tsr-2

The British Aircraft Corporation TSR-2 is a cancelled Cold War strike and reconnaissance aircraft developed by the British Aircraft Corporation (BAC), for the Royal Air Force (RAF) in the late 1950s and early 1960s. The TSR-2 was designed around both conventional and nuclear weapons delivery: it was to penetrate well-defended frontline areas at low altitudes and very high speeds, and then attack high-value targets in rear areas. Another intended combat role was to provide high-altitude, high-speed stand-off, side-looking radar and photographic imagery and signals intelligence, aerial reconnaissance. Only one airframe flew and test flights and weight-rise during design indicated that the aircraft would be unable to meet its original stringent design specifications. The design specifications were reduced as the result of flight testing.Burke 2010, p. 109.

The TSR-2 was the victim of ever-rising costs and inter-service squabbling over Britain's future defence needs, which together led to the controversial decision in 1965 to scrap the programme. It was decided to order an adapted version of the General Dynamics F-111 instead, but that decision was later rescinded as costs and development times increased. The replacements included the Blackburn Buccaneer and McDonnell Douglas F-4 Phantom II, both of which had previously been considered and rejected early in the TSR-2 procurement process. Eventually, the smaller swing-wing Panavia Tornado was developed and adopted by a European consortium to fulfil broadly similar requirements to the TSR-2.

Development

Operational environment

The introduction of the first jet engines in the late-World War II period led to calls for new jet-powered versions of practically every aircraft then flying. Among these was the design of a replacement for the de Havilland Mosquito, at that time among the world's leading medium bombers. The Mosquito had been designed with the express intent of reducing the weight of the aircraft in order to improve its speed as much as possible. This process led to the removal of all defensive armament, improving performance to the point where it was unnecessary anyway. This high-speed approach was extremely successful, and a jet-powered version would be even more difficult to intercept.Wynn 1997, pp. 65–68.

This led to Air Ministry specification E.3/45. The winning design, the English Electric Canberra, also dispensed with defensive armament, producing a design with the speed and altitude that allowed it to fly past most defences. The design's large wings gave it the lift needed to operate at very high altitudes, placing it above the range where even jet powered fighters were able to intercept it. The Canberra could simply fly over its enemy with relative impunity, a quality that made it naturally suited to aerial reconnaissance missions. The design was so successful that it was licensed for production in the United States, one of very few such cases. The Martin RB-57D and RB-57F American-built reconnaissance subtypes further extended the wings up to a span for extremely high altitude capabilities.

This high-speed, high-altitude approach was effective until the late 1950s, when the Soviet Union began to introduce its first surface-to-air missiles (SAMs). SAMs had speed and altitude performance much greater than any contemporary aircraft. The Canberra, and other high-altitude aircraft like the British V bombers or United States' Boeing B-52 Stratofortress, were extremely vulnerable to these weapons. The first aircraft to fall victim to the Soviet S-75 ''Dvina'' (NATO name "SA-2 Guideline") SAM was a Taiwanese RB-57, a US reconnaissance version of the Canberra, shot down in 1959.

The solution was to fly lower: since radar operates in line-of-sight, the curvature of the Earth renders low-flying aircraft invisible beyond a certain range, the radar horizon.Spick 1986, pp. 6–8. In practice, trees, hills, valleys and any other obstructions reduce this range even more, making a ground-based interception extremely difficult. The Canberra was designed for medium- to high-altitude flight and was not suitable for continuous terrain-hugging flight; this would require a completely different aircraft.Wynn 1997, p. 503. Low-level strike aircraft, or "interdictors", grew into a new class of their own during the late 1950s. They generally featured high wing loading to reduce the effects of turbulence and cross-wind, some form of high-performance navigational radar to allow very low flight at high speeds, and large fuel loads to offset the higher fuel use at low altitudes.

GOR.339

Aware of the changing operational environment, the Ministry of Supply started work with English Electric in 1955, attempting to define a new light bomber to replace the Canberra.''Flight'', 9 October 1969, p. 570. These early studies eventually settled on an aircraft with a ferry range, Mach 1.5 speed "at altitude" and low-level range. A crew of two was required, one being the operator of the advanced navigational and attack equipment. The bombload was to be four bombs.

