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59-585: The design was originally intended to be a relatively simple upgrade to the F-84 Thunderjet to make it more competitive with the F-86 Sabre , differing largely in the use of a swept-wing and tail. Given the small number of changes, it was assigned the next model letter in the F-84 series, F. The prototypes demonstrated a number of performance and handling issues, which resulted in marginal improvement over

118-553: A brief period using ex-French examples, the Israeli Air Force . In 1948, a swept wing version of the F-84 was created with the hope of bringing performance to the level of the F-86 . 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

177-408: A different canopy which opened up and back instead of sliding to the rear (a unique design, the canopy was mounted on a pair of hydraulic rams and a pivoted lever arm that allowed it to lift up and backwards while remaining almost level with the fuselage, instead of the more common simple hinged canopy), as well as airbrakes on the sides of the fuselage instead of the bottom of the aircraft. The aircraft

236-540: A front-line design was brief; it began to be moved to secondary roles as early as 1958. F-84Fs were then offered to NATO member countries and other allies, who took them up in large numbers. Operators included the Belgian Air Force , Royal Danish Air Force , French Air Force , West German Air Force , Hellenic Air Force , Italian Air Force , Royal Netherlands Air Force , Royal Norwegian Air Force , Republic of China Air Force , Turkish Air Force , and for

295-615: A longer runway. On approach, at a high angle of attack, the fighter exceeded its flight envelope, and, too far into stall condition, lost directional control with fatal results. These scenes were inserted in the movie The Hunters , starring Robert Mitchum and Robert Wagner , in the movie X-15 with actor Charles Bronson playing the pilot, and in the made for TV film Red Flag: The Ultimate Game , although in The Hunters and in Red Flag: The Ultimate Game ,

354-441: A move to more highly tapered designs as well. Although it had long been known that an elliptical planform is "perfect" from an induced drag standpoint, it was also noticed that a linear taper of the wing had much the same effect, while being lighter. Research during the war led to widespread use of taper, especially in the post-war era. However, it had been noticed early on that such designs had unfavourable stall characteristics; as

413-514: 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

472-727: A result, the F-84F was not declared operational until 12 May 1954. 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,

531-471: A similar solution was attempted on the Boeing B-47 Stratojet where it proved considerably more effective. This may have been helped by the presence of the podded engines , whose vertical mountings acted as barriers to span wise flow. More common solutions to the problem of spanwise flow is the use of a wing fence or the related dogtooth notch on the leading edge of the wing. This disrupts

590-415: Is a vector addition of all of the weight terms of the parts of the aircraft, including the wing. This too can be reduced to a single weight term acting at some point along the longitudinal axis of the aircraft, the " center of gravity ", or CoG. If the wing is positioned so its CoP lies near CoG for the aircraft, in level flight the wing will lift the aircraft straight up. This reduces any net forces pitching

649-474: Is an uncommanded nose-upwards rotation of an aircraft. It is an undesirable characteristic that has been observed mostly in experimental swept-wing aircraft at high subsonic Mach numbers or high angle of attack. Pitch-up problems were first noticed on high-speed test aircraft with swept wings. It was a common problem on the Douglas Skyrocket , which was used extensively to test the problem. Before

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708-627: Is further forward. This causes further nose-up force, increasing the angle of attack and causing more of the tip area to stall. This may lead to a chain reaction that causes violent nose-up pitching of the aircraft. This effect first noticed in the Douglas D-558-2 Skyrocket in August 1949, when a 0.6 G turn suddenly increased out of control to 6 G. This was not entirely surprising; the effect had been seen earlier in wind tunnel simulations. These effects can be seen at any speed; in

767-673: Is on static display at the Midland Air Museum , Coventry Airport , Warwickshire . Very few Armstrong Siddeley Sapphire engines exist, other known examples are preserved at the Jet Age Museum in Gloucester, England, and the Malta Aviation Museum at Ta' Qali . Data from Jane's. Related development Comparable engines Related lists Pitch-up In aerodynamics , pitch-up

826-503: Is part of the overall wing design and normally controlled via the existing high-lift devices . The first known attempt to address these problems took place on the platform where they were first noticed, the Douglas Skyrocket. This took the form of a series of vortex generators added to the outboard portions of the wing, breaking up the boundary layer. However, this was found to have almost no effect in practice. Nevertheless,

885-435: Is possible for a pitch-up event to cause the turbulent air behind the wing to flow across the horizontal stabilizer, making it difficult or impossible to apply nose-down pressure to counteract the pitch-up. Aircraft with low-mounted tail surfaces did not suffer from this effect, and in fact improved their control authority as the wing's wake cleared the controls surfaces, flowing above it. This was not always enough to correct for

