<p>Designed as a nuclear bomber to attack the Soviet Union, Republic's mighty 'Thud' found fame hauling loads of iron bombs over the jungle of Southeast Asia. In the Vietnam War the type earned respect as an extremely tough warplane with a 'get-you home' capability unmatched by the more glamorous Phantom. As well as dropping bombs, it took on SAM radars and shot down MiGs.
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<p>Plagued by numerous misfortunes and shortcomings during the course of its development and early service, the 'Thud', as it became better known, emerged from the worst of these vicissitudes at about the same time as US involvement in Southeast Asia began to escalate seriously, and it was truly a case of the 'Thud' being the 'right aircraft at the right moment'. The F-105 went on to compile an impressive combat record, being involved in action for the entire sorry conflict. Inevitably, however, it paid an appallingly high price, approximately half of the 833 aircraft built falling victim to the awesome defense network in and around North Vietnam, an attrition rate which was never made good and which was directly responsible for the type's early relegation to second-line elements such as the Air National Guard and Air Force Reserve. By January 1984, only about 20 F-105D single-seaters and a handful of F-105F two-seaters remained active with one AFReS squadron of the 419th Tactical Fighter Wing at Hill AFB, Utah, these being replaced by the F-16A Fighting Falcon, an event which marked the passing of what many reckon to be Republic's greatest combat aircraft.
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<p>Known originally in company parlance as the AP-63 (Advanced Project 63), the F-105 was first conceived as a private venture in 1951 to fulfill the tactical nuclear strike role then being largely undertaken by another Republic product, namely the F-84. Overall responsibility for design rested with Alexander Kartveli, the mastermind behind several Republic success stories, most notable of which was without doubt the P-47 Thunderbolt of World War II. Like most of Kartveli's designs, the projected fighter was big. The initial proposal, based on the use of a single Allison J71 engine, was formally submitted to the US Department of Defense (DoD) in March 1952, meeting with a favorable response which culminated in the award of a contract covering tooling and engineering aspects during autumn of the same year. This was quickly followed by a DoD request that the chosen powerplant be changed to Pratt & Whitney's J57P-25 which was rated at 15,000 lb (66.73 kN), as an interim measure since it was felt that the J71 might not reach thrust requirements. In the event, this proved to be the end of the J71 as far as the F-105 was concerned, the two prototypes using the J57 while subsequent production machines were all powered by the even more powerful Pratt & Whitney J75.
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<p>Republic's enterprise was further rewarded during March 1953 with a contract covering the manufacture of no fewer than 37 examples of the XF-105A, plus nine reconnaissance-configured RF-105s to fulfill RDTE (Research, Development, Test and Evaluation) duties.
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<p>As far as the parent company was concerned, the mid-1950s proved to be a period of some frustration, difficulties being experienced both with the F-84F Thunderstreak then in quantity production and with the new fighter, although the latter did pass fairly easily the hurdle of USAF mock-up inspection during October 1953. This, however, was followed in December by a US Air Force decision to suspend procurement because of delays at Republic, and when the project was reinstated in February 1954 the number of test specimens had been cut to 15. Further complications arose in August 1954 when it was decided to install the J75 engine in four of the RDTE aircraft, these henceforth being known as F-105Bs, while development delays resulted in the program being further cut to just three aircraft in September, a figure which was doubled in October and which climbed back to 15 in February 1955, this comprising two J57-powered YF105As, 10 J75-powered YF-105Bs and three RF-105Bs for reconnaissance.
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<hi style=hdr1>'Hi Tech' Design</hi>
<p>Design of the Thunderchief occurred at a time of great innovation and the Republic Aviation Corporation was hard-pressed to keep pace with all of the many new developments then taking place. Nevertheless, the F-105 did benefit from area-ruling, while other new features centered around the unique air-inlet configuration (which is such a distinctive feature of the 'Thud') and the adoption of a ventral fin for increased lateral stability. Such was the speed of events, however, that the YF-105A prototypes were overtaken by some of these refinements and lacked a number of features which were incorporated in the production-standard aircraft.
