Republic F-84F Thunderstreak
|USAF F-84F Thunderstreak|
|First flight||June 3, 1950|
|Introduction||May 12, 1954|
|Retired||1972 (US ANG)
|Primary users||United States Air Force
Belgian Air Force
Greek Air Force
Turkish Air Force
|Unit cost||US$769,330 (F-84F)|
|Developed from||Republic F-84 Thunderjet|
|Variants||Republic XF-84H Thunderscreech|
The Republic F-84F Thunderstreak was an American-built swept-wing turbojet fighter-bomber. While an evolutionary development of the straight-wing F-84 Thunderjet, the F-84F was a new design. The RF-84F Thunderflash was a photo reconnaissance version.
Design and development 
In 1949, Republic created a swept wing version of the F-84 hoping to bring performance to the F-86 level. The last production F-84E was fitted with a swept tail, a new wing with 38.5 degrees of leading edge sweep and 3.5 degrees of anhedral, and a J35-A-25 engine producing 5,300 pound-force (23.58 kN) of thrust. The aircraft was designated XF-96A. It flew on 3 June 1950 with Otto P. Haas at the controls. Although the airplane was capable of 602 knots (693 mph, 1,115 km/h), the performance gain over the F-84E was considered minor. Nonetheless, it was ordered into production in July 1950 as the F-84F Thunderstreak. The F-84 designation was retained because the fighter was expected to be a low-cost improvement of the straight-wing Thunderjet with over 55 percent commonality in tooling.
In the meantime, the USAF, hoping for improved high-altitude performance from a more powerful engine, arranged for the British Armstrong Siddeley Sapphire turbojet engine to be built in the United States as the Wright J65. To accommodate the larger engine, YF-84Fs with a British-built Sapphire as well as production F-84Fs with the J65 had a vertically stretched fuselage, with the air intake attaining an oval cross-section. Production delays with the F-84F forced USAF to order a number of straight-wing F-84Gs as an interim measure.
Production quickly ran into problems. Although tooling commonality with the Thunderjet was supposed to be 55 percent, in reality only 15 percent of tools could be reused. To make matters worse, the F-84F utilized press-forged wing spars and ribs. At the time, only three presses in the United States could manufacture these, and priority was given to the Boeing B-47 Stratojet bomber over the F-84. The YJ65-W-1 engine was considered obsolete and the improved J65-W-3 did not become available until 1954. When the first production F-84F finally flew on 22 November 1952, it differed from the service test aircraft. It had a different canopy which opened up and back instead of sliding to the rear, as well as airbrakes on the sides of the fuselage instead of the bottom of the aircraft. The aircraft was considered not ready for operational deployment due to control and stability problems. The first 275 aircraft, equipped with a conventional stabilizer-elevator tailplane, suffered from accelerated stall pitch-up and poor turning ability at combat speeds. Beginning with Block 25, the problem was ameliorated by introduction of a hydraulically-powered one-piece stabilator. A number of aircraft were also retrofitted with spoilers for improved high-speed control. As a result, the F-84F was not declared operational until 12 May 1954.
Operational history 
Project Run In completed operational tests in November 1954 and found the aircraft to be to USAF satisfaction and considerably better than the F-84G. However, ongoing engine failures resulted in the entire fleet being grounded in early 1955. Also, the J65 engine continued to suffer from flameouts when flying through heavy rain or snow. As the result of the problems, the active duty phaseout began almost as soon as the F-84F entered service in 1954, and was completed by 1958. Increased tensions in Germany associated with construction of the Berlin Wall in 1961 resulted in reactivation of the F-84F fleet. In 1962, the fleet was grounded due to corrosion of control rods. A total of 1,800 man hours was expended to bring each aircraft to full operational capacity. The aircraft were retired from active service in 1964. Stress corrosion forced retirement of ANG F-84Fs in 1971.
In what is probably one of the very few air-to-air engagements involving the F-84F, two Turkish Air Force F-84F Thunderstreaks shot down two Iraqi Il-28 Beagle bombers that crossed the Turkish border by mistake during a bombing operation against Iraqi Kurdish insurgents. This engagement took place on 16 August 1962.
The second YF-84F prototype was completed with wing-root air intakes. These were not adopted for the fighter due to loss of thrust. However, this arrangement permitted placement of cameras in the nose and the design was adopted for the RF-84F Thunderflash reconnaissance version. The first YRF-84F was completed in February 1952. The aircraft retained an armament of four machine guns and could carry up to fifteen cameras. Innovations included computerized controls which adjusted camera settings for light, speed, and altitude, a periscope to give the pilot better visualization of the target, and a voice recorder to let the pilot narrate his observations. Being largely identical to the F-84F, the Thunderflash suffered from the same production delays and engine problems, delaying operational service until March 1954. The aircraft was retired from active duty in 1957, only to be reactivated in 1961, and finally retired from the ANG in 1972.
