A method of blade construction employing CFRP in a basic load-carrying spar, GFRP outer shell of aerofoil form, has been developed. Full-scale blade specimens have been fatigue-tested in various models. Other tests, such as bird impact trials, have also been carried out. Complete propellers have been run on hovercraft and the blades have been straingauged; comparisons have been made between the measured vibratory strains and the fatigue test results. A propeller with such blades has been fitted to a craft maintaining a high frequency scheduled service, and has accumulated 1150 h operating time over a period of approximately 6 months. The only problems encountered concern the leading-edge erosion protection. By November 1973 the total hours accumulated exceeded 2,500.