On February 8th Group Captain Jock Heron OBE made another visit to Kingston to tell of his experiences as an exchange officer with the USAF flying the magnificent Thunderchief. Jock described it as “big, elegant, capable and a delight to fly”. With honest handling it was like a big, heavy Hunter. It was large: 65 ft long with a 35 ft span and was 20 ft high. Wing area was 385 sq ft, empty weight 29,000 lb, with a max take-off weight of 54,000 lb.
Its ancestor was Republic’s first jet, the F-84 Thunderjet, a clean, single engined, straight wing fighter with a nose intake. It was a totally new design owing nothing to its famous predecessor, the piston engined P-47 Thunderbolt; the F-84 F had swept wings. Hawker, meanwhile had done the Sea Hawk and Hunter and were planning the P.1121, another large, heavy fighter with, as Jock put it, F-105 potential. However, the short-sighted 1957 defence White Paper led to the project’s cancellation by HSA.
Republic Chief designer Alexander Kartveli’s Advanced Project 63 was submitted in 1952 and the first YF-105A flew in 1955 powered by the interim 15,000 lb thrust Pratt & Whitney J-57, an engine similar to Bristol’s Olympus. The improved YF-105B with an area ruled fuselage, swept forward Ferri variable geometry intakes and the P&W J-75, flew in 1956. The F-105B with the P&W J-75 of 24,000lb take-off thrust entered limited service in 1958. It had the APG-31 ranging radar, a toss bombing computer, a Doppler navigator and autopilot.
The F-105D entered service in 1960 with an improved engine with water injection which raised the thrust to 26,500 lbs, all-weather ground attack capability with a NASARR 14A multi-mode radar providing air-to-air search and track, ground mapping, targeting, terrain avoidance and contour mapping. It could carry a Mk28 or 43 nuclear weapon internally with centre line and underwing drop tanks. Some 600 D models were built and served in the USA, Europe and Japan. Its operational roles included nuclear alert (equivalent to the RAF quick reaction alert , QRA), air refuelled deployment and Vietnam combat operations.
Jock became acquainted with the Thud in 1965 at Nellis Air Force Base (AFB) near Las Vegas as an exchange pilot with the 4526th combat crew training wing where he became an instructor. The training syllabus was 120 hrs in 6 months. He found the cockpit comfortable with a 31 inch sill width but with a poorly placed radar screen, low and behind the stick. It had ailerons and spoilers, and a variable gear tailplane. The built-in M.61 cannon had a 100 rounds per second rate of fire. The Thud weighed 29,000 lb empty and carried 10,000 lb of fuel including a bomb-bay tank. For air-to-air refuelling there was a retractable probe for probe and drogue operations and a receptacle for flying boom refuelling.On landing he was met by two vehicles, one carrying engineers, the other contained two “suits”. The presence of a foreign national in a USAF aircraft was perplexing and Jock suffered assertive questioning about his need to land at the secret base. However, the engineers reported later that the F-105’s cold air unit had seized, igniting the lubricant in the air supply lines so the emergency had been genuine. Jock was then treated in a fairly relaxed manner before being invited outside to watch a Lockheed A-12, (the Mach 3 single seat CIA predecessors of the SR-71 Blackbird) taxying from a nearby hangar followed by an F-101 chase.. Jock also flew Transpacific in 1966 from California (McClellan AFB) to Okinawa (Kadena AFB) via Hawaii (Hickham AFB) and Guam (Andersen AFB).
The F-105D’s most important deployment was to Thailand for operations over Vietnam. They flew from Takhli and Korat Royal Thai Air Force Bases over Laos and Cambodia to Hanoi for the “Rolling Thunder” campaign. The only permitted route to the city was from ‘Thud Ridge’ so the enemy knew exactly where the attacks would come from. The normal weapon load would be six M117 750 lb bombs, two 450 gal drop tanks and a jamming pod outboard. The maximum loads were sixteen 750 lb bombs with tanks or two 3000 lb bombs with a centerline fuel tank. For “Wild Weasel” missions the two seat F-105F or G would carry a rear electronic warfare officer (EWO) and be armed with Shrike anti-radar missiles. The hazardous task was to go in ahead of the F-105 and F-4 Phantom fighter-bombers, lure the defensive surface-to-air missiles (SAMs) to reveal themselves and knock out the batteries; first in, last out! Unbelievably, target information was passed by the US Government to the Swiss Embassy for onward transmission to the North Vietnamese Government, supposedly to reduce civilian casualties. During the Viet Nam war 395 F-105s were lost and 156 aircrew killed; hardly surprising.