Il Vickers Valiant (in inglese, Valoroso) era un bombardiere strategico inglese degli anni cinquanta.
Nato in risposta alla Specifica B.35/46, fu il primo dei quadrigetto divenuti famosi, in base all'iniziale dei rispettivi nomi, come V-Bombers (gli altri velivoli della classe furono l'Avro Vulcan ed l'Handley Page HP.80 Victor).
Operativo tra il 1955 ed il 1965, fu protagonista dei primi lanci da un aereo di una bomba atomica inglese (sito di Maralinga, Australia, ottobre del 1956) e della prima bomba all'idrogeno inglese (Oceano Pacifico, maggio del 1957).
Storia del progetto
Nell'immediato dopoguerra il Regno Unito considerava primario mantenere una forza aerea strategica che potesse fungere da deterrente nei confronti del potenziale nemico; a questo scopo la Royal Air Force mise in linea il quadrimotore Avro Lincoln (diretto sviluppo dell'Avro Lancaster) motorizzato, tuttavia, ancora da motori a pistoni.
Lo sviluppo tecnologico, legato in particolare al motore turbogetto ed alla bomba atomica, rese necessaria la realizzazione di una nuova generazione di velivoli che consentisse agli inglesi il mantenimento di tale forza di deterrenza.
Il primo progetto in risposta alla specifica per questo nuovo velivolo venne dalla Vickers: pur non rispettando in pieno le caratteristiche richieste, lo sviluppo procedette (in base ad una nuova richiesta specifica, la B.9/48), in virtù della possibilità di una più rapida realizzazione, in attesa dei velivoli più sofisticati ed ambiziosi realizzati dalle case costruttrici concorrenti.
Nacque così il progetto Vickers Type 660, la cui motorizzazione era affidata a quattro Rolls-Royce Avon RA.3, mentre un secondo prototipo, cui venne assegnato il codice interno Type 667, avrebbe dovuto avere motori Armstrong Siddeley Sapphire.
Il primo prototipo volò per la prima volta il 18 maggio 1951; andò tuttavia distrutto, a causa di un incendio dovuto ad un guasto al circuito di alimentazione dei motori. Dopo le opportune modifiche il secondo prototipo, i cui motori erano nel frattempo stati sostituiti con i Rolls-Royce Avon RA.7, volò l'11 aprile 1952.
Il Type 660 aveva nel frattempo ricevuto la denominazione ufficiale di Valiant (scelto mediante un sondaggio svolto internamente alla Vickers) interrompendo una tradizione consolidata che voleva i bombardieri strategici individuati con nomi di città.
Il primo ordine per la produzione di serie arrivò nell'aprile del 1951, quando ancora non era stato effettuato il primo volo, ed il primo Valiant B.1 volò nel dicembre del 1953.
Tecnica
Il Valiant era un monoplano ad ala alta, con angolo di freccia composito; l'equipaggio, formato da 5 elementi, era alloggiato in una cabina di pilotaggio pressurizzata.
I quattro motori turbogetto erano annegati, due per parte, alla radice delle semiali; si trattava di turbogetti Rolls-Royce Avon che fornivano una spinta di poco superiore ai 44 kN.
L'armamento era costituito da carichi di caduta fino ad un massimo di 21 000 lb ed era prevista la possibilità di trasportare ordigni nucleari.
Impiego operativo
Entrato in servizio nel corso del 1955, il Valiant fece parlare di sé per una impressionante parata alla Mostra internazionale e esposizione di volo di Farnborough del settembre del medesimo anno: in quell'occasione si esibì una formazione composta da ben 12 velivoli del 138º Squadron della RAF.
Sul finire del 1956 i Valiant ebbero la loro unica occasione di intervento in azioni di guerra, prendendo parte alle operazioni nel corso della Crisi di Suez.
Al momento dell'entrata in servizio dei Vulcan (prima) e dei Victor (poi), i Valiant vennero destinati, di prevalenza, al ruolo di aerocisterna.
Nel corso del 1964, al variare delle necessità strategiche determinate dall'entrata in servizio dei missili balistici (in particolare i UGM-27 Polaris), il Bomber Command tentò la riconversione dei Valiant in bombardieri da bassa quota. In questo caso, contrariamente a quanto avvenuto con il Vulcan, la transizione non ebbe esito felice in quanto emersero problemi di solidità strutturale che interessarono principalmente il longherone dell'ala. Di fronte a questi problemi la RAF dispose, nel gennaio del 1965, il ritiro dal servizio dei Valiant.
