by Damien Burke
A TSR2 windtunnel fuselage model with half-cone intakes and the in-flight refuelling probe fairing. The latter was later reduced in size slightly so that its aft end would not foul the equipment-bay door. BAE Systems via Brooklands Museum
Damage to the Second World War runway at Turweston after a single take-off run by Scimitar WW134 in January 1960. Surface erosion of this sort would have been a serious issue when operating the much more powerful TSR2 from rough strips. BAE Systems via Brooklands Museum
At the end of December the design study contract ran out, but work had to continue regardless if the project was to have any hope of meeting its deadline. On 1 January 1960 the wing thickness taper was made equal on top and bottom, thus losing the flat lower surface and simplifying construction somewhat. The large main undercarriage bay doors were creating a substantial destabilizing effect when open, and various means were tried to ameliorate this, such as smaller bay doors, horizontal strakes on the nose, an extra sawtooth extension on the wing leading edge, and baffles and fairings around and within the undercarriage bays. In windtunnel tests the most impressive results came from an airframe change, lengthening the fuselage by 18in (46cm) to bring it in line with the tailplane trailing edge, and also raising the tailplane position. It was also helpful to ensure that the main doors were closed immediately after the undercarriage had been lowered, and this change, the fuselage extension and the revised tailplane position were incorporated. Windtunnel tests had also been carried out in November of a down-turned wingtip designed to combat Dutch roll, and the results were now available and looked promising.
The design was now allegedly frozen so that detailed production drawings could be produced and the work of building the aircraft could begin. However, by late February increases in the weight of the engines, reheat pipes and reheat nozzles had contributed to another rearward shift of the c.g. The sawtooth leading edge with variable leading-edge flap had shifted the aerodynamic centre forward, added weight and further reduced the aft c.g. limit, making the balance problem acute and introducing some undesirable pitch characteristics. Three methods were considered for dealing with this: moving the undercarriage aft by changing the pintle position, along with moving the wing and tail further aft and extending the nose; a similar scheme but with a bodily movement of the undercarriage (entailing centre fuselage redesign); or a similar scheme but using increased rake on the undercarriage oleo to change its position. Transonic stability had suffered in the most recent windtunnel tests of a fully representative TSR2 layout, the sawtooth leading edge causing an undesirable transonic aerodynamic centre shift. The favoured solution was to delete it and extend the wing chord by moving the trailing edge back.
Windtunnel results on the down-turned wingtip had shown that it introduced no adverse effects and dealt with the Dutch roll issue, and the reduction in the span of the flaps produced no serious change in their performance either. Such wingtips would require a complex joint at the end of the primary wing box, but as there was minimal loss of lift there was a strong case for going ahead with this change. There were, however, some strong disagreements with the analysis produced by the windtunnel section at Warton, one writer describing it as ‘the most dishonest windtunnel report I have ever seen’. Discussion bounced back and forth until the matter was eventually brought to a head when the design was placed on Freddie Page’s desk for a final decision. He wasted no time; the down-turned tips were in, and the sawtooth leading edge was out.
A TSR2 windtunnel model. A false floor has been added to the tunnel so that flight near the ground can be investigated. Note that the rear wheels are cut away to enable different pitch angles to be tried out easily. BAE Systems via Brook-lands Museum
A TSR2 windtunnel model with a selection of external stores. It has the ECM pod and drop tank as illustrated in the Preliminary Brochure general-arrangement drawing, and stores on the tunnel floor include rocket pods, Bullpup missiles, bombs and rockets. This model has down-turned wingtips as well as the sawtooth leading edge. BAE Systems via Brooklands Museum
Another windtunnel model, showing the 450gal (2,045L) slipper tank. This model was used for stores separation tests; note the net in the background to catch items after release. BAE Systems via Brooklands Museum
A meeting on 31 March then dealt with the ‘re-freezing’ of the design, and by April 1960 the airframe was very close to the final and now-familiar TSR2 layout. A drawing issued on the 12th showed the fuselage extended by 6in (15cm) and the wing, tailplane and main undercarriage moved aft 3in (7.6cm) to fix the balance problem. As per Freddie Page’s decision, the leading-edge sawtooth extension on the wing was deleted, the wing chord had been extended rearward 24in (61cm) at the tip to give a perpendicular trailing edge, and the wing tips extended and angled down at 30 degrees, keeping the overall span the same. The fin had been moved 18in (45.7cm) further aft, and the lines of the rear fuselage had been adjusted. This final shift in the airframe configuration may have dealt with the outstanding issues, but it also dealt a blow to English Electric’s production plans, as drawings had to be withdrawn from the production shops, incurring a three-month delay before work could resume.
