Editing Vickers Valiant (section)

==Design==
[[File:Vickers Valiant (27363801724).jpg|thumb|Forward view of preserved Vickers Valiant XD818 at [[Royal Air Force Museum Midlands]] ]]
The Valiant was based on contemporary aeronautical knowledge with no advanced untried aerodynamics that required proving with scaled-down research aircraft or lengthy research and development. As a result George Edwards described the Valiant appropriately and simply but using his own, mostly original, idiom<ref>From Bouncing Bombs To Concorde-The Authorised Biography Of Aviation Pioneer Sir George Edwards OM,Robert Gardner 2006, {{ISBN|0 7509 4389 0}}, p.85</ref> as an "unfunny" aircraft.
The Valiant had a shoulder-mounted wing and four Rolls-Royce Avon RA.3 turbojet engines, each providing up to {{convert|6500|lbf|kN}} of thrust, installed in pairs in [[fireproof]] bays in each wing root.<ref name = "bomber 75"/> The design of the Valiant gave an overall impression of a clean aircraft with swept-wing aerodynamics.<ref name="Andrews Vickers p449">Andrews and Morgan 1988, p. 449.</ref> The root chord thickness ratio of 12% allowed the Avon engines to be within the wing rather than on pods as in the contemporary [[B-47 Stratojet|Boeing B-47]].<ref name="Andrews Vickers p442">Andrews and Morgan, p. 442.</ref> 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.<ref name = "bomber 73 74">Gunston and Gilchrist 1993, pp. 73–74.</ref>

The wing of the Valiant used a "compound sweep" configuration, devised by Vickers [[aerodynamics|aerodynamicist]] Elfyn Richards.<ref name="Barfield p158">Barfield ''Air International'' September 1992, p. 158.</ref> Richards found that it was necessary to increase the sweep on the inboard section of the wing, a discovery which he later [[patent]]ed as "Improvements in Aeroplane Wing Formation" with an explanation that "the formation of the shockwaves be delayed to the same extent over the whole span of the wing";<ref>Patent Specification 631,785, Improvements in Aeroplane Wing Formation", Elfyn John Richards, Application Date Nov. 25,1947</ref> the Valiant wing had 37° sweepback for the inner third of the wing, and 21° for the remainder.<ref name="Aero Aug80 p398">Burnet and Morgan  ''Aeroplane Monthly'' August 1980, p. 398.</ref><ref name = "bomber 74">Gunston and Gilchrist 1993, p. 74.</ref> This was because the thickness/chord ratio could be reduced closer to the tips.<ref name="Barfield p158"/> 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 {{convert|55000|ft}} when lightly loaded.<ref name="Profile p16">Andrews 1966, p. 16.</ref><ref name = "black wright 17 18">Blackman and Wright 2015, pp. 17–18.</ref> A [[drogue parachute]] was not necessary even operating from runways as short as {{Convert|6000|ft}}.<ref name = "bomber 77"/>

The wing was mounted high on the fuselage and the location of the engines and main [[landing gear]] within the wing limited the volume available for fuel.<ref name = "bomber 75"/> The [[trailing edge]] of the wing had two-section [[aileron]]s with [[trim tab]]s, and inboard of the ailerons were double-slotted [[Flap (aeronautics)|flap]]s.<ref>Gunston and Gilchrist 1993, pp. 75–76.</ref> Direct [[electric motor|electrical drive]]s were used to move the flaps and landing gear. The only hydraulically-operated equipment, the steering and brakes, was also powered by electric motors but driving hydraulic pumps instead of mechanical gearing.<ref name = "bomber 76">Gunston and Gilchrist 1993, p. 76.</ref>

[[File:Valiant 2 (3446560911).jpg|thumb|left|The wing root and air intakes]]
Production aircraft were powered by four Avon 201 turbojet engines, with {{convert|9500|lbf|kN}} thrust. The engines also provided [[bleed air]] for the [[pressurization]], [[ice protection system|ice protection]], and [[air conditioning]] systems. The aircraft's DC electrical [[Electric generator|generator]]s were also driven by the engines.<ref name = "bomber 76"/> [[Napier & Son|Napier Spraymat]] [[electric heating|electric heaters]] were installed in the engine inlets to prevent ice formation and subsequent shedding possibly causing engine damage. The shape of the engine inlets were long rectangular slots in the first prototype, whereas production Valiants had oval or "spectacle" shaped inlets designed to pass greater airflow for the more powerful engines that were installed.<ref name="Andrews Vickers p442"/> The jet exhausts emerged from fairings above the trailing edge of the wings.<ref name="Andrews Vickers p442"/>