The requirements were eventually made official in November 1956 with General Operational Requirement 339 (GOR.339), which was issued to various aircraft manufacturers in March 1957. This requirement was exceptionally ambitious for the technology of the day, requiring a supersonic all-weather aircraft that could deliver nuclear weapons over a long range, operate at high level at Mach 2+ or low level at Mach 1.2, with STOL or possible VTOL performance.Thornborough 2005, p. 6. The latter requirement was a side-effect of common battle plans from the 1950s, which suggested that nuclear strikes in the opening stages of war would damage most runways and airfields, meaning that aircraft would need to take off from "rough fields" such as disused Second World War airfields, or even sufficiently flat and open areas of land.

Specifically, the requirement included:
* Delivery of tactical nuclear weapons at low level in all weathers, by day and night
* Photo-reconnaissance at medium level (day) and low level (day and night)
* Electronic reconnaissance in all weathers
* Delivery of tactical nuclear weapons day and night at medium altitudes using blind bombing if necessary
* Delivery of conventional bombs and rockets

Low level was stated to be under with an expected attack speed at sea level of Mach 0.95. The operational range was to be operating off runways of no more than .Thornborough 2005, p. 5. The TSR-2 was able to operate at above the ground at speeds of Mach 1.1; its range allowed it to operate strategically in addition to tactical scenarios.

Political changes

As this specification was being studied by various manufacturers, the first of the political storms that were to dog the project reared its head, when Defence Minister Duncan Sandys stated in the 1957 Defence White Paper that the era of manned combat was at an end and ballistic missiles were the weapons of the future. This viewpoint was vigorously debated by the aviation industry and within the Ministry of Defence for years.Smith 1980, p. 130. Senior RAF officers argued against the White Paper's premise, stating the importance of mobility, and that the TSR-2 could not only replace the Canberra, but potentially the entire V bomber force.

In addition to the argument over the need for manned aircraft, additional political machinations had the effect of complicating the project. In September 1957 the Ministry of Supply informed the heads of the aviation companies that the only acceptable proposals would be those issued from teams consisting of more than one company.Kaldor et al. 1979, p. 289. There was a large number of competing aircraft manufacturing companies in the UK, while orders were decreasing; thus the government intended to foster cooperation between certain companies and encourage mergers.Segell 1997, p. 117.

Another political matter, that did not help, was the mutual distrust between the various services. At the time that GOR.339 was being defined, the Royal Navy was in the midst of its NA.39 project, which would eventually become the Blackburn Buccaneer. This was a low-altitude subsonic attack aircraft, designed for over-water as opposed to overland use. The savings involved in both forces using a common aircraft would be considerable, and Blackburn offered the RAF a version of the NA.39 to fit some of the GOR.339 requirements.Segell 1997, p. 120. The Chief of the Defence Staff, and former First Sea Lord, Lord Mountbatten was a loyal proponent of the Buccaneer, later claiming that five of the type could be purchased for the same price as one TSR-2. However, the RAF rebuffed the proposal, stating that it was unsuitable due to poor takeoff performance and the avionics not being capable of the desired role. As one RAF official put it, "If we show the slightest interest in NA.39 we might not get the GOR.339 aircraft."

Another political opponent of the TSR-2 project was Sir Solly Zuckerman, at the time the Chief Scientific Advisor to the Ministry of Defence. Zuckerman had a low opinion of British technological achievements and was in favour of procuring military hardware from the United States.Wood 1986, p. 158.

Submissions

Work on GOR.339 continued, with a deadline for submissions on 31 January 1958. Many proposals were entered; English Electric teamed up with Short Brothers and submitted its P.17A along with the Shorts' P.17D, a vertical-lift platform that would give the P.17 a VTOL capability; designs were also received from Avro, Blackburn (the NA.39), de Havilland, Fairey, Hawker and Vickers-Armstrongs.Segell 1997, p. 110. The Air Ministry eventually selected the EE P.17A and the Vickers-Armstrongs Type 571 for further consideration. The Ministry was particularly impressed with the Vickers submission, which included not only the aircraft design, but a "total systems concept" outlining all the avionics, support facilities and logistics needed to maintain the aircraft in the field. Official opinions of English Electric's management found it decidedly lacking in comparison to Vickers, but the combination of the two was felt by officialdom to be a useful marriage and accordingly the development contract was awarded to Vickers, with English Electric as sub-contractor.Burke 2010, pp. 66–68.Segell 1997, p. 118.

