To the practical designer the cumulative knowledge on airscrews seems at present to be in an unsatisfactory state of disorder. He wants to get reasonably accurate estimates reasonably quickly, without taking the time to become a specialist.

Several airscrew theories exist, but they either give wrong answers or take too long to work out, or both.

The great mass of test data that have been accumulated is so confused in a tangle of variables that the practical designer is often forced to select a test report almost at random and use it as if it applied to his particular problem; usually it does not and the calculation is seriously in error.

The present study attempts to clarify airscrew practical knowledge by coordinating data in a form suitable for use in performance calculations. It embraces the whole body of test data, but places particular reliance upon large scale wind tunnel results.

The arrangement of the analysis is such as to permit quick estimates to be made, the degree of accuracy obtained being a function of the amount of time available to the calculator. It is also designed to be as foolproof as possible so that it may be readily applied by inexperienced calculators.

It is especially adapted to calculations of the performance of aluminium alloy variable pitch airscrews.

One of the points brought out in the paper is the need for more data on certain subjects. They are specifically designated, and suggestions are made for carrying out research.