Built by Republic Aircraft, the F-105 was designed as a supersonic, single-seat, fighter-bomber able to carry nuclear weapons and heavy bomb loads over great distances at high speeds. It made its first flight on October 12, 1955. The first F-105D (58-1146) flew on 9 June 1959. The TAC at Nellis AFB, Nevada, accepted the first F-105D on September 28, 1960. The initial contract for 59 F-105Ds was increased to nearly 300 by the end of 1961. Ultimately, 610 F-105Ds were built.
The F-105D variant was an all-weather fighter-bomber version, fitted with monopulse and Doppler radar for night or bad weather operations. This radar was capable of terrain avoidance commands. The original weapons bay, designed for nuclear stores, was sealed and fitted with additional fuel tanks. Bombs were carried on multiple weapons racks on the centerline of the fuselage, and on wing pylons. The aircraft was fitted with a retractable in-flight refueling probe. During the Vietnam War, F-105 units operated from bases in Thailand.
The F-105D was the major production version of the Thunderchief series. It was an all-weather version of the day-only F-105B. Externally, the -D differed from the -B in having a slightly longer and wider nose, which housed the AN/ASG-19 "Thunderstick" system designed to meet new all-weather requirements specified in the November 1957. The AN/ASG-19 was designed around the NASARR R-14A all-purpose monopulse radar. This was optimized in both air-to-ground and air-to-air modes and was capable of performing both low-level and high-altitude missions. The aircraft was equipped with a General Electric FC-5 flight control system that operated in conjunction with the R-14A radar to provide the F-105D with full all-weather capability. The system included a bomb-toss computer, a sight system, an AN/APN-131 Doppler navigator, an air data computer, missile launch computer, autopilot, and search and ranging radar. The radar installation also incorporated a terrain guidance mode permitting the pilot to descend through bad weather in unfamiliar territory and to hug the ground, avoiding detection.
A J75-P-19W jet engine equipped with water injection powered the F-105D. A new cockpit was provided with a vertical instrument panel. The higher gross weight of the -D version required the provision of a stronger main landing gear and more robust brakes. In addition, a pitot tube was mounted on the extreme tip of the nose. The aircraft were otherwise quite similar to other F-105s. The F-105D had an arrester hook mounted on the rear of the ventral fin. This hook was intended to engage a wire in case the aircraft overshot the end of the runway during a landing. The Thunderchief was not capable of carrier-based operations.
The 335th Tactical Fighter Squadron of the 4th Tactical Fighter Wing was the first unit to receive the new F-105D. It exchanged its older F-105Bs for the new D-model in June 1960. The Thunderchief's first European deployment came in May of 1961, when the 36th TFW based at Bitburg in Germany received its first F-105Ds. It was soon followed by the 49th TFW. F-105Ds were also supplied to the 4520th Combat Crew Training Wing based at Nellis AFB, the 36th TFW (22nd, 23rd, and 53rd Squadrons), the 49th TFW (7th, 8th, and 9th Squadrons), the 18th Fighter Bomber Wing (12th, 44th, and 67th squadrons), the 355th FBW (354th and 357th Squadrons), and the 388th TFW. The 36th and 49th Wings went to Europe at the end of 1961 to provide NATO with nuclear strike capability. The 8th and 18th Wings were stationed in Japan from 1962 onwards.
In June 1961, during special tests at Eglin AFB in Florida, the F-105D demonstrated its ability to carry and deliver seven tons of bombs. This was the heaviest load of bombs ever carried by a single-engine fighter. This feat was repeated in October 1961 at Fort Bragg, North Carolina. President Kennedy was one of the brass hats in attendance.
The F-105D was originally intended for the nuclear strike role, with the primary armament being a "special store" (a nuclear weapon) housed in the internal weapons bay. This weapon was usually a Mk 28 or a Mk 43. However, a Mk 61 could be carried underneath the left or right inboard under wing pylon and a Mk 57 or a Mk 61 could be carried underneath the centerline pylon. But, as nuclear war became less and less likely, the nuclear weapon carried in the internal weapons bay was usually replaced by a 390-gallon internal fuel tank.
The Thunderchief made an excellent tactical bomber. With the exception of the ammunition for the M61A1 cannon, all the ordnance was carried externally. With multiple ejector racks the F-105D could carry an impressive load of external fuel, ECM gear, and up to eight 750-lb. bombs on long-range missions. On short-range missions, it could carry sixteen 750-lb. bombs. Alternative combat loads consisted of two 3000-lb. bombs or three drop tanks. On a typical mission over North Vietnam, the F-105D carried six 750-lb. bombs or five 1,000-lb. bombs, along with two 450 US-gallon drop tanks. The -D also carried the Martin AGM-12 Bullpup air-to-surface missile. This weapon proved ineffective in Vietnam against hardened targets. The F-105D was also capable of carrying 2.75-inch rocket pods, napalm canisters, as well as four AIM-9 Sidewinder infrared homing air-to-air missiles. The M61A1 Gatling-type, 20-mm cannon proved highly effective in the dual role of air-to-air combat and ground strafing. With its size and range, the F-105D could carry twice the bomb load further and faster than the F-100. Initially, the hydraulic system was susceptible to failure due to battle damage. Modifications in that system improved the F-105s ability to withstand enemy fire.