The existence of GOR.339 was revealed to the public in December 1958 in a statement to the House of Commons. Under pressure by the recommendations of the Committee on Estimates, the Air Ministry examined ways that the various project proposals could be combined, and in January 1959 the Minister of Supply announced that the TSR-2 would be built by Vickers-Armstrongs working with English Electric;Winchester, ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft'', 2005, p. 16. the initials coming from "Tactical Strike and Reconnaissance, Mach 2", the 'Strike' part of the designation specifically referring in RAF terminology to a nuclear weapons role.

On 1 January 1959, the project was given an official go-ahead; in February, it came under the new designation Operational Requirement 343. OR.343 was more specific and built upon work from the various submissions to GOR.339 specifically stating that the low-level operations would be at or less, and that Mach 2 should be attained at altitude.

Mission

The envisioned "standard mission" for the TSR-2 was to carry a weapon internally for a combat radius of . Of that mission was to be flown at higher altitudes at Mach 1.7 and the into and out of the target area was to be flown as low as 200 ft at a speed of Mach 0.95. The remainder of the mission was to be flown at Mach 0.92. If the entire mission were to be flown at the low 200 ft altitude, the mission radius was reduced to . Heavier weapons loads could be carried with further reductions in range.Winchester, ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft'', 2005, p. 25. Plans for increasing the TSR-2's range included fitting external tanks: one tank under each wing or one tank carried centrally below the fuselage. If no internal weapons were carried, a further could be carried in a tank in the weapons bay. Later variants would have been fitted with variable-geometry wings.

The TSR-2 was also to be equipped with a reconnaissance pack in the weapons bay which included an optical linescan unit built by EMI, three cameras and a sideways-looking radar (SLR) in order to carry out the majority of its reconnaissance tasks. Unlike modern linescan units that use infrared imaging, the TSR-2's linescan would use daylight imaging or an artificial light source to illuminate the ground for night reconnaissance.Thornborough 2005, p. 36.

Tactical nuclear weapons

Carriage of the existing Red Beard tactical nuclear bomb had been specified at the beginning of the TSR-2 project, but it was quickly realised that Red Beard was unsuited to external carriage at supersonic speeds, had safety and handling limitations, and its 15  kt yield was considered inadequate for the targets assigned. Instead, in 1959, a successor to Red Beard, an "Improved Kiloton Bomb" to a specification known as Operational Requirement 1177 (OR.1177), was specified for the TSR-2. In the tactical strike role, the TSR-2 was expected to attack targets beyond the forward edge of the battlefield assigned to the RAF by NATO, during day or night and in all weathers. These targets comprised missile sites, both hardened and soft, aircraft on airfields, runways, airfield buildings, airfield fuel installations and bomb stores, tank concentrations, ammunition and supply dumps, railways and railway tunnels, and bridges.''AIR 77/654: The Limitations of 10 kt Free-Fall Tactical Weapon As A Replacement for Red Beard''. London: Public Record Office, 2010. OR.1177 specified 50, 100, 200 and 300 kt yields, assuming a circular error probable of and a damage probability of 0.8, and laydown delivery capability, with burst heights for targets from 0 to above sea level. Other requirements were a weight of up to , a length of up to , and a diameter up to (the same as Red Beard).''AIR 2/17322: Draft Air Staff Requirement No. O.R.1177 An Improved Kiloton Bomb''. London: Public Record Office, 2010.

However, a ministerial ruling on 9 July 1962 decreed that all future tactical nuclear weapons should be limited to a yield of 10 kt.''AIR 2/17325 E31B: Joint Naval/Air Staff Requirement G.D.A.15/O.R.1177 (Issue 3): An Improved Kiloton Bomb pp. 1–2''. London: Public Record Office, 2010. The RAF issued a new version of the OR.1177 specification, accepting the lower yield, while making provision in the design for it to be capable of adaptation later for a higher yield, in the event of the political restriction being lifted. Meanwhile, the RAF explored ways of compensating for the lower yield by including, in the specifications for both the bomb and TSR-2, provision for releasing the smaller weapons in salvos, dropping sticks of four of the revised OR.1177, later named WE.177A, at intervals to prevent the detonation of the first weapon destroying the succeeding ones before they could, in turn, detonate. This led to the requirement that the TSR-2 must be able to carry four WE.177As, two internally and two on external underwing stores pylons—the width of the TSR-2 bomb bay (originally designed to accommodate a single Red Beard weapon) necessitating the reduction in diameter of the WE.177A to , the bomb's width and fin span being constrained by the need to fit two WE.177 bombs side-by-side in the aircraft's bomb bay. The requirement for stick bombing using nuclear weapons was soon dropped as larger yield bombs came back into favour.

