From Kestrel to Harrier - Harrier development

Despite the good results of the trials, at the time there was little prospect of fielding the P.1127. Along with the British government's muddled attitude about new aircraft, the P.1127 also had competition.

Even as the Hawker VTOL aircraft was taking shape, Rolls Royce and Dassault had been internationally promoting a VTOL version of the Dassault Mirage III fighter, using Rolls Royce liftjets engines for vertical take-off. This concept would emerge as the Mirage IIIV (read as "three-vee" for "VTOL", not "three-five") experimental fighter, with a conventional turbojet for forward flight and eight Rolls RB.162 liftjets. The result of all this activity was the evolution of the "NATO Basic Military Requirement 3 (NBMR-3)" in 1959 and 1960 for a Mach 2 VTOL fighter, with a number of different manufacturers developing proposals. The whole NBMR-3 farce is discussed in more detail in the next section.

Tripartite Evaluation Squadron & Kestrel

One of its implications, however, was that the firmly subsonic P.1127 began to look like a dead end. There were those in the RAF and the British Air Ministry who tried to promote the P.1127 as the basis for a combat aircraft, reasoning, as it would turn out with complete sensibility, that an existing machine that worked was probably a better starting point than a far superior machine that existed only on paper. In fact, the Air Ministry had released "General Operational Requirement 345" in March 1960, defining a P.1127-based strike fighter. However, they were a minority, and military aviation in the UK was in a state of complete chaos at the time.

At that point, the MWDP came to the rescue once more. The British Minister of Aviation, Peter Thorneycroft, had discussions with the Germans on cooperative development of a combat aircraft based on the P.1127, and on 14 January 1961 announced such a joint program. The MWDP had been scaling back their financial support of the P.1127 effort, since the organization was chartered to perform investigations and not development, but the idea of a multinational investigation of the possibilities of VTOL combat aircraft appealed to some MWDP and senior US military officers.

One of the MWDP civilian staff, a very wealthy American named Larry Levy, lobbied hard to interest the British, West German, and American governments into funding a joint effort to investigate the military potential of the P.1127. The result was the "Tripartite Evaluation Squadron (TES)". Hawker was given an "Instruction to Proceed" on the construction of new aircraft for the TES on 22 May 1962, but the company asked for a delay, since their current round of testing was suggesting new features that would result in a much better aircraft.

The "Tripartite Agreement" that formally created the TES was signed on 16 January 1963, with manufacture of the new aircraft beginning that summer. Although 18 aircraft were originally planned, the British had the total cut down to nine. The aircraft were originally named the "P.1127-Evaluation", but in September 1964 they were redesignated the "Kestrel F(GA) Mark 1", where "F(GA)" stood for "Fighter (Ground Attack)".

The first had already flown on 7 March 1964. They featured all the improvements that had been devised during the P.1127 test program, and were also all initially fitted with the Pegasus 5 engine. They featured a new wing with a different configuration and slightly greater area that had been fitted to one P.1127 late in the test program; a short fuselage stretch; twin strakes fitted to the belly of the aircraft; a stores pylon under each wing for a drop tank; and a rear landing-gear door stressed for use as an airbrake.

The Kestrels originally featured the inflatable inlet lips, but this feature was quickly abandoned. They had no built-in armament, though practice bombs were carried on the wing pylons on occasions, and a nose camera was fitted to help evaluation simulated attacks and to perform experimental reconnaissance flights.

The TES was formally set up on 15 October 1964 in the UK, under the command of Wing Commander D. McL. Scrimgeour, with pilots from the RAF, Luftwaffe, USAF, US Navy, and US Army performing flight tests. The US Marines were interested, but did not participate. The Kestrels sported a "TES" insignia that combined USAF and Luftwaffe insignia with the RAF roundel like a pie with three slices. Wing Commander Scrimgeour was assisted by two deputies, one from the US Navy and the other from the West German Luftwaffe. The deputy from the Luftwaffe was Oberst Gerhardt Barkhorn, one of Germany's top aces, with 301 kills to his credit.

