BRISTOL AND THE BOMBER GAP

The Avro Lincoln - seen here at RAF Cosford - dwarfed the Lancaster it was derived from. Although 30 years younger than the biplane parked under its wing, it was soon to be made obsolete itself by a new generation of jet propelled V bombers.

During 1951 – at the height of the Korean War - the British Government became worried by the apparent bomber gap developing between the Royal Air Force and the Soviet Union. The Soviet Air Force seemed to have far more bomber aircraft than Britain’s existing fleets of Canberras and Lincolns, and intelligence reports reaching Prime Minister Winston Churchill indicated the USSR was planning a massive action of an unspecified nature in 1953. With these thoughts in mind the RAF was asked to consider the use of "flying bombs" made from plastic as the primary weapon of Britain's future nuclear strike force.

Although the United States had perfected the atomic bomb in 1945 and the Soviet Union had become the second nuclear power in 1949, the first British nuclear fission weapon would not in fact be tested until October 1952. This was less than a month before the first American hydrogen bomb was detonated at Enewetok in the Marshall Islands.

Bristol Aircraft designed the Type 182 Red Rapier as a pilotless, radio controlled expendable bomber – combining some of the features of the wartime German V-1 with those of later cruise missiles such as the American Tomahawk. Indeed, the US military would include such similar vehicles as the Snark and Chance-Vought SSM-N-8 Regulus in its order of battle later in the 1950s.

The Chance Vought SSM-N-8 Regulus was similar in format to the Bristol Type 182. Unlike the later Tomahawk cruise missile, launching a Regulus from a submarine involved the vessel surfacing and becoming vulnerable to detection and attack as the missile was assembled. The Regulus also lacked the terrain following radar based guidance system fitted to the Tomahawk and first developed as part of the American Supersonic Low Altitude Missile (SLAM) programme. The SLAM was designed to attack up to 16 Soviet targets, ejecting hydrogen bombs upward from its fuselage and using its speed to escape the resultant blast en route to the next objective. However, SLAM was never fully developed or deployed as it was considered too much of a threat to the balance of terror between east and west and likely to encourage a Communist first strike on the USA.

Vickers Valiant XD 818 - seen at RAF Cosford - dropped the first British hydrogen bomb

With the cancellation of the Bristol Type 182, the nuclear strike force of the RAF rested with the three new types of manned four-engined V-bombers.

The swept-wing Vickers Valiant first flew in May 1951. As an insurance against its possible failure, the more conventional straight-winged Short Sperrin was also developed as far as two flying prototypes. But in the event the Valiant was a success, despite being rushed into active service with conventional bombs during the October 1956 Suez Crisis. As the correct bomb aiming equipment was not ready by the start of the ill fated "Operation Musketeer", the damage inflicted by Malta-based Valiants on Egyptian airfields was minimal. But on 11 October 1956 a Valiant of 49 Squadron dropped an example of Britain's first practical free fall plutonium bomb - the three kiloton yield Blue Danube - just 110 yards from the intended ground zero at a remote test site at Maralinga in the Australian Outback. Then - on 15 May 1957 - Valiant XD818 - another 49 Squadron aircraft - dropped Britain’s first hydrogen bomb on Malden Island - near Christmas Island - and tests continued in the South Pacific into 1958.

Meanwhile, the delta-winged Avro Vulcan’s maiden flight was in August 1952 while the crescent-winged Handley Page Victor first flew that December.

Myasishchev M-4 - NATO code name Bison - was the Soviet equivalent to the Boeing B-52

On 14 August 1953 the Soviet Union tested its first hydrogen bomb and on 1 May 1954 unveiled its first operational jet propelled nuclear-armed long-range bomber aircraft, the Tupolev Tu-16 "Badger". In July 1955, American fears of a bomber gap grew after formations of new 500 mph Tupolev Tu-95 "Bear" turboprop and 625 mph Myasishchev M-4 "Bison" jet bombers were flown repeatedly over US observers at a Moscow air display.

By then however, the United States Air Force’s Strategic Air Command had Boeing B-52 bombers permanently in the air and ready for retaliatory bombing of communist targets. Indeed, on 18 July at a Summit Conference in Geneva, US President Eisenhower proposed an "Open Skies" policy that would allow each superpower to photograph each other’s territories from the air.

However, the RAF lacked a matching strategic reconnaissance aircraft for its new V-Force, despite one Vickers Valiant squadron being dedicated to this task. Lone Canberra twin-engined light bombers had been conducting reconnaissance operations over the Soviet Union with impunity since the early 1950s but by 1954 it was thought that for a viable strategic reconnaissance force, a dedicated platform was required. Whereas the Americans were working concurrently on a the subsonic high altitude Lockheed U-2, the Ministry of Supply plumped for a high altitude, high speed aircraft with an extensive sensor suite.

