Classic Aircraft profiled every issue -

Issue 11 - Harrier: The Trainers - The Harrier T.2 to T.12, and the TAV-8A and B

Ralph Hooper of Hawker Aircraft was a very busy man in 1966. Aside from overseeing the final design modifications to the six pre-production P.1127(RAF) aircraft, he was suddenly presented with a new development project which was to cause its own problems with regard to modifying the new airframe.

In June, 1966, the British Government had authorised a one-year study programme to examine the feasibility, and likely costs, of developing a two-seat trainer version of the Harrier as it was now officially named. The RAF was already making plans to develop a structured training course for the aircraft, which included a short helicopter course to introduce trainees to the reality of vertical flight. Even with this vertical training element, it was decided that the Harrier was so unusual that a two-seat trainer would be likely to reduce the training accident rate, not to mention be able to be pressed into service to supplement the combat fleet in the event of war.

To this end, Ralph Hooper turned his attention to the very difficult task of fitting a complete second cockpit, with all the attendant equipment, into a small airframe already completely full and close to its weight limits. To solve the weight problem, Hooper contacted Bristol Siddeley, which was already looking at increased thrust versions of the Pegasus which would satisfy the trainer’s needs. This settled, he began detail design work in order to accommodate the second cockpit.

Firstly, the nose was lengthened by 47 inches (1.2m) simply by moving the existing cockpit forward. In the space created, the second cockpit was added, but raised 18 inches (0.45m) for a number of reasons. Firstly, the instructor in the back would be able to see over the pupil’s head. That might sound elementary, but a number of jet training aircraft, such as the Folland Gnat and T-33, were in service where the instructor could see forward only by leaning to one side and looking down the spaces on either side of the pupil’s head and seat. Not a good way to fly, let alone teach someone else to fly!

Because the new cockpit was going to cause both a weight and an aerodynamic balance problem, the space under it was used to house equipment that had been in the extreme nose of the single seater, like the F.95 camera and some of the avionics. Moving these items aft lessened the balance problem but did not solve it.

To offset the increased nose weight, a new tailcone, 33 inches (0.84m) longer than the original, was added which contained around 180lb (81.6kg) of ballast. The entire fin was moved aft by 33.3 inches (0.85m) and the fin fillet was modified to take account of this. The fin also now sat on top of an 11-inch (0.28m) tall extension.

All these modifications solved the question of weight balance, but only partly addressed the aerodynamic balance problem. Under the fuselage a new and larger ventral fin was added on the centreline, immediately below the modified fin, to balance the increased side area of the new nose. In tests, even this was found to be insufficient to maintain directional stability, particularly at high angles of attack, so a further 18-inch (0.45m) extension was added to the top of the fin.

The new design was given the company designation of HS.1184, and the study revealed that the cost of a two-seater would be £1.15 million, as opposed to £0.85 million for the single-seater. This was deemed acceptable by the treasury, which after approving an order for two pre-production development aircraft as part of the study, ordered 14 production examples of the trainer, designated Harrier T.2 and powered by the Pegasus 6 Mk101 engine producing 19,000lb (8618kg) of thrust. The last four aircraft of this first batch of trainers, XW926 and 7 and XW933 and 4, were modified to take the Pegasus 10 Mk102 with 20,500lb (9299kg) of thrust, and these were designated as Harrier T.2As. The first 10 T.2s were later upgraded to T.2A standard with the addition of this engine.

In 1969, the first pre-production prototype, XW174, made its first flight in the hands of test pilot Duncan Simpson on April 22, followed by the second aircraft on July 14.

These trainers had the full avionics, navigation and attack systems of the single-seaters, the only exception being there was no moving map display in the rear cockpit, making them fully combat capable aircraft.

With the advent of the Harrier GR.3 with its nose-mounted Laser Ranger and Marked Target Seeker (LRMTS), the T.2As were further modified with the addition of the same system in the nose and the greater power of the Pegasus 11 Mk103 with 21,500lb (9752kg) thrust. They also carried the Radar Warning Receiver (RWR) equipment of the GR.3, mounted in the fin and rear fuselage. The new trainer was known as the T.4, with 13 T.2As being modified to this standard, alongside 12 new aircraft being built in small batches between 1976 and 1987.

The Royal Navy took an interest in the trainer for the Sea Harrier fleet, ordering a single example of a T.4, XW268, before the development of the navalised T.4N.

Three T.4Ns were built and had avionics more suitable for training Sea Harrier pilots, with the exception of the Blue Fox radar, which was not fitted. All four naval trainers were also not fitted with the RAF’s extended LRMTS nose, but in all other respects were fully combat capable as attack aircraft.

With the introduction into service of the Sea Harrier F/A.2, these three aircraft, and two additional T.4s acquired from the RAF, were converted to T.8 standard, flying for the first time in 1994. These aircraft had modified cockpits to better emulate the layout of the F/A.2, again without the Blue Vixen radar, and were powered by the improved Pegasus 11 Mk106 with 21,500lb (9752kg) thrust. Similarly, the RAF had planned to upgrade the T.4As to a new standard known as the T.6 to act as a trainer for the new Harrier GR.5. When it was fully understood just how different the new aircraft was from the earlier Harriers, this project was shelved in favour of a two seat version of the Harrier II, called the T.10.

The US Marine Corps Harrier training squadron, VMAT-203, operated 8 TAV-8As between 1975 and 1987, these aircraft being analogous to the RAF’s T.4, but without the LRMTS nose and the RWR tail. Like the RAF, the advent of the AV-8B in USMC service with its completely different digital cockpit, larger wing and different handling prompted the development of a two-seat version of the new type, known as the TAV-8B.

The improved aerodynamics of the AV-8B meant that the tail did not have to be quite so modified, as had been the case with the earlier trainers, in order to balance the two-seat cockpit which lengthened the nose by the same 47 inches (1.2m) as on the earlier types. On the AV-8B, the fin is increased in height by 17 inches (0.43m) and is of slight broader chord as a result, giving the required directional stability.

Jackie Jackson first flew the prototype on October 21, 1986, and the first production aircraft, 162963, was delivered to VMAT-203 on July 24, 1987. The cockpit is identical to that of the single seater, but the TAV-8B is not fully combat capable, as it only has two underwing pylons for the carriage of drop tanks or practice weapons.

The first 23 TAV-8Bs built, 22 for the USMC and one for the Spanish Navy, had the Pegasus 11 Mk106 with 21,500lb (9752kg) thrust. Two later aircraft built to Harrier II Plus standard but without the radar were delivered to the Italian Navy and powered by the Pegasus 11-61 or F402-RR-408 of 23,800lb (10,795kg) thrust.

The Harrier T.10 for the RAF was similar to the TAV-8B with one major exception, it retained the eight underwing pylons of the GR.5, and was fitted with the same Forward Looking Infrared (FLIR) system, making it fully combat capable. Powered by the Pegasus 11-21 Mk106 of 21,750lb (9866kg) thrust, the first of 13 T.10s built for the RAF made its maiden flight on April 7, 1994, and entered service with 20(R) Squadron, the Harrier OCU, on March 1, 1995. The last trainer version, the T.12, was a conversion of the T.10 to the same weapons, avionics and software standard of the GR.9. Twelve aircraft were converted to T.12 standard between 2003 and 2006.

Words: Tim Callaway