Versioni
- B.1 (Type 706): prima versione di serie, destinata al ruolo esclusivo di bombardiere. Venne prodotta complessivamente in 36 esemplari (compresi 5 di pre-serie, Type 674). Un B.1 venne impiegato come base di collaudo per la turboventola Rolls-Royce Pegasus;
- B(PR).1 (Type 710): prima versione multiruolo; affiancava la possibilità d'impiego come bombardiere a quella di ricognitore. Ne furono costruiti 11 esemplari;
- B(PR) K.1 (Type 733): serie di 13 esemplari che, in aggiunta alle funzioni della versione precedente, affiancava la possibilità di assolvere il compito di aerocisterna;
- BK.1 (Type 758): versione studiata per l'impiego come bombardiere o aerocisterna; venne realizzata in 44 unità;
- B.2: singolo prototipo, frutto di un'estesa revisione del progetto iniziale (con ampie modifiche al muso, all'ala ed al carrello), era destinato allo sviluppo di una versione espressamente destinata al bombardamento a bassa quota; malgrado prestazioni sensibilmente migliori rispetto alle versioni iniziali, non ebbe seguito produttivo.
Utilizzatori
- Regno Unito - Royal Air Force.
ENGLISH
The Vickers-Armstrongs Valiant is a British high-altitude jet bomber, and was part of the Royal Air Force's "V bomber" nuclear weapon equipped strategic deterrent in the 1950s and 1960s. It was developed by Vickers in response to Specification B.35/46 issued by the Air Ministry for a nuclear-armed jet-powered bomber. The Valiant was the first of the V bombers to become operational, and was followed by the Handley Page Victor and the Avro Vulcan, which were more advanced. The Valiant has the distinction of being the only V bomber to have dropped live nuclear weapons.
The Valiant was intended as a high-altitude strategic bomber. During the late 1950s, in response to rapid advances in surface-to-air missile (SAM) technology, the Valiant fleet was switched to flying low-level for the strike role. Beyond the nuclear deterrence role, the Valiant was also used by the RAF for other purposes, as a number were converted to perform support roles such as aerial refuelling tankers and aerial reconnaissance aircraft. Valiants were used for conventional bombing missions over Egypt for Operation Musketeer during the Suez Crisis of 1956.
By late 1964 it was found that all variants of the Valiant showed premature fatigue and inter-crystalline corrosion in wing spar attachment forgings, traced to the use of a poorly understood aluminium alloy, DTD683. Rather than proceeding with an expensive rebuilding program, the Ministry of Defence retired the Valiant in 1965. Its duties were continued by the other V-bombers which remained in service until the 1980s.
Development
Background and origins
In November 1944, the Joint Technical Warfare Committee, along with a separate committee chaired by Sir Henry Tizard, examined the future potential of "weapons of war" and the accompanying Tizard Report published on 3 July 1945 made specific policy directions for the Royal Air Force (RAF) Bomber Command.[4] After the Second World War, the policy of using heavy four-engined bombers for massed raids continued into the immediate postwar period; the Avro Lincoln, an updated version of the Avro Lancaster, became the RAF's standard bomber. In 1946, the Air Staff issued Operational Requirements OR229 and OR230 for the development of turbojet-powered heavy bombers capable of carrying nuclear weapons at high altitude and speed, without defensive armament, to act as a deterrent to hostile powers and, if deterrence failed, to perform a nuclear strike. In conjunction with this ambition, Britain set about developing its own atomic weapons.
In January 1947, the British Air Ministry issued Specification B.35/46 for an advanced jet bomber intended to carry nuclear weapons and to fly near the speed of sound at altitudes of 50,000 ft (15,000 m). Three firms: A.V. Roe, Handley-Page and Vickers-Armstrongs submitted advanced designs intended to meet the stringent requirements. While Short Brothers submitted a design, by Geoffrey T. R. Hill, that was judged too ambitious, the Air Staff accepted another submission from the company for a separate requirement, B.14/46, as "insurance" in case the advanced B.35/46 effort ran into trouble. Aviation authors Bill Gunston and Peter Gilchrist described Specification B.14/46 as "calling for little more than a traditional aircraft fitted with jet engines" Short submitted a conservative design to meet B.14/46, which became the S.A.4 Sperrin. Two prototypes were completed, the first conducting its maiden flight in 1951, but the Sperrin was ultimately relegated to research and development purposes only.
Vickers had emerged from the Second World War as one of the world's pre-eminent companies in the field of aeronautical manufacturing and development. Furthermore, the company operated its own secretive Skunk Works-like development organisation based at Weybridge, Surrey, which had been involved in several secret wartime development projects. It was this secretive division in which the early stages of the development of the Valiant took place, including the later assembly of the initial two prototypes. Vickers initially produced a six-engine jet bomber design proposal to meet Specification B.35/46; as rapid progress in the development of more powerful jet engines had been made, this was re-worked to a four-engine proposal in 1948.[12] The proposed design submitted by Vickers was relatively straightforward, being less aerodynamically advanced in comparison to competing bids made by rival firms.
