What does it take for a quadcopter to carry a 10-kg (22-lb) payload and fly for three hours straight? It takes petrol power – and a clever variable pitch rotor system that makes this gas-powered drone ...

Barring the smallest manned airplanes, most aircraft that are pulled around by a prop have variable pitch propellers. The reason for this is simple efficiency. Internal combustion engines are most ...

Quadcopters tend to have very poor efficency because of their high disk loading. High disk loading– that is, how much weight each square meter of area swept by the propellers must carry–is almost ...