The TES performed 938 test flights from April 1964 through November 1965, flying the nine Kestrels plus the last P.1127, XP984, which had been fitted with the Kestrel-like wing. They performed flights from a variety of sites and performed exercises in remote deployments, defining the tactics to be used by VTOL combat aircraft and the logistical procedures needed to support them. One of the Kestrels was written off after a nasty ground loop when a US pilot tried to perform a rolling takeoff with the parking brake on, but the pilot escaped with little injury, and none of the other aircraft were lost during the test program.

The TES then went largely idle until April 1966, when it was broken up. Two the Kestrels stayed in Britain, while the other six survivors, including the West German aircraft, were purchased outright by the Americans at a pre-arranged "used" price and shipped across the Atlantic.

By the time the TES was disbanded, the British government had already decided to take the next step and make a true operational combat aircraft out of the Kestrel. As with everything else in the story, they did not come to this decision by any straightforward path.

Kestrel US trials

In US service, the six Kestrels were originally designated "VZ-12", but this designation was quickly changed to "XV-6A". They were used for extensive tri-service flight trials, in competition with two other VTOL aircraft prototypes, the Lockheed "XV-4 Hummingbird" and the "Ryan XV-6 Vertifan". After the trials, the US military services decided they had no need for such an aircraft, though that wasn't the end of the story by any means. NASA conducted extended trials with two of the Kestrels after the service trials; one of the NASA Kestrels later ended up in the hands of the Smithsonian Air & Space Museum in Washington DC.

Hawker P.1154 - the birth of the Harrier

While Hawker and Bristol were working to get the P.1127 and then the Kestrel flying, they were also playing with concepts for an operational VTOL combat aircraft. One interesting early concept put forward in the summer of 1958, the Hawker "P.1132", looked something like a bigger P.1127 / Kestrel with a wider wing. The outriggers were mounted in mid-wing, with the wings folding up beyond that point, presumably for carrier stowage. Given the limited thrust expectations for the Pegasus at the time, the P.1132 had twin side-by-side engines, one with two rotating exhausts on the right, the other with two rotating exhausts on the left.

With the emergence of the NATO NBMR-3 requirement for a Mach 2 VTOL fighter, Hawker came forward with a new concept, the "P.1150", which looked like a stretched version of the P.1127. The P.1150 was an elegant machine with the sleek lines of a dolphin, like a jet fighter from Atlantis. It was to be powered by an advanced Pegasus variant with "plenum chamber burning (PCB)", similar to afterburning, except that the augmented combustion took place in the front nozzle pair.

NBMR-3 was finalized in March 1961, and Hawker submitted an improved concept, the "P.1154", which looked much like the P.1150 concept externally but had an entirely new engine, the Bristol-Siddeley "BS.100", with PCB and 147 kN (15,000 kgp / 33,000 lbf) thrust.

The P.1154 concept remains appealing even today, and in fact it won the NBMR-3 competition in April 1962 -- though it would be more accurate to say it "sort of" won the competition. The reality was that the French refused to accept the British aircraft, preferring their own Mirage-IIIV, and so the international collaboration for a supersonic VTOL fighter gradually bogged down and died. The French Mirage IIIV proved to be a non-starter, and the program was eventually killed in 1966. The additional burden of separate lift engines, as Syd Camm had forseen, made the design impractical for actual use, though the IIIV was one of the few supersonic VTOL aircraft flown in the 20th century.

For a time, however, the P.1154 remained alive and seemingly healthy. Both the RAF and the British Royal Navy (RN) found the concept very attractive. However, this joint interest turned out to be a curse in disguise, since the two services could not agree on a common configuration. They seemed determined to make sure that the "P.1154RAF" and the "P.1154RN" were as different as possible.

