Static and dynamic coefficients of a cross-type parachute

A parametric investigation of the aerodynamic characteristics of a group of cross-type parachutes is described. The investigation includes the measurements of the static and dynamic aerodynamic coefficients, utilizing a measuring system designed especially for this task. The validity of the measuring technique was established by comparing the results to previous data. The static aerodynamic coefficients are presented as a function of the angle of attack and the parachute geometric parameters. Spin is introduced by staggering the length of the cords. The effects of the spin on the axial force, as well as on the stability parameters, are investigated with different parachute geometries. The measurements show an increase of up to 50% in the axial force due to the spin, followed by a decrease in the longitudinal stability, which explains the tendency for this type of parachute to undergo a conning motion during descent flight. The apparatus supplies a unique means to measure the maximum obtainable roll rate and the maximum torque the cords can transfer before collapsing.