North American F-100 Super Sabre
The North American F-100 Super Sabre was an American supersonic jet fighter aircraft designed and produced by the aircraft manufacturer North American Aviation. The first of the Century Series of American jet fighters, it was the first United States Air Force fighter capable of supersonic speed in level flight.
The F-100 was envisioned during the late 1940s as a higher-performance successor to the F-86 Sabre air superiority fighter. Initially referred to as the Sabre 45, it was delivered as an unsolicited proposal to the USAF in January 1951, leading to two prototypes being ordered one year later following modifications. The first YF-100A performed its maiden flight on 25 May 1953, seven months ahead of schedule. Flight testing demonstrated both the F-100's promising performance and several deficiencies, which included its tendency of yaw instability and inertia coupling that led to numerous fatal accidents. On 27 September 1954, the F-100A officially entered USAF service, however, as a result of six major accidents occurred by 10 November 1954, the type was grounded while investigations and remedial work were conducted. The F-100 returned to flight in February 1955.
In response to the Tactical Air Command's request for a fighter-bomber, the F-100C was developed, followed by the more capable F-100D. Several other models would be developed, including the two-seat F-100F supersonic trainer. As early as 1958, the USAF began to withdraw its F-100As, but returned them to service during early 1962 amid escalating world tensions. Many F-100s saw combat use during the Vietnam War before being superseded by the high-speed Republic F-105 Thunderchief in the strike mission role. The F-100 flew extensively over South Vietnam as the air force's primary close air support aircraft until being replaced by the more capable subsonic LTV A-7 Corsair II, General Dynamics F-111 Aardvark, and the McDonnell Douglas F-4 Phantom II. 242 F-100s of various models were lost over Vietnam. Several F-100As were rebuilt into RF-100A aerial reconnaissance aircraft. Several F-100Fs were modified into electronic warfare platforms. Several proposed models and derivatives, such as the F-100B interceptor and the F-107, did not proceed through to production.
Amid a relatively high attrition rate and the arrival of more advanced fighters, the USAF opted to permanently withdraw its remaining F-100s during the early 1970s. The type was also operated by the Air National Guard until 1979. The F100 was exported to several overseas operators, including NATO air forces and other US allies, including the Turkish Air Force, Republic of China Air Force, and the French Air Force. The F-100 was deployed during the Turkish invasion of Cyprus, performing close air support missions. French F-100s also saw action during the Algerian War. During its later life, the F-100 was often referred to as the "Hun", a shortened version of "one hundred".
Development
Background
The F-100 can be traced back to an internal design study performed by North American Aviation as early as 1949. It was named Sabre 45 in reference to its 45° wing sweep and essentially represented an evolution of the company's successful F-86 Sabre. In January 1951, the company delivered an unsolicited proposal for a supersonic day fighter to the United States Air Force. On 7 July 1951, a mockup of the aircraft was presented for inspection; the USAF produced a general operational requirement that called for an air superiority weapon to be operational no later than 1957, preferably by 1955. During October 1951, the Air Force Council advocated for the development of a refined model of the Sabre 45; furthermore, it agreed with the Aircraft and Weapons Board's recommendation that it be purchased in quantity even prior to flight testing despite the risks involved in this approach.By mid-November 1951, in excess of 100 aircraft configuration change requests had been received, necessitating numerous modifications to the original design; several of these alterations were focused on its armaments and were intended to improve its lethality. The new aircraft was accepted as the F-100 on 30 November 1951. On 3 January 1952, the USAF placed an order for two prototypes; one month later, a follow-on production order was issued for 23 F-100As while an additional 250 F-100As were ordered in August of that year as well. Around this time, development work slowed considerably while North American focused on improving and ramping up production of the F-86 in response to urgent demands for more aircraft to participate in the Korean War.