Invitations to tender for R.156T ( which was worked up around Operational Requirement (OR) 330) were issued to A.V. Roe, English Electric, Handley Page Vickers and Shorts by the Air Staff in 1954.

As a reconnaissance platform, the OR.330 aircraft was to carry a suite of optical and radar sensors to provide targeting intelligence and post strike assessment for the V-force. With a specified speed of Mach 2.5 with Mach 3.0 dash speed over the target at an altitude of 70 000ft, OR.330 was to be immune to Soviet fighter defences and have a range of 5 000 nautical miles.

All the contenders submitted a canard configuration, mainly as a means to retain stability in the high-speed sections of the flight profile.

A.V. Roe of Manchester had provided the RAF with its bomber aircraft for many years, the most famous being the Lancaster. Avro, as they were usually known, were developing the Vulcan for the RAF and this would enter Squadron service in 1957. Development of its possible successor was underway by that time and the experience of bringing the Vulcan to service entry must have helped Avro with its OR.330 submission, the 730.

The Avro 730 started off as a four jet unswept canard, with the Armstrong Siddeley P.159 engines mounted in vertical pairs, in pods, at the tips of the trapezoidal wings. The undercarriage utilised a single main bogie with four wheels, along with nose wheels and a pair of Lockheed U2 style outriggers in the engine nacelles. For high-weight take-offs, four extra wheels could be attached to the main bogies. These would be jettisoned just after take off.

With a length of 108.75ft (33.1m) the EE P.10 carried only 2 crew rather than the three specified, which the Ministry perceived as increasing the crew workload. The downside of the smaller airframe was reduced internal fuel capacity and inability to meet the specified range. English Electric intended gaining sufficient range to meet the specification by fitting auxiliary fuel tanks as detachable wing extensions. These extensions increased the take off weight of P.10 and would put additional strain on the undercarriage. To alleviate this, English Electric proposed fitting further wheels that were to be jettisoned after take off, with the auxiliary wing tanks jettisoned shortly after. These techniques prompted a sceptical response from the Ministry of Aviation, who considered the additional wheels to be a probable cause of aborted missions, as the landing gear could not be retracted until the auxiliary wheels had been jettisoned.

With this track record behind it, Handley Page's OR.330 submission - the HP 100 - was a 70-degree canard delta design with a single fin - offering a silhouette not dissimilar to the Swedish Saab Viggen fighter of the period - and fitted out with stations for three crew.

At 185ft (56.4m) long, the HP.100 was also the largest of the contenders, while the wingspan of 59.3ft (18.1m) was comparable with the Avro and Vickers submissions. Power was supplied by no less than twelve RB 121 turbojets. These were arranged, six on each side, in a pair of fairings under the wing's trailing edge.

Vickers' submission was unusual to say the least - with sixteen RB.121 turbojets grouped in quartets in four fairings under the wings - but one innovative feature of the Vickers SP4 was its use of endplate fins on the wings rather than a single fin on the tail. This planform with the endplate fins has appeared again and again in high-speed configurations in the years since OR.330 was drawn up.

TRIAL … AND ERROR?

The Ministry of Supply, while lauding the technically advanced English Electric design, deemed it too unconventional and foresaw difficulties in service use. The area where the Ministry was particularly scathing was the size of the airframe. The reconnaissance component of the specification for OR.330 stated that a K-band Sideways Looking Active Radar would be fitted, requiring a 50ft antenna. English Electric believed that by the time of entry into service, J-band, requiring a 35ft antenna, would be the sensor of choice. Similarly, criticism of the two-crew arrangement was again countered by English Electric's faith in future systems improvement. Despite all this the P.10 – unlike the larger contenders from Handley Page and Avro - was not capable of possible conversion to a bomber, its airframe was just too small. English Electric had been too advanced with the P.10, with the probable in service date of 1965 deemed too late for the RAF and their 1960-62 "deterrent gap".

P.10 and its innovations however would not go away. There have been suggestions that the EE P.10 could have been used as the basis for a fighter or more interestingly, as a "clandestine reconnaissance" aircraft.

The Vickers SP4, with its very unconventional configuration and no less than 16 engines probably fell at the maintenance hurdle.

A NEW CHALLENGE FOR AVRO

This left the two large contenders, HP.100 and the Avro 730. Both designs underwent extensive wind tunnel testing and eventually a full scale mock up of the HP.100 was built. However, the Avro 730 was selected in May 1955, meeting the specification with less innovation than the P.10, but more than the HP.100.

