Republic F - 84 Thunderjet The Republic F - 84 Thunderjet was an American turbojet fighter - bomber aircraft . Originating as a 1944 United States Army Air Forces ( USAAF ) proposal for a " day fighter " , the F - 84 flew in 1946 . Although it entered service in 1947 , the Thunderjet was plagued by so many structural and engine problems that a 1948 U . S . Air Force review declared it unable to execute any aspect of its intended mission and considered canceling the program . The aircraft was not considered fully operational until the 1949 F - 84D model and the design matured only with the definitive F - 84G introduced in 1951 . In 1954 , the straight - wing Thunderjet was joined by the swept - wing F - 84F Thunderstreak fighter and RF - 84F Thunderflash photo reconnaissance aircraft . The Thunderjet became the USAF ' s primary strike aircraft during the Korean War , flying 86 , 408 missions and destroying 60 % of all ground targets in the war as well as eight Soviet - built MiG fighters . Over half of the 7 , 524 F - 84s produced served with NATO nations , and it was the first aircraft to fly with the U . S . Air Force Thunderbirds demonstration team . The USAF Strategic Air Command had F - 84 Thunderjets in service from 1948 through 1957 . The F - 84 was the first production fighter aircraft to utilize in - flight refueling and the first fighter capable of carrying a nuclear weapon , the Mark 7 nuclear bomb . Modified F - 84s were used in several unusual projects , including the FICON and Tom - Tom dockings to the B - 29 Superfortress and B - 36 bomber motherships , and the experimental XF - 84H Thunderscreech supersonic turboprop . The F - 84 nomenclature can be somewhat confusing . The straight - wing F - 84A to F - 84E and F - 84G models are called the Thunderjet . The F - 84F Thunderstreak and RF - 84F Thunderflash are a different airplane with swept wings . The XF - 84H Thunderscreech ( not its official name ) was an experimental turboprop version of the F - 84F . The F - 84F swept wing version was intended to be a small variation on the normal Thunderjet with only a few different parts , so it kept the basic F - 84 number . Production delays on the F - 84F resulted in another order of the straight - wing version ; this was the F - 84G . Design and development . In 1944 , Republic Aviation ' s chief designer , Alexander Kartveli , began working on a turbojet - powered replacement for the P - 47 Thunderbolt piston - engined fighter . The initial attempts to redesign the P - 47 to accommodate a jet engine proved futile due to the large cross - section of the early centrifugal compressor turbojets . Instead , Kartveli and his team designed a brand - new aircraft with a streamlined fuselage largely occupied by an axial compressor turbojet engine and fuel stored in rather thick unswept wings . On 11 September 1944 , the USAAF released General Operational Requirements for a day fighter with a top speed of 600 mph ( 521 kn , 966 km / h ) , combat radius of 705 miles ( 612 nmi , 1 , 135 km ) , and armament of either six 0 . 50 in ( 12 . 7 mm ) or four 0 . 60 in ( 15 . 2 mm ) machine guns . In addition , the new aircraft had to use the General Electric TG - 180 axial turbojet which entered production as Allison J35 . On 11 November 1944 , Republic received an order for three prototypes of the new " XP - 84 " — Model AP - 23 . Since the design promised superior performance to the Lockheed - built P - 80 Shooting Star and Republic had extensive experience in building single - seat fighters , no competition was held for the contract . The name " Thunderjet " was chosen to continue the Republic Aviation tradition started with the P - 47 Thunderbolt while emphasizing the new method of propulsion . On 4 January 1945 , even before the aircraft took to the air , the USAAF expanded its order to 25 service test " YP - 84A " s and 75 production " P - 84B " s ( later modified to 15 YP - 84A and 85 P - 84B ) . Meanwhile , wind tunnel testing by the National Advisory Committee for Aeronautics revealed longitudinal instability and stabilizer skin buckling at high speeds . The weight of the aircraft , a great concern given the low thrust of early turbojets , was growing so quickly that the USAAF had to set a gross weight limit of 13 , 400 lb ( 6 , 080 kg ) . The results of this preliminary testing was incorporated into the third prototype , designated " XP - 84A " , which was also fitted with a more powerful J35 - GE - 15 engine with 4 , 000 lbf ( 17 . 8 kN ) of thrust . The first prototype XP - 84 was transferred to Muroc Army Air Field ( present - day Edwards Air Force Base ) where it flew for the first time on 28 February 1946 with Major Wallace A . " Wally " Lien at the controls . It was joined by the second prototype in August ; both aircraft flying with J35 - GE - 7 engines producing 3 , 745 lbf ( 16 . 66 kN ) . The 15 YP - 84As delivered to Patterson Field ( present - day Wright - Patterson Air Force Base ) for service tests differed from XP - 84s by having an upgraded J35 - A - 15 engine , carrying six 0 . 50 in ( 12 . 