For required takeoff performance from short tropical dispersal bases,<ref>Gunston 1973, p. 50.</ref> a [[jettison (aviation)|jettisonable]] [[RATO|rocket booster engine]]s pack was developed for the Valiant.<ref name = "bomber 78"/> Trials were performed with two underwing [[de Havilland Sprite]] boosters; they were no longer needed when more powerful variants of the Avon engine became available. Also, there was an increased risk of accidents if one booster rocket failed on takeoff, resulting in asymmetric thrust.<ref name = "black wright 20">Blackman and Wright 2015, p. 20.</ref> Some Valiant engines had [[water injection (engines)|water injection]], which increased takeoff thrust by about {{convert|1000|lbf|kN}} per engine.<ref name = "darling 41">Darling 2012, p. 41.</ref>

The crew were in a pressurized compartment in the forward fuselage and consisted of a pilot, co-pilot, two navigators, and air signaller (later called an air electronics officer (AEO)).<ref name = "black wright 28">Blackman and Wright 2015, p. 28.</ref> Manufacture of this pressurized section was subcontracted to [[Saunders-Roe]]. The pilot and co-pilot were located side by side on an upper level, the remaining three crew members sat at stations lower in the cockpit, and faced to the rear.<ref>Gunston and Gilchrist 1993, pp. 74–75.</ref> The crew was reduced to five with the deleted requirement for defensive [[gun turret]]s and [[air gunner]]s, an operational philosophy proved by the [[De Havilland Mosquito]] bomber of World War II.<ref name = "bomber 74"/>{{#tag:ref|Vickers had proposed the installation of a pair of 20 mm [[revolver cannon|cannon]] in the tailcone; this concept was never taken beyond the drawing stage.<ref name = "bomber 78"/>|group=N}} The pilot and copilot were provided with [[Martin-Baker Mk.3]] [[ejector seat]]s, while the rear crew had to bail out of the oval main entrance door on the port side of the fuselage.<ref name="Turpin p79-0">Turpin 2002, pp. 79–80.</ref> Safe escape using this exit was not considered likely.<ref name = "bomber 75"/>

[[File:Vickers Valiant B1 (3873562557).jpg|thumb|The entry door on the side of the forward fuselage, with the names of pilot [[Kenneth Hubbard]] and his crew]]
The fuselage area behind the pressurised crew section and forward of the wing was used to house much of the [[avionics]], and air conditioning equipment, and was sometimes called the "organ loft".<ref name = "bomber 75">Gunston and Gilchrist 1993, p. 75.</ref> The Valiant had twin-wheel nosegear and [[tandem]]-wheel main gear that retracted outwards into recesses in the underside of the wing. Each of the main gears were equipped with multipad [[anti-lock braking system|anti-skid]] [[disc brake]]s, and were [[telescoping (mechanics)|telescopic]]ally linked so that a single drive motor could pull them up into the wing recesses.<ref name = "bomber 75"/> Most of the aircraft systems were electric, including the flaps and undercarriage.<ref name = "darling 39">Darling 2012, p. 39.</ref> The brakes and steering gear were electrically powered, driving hydraulic pumps for actuation.<ref name="Flight p19"/><ref name = "black wright 18"/> The lower half of the aircraft nose contained the scanner for the [[H2S (radar)|H2S]] [[radar]] in a [[glass fiber]] [[radome]]; in addition, a visual [[bomb sight]] was located beneath the lower floor of the pressurised cockpit.<ref name = "bomber 75"/> The avionics bay was not accessible from the cockpit but could be accessed using an entrance at the base of the rear fuselage leading to an internal [[catwalk]] above the aft part of the [[bomb bay]].<ref name = "bomber 76 77">Gunston and Gilchrist 1993, pp. 76–77.</ref>

The electrical systems used 112 volt [[direct current]] generators, one on each engine, for functions requiring large amounts of electrical power. A 28 V DC system was used for other uses including actuators that controlled the higher-voltage system functions. Backup power came from 24 V and 96 V batteries. 115 V [[alternating current]] was provided for the radar and the [[actuator]]s for the flight surfaces, flaps, [[Air brake (aeronautics)|air brake]]s and undercarriage.<ref name="Flight p19">''Flight'' 4 July 1958, p. 19.</ref><ref name="Turpin p78">Turpin 2002, p. 78.</ref><ref name = "black wright 18"/> It was decided during the design phase that as much of the aircraft would be electrically driven as was possible; the complete electrical system including high voltage generators and cabling, together with electric motors with mechanical drives, was lighter than the hydraulic equivalent consisting of pumps, tubing, actuators, fluid and storage tanks.<ref name = "bomber 76"/>

