Recent reports contain tables of a parameter K required in calculating the performance of an airscrew by a new method.
The method of calculating K (due to Goldstein) is unsuitable for large values of the pitch especially near the tip of the airscrew.
In the case of infinite pitch we fall back, for a two-bladed airscrew, on the problem of a rotating lamina in two dimensions.
The solution for a cross lamina (corresponding to a four-bladed propeller) is given below and the tables of K for four blades are completed.
A formula for the limit of K/Kp at the airscrew tip is given for a propeller with any number of blades, where Kp is an approximate value of K due to Prandtl.
K for any number of blades is given in the form of an infinite series. The case of three blades is discussed in detail.