The complexity of the bombing and navigation system of the single-seat F-105D left the Air Force in need of a two-seat training version for use in instructing new pilots in the use of these highly complex systems. The two-seat F-105C had originally been intended for this role, but its development had been terminated in 1957. A second two-seat version, the F-105E, based on the F-105D airframe but fitted with two tandem ejector seats underneath a single-piece bubble canopy, was cancelled in May of 1959 as being too expensive, freeing up funds for more F-105Ds. Nevertheless, the Air Force still perceived a need for a two-seat conversion trainer.
The F-105F was the result. The F-105F was a minimal-change derivative of the F-105D, in which the two crew members were seated in tandem ejector seats underneath separate clamshell-type canopies. The cockpits were provided with dual controls. The rear cockpit was a virtual duplicate of the front cockpit (including a second R-14A radar scope), so the rear pilot could fly the mission even if the front pilot were incapacitated. A transfer system in the F-105F allowed each crew member to monitor or control all or any of the aircraft's subsystems.
The fuselage of the F-105F was about five feet longer than that of the F-105D and the tailfin and rudder were taller and larger in area. The F-105F was nearly 2000 pounds heavier than the F-105D, and it retained many of the features of the D, including the retractable midair refuelling probe. Although originally intended as an advanced trainer, the F-105F retained the full combat capability of the single-seat F-105D, including the all-weather R-14D radar system, the AN/ASG-19 Thunderstick fire control system, and the nuclear delivery mission. Externally, it had the same 5 hardpoints under the wings and the fuselage that the F-105D, and the internal weapons bay was of the same size. It had a performance that was within a couple of a percent of that of the F-105D.
The maiden flight of the first F-105D (62-4412) was on June 11, 1963. It reached a speed of Mach 1.15 on this flight. Service introduction was in December of 1963 with the 4520th Combat Crew Training Wing based at Nellis AFB and with the 4th Tactical Fighter Wing based at Seymour-Johnson AFB, where it flew alongside the F-105Ds already serving.
143 F-105Fs were built in the years 1963 to 1964. These aircraft were actually originally all ordered as single-seat F-105Ds, but before they could be built the Air Force specified that they be delivered as two-seat F-105Fs. No Thunderchiefs were actually procured as F-105Fs from the beginning.
The delivery of the last F-105F (63-8366) in January 1965 marked the end of Thunderchief production. In the early 1960s, Secretary of Defense Robert McNamara had sought to bring defense budgets under control by adopting joint service programs such as the F-111 TFX. It was decided to adapt the US Navy/Marine Corps F-4 Phantom as the Air Force's primary fighter-bomber, and the F-105 program was terminated. Later on in the 'sixties, the mounting losses of F-105s in combat over Vietnam led the Air Force to give some consideration to reopening the F-105 production line, but nothing ever came of the idea. The closing down of Thunderchief production marked the end of the line for Republic Aviation as a manufacturer of fighter aircraft.
Although the visibility from the rear cockpit was too limited to make the F-105F a practical conversion trainer, it was nevertheless a useful aircraft for check rides and in instructing new pilots in the use of the complex bombing and navigational equipment.
The F-105F is primarily remembered today for its role as a Wild Weasel aircraft, a type of aircraft originally designed for the suppression of North Vietnamese surface-to-air missile radar sites. When American bombing raids against North Vietnam began in 1964, combat losses of US aircraft began to mount alarmingly. Many of these losses were caused by the increasingly effective use by the North Vietnamese of radar-guided surface-to-air missiles. Someone in the USAF got the bright idea that the best way to defeat the surface-to-air missile threat would be to destroy or otherwise shut down their guidance radars, leaving enemy missile sites effectively blind and impotent. The project was given the name Wild Weasel, after the fierce little mammal which has a reputation of being so fearless that it pursues its prey into its very den.
The first Wild Weasel aircraft were North American F-100F Super Sabre two-seat fighter-bombers which were modified in 1965 for the role of identifying, marking, and attacking North Vietnamese SAM sites, particularly their radar installations. They were fitted with special equipment designed to detect enemy radar emissions and to determine the location of their transmitters. Once the sites were located and identified, fighter-bombers accompanying the F-100F aircraft would then attack the target with iron bombs. The F-100F Wild Weasel I program claimed credit for nine confirmed SAM radar kills. An undetermined number of other enemy radars were forced off the air as a result of Wild Weasel I activities.
After the F-100F two-seaters had proven the feasibility of the general concept, the same sort of adaptation was made to the vastly more capable F-105F two-seater. 86 F-105Fs were selected for modification as Wild Weasel III aircraft, which was over half the total F-105F production. These planes were known within the Air Force as EF-105F, but the official designation remained F-105F. The electronic weapons officer in the rear seat of the Wild Weasel F-105F operated a battery of sophisticated electronic equipment which was capable of detecting the emissions from enemy radars and determining the exact location of their sources. Once these sites were identified, the F-105F could attack them with a battery of AGM-45A Shrike antiradar missiles, which were designed to home in on an enemy radar transmission and follow it all the way to its source and destroy it. The Wild Weasel F-105F could also carry powerful jamming equipment which was designed to confuse the enemy radar installation or to misdirect any surface-to-air missiles that might be launched. Alternatively, the F-105F crew could direct other aircraft toward the missile sites, which would be attacked by iron bombs or cannon fire.
