Editing Avro Vulcan (section)

===Prototypes and type certification{{anchor|Vulcan B.1}}{{anchor|Vulcan B.1A}}{{anchor|Vulcan B.2}}===

====First prototype VX770 and name====
[[File:Comparison of Vulcan Planforms.jpg|thumb|upright|Comparison of Vulcan wing designs]]
More influential than the Avro 707 in the 698's design was the wind-tunnel testing performed at RAE [[Farnborough Airport|Farnborough]]. This necessitated a wing redesign incorporating a cranked and drooped leading edge and [[vortex generators]] to avoid the onset of [[Compressibility#Aeronautical dynamics|compressibility]] drag, which would have restricted the maximum speed.<ref>Laming 2002, p. 43.</ref> This wing modification resulted in the "phase 2" wing which was first investigated on Avro 707A WD480. This modification was too late to be incorporated on the two prototype 698s and the first three B.1 aircraft before their first flights. (The B.1s were quickly retrofitted).

Painted gloss white, the 698 prototype VX770, with its pure delta wing, flew for the first time on 30 August 1952 piloted by [[Roland Falk|Roly Falk]] flying solo.<ref>Darling 2007, p. 13</ref> VX770, fitted with only the first pilot's ejection seat and a conventional control wheel, was powered by four [[Rolls-Royce Avon|Rolls-Royce RA.3 Avon]] engines of {{convert|6500|lbf|kN|abbr=on}} thrust, its intended [[Bristol Olympus]] engines not being available. The prototype had fuselage fuel tanks but no wing tanks, so temporary additional tankage was carried in the bomb bay.<ref>Blackman 2007, pp. 38, 40.</ref> VX770 made an appearance at the 1952 [[Society of British Aerospace Companies|Society of British Aircraft Constructors']] (SBAC) Farnborough Air Show the next month when Falk demonstrated an almost vertical bank.<ref name="Empire">Hamilton-Paterson 2010, pp. 18–19.</ref>

After its Farnborough appearance, the future name of the Avro 698 was a subject of speculation. Avro had strongly recommended the name ''Ottawa'',{{refn|RAF bombers had been traditionally named after inland towns in the British Commonwealth or towns associated with industry.<ref name='white44'>Wansbrough-White 1995, p. 44.</ref>|group=N}} in honour of the company's connection with [[Avro Canada]].<ref name = 'but 31'/><ref name='white44'/> The weekly magazine ''[[Flight International|Flight]]'' suggested ''Albion'' after rejecting ''Avenger'', ''Apollo'', and ''Assegai''. The chief of the air staff preferred a V-class of bombers, and the Air Council announced the following month that the 698 would be called ''Vulcan'' after the [[Vulcan (mythology)|Roman god of fire and destruction]].<ref name='brookes8'>Brookes and Davey 2009, p. 8.</ref>

In January 1953, VX770 was grounded for the installation of wing fuel tanks, [[Armstrong Siddeley Sapphire|Armstrong Siddeley ASSa.6 Sapphire]] engines of {{convert|7500|lbf|kN|abbr=on}} thrust and other systems; it flew again in July 1953.<ref>Blackman 2007, p. 41.</ref>

From 1957, VX770 was used as the flying testbed for the [[Rolls-Royce Conway]] [[turbofan|by-pass]] engine. It crashed at [[1958 Syerston Avro Vulcan crash|a flying display]] at [[RAF Syerston]] in September 1958.<ref name="auto">Darling 2007, p. 15.</ref>

====Second prototype VX777====
The second prototype, VX777, first flew on 3 September 1953. More representative of production aircraft, it was lengthened to accommodate a longer nose undercarriage leg to increase the angle of attack of the wing, shortening the take-off run. It featured a visual bomb-aiming blister under the cabin and was fitted with Bristol Olympus 100 engines of {{convert|9750|lbf|kN|abbr=on}} thrust. At Falk's suggestion, a fighter-style control stick had replaced the control wheel. Like VX770, VX777 had the original wing with straight leading edges.<ref name="auto"/> VX777 was joined in formation by the first prototype VX770 and four Avro 707s at the 1953 Farnborough Air Show. During trials in July 1954, VX777 was substantially damaged in a heavy landing at Farnborough. It was repaired, fitted with Olympus 101 engines of {{convert|11000|lbf|kN|abbr=on}} thrust before resuming trials with Avro and the [[Aeroplane and Armament Experimental Establishment]] (A&AEE) at [[MOD Boscombe Down|Boscombe Down]].{{citation needed|date=November 2024}}

====Testing and type certification====
While exploring VX777's high-speed and high-altitude [[flight envelope]] at the A&AEE, mild [[buffeting]] and other undesirable flight characteristics were experienced while approaching the limiting Mach number, including an alarming tendency to enter an [[Mach tuck|uncontrollable dive]]. This was judged unacceptable for an unarmed bomber. Fitting the phase 2 wing removed the buffeting and an auto-mach trimmer countered the high-speed dive. The latter applied up-elevator as the speed critically increased. This up-elevator force was greater than the force required to counter the dive. Consequently, as speed increased, the control column had to be pushed rather than pulled to maintain level flight. This artificial pitch-up made the Vulcan handle more like other aircraft as its speed increased.<ref>Blackman 2007, pp. 82/83</ref>

The first production B.1{{refn|A contract for 25 production models had been made in July 1952. The same number of the rival Handley Page design, later named Victor, were also ordered.<ref name='wynn62'>Wynn 1997, p. 62.</ref>|group=N}} XA889 first flew in February 1955 with the original wing<ref>Blackman 2007, p. 48.</ref> and joined the trials in June. In September 1955, Falk, flying the second production B.1 XA890 (which had remained at Woodford as part of the MoS's Air Fleet on radio trials), amazed crowds at the Farnborough Air Show by executing a [[barrel roll]]<ref name="Blackman, 2007, 128" >Blackman 2007, pp. 128–129.</ref> on his second flypast in front of the SBAC president's tent. After two days of flying, he was called in front of service and civil aviation authorities and ordered to refrain from carrying out this "dangerous" manoeuvre.<ref name="Blackman, 2007, 128" /> Now fitted with a phase 2 wing, XA889 was delivered in March 1956 to the A&AEE for trials for the type's initial [[Certificate of Airworthiness]] which it received the following month.<ref>Laming 2002, p. 48.</ref>

(In 1956, VX777 was modified with the even larger phase 2(C) wing. Fitted with Olympus 104 engines, it became the aerodynamic prototype of the Vulcan B.2.){{citation needed|date=November 2024}}