THOSE engaged on airscrew work are constantly making use of the tables of experimental values of kT and kQ for different values of J given in R.M. 1673. In using these tables it is usually necessary to extrapolate. It is the object of this article to show that, where we have strict grounds for comparison, we can construct a single thrust curve, which covers a wide range of pitch and conditions of working, and so obviate the need for extrapolation. The curve found covers the range of pitch p/p=0 to 1 and the working range below stall.