The Royal Navy finally pulled out of the program in 1964, deciding to buy US McDonnell Phantom fighters fitted with Rolls Royce Spey turbojets instead. Predictably, the P.1154 and the BS.100 were cancelled on 2 February 1965. However, the RAF still had an outstanding need for a new strike aircraft to replace the Hunter, and the government orders cancelling the P.1154 also included instructions for the development of a combat-capable version of the Kestrel, to be extensively redesigned and fitted with P.1154 avionics.

The result was the "P.1127RAF", which would become the "Harrier GR (Ground Attack / Reconnaissance) Mark 1", the first operational VTOL combat aircraft. A contract for six pre-series machines was issued on 17 February 1965, a little more than two weeks after the cancellation of the P.1154.

First-Generation Hawker Harrier and Sea Harrier

The Harrier emerged from the P.1127 / Kestrel by a complicated and more-or-less lucky sequence of events. The aircraft that resulted, though suffering from a number of limitations in performance, range, and warload, proved extremely useful, and became an important front-line asset for both the RAF and the US Marine Corps (USMC).

Another complicated and more-or-less lucky sequence of events led to the modification of the RAF Harrier for Royal Navy use as the "Sea Harrier", which proved critical to British victory in the Falklands War in 1982, and which was given major extensions in capability after the war. This chapter outlines the development and careers of the "first-generation Harriers".

The Hawker Harrier GR.1 / T.2

Hawker's John Fozzard was put in charge of the development of the Harrier GR.1. While the new aircraft was derived from the Kestrel and unmistakeably resembled it, in engineering terms the Harrier GR.1 was a complete redesign, with only about 7% of its engineering drawings identical to those used for the Kestrel. One of the two Kestrels retained by the UK was used for engine development flights.

Initial flight of the Harrier GR.1 was on 31 August 1966. Six preproduction aircraft were built, which were all used for test and evaluation and never entered operational service. The first production Harrier GR.1 was flown on 28 December 1967. It began its military career almost exactly a year later, on 1 January 1969, with the Harrier Conversion Team formed at Wittering, and was fielded with RAF Number 1 Squadron in October of that year in the attack role. Unfortunately, Sydney Camm had died on a golf course in 1966, and never saw the Harrier in operation.

The Harrier was a unique aircraft that offered capabilities and challenges no combat pilot had ever been given before, and so a two-seat conversion trainer version, the "Harrier T Mark 2", was ordered in 1967 in order to assist new pilots in adjusting to the type.

The GR.1 and T.2 establish a baseline configuration for later Harriers. Both aircraft were powered by the "Pegasus 6 Mark 101" engine, with 84.6 kN (8,620 kgp / 19,000 lbf) thrust. Water injection provided incremental thrust over the Kestrel's Pegasus 5. Very importantly, the Pegasus 6 was much more reliable than the Pegasus 5, with an operating time between overhauls of 300 hours, as opposed to only 50 hours for the Pegasus 5.

The general configuration of the Harrier was a directed evolution of that of the P.1127 and Kestrel. As noted, the Pegasus engine had to be placed at the center of gravity, and the wing had to be raised high to clear the four rotating exhausts, leading to the bicycle-style tandem landing gear. For low-speed flight, engine bleed air was routed to puffers in the nose, tail, and wingtips to allow maneuvering, and the forward fan and compressor spool in the Pegasus contra-rotated to nullify the effects of angular momentum that could make such maneuvers more difficult.

The Harrier had the big "elephant ears" intakes to feed the forward fan, with the cockpit squeezed in between them. There were eight small doors around each intake to allow greater air input when required. The big intake hid the four rotating exhaust nozzles from the airstream.

Although Hawker engineers had been puzzled on how to arrange the cockpit controls for VTOL flight when they first began work on the P.1127, their experiments resulted in a simple, logical, though not very convenient, scheme. The cockpit layout provided the pilot with three levers on his left, from farthest to nearest:

• Throttle.
• Short-takeoff (STO) limit-set lever -- more on this later.
• A nozzle angle lever.

Adjusting the nozzle angle lever moved the four nozzles in unison, directed by a yoke under the Pegasus engine and rotated via a chain drive by a motor operating off engine bleed air.

