. The ratio between the part of a propeller disc that when viewed from the front is solid and the part that is just air. This ratio is measured by adding up the blade chords at a certain radius and dividing the sum by the circumference at that radius. The greater the solidity, the greater is the ability of the propeller to absorb the power. The solidity can be affected by either increasing the number of blades, as in contrarotating propellers, or increasing the chord of each blade, as is done with paddle blades.ii
. The ratio of the total blade area to the disc area of a helicopter engine. Solidity is the function of the blade's ability to absorb power from the engine and the potential to provide rotor thrust.