Editing Convair F-106 Delta Dart (section)

==Development==
===Background===
The F-106 was the ultimate development of the USAF's [[1954 interceptor]] program of the early 1950s.<ref name="knaack p159">Knaack 1978, p. 159.</ref> The initial winner of this competition had been the [[Convair F-102 Delta Dagger|F-102 Delta Dagger]], but early versions of this aircraft had demonstrated extremely poor performance, being limited to flying at subsonic speeds and relatively low altitudes.<ref name="knaack p166167">Knaack 1978, pp. 166-167.</ref> During the testing program the F-102 underwent numerous changes to improve its performance, notably the application of the [[area rule]] to the fuselage shaping and a change of engine, and the dropping of the advanced MX-1179 [[fire control system]] and its replacement with a slightly upgraded version of the MX-1 already in use on subsonic designs. The resulting aircraft became the F-102A, and in spite of being considered barely suitable for its mission, the Air Force sent out a production contract in March 1954, under which the first deliveries were expected during the following year.<ref name="knaack p164">Knaack 1978, p. 164.</ref><ref>Converse 2012, p. 241.</ref>

By December 1951, the Air Force had already turned its attention to a further improved version, which was initially referred to as the F-102B. The main planned change was the replacement of the F-102A's [[Pratt & Whitney J57]] (which had itself replaced the original J40<ref name="knaack p163">Knaack 1978, p. 163.</ref>) with the more powerful [[Wright J67]] (a [[Bristol Olympus]] [[licensed production|produced under license]]).<ref name="knaack p207">Knaack 1978, p. 207.</ref> By the time this engine would be available, the MX-1179 was expected to be available, and thus it was selected as well. The intended result would be the "ultimate interceptor" that the USAF had originally sought.<ref name="knaack p207208">Knaack 1978, pp. 207-208.</ref> However, while initial work on the Olympus design appeared to go well, by August 1953 Wright was already a full year behind schedule in development. Continued development did not resolve problems with the engine, and in early 1955 the Air Force approved the switch to the [[Pratt & Whitney J75]].<ref>{{cite web |title = History of the 'F-106 Delta Dart' |url = http://www.f-106deltadart.com/history.htm |website = F-106DeltaDart.com |publisher = Convair Aircraft Plant San Diego, CA |access-date = 17 June 2014 |url-status = live |archive-url = https://web.archive.org/web/20140722114037/http://www.f-106deltadart.com/history.htm |archive-date = 22 July 2014}}</ref><ref name="knaack p208"/>

The J75 was somewhat larger than the J57 in the F-102A, and had greater {{clarification needed span|text=mass flow.|reason=What is "mass flow"?  Appropriate link or reliable citation, please.|date=May 2024}} This demanded changes to the inlets to allow more airflow, and led to the further refinement of using a somewhat shorter [[intake ramp|variable-geometry inlet duct]] to allow the intakes to be tuned to best performance across a wide range of supersonic speeds. The fuselage grew slightly longer, and was cleaned up and simplified in many ways. The wing was slightly enlarged in area, and a redesigned vertical tail surface was used. The engine's two-position afterburner exhaust nozzle was also used for idle thrust control, held open to decrease thrust by 40%, resulting in slower taxiing and less brake wear.<ref>Flight Manual F-106A and F-106B T.O. 1F106A-1 page 1-22 "Idle thrust control switch".</ref>

===Competing efforts and production arrangements===
Throughout its early development, the F-102B had to compete for attention and resources with the F-102A; the aviation author Marcelle Knaack observed that there were fewer funds to develop the more capable systems of the F-102B, which would have been useful in more quickly overcoming some of the technical difficulties that arose.<ref name="knaack p208">Knaack 1978, p. 208.</ref> The number of F-102As on order grew substantially beyond that which had been originally forecast, indicative of the growing importance attached to what had once been intended to be an interim or 'stop-gap' aircraft to fill in until the F-102B could be delivered. During December 1955, a mock-up with the expected layout of the MX-1179, now known as the MA-1, was inspected and approved.<ref name="knaack p208209">Knaack 1978, pp. 208-209.</ref>