7 mm ) M2 Browning machine gun s ( four in the nose and one in each wing root ) , and having the provision for wingtip fuel tanks holding 226 U . S . gal ( 856 L ) each . Due to delays with delivery of jet engines and production of the XP - 84A , the Thunderjet had undergone only limited flight testing by the time production P - 84Bs began to roll out of the factory in 1947 . In particular , the impact of wingtip tanks on aircraft handling was not thoroughly studied . This proved problematic later . After the creation of the United States Air Force by the National Security Act of 1947 , the " Pursuit " designation was replaced with " Fighter " , and the P - 84 became the " F - 84 " . F - 84s were assigned to the 27th Fighter Wing , 27th Fighter Escort Wing , 27th Strategic Fighter Wing , 31st Fighter Escort Wing , 127th Fighter Day Wing , 127th Fighter Escort Wing , 127th Strategic Fighter Wing , 407th Strategic Fighter Wing and the 506th Strategic Fighter Wing of the Strategic Air Command from 1947 through 1958 . Operational history . The F - 84B , which differed from YP - 84A only in having faster - firing M3 machine guns , became operational with 14th Fighter Group at Dow Field , Bangor , Maine in December 1947 . Flight restrictions followed immediately , limiting maximum speed to Mach 0 . 8 due to control reversal , and limiting maximum acceleration to 5 . 5 " g " ( 54 m / s² ) due to wrinkling of the fuselage skin . To compound the problem , parts shortages and maintenance difficulties earned the aircraft the nickname , " Mechanic ' s Nightmare " . On 24 May 1948 , the entire F - 84B fleet was grounded due to structural failures . A 1948 review of the entire F - 84 program discovered that none of the F - 84B or F - 84C aircraft could be considered operational or capable of executing any aspect of their intended mission . The program was saved from cancellation because the F - 84D , whose production was well underway , had satisfactorily addressed the major faults . A fly - off against the F - 80 revealed that while the Shooting Star had a shorter takeoff roll , better low altitude climb rate and superior maneuverability , the F - 84 could carry a greater bomb load , was faster , had better high altitude performance and greater range . As a temporizing measure , the USAF in 1949 committed US $ 8 million to implement over 100 upgrades to all F - 84Bs , most notably reinforcing the wings . Despite the resultant improvements , the F - 84B was withdrawn from active duty by 1952 . The " F - 84C " featured a somewhat more reliable J35 - A - 13 engine and had some engineering refinements . Being virtually identical to the F - 84B , the C model suffered from all of the same defects and underwent a similar structural upgrade program in 1949 . All F - 84Cs were withdrawn from active service by 1952 . The structural improvements were factory - implemented in the " F - 84D " , which entered service in 1949 . Wings were covered with thicker aluminum skin , the fuel system was winterized and capable of using JP - 4 fuel , and a more powerful J35 - A - 17 engine with 5 , 000 lbf ( 22 . 2 kN ) was fitted . It was discovered that the untested wingtip fuel tanks contributed to wing structural failures by inducing excessive twisting during high - " g " maneuvers . To correct this , small triangular fins were added to the outside of the tanks . The F - 84D was phased out of USAF service in 1952 and left Air National Guard ( ANG ) service in 1957 . The first effective and fully capable Thunderjet was the " F - 84E " model which entered service in 1949 . The aircraft featured the J35 - A - 17 engine , further wing reinforcement , a 12 in ( 305 mm ) fuselage extension in front of the wings and 3 in ( 76 mm ) extension aft of the wings to enlarge the cockpit and the avionics bay , an A - 1C gunsight with APG - 30 radar , and provision for an additional pair of 230 gal ( 870 L ) fuel tanks to be carried on underwing pylons . The latter increased the combat radius from . One improvement done to the original F - 84 design was rocket racks that folded flush with the wing after the 5 - inch HVAR rockets were fired , which reduced drag over the older fixed mounting racks . This innovation was adopted by other U . S . jet fighter - bombers . Despite the improvements , the in - service rates for the F - 84E remained poor with less than half of the aircraft operational at any given time . This was primarily due to severe shortage of spares for the Allison engines . The expectation was that F - 84Es would fly 25 hours per month , accumulating 100 hours between engine overhauls . The actual flight hours for Korean War and NATO deployments rapidly outpaced the supply and Allison ' s ability to manufacture new engines . The F - 84E was withdrawn from USAF service in 1956 , lingering with ANG units until 1959 . The definitive straight - wing F - 84 was the " F - 84G " which entered service in 1951 . The aircraft introduced a refueling boom receptacle in the left wing , autopilot , Instrument Landing System , J35 - A - 29 engine with 5 , 560 lbf ( 24 . 