Into flight
On 25 May 1953, North American Aviation Chief Test Pilot George Welch conducted the first flight of the YF-100A, seven months ahead of schedule. Once level at 35,000 feet he accelerated to supersonic speed, leaving his chase pilot, ”Pete” Everest well behind in his F-86D. As such, he was the first person to exceed Mach 1 in level flight in a jet. During one of its early test flights, the first prototype reached a maximum of Mach 1.05 in spite of being fitted with a derated Pratt & Whitney XJ57-P-7 engine. By September, flight testing had confirmed the presence of three major deficiencies in the design, all of which required correction ahead of it being considered as acceptable. On 14 October 1953, the second prototype flew for the first time, followed by the first production F-100A on 29 October 1953. This first F-100A was put through extensive testing to help develop fixes for identified deficiencies. Progress on the project was set back by a three-month general strike by North American employees in late 1953.An operational evaluation of the F-100A was conducted by the USAF November 1953 and December 1955, it determined that the new aircraft possessed superior performance to existing USAF fighters, but declared that it was not ready for widescale deployment due to various deficiencies and functional difficulties in the design. These findings were subsequently confirmed during operational suitability tests performed under "Project Hot Rod". During August 1954, six F-100s arrived at the Air Proving Ground Command, Eglin Air Force Base. The Air Force Operational Test Center used four of the fighters for operational suitability tests while the other two aircraft underwent armament tests by the Air Force Armament Center. The Tactical Air Division of the AFOTC conducted the APGC testing under the direction of project office Lieutenant Colonel Henry W. Brown; initial testing was completed by APGC personnel at Edwards Air Force Base.
Despite these shortcomings, the Tactical Air Command advocated for the F-100 as a matter of urgency, particularly in light of delays experienced in the Republic F-84F Thunderstreak program; furthermore, TAC recommended the production of a day fighter with a secondary fighter-bomber capability that would be suitable not only for the USAF but also foreign nations covered by the Mutual Development Assistance Program. Accordingly, during December 1953, the Air Council opted to alter the program, reducing the outstanding total orders for the F-100A by 70 aircraft in favor of a new fighter-bomber variant that would be capable of delivering nuclear bombs. In February 1954, the USAF would issue the first production contract for this fighter-bomber model, the F-100C; equipped to carry additional munitions and fuel tanks, the prototype performed its maiden flight one month later while the first production aircraft followed in January 1955.
In response to observed improvements in fighters deployed by the Soviet Union, the USAF directed production of the F-100 to be accelerated via the establishment of a second production line in Columbus in September 1954. During November 1954, production of the F-100 was reduced to 24 aircraft per month in response to a spate of fatal accidents. Aircraft already built were stored and the corrections were applied later. Following appropriate remedial work, the USAF opted to partially lift its restrictions on both production and flights of the F-100 in February 1955; deliveries resumed two months later.
Further development
Various adaptions and derivatives of the F-100 were considered during its development. During mid-1954, an interceptor model of the aircraft was being studied; in July of that year, a mockup of the envisioned F-110B1 was completed, it was intended as a backup for the in-development Convair F-102 Delta Dagger interceptor. However, the difficulties experienced with the F-100A were viewed as evidence that the aircraft, even in the face of expected improvements, would be incapable of satisfying the operational requirement to a greater degree than that of the F-102.The definitive model would be the F-100D. During May 1954, the TAC had requested a more sophisticated fighter-bomber; the company aimed to address the offensive shortcomings of the F-100C by being primarily a ground-attack aircraft with secondary fighter capabilities. To achieve this, the aircraft was fitted with autopilot, upgraded avionics, and starting with the 184th production aircraft, compatibility with the AIM-9 Sidewinder air-to-air missile. To further address the dangerous flight characteristics, the wingspan was extended by 26 in and the vertical tail area was increased by 27%. In October 1954, an initial production contract was issued for the F-100D, follow-on contracts would be issued in March and December of the following year. On 24 January 1956, the first F-100D flew, piloted by Daniel Darnell.
In December 1954, a new General Operational Requirement, GOR 68, was issued by the USAF; it called for a tactical fighter-bomber that would also be effective as an aerial superiority fighter under both day and night conditions. North American opted to respond with a heavily modified version of the F-100; the design was so substantially different that it was promptly decided to redesignate it as the F-107. Intended for speeds as high as Mach 2, the aircraft could be easily distinguished from the F-100 by the placement of the air intake above and behind the cockpit. It was not ultimately produced in quantity, having been passed over in favor of the competing Republic F-105 Thunderchief.
On 8 September 1955, North American proposed modifying an F-100C into a two-seat trainer model at no expense to the USAF; two months later, the air council decided to produce the type, perceiving a need for a supersonic trainer. During December 1955, an initial production contract for the F-100F trainer was placed. The prototype TF-100C, which lacked most operational equipment, made its first flight on 6 August 1956; it was followed by the first production aircraft on 7 March 1957.