The F-105D was somewhat less successful as an air-to-air weapon, often challenged by enemy MiG-17 and MiG-21 fighters. The "Thud" was not as maneuverable as more nimble MiGs. Additionally, because the aircraft's ordnance was carried externally, maximum performance could only be reached once the bombs and rockets had been jettisoned or after the aircraft was clear of the target. However, when attacked, the enormous thrust of the J75 engine enabled a "slick" Thunderchief to fly supersonic "on the deck", quickly leaving its pursuers behind. F-105Ds did manage to shoot down 27-1/2 enemy fighters during 1966 and 1967. 20-mm Vulcan cannon shots accomplished most of these, and two were downed by Sidewinders.
Strikes against targets near Hanoi involved 1250-mile round trips from Tahkli. High ambient temperatures, normal for Thailand, handicapped takeoff performance. This required takeoffs with less than a maximum fuel load. Consequently, F-105Ds operating out of bases in Thailand usually had were refueled by KC-135s over Laos before crossing into North Vietnam. Refueling operations often were repeated on the way back, especially if afterburners had been used to evade enemy defenses. On occasion, KC-135 tankers would take extra risks and penetrate into North Vietnamese airspace to come to the rescue of F-105Ds short on fuel or suffering from battle damage. Many an F-105 pilot escaped from being an unwilling guest in the "Hanoi Hilton" because of the courage and skill of KC-135 crews. When approaching Hanoi from Thailand, the F-105Ds had to cross "Thud Ridge", the name given by Thunderchief pilots to a series of hills located between the Red and Black Rivers. Once over "Thud Ridge," the F-105s would approach their targets low and fast, an environment in which the F-105D excelled. Maneuverability and stability during low-level, high-speed flight were excellent because of the aircraft's high wing loading.
Throughout the Vietnam War, the F-105D was modified to meet changing conditions. Many F-105Ds were retrofitted with armor plating, backup flight control systems, X-band beacons, more effective radar altimeters, and AN/ASG-19 Thunderstick gun/bombsights. This sight provided for blind or visual weapons delivery, using automatic or manually-controlled weapons release. The pilot ejection seat was improved and AN/APR-25(U)-26(V) radar homing and warning (RHAW) antennae were added to the tip of the vertical fin. The RHAW helped to warn the pilot when MiGs were sneaking up on his tail and targeting his aircraft with radar. In addition, F-105D refueling probes were improved.
Several F-105Ds were provided with a combat camera mounted in a protrusion on the lower nose just behind the radome. Many F-105Ds were fitted in the field with ram air intake scoops on the rear fuselage to address an afterburner cooling problem that had resulted in some engine fires. Unfortunately, heat and high humidity often played havoc with the reliability of delicate electronic systems, with failures often occurring just at inopportune times.
In 1969, 30 F-105Ds were re-equipped with AN/ARN-92 LORAN equipment for more precise navigation. These planes could be identified by the presence of a long dorsal spine extending all the way from the canopy to the tail fin. They were known as "Thunderstick IIs," T-Stick II for short. The first T-Stick aircraft flew on August 9, 1969. They served with the 23rd TFW in the continental US, but never saw any combat.
Thunderchiefs in Vietnam flew more than 20,000 combat missions. 350 Thunderchiefs (-Ds and -Fs) were lost in combat, most of them to North Vietnamese anti-aircraft fire. This was more than half of all Thunderchiefs built. 126 F-105s were lost in 1966 alone, 103 of them to AAA. At one stage in 1965-1968, it was calculated that an F-105 pilot stood only a 75 percent chance of surviving 100 missions over North Vietnam.
Following their withdrawal from Southeast Asia, the few Thunderchiefs to survive combat in Vietnam served with active duty Air Force units for two more years, primarily with the 23rd TFW at McConnell AFB and with the 18th TFW at Kadena AB on Okinawa. Beginning in 1971, some of these aircraft were handed over to the Air National Guard. The ANG operated them until 1983 when the last Thud was retired. Other F-105Ds were transferred to the Air Force Reserve.
The Air Force Reserve acquired its first F-105Ds in July 1972. The last Air Force reserve unit to operate the F-105D, the 466th TFS of the 508th TFW, made the last flight with the type on February 25, 1984.