The GR.1's wing was entirely new. It was optimized for subsonic flight, with maximum rated speed of 1,185 KPH (736 MPH). The wing was small, in order to reduce buffeting in low-level operations, with an area of 18.67 square meters (201 square feet). The wing was built as a single piece and had to be removed for an engine change. Optional "ferry tips", each 69 centimeters (27.2 inches) long, could be attached to the wing tips to provide about a 9% increase in range, at the expense of speed. A midair refueling probe could also be bolted on to the left side of the aircraft, just behind the intake, for ferry flights. The tail was conventional, similar to that of the Hawker Hunter, but included a small ventral fin, with a bumper to protect the aircraft from a rough landing. The pop-up ram-air turbine emergency power generator system in front of the tail that had been introduced with the P.1127 was retained.

The flight control system was based on a traditional wheel-and-pulley scheme, with an interesting variation in that the tail (yaw) and wingtip (roll) thrusters for hovering flight were slaved to the appropriate control surfaces. There was also a pitch thruster in the nose. The pilot controlled the thrusters in exactly the same way that he controlled the normal flight control surfaces. The thrusters were activated when the nozzles were moved 20 degrees down from the horizontal, and were driven by engine bleed pressure of up to about 12 atmospheres at 400 degrees Celsius, resulting in a thruster exhaust velocity of over 2,700 KPH (1,680 MPH)!

The GR.1's cockpit was somewhat cramped and squeezed between the two big intakes, resulting in terrible rearward visibility. It was also said to be very noisy, pilots claiming it seemed the engine was actually in the cockpit with them.

The GR.1's flight avionics were simple, consisting of:

• A Ferranti FE541 inertial-navigation / attack system that featured a moving-map display of the aircraft's current position. This was one of the pieces of gear that had been originally developed for the P.1154.
• A tactical air navigation (TACAN) beacon-navigation system and gyrocompass.
• A head-up display (HUD).
• Identification friend or foe (IFF) transponder.
• HF/VHF/UHF radios.

No radar was fitted, it being judged unnecessary for the daylight close air support role. The GR.1 also had an interesting feature useful for low-speed hovering flight: a little "weathervane" in front of the canopy that served as a yaw sensor. The windscreen was "hardened" to resist birdstrikes, a serious problem in low-level operations. The windscreen could withstand the impact of a 4.5 kilogram (11 pound) bird at an impact velocity of 1,100 KPH (680 MPH).

The GR.1 was fitted with a Martin Baker Mark 9 rocket-boosted zero-zero (zero speed, zero altitude) ejection seat. Instead of blasting off the canopy, the GR.1 had a string of "miniature detonating cord (MDC)" ribboned around the top of the canopy. Before ejecting, the detcord would blast the top of the canopy into fragments, and the pilot would eject through the hole. Although this is a fairly common measure now, the Harrier was one of the first aircraft to incorporate the scheme because, in hovering mode, blasting off the canopy would have thrown it straight up, and the ejecting pilot couldn't have missed it.

The GR.1 had five stores pylons, one under the fuselage and two under each wing. Typical external warload was about 2,270 kilograms (5,000 pounds) and could include:

• Bombs, for example two 500 kilogram (1,100 pound) retarded bombs or four Hunting Engineering BL755 cluster bombs.
• Unguided rocket packs. The Matra 155 18-round pod for the SNEB 68-millimeter (2.7 inch) unguided rocket was a preferred munition for the GR.1.
• Two 455 liter (100 Imperial gallon / 120 US gallon) external tanks, carried on the inboard wing pylons only, as the outboard pylons didn't have the plumbing.
• A five-camera reconnaissance pod, carried on the center pylon. The pod contained one forward-facing camera, and a "fan" of four cameras to give a horizon-to-horizon panoramic view under and to the sides of the aircraft.