Avro’s Type 730 was a three-man canard aircraft, 163 feet 6 inches long with a wing span of 59 feet 9 inches and a wing area of 2,000 square feet. Flying surfaces were controlled by a "fly-by-wire" system. Four Armstrong-Siddeley P.159 turbojets were mounted in wingtip pods. The "Red Drover" sideways-looking radar was to be the primary reconnaissance device and this was housed within the fuselage.

The undercarriage was dependent on the take-off weight. For weights up to 158,000 pounds, the standard landing gear was to be used. Weights up to 200,000 pounds required additional main wheels to be added to the main undercarriage leg. Both the nose and main undercarriage were mounted on the fuselage with outriggers on the engine pods. Take-off runs were estimated to be within 2,230 yards at which time the 730 would be at 50 feet altitude. Landing distance would be 1,150 yards with a 24 feet diameter brake chute deployed. Initial climb rate was to be 12,300 feet per minute. The first flight would be in 1959 with the eighth and last flying prototype projected to be in use by December 1961.

In October 1955 however the specification had been renumbered as RB.156D to place much more emphasis on the bomber role to meet new Operational Requirement .336. Avro had originally suggested that the 730 could be used in the bomber role as well as a reconnaissance aircraft and this development meant that the 730 was now to be a direct successor to the Vulcan.

By a stroke of luck the "Red Drover" radar antenna had by this time been shortened, which allowed a bomb bay to be installed in the increased-diameter fuselage to house a new one-megaton stand-off missile of 50 feet length.

The 35 feet long Blue Steel missile was powered by a Bristol Siddeley Stentor rocket motor

Despite its anticipated Mach 3 performance, British defence planners still recognised that the new Avro 730 could be vulnerable to increasingly sophisticated Soviet defences en route to dropping a free fall nuclear device directly over a target. Surface to air ( SAM ) missiles with new solid fuel rocket motors posed a new threat to existing V bombers and Strategic Air Command B-52s alike, while Sukhoi and MiG fighters grew ever faster and capable of reaching new altitudes.

Following on from radar countermeasures developed during the Second World War, the RAF's V-bombers carried Air Electronics Officers to operate both radar warning receivers and jamming devices. The latter could inhibit both fighter and SAM guidance radar frequencies ( a Soviet SAM needing at least 60 seconds of uninterruped data to lock on to a target ) and also broadcast a high pitched whine on the radio channels used by fighter controllers to talk to their fighter pilots. This was particularly important as Soviet defence thinking placed more emphasis on decisions made by ground based controllers than by the pilots themselves.

Beyond the use of active devices, V-bombers could still confuse opposing radar by dropping strips of aluminium "chaff" foil - and the large delta wings of the Avro Vulcan in particular helped it to out-turn fighters at high altitude. However, both existing and projected manned bombers could be given the same certain warhead delivery as the intercontinental missiles then under development by the use of stand-off systems.

The stand-off missile concept had been pioneered by the wartime Luftwaffe when it had used manned bombers - flying over the North Sea beyond the reach of RAF Fighter Command - to launch V-1 pulse-jet cruise missiles at Greater Manchester. As early as 1949 Vickers had drawn up plans for a stand -off missile code named Blue Boar guided by a television camera mounted its nose. However, in 1954 this concept was superceded by a more reliable jam-proof inertially-guided missile named Blue Steel. With a 100 - 200 mile range courtesy of its liquid fuelled Bristol Siddeley Stentor rocket motor, the Avro built Blue Steel could fly to its target - following pre-release updates from its parent aircraft's navigation system - at Mach 3 and allow - for example - an attack on Leningrad by a Victor or Vulcan flying comparatively safely over the Baltic Sea.

The use of stand-off missiles also eliminated the risk of the bomber crew being blinded and burned by the flash from their own free-fall nuclear weapon. Nevertheless, a thermal shield to protect pilots in such an instance was pioneered by American inventor KP Rice, who also designed multiple carriage bomb racks and the 0V-10 Bronco counter insurgency aircraft.

However, the one megaton thermonuclear yield Blue Steel was 35 feet long and required new generations of Victor and Vulcan bombers to carry it. The Victor B2 featured Rolls Royce Conway engines with double the thrust of the earlier Armstrong Siddeley Sapphire turbines while the Vulcan B2 was easily distinguished by a larger ogive delta ( kinked edge ) wing housing Bristol Olympus 201 engines of 18 000 lb thrust apiece. The first Vulcan B2 to enter RAF service arrived at Waddington, Lincolnshire, in 1960 while - following five years of tests - Blue Steel first became operational under the same manufacturer's "tin triangles" with 617 Squadron in February 1963. The first Blue Steel Victor unit was 139 Squadron in September that year, although once again the first Blue Steel test releases in 1958 at the Weapons Research Establishment at Woomera were from Valiant aircraft.

