The History of VTOL

Early designs for vertical takeoff air­planes in the 1940s and 1950s tried a type of aircraft called a tail-sitter. The plane sat on the ground on its tail, with its nose pointing straight up in the air. It looked like a rocket with wings. Its propellers lifted it up off the ground. Once the plane was airborne, it slowly tipped over and started to move forward. As it accelerated, its wings generated more and more lift until it was flying normally. The Lockheed XFV-1 and Convair XFY-1 Pogo were tail-sitters.

These planes were very difficult to land because the pilot was facing away from the ground. The tail-sitter design was eventually abandoned.

In the early 1950s, the British compa­ny Rolls-Royce produced two experi­mental, jet-powered, vertical takeoff air­craft called Thrust Measuring Rigs. They were made from a skeleton-like frame with two Rolls-Royce Nene jet engines. These aircraft were so successful that Rolls-Royce went on to develop a new jet engine, the RB108, specially for ver­tical takeoff aircraft.

Some experimental VTOL aircraft built in the 1950s and 1960s tilted their wings with the engines attached. These aircraft, including the Canadair CL-84, LTV-Hiller-Ryan XC-142, and also the Hiller X-18, are called tilt wings. The Vertol 76 VZ-2 also was a tilt wing but its engine was mounted in the center of the fuselage, and it drove two propellers on the wings. This layout meant that the wings and propellers could be tilted without having to tilt the heavy engine as well.

Other researchers, meanwhile, were experimenting with the use of separate engines for lift and forward thrust. The Short Brothers aircraft company in Belfast, Northern Ireland, carried out pioneering research in vertical takeoff in the 1950s. Their Short SC.1 was the first successful British fixed-wing VTOL air­craft. Looking a little like a housefly, it was powered by four Rolls-Royce RB108 jet engines for lift and a fifth RB108 engine for forward thrust.

About the time the early tail-sitting airplanes were being discontinued, the British Hawker company developed a flying test bed for new technologies. It was a vertical takeoff jet plane called the P1127. It was never meant to be an oper­ational aircraft, but it was developed into the most successful vertical takeoff aircraft of all: the Harrier.