Both Handley-Page and Avro had produced advanced designs for the bomber competition. These would be produced as the Victor and the Vulcan respectively; the Air Staff decided to award contracts to each company as a form of insurance in case one of these designs failed. The submissions became known as the V bombers, or V-class, with the aircraft all being given names that started with the letter "V". Vickers' submission had initially been rejected as not being as advanced as the Victor and the Vulcan, but Vickers' chief designer George Edwards lobbied the Air Ministry on the basis that it would be available much sooner than the competition, going so far as to promise that a flight-capable prototype would be flown by the end of 1951, that subsequent production aircraft would be flown prior to the end of 1953, and that serial deliveries would commence during early 1955. Gunston and Gilchrist observe that measures offered by Edwards were a "gigantic risk", and that gaining the bomber contract has been deemed of crucial importance to the future of aircraft manufacturing at Vickers.
Although developing and operating three overlapping large aircraft in response to a single Operational Requirement (OR) was wasteful and very costly, events such as the Berlin Blockade had led to officials placing a sense of urgency in the necessity to provide an effective deterrent to the Soviet Union from acts of aggression in Europe. In April 1948, the Air Staff issued a specification with the designation B.9/48 written around the Vickers design, which was given the company designation of Type 660; an 'Instruction to Proceed' was received by Vickers on 16 April 1948. In February 1949, two prototypes of the aircraft were ordered. The first of these was to be fitted with four Rolls-Royce RA.3 Avon turbojet engines, while the second was to be fitted with four Armstrong Siddeley Sapphire engines as the Type 667.
Prototypes
On 18 May 1951, the first prototype, serial number WB210 took to the air for its maiden flight, within the deadline that George Edwards had promised, and preceding the first Short Sperrin into the air by several months, it being only 27 months since the contract had been issued. The pilot was Captain Joseph "Mutt" Summers, who had also been the original test pilot on the Supermarine Spitfire, and wanted to add another "first" to his record before he retired. His co-pilot on the first flight was Gabe "Jock" Bryce, who succeeded Summers as Vickers' chief test pilot upon his retirement shortly afterwards. The next month, the Vickers Type 660 was given the official name of "Valiant", recycling the name given to the Vickers Type 131 general-purpose biplane of 1931. The name Valiant had been selected by a survey of Vickers employees.
On 11 January 1952, the first Valiant prototype was lost while making internal noise measurements for the V.1000 programme. Testing included engine shutdowns and re-lights, one of which caused a fire in the starboard wing; most of the crew managed to escape the aircraft safely, except for the co-pilot, who struck the tail after ejecting. After modifications to the fuel system the second prototype, serial number WB215, the Vickers Type 667, conducted its maiden flight on 11 April 1952. It was fitted with more powerful RA.7 Avon engines with 7,500 pounds-force (33 kN) thrust each, rather than the Sapphires that had been originally planned; it also featured more rounded air inlets, replacing the narrow slot-type intakes of the first prototype, in order to feed sufficient air to the more powerful engines. The short delay until the second prototype became available for testing, which was accelerated by three months, meant that loss of the initial prototype did not seriously compromise the schedule.
Of the three prototypes, two were representative of the Valiant B.1, while one was built as a further developed version, referred to as the Valiant B.2. The B.2 variant was intended to serve as a Pathfinder aircraft, flying at high speed at low level to mark targets for the main bomber force. To cope with the rougher ride compared with high altitude operations, the B.2 had a strengthened airframe. In particular, the wing received design alterations to strengthen it, a key change being the removal of the large cut-outs in the wing structure into which the main wheels retracted, allowing the wing torsion box structure to be uninterrupted and giving more room for internal fuel storage; instead the main landing gear, which had four wheels instead of the two large wheels of the B.1, retracted backwards into large fairings set into the rear of the wings. The B.2 had a lengthened fuselage with a total length of 112 ft 9 in (34.37 m), in contrast to a length of 108 ft 3 in (32.99 m) for the Valiant B.1, with the extra length giving room for more avionics.