Several modified Thunderflashes were used in the FICON project.
Flying the Thunderstreak 
The Thunderstreak suffered from the same poor takeoff performance as the straight-wing Thunderjets despite having a more powerful engine. In reality, almost 700 pounds-force (3.11 kN) or 10 percent of total thrust was lost because the J65 was installed at an angle and its exhaust had a prominent kink. On a hot day, 7,500 feet (2,285 m) of runway were required for takeoff roll. A typical takeoff speed was 160 knots (185 mph, 300 km/h). Like the Thunderjet, the Thunderstreak excelled at cruise and had predictable handling characteristics within its performance envelope. Like its predecessor, it also suffered from accelerated stall pitch-up and potential resulting separation of wings from the airplane. In addition, spins in the F-84F were practically unrecoverable and ejection was the only recourse below 10,000 feet (3,000 m).
With the appearance of Republic's F-105 Thunderchief, which also used wing-root mounted air intakes, the Thunderstreak became known as the Thud's Mother. The earlier F-84A had been nicknamed the "Hog" and the F-84F "Super Hog," the F-105 becoming the "Ultra Hog."
March 9, 1955: Lt. Col. Robert R. Scott, in a F-84F Thunderstreak, set a three hour, 44-minute and 53-second record for the 2,446 mile flight from Los Angeles to New York."Week In History". U.S. Air Force. Retrieved 4 March 2013.
By the mid-1960s, the F-84F was replaced by the North American 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.
Richard Bach, who later wrote the bestseller Jonathan Livingston Seagull, was an ANG F-84F pilot who was once activated for duty in Europe. His first book, Stranger to the Ground, described in detail what it was like to fly the Thunderstreak in the course of an operational flight at night from England to France in adverse weather.
Variants and production blocks 
- Two swept-wing prototypes of the F-84F, initially designated YF-96.
- F-84F Thunderstreak
- Swept wing version with Wright J65 engine. Tactical Air Command aircraft were equipped with Low-Altitude Bombing System (LABS) for delivering nuclear bombs. 2,711 built, 1,301 went to NATO under Mutual Defense Assistance Program (MDAP).
- 25 RF-84Fs were converted to be carried, and launched from the bomb bay of a GRB-36F bomber as part of the FICON project. The aircraft were later redesignated RF-84K.
- RF-84F Thunderflash
- Reconnaissance version of the F-84F, 715 built.
- Two F-84Fs were converted into experimental aircraft. Each was fitted with an Allison XT40-A-1 turboprop engine of 5,850 shaft horsepower (4,365 kW) driving a supersonic propeller. Ground crews dubbed the XF-84H the Thunderscreech due to its extreme noise output.
- Two F-84Fs were converted into YF-84J prototypes with enlarged nose intakes and a deepened fuselages for the General Electric J73 engine; the YF-84J reached Mach 1.09 in level flight on 7 April 1954. The project was cancelled due to the excessive cost of converting extant F-84Fs.
Serial number Quantity produced type and block
- 49-2430 1 YF-84F-RE
- 51-1344/1345 2 YF-84F-RE
- 51-1346/1355 10 F-84F-1-RE
- 51-1356/1380 25 F-84F-5-RE
- 51-1381/1430 50 F-84F-10-RE
- 51-1431/1510 80 F-84F-15-RE
- 51-1511/1620 110 F-84F-20-RE
- 51-1621/1760 140 F-84F-25-RE (A)
- 51-1761/1827 67 F-84F-30-RE (B)
- 51-9311/9320 10 F-84F-1-GK
- 51-9321/9335 15 F-84F-5-GK
- 51-9336/9356 21 F-84F-10-GK
- 51-9357/9409 53 F-84F-25-GK (A)
- 51-9410/9454 45 F-84F-30-GK (B)
- 51-9455/9503 49 F-84F-35-GK (C)
- 51-9504/9547 44 F-84F-40-GK (D)
- 51-17061/17088 28 F-84F-35-RE (C)
- 52-6355/6422 68 F-84F-30-RE (B)