A drawback of carrying WE.177 on external pylons was a limitation due to aerodynamic heating of the bomb's casing. WE.177A was limited to a maximum carriage time of five minutes at Mach 1.15 at low level on TSR-2, otherwise the bomb's temperature would rise above its permitted maximum. This would impose a severe operational restriction on TSR-2, as the aircraft was designed for Mach 1+ cruise at this height.''AIR 2/17330 E9A p1''. London: Public Record Office, 2010.

Nuclear stand-off missiles were also proposed for the TSR-2 early in development but not proceeded with. These included an air-launched development of the Blue Water missile,Wood 1986, p. 168. carried underwing, or semi-recessed in the bomb bay, and an air-launched ballistic missile, referred to as ''Grand Slam'', with a warhead derived from that intended for the Skybolt missile, and a range of .Wood 1986, p. 155. Conventional missiles were catered for instead, with the design originally centring on use of the AGM-12 Bullpup, then moving on to favour the French AS-30 before settling on the new OR.1168 missile (which would become the TV-guided AJ-168 Martel).

After the cancellation of the TSR-2, the RAF eventually filled the tactical strike requirement using McDonnell F-4 Phantom IIs with US dual-key nuclear weapons, but continued their attempts to get the 10 kt limit lifted. Development of WE.177A was delayed by several years due to the Atomic Weapons Research Establishment (AWRE) at Aldermaston being inundated with work on other warhead developments. AWRE workload eased after completion of the Polaris missile warheads and work was able to resume on the WE.177A, deliveries to the RAF beginning in late 1971 for deployment on Buccaneers of RAF Germany, a year after WE.177A deliveries to the Royal Navy. Approval for high-yield tactical weapons was eventually gained in 1970 and, by 1975, the RAF had WE.177C, which at almost 200 kt was a weapon very similar to what they had planned for the TSR-2 in 1959.

Design

Throughout 1959, English Electric (EE) and Vickers worked on combining the best of both designs in order to put forward a joint design with a view to having an aircraft flying by 1963, while also working on merging the companies under the umbrella of the British Aircraft Corporation. EE had put forward a delta winged design and Vickers, a swept wing on a long fuselage. The EE wing, born of their greater supersonic experience, was judged superior to Vickers, while the Vickers fuselage was preferred. In effect, the aircraft would be built 50/50: Vickers the front half, EE the rear.

The TSR-2 was to be powered by two Bristol-Siddeley Olympus reheated turbojets, advanced variants of those used in the Avro Vulcan. The Olympus would be further developed and would power the supersonic Concorde. The design featured a small shoulder-mounted delta wing with down-turned tips, an all-moving swept tailplane and a large all-moving fin. Blown flaps were fitted across the entire trailing edge of the wing to achieve the short takeoff and landing requirement, something that later designs would achieve with the technically more complex swing-wing approach. No ailerons were fitted, control in roll instead being implemented by differential movement of the slab tailplanes. The wing loading was high for its time, enabling the aircraft to fly at very high speed and low level with great stability without being constantly upset by thermals and other ground-related weather phenomena.Winchester, ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft'', 2005, p. 24. The EE Chief Test Pilot, Wing Commander Roland Beamont, favourably compared the TSR-2's supersonic flying characteristics to the Canberra's own subsonic flight characteristics, stating that the Canberra was more troublesome.

According to the Flight Envelope diagram,McLelland 2010, p. 92. TSR2 was capable of sustained cruise at Mach 2.05 at altitudes between and and had a dash speed of Mach 2.35 (with a limiting leading edge temperature of 140 °C). Its theoretical maximum speed was Mach 3 in level flight at .

The aircraft featured some extremely sophisticated avionics for navigation and mission delivery, which would also prove to be one of the reasons for the spiralling costs of the project. Some features, such as forward looking radar (FLR) and side-looking radar for navigational fixing, only became commonplace on military aircraft years later. These features allowed for an innovative autopilot system which, in turn, enabled long distance terrain-following sorties as crew workload and pilot input had been greatly reduced.

There were considerable problems with realising the design. Some contributing manufacturers were employed directly by the Ministry rather than through BAC, leading to communication difficulties and further cost overruns. Equipment, an area in which BAC had autonomy, would be supplied by the Ministry from "associate contractors", although the equipment would be designed and provided by BAC, subject to ministry approval. The overall outlay of funds made it the largest aircraft project in Britain to date.