The prototype B.2, serial number WJ954 first flew on 4 September 1953. Finished in a gloss black night operations paint scheme, it became known as the "Black Bomber". Its performance at low level was superior to that of the B.1 (or any other V-bomber), being strong enough to fly at full power at sea level, with the aircraft being cleared for 580 mph (930 km/h) at low level (with speeds of up to 640 mph (1,030 km/h) being reached in testing). This was compared to the B.1's sea-level limit of 414 mph (665 km/h). The Air Ministry ordered 17 production B.2s, which were to be powered by Rolls-Royce Conway turbofans. Although the Valiant B.2's low-level capabilities later proved to be highly desirable, the B.2 program was abandoned as the RAF considered that the Pathfinder concept, born in a time of mass raids, was obsolete in the nuclear era. The B.2 prototype was used for tests for a few years, including testing use of rockets to boost takeoff, contributing to improvements for the Valiant B.1, before being scrapped in 1958.
Production
In April 1951, an initial production order for 25 Valiant B.1 (Bomber Mark 1) aircraft was placed by the Ministry of Supply on behalf of the RAF. The timing of this order was key to establishing production quickly. Due to shortages of steel and other materials while setting up an assembly line at Brooklands, substantial portions of the production jigs for the Valiant were made from concrete. The first five Valiants produced were completed to a pre-production standard, the first being WP199. On 21 December 1953, the production aircraft conducted its first flight; this had again occurred within the schedule that Edwards had promised.
On 8 February 1955, this first production Valiant was delivered to the RAF. Britain's "V-bomber" force, as it had been nicknamed in October 1952, formally entered operational service on that day. The Victor and Vulcan would soon follow the Valiant into service, for a total of three types of nuclear-armed strategic bombers in RAF service. In September 1957, the final Valiant was delivered. According to Bill Gunston and Peter Gilchrist, all production aircraft had been delivered on time and below budget.
A total of 108 Valiants were manufactured, including the sole B.2 prototype. In addition to its principal role as the RAF's delivery platform for Britain's nuclear deterrent, the Valiant bomber also dropped high explosive bombs. The bombers were followed into service by a strategic reconnaissance version and a multi-purpose version capable conventional bombing, aerial reconnaissance and aerial refuelling. One squadron operated 6 Valiants with electronic countermeasures equipment. Valiants of 90 and 214 squadrons were used for air refuelling through the addition of a Hose Drum Unit (HDU) in the bomb bay, mounted on the same suspension units that were also used for bombs. This meant that for refuelling, the bomb-bay doors had to be opened so that the refuelling hose could be streamed (unlike later tankers where the HDU was flush with the under fuselage rather than inside a bomb bay). Several Valiants were also used for testing and development purposes, such as its use as a flying testbed during trials of the Blue Steel nuclear-armed standoff missile, which was later added to the arsenal of munitions the other V-bombers were equipped with.
Unlike its Vulcan and Victor peers, the Valiant did not see the production of a refined and more capable B.2 model. Instead, the Valiant B.1 fleet was later switched to a low-level flight profile, after which fatigue due to the resulting increased turbulence was discovered and ultimately led to the type's premature retirement. Vic Flintham observed that: "There is a fine irony to the situation, for Vickers had produced the Type 673 B Mk 2 version designed as a fast, low-level pathfinder... The Air Ministry was not interested..." The Valiant was Vickers' last purpose-built military aircraft. It was followed by the Vanguard, a passenger turboprop designed in 1959, and the Vickers VC10, a jet passenger aircraft in 1962, also used as a military transport and tanker by the RAF.
Design
The Valiant was a conservative design of the era, having a shoulder-mounted wing and four Rolls-Royce Avon RA.3 turbojet engines, each providing up to 6,500 pounds-force (29 kN) of thrust, installed in pairs in fireproof bays in each wing root. The design of the Valiant gave an overall impression of a plain and clean aircraft with simple aerodynamics. George Edwards described the Valiant appropriately and simply as an "unfunny" aircraft. The root chord thickness ratio was 12% and allowed the Avon engines to be within the wing rather than on pods as in the contemporary Boeing B-47. This "buried engine" installation contributed to the aircraft's aerodynamic cleanness, and was British practice at the time. It made engine access for maintenance and repair difficult and increased the risk that an uncontained failure of one engine would cause damage to the adjacent engine; it also increased the complexity of the design of the main spar which had to be routed around the engines.
The wing of the Valiant used a "compound sweep" configuration, devised by Vickers aerodynamicist Elfyn Richards. Richards found that it would be advantageous to increase the sweep on the inboard section of the wing, a discovery which he later patented; the Valiant's wing made use of a 37° angle of sweepback for the inner third of the wing, which reduced to an angle of about 21° at the tips. This was because the thickness/chord ratio could be reduced closer to the tips, balancing this against the sweep reduction in postponement of supersonic airflow effects such as buffeting and increased drag. The choice to have mild sweepback around the aerodynamic control surfaces meant that in-service speeds were limited to Mach 0.84 and a typical cruise of Mach 0.75 at heights up to 55,000 feet (17,000 m) when lightly loaded. A drogue parachute was deemed unnecessary even operating from runways as short as 6,000 feet (1,800 m).