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<p>Despite not being truly representative of the definitive configuration, the two YF-105As did make a significant contribution to the flight-test program, which began with a successful maiden flight on 22 October 1955, an occurrence highlighted by the fact that the aircraft concerned exceeded Mach 1.0 during the course of the 45-minute sortie. The second prototype entered flight status on 28 January 1956; the first F-105B followed a few months later, on 26 May 1956, although this event was marred when the aircraft involved suffered damage on landing with a resultant delay in the ensuing test program.
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<p>Although the early phases of flight test indicated considerable promise, there was still a good deal of uncertainty. This extended so far as to question the whole validity of the entire project, such doubts continuing to threaten the future of Republic's fledgling fighter even after it had proved itself superior to North American's XF-107 in a paper study conducted early in 1956. Uncertainty continued to surround the Thunderchief, but a major step forward occurred in March 1956 when some $10 million of fiscal year 1957 funding was released to cover procurement of 65 production examples of the J75-engined F-105B plus 17 RF-105s, although the proposed reconnaissance derivative was abandoned soon afterwards, in July, the three prototypes ultimately appearing as JF-105Bs specifically for test and evaluation tasks. A third variant, the two-seater F-105C combat proficiency trainer, was added to the program in June 1956 when an initial quantity of five aircraft was funded; these did not survive for long, being eliminated during the course of 1957 largely on the grounds of high cost.
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<p>Production models of the F-105B eventually began to roll from the Farmingdale line during 1958, with the USAF formally accepting its first aircraft (actually one of the test and evaluation specimens) on 27 May of that year. Re-equipment of the first Tactical Air Command unit got under way soon afterwards when, in August, the 335th Tactical Fighter Squadron began to convert. Normally stationed at Seymour Johnson AFB in North Carolina, the 335th TFS formed part of the 4th Tactical Fighter Wing and had been temporarily reassigned to Eglin AFB, Florida, from where it was extensively involved in operational test work under the auspices of Air Research and Development Command. In the event, this proved to be a frustrating and time-consuming exercise, the Thunderchief's complexity conspiring with production slippages and component supply problems to delay completion of formal USAF testing until August 1960. It was not until late in that year that the type was considered to be operationally ready. Even then, serviceability rates remained almost abysmally low, largely as a result of system unserviceability and spares shortages.
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<hi style=hdr1>F-105D Development</hi>
<p>While all this was going on, development of what eventually transpired to be the definitive Thunderchief variant, the F-105D, proceeded apace, although once again this model was subjected to more than its fair share of changes in policy. It fell foul of both politicians and planners, who between them brought about a significant shift in mission from nuclear to conventional attack duties at an early stage in the F-105's operational career and a drastic reduction in production from 1,500 aircraft for 14 fighter wings to just 753 for seven wings. The latter figure was cut still further by a later decision to complete the last 143 as two-seat F-105 trainers.
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<p>The first model of the Thunderchief family to possess genuine all-weather capability, the F-105D was, at the time of its debut, without doubt the most sophisticated and complex type to be found in TAC's inventory. In appearance it was similar to the earlier F-105B, the most significant external difference relating to the larger nose radome which contained a NASARR (North American Search And Ranging Radar) R-14A all-purpose monopulse radar which, in conjunction with the AN/ASG-19 Thunderstick FCS (fire-control system) and a Bendix toss-bombing computer, permitted the F-105D to perform visual or blind attacks with a variety of ordnance ranging from air-to-air missiles through air-to-surface missiles to conventional 'iron' bombs across virtually the entire flight envelope.
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<hi style=hdr1>In Service in Europe and Southeast Asia</hi>
<p>Unlike earlier Thunderchiefs, there was no F-105D prototype in the literal sense of the word, the first example to fly being a production-configured aircraft which made a successful maiden flight from Farmingdale on 9 June 1959. Deliveries to the US Air Force followed within a year, the first unit being the 333rd TFS of the 4th TFW, which began transition in May 1960, soon being joined by the 4th TFW's three other squadrons.
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<p>Once again, ARDC played a major part in bringing the newest variant into operational service. Another TAC unit which featured prominently at this time was the Nellis-based 4520th Combat Crew Training Wing, this being tasked with all Thunderchief training for the first half of the 1960s.
