The concept of target-marking had been proved with great success by the RAF of World War Two, but how would it translate to the jet bomber age? The Vickers Valiant was chosen to lead the role into this new era. Why, then, did the menacing and very capable ‘Black Bomber’, the Valiant B2, end up being a one-off?
In the RAF of the 1950s, thanks to being tasked with the carriage of the nuclear deterrent in the shape of Blue Danube, Bomber Command received the latest kit. His Majesty’s Government had invested a king’s ransom in Blue Danube since its development had begun, in complete secrecy, under the orders of Clement Attlee on 10 August 1945. Blue Danube would require a delivery system and the Attlee administration embarked on the development of four bombers: the Valiant, the Vulcan, the Victor and, as insurance, the Sperrin.
However, in the immediate post-war period, the availability of a British nuclear weapon was not guaranteed and, with the possibility of a ‘limited war’, there was a need for conventional bombing. Bombing and navigation aids were effectively the same as those used during World War Two, but the scale of the operations had changed: fewer aircraft over greater distances. Therefore, to ensure the effective use of limited resources, target-marking was adopted for the medium bomber force.
Bomber Command’s Pathfinder units were the elite, the first to use the newest bombing aids and developers of tactics such as sky marking. They also introduced the master bomber, epitomised by Gp Capt Leonard Cheshire coordinating a raid on a V1 storage depot at Siracourt by flying at low level in a Mustang he had ‘acquired’ from the US Army Air Forces (see Aeroplane May 2018). By the end of the war Bomber Command could send hundreds of aeroplanes to eastern Germany and lay waste to a city.
Why, with one bomber capable of devastating cities, did the ‘V-Force’ need a pathfinder/target-marker in the first place? Having spent six years bombing targets in Europe, where the maps were accurate and photographic coverage total and constantly updated, the Soviet Union posed a peculiar problem. Bomber Command would be heading for targets for which, in the early 1950s, it had little or no detailed map coverage. This was compounded by the weather over the Soviet Union, which would render the TV-guided Blue Boar bomb useless, with low cloudbases and poor visibility for much of the year. There was also the small matter that British nuclear weapons were scarce and expensive. Every bomb should count.
The Air Staff took the view that target-marking, for conventional bombing at least, would continue in the same manner, using techniques similar to those employed in World War Two. These methods would include a target-marker operating in the same manner Leonard Cheshire had with his Mosquito and Mustang. The target-markers would lead the way to the target, descend to low level, find the target, mark it and co-ordinate the raid. When the ‘V-bombers’ were being developed the Air Staff soon realised that the target-marker aircraft under development at the time, a version of the English Electric Canberra to meet specification B22/48, “did not have sufficient range to match” that of the ‘V-bombers’. Therefore, a new high-performance target-marker was required. Discussions by the Operation Requirements Committee (ORC) centred on the changes required to the new medium bomber designs, specifically for low-level operations.
The Air Staff on 1 July 1950 issued a requirement, OR285, and attendant specification B104D for a medium-range targetmarker aircraft that was to have “comparable endurance to the B9/48 and the B35/46 medium bombers to locate and mark a precise target from low or high altitude”. Specific cation B9/48 was written around the Vickers Type 660 (Valiant) while B35/46 was met by the Avro 698 (Vulcan) and Handley Page HP80 (Victor). These specific cations were issued in 1948 and 1946 respectively, so fell under the Air Ministry’s original role/specific cation number/year nomenclature, while the targetmarker, B104D, used the new post- 1950 role/spec number system.
Take-off performance was such that “rocket assistance or reheat is acceptable”. The aircraft was to be capable of cruising at 450kt at 45,000ft, with a ceiling of at least 50,000ft. In addition to carrying out target-marking, the “design should permit rapid conversion to the normal bomber role”. Its still-air range was to be at least 3,350nm including a descent to the target, which may require flight at “near ground level” and 30 minutes’ search at maximum continuous thrust before marking the target, followed by a “climb at maximum continuous thrust” from near ground level at the target to cruising altitude. When range was discussed, it was pointed out that every mile spent on maximum thrust at low altitude equated to four miles knocked off the range at cruising speed.
The requirement further stated that the aircraft was to be capable of delivering target-markers at angles of up to 30°. During such diving attacks the bomb-aimer’s view of the target would be obscured, so “target markers will be aimed by the pilot” and released using a button on the control column. Thus the aircraft was to be fitted with a “means of rapid deceleration from service limited diving speed to cruising speed at low altitude” — dive brakes.