On 18 April 1956, an extended production contract for 17 F-102Bs was issued to Convair, representing substantially fewer aircraft than had been originally anticipated at this stage.<ref name="knaack p208209"/> On 17 June of that year, the aircraft was officially re-designated as the F-106A.<ref name="knaack p162">Knaack 1978, p. 162.</ref><ref>{{cite web |title=The Convair F-102A |url=http://www.456fis.org/F-102A.htm |website=456FIS.ORG |publisher=THE 456th FIGHTER INTERCEPTOR SQUADRON |access-date=17 June 2014 |url-status=usurped |archive-url=https://web.archive.org/web/20140714155915/http://www.456fis.org/F-102A.htm |archive-date=14 July 2014}}</ref><ref>{{cite web |title = CONVAIR F-106A DELTA DART |url = http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=4085 |website = The Official Web Site of National Museum of the USAF |publisher = National Museum of the US Air Force |access-date = 17 June 2014  |archive-url = https://web.archive.org/web/20110914000635/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=4085 |archive-date = 14 September 2011 }}</ref> On 18 August 1956, the USAF issued a systems development directive that called for development and production of the F-106 {{clarification needed span|text=to occur simultaneously;|reason=With what?|date=May 2024}} Knaack attributed this policy as being responsible for several later problems in the program.<ref name="knaack p209">Knaack 1978, p. 209.</ref> During April 1957, the USAF formally rejected Convair's F-102C proposal (essentially a reengined model of the F-102) to concentrate on the more advanced F-106 program, which it had then anticipated to enter service during the following year.<ref name="knaack p168169">Knaack 1978, pp. 168-169.</ref>

===Flight testing===
On 26 December 1956, the first prototype F-106, an aerodynamic test bed, performed its [[maiden flight]] from [[Edwards Air Force Base]]. On 26 February 1957, the second prototype, which was outfitted with a fuller set of equipment, made its first flight.<ref name="Peacock p200">Peacock 1986, p. 200.</ref><ref name="knaack p209"/> Early flight testing around the end of 1956 and beginning of 1957 demonstrated somewhat disappointing results, having achieved less of a performance gain over the F-102 than had been anticipated. Specifically, both the acceleration and maximum speed were beneath Convair's own estimates.<ref name="knaack p210">Knaack 1978, p. 210.</ref> Furthermore, both the engine and avionics proved to be somewhat unreliable.<ref name="knaack p211">Knaack 1978, p. 211.</ref> These combined problems, and the delays associated with them, were nearly responsible for the termination of the program.<ref name="Peacock p200"/><ref>Wegg 1990, p. 209.</ref>

However, the service decided to persist with the F-106 program after the Air Defense Command had heavily advocated for it.<ref name="knaack p211212">Knaack 1978, pp. 211-212.</ref> Based upon the test data submitted, USAF officials had determined that modifications to the inlet duct cowling and charging ejectors were likely to increase both acceleration and speed; modifications would be made following the completion of Category II testing and were evaluated during Category III testing.<ref name="knaack p210"/> At this stage, the service enacted several measures to hasten development towards production; in April 1957, it authorized the conditional acceptance of several F-106s being used by Convair for flight testing; it also took several quick decisions to settle outstanding development questions.<ref name="knaack p210211">Knaack 1978, pp. 210-211.</ref> By mid-1957, funding for 120 F-106As had been allocated.<ref name="knaack p212">Knaack 1978, p. 212.</ref> The USAF ultimately opted to order 350 F-106s, substantially fewer than the planned fleet of 1,000 aircraft. Deliveries of the single-seat F-106A and the twin-seat F-106B combat-capable trainer variant commenced to 15 fighter interceptor squadrons in October 1959.<ref>Green 1964, p. 138.</ref><ref name="knaack p212"/>

===World Speed record===
[[File:ConvairF-106DeltaDart01.JPG|thumb|F-106A Delta Darts from 5 FIS at [[CFB Moose Jaw]] in 1982]]

On 15 December 1959, Major Joseph W. Rogers set a world speed record of 1,525.96&nbsp;mph (2,455.79&nbsp;km/h) in a Delta Dart at 40,500&nbsp;ft (12,300 m).<ref>Drendel 1980, p. 92.</ref><ref name="Donald 2003, p. 232">Donald 2003, p. 232.</ref><ref>"U.S. Jet Sets 1,520.9-M.P.H. Speed Record", ''Oakland Tribune'', 16 December 1959, p. 1.</ref> That year, [[Charles E. Myers]] flew the same model aircraft at 1,544&nbsp;mph (2,484&nbsp;km/h).<ref>Samuel 2015, p. 407.</ref>