F-105D "Thunderchief"
New features to the F-105D included a higher thrust J-75-P-19W engine with water injection, a cockpit with a vertical instrument panel, a bad weather navigation system, attack equipment, and integrated instruments. The last Ds off the line could refuel from either the flying boom or hose drogue type tanker.
Configuration of the D cockpit was finalized by a Mockup Board on 11 December.
Republic requested new production schedules. The contractor claimed that the F-105D, although similar in appearance to the F-105B would be different enough to make it difficult to use the B production line, even with many modifications. The higher gross weight of the new model series would require stronger main gear, wheels, and brakes. The F-105D's improved engine would necessitate changes in the fuselage and intake ducts. Fabrication time, Republic stated, would be raised from 144 to 214 workdays.
General Operationl Requirement (GOR) 49, as revised 22 November 1958, was amended. The amendment required that the F-105 be capable of delivering at least two of the air to surface missiles specified in GOR 166 of October 1957.
Production of an increased number of F 1051)s was programmed at the expense of the two place F 105E. The Air Force hoped that cancellation of the high cost F 105E and replacement by the cheaper F 105D, on a one for one basis, also would enable Republic to speed production.
Despite the efforts expanded on the aircraft and its components, the F-105B was still not fully proven when the first F-105D was accepted by the Air Force. The engineering changes made on the F-105B under Project Optimize and the subsequent Prove Out testing of the MA-8 fire control system were but one example of the difficulties experienced with the new components and their integration into the weapon system. Other modifications were either established or proposed for both the production completed F-105Bs and the incoming F-105Ds. To avoid a variety of aircraft configurations, the Air Force decided to process these modifications as a single package. The first production black box aircraft, received at Eglin AFB on October 27, 1960, upon evaluation proved to be adequate and the F-105D's operational capability in all visual and blind bombing was recognized. The black box modification of all F-105 aircraft was confirmed in November. Republic's lack of experience in delivering aircraft with the modification affected production schedules and delayed various phases of the F-105D flight testing program.
During tests, the F-105D encountered problems similar to those that had plagued the F-105B. Category I flight tests were delayed because of difficulties with the J-7b engine and speed restrictions placed on the aircraft. Category II testing, scheduled to start in May 1960, did not begin until 26 December because of the black box modification and other production slippages. The F-105D's airframe and engine had undergone evaluation either on the F-105B or during the D model's Category I tests. This let the Air Force cut short the delayed Category II tests that centered on the instrument display as well as the fire control and navigation systems. Conducted by the 335th TFS at Eglin AFB, these tests ended on 31 October 1961. Category III flight tests were also reduced and conducted by the 335th but took place at Seymour Johnson AFB, which became the collecting point for all specialized test equipment and spare parts prior to TAC acceptance of the first F-105D. Most of the support problems encountered during the Category III testing of the F-105B were eliminated.
TAC's 4th Fighter Wing was first to receive the aircraft. F-105Ds began reaching USAFE's 36th Tactical Fighter Wing in May 1961. Deliveries to PACAF started in October 1962. Between 1961 and 1967, the F-105D was grounded a number of times, after experiencing various operational problems, including the failure of the fuselage frame, chafing and flight control deficiencies, engine failures, fuel leaks, and malfunctions of the fuel venting systems.
All F-105Ds were grounded for inspection after the aircraft's main fuselage frame failed during a routine laboratory fatigue test at Wright-Patterson AFB. Ensuing tests confirmed that the frame retained considerable strength after cracking. Republic had suitable adapters and tools to do the corrective work required.
In June 1962, following two major accidents at Nellis AFB, all F-105B and D aircraft were grounded for correction of chafing and flight control deficiencies. The project, referred to as Look Alike and started in July, was expected to be done quickly, but continuous operational difficulties caused it soon to grow into an extensive, $51 million modification program. The 2 year spanned modifications, grouped under Look Alike, were accomplished in two phases, the first of which was completed in November 1962 by the Air Force with the assistance of several technicians from Republic. The second phase, extended to include a dual in-flight refueling capability for the last 20 F-1051s produced, was done entirely by Republic and did not end until mid 1964.
Despite the successful completion of Look Alike, the efficiency of the F-105Ds had not peaked. At the time production ended in early 1964, they experienced a series of accidents due to engine failures, fuel leaks, and malfunctions of the fuel venting systems. This in turn added a shortage of J-75 engines to the similar problems hampering F-105D operations from 1964 through 1968.
