A gyrocopter has a rotor that looks like a helicopter and a propeller for thrust. Every kid knows that a propeller is what moves an aircraft through the air. There are a variety of propellers available for gyroplanes. These propellers can be made of wood, metal, or of composite materials. There are also different types of propellers such as fixed pitch, ground adjustable, or constant speed.
Types of Gyrocopters
Early gyrocopters were the tractor-type. On this type of aircraft the engine and propeller were positioned in the front of the aircraft. They pulled the plane forward. Small wings added stability to the tractor-type gyrocopter.
Most modern gyrocopters today are pusher-type and have the engine and prop in the back of the place behind the pilot and they push instead of pull the plane foward.
What Makes a Propeller Work
The answer is its shape. The twist in the propeller blade is what makes the propeller produce thrust. When spinning, the part of the propeller blades closer to the center move slower than those at the tips creating lift. The twist in the blade is shallow at the tip and steep at the hub. This gives even thrust from one end the blade to the other. The amount of thrust created by a propeller depends on how fast it spins and at what angle its blades slice through the air.
The best working propeller is one that is rigid enough to allow all blades to move alike, thin at all cord sections to eliminate as much drag as possible, and strong enough to satisfy the large amounts of stress required during flight. Traditional propellers are made of wood but the newest high tech ones are made of composites.
Going Your Own Way
If you are making a gyrocopter from a kit, the manufacturer will probably recommend a propeller and an engine for your particular kit. If you use a different horsepower engine then you will need to adjust the propeller size and profile. There are stringent standards for propellers for a certain horsepower, rpm (revolutions per minute), and performance expectations of an aircraft.
Propellers bolt directly to the engine. Aircraft engines are designed for maximum power where the propeller will also turn at an efficient rpm. The auto engine turns at an rpm too high for most propellers. The solution is to use a reduction unit to make the auto engine usable on the aircraft. For example, a 2 to 1 reduction unit will change 4,000 rpm at the engine to 2,000 rpm at the propeller. Usually you can get a reduction unit from those who sell aircraft auto conversion engines.
Asking for Advice
If you decide not to stay with the propeller that the kit recommends then there is help available from propeller manufacturers or organizations such as the PRA (Popular Rotocraft Association). They can assist you in finding manufacturers who make propellers specifically for gyrocopters. A propeller is an important choice for a gyrocopter. Do your research and ask questions.