The GR.1 did not have any built-in guns, but two Aden Mark 4 30-millimeter revolver-type cannon pods could be attached to the belly. Each cannon carried 100 rounds and had a rate of fire of about 1,200 rounds per minute. The gun pods also helped improve hovering characteristics by trapping backblast when in ground effect; and reduced exhaust-to-intake gas ingestion problems, a common difficulty with VTOL jets. When the pods were removed, a pair of "strakes" were installed in their place to maintain hovering flight characteristics.

The first of two T.2 prototypes performed its initial flight in 1969. The T.2 featured a stretched fuselage to accommodate the two seats in a tandem fashion. The stepped-up canopy was hinged on the side, not backwards-sliding as with the GR.1, and the back seat was stepped up to give the instructor excellent forward visibility. To compensate for the extended nose the tail was also extended, and both the tailfin and ventral fins were increased in size. The T.2 was completely combat-operational, capable of carrying a full load of fuel and weapons.

The Harrier was not really a VTOL aircraft. A GR.1 could not take off vertically with a full combat load. In practice, the nozzles were angled down to about 55 degrees lever, and the aircraft would blast off after an astonishingly short takeoff run. It would be more appropriate to call the machine a "short take-off / vertical landing (STOVL)" aircraft.

Actually, although landings could be performed vertically if stores had been expended, Harrier pilots often preferred a short landing roll. This was a useful practice in field environments since it avoided sucking dust and debris into the engine. On a rolling landing, the nozzles could be pointed 8.5 degrees forward of vertical to reduce landing roll. This also allowed the aircraft to be flown backward, though this was almost never done as anything but an airshow stunt.

Pilots found the aircraft generally straightforward to fly once in normal flight, but takeoffs and landings could be tricky and dangerous. Having to deal with the stick, throttle, and nozzle angle lever required "three hands", increasing pilot workload on takeoffs when the workload is maximized in the first place. The first person killed in Harrier, USAF Major Charles R. Roberg, died in 1970 when he tried to turn during the transition period and went out of control. There would be a fairly large attrition among Harriers in operation, but this would also be due to the demanding nature of low-level operations. The Harrier is not regarded as "bad" aircraft, just a "unique" one because of its unique capabilities, and is generally flown by the most experienced pilots who are given extensive training to convert to the type.

Combat radius of the GR.1 was about 370 kilometers. This was only about half the range of a Jaguar strike fighter but was regarded as acceptable, since the aircraft was intended to be based near forward combat areas to provide quick-response strikes.

A total of 61 GR.1s and 10 T.2s was built, not counting the two T.2 prototypes and a single "Mark 52" two-seat Harrier, which had the tailcode "G-VTOL" and was retained by Hawker Siddeley for test purposes.

The Harrier GR.1A, T.2A, GR.3, & Harrier T.4

Further tweaking of the Pegasus engine resulted, in 1969, in the "Pegasus 10 Mark 102", with 9,300 kilograms (20,500 pounds) thrust, as compared with the 8,620 kilograms (19,000 pounds) thrust of the Pegasus 6 Mark 101. Harriers produced with the new engine were "GR.1As", with 17 built, and "T.2As", with four built. Surviving GR.1s and T.2s were also updated to the GR.1A and T2.A specification.

Pegasus development didn't stop there. The next major revision was the definitive "Pegasus 11 Mark 103", which provided 95.6 kN (9,750 kgp / 21,500 lbf) thrust with a modified fan, combustion chamber, fuel control system, and higher operating temperature. A new Pegasus variant led to a new Harrier variant, the "GR.3", which also incorporated some avionics upgrades. There was also a corresponding trainer version, the "T.4". A total of 40 GR.3s new-build GR.3s were manufactured, as well as 11 T.4s.

The most visible change to the GR.3 relative to the GR.1 was the addition of an elongated nose "thimble", to house a Ferranti 106 "laser ranger and marked target seeker (LRMTS)". This instrument could either be locked onto a target to provide continuous updates on position and rate of closure via laser radar, with the result displayed on the cockpit HUD; or could be used as what is now known as a "laser spot tracker", locking onto a target being illuminated by ground troops or whoever with a laser target designator.