The [[aircraft flight control system|flight control]]s of the Valiant (ailerons, elevator and rudder) consisted of two channels of power control with full manual backup; flying in manual was practised during training as it would be required if a complete electrical failure occurred during a flight.<ref name="Flight p19"/> In "manual" the flight controls required considerable physical effort to operate.<ref name = "black wright 18">Blackman and Wright 2015, p. 18.</ref> The pilot's controls for elevators, ailerons and rudder had an [[Aircraft flight control system#Artificial feel devices|artificial feel]] system, the pressure for which was provided from a [[ram-air intake|ram-air inlet]].<ref name = "bomber 76"/>

A [[GE Aviation Systems|Smith Aerospace]] [[autopilot]] and [[instrument landing system]] (ILS) was installed along with various [[navigational aid]]s, such as the [[Marconi Company]]-built [[Green Satin radar|Green Satin]] [[doppler radar]], [[Gee (navigation)|Gee]] [[radio navigation]], [[Non-directional beacon|Automatic Direction Finder]] (ADF), [[VHF omnidirectional range|VOR]]/[[distance measuring equipment|Distance Measuring Equipment]] (DME), and [[radar altimeter]]s.<ref name = "bomber 77"/> Provisions for additional equipment and sensors, such as [[side looking airborne radar]], were also made.<ref name = "bomber 77"/>

[[File:Handley Page K2 (10024223034).jpg|thumb|Landing gear and wing]]
The centre fuselage of the Valiant had a main backbone beam to support the weight of the two widely-set [[Spar (aeronautics)|wing spar]]s and five [[fuel cell]]s in the upper fuselage. The bomb bay was also in the lower half of the centre fuselage.<ref name = "bomber 75"/><ref name="Flight p18">''Flight'' 4 July 1958, p. 18.</ref> The aft fuselage used a [[monocoque|semi-monocoque]] structure, being lighter than the centre fuselage; the [[Boulton Paul Aircraft|Boulton-Paul]]-produced electro-hydraulic power units for the ailerons, [[elevator (aeronautics)|elevator]]s, and [[rudder]] were contained within this space.<ref name = "bomber 76"/> The tail, which was attached to the rear fuselage was [[Cone|tapered]] rather than swept back,<ref name = "bomber 75"/> the [[horizontal stabilizer|horizontal tailplane]] was mounted well up the [[vertical stabilizer|vertical fin]] to keep it clear of the engines' exhaust.<ref name="Barfield p158"/> The tailcone contained an ARI 5800 Orange Putter [[tail warning radar]].<ref name = "bomber 78"/>

The main structural components, spars and beams of the Valiant had been constructed from a zinc/magnesium/copper aluminium alloy called DTD683 in the UK.<ref>''Flight'' 14 December 1951, p. 756.</ref><ref>''Flight'' 17 July 1953, p. 91.</ref> The Valiant had been designed with a '[[Safe-life design|Safe-Life]]' strategy;<ref>Brookes 2012, p. 83.</ref> 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<ref>''The Journal of the Institute of Metals'' (JIM), Vol. 86, No. 1790, 1957–1958.</ref>{{#tag:ref|Structural Changes Caused by Plastic Strain and by fatigue in Aluminium-Zinc-Magnesium-Copper Alloys Corresponding to DTD.683 (Broom and Mezza)|group=N}} 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 from catastrophic failure.<ref>''Flight'' 6 April 1956, p. 394.</ref>

The Valiant B.1 could carry a {{convert|10000|lb|kg|adj=on}} nuclear weapon or up to 21 {{cvt|1000|lb|kg}} conventional [[bomb]]s in its bomb bay. It was designed for the early [[Nuclear fission|fission]]-based nuclear weapons and also the newer and larger [[thermonuclear]] [[hydrogen bomb]]s.<ref name = "bomber 75"/> A "clean" Valiant (one without underwing tanks) could climb straight to 50,000&nbsp;ft after takeoff unless it had heavy stores in the large bomb bay.{{Citation needed|date=May 2011}}

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.<ref name = "black wright 19">Blackman and Wright 2015, p. 19.</ref> Large external fuel tanks under each wing with a capacity of {{convert|1650|Impgal|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.<ref name = "black wright 19"/> For receiving fuel, a fixed [[aerial refueling#Probe-and-drogue 2|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.<ref name = "bomber 79">Gunston and Gilchrist 1993, p. 79.</ref>