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<p>As far as overseas commands were concerned, the United States Air Force in Europe (USAFE) was first to receive F-105Ds, Bitburg's 36th TFW entering into the re-equipment phase on 12 May 1961; this wing eventually controlled three squadrons with a combined complement of about 80 aircraft. Nearby Spangdahlem became the second and last USAFE Thunderchief base during the course of 1962, when the 49th TFW converted. However, the focus of attention moved to Asian skies late in 1962 when the 18th TFW's three squadrons took delivery of their new mounts at Kadena, Okinawa.
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<p>Capable of carrying just four 750-lb (340-kg) bombs externally in its original guise, the F-105D's payload capability was greatly enhanced following the decision to switch emphasis from nuclear to conventional attack fairly soon after it entered operational service. New production aircraft from the F-105D-25-RE onwards featured multiple ejection racks (MERs) as standard, fitment of these permitting a fourfold increase in external payload, while those aircraft built before this were retrospectively modified to similar configuration during Project Look-Alike. At the same time, the original natural metal scheme gave way to an acrylic aluminum finish which offered better protection from the elements.
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<p>The Thunderchief also featured an internal weapons bay originally intended to house a single nuclear device, although this very soon gave way to a 390-US gal (1,476-liter) fuel tank which significantly increased the type's combat radius. In addition to conventional bombs, the F-105D could also operate with the Martin AGM-12 Bullpup air-to-surface missiles, 2.75-in (70-mm) rocket pods, napalm containers and the AIM-9 Sidewinder air-to-air missile, while the integral M61 Vulcan 20-mm Gatling-type cannon proved valuable in the dual roles of air-to-air combat and air-to-ground strafing in later years, Thunderchiefs downing several MiGs in Southeast Asia. Auxiliary fuel tanks could also be carried for long-distance ferry flights or strike missions, the usual combat configuration in Vietnam combining a pair of 450-US gal (1,703-liter) drop tanks on the inner-wing store stations with six 750-lb (340-kg) or five 1,000-lb (454-kg) bombs on the centerline MER. An ECM pod was also normally carried on one of the outer-wing hardpoints with a single AIM-9 Sidewinder missile on the other for self-defense.
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<p>One other variant of the F-105D also deserves mention, this being the so-called F-105D T-Stick 11 which was fitted with additional avionics in a prominent dorsal fairing extending along the spine to the leading edge of the vertical tail surfaces to bestow superior all-weather bombing capability. A total of 30 aircraft was converted to this configuration in the late 1960s and early 1970s, these entering service with the 563rd TFS, 28th TF W at McCoImell AFEA, Kansas, during the course of 1970-71. The F-105D T-Stick 11 was originally destined to undertake combat duty, although as far as is known the type was not deployed, most, if not all, being relegated to second-line service with the AFReS in 1972.
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<hi style=hdr1>Two-Seat Variant</hi>
<p>Although the original F-105C two-seater proposal fell by the wayside, the USAF was in fact anxious to acquire a model of the Thunderchief for training duties. A second attempt resulted in the F-105E, which was slightly more fortunate than its predecessor in that it did attain production status briefly before being abandoned in March 1959. The handful of aircraft then under construction eventually emerged from the factory as single-seat F-105Ds and it was not until the early 1960s that a two-seater eventually appeared, this being the F-105F model.
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<p>Authorization to proceed with the F-105F was granted in May 1962, the parent company receiving $8 million to complete the last 143 programmed F-105Ds as F-105Fs, and this model made its maiden flight on 11 June 1963, entering operational service just six months later with the 4th TFW at Seymour Johnson AFB. By the end of 1964 most of the active Thunderchief wings had received some F-105Fs, production of the Thunderchief being completed in December of that year when the last F-105F emerged from the factory.
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<p>Retaining many features of the F-105D, the two-seat model was 2,000 lb (907 kg) heavier as well as being slightly longer in order to accommodate a second cockpit in tandem. Taller vertical tail surfaces were also a feature but the internal systems were identical to those of the F-105D, while performance was only slightly impaired, a factor which proved valuable in later years when the two-seat derivative undertook SAM (surface-to-air missile) suppression tasks in Southeast Asia, initially in its original guise and later in modified form as the F-105G.