The rear fuselage had turned out to be another problem area. The July 1959 datum design had included a simple twin reheat nozzle configuration without an ejector nozzle. However, analysis of windtunnel data several months later showed that this area had excessive base drag, and research in Britain and the USA had revealed that afterbody suction was a significant contributor to this. It was a big setback, and leaving the rear-fuselage design unchanged would result in a fuel penalty of up to 6,000lb (2,720kg). Air Ministry staff later misunderstood this, and accused BAC of ‘forgetting’ base drag in its initial design. To solve the problem, the partial vacuum generated here had to be relieved, and the way to do this was to use a fixed airframe ejector nozzle, opening a small gap between the reheat nozzle and the rear fairing to permit airflow through the gap. Asked to reduce the diameter of the final reheat nozzle by 2in (5cm) to make room for this, BSEL readily agreed. As can be seen, although it was supposedly a frozen design, there was still some work under way on the actual shape of the aircraft, though few further changes would now occur. Windtunnel testing was also finally showing acceptable stability and balance, though under wing stores gave some destabilizing effect. Particularly large underwing stores were proving to be a real worry.
Meanwhile, there had been constant debate within the government’s various Ministries as to whether the project was really necessary. The latest NA.39 development and a new foreign contender, the McDonnell F4H Phantom II (‘a much more attractive prospect than any Blackburn Beast’), were brought up time and again. The Air Ministry put together a paper clearly laying out the need for the TSR2, and the new Ministry of Aviation (the MoS’s successor) finally accepted OR.343. The need for low-level penetration to survive in the modern air defence environment was underlined on 1 May 1960, when a United States Air Force (USAF) Lock-heed U-2 reconnaissance aircraft was swatted out of the sky over Sverdlovsk in central Russia by a surface-to-air missile (SAM). Like the October 1959 loss of a Taiwanese Martin RB-57 Canberra over China, this was another victory for the S-75 (SA-2 Guideline) missile. The TSR2’s low-level capabilities were now, without a doubt, the only way to get to the target.
However, the Treasury remained unconvinced, and the next design contract was not finally signed until mid-June, and only covered the period from the start of the year to September 1960. Work also began around this time on designing test rigs for the powered flying controls, general services hydraulics, fuel system (a sophisticated rig that could tilt to allow testing in various flight attitudes) and flap blowing and gearing. To verify stressing calculations on the wing and fuselage structure, test boxes were drawn up, sample areas of structure that could be put together and strength tested before real production components were put together. Planning also began for the flight test programme and the instrumentation that would be needed, plus how it could be f
itted to the aircraft.