The first modified F-105F (62-4416) flew on January 15, 1966, and test and development work was completed in May. The first pilots and electronic warfare officers came from the F-100F Wild Weasel detachment, which was training at Eglin AFB in Florida. The first Wild Weasel F-105Fs left for Southeast Asia in June of 1966.
The first F-105F Wild Weasel III missions were flown in June 1966. In a typical mission, a Wild Weasel F-105F would accompany each flight of two or four F-105Ds. This helped to cut the loss rates of the single seaters tremendously. However, because of the nature of their missions, losses of the Wild Weasel F-105Fs were heavy, with five of the first eleven examples having been lost by the end of August.
North Vietnamese MiG-17 and MiG-21 fighters were also a menace, and many a bombed-up F-105D Thunderchief fell to the guns and missiles of these aircraft. In order to counter the MiG threat, a few F-105Fs were modified to carry Hallicrafters QRC-128 VHF jammers that were intended to block communications between MiG pilots and their ground controllers. The North Vietnamese were trained in Soviet tactics, which called for rigid ground control of airborne interceptors and permitted only limited pilot initiative. When communication was cut, tactics usually called for the MiG pilots immediately to return to base. The code name for this project was Combat Martin. Six of these planes were later returned to their original configuration and were eventually brought into the Wild Weasel III program.
Many targets in the North had to be attacked at night to reduce losses. Several F-105Fs were modified under the Commando Nail program with an improved R-14A radar with higher resolution which made it possible to achieve sharper target definition. In addition, the pilot's weapons release switch was modified to enable the rear seat pilot to control the bomb release. A better resolution scope was installed in the rear cockpit, and special cabin lighting was provided. Commando Nail F-105Fs operated by selected crews (Ryan's Raiders) from the 44th TFS at Korat flew numerous hazardous all-weather low-level bombing missions over North Vietnam, the first of these being on April 26, 1967. The Commando Nail F-105Fs were also used to develop tactics for the possible deployment of B-58 Hustlers to Southeast Asia. In the event, the four-engined supersonic bomber never did serve in the Vietnam conflict. Six of these Commando Nail F-105Fs were later returned to their original configurations and were brought into the Wild Weasel III program
Throughout the Southeast Asia War, the F-105F was repeatedly modified to meet changing conditions. They were equipped with armor plating, backup flight control systems, X-band beacons, new radar altimeters, and AN/ASG-19 Thunderstick gun bombsights which provided for automatic or manual and blind or visual weapons delivery, with automatic or manually-controlled weapons release. The pilot ejector 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. Several F-105Fs were equipped with a combat camera mounted in a protrusion on the lower nose just behind the radome. Most F-105Fs were fitted in the field with ram air scoops on the rear fuselage to address an afterburner cooling problem which had resulted in some engine fires.
Although the last F-105D was withdrawn from Southeast Asia in October of 1970, the two-seat F-105F Wild Weasel remained in Southeast Asia until the end of US involvement in Vietnam. However, they were gradually replaced in their Wild Weasel role by the McDonnell F-4G Wild Weasel IV. Their final wartime role was as an escort for high-flying B-52s during the Linebacker I and Linebacker II operations, which culminated in the Christmas 1972 offensive against Hanoi that finally forced the North Vietnamese government to the conference table and ended the American involvement in the war.
The following Air Force units flew the F-105F:
The following Air Force Reserve units operated the F-105F:
Surviving F-105Fs from Vietnam were transferred to the Air National Guard as they were replaced in Air Force service by F-4Gs. In 1971, the Air National Guard received its first 8 F-105Fs. By mid-1973, only 17 F-105Fs remained in service, 5 with the Air Force and 12 with the ANG. Several examples served with the 508th TFG and with the Georgia Air National Guard until 1981, when the last Thunderchiefs were finally retired.
The following Air National Guard units operated the F-105F:
62-4412/4447 Republic F-105F Thunderchief 63-8260/8366 Republic F-105F Thunderchief
Engine: One Pratt & Whitney J75-P-19W turbojet, rated at 17,200 lb.s.t. dry and 26,500 lb.s.t. with afterburner. Performance: Maximum speed: 1386 mph at 38,000 feet (Mach 2.1), 876 mph at sea level (Mach 1.15). Initial climb rate was 34,500 feet per minute (at 39,350 pounds). Combat radius was 740 miles with 8 750-pound bombs. Fuel: Total internal fuel capacity was 1160 US gallons in seven tanks (including 25 gallons in the fuel lines). The internal weapons bay can accommodate a 390-US gallon fuel tank in place of the "special store". The fuel load could be further augmented by two 450 US-gallon drop tanks on the inner underwing pylons and an additional 450 or 600 US gallon drop tank carried on a pylon underneath the fuselage, bringing total maximum fuel capacity to 3100 US gallons. Dimensions: wingspan 34 feet 11 1/4 inches, length 69 feet 7 1/3 inches, height 20 feet 2 inches, wing area 385 square feet. Weights: 40,073 pounds loaded (clean), 54,027 pounds maximum takeoff. Armament: Armed with one 20-mm M61A1 rotary cannon with 1029 rounds. Up to 8,000 pounds of ordinance could be carried in the internal weapons bay. In addition, a further 6000 pounds of ordinance could be carried on external weapons racks (four underneath the wings, one underneath the fuselage). Typical weapons load include 16 750-pound bombs, 9 LAU-3/A or LAU-18/A rocket pods, or four AIM-9B Sidewinder infrared homing missiles in the intercept role