7 kN ) of thrust , a distinctive framed canopy ( also retrofitted to earlier types ) , and the ability to carry a single Mark 7 nuclear bomb . The F - 84G was retired from USAF in the mid - 1960s . Starting in the early 1960s , the aircraft was deployed by the Portuguese Air Force during the Portuguese Colonial War in Africa . By 1972 , all four operating F - 84 aircraft were supplementing the " Força Aérea " in Angola . Flying the Thunderjet . Typical of most early jets , the Thunderjet ' s takeoff performance left much to be desired . In hot Korean summers with a full combat load , the aircraft routinely required 10 , 000 ft ( 3 , 000 m ) of runway for takeoff even with the help of RATO bottles ( two or four of these were carried , each producing 1 , 000 lbf ( 4 . 4 kN ) of thrust for 14 seconds ) . All but the lead aircraft had their visibility obscured by the thick smoke from the rockets . Early F - 84s had to be pulled off the ground at 160 mph ( 140 kn , 260 km / h ) with the control stick held all the way back . Landings were made at a similar speed , for comparison the North American P - 51 Mustang landed at approximately 120 mph ( 100 kn , 190 km / h ) . Despite the " hot " landing speeds , the Thunderjet was easy to fly on instruments and crosswinds did not present much of a problem . Thanks to the thick straight wing the Thunderjet rapidly reached its Mach 0 . 82 limitation at full throttle and low altitude . The aircraft had sufficient power to fly faster , but exceeding the Mach limit at low altitudes resulted in a violent pitch - up and structural failure causing the wings to break off . Above 15 , 000 ft ( 4 , 600 m ) , the F - 84 could be flown faster but at the expense of severe buffeting . Fortunately , the airspeed was sufficiently easy to control to make safe dive bombing from 10 , 000 ft ( 3 , 000 m ) possible . The top speed limitation proved troublesome against Soviet Mikoyan - Gurevich MiG - 15 s in Korea . Slower than the MiG , the F - 84 was also unable to turn tightly with a maximum instantaneous - turn load of only 3 Gs followed by rapid loss of airspeed . One F - 84E pilot credited with two MiG kills achieved his second victory by intentionally flying his aircraft into pitch - up . The MiGs chasing him were unable to follow the violent maneuver and one crashed into the ground . Luckily for the F - 84E pilot , the aircraft did not disintegrate but the airframe did suffer heavy warping . The F - 84 was a stable gun platform and the computing gunsight aided in accurate gunnery and bombing . Pilots praised the aircraft for Republic ' s legendary ruggedness . Pilots nicknamed the Thunderjet " The Lead Sled " . It was also called " The Iron Crowbar " , " a hole sucking air " , " The Hog " ( " The Groundhog " ) , and " The World ' s Fastest Tricycle " , " Ground Loving Whore " as a testament to its long takeoff rolls . F - 84 lore stated that all aircraft were equipped with a " sniffer " device that , upon passing " V " , would look for the dirt at the end of the runway . As soon as the device could smell the dirt , the controls would turn on and let the pilot fly off the ground . In the same vein , it was suggested a bag of dirt should be carried in the front landing gear well . Upon reaching " V " , the pilot would dump the dirt under the wheels , fooling the sniffer device . Korean War . The Thunderjet had a distinguished record during the Korean War . Although the F - 84B and F - 84C could not be deployed because their J35 engines had a service life of only 40 hours , the F - 84D and F - 84E entered combat with 27th Fighter Escort Group on 7 December 1950 . The aircraft were initially tasked with escorting the B - 29 Superfortress bombers . The first Thunderjet air - to - air victory was scored on 21 January 1951 at the cost of two F - 84s . The F - 84 was a generation behind the swept - wing Soviet Mikoyan - Gurevich MiG - 15 and outmatched , especially when the MiGs were flown by more - experienced pilots , and the MiG counter - air mission was soon given to the F - 86 Sabre . Like its famous predecessor , the P - 47 , the F - 84 switched to the low - level interdiction role at which it excelled . The F - 84 flew a total of 86 , 408 missions , dropping 55 , 586 tons ( 50 , 427 metric tons ) of bombs and 6 , 129 tons ( 5 , 560 metric tons ) of napalm . The USAF claimed F - 84s were responsible for 60 % of all ground targets destroyed in the war . Notable F - 84 operations included the 1952 attack on the Sui - ho Dam . During the war , the F - 84 became the first USAF fighter to utilize aerial refueling . In aerial combat , F - 84 pilots were credited with eight MiG - 15 kills against a Soviet - claimed loss of 64 aircraft . The total losses were 335 F - 84D , E and G models . Notable achievements . By the mid - 1960s , the F - 84 / F - 84F was replaced by the F - 100 Super Sabre and the RF - 84F by the RF - 101 Voodoo in USAF units , being relegated to duty in the Air National Guard . The last F - 84F Thunderflash retired from the ANG in 1971 . Three Hellenic Air Force RF - 84Fs that were retired in 1991 were the last operational F - 84s . Costs . Notes : " The costs are in approximately 1950 United States dollars and have not been adjusted for inflation . "