Also working at the South Australian proving range were Bristol Type 170 Freighters of the Royal Australian Air Force while another Bristolian link was the use of Filton aerodrome as a dispersal field for V-bombers. In times of international tension - such as the October 1962 Cuban Missile Crisis - the four engined white bombers could be stationed away from their main bases to make them less vulnerable to a pre-emptive Soviet missile strike.

Indeed, as the Blue Steel missile started to equip Victor and Vulcan squadrons across RAF Bomber Command another high speed ogive delta aircraft was being assembled at the former Bristol Aircraft Company base at Filton - the British Aircraft Corporation / Aerospatiale Concorde.

And for me too there is another strong connection between Gloucestershire, Concorde and the Avro Vulcan because I saw the British prototype supersonic airliner for the first time - or rather a part of it - at RAF Fairford in 1972. After much pleading, Dad agreed to drive his ten year old son down one sunny afternoon only to find the object of his hard-won income tax parked behind a hangar on the far side of the main runway. Only the tail with the word "Concorde" was visible, although there was an unexpected surprise in store. A squadron of Vulcan bombers were using Fairford while their usual runway in East Anglia was being resurfaced and they all - bar one - took off one after another as we watched. This was not just a lone air show Vulcan rolling past with the bomb bay open - impressive though that always was - but nine or ten Rolls Royce Olympus quartets powering up together. Mother - knitting in the front seat of the car - was unimpressed by the noise but I can hear that crackling, channelled thunder even now: each delta winged giant - by now camouflaged for its low level penetration role - dipping out of sight for a while at the end of the runway before leaping skywards.

Until 1963, it had also been hoped to equip some Avro Vulcans with pairs of the American built Douglas Skybolt stand off missile. Originally designed to be carried by the B52H variant of the Boeing Stratofortress, Skybolt was smaller than Blue Steel but offered a range of 1150 miles. Indeed, Avro had proposed a "Phase Six" development of the Vulcan large enough to carry six GAM-87 Skybolts. With an additional fleet of 48 of these giant delta winged bombers, the RAF would have had the option of keeping 84 Skybolts in the air at any one time. Unfortunately, however, the Skybolt programme ran into such technical difficulties that it was cancelled by the United States Congress.

The revised Avro 730 had another four engines – now upgraded to the Armstrong Siddeley P176 -added making a total of eight housed in two pods, an increased wing area (2,100 square feet), an increased fuselage diameter of just under 10 feet and reduced fuselage length of 159 feet.

Each quartet of engines was mounted in a new nacelle, with a shock cone intake, at approximately 2/3 span of a redesigned wing. The wing gained a highly swept section outboard of the engine nacelles. The intention was to develop the Avro 730 with the aid of a 3/8 scale manned analogue, the 731. The Avro 731 shared the basic planform of the original 730, but with a single crew station and Gyron Junior engines. The 731 was not proceeded with, but when the definitive planform for the 730 was settled, it was tested on the Bristol Type188. Bristols used the same planform as the Avro 730, but opted for a more conventional T tail.

The first 730 fuselage was well advanced at Avro's Chadderton factory when, in 1957, Duncan Sandys announced his decision to cancel all work on the majority of manned aircraft. The 730 was broken up and the World's first Mach 2+ bomber ended up being used as scrap bins. Without the Avro 730, Britain’s large high-speed military aircraft development was dead. Of so many promising designs, only the English Electric Lightning was spared as it was so near to service entry and Vickers and English Electric ( along with Bristol ) were forced into a not always happy union as the British Aircraft Corporation to build the TSR2. The Tactical Strike and Reconnaissance 2 with its two crew and two Bristol Olympus engines is widely regarded as the best warplane that Britain never had. It was cancelled in 1965 by the incoming Labour Government who then spent even more money than TSR2’s development budget on buying American aircraft such as the McDonnell Douglas F4 Phantom for the RAF.

Ironically, work on the Bristol Type 188, planned as a flying test-bed for the 730, was allowed to continue and it flew for the first time on 14 April 1962. It was used to investigate kinetic heating on airframes as part of the Anglo-French Concorde project.

In the same month, the first Lockheed SR-71 "Blackbird" flew. This Mach 3 strategic reconnaissance aircraft would continue its investigations into the USSR, China and the Middle East until the 1990s. Despite the loss of Gary Power’s U2 – shot down from 68 000 feet over Sverdlovsk in 1960, no SR-71 was ever lost due to enemy action.