For target-marking by level bombing, a visual bombsight or H2S Mk2 was to be used rather than H2S Mk9. The latter was not thought suitable as it was designed for high altitude and was therefore “unsuitable at heights between 500 and 7,000ft”, although there was hope for a Q-band variant. The Telecommunications Research Establishment advised, “It is not possible to design a single H2S bombing equipment covering the full range of height from 500- 50,000ft”, which was problematic for an aircraft that could be required to bomb from any height. This may explain the need for a targetmarking aircraft in the first place. Another consideration would be the fact that there would be no ‘radar pictures’ of potential targets that the Main Force could use. These were photographs of the radar display issued to the navigator (radar) to compare with the image being displayed on the H2S display as the bomber approached the target. The acquisition of such radar pictures was the basis of the OR330/R156 Mach 3 reconnaissance aircraft, the Avro 730, soon revised as the RB156/ OR336 supersonic bomber.
The load for target-marking was to be four 1,000lb target-markers, four 1,000lb flare clusters, or a combination of these to a maximum load of 6,000lb with the remainder of the bomb bay space taken up with fuel. Other weapons for the bomber role were to be the ‘Special Bomb’ or the Blue Boar guided bomb. A pair of the 5,000lb Blue Boars or a single 10,000lb version could be carried.
The original specification had stated that the requirement “excludes any entirely fresh project and presupposes that the requirement must be met by conversion of a type already under development”. Bristol Aircraft at Filton probably missed that memo but took the view that OR285 was best served by a small aircraft and responded with the ‘V-bomber’ equivalent of Cheshire’s Mustang.
In April 1950 it submitted a brochure for the RA6, a single-seat long-range target-marker with a cruising speed of 505kt at 42,000ft while carrying 1,200lb of stores to a target 2,500nm away. To mark the target the RA6 would descend to 5,000ft, search for 20 minutes, mark the target and climb to 40,000ft for the return to base. However, the Air Staff were not very enthusiastic about starting development of a new type in the economic climate of the time.
OPERATING THE B2
Handley Page proposed in February 1951 a target-marker version of the HP80 Victor, designated HP98. It said the airframe and “aerodynamic features are identical” with the HP80 and “in principle, its structural design is the same”. Where it did differ was in the “large airbrakes” that “permit rapid deceleration” and “allow dives up to 34° at 15,000ft and up to 57° at 5,000ft to deliver target-markers in a dive”. The HP80 already possessed large airbrakes on either side of the tail cone/extreme rear fuselage, and which did not produce any trim changes when opened. How the HP98 was to be fitted with “enlarged airbrakes” is not described in the brochure. It was to have additional fuel in the bomb bay, plus the usual load of target-markers, and the option to carry a full bomb load as a low-level bomber.
The Bristol RA6 was to be powered by a pair of scaled-down Bristol Olympus engines rated at 4,400lbf, mounted in underwing nacelles under the swept, high-aspect ratio wings, with a wing sweep of 45°. The wing loading was computed at 96lb per sq ft, which was high, and at the all-up weight of 54,000lb would require rocket-assisted take-off (RATO). This took the form of eight solid rocket motors in vertically stacked pairs, with four rockets on each side of the fuselage just aft of the wing root trailing edge. The stores were to comprise 1,000lb of target markers and 200lb of flares and photo-flashes. To meet the range requirement the RA6 could be fitted with two drop tanks, carried at the four and eight o’clock positions on the fuselage at the centre of gravity. The Air Staff’s desire for marking in a dive was more easily met by Bristol, which fitted the RA6 with large dive brakes on the rear fuselage, while the cockpit afforded an excellent view of the target.
Bristol also suggested a version that used an existing engine, the Armstrong Siddeley Sapphire rated at 7,300lbf, but this would be a larger aircraft with an all-up weight of 73,000lb. This would have a higher cruising altitude of 44,000ft and a higher payload, carrying 2,700lb of stores. The manufacturer further described a slightly smaller version, the RA4, with an even higher wing loading of 108lb per sq ft and less equipment, for an all-up weight of 51,400lb.
Handley Page estimated that, with Conway or Olympus engines, the HP98 could achieve a cruise speed of 500kt, at altitudes of up to 47,000ft with Conways. At low altitude it calculated that the aircraft could reach 580kt during the 30 minutes of target search at 5,000ft. This was the ‘economic’ speed as Handley Page advised that the HP98 was good for 600kt at low level. As with the RA6, the HP98 did not progress.
Like the Victor, the Vulcan would not need a lot of structural modification for the target-marker role. Its delta wing possessed the inherent strength that made the configuration attractive to designers. The draft requirement had stated a cruising speed of 475kt, but parametric studies showed a targetmarker version of the Vulcan could not achieve the speed requirement while the Valiant could — “just”. Nor could the Vulcan meet the 45,000ft cruising altitude, but it must be noted that these studies were based on the Vulcan with Sapphire, not Olympus, engines. The ORC noted that the bomb-aimer’s station on the Vulcan was only usable when the aircraft was horizontal! The Vulcan’s manoeuvrability would have been ideal for the target-marking role, but the Air Staff were not interested. Why did the Valiant become the aircraft of choice?