The wing was mounted high on the aircraft's fuselage and this created a limited fuel capacity when combined with the other necessary compromises in design such as the placement of the engines and main landing gear within the wing's internal space. The leading edge of the wing was fixed while the trailing edge incorporated large outboard two-section ailerons, the inner section featuring trim tabs, alongside double-slotted flaps again split into inboard and outboard sections. Direct electrical drives were used to move the flaps and other, usually hydraulically-operated, equipment on the aircraft.
Production aircraft were powered by four Avon 201 turbojet engines, with 9,500 pounds-force (42 kN) thrust. In addition to providing thrust for flight, the engines also provided bleed air for the pressurization, ice protection, and air conditioning systems. The aircraft's electrical generators were also driven by the engines. Napier Spraymat electric heaters were installed in the engine inlets to prevent engine damage due to ice forming on the duct surfaces and then shedding into the compressors. The shape of the engine inlets were long rectangular slots in the first prototype, while the production Valiants had oval or "spectacle" shaped inlets designed to pass greater airflow for the more powerful engines that were installed. The jet exhausts emerged from fairings above the trailing edge of the wings.
For additional takeoff performance in hot and high conditions, such as tropical climates, a jettisonable rocket booster engines pack was developed for the Valiant. Trials were performed with two underwing de Havilland Sprite boosters; these were ultimately deemed unnecessary due to the availability of more powerful variants of the Avon engine, as well as fears of potential accidents if one booster rocket failed on takeoff, resulting in asymmetric thrust. Some Valiants were powered by engines with water injection, which increased takeoff thrust by about 1,000 pounds (450 kg) per engine.
The crew of the Valiant were contained in a pressurized "egg" in the forward area of the aircraft and consisted of a pilot, co-pilot, two navigators, and an electronics operator; the manufacturing of this pressurized section was subcontracted to Saunders-Roe. The pilot and co-pilot were located on an upper level in a side-by-side arrangement akin to the flight deck of an airliner, the remaining three crewmen sat at stations set lower in the cockpit to the rear. A crew of five had been enabled by the discontinuation of defensive gun turrets and accompanying air gunners, a design philosophy proved by the successful De Havilland Mosquito bomber of World War II. The pilot and copilot were provided with Martin-Baker Mk.3 ejector seats, while the rear crewmen were expected to bail out of the oval main entrance door. It has been claimed that the survivability of the rear crewmen was substantially reduced due to the ineffectiveness of this method of escape.
The fuselage area behind the pressurised crew section and forward of the wing was used to house much of the Valiant's avionics, air conditioning, and the retractable main landing gear. The Valiant featured a tricycle landing gear arrangement, with twin-wheel nosegear and tandem-wheel main gear that retracted outwards recessed set into the wing. Each of the main gears were equipped with multipad anti-skid disc brakes, and were telescopically linked so that a single drive motor could pull them up into the wing recesses. Most of the aircraft's systems were electrically powered, including the flaps and undercarriage. The brakes and steering gear were hydraulically powered, the pumps themselves were electrically driven. The lower half of the aircraft's nose contained the scanner of a powerful H2S radar in a large glass fiber radome; in addition, a visual bomb sight was set beneath the lower floor of the pressurised section. The avionics bay could be accessed via an entrance at the base of the rear fuselage leading to an internal catwalk above the aft of the bomb bay.
The electrics were powered by 112 volt direct current generators for functions requiring large amounts of electrical power, and a 28 V DC system provided a controlling voltage for other systems and the actuators that initiated the higher-voltage system functions. Backup batteries were a bank of 24 V units and 96 V batteries. 115 V alternating current was provided to systems such as radio and radar that required it; the actuators for the flight surfaces, flaps, air brakes and undercarriage were also powered via this facility. It was decided during development that as much of the aircraft would be electrically-driven as was possible; this design choice was due to electrical cabling being lighter than its hydraulic equivalent, and the already-present high power electrical generators to meet requirements of energy-hungry equipment such as the radar.
The flight controls of the Valiant consisted of two channels of power control with full manual backup; flying in manual was allowed but limited, being intended to be used only in the event of complete electrical failure. The flight controls reportedly required considerable effort to manually operate. All three axes of the flight controls featured a dynamic artificial feel system, the pressure for which was provided via a ram-air inlet. A Smith Aerospace autopilot and instrument landing system (ILS) functionality was installed along with various navigational aids, such as the Marconi Company-built Green Satin doppler radar, Gee radio navigation, Automatic Direction Finder (ADF), VOR/Distance Measuring Equipment (DME), and radar altimeters. Provisions for additional equipment and sensors, such as side looking airborne radar, were also made.