944-470: Is replaced by an equivalent pair of forces called lift and drag. The longitudinal position at which these forces act and the magnitude of the forces change with angle of attack . In addition a varying pitching moment exists for any force location other than the CoP. These changes lead to a requirement to trim aircraft as they change their speed or power settings. Another major consideration for aircraft design

1003-530: Is to use a control-canard . Another modern solution to pitch-up is the use of slats. When slats are extended they increase wing camber and increase maximum lift coefficient . Pitch-up is also possible in aircraft with forward-swept wings as used on the Grumman X-29 . With forward-swept wings the span wise flow is inboard, causing the wing root to stall before the wingtip. Although at first glance it would appear that this would cause pitch- down problems,

1062-601: The Air National Guard . The last RF-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. Data from Fighters of the United States Air Force, Combat Aircraft since 1945 General characteristics Performance Armament Avionics Communications Equipment Richard Bach , who later wrote

1121-657: The Avon RA.3 had a design thrust of 6,500 lbf (29,000 N) at that time. A number of companies expressed interest in the Sapphire, and it was considered as either the main or backup powerplant for most British designs of the late '40s and early '50s. The ASSa.5 with 7,500 lbf (33,000 N) thrust was used only on the English Electric P.1A , prototype for the Lightning. A simple fixed-nozzle reheat

1180-664: The Metrovick F.2 in 1940, evolving into an advanced axial flow design with an annular combustion chamber that developed over 11,000 lbf (49 kN). It powered early versions of the Hawker Hunter and Handley Page Victor , and every Gloster Javelin . Production was also started under licence in the United States by Wright Aeronautical as the J65 , powering a number of US designs. The Sapphire's primary competitor

1239-575: The Wright J65 at the entry to the compressor to prevent the stalling and blade excitation. Armstrong-Siddeley tested a similar solution on the Sapphire but incorporated blade changes instead to reduce the blade response to the stalling. Caygill states that one of the most serious problems encountered throughout the life of the Gloster Javelin was caused by "centre-line closure" on the Sapphire engine. Flying through thick cloud could cause

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1298-495: The ailerons . An unusual solution tried on the XF-91 Thunderceptor prototype fighter was to give the wingtips a wider chord than the wing roots. The idea was to increase wingtip efficiency and cause the wing roots to stall first. Angle of attack sensors on the aircraft can also detect when the angle of attack approaches the attitude known to result in pitch-up and activate devices like the stick shaker to warn

1357-406: The boundary layer , causing some of the airflow to move "sideways" along the wing. This occurs all along the wing, but as one moves towards the tip the sideways flow increases, as it includes both the contribution of the wing at that point, as well as span wise flow from points closer to the root. This effect takes time to build up, at higher speeds the span wise flow tends to be blown off the back of

1416-521: The ANG in 1972. Several modified Thunderflashes were used in the FICON project . The Thunderstreak suffered from the same poor takeoff performance as the straight-wing Thunderjet despite having a more powerful engine. In reality, almost 700 pounds-force (3.11 kN) or ten percent of total thrust was lost because the J65 was installed at an angle and its jet pipe was not perfectly straight (in addition to

1475-492: 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

1534-711: 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 F-84F was retired from active service with the USAF in 1964, and replaced by the North American F-100 Super Sabre . The RF-84F was replaced by the RF-101 Voodoo in USAF units, and relegated to duty in

1593-519: 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

1652-476: The J65 had a vertically stretched fuselage, with the air intake attaining an oval cross-section. Production delays with the F-84F forced the 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 fifteen percent of tools could be reused. To make matters worse,

1711-584: The Skyrocket they occurred primarily in the transonic (the Weil-Gray criteria) but with more highly swept and tapered planforms, like on the North American F-100 Super Sabre , the effect was common at low speeds as well (the Furlong-McHugh boundary), when the aircraft flew at higher angles of attack in order to maintain lift at low speeds. In addition, swept wings tend to generate span wise flow of

1770-491: The Soviet fighters were available during the ongoing Cold War for filming. They were painted a flat gray with red star insignia. Related development Aircraft of comparable role, configuration, and era Armstrong Siddeley Sapphire The Armstrong Siddeley Sapphire is a British turbojet engine that was produced by Armstrong Siddeley in the 1950s. It was the ultimate development of work that had started as

1829-575: The air intake to be modified. With these and other changes, the design was finally ready to enter production, but only a fraction of the original production systems could be used and the aircraft was effectively a new design. It finally entered service in November 1954, by which time the Sabre had also undergone many upgrades and the Thunderstreak was relegated to the fighter-bomber role. Its time as

