Low and High Speed Propellers for General Aviation — Performance Potential and Recent Wind Tunnel Test Results

Research sponsored by NASA has indicated that there is a significant potential for fuel savings from advanced propellers designed for lower speed general aviation (G.A.) aircraft as well as the advanced turboprop for future higher speed (Mach 0.6 to 0.8) aircraft. Lower speed G.A. propellers tested in the Lewis 10×10 foot wind tunnel had variations in the level of airfoil technology and activity factor. At cruise, the measured performance was about 4 to 5% below the predicted levels. A large part of this difference appears to be from inadequate modeling of blade and spinner losses with round shank blade designs. Blade cuffs and shaping of the spinner/blade juncture should offer the potential of recovering most of these losses, and combined with various advanced concepts may result in a 10 to 15% reduction in trip fuel for future lower speed G.A. aircraft. Advanced aerodynamic concepts for high cruise speeds were evaluated in the Lewis 8×6 foot wind tunnel. Results from these tests show high propeller performance can be obtained to at least Mach 0.8, offering the potential of reducing trip fuel by 15 to 30% compared to equivalent technology high bypass ratio turbofans.