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<hi style=hdr1>SAM Masters</hi>
<p>Colloquially known as 'Wild Weasels', both the F-105F and F-105G saw extensive action in the Iron Hand anti-SAM campaign, which was among the most hazardous missions of the air war against North Vietnam. Early 'Wild Weasels' were F-105Fs fitted with RHAW (Radar Homing And Warning) apparatus, jamming pods, a missile launch warning receiver and other specialized equipment which was able to sort and identify threats posed by the SA-2 'Guideline' surface-to-air missile. Weaponry generally comprised the AGM-45 Shrike, although some F-105Fs could also carry the larger AGM-78 Standard ARM anti-radiation missile, both weapons homing on emission from SAM radars. 'Iron' bombs were also often used, the 'Wild Weasel' aircraft frequently being accompanied by F-105Ds or McDonnell Douglas F-4 Phantoms.
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<p>A total of 86 F-105Fs was eventually reconfigured for such duties, approximately 60 of these being subject to a major modification effort which resulted in what was known initially as the EF-105F and later as the F-105G. Instantly recognizable by the fuselage fairings for the ALQ-105 jamming gear, the F-105G was wholly compatible with the AGM-78 Standard ARM from the outset, this weapon requiring a sophisticated avionics suite to sort and select signals emanating from ground-based radars. AGM-45 Shrikes also formed part of the F-105G's arsenal while both 'Wild Weasel' types retained the M61 cannon along with 1,028 rounds of ammunition.
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<p>Introduction of 'Wild Weasel'-configured F-105Fs to combat occurred in the summer of 1966 and from then until the end of the conflict in 1973 the Thunderchief constituted the backbone of anti-SAM forces, F-105Gs assuming responsibility for this dangerous task during the course of 1970. These were in fact the last 'Thuds' to see combat, operating from Korat as part of the 388th TFW. Following the ceasefire, all surviving F-105Gs congregated at George AFB, California, where they served with the 35th TFW until supplanted by F-4G Phantoms in the late 1970s, at which time approximately 25 were passed to the 128th TFS, Georgia ANG at Dobbins AFB, where they were retired in August 1983.
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<p>The only other Thunderchief model to undertake combat, the F-105D, suffered what can only be described as severe attrition, with well over half of the 610 aircraft built falling victim to North Vietnam's defenses. Accordingly, following their withdrawal from Southeast Asia in 1969-70, these were quickly passed on to second-line elements of the ANG and AFReS. Progressive updating of these forces had, in turn, brought about a gradual phase-out of the surviving aircraft by 1984.
<item><hi format=bold>Powerplant:</hi> one Pratt & Whitney J75-P 19W turbojet rated at 17,200 lb (76.51 kN) thrust dry and 24,500 lb (108.98 kN) thrust with afterburning; water injection permits 60-second rating of 26,500 lb (117.88 kN) thrust in afterburner mode
<item><hi format=bold>Performance:</hi> maximum speed 1,390 mph (2,237 km/h) or Mach 2.1 at (36,000 ft (10,970 m ); initial climb rate 34,400 ft (10,485 m) per minute in clean configuration; service ceiling 41,200 ft (12,560 m) on a typical mission; range 920 miles (1,480 km) with two 450-US gal (1,703-liter) drop tanks underwing, one 650-US gal (2,461-liter) drop tank on centerline and two AGM 12 Bullpup ASMs; ferry range 2,390 miles (3,846 km) with maximum external fuel at 584 mph (940 km/h)
<item><hi format=bold>Weights:</hi> empty 27,500 Ib (12,474 kg); maximum overload take-off 52,838 lb (23,967 kg)
<item><hi format=bold>Dimensions:</hi> span 34 ft 9 in (10.59 m); length 64 ft 4 in (19.61 m); height 19 ft 7 in (5.97 m); wing area 385.0 sq ft (35.77 m<su>2</su>)
<item><hi format=bold>Armament:</hi> combinations of 750-lb (340-kg) M117 bombs, 1,000-lb (454-kg) Mk 83 bombs, 3,000-lb (1,361-kg) M118 bombs, AGM 12 Bullpup ASMs, AIM-9 Sidewinder AAMs, 2 75-in (70-mm) rocket pods, napalm containers, Mk 28/43 special weapons, chemical bombs, leaflet bombs, 5-in (127-mm) rocket pods and MLU-10/B mines; also one M61 Vulcan 20-mm cannon with 1,028 rounds of ammunition