The LRMTS gave the GR.3 a "Pinnochio nose", or as the RAF called it, a "Snoopy nose", appearance, after the famous long-nosed beagle in the popular American PEANUTS comic strip. The nose did not affect the aircraft's flight characteristics and so no aerodynamic modifications were necessary. The LRMTS was also refitted to older GR.1As still in service. In addition, the GR.3s were fitted with a camera shooting out the left side to give them a basic reconnaissance capability. Another visible change was a Marconi ARI-18223 radar warning receiver (RWR), whose forward aerial appeared as a tab breaking up the smooth curve of the tailfin. The rearward aerial was placed less obtrusively on the tailcone.

The new avionics demanded more electrical power, and so the twin 4 kVA alternators of earlier Harriers were replaced by a single 12 kVA alternator.

The T.4 featured similar kit, including the LRMTS.

The Royal Navy Sea Harrier FRS.1

The Royal Navy's waffling on the P.1154 quickly came back to haunt the service. In 1966, the British Labour government decided to give the axe to all of Her Majesty's fleet carriers. The Phantoms on which much money had been lavished now could only operate off of land bases. However, in 1968 the government decided that helicopter carriers were still affordable and useful, though they were given the entirely baffling name of "through-deck cruisers" for the sake of political correctness. Royal Navy jokers renamed them "see-through cruisers".

The Harrier was an obvious fit for such vessels. As noted, the P.1127 had operated off the deck of a carrier back in 1963, and during the 1960s and 1970s Harriers were flown without difficulty off a number of vessels, some of them very small. The desireability of a naval Harrier wasn't obvious to everyone, however; there was still the prejudice that Mach 2 was an absolute necessity, and the Harrier was only supersonic in a dive. Still, half a loaf was better than none, and in August 1972, after fanatical lobbying by concerned Royal Navy air staff to overcome a seemingly endless series of bureaucratic obstacles, development was begun on a naval Harrier, to be derived in as minimal a fashion as possible from the GR.3, for operation off light carriers.

After further near-brushes with death, the first "P.1184 / Sea Harrier Fighter-Reconnaissance-Strike Mark 1 (FRS.1)" flew on 20 August 1978. It was very similar to a GR.3 from the air intakes back, but the cockpit and nose were largely redesigned.

The Sea Harrier, as its "FRS" designation implied, was intended to be a multirole aircraft, suited for air combat, with the capability of carrying a Sidewinder on each outer wing pylon, as well as for attack and reconnaissance. Since its primary target was expected to be Soviet Bear-class turboprop reconnaissance and missile-attack aircraft, the Sea Harrier's subsonic speed was not regarded as a major limitation.

The mission did, however, require that an air-intercept radar be added, and the Ferranti "Blue Fox" radar was selected. The Blue Fox was a derivative of the "Sea Spray" radar developed for navalized Westland Lynx helicopters, and had four operational modes, including "Search", "Air-To-Air Attack", "Air-To-Surface Attack", and "Boresight". It was relatively simple compared to other contemporary fighter-aircraft radars, in particular lacking a look-down capability, but it was compact, light, affordable, and met mission requirements.

A new nav-attack kit was fitted as well, consisting of a Ferranti attitude reference and heading system, linked to a Decca 72 Doppler radar. The new system was provided because the Ferranti FE541 system used on the RAF Harriers had to be aligned while the aircraft was dead motionless on the ground, a difficult condition to achieve on an aircraft carrier on the open sea.

The pilot needed more display area on the control panel to deal with the new avionics. This demanded that the cockpit be raised 28 centimeters (11 inches). Raising the cockpit also fixed one of the major disadvantages of the GR.3 in air combat: the poor rearward and sideways view for the pilot. The Sea Harrier's canopy was also bulged to improve the view forward and downward. The height of the tailfin was increased by 10 centimeters (4 inches) to compensate aerodynamically for the raised cockpit.