The main centre fuselage of the Valiant was highly strengthened around a massive backbone beam to appropriately support the weight and stresses of the two widely-set wing spars and five protected fuel cells located in the upper portions of this section, the sizable bomb bay was also in the lower half of the centre fuselage. The aft fuselage used a semi-monocoque structure, being far lighter than the centre fuselage; the Boulton-Paul-produced electro-hydraulic power units for the ailerons, elevators, and rudder were contained within this space. The tail, which was attached to the rear fuselage was of a simple design, being tapered rather than swept back, the horizontal tailplane was mounted well up the vertical fin to keep it clear of the engines' exhaust. The tailcone contained a tail warning radar.
The main structural components, spars and beams of the Valiant had been constructed from a zinc/magnesium/copper aluminium alloy designated as DTD683 in the UK, which later proved problematic. The Valiant had been designed with a 'Safe-Life' strategy; this combination of 'Safe-Life' and DTD683 came to be viewed as a severe mistake. In 1956, a publication within the Journal of the Institute of Metals condemned the material DTD683 as being unstable and capable of catastrophic failure when stressing the airframe close to its design limits. The "Safe-Life" design strategy was dismissed by a Lockheed engineer in a talk given to the Royal Aeronautical Society in 1956, because it did not guarantee safety in a catastrophic failure.
The Valiant B.1 could carry a single 10,000 pounds (4,500 kg) nuclear weapon or up to 21 1,000 pounds (450 kg) conventional bombs in its bomb bay. The Valiant had been designed not only to accommodate the early fission-based nuclear weapons, but also the newer and larger thermonuclear hydrogen bombs. A "clean" Valiant (one without underwing tanks) could climb straight to 50,000 ft after takeoff unless it had heavy stores in the large bomb bay. In the aerial reconnaissance role, a camera crate would be installed in the bomb bay, along with a pair of cameras set into the fuselage and larger rear fuel tanks to extend the aircraft's endurance. Large external fuel tanks under each wing with a capacity of 1,650 imperial gallons (7,500 l), could be used to extend range; an auxiliary fuel tank could also be installed in the forward area of the bomb bay; the external wing tanks were fitted as standard on Valiants that were operated as aerial refuelling tankers. For receiving fuel, a fixed refuelling probe was fitted onto the aircraft's nose, this was connected to the fuel tanks via a pipe running along the outside of the canopy to avoid penetrating the pressure cabin.
Operational history
Nuclear deterrent
The first squadron to be equipped with the Valiant was 138 Squadron, which formed at RAF Gaydon on 1 January 1955, with 232 Operational Conversion Unit forming at Gaydon on 21 February 1955 to convert crews to the new bomber. Since the Valiant was part of an entirely new class of bombers for the RAF, the crews for the new type were selected from experienced aircrew, with first pilots requiring 1,750 flying hours as an aircraft captain, with at least one tour flying the Canberra, with second pilots needing 700 hours in command and the remaining three crewmembers had to be recommended for posting to the Valiant by their commanding officers. Valiants were originally assigned to the strategic nuclear bombing role, as were the Vulcan and Victor B.1s when they became operational. At its peak, the Valiant equipped ten RAF squadrons.
According to Gunston and Gilchrist, the Valiant had performed "extremely well" during bombing competition hosted by American Strategic Air Command (SAC). American interest in the Valiant resulted in a visit to Vickers by USAF generals Vandenberg, Johnson and LeMay. Vickers test-pilot Brian Trubshaw believed that George Edwards was put under some pressure to build the Boeing B-47 under license. The only result from the visit was Le May's insistence that the Valiant pilot side-by-side seating be incorporated in the B-52 instead of the tandem arrangement in the B-47 and prototype B-52.
On 11 October 1956, a Valiant B.1 (WZ366) of No 49 Squadron was the first RAF aircraft to drop a British operational atomic bomb when it performed a test drop of a down-rated Blue Danube weapon on Maralinga, South Australia. Windscreen blinds were fitted in advance of the test to protect the crew from the intense flash of light from the nuclear detonation. Following the landing of the aircraft after deploying the weapon, WZ366 was assessed for potential damage and for radioactive contamination.