By now, the problem of nosewheel lifting on the take-off run had been rumbling on for many months, Ray Creasey of English Electric being particularly concerned and regarding it as the current design’s real Achille’s heel. Vickers’s solution was to incorporate a nose gear leg extension that would be selectable by the pilot. If both tailplane surfaces were equally used for pitch at their maximum extent, an extension of 2.5ft (0.76m) would suffice to lift the nose early enough to meet the shortest take-off run requirement. However, no roll control would be available, and short take-offs with any significant crosswind would become a serious problem. If 5 degrees of tailplane travel were reserved for roll control, the nosewheel extension would need to be 4ft (1.2m) or more, and that was the absolute limit that could be accommodated in the current design. The tailplane travel could well still be insufficient for full roll control in a strong crosswind, and English Electric even looked at a scheme for fitting small ailerons on the wingtips. Moving the main undercarriage 3in (7.6cm) forward of its current position, however, helped things somewhat. Meeting the take-off requirements would now be possible, although special take-off techniques would be required involving the timed selection of the nose-wheel extension and flap blowing during the take-off run to get the best effect.
The final big airframe problem to be dealt with (or so it was thought) was the fin. The size of fin needed to retain directional stability at supersonic speeds was huge, and weight and drag considerations, along with the massive side loads that would be induced during rapid rolls, meant that this was simply not practical. The way forward seemed to be the smallest possible fin coupled with an auto-stiffener mechanism that detected lateral accelerations and automatically moved the fin by small degrees to compensate, and this relatively small fin, with an area of 87sq ft (8.08sq m), was a feature of almost all of the general-arrangement drawings throughout the design process. However, by September 1960 it was becoming clear that the fin needed some serious work, as its flutter speed had turned out to be unacceptably low, at just half of the design’s maximum diving speed. Similar problems with the tailplane had been solved by strengthening the root rib, which avoided the need to improve spigot stiffness; the fin was not so easily fixed. A protracted argument blew up between English Electric and Vickers-Armstrongs over the solution to fin flutter, and to Vickers-Armstrongs’ displeasure English Electric presented a much larger 109 sq ft (10.12sq m) fin that went part way to solving the flutter issue, though the necessary root thickness was huge. Vickers-Armstrongs was not at all happy with the resulting serious weight and drag penalty, and while it tinkered with the planform, resulting in the final 105 sq ft (9.75sq m) fin with a small blister at the base to cover the bearing, English Electric discovered that a mass-balance at the base of the leading edge was fairly effective in reducing flutter, and appropriate windtunnel tests were begun. To everybody’s horror they showed that flutter was still a problem at high Mach numbers, and increasing the size of the mass-balance was not practical. The eventual solution, born of desperation, was the inclusion of a sprung mass-balance. A pair of spring-linked weights with hydraulic dampers would be installed in the fin leading edge, by the root, and careful engineering meant no further changes to the planform to accommodate this. Despite the fin’s increased size, the auto-stiffener would still be required. This was an interesting early example of the advantages of accepting an unstable configuration that could be compensated for by computer control.
This windtunnel model has a configuration very close to the final layout of tailplane, large fin and contoured rear fairing. Tufts on the underside of the tailplane give an indication of the airflow over the surface. BAE Systems via Brooklands Museum
TSR2 final layout – with down-turned wingtips, sawtooth deleted and enlarged fin; February 1961. Only minor changes would follow from this date, e.g. to navigation beacon light positions.
In September the rear-fairing design and construction, which was going to be given to Lucas, came in for some competition when BSEL made a proposal. This was highly attractive on cost grounds alone, apart from the logic of giving the engine maker the job of building the bit that wrapped around the exhausts. The reheat shroud was to be extended, bringing down temperatures in the rear fairing and thereby reducing the use of Nimonic material and enabling more conventional construction to be employed. Moreover, lots of ‘free’ testing would be available during Olympus 22R test runs. Not surprisingly, BSEL ended up with job, being given an intention to proceed in December and a contract in January 1961.
