T H E   H O U S T O N   A R E A   G Y R O   C L U B
Chapter 62 of the Popular Rotorcraft Association
--- Houston 
Texas ---

 Why Fly One | All About GyrosMeetings | Club Info | Training | Events | Links | Glossary | Guestbook | Forum | Gallery 

 


 

Buy a T-Shirt!

All About Gyros

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 industry.

                                       

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 war.

                                     

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.

How does a Gyroplane fly?

Lift 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 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. 

There is no motor power going to the 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.

While 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 to 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 (somewhat exaggerated).  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 under control and one must 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.

Given a little practice, landings can easily be made within the rotor blade diameter - 25 ft or less. 

Suggested Books available on Gyros

Common Mistakes

Quick Links
Most links open an external window


LSRC Meetings


Rotor Flight
Dynamics

Commander Elite
Air Command



Popular Rotorcraft Association

The Lightning
Sport Copter

For more links, click here

 

 

Top

   Webmaster: Robert Laird

Home