Republic F-84F Thunderstreak - Misplaced Pages Continue

1888-403: The aircraft up or down, but for a number of reasons the two points are normally slightly separated and a small amount of force from the flight control surfaces is used to balance this out. The same basic layout is desirable for an aircraft with a swept wing as well. On a conventional rectangular wing, the CoP meets the aircraft at the point on the chord running directly out from the root. While

1947-454: 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). 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,

2006-637: The appearance of the Republic F-105 Thunderchief , which used wing-root mounted air intakes of a similar design to those fitted on the RF-84F, the photorecon variant Thunderflash 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". In what is probably one of the very few air-to-air engagements involving

2065-562: 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. F-84Fs were also used to represent North Korean MiG-15 fighters in the 1958 film version of James Salters' novel "The Hunters", because none of

2124-504: The compressor case to shrink and rub the blades causing catastrophic engine failures and loss of the aircraft. "Centre-line closure" also caused a Sapphire failure on a Victor B.1. An afterburner with limited boost was required for the Javelin's ASSa.7, making it the ASSa.7LR . 12% boost was required at high altitudes to regain the bomber intercept performance that had been lost carrying

2183-401: The corrosion of control rods. A total of 1,800 man hours were expended to bring each aircraft to full operational capacity. Stress corrosion eventually forced the retirement of ANG F-84Fs in 1971. On 9 March 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 miles (3,936 km) flight from Los Angeles to New York. With

2242-428: The extreme rear mounting of the wing means that when the root stalls the lift moves forward, towards the tips. When a swept wing starts to stall, the outermost portions tend to stall first. Since these portions are behind the center of pressure , the overall lift force moves forward, pitching the nose of the aircraft upwards. This leads to a higher angle of attack and causes more of the wing to stall, which exacerbates

2301-425: The first place). Deployment of the braking parachute and a considerable height above the ground were essential for a chance at recovery. Wings generate pressure distributions on their upper and lower surfaces which produce a single force acting at a point known as the " center of pressure ", or CoP, which is normally located between ⅓ and ½ of the way back from the leading edge . This upward and rearward leaning force

2360-403: The flow and re-directs it rearward, while also causing the buildup of stagnant air inboard to lower the stall point. This does have an effect on overall airflow on the wing, and is generally not used where the sweep is mild. To address the problems with spanwise loading, a wider variety of techniques have been used, including dedicated slats or flaps, the use of washout or automated control of

2419-453: The new de Havilland Firestreak missiles. Afterburners with a low boost requirement were sometimes known as "wee-heat". Other low-boost reheats have included the "tailpipe augmentation"(TPA) on the F-86H (J73) with +10% at take-off and "Bristol Simplified Reheat"(BSR), with about 16% boost at take-off, tested on Derwent V, Orenda, Olympus and Orpheus engines. An Armstrong Siddeley Sapphire

Republic F-84F Thunderstreak - Misplaced Pages Continue

2478-740: The only project to select it, the Saunders-Roe SR.A/1 , was cancelled. The Ministry of Supply (MoS) designated the F.9 as the MVSa.1 . In 1948 Metrovick exited the jet engine industry. Armstrong Siddeley, who already had a turbine development of their own, the ASX , took over the MVSa.1, now renamed ASSa.1 . After a redesign it emerged as the ASSa.2 . In December 1949 the ASSa.2 completed an acceptance test at 7,380 lbf (32,800 N). Its competitor,

2537-420: The pilot, and the stick pusher which overpowers the pilot and forces the nose of the aircraft down to a safer angle of attack. Twist or washout built into the wingtips can also alleviate pitch-up. In effect, the angle of attack at the wingtip becomes smaller than elsewhere on the wing, meaning that the inboard portions of the wing will stall first. A commonly used solution to pitch-up in modern combat aircraft

2596-606: The pitch-up phenomenon was well understood, it plagued all early swept-wing aircraft. In the F-100 Super Sabre it even got its own name, the Sabre dance. In aircraft with high-mounted tailplanes, like the F-101 Voodoo , recovery was especially difficult because the tailplane was placed directly in the wing wake during the pitch-up, causing deep stall (although the T-tail was meant to prevent pitch-up from starting in

2655-417: The previous versions. Production was repeatedly delayed and another run of the straight-wing Thunderjets were completed as the G models. Looking for a clear performance edge compared to the G models, the engine was upgraded to the much more powerful British Armstrong Siddeley Sapphire built in the United States as the Wright J65 . The larger engine required the fuselage to be stretched into an oval shape and