Throughout these closing months of the existing design contract the continued need for the aircraft was still being endlessly debated by the bureaucracy. There was brief concern at Vickers when the Americans submitted a brochure on the Republic F-105D to meet OR.343. The Air Staff’s OR department gave it short shrift, writing on 29 August: ‘This aircraft has no chance of being regarded as a contender for O.R.343’. The TSR2’s use in a strategic role was also examined in some detail. The first draft contract covering the production of the actual development-batch aircraft was received by Vickers in August, but the Prime Minister and the Chancellor of the Exchequer both felt that they could not allow the Treasury to approve anything until a full discussion on TSR2 was held in the Defence Committee. On 16 September 1960 a meeting of the Defence Committee finally agreed that TSR2 should continue, and the Treasury could continue to negotiate the terms of the contract covering the development-batch aircraft. The contract was finally signed in October, and it was now time to begin cutting metal.
A final-configuration TSR2 model being prepared for windtunnel testing on a rig that permitted various angles of incidence to be set up. Nearly 10,000 individual windtunnel test runs were carried out during the TSR2 project’s life. BAE Systems via Warton Heritage Group
A final-configuration TSR2 model positioned at high incidence in a windtunnel; it was in this sort of attitude that most of the stability problems became evident. BAE Systems via Brooklands Museum
By the end of 1960 Vickers/English Electric had an aircraft design that was close to 90,000lb (40,825kg) in weight for the 1,000nm sortie, with a promise that, as long as weight was held below 95,000lb (43,100kg), it would be able to meet each performance aspect of the requirement fully. The manufacturers were confident that holding the weight down would not be a problem; the MoA, however, was not.
OR.343 Evolves
Throughout the period of airframe and system design, from 1959 to mid-1961, the Air Staff were refining OR.343 in light of decisions made along the way. Issue 2 of OR.343, completed on 21 February 1961, contained a number of significant changes. High-level cruise, previously to be simply ‘supersonic’, was now defined as being no less than Mach 1.7. The term ‘terrain clearance’ was replaced by ‘terrain following’ (a significant concept change), and in terrain-following mode no single failure was to endanger the aircraft. This simple statement would produce an expensive result. Navigation fixes were relaxed to being taken every 100nm (115 miles; 185km), rather than every 50nm (57miles; 90km). On the armament side the nuclear store was still OR.1127/Red Beard, though it was clear that this was now likely to be replaced by a new development. The carriage of 1,000lb bombs changed from ‘four or more’ to ‘six’, and the carriage of at least six 25lb practice bombs was added. The internal carriage of two or more guided missiles to OR.1173 was deleted, along with internal carriage of rockets. External stores were now specified; either two tactical nuclear weapons, four 1,000lb HE bombs, four rocket pods (thirty-seven 2in) or four guided missiles to OR.1173 (Bullpup at the time). All of these were to be carried in combination with internal stores if need be, but no mix of nuclear and conventional stores was required. Various detail changes to the pilot’s display, communication equipment, automatic flight-control system (AFCS) and fuel system were also included. Years down the line, all of these changes would be described by the Air Staff and government as ‘minor’, when in reality almost all of them involved considerable extra development
effort and expense.
A general-arrangement drawing of the TSR2 as built.
CHAPTER FOUR
Building TSR2
On 1 July 1960 the British Aircraft Corporation was formed, bringing Vickers and English Electric together as subsidiaries of the new firm, along with the Bristol Aeroplane Company, though for the time being each firm continued on more or less as before, no actual merger taking place. With negotiations under way on the contract to produce the nine development-batch aircraft, BAC was confident enough to begin putting together full-scale mock-ups of the complete aircraft to aid the design of the integrated structure and systems to be built within the real airframes. Various partial mock-ups had already been put together at Warton and Weybridge to aid early design work, but the final mock-ups would be more substantial affairs of wood and metal. Construction of one mock-up at each site began during September 1960, and they were complete by the end of 1961. By this time the major structural components had been designed, so the jigs and tooling needed to build them could be constructed. From mid 1961 onwards the factory floors had been cleared to take on the task of producing the TSR2 airframes, and jigs were under construction at both sites.
Contract KD/2L/02/C.B.42(a) October 1960 Development Batch (Aircraft 1–9)
Aircraft
Serial No.