- 52-6423/6522 100 F-84F-35-RE (C)
- 52-6523/6642 120 F-84F-40-RE (D)
- 52-6643/6812 170 F-84F-45-RE (E)
- 52-6813/6907 95 F-84F-50-RE (F)
- 52-6908/7007 100 F-84F-55-RE (G)
- 52-7008/7017 10 F-84F-56-RE (G)
- 52-7018/7049 32 F-84F-35-RE (C)
- 52-7050/7089 40 F-84F-40-RE (D)
- 52-7090/7114 25 F-84F-45-RE (E)
- 52-7115/7126 12 F-84F-46-RE (E)
- 52-7127/7191 65 F-84F-51-RE (F)
- 52-7192/7228 37 F-84F-56-RE (G)
- 52-8767/8834 68 F-84F-41-GK (D)
- 52-8835/8982 148 F-84F-46-GK (E)
- 52-8983/9128 146 F-84F-51-GK (F)
- 52-10510/10538 29 F-84F-56-RE (G)
- 53-6532/6715 184 F-84F-61-RE (H)
- 53-6716/6835 120 F-84F-66-RE (J)
- 53-6836/6955 120 F-84F-71-RE (K)
- 53-6956/7075 120 F-84F-76-RE (K)
- 53-7076/7230 155 F-84F-81-RE (K)
- 51-1828 1 YRF-84F-RE
- 51-1829/1958 130 RF-84F-1-RE
- 51-11250/11297 48 RF-84F-RE
- 51-16996/17058 63 RF-84F-RE
- 52-7229/7475 247 RF-84F-RE
- 52-7254/7278 25 RF-84K-RE
- 52-8717/8766 50 RF-84F-30-RE
- 53-7521/7697 177 RF-84F-RE
- 57-6552/6716 165 RF-84F-RE
- Belgian Air Force (197 x F-84F, 34 x RF-84F operated from 1955)
- Royal Danish Air Force (23× RF-84F 1957-1971)
- Luftwaffe (450× F-84F, 108× RF-84F 1956-1967)
- Royal Netherlands Air Force (143× F-84F, 24× RF-84F 1955-1970)
- Royal Norwegian Air Force (35× RF-84F 1956-1970)
- United States Air Force (1496× F-84F, 388× RF-84F 1952-1972)
Aircraft on display 
- 51-17045 - Flyhistorisk Museum, Sola, Stavanger Airport, Sola, near Stavanger
- 51-17053 - Norwegian Armed Forces Aircraft Collection, Gardermoen.
United Kingdom 
United States 
- RF-84F Thunderflash
Specifications (F-84F) 
- Crew: 1
- Length: 43 ft 4¾ in (13.23 m)
- Wingspan: 33 ft 7¼ in (10.25 m)
- Height: 14 ft 4¾ in (4.39 m)
- Wing area: 325 ft² (30 m²)
- Empty weight: 13,830lb (5,200 kg)
- Loaded weight: lb (kg)
- Max. takeoff weight: 28,000 lb (12,701 kg)
- Powerplant: 1 × Wright J65-W-3 turbojet, 7,220 lbf (32.2 kN)
- Maximum speed: 695 mph (604 knots, 1,119 km/h) at sea level
- Range: 810 mi (704 nmi, 1,304 km) combat radius with two droptanks
- Service ceiling: 46,000 ft (14,000 m)
- Rate of climb: 8,200 ft/min (42 m/s)
- Wing loading: 86 lb/ft² (423 kg/m²)
- 6× .50 in (12.7 mm) Browning M3 machine guns,
- Up to 6,000lb (2,727 kg) of rockets and bombs, including one Mark 7 nuclear bomb
- A-1CM or A-4 gunsight with APG-30 or MK-18 ranging radar
- AN/ARC-33 or 34 command set radio
- AN/APX-6 or 6A IFF set
- AN/AR-6 radio compass
- AN/APW-11 or 11A radar set
- AN/APN-21 TACAN set
Accidents and incidents 
- On 4 April 1957 the USAF Captain Richard W. Higgins died after a low ejection with one of the first F-84F of the German Air Force near the Fürstenfeldbruck Air Base.
- In June 1957 Bud Day survived a "no chute" ejection from an F-84 in Britain following an engine fire.
- On 29 August 1961, a French Air Force F-84F clipped the cable of an aerial tramway at Mont Blanc, killing six people and leaving 81 more stranded. The pilot was on a reconnaissance mission and was unaware of the accident until after he had landed.
- On 14 September 1961, two West German F-84F of the Luftwaffe crossed into East German airspace due to a navigational error, eventually landing at Berlin Tegel Airport, evading a large number of Soviet fighter aircraft. The event came at a historically difficult time during the Cold War, one month after the construction of the Berlin Wall.
See also 
- Related development
- Republic F-84 Thunderjet
- Republic XF-84H Thunderscreech
- RF-84K FICON
- Republic XF-91 Thunderceptor
- Republic F-105 Thunderchief
- Aircraft of comparable role, configuration and era
- Knaack 1978, p. 42.
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