Glossary
What is a gyroplane?
A rotorcraft whose rotor is turned by airflow rather than by the engine, with a separate propeller providing thrust. Regulators generally use "gyroplane"; autogyro and gyrocopter mean the same aircraft. Rotorcraft is the wider category and includes helicopters, so it is not a synonym.
Also called Gyrocopter, autogyro, gyro
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.