The Air Staff reasoned that neither the Vulcan nor the Victor would be entering production until late 1954, at the earliest for the Vulcan, with a target-marker variant lagging a year behind that. There was also a desire to produce the target-marker and the bomber concurrently — if possible, one target-marker for every 10 bombers. Agility at low altitude was debated, as a Valiant could not be expected to manoeuvre like the Mosquitos used for wartime marking. There were fears that, as Cheshire had found with the Lancaster, the Valiant was not up to the job due to poor lowaltitude manoeuvrability. A turning circle of 1.5 miles at 500kt was thought feasible, but whether that would provide “the view required for low altitude visual marking” was unknown. Either way, the concern was whether the Valiant B1 would have the structural strength required for rigorous manoeuvres at 5,000ft. Time would prove that it didn’t.
The Valiant would be available earlier — the first production example flew in December 1953 — and so was selected to form the basis of the target-marker aircraft to meet Air Staff Requirement OR285. Vickers submitted its brochure for OR285 in September 1950 and Air Ministry specification B104P covering production of 15 targetmarker/ pathfinder aircraft, with two prototypes for development flying, was issued in November 1951. As noted above, in addition to the 6,000lb of target-markers, Vickers stated that the B104P aircraft could carry the same payload as the Valiant B1, which was up to 41,000lb and thus could operate as a lowaltitude bomber.
Work began on what became known as the Vickers Type 673. To cope with the stress of the lowaltitude environment the Valiant would require modification. The most obvious change was to the wing, which gained a large trailingedge sponson just outboard of the engines to house a new, rearwards-retracting, four-wheel bogie undercarriage. The reason for changing the undercarriage from an outwards-retracting tandem pair to the bogie was to avoid potential weaknesses in the wing structure such as the undercarriage wells outboard of the engine bays on the B1’s wing. By moving the undercarriage into a trailing-edge sponson, the aircraft’s centre of gravity moved aft, countered by a 4ft 6in extension forward of the wing, which provided space for additional equipment.
The result was the Valiant B2 and the first of two planned prototypes, WJ954, took to the air on 4 September 1953. ‘Jock’ Bryce and Brian Trubshaw were at the controls. With its gloss black finish, it soon acquired the moniker ‘Black Bomber’. Thanks to its revised structure the B2 was cleared to fly faster at low level than the B1, and this performance would probably improve with the advent of the second prototype fitted with Rolls-Royce Conway turbofans, as on the Victor, that were intended for the 15 production B2s.
It was not to be. The Valiant B2 to meet specification B104P was cancelled in August 1953, even before the first example took to the air. There was, the Air Ministry decided, no need for a dedicated pathfinder. WJ954, therefore, was used for trials work in support of the Valiant B1 programme. In test flights the B2 was found to be “flutter free up to 480kt”, while further sorties investigated the effects of vibration on the rear fuselage, examination of buffet characteristics and flight on three engines. In one sortie on 16 December 1953, WJ954 was dived from 46,000ft and achieved a maximum Mach number of 0.905 at 40,500ft, reaching a vertical speed of 8,000ft per minute. Early the following year it was fitted with an in-flight refuelling probe and used for trials with Flight Refuelling’s Canberra B2 WH734, although these mainly involved ‘dry’ contacts.
Appearing at the 1954 SBAC Farnborough show, WJ954 was demonstrated at high speed and low level, attaining 480kt on one flypast. It subsequently conducted tests with the de Havilland Sprite rocket engine in support of the Valiant B1’s use of RATO (rocket-assisted take-offs). On 6 October 1954 the starboard Sprite unit broke away from its mounting, forcing the pilot to jettison it to avoid asymmetric thrust. This caused damage to the airframe, the starboard undercarriage and its nacelle. The incident revealed problems with the RATO unit release system, and the damage to the starboard undercarriage bogie resulted in ongoing maladies with the wheel braking system.
In April 1956 WJ954 was being used for fuelling trials with the RAF including fuel tank inert gas purging. Having completed 167 hours 35 minutes of flying by May 1958, WJ954 was dismantled at Vickers’ Wisley works. It was taken to the range at Foulness, where it was destroyed during weapon trials.
By October 1956 a Valiant B1 had dropped the first Blue Danube bomb, making the target-marker for the ‘V-Force’ irrelevant in the nuclear era. Pathfinders had been superseded by the forthcoming R156/OR330, the Mach 3 radar reconnaissance aircraft tasked with gathering targeting data to be used by the ‘V-bombers’. Then, over Sverdlovsk on May Day 1960, a swarm of missiles climbed towards a high-flying aircraft. Perhaps the RAF could have used the Valiant B2 after all.
The author thanks Dave Forster and James Jackson.