2714-464: The problem, however; the F-86 continued to suffer from pitch-up in spite of increasing nose-down pressure from the tail surfaces. As the primary causes of the pitch-up problem are due to spanwise flow and more loading at the tips, measures to address these issues can eliminate the problem. In early designs these were typically "add-ons" to an otherwise conventional wing planform, but in modern designs this

2773-548: The problem. The pilot often loses control, with fatal results at low altitude because there was insufficient time for the pilot to regain control or eject before hitting the ground. A large number of aircraft were lost to this phenomenon during landing, which left aircraft tumbling onto the runway, often in flames. One of the most notorious incidents was the loss of F-100C-20-NA Super Sabre 54-1907 and its pilot during an attempted emergency landing at Edwards AFB , California on January 10, 1956. By chance, this particular incident

2832-477: The same analysis will reveal a center of pressure point for a swept wing, its location may be considerably behind the leading edge measured at the root of the wing . For highly swept planforms, the CoP may lie behind the trailing edge of the wing root, requiring the wing to meet the aircraft at a seemingly far-forward location. In this case of a swept wing, changes to the CoP with angle of attack may be magnified. The introduction of swept wings took place during

2891-507: 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-84F s with a British-built Sapphire as well as production F-84Fs with

2950-434: The tips were more highly loaded in high angles of attack, they operated closer to their stall point. Although this effect was unfavourable in a conventional straight wing aircraft, on a swept-wing design it had unexpected and dangerous results. When the tips stall on a swept wing, the center of pressure, the average lift point for the wing as a whole, moves forward. This is because the section still generating considerable lift

3009-465: The usual thrust losses from the long jet pipe). 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

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3068-406: The wing before it has time to become serious. At lower speeds, however, this can lead to a considerable buildup of the boundary layer at the wing tip, adding to the problems noted above. Finally, while not directly related to the effects above, it was common during the early jet age to use T-tail designs in order to keep the aerodynamic surfaces well clear of the jet engine area. In this case it

3127-449: Was allowed to decay too much. The brand new F-100C was flown by Lt. Barty R. Brooks, a native of Martha, Oklahoma and a Texas A&M graduate, of the 1708th Ferrying Wing, Detachment 12, Kelly AFB , Texas . The aircraft was one of three being delivered from North American's Palmdale plant to George AFB , California, but the nose gear pivot pin worked loose, allowing the wheel to swivel at random, so he diverted to Edwards, which had

3186-480: Was considered not ready for operational deployment due to control and stability problems. The first 275 aircraft, equipped with conventional stabilizer-elevator tailplanes, suffered from accelerated stall pitch-up and poor turning ability at combat speeds. Beginning with Block 25, the problem was improved upon by the introduction of a hydraulically powered one-piece stabilator . A number of aircraft were also retrofitted with spoilers for improved high-speed control. As

3245-585: Was designated XF-96A . It flew on 3 June 1950 with Oscar 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

3304-537: Was fitted to extend the performance boundary for stability and control testing from about Mach 1.1 to beyond Mach 1.5. Future versions of the Lightning were powered by the Avon. The ASSa.6 , 8,300 lbf (37,000 N), was used on the Gloster Javelin FAW Mk.1 , Hawker Hunter F.Mk.2 and F.Mk.5, and the prototype Sud Ouest SO 4050 Vautour . The higher thrust ASSa.7 at 11,000 lbf (49 kN)

3363-488: Was recorded in detail on 16 mm film by cameras set up to cover an unrelated test. The pilot fought desperately to regain control due to faulty landing technique, finally rolling and yawing to the right before striking the ground with the fuselage turned approximately 90 degrees to the line of flight. Anderson, 1993 states the F-100 was noticeably underpowered for its day and had very pronounced "backside" tendencies if airspeed

3422-633: Was the Rolls-Royce Avon . Design evolution of the Sapphire started at Metropolitan-Vickers (Metrovick) in 1943 as an offshoot of the F.2 project. With the F.2 reaching flight quality at about 1,600 lbf (7,100 N), Metrovick turned to producing larger designs, both an enlarged F.2 known as the Beryl , as well as the much larger F.9 Sapphire . (The names were chosen after a decision to use gemstones for future engine names). The Beryl eventually developed 4,000 lbf (18 kN) thrust, but

3481-605: Was the first British engine to be rated above 10,000 lbf (44 kN) and it powered the Gloster Javelin FAW Mk.7 , Handley Page Victor B.Mk.1 and a prototype Swiss fighter-bomber, the FFA P-16 . The Sapphire compressor operated well, free from surging, over its complete RPM range without the need for variable inlet guide vanes (VIGV) or bleed. However, early compressor stages suffered from fatigue due to rotating stall at low RPM and various fixes, such as lacing wire, were incorporated. Curtiss-Wright introduced variable ramps on

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