On 15 May 1957, a Valiant B(K).1 (XD818) dropped the first British hydrogen bomb, the Short Granite, over the Pacific as part of Operation Grapple. No 49 Squadron was selected to perform the live weapon drop, and were equipped with specially-modified Valiants to conform with the scientific requirements of the tests and other precautionary measures to protect against heat and radiation. The test was largely a failure, as the measured yield was less than a third of the maximum expected and while achieving the desired thermonuclear explosion the device had failed to operate as intended. The first British hydrogen bomb that detonated as planned was dropped in the Grapple X test on 8 November 1957. The Grapple series of tests continued into 1958, and in April 1958 the Grapple Y bomb exploded with ten times the yield of the original "Short Granite". Testing was finally terminated in November 1958, when the British government decided it would perform no more air-delivered nuclear tests.
Originally the bombing role was to have been carried out at high altitude, but following the shooting down in 1960 of the Lockheed U-2 flown by Gary Powers by an early Soviet SA-2 Guideline missile, the SAM threat caused the V-force to train for low-level attack as a means of avoiding radar detection when flying within hostile airspace. They were repainted in grey/green camouflage with normal markings, replacing their anti-flash white scheme. By 1963, four Valiant squadrons (49, 148, 207 and 214) had been assigned to SACEUR in the low-level tactical bombing role. By this point, there had been a noticeable decline in flying rates for the type.
Conventional warfare
Peacetime practice involved the dropping of small practice bombs on instrumented bombing ranges, and a system of predicted bombing using radio tones to mark the position of the bomb drop over non-range targets, the bomb error being calculated by a ground radar unit and passed either to the crew during flight or to a headquarters for analysis. Use of the Valiant's Navigational and Bombing System (NBS) and the high quality of assigned crews, who were typically veterans and often had been previously decorated for wartime service, meant a high level of bombing accuracy could be achieved, greater than that of aircraft during the Second World War. According to Gunston and Gilchrist, Valiant crews were able to place practice bombs from an altitude of 45,000 feet (14,000 m) within a few meters of their assigned target.
The Valiant was the first of the V-bombers to see combat, during the Anglo-French-Israeli Suez intervention in October and November 1956. During Operation Musketeer, the British military operation in what became known as the Suez Crisis, Valiants operating from the airfield at Luqa on Malta repeatedly dropped conventional bombs on targets inside Egypt. Egyptian military airfields were the principal target of these bombing raids; other targets included communications such as radio stations and transport hubs. On the first night of the operation, six Valiants were dispatched to bomb Cairo West Air Base (which was aborted in flight due to potential risk to US personnel in the vicinity) while six more attacked Almaza Air Base and a further five bombed Kibrit Air Base and Huckstep Barracks.
Although the Egyptians did not oppose the attacks and there were no Valiant combat losses incurred, the results of the raids were reportedly disappointing. Although the Valiants dropped a total of 842 long tons (856 t) of bombs, only three of the seven airfields attacked were seriously damaged. The Egyptian Air Force had been effectively destroyed in a wider series of multinational attacks of which the Valiant bombing missions had been a part. It was the last time the V-bombers flew a live combat mission until Avro Vulcans bombed Port Stanley airfield in the Falkland Islands during the Falklands War in 1982.
Tanker operations
Valiant tankers were flown by No. 214 Squadron at RAF Marham, operational in 1958, and No. 90 Squadron at Honington, operational in 1959. The two lost their bomber role and became full-time tanker squadrons on 1 April 1962. Aircraft assigned to the tanker role were fitted with a Hose Drum Unit (HDU or "HooDoo") in the bomb bay. The HDU was mounted on bomb-mounting points and could be removed if necessary; this arrangement meant that the bomb bay doors had to be opened in order to give fuel to a receiver aircraft. A control panel at the radar navigator station in the cockpit was used to operate the HDU. All of the HDU equipment was designed to be easily removable so that the aircraft could be reverted to the bomber role.
With in-flight refuelling probes fitted to Valiants, Vulcans and Victors and Valiant tankers available to give fuel and extend the range of the aircraft being refuelled, the RAF Medium Bomber Force could go beyond "medium range", and the RAF had a long range capability. Long-range demonstration flights were made using Valiant tankers pre-deployed along the route. In 1960, a Valiant bomber flew non-stop from Marham in the UK to Singapore and in 1961 a Vulcan flew non-stop from the UK to Australia. The two tanker squadrons regularly practised long range missions, refuelled by other Valiant tankers on the way. These included non-stop flights from the UK to Nairobi, Singapore and Sydney. In 1963 a squadron of Gloster Javelin fighters was refuelled by tankers and flew in stages from the UK to India (Exercise "Shiksha") to support the Indian Air Force in a dispute over their border with China. Other aircraft refuelled by Valiants at this time included Victor and Vulcan bombers, English Electric Lightning fighters, and de Havilland Sea Vixen and Supermarine Scimitar fighters of the Royal Navy.
