Wind tunnel experiments on a model autogyro at small angles of incidence

Abstract

A wooden scale model, 6 feet in diameter, of the original 4-bladed rotating wing unit of the Cierva Autogyro, has been tested in the Duplex tunnel at blade angles of 0°, 1°, 1.8°, 2.30° and 3°. It has also been tested as a 2-blader at a blade angle of 1·8°. The extreme range of incidence was from 2° to 20° and of rotational speed from 3 to 12 revolutions per second. It was found that the model would not rotate at all at a blade angle of 4° while at 3° blade angle it would only rotate at angles of incidence above 12°. In order to supplement the measurement of forces and rotational speed at zero torque, observations of forces and angular accelerations were made over a more limited range at varying rotational speed, by means of a chronograph and stroboscope. These observations were interpreted as giving the forces and torque in steady motion when the torque was not zero. Observations were also made of the angular motion of the blades in flapping about their hinges.(Scan courtesy of Juergen Humt.)