An improved autopilot was added to help the pilot deal with the increased workload. With all the new avionics, the cockpit of the Sea Harrier was an entire redesign of that of the GR.3. A new Martin-Baker Mark 10H zero-zero ejection seat was also added. Other minor changes were made:

• A navalized Pegasus 104 engine was fitted, with components made of corrosion-resistant alloys to replace those made of easily-corroded magnesium.
• Larger wingtip reaction control valves were installed, to allow the aircraft to deal with turbulence caused by the carrier superstructure.
• Deck tie-down lugs were fitted to the nose gear leg.
• The oblique camera was moved from the left to the right side of the aircraft.

For training, the Royal Navy initially obtained a single new-build T.4A, calling it a "T.4AN", and later obtained seven hand-me-down T.4As from the RAF, also redesignating them T.4ANs. The navy then acquired three new-build "T-4Ns", which were minor navalized modifications of the standard T.4, with the Pegasus 104 engine and a basic subset of FRS.1 avionics. Since the T.4Ns in particular lacked the Blue Fox radar of the FRS.1, the Royal Navy also obtained three Hawker Hunter T.8Ms fitted with the Blue Fox as radar trainers. Two of the Hunter T.8Ms had been used in development of the radar.

The T.4N was combat-capable, but was too long to fit on the elevators on British carriers and could not be stowed below deck. The FRS.1 itself would fit on an elevator if its nose was folded back.

The first production FRS.1 was handed over to Royal Navy service in mid-June 1979. The Sea Harrier was a welcome arrival for the Royal Navy's combat aircraft pilots, since the RN's last fixed-wing combat aircraft, the BAE Buccaneer and their Spey-powered Phantoms, had been retired the previous December.

The Sea Harriers, or "Shars" as they were sometimes called, were slated for operations off the three "command cruisers" (as the "through-deck cruisers" had been renamed) HMS INVINCIBLE, ILLUSTRIOUS, and ARK ROYAL, the last of which was in planning at the time, with a normal complement of six Sea Harriers along with helicopters.

The "Ski Jump" takeoff ramp

Carrier operation of the Sea Harrier was greatly enhanced by an elegantly simple idea, devised by Royal Navy Lieutenant Commander Douglas Taylor: the ski-jump takeoff ramp.

Taylor calculated that simply modifying the deck so that it curved up at the end would throw the fighter up into the air, allowing it to carry more warload with a shorter takeoff run, as well as give a Royal Navy pilot more time to eject if it became apparent his aircraft was going to splash. Taylor proposed the idea in early 1970s, but it wasn't until 1976 that Hawker received funding to perform land-based tests of the ski jump takeoff. The tests clearly demonstrated the effectiveness of the concept.

Resistance to the ski jump concept was so stubborn in some quarters that advocates of the idea collectively referred to the critics as the "Flat Deck Preservation Society". The advocates prevailed, and the ski jump was adopted for carrier operations. Ski jump takeoffs are apparently very spectacular to watch, though pilots describe them as "cake".

The HMS INVINCIBLE and ILLUSTRIOUS were both originally fitted with a 7-degree ski jump, while the ARK ROYAL featured a 12-degree ski jump when it was commissioned in 1985. Both the INVINCIBLE and ILLUSTRIOUS were later refitted with a 13-degree ramp. The Spanish light carrier DEDALO was not fitted with a ski jump, but the modern Spanish PRINCIPE DE ASTURIAS and Thai CHAKRI NARUEBET both have 12-degree ski jumps.

In the spring of 1977, Hawker Siddeley was absorbed into the initially nationalized British Aerospace (BAE) group, and the "Hawker Siddeley Harrier " then became the "BAE Harrier".

US Marine Corps Harrier AV-8A

Although the US Marine Corps had a strong interest in VTOL aircraft, as noted, the USMC did not participate in the Tripartite Evaluation Squadron. However, when the US took ownership of six Kestrels from the TES, some of them also ended up at the Naval Air Test Center at Patuxent River, Maryland, where the Marines performed flight evaluations with them. In April 1966, the Marines operated a Kestrel off the commando assault ship RALEIGH and were impressed with the aircraft. Nonetheless, the Kestrel had no combat capability and was useless to the Marines as it was, and there matters stood until the Farnborough Air Show in the UK in September 1968.