Countermeasures and reconnaissance roles
Valiants of No. 18 Squadron RAF at RAF Finningley were modified to the "radio countermeasures" (RCM) role—now called "electronic countermeasures" (ECM). These aircraft were ultimately fitted with American APT-16A and ALT-7 jamming transmitters, Airborne Cigar and Carpet jammers, APR-4 and APR-9 "sniffing" receivers, and chaff dispensers. At least seven Valiants were configured to the RCM role.
Valiants of No. 543 Squadron at RAF Wyton were modified to serve in the photographic reconnaissance role. In one notable operation in 1965, Valiants of No. 543 Squadron photographed around 400,000 square miles (1,000,000 km2) of Rhodesia across an 11-week period.
Fatigue failures and retirement
In 1956, Vickers had performed a series of low level tests in WZ383 to assess the type for low level flight at high speed. Several modifications to the aircraft were made, including a metal radome, debris guards on the two inboard engines, and after six flights the aileron and elevator artificial feel was reduced by 50%. Pilots reported problems with cabin heating and condensation that would need remedying. The aircraft was fitted with data recording equipment and these data were used by Vickers to estimate the remaining safe life of the type under these flying conditions. Initially a safe life of 75 hours was recommended, which became "the real figure might be less than 200 hours". The number of hours flown by each Valiant in a year was an operational issue for the RAF.
Later the RAE ran a similar series of tests that more closely resembled actual operational conditions including low level and taxiing; the corresponding report published in 1958 produced data that could be used to get a better grasp on which flight conditions produced the most damage, and enable a better projection of the future life span for the type.
In May 1957 Flight reported an "incident at Boscombe Down, when a Valiant cracked a rear spar member after a rocket-assisted takeoff in overload conditions" This aircraft was the second prototype WB 215; it was subsequently broken up for wing fatigue testing after it had flown 489 hours. In July 1964, a cracked spar was found in one of the three Valiants (either WZ394 – Wynne, or WZ389 – Morgan) on Operation Pontifex. This was followed on 6 August by a failure of the starboard wing rear spar at 30,000 ft, in WP217, an OCU aircraft from Gaydon captained by Flight Lieutenant "Taffy" Foreman. The aircraft landed back at Gaydon but without flap deployment because damage to the starboard rear spar caused the flap rollers to come out of their guides so that the flap would not lower on that side. Later inspection of the aircraft also showed the fuselage skin below the starboard inner plane had buckled, popping the rivets; the engine door had cracked and the rivets had been pulled and the skin buckled on the top surface of the mainplane between the two engines. Both of these aircraft were PR variants.
Inspections of the entire fleet showed that the wing spars were suffering from fatigue at between 35% and 75% of the assessed safe fatigue life, probably due to low level turbulence. After this inspection, the aircraft were divided into three categories, Cat A aircraft continuing to fly, Cat B to fly to a repair base, and Cat C requiring repair before flying again. The tanker squadrons had the highest proportion of Cat A aircraft because their role had been mainly at high level. This also caused the methods of assessing fatigue lives to be reviewed. By the time the type was scrapped, only about 50 aircraft were still in service; the rest had been slowly accumulating at various RAF Maintenance Units designated as "Non effective Aircraft".
Initially there was no question of retiring the type, or even a majority of affected aircraft. Repairs were actively taking place at Valiant bases such as Marham using working parties from Vickers plus RAF technicians from the base. In January 1965, the Wilson government with Denis Healey as Secretary of State for Defence decided that the expense of the repairs could not be justified, given the short operational life left to the Valiant, and the fleet was permanently grounded as of 26 January 1965. The QRA alert that had been in place for SACEUR was maintained until the final grounding and was then allowed to lapse. When asked to make a statement regarding the Valiant's scrapping in the House of Commons, Denis Healey stated that it "was not in any way connected with low-level flying" and that the "last Government took the decision to continue operating the Valiant force for another four years after its planned fatigue life was complete".
Aviation author Barry Jones commented in his book that: "A question has to be asked. For two years before the demise of the Valiant, Handley Page at Radlett had 100 Hastings go through their shops. They were completely dismantled and rebuilt, having DTD683 components removed and replaced by new alloy sections. What was so special about the Hastings and why was the Valiant not treated similarly? Perhaps we will know one day – but I doubt it." A Flight report about the scrapping states "Fatigue affected all Valiants ... not only those that had been used for some low flying".
On 9 December 1964, the last Valiant tanker sortie in XD812 of 214 Squadron was refuelling Lightning aircraft over the North Sea and was recalled to land back at Marham before the scheduled exercise was completed. On the same day, the last Valiant bomber sortie was carried out by XD818
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