There was talk about canceling the F-105D program because of several groundings of the fleet following engine problems that resulted in two fatal accidents
The F-105 Thunderchief originated from a 1951 effort to find a replacement for the F-84F fighter-bomber. Its prototype took to the air for the first time in October 1955, and Republic handed over the first operational aircraft to the U.S. Air Force (USAF) in 1958.
The F-105D model—of which the first example flew on June 9, 1959, with a total of 610 eventually produced—was an all-weather fighter-bomber variant. It was equipped with monopulse and Doppler radar systems, enabling operations at night and in poor weather conditions. The original internal weapons bay, initially intended to carry nuclear ordnance, was closed off and repurposed to house extra fuel tanks. Conventional bombs were instead mounted on multiple ejector racks along the fuselage centerline and on underwing pylons. The aircraft was also outfitted with a retractable probe for aerial refueling.
However, despite these advantages, there were discussions about terminating the F-105D program after repeated fleet groundings caused by engine problems, resulting in two fatal crashes.
According to Ted Spitzmiller’s book Century Series: The USAF Quest for Air Supremacy 1950–1960, as with earlier F-105 versions, the use of production blocks created configuration differences that complicated maintenance procedures and spare parts ordering. In particular, issues with routing and securing the extensive wiring, along with the hydraulic and fuel lines, led to chafing, which in turn caused electrical shorts and fluid leaks, driving up maintenance demands and contributing to several accidents. To address these problems, the Air Force implemented a standardization initiative known as “Project Look-Alike” between 1962 and 1964 to inspect and correct these systems.
In addition, steps were taken to resolve the issue of water seeping into various small gaps and cavities in the airframe, which was causing serious electronic failures and other maintenance difficulties. This problem became especially apparent during deployments in Europe, where seasonal weather conditions were much harsher. Once access panels were properly sealed and the aircraft were coated with a silver lacquer to protect as much of the surface as possible, the frequency of these failures declined.
Another recurring issue involved excessive heat in the afterburner (AB) section of the fuselage. To fix this, engineers added two extra air inlets on each side of the rear fuselage, allowing more outside air to flow in and cool the area.
Howard Plunkett, author of the book F-105 Thunderchiefs: A 29-Year Illustrated Operational History, with Individual Accounts of the 103 Surviving Fighter Bombers, says, “A ‘constant problem’ is a bit understated. Fuel leaks and overheating caused explosions and aircraft losses. Safety Pack II was the mod that installed the cooling scoops on the left fuselage, among other things, during March–July 1965. It was probably the most significant mod to the F-105 and fixed the problem in time for combat deployments that year.”
Because of all these issues, the initial plan to build 1,500 aircraft was sharply reduced.
In the end, as Spitzmiller recounts, although “Thunderchief” sounded impressive to Republic and its public relations team, the pilots who flew this heaviest fighter of its era—whose high wing loading meant it dropped rapidly if the engine failed—gave it a different nickname. Whether inspired by the crash of 50,000 pounds of metal slamming into the ground or as a playful shortening of the name of Howdy Doody’s TV adversary, Chief Thunderthud, the F-105 was affectionately dubbed the “Thud” by the aircrews and maintainers who worked with it.
Century Series: The USAF Quest for Air Supremacy, 1950-1960 is published by Schiffer Publishing and is available to order here.
Photo by U.S. Air Force