Three USMC officers dropped into the Hawker Siddeley chalet at Farnborough and asked to fly the Harrier. The three were given ten flights each, and felt the Harrier was what they were looking for. What the Marines required was a strike aircraft that could support landing forces. Fleet carriers had to be kept well at sea for their own safety, but Harriers could fly from smaller assault ships just offshore, or from rough landing sites behind the battle lines, to provide quick-response strikes for ground troops.

The main obstacle was that the Harrier was a British machine, and the US armed forces have a strong preference to "buy American". The solution was for Hawker Siddeley to license the aircraft to McDonnell Douglas (MDD) for sale to the USMC "AV-8A". Rolls Royce, which had bought out Bristol in the interim, similarly made an arrangement to allow Pratt & Whitney (P&W) to build the Pegasus under license, which then became a P&W "F402-RR". These collaborations were to be crucial to the future of the Harrier.

In practice, although the original agreement envisioned that MDD would actually build Harriers themselves, none of the AV-8As, or "Mark 50 Harriers" as Hawker designated them, were actually made in the US, since opening a second assembly line proved uneconomical. They were built in the UK, shipped as airfreight overseas, and delivered by MDD. It is unclear if MDD fitted the aircraft with USMC avionics. The first few AV-8As used the Pegasus 10, but all following production used the Pegasus 11.

102 AV-8As and 8 "TAV-8A" or "Mark 54" trainers, generally similar to a Harrier T.4 but with different avionics fit to match that of the AV-8A, were built in the early 1970s, giving the USMC a potent STOVL strike capability. The first combat squadron was formed up in 1971. Marine Harriers operated off fleet carriers, helicopter assault ships, and any other convenient vessel.

The USMC Harrier was externally identical to the Harrier GR.1. The Martin Baker ejection seat was replaced by a US-made Stencel SIIIS-3 seat, and US-built IFF and radio gear were incorporated. A Smiths Industries HUD and a multimode weapons aiming system replaced the British equivalents. The AV-8As were also cleared to carry a pair of large 1,135 liter (300 US gallon) drop tanks.

Originally, the Marines had wanted to replace the 30 millimeter Aden cannon pods, but they were retained, even though no other Marine weapons used their ammunition. It appears that the USMC did not want to escalate costs by re-specifying a new cannon, and believed the Aden cannon could do the job. The Marines did of course qualify US-made stores, such as 70 millimeter (2.75 inch) or 12.7 millimeter (5 inch / Zuni) rocket pods and Rockeye cluster bombs. The outer stores pylons, were wired to carry Sidewinder air-to-air missiles (AAMs) for self-defense, an innovation that would later prove significant.

The USMC's provision for Sidewinder missiles on the AV-8A led the service to devise an interesting new dogfighting tactic, named, somewhat stiffly, "vectoring in forward flight (VIFF)". Experiments performed by the USMC with VIFF demonstrated that it had some extraordinary qualities. The Marine pilot who performed the first evaluations on VIFF in 1970, Captain Harry Blot, fully reversed the nozzles while flying at high speed on his first test flight. He reported that he "decelerated rapidly" -- but he could not determine just how rapidly, since he was wrapped around the stick with his nose stuck on the gunsight.

Although the Harrier with its short wings has a poor turning radius, VIFF gives it some unusual maneuvering options, allowing it to perform strong banking turns and quick braking to allow a pursuer to overshoot. There has been a lively debate over the merits of VIFF. It is clearly not a miraculous tactic, but the Marines were so impressed with it that they requested, and got, changes to the Pegasus engine to support it. The changes included strengthened nozzles, an uprated nozzle drive motor, and a capability to redline the engine for 2.5 minutes. The Marines established VIFF as an operational doctrine.

Author: Greg Goebel