Gyroplane Pilot Q&A
Sierra RotorCraft Club
In addition to training the pilot to avoid these problems, designers are helping too. Early gyros did not have a horizontal stabilizer, but many people now agree that having a horizontal stabilizer greatly reduces the risk of these problems (PIO & PP0) due to the engine thrust moving over the stabilizer, and have now incorporated them into their designs.
Complete List of Gyroplane Instructors
JON ROBERT STARK, CFI-gyro, helicopter, Instrument helicopter 3567 SUNNYDALE CT, SAN JOSE, CA, 95117-2952, USA
Popular Rotorcraft Association
Welcome to the homepage of the Popular Rotorcraft Association. Based in Mentone, Indiana, USA at the PRA Mentone Airport, PRA was started in 1962 by Igor Bensen, the inventor of the famous Bensen Gyrocopter. Since then it has grown to include rotorcraft of all sorts with members in over 80 countries. We are a group of people who love homebuilt rotorcraft -- gyroplanes and helicopters that they build and fly themselves. These rotorcraft enthusiasts get together to exchange ideas, information, help one another, promote safety and help with flight training.
How does a Gyroplane fly? Very informative description of the physics of gyroplane flight.
With proper training, a gyro pilot can fly on windy days that his fixed wing counter part cannot fly on. He can also perform maneuvers that will leave his fixed wing counterpart scratching his head in amazement. As our British gyro enthusiasts are fond of saying, "The gyroplane is far more nifty and maneuverable".
GyrosAway - Introduction
Gyroplane Buyers Guide - From Popular Mechanics Magazine
Carter Aviation Technologies - Home Page
Carter†Aviation Technologies is a research and development company, pioneering new aviation concepts. Our primary focus is the slowed-rotor compound aircraft, a vertical takeoff and landing aircraft that uses the rotor for takeoff and landing, and a small, efficient wing for high speed flight, up to 500 mph, all with much less complexity than a tilt-rotor or other vectored thrust vehicle.
Complete List of Gyroplane Instructors
Autogyro History and Theory
This essay describes autogyros and how they work, gives a brief history of their early development, explains their differences with other aircraft, and explains why they were never accepted. It then explains some modern autogyro concepts.
Autogyro - Wikipedia, the free encyclopedia
An autogyro, also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust. While similar to a helicopter rotor in appearance, the autogyro's rotor must have air flowing up and through the rotor disc in order to generate rotation.

how to fly autogyros
Autogyros are often regarded by fixed-wing aircraft pilots as "dangerously unstable", which is certainly true if one tries to fly an autogyro using fixed-wing principles. Piloted properly, a autogyro is slightly safer than a fixed-wing aircraft because it cannot stall. A "stall" does not mean an engine-out event, it means a fixed wing aircraft is travelling too slowly for the wings to produce lift. Since the rotor of a autogyro is always spinning, it cannot stall. If forward airspeed becomes zero, the autogyro will slowly drift to the ground, rotor still spinning. A vertical landing in this manner will not critically damage most autogyros.

One weakness in certain types of autogyro is pitch instability (pitch is the tilting up or down of the craft as viewed from the front or the back). Pitch instability can be a problem because autogyros lose rotor control authority in negative-G forces (positive-G forces push people into their seats; negative-G forces make people float out of them, such as driving over a hump back bridge at high speed in an automobile). Negative-G forces "unload the rotor" and rotor control authority is lost. A flying autogyro hangs from the rotor much like an object hung from a string. As long as the plane is hanging from the rotor, stability is maintained. The instant zero or negative-Gs are introduced, rotor speed begins to decay and the forces stabilizing the plane are lost.

Negative-Gs can be caused by Pilot-Induced Oscillation, or PIO. PIO happens when a pilot adjusts his pitch too much too quickly, then makes a countering control input to bring the pitch back. The countering input often overcompensates, and the autogyro begins to buck like a bronco. You can see a similar effect when some learner-drivers are doing kangaroo-hops in a car with a stick shift and clutch. This is most likely at higher engine throttle settings. If the pilot continues to fight the plane, the rotor (which is flexible) can slow down due to the lack of positive G force, and can flop down and strike the spinning propeller, which destroys both and sends the autogyro into an uncontrolled fall. The way to avoid this during an incipient PIO is to apply gentle back pressure on the stick (to raise the nose in pitch) and cut engine power. Note that this is the exact opposite of what fixed-wing pilots are trained to do when in trouble, which has led to some unfortunate accidents and the autogyro's undeserved reputation for being "dangerous."

Another danger is "bunting over" or a Power Push-Over (PPO). An autogyro's vertical airspeed (climb or sink rate) is directly coupled to airspeed. Increase forward airspeed, increase rate of climb. In order to maintain level flight at high engine throttle settings, the pilot must tilt the rotor forward to prevent climbing and maintain level flight. The rotor thus becomes more nearly horizontal, and the control stick becomes more sensitive.

Too much forward stick, and the autogyro's rotor can aim down towards the ground. When this happens, negative-gees occur, rotor speed drops too low to provide lift, and a high-thrust line autogyro is then pitched forward by the propeller thrust and tumbles end-over-end in a somersault. It is virtually impossible to regain control after a full PPO.

Two factors can lead to pitch instability: no or too small horizontal stabilizers (h-stabs) on too short a tail and high thrust line propeller placement which destabilises the force diagram. A large h-stab, ideally in the prop wash (where the propeller blows on it) will reduce the tendency of an autogyro to bunt over as a result of improper control input by damping the control response.

If the propeller thrust line in an autogyro is high -- meaning the axis of propeller power is above the centre of gravity for the aircraft -- the autogyro tends to pitch forward under sudden power application (see PPOs above, as for why this is Bad). (Unfortunately, Bensen-type autogyros have a notably high thrust line.) If the thrust line is low, the autogyro tends to pitch up under sudden power application, which is harmless. It's difficult to have a low thrust line without a really tall autogyro (such as a "Dominator" style) however, so most autogyro designs simply try to get the thrust line as low as possible though still being slightly above the centre of gravity.

In spite of these dangers, most autogyros are designed to reduce them. Also, the majority of autogyro pilot training involves avoidance of PIO and PPOs.

Autogyro rotors usually feature a teeter-hinge in the middle. Picture a autogyro or helicopter from above, rotor spinning clockwise. If the aircraft is flying forward, the rotor tips on the left are travelling faster than the aircraft, while those on the right are actually going backwards relative to the craft. If the rotor blades were fixed, this would produce uneven lift -- more lift on the left side, since those blades are travelling faster. The teeter hinge on each blade lets it "flap" up and down. As the blade swings on the left, the increased speed makes it flap up with a greater angle of attack to the relative wind. This increases drag and reduces lift. As it swings to the right, it's now going slower, relative to forward speed. This reduced drag lets it flap down and get a better bite into the air, increasing lift.

Pitch is controlled by a conventional joystick coupled to the rotor. Pulling back on the stick tilts the rotor back, increasing lift and decreasing forward airspeed. Pushing forward on the stick decreases lift and increases airspeed, as long as it is not pushed much beyond horizontal (see PPO above). The plane's direction is controlled by rudder pedals.
The autogyro has a very unique way of flying, setting it apart from both the airplane and the helicopter.  The differences mainly come from the utilization of different basic principles to provide lift for the aircraft, and to propel them forward.

The Gyroplane Flight Manual
By Paul Bergen Abbott

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