view of shipping for miles, and could easily detect the widely scattered Allied
ships and relay this information over an intercom to the crew below. Because
of the difficulties experienced in retrieving the craft and pilot before
engaging in battle, the system was discontinued long before the end of the
1953 saw the rebirth of interest in the gyroplane with the invention of Dr.
Igor Bensen's patented "Gyrocopter." This two-bladed rotorcraft used a
teetering hub bar and rotorhead to equalize the lift from opposing sides of
the rotor disc. By using locally-available materials the home builder was
able to keep the construction cost down, and he could work on the aircraft
as his time and budget would permit. Factory-packed material kits were also
available; assembly time on either version often ran into the 150-200 hour
range. Amateur and professional builders have probably copied the Bensen
Gyrocopter more than any other aircraft throughout the history of aviation.
does a Gyroplane fly?
Lift on a gyroplane is provided by the rotor blade which is actually two
separate blades. Each blade looks somewhat similar to an aircraft wing only
smaller, skinnier and more flexible. The blades are connected together by
a hub bar which sits atop the gyro frame via a mast and a two axis pivot
assembly called the rotor head. The rotor head not only allows the blades
to rotate but also allows them to rock up and down as does a teeter-totter
(see-saw) board. As an aircraft wing develops lift moving forward through the air,
the rotor blades do the same only they are going around in a circle. Mr.
Bernoulli was responsible for explaining this fact of science, and it is based
on a difference in air pressure on top of and below the wing. As a wing
surface is curved on the top side, air must travel further and faster on the top to
reattach with the air on the bottom side at the back edge of the wing. This
results in less pressure on top, more on the bottom, and thus lift is
developed as the higher pressure on the bottom of the wing results in a
lifting force. Basically the faster the wing goes (faster rotation) the
more lift that is developed. (Mr. Newton also has a hand in the aerodynamics, inasmuch as air hitting the underside of the rotor and deflecting downwards provides an equal and opposite reaction of the rotor blade being forced upwards. Combined, both of these aerodynamic characteristics work toward the goal of providing lift.)
There is no motor power going to the rotor blades to make them
turn. Motor power simply pushes or pulls the gyro forward through the air.
Everybody has played with a windmill toy when we were kids, and it is easy
to understand that air moving through the blades will make them rotate and
I'm sure you can reason out which way they turn. The trouble is that they
don't rotate in the direction that you would think. They go against the air
airflow just as would a helicopter blade which has power turning them
causing air to be deflected downward. So how does a positive pitched rotor
blade turn in a direction that our initial logic says it shouldn't? This
is our first big mystery.
the rotor blades won't start by themselves in the opposing direction,
once started they will be kept rotating solely by positive
airflow. This is called auto rotation. It not only keeps the blades
rotating but also creates the lift to keep the gyro
airborne. Explanation of autorotation is a function of relative wind,
lift and drag being developed as lift is created. Maybe a little too
involved for this website, but please realize that you will have a full
understanding upon completion of your training.
The second mystery is how a set of flimsy, thin blades can
become stiff and develop lift? The answer to this is centrifugal force
being developed as the blades rotate. The faster they go around, the more
pull outward and the stiffer they get. Actually they bend somewhat and if
you looked at the blades from the side while they are rotating and lifting
the gyro, you would see that they are coned upward and look like the inside
of a bowl (that is somewhat exaggerated as the coning is very small). This is what gives the gyro positive
stability at all times. Think of it as releasing a small ball inside a
large ball. No matter where you let it go at, the small ball would
eventually come to rest on it's own directly at the bottom of the large ball
and stay stationary.
The third mystery is why the rotor blades must be allowed
to rock from side to side as they are going around in a circle. Remember
that the only thing that keeps the blades rotating is air moving through
them, and this can come only by moving forward or being in a head wind.
Actually as we are really talking about relative airflow, we can also be
moving straight down through the air assuming we had some altitude.
However, let's assume we are moving forward or pointing into a head wind,
then the blade advancing on the right moving into the relative airflow must
be going faster than the blade on the left side which is retreating from the
relative airflow. Rotor blades rotate clockwise when viewed from below.
Again remember that a faster moving blade develops more lift and
subsequently the blade will go up when it is on the right side and then down
when it rotates to the left side. This is called dissymmetry of lift and
would result in the gyro rolling to the left if the rotor blades weren't
allowed to rock as they went around.
So what do we know now? With a motor
either pushing or
pulling us forward the rotor blades will
rotate, lift will be developed and we will have control of the gyro.
However, let's assume the motor quits. We may quit going forward or up and
have to go down, even straight down, but relative airflow even straight up
is still airflow, the blades keep turning at speed and we have full control
of the gyro. It simply won't stall and fall out of the air as a fixed wing
aircraft will do at a reduced or even zero forward airspeed. It will,
however, come down! So one must maintain control and find a place to land.
In the early days of gyros (Dr. Bensen / 1950's) most gyro
rotor blades were started by hand. Today electric or hydraulic pre-rotators
are used for this purpose. Given a pre-rotator system or a strong wind
capable of getting the blades up close to flying speed, takeoff can be
accomplished in a very short distance - 20 to 50 feet. Normal takeoff runs
of 250 Ft. are common without a pre-rotator. Larger LSA-style gyroplanes are also, of course, heavier so their take-off roll -- even with a strong pre-rotator -- may require 500-700 feet.
Given a little practice, landings for many gyroplanes can easily be made
within the rotor blade diameter - 25 ft or less.
Here are some suggested books available on
Continue reading about some Common Mistakes when flying gyroplanes.