TRADITIONAL helicopters have a vertical tail rotor to stop the main rotor
from spinning the craft endlessly round and round. But running that second rotor
wastes around 8 per cent of the chopper’s fuel, says Vladimir Savov, an expert
in aerodynamics at the Bulgarian Air Force Academy in Sofia. So to save that
fuel, Savov has invented the “rotopter”, a helicopter that flaps its rotors.
Helicopters can already fly without tail rotors—using counter-rotating
main rotors or elaborate fans on the tail boom—but Savov has taken a
different tack that he says will be far cheaper. To fight the…