Unlike most previous projects, there were to be no prototypes. Under the "development batch" procedure pioneered by the Americans (and also used by English Electric for the Lightning), there would instead be a development batch of nine airframes, to be built using production jigs.Segell 1997, p. 121. The choice of proceeding to production tooling turned out to be another source of delay, with the first aircraft having to adhere to strict production standards or deal with the bureaucracy of attaining concessions to allow them to exhibit differences from later airframes. Four years into the project, the first few airframes had effectively become prototypes in all but name, exhibiting a succession of omissions from the specification and differences from the intended pre-production and production batches.

Operational history

Testing

Despite the increasing costs the first two of the development batch aircraft were completed. Engine development and undercarriage problems led to delays for the first flight which meant that the TSR-2 missed the opportunity to be displayed to the public at 1964's Farnborough Airshow.Thornborough 2005, p. 28. In the days leading up to the testing, Denis Healey, the Opposition shadow secretary for defence, had criticised the aircraft saying that by the time it was introduced it would face "new anti-aircraft" missiles that would shoot it down making it prohibitively expensive at £16 million per aircraft (on the basis of only 30 ordered).

Test pilot Roland Beamont finally made the first flight from the Aeroplane and Armament Experimental Establishment (A&AEE) at Boscombe Down, Wiltshire, on 27 September 1964. Initial flight tests were all performed with the undercarriage down and engine power strictly controlled—with limits of and on the first (15-minute) flight. Shortly after takeoff on ''XR219's'' second flight, vibration from a fuel pump at the resonant frequency of the human eyeball caused the pilot to throttle back one engine to avoid momentary loss of vision.Wood 1986, p. 161.Gardner 1981, p. 116.

Only on the 10th test flight was the landing gear successfully retracted—problems preventing this on previous occasions, but serious vibration problems on landing persisted throughout the flight testing programme. The first supersonic test flight (Flight 14) was achieved on the transfer from A&AEE, Boscombe Down, to BAC Warton. During the flight, the aircraft achieved Mach 1 on dry power only (supercruise). Following this, Beamont lit a single reheat unit as the other engine's reheat fuel pump was unserviceable, with the result that the aircraft accelerated away from the chase English Electric Lightning (a high speed interceptor) flown by Wing Commander James "Jimmy" Dell, who had to catch up using reheat on both engines. On flying the TSR-2 himself, Dell described the prototype as handling "like a big Lightning".O'Sullivan, Bill
"The Beamont Files."
''Newark Air Museum''. Retrieved: 2 February 2011.

Over a period of six months, a total of 24 test flights were conducted. Most of the complex electronics were not fitted to the first aircraft, so these flights were all concerned with the basic flying qualities of the aircraft which, according to the test pilots involved, were outstanding. Speeds of Mach 1.12 and sustained low-level flights down to 200 ft were achieved above the Pennines. Undercarriage vibration problems continued, however, and only in the final few flights, when XR219 was fitted with additional tie-struts on the already complex landing gear, was there a significant reduction in them.Wood 1986, p. 179. The last test flight took place on 31 March 1965.Thornborough 2005, p. 33.

Although the test flying programme was not completed and the TSR-2 was undergoing typical design and systems modifications reflective of its sophisticated configuration, " ere was no doubt that the airframe would be capable of accomplishing the tasks set for it and that it represented a major advance on any other type."

Costs continued to rise, which led to concerns at both company and government upper management levels, and the aircraft was also falling short of many of the requirements laid out in OR.343, such as takeoff distance and combat radius. As a cost-saving measure, a reduced specification was agreed upon, notably reductions in combat radius to , the top speed to Mach 1.75 and takeoff run up increased from .

Project cancellation

By the 1960s, the United States military was developing the swing-wing F-111 project as a follow-on to the Republic F-105 Thunderchief, a fast low-level fighter-bomber designed in the 1950s with an internal bay for a nuclear weapon.Gunston 1978, pp. 12–13. There had been some interest in the TSR-2 from Australia for the Royal Australian Air Force (RAAF), but in 1963, the RAAF chose to buy the F-111 instead, having been offered a better price and delivery schedule by the American manufacturer.Segell 1997, p. 122. Nonetheless, the RAAF had to wait 10 years before the F-111 was ready to enter service, by which time the anticipated programme cost had tripled.Wood 1986, p. 160. The RAF was also asked to consider the F-111 as an alternative cost-saving measure. In response to suggestions of cancellation, BAC employees held a protest march, and the new Labour government, which had come to power in 1964, issued strong denials. However, at two