F-105Ds, flying from Korat AB, began striking carefully selected targets north of the 17th parallel in early 1965. While participating in tactical air strikes over South Vietnam, in 1966 and subsequent years, they carried out more strikes against the North than any other USAF aircraft. Operating against ever stiffening defenses, the F-105Ds also led in SEA battle losses. The steady loss of F 105 aircraft to enemy action, accidents, and normal attrition necessitated urgent repairs, cannibalization of the more badly damaged aircraft, and depletion of USAFE and TAC inventories. TAC's resources for training and support of the combat effort were also reduced.
The F-105Ds were repeatedly modified to meet changing SEA combat requirements. They were equipped with armor plates, backup flight control systems, X band beacons, new radar altimeters and ASG 19 gun bombsights. Primarily designed to carry nuclear bombs, their conventional bombing capability was increased. The pilot ejection seat of all F-105 aircraft was improved as were the refueling probes of the early F-105Ds. Modifications, first impeded by sparse funds often were delayed by technical difficulties. A most important and complex modification (putting ECM pods on the aircraft's wings) began in 1966 and consumed several years. Another crucial modification, started in 1966 and hindered by numerous problems, would give 30 F-105Ds improved visual bombing accuracy, a more precise navigation system, and a better blind bombing capability. An overriding problem was the poor reliability and rising cost of the AN/ARN-85 LORAN system first considered. This problem persisted until new testing began at Eglin AFB in September, 1969. The T-Stick II/Loran prototype aircraft was then equipped with the AN/ARN 92 (produced by International Telephone and Telegraph) and successfully flight tested. Still, modification of the 30 aircraft was not completed until late July, 1971.
As war losses foretold its gradual removal, the F-105 was increasingly praised for its payload, range, and exceptional speed at low altitudes. It was praised as the "hardest worker" of the Vietnam War by pilots who regretted that the planes were not being replaced. Loaded with twelve 750 1b bombs, the F-105D was faster than any other available USAF aircraft flying under the same conditions.
There were no other configurations. Production of a reconnaissance version of the F-105, after progressing through a February 1954 mockup inspection, was cancelled on 20 July 1956. Amendment No. 2 to the revised GOR of November 1957, published on 7 December 1960, reinstated as well as enlarged the project by calling for a reconnaissance version of the F-105 model series D. The new reconnaissance aircraft, while retaining the strike capability of the F-105D, would be equipped with a pod containing side looking radar, infrared sensors and a variety of cameras. In flight development of films and ejection of film casettes were included in the specific. operational requirements issued in December 1960. Revival of the project, however, was of short duration. One year later, on 23 December the new RP-105 contract was terminated in favor of a reconnaissance version of the F-4C Phantom II, soon to be produced by the McDonnell Aircraft Corporation. SOR 49-2 was cancelled on 30 April 1962, its requirements being transferred to SOR 196, issued for the RF-4C in the spring of 1962.
The Air Force accepted 17 F-105Ds in FY 60, 149 in FY 61, 171 in FY 62, 198 in FY 63, and 75 in FY 64.
The F-105Ds began to see action in Southeast Asia 1 year later. Ensuing battle losses were considerable, and reopening of the production line was considered in mid 1967. The project, however, did not materialize.
The Flyaway Cost Per Production Aircraft was $2.14 million-airframe, $1,472,145; engine (installed), $244,412; electronics, $19,346; armament, $167,621; ordnance, $19,346.
Phasing out of remaining F l05Ds (roughly one fourth of some 600 productions) took shape in November 1970, when two ANG units were alerted to their impending conversion. F-105Ds began reaching the 184th Tactical Fighter Training Group, McConnell AFB, and the 192d Tactical Fighter Group (TFG), Byrd Field, Va., in January 1971. Conversion of a third ANG unit, the 113th TFG, Andrews AFB, Md., swiftly followed. By mid 1973 USAF active rolls showed 6 F-105Ds left-two were used for special tests, the other four for training.
As war losses foretold its gradual removal, the F-105 was increasingly praised for its payload, range, and exceptional speed at low altitudes. It was praised as the "hardest worker" of the Vietnam War by pilots who regretted that the planes were not being replaced.
Loaded with twelve 750-1b bombs, the F-105D was faster than any other available USAF aircraft flying under the same conditions.
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