By a twist of fate too, the Soviet Union was working on an aircraft with almost the same performance and layout as the 730 until it was cancelled in the late 1960s. If the Soviet Air Force had flown this aircraft the RAF would have been in the strange situation of intercepting the aircraft that they had specified in 1954!

As it was, the Soviet Air Force was to fly the supersonic Tupolev Tu22 (NATO code name Blinder ) from the early 1960s with the swing wing Tupolev Tu-22M (NATO code name Backfire ) following in 1970 and Tupolev Tu-160 ( NATO Code name Blackjack and very similar to the Rockwell B-1B Lancer ) from 1988.

NORTH AMERICAN VALKYRIE – A PARALLEL LIFE

Just as the British Aircraft Corporation’s TSR 2 would be rivalled by the General Dynamics F-111 and Concorde face initial competition from the Boeing 2707-300, America also came close to developing its own equivalent to the Avro 730 – the North American Valkyrie.

Just as the Avro 730 was seen as a possible successor the Avro Vulcan, so the Valkyrie was planned as a replacement for the Boeing B-52 after 1965. General Operational Requirement GOR-38 was issued on 14 October 1954 for an intercontinental range piloted bomber ( later designated WS-110A ) capable of a sustained Mach 0.9 and a supersonic dash through enemy airspace. Interestingly, a reconnaissance version was also considered but further research into this was cancelled in July 1956.

Initial design studies by both Boeing and North American both involved large fuel tanks on jettisonable outer wing panels to give the necessary range, although this prohibitively expensive feature was left out of North American’s winning NA-329 submission of December 1957. Despite being capable of Mach 3 however, North American’s Valkyrie programme was cut back to just one XB-70A prototype on 3 December 1959 as land and submarine based intercontinental ballistic missiles were by then seen as a more elegant and credible deterrent. Unlike manned bombers, for example, missiles would not need to be refuelled in mid air – a potentially dangerous manoeuvre for a nuclear bomber.

Notwithstanding its lack of operational role, March 1963 saw two prototypes ordered for hypersonic research and to keep America ahead in the field of inertial navigation and bombing systems. The first of these was rolled out on 11 May 1964 and first flew on 21 September.

Like the Bristol 188 – then just finishing its active life – the XB-70 was a superlative vehicle. Six General Electric YJ93-GE-3 engines – each generating 31 000 lb static thrust – made it the most powerful aircraft ever flown. These in turn were fed by wing and fuselage tanks holding a total of 300 000 lb of fuel pressurised by nitrogen. The wingtips themselves could be folded down to 25 degrees below horizontal for low level supersonic flight and down to 65 degrees for flying faster than sound at high altitude. At Mach 3, the Valkyrie was designed to ride its own shock wave, a phenomenon also explored by British aerodynamicists in the 1960s.

To cope with the heat generated at hypersonic speed, the XB-70’s wings – swept to just over 65 degrees - were built out of titanium and brazed stainless steel honeycomb ( a similar construction technique to that used on the Bristol Type188 and Handley Page Victor) and could withstand temperatures of 332 degrees centigrade. Like the Bristol 188 too, most of the fuselage was built of stainless steel although the front section was made of titanium and featured – like the production variants of Concorde - a fixed inner and moveable outer windscreen.

The XB-70 was 196’ long, 105’ wide with wing tips fully spread, 30’ tall and had an expected range of 7 600 miles and ceiling of 73 980’. The cabin for the pilot, co-pilot, bombardier-navigator and defensive systems operator was air-conditioned and each seat formed a self-contained emergency ejection capsule. No bulky pressure suits were thus required, as in the event of pressure loss the crew could simply "encapsulate" and using minimum flying controls – still accessible – descend to a safe un-pressurised altitude.

The first XB-70A ( 62-001 ) first broke the sound barrier on 12 October 1964 ( and exceeded Mach 3 a year and two days later ) while the second machine ( numbered 62-207 ) first flew on 18 July 1965. Sadly, the latter Valkyrie crashed with the loss of its co-pilot on 8 June 1966 during a aerial photo shoot of aircraft fitted with General Electric engines. This left 62-001 to continue expensive but valuable high speed test flying until its retirement to the USAF Museum at Wright-Patterson Air Force Base, Ohio on 4 February 1969.

By then Britain's V-Force had been reconfigured to attack at low level under Soviet radar and future nuclear bomber designs were to be based either on this "hedge-hopping" approach or, like the Northrop B-2 Spirit, use Stealth technology to avoid detection by enemies.