Turnbull's research was recognized early - he won a medal from the Royal Aeronautical Soc in 1909 - but his greatest achievement was the variable-pitch propeller, tested in flight in 1927. This device adjusts the angle at which propeller blades cut the air and it became as essential to aviation as the gearbox is to the automobile. It provides for safety and efficiency at all engine speeds, for example, maximum power on takeoff and landings and economical cruising for long distances. It was independently perfected in several countries, so that Turnbull's work has been overlooked by most historians, perhaps because he licensed its manufacture and went on with other inventions. But his variable-pitch propeller (now in the National Aviation Museum, Ottawa) appears to have been the first to fly successfully.
Author DONALD J.C. PHILLIPSON
Links to Other Sites
A profile of Wallace Turnbull from the Canadian Science and Engineering Hall of Fame.