Not long after the jet engine had been invented, aircraft designers began to look for new ways to harness its thrust. The unprecedented combination of high power and light weight opened the way to VTOL (vertical take-off and landing) aircraft.

The concept of vectoring the thrust downwards dates from the late 1940s. By the late 1950s a spate of V/STOL (vertical or short take-off and landing) aircraft, many of them prop-driven were being test flown on both sides of the Atlantic.

Most of the early V/STOL schemes were ungainly and complex, some having batteries of special vertical turbojets used only at take-off and landing. A French engineer, Michel Wibault, proposed a VTOL scheme in which an engine drove giant air compressors delivering through pipes which could be vectored downwards, to lift the machine off the ground, or to the rear, for forward flight. At Bristol Dr Stanley Hooker and his engine designers simplified this into a much neater and more compact solution which eventually became the Bristol (now Rolls-Royce) Pegasus engine. A turbofan, it delivers fan air to left and right front nozzles and hot jet gas to left and right rear nozzles, all four nozzles rotating in unison. At Hawker Aircraft Sir Sydney Camm's designers created the P.1127 around this unique engine.

The prototype Hawker P. 1127 hovered for the first time on 21 October 1960. Five months later, it made its first proper flight. From this stemmed first a squadron of aircraft called Kestrels and then, from early 1969, regular PAF service by the production Harrier, a fully developed combat aircraft. Although these aroused considerable interest, much of this seemed to be idle curiosity rather than serious interest in the aircraft's potential for military use. This amused tolerance by the worlds air forces and aircraft makers continued for over 20 years.

Then, unexpectedly, the Harrier startled the world. In May, 1982 pilots of the British Royal Navy and RAF showed the world, and in particular the Argentinian air force and navy, just what a deadly weapon the Harrier can be. Helicopters apart, the Harrier was the only aircraft that Britain could deploy in its bid to liberate the Falkland Islands and their inhabitants. Its ability to take off from the tiny decks of Britain's two small carriers, HMS Hermes and Invincible, with no catapult or arrester gear, was of course fundamental. But what shocked the pilots of the Skyhawks, Mirages and Super Etendards was the little aeroplanes' staggering maneuverability.

Today there are several versions of the Harrier in service. The GR.3 close-support attack and reconnaissance model has the Pegasus 103, of 21 ,5001b thrust. Four squadrons of these are serving with the Royal Air Force. They carry two 30mm Aden cannon in detachable pods and five pylons can carry up to 50001b of bombs, rocket pods and Sidewinder self-defense missiles. The GR.3's avionics include a laser nose, inertial navigation and a HUD (head-up display).

Another main variant is the Sea Harrier. Basically the same as a GR.3, the Sea Harrier has a redesigned front end with the pilot placed at a higher level to allow room for further avionics and additional cockpit interfaces and controls. This also improves all-round visibility. In the nose is a Blue Fox radar, arranged to fold through I 800 to reduce length to fit small ship lifts and hangars. It was this aircraft, still hardly settled down in service, that was so spectacularly successful in the South Atlantic: it scored 23 air-combat victories, plus three probable's, over assorted Argentinian aircraft without suffering a single loss. Six Sea Harriers were lost, but these were either destroyed by ground fire (2) or lost in accidents (4), the latter all being caused by appalling weather conditions.

Although the Sea Harrier is perfectly capable of vertical take-off, it normally uses a ski-jump' take-off ramp to increase mission capability. On take-off the engine nozzles are all vectored rearwards at the beginning of the short but exciting run. As the Harrier reaches the end of the ramp, sloping at 70 to I 50 (depending on the installation), the nozzles are suddenly vectored 500 downwards, hurling the aircraft into the sky while still accelerating it horizontally. Weapon or fuel loads can be greatly increased, and safety on engine failure is also far better.

In 1982, a fascinating new ship borne launching method was announced, the Skyhook. Developed by BAe as a private venture, it would enable even small frigates and destroyers to carry a complement of Harriers without a traditional flight deck. Cranes on each side of the ship lift two aircraft into the air, then swing them outboard. At this point the engine is started; as soon as it is supporting the aircraft, the special 'grabs' release it. At the end of its mission, the Sea Harrier hovers alongside the ship. The Skyhook, which has an inbuilt sensor, is automatically positioned so that the 'grab' can clasp the aircraft. Then the crane swings it inboard and on to the deck or straight into the hold. As with the ski ramp, it takes a long time for navies to understand and accept new ideas.

Harriers are in service with Britain, the US Marines and the navies of India and Spain. Although not yet produced in anything like the numbers that its designers had every right to hope for, the Harrier has proved beyond doubt and in the most conclusive way possible that it is no gimmick. With incredible slowness the penny is gradually dropping: future combat aircraft dare not require airfields. The Harrier was simply the first of the warplanes of the future.