When's the last time you caught a ride in an autogiro?
- By T.A. Heppenheimer
- Air & Space magazine, March 2003
(Page 4 of 5)
Little has been done in the past 40 years to resurrect the always-intriguing concept. The reason: A winged car is too heavy to be a good airplane.
During the heyday of the autogiro in the early ’30s, Gerald Herrick invented an aircraft that fused elements found in autogiros with those found in conventional airplanes. The Vertaplane employed a two-blade rotor: It could be left to spin freely in order to dramatically shorten takeoff rolls, or it could be locked into place before takeoff to form a second wing. Fixed as an additional wing, the rotor effectively converted the aircraft to a biplane, which was faster than an autogiro. Once in flight, the rotor could be unlocked to allow the aircraft to land vertically (the rotor could not be stopped and locked in mid-air).
Initial flight tests were promising, but the aircraft suffered from excessive drag and was too underpowered to lift more than a single pilot and a small amount of fuel. When a lack of funding ended further research and development, Herrick’s aeronautical oddball was put out of its misery.
Convertiplanes reappeared during the l950s, this time as hybrids trying to combine the speed of fixed-wing aircraft and the vertical capabilities of rotary wings. The McDonnell XV-l of l954 took the shape of a helicopter with wings, using a single engine to drive both the rotor and a pusher propeller. It topped speeds of 200 mph, but by 1957, when the Pentagon ended its development, it was clear that helicopters would soon be capable of such speeds. Three companies followed with new designs. The Hiller X-18 mounted engines on a tilting wing; the Curtiss Wright X-19 used tilting rotors. Both were flat failures. The Bell Textron V-22 has been flying for over a decade, but on the question of whether the tilt-rotor is a viable design, the jury’s still out.
Ramjet- andRocket-Powered Aircraft
Aviation entered World War II with a single practical powerplant, the reciprocating piston engine, and emerged with three new ones: the turbojet, ramjet, and rocket. All three promised speed, but only the fittest would survive.
During World War II, Germany developed a rocket-powered interceptor, the Messerschmitt Me 163. Radar systems of that era lacked the range to give enough warning for propellerdriven airplanes, which took precious time struggling up to the altitudes where bombers flew. The Me 163 was capable of an ultra-quick ascent (it could reach nearly 40,000 feet in just three and a half minutes), but it ran out of fuel only minutes after takeoff, had a tough time targeting much slower bombers, and was vulnerable during descent, when it was unpowered. The Luftwaffe chose to place its bets on turbojet Me 262 fighters instead.
In the late 1940s, Republic Aviation designed the awkward-looking XF-91 Thunderceptor for the newly formed U.S. Air Force. It used rockets for an extra boost into combat, but could carry only enough fuel for a 25-minute flight. As did the Luftwaffe before it, the Air Force found solace in the wings of another turbojet—this time the F–l04 Starfighter. Turbojets triumphed because they used oxygen from the air to burn their fuel; rockets had to carry their own supply of liquid oxidizer—a fundamental disadvantage that could not compensate for the higher speed.
The ramjet had better luck. Invented by Frenchman Rene Lorin in 1913, it dispensed with the turbine’s rapidly spinning blades and instead used the force of air rushing in through its carefully shaped intake to compress air for combustion. It could function, therefore, only after being accelerated by another form of propulsion to very high speeds.