It is an historical fact that the Rotol Airscrew Co was formed in the late 1930s specifically to manufacture variable pitch propellers. It would not be unnatural, therefore, to think that the development, in 1975, of a propeller for a crop spraying aircraft would be a routine matter for a company with nearly 40 years experience in the business. To some extent it was, but in other ways it proved to be an interesting and exciting challenge. Perhaps this was partly due to the fact that it was a new type and new types of aircraft or engine or major accessories are something special these days. But the main reason was that some fairly radical changes in design philosophy to those which the Company was accustomed were employed and these provided the major source of development activity.