History of F-35 Lightning II Fighter Development
History of F-35 Lightning II Fighter Development - The F-35 Joint Strike Fighter, developed jointly by the United States and eight partner nations, combines the stealth of the F-117 Nighthawk, the supersonic speed of the F-16 Fighting Falcon, the ship-based operations of the F-18 Hornet, the AV-8B Harrier ( All three prototypes are now in the final stages of System Development and Demonstration (SDD).
History of F-35 Lightning II Fighter Development
alienmilitary - The F-35A is typical of the F-35A, but the F-35B is also typical of the US Navy. The F-35B has a shorter cockpit, with a lift fan between the cockpit rear air inlet ducts, driven by the engine via a drive shaft; the F-35C has a larger wing to reduce the weight of the wing on the aircraft carrier. The Tactical Fighter Experimental (TFX) program was a failure in the 1960s, and the need for a common fighter mission was initially questioned as to whether it could be accommodated in a common fighter aircraft.
With the failure of the Tactical Fighter Experimental (TFX) program in the 1960s, it was initially questionable whether the mission requirements of the different services could be accommodated in a common fighter. The Tactical Fighter Experimental program was originally conceived as a common airframe and engine to meet the air defense needs of the Navy's fleet and the Air Force's long-range tactical bomber needs, saving billions of dollars in development costs. -111.
The development of a supersonic vertical take-off and landing fighter was a major challenge, as the VAK 191 and the XFV-12A technology demonstrator were not capable of supersonic flight and never entered service. The reason was that only a large engine could provide the hovering thrust needed, and a large amount of fuel had to be carried on board, making it impossible to design a slim supersonic aircraft.
The development of the vertical take-off and landing aircraft
The first vertical take-off and landing fighters were the Lockheed XFV-1, the Convair XFY-1, and the Ryan X-13 in the 1950s. It was thought that, with a little more thrust, the tail-sitter would be able to take off and land vertically with the nose up and the tail down. However, the XFY-1's test flights showed that the aircraft had very poor handling and it was not easy to change from a vertical to a horizontal flight attitude.
The second generation of vertical take-off and landing fighters, such as the French Mirage IIIV of the 1960s, had eight vertical engines for landing in addition to the traditional tail engine, so that the plane could still take off in the traditional horizontal attitude and the pilot could judge the rate of descent by looking at the ground. However, the additional eight engines took up too much space on the fuselage and were useless when the plane was cruising; when the plane was taking off and landing, the engines were not only useless, but also became excess weight on the plane. In addition, the exhaust gases from the vertical engine would not only cause corrosion of the fuselage, but if they got into the intake ducts of the vertical engine, they would also cause the engine to stall and lose thrust, posing a major threat to the safety of the aircraft's landing.
The VJ-101 is similar in appearance to the F-104, with six engines, two side-by-side in the rear of the cockpit, dedicated to generating vertical lift, and a rotating engine pod with two engines in each wingtip. The engine pods are oriented vertically for vertical takeoff and landing, providing vertical thrust with the two engines behind the cockpit, and rotate horizontally for cruise flight, providing horizontal thrust. However, it is very difficult to change from a cruise attitude to a vertical take-off and landing attitude, and vice versa, and the engines required for vertical take-off and landing are large in size and thrust, which naturally results in high aerodynamic drag and unsatisfactory range and payload.
The VAK 191 used two lift engines, one behind the cockpit and one behind the wing trailing edge, with one deflector engine in the middle of the two lift engines to provide vertical and horizontal take-off and landing. Directional thrust; the propulsion and lift of the Yak-38 and Yak-141 are very similar, both have two lift engines installed at the rear of the cockpit, the main engine nozzle at the tail is rotatable. Forward thrust. This type of lift engine takes up too much fuselage space and also produces hot exhaust gases that flow back into the fuselage causing corrosion and engine stalling problems.
The most successful vertical take-off and landing fighters use deflected engine thrust to provide the lift needed to hover the aircraft. The only AV-8B in service today is to use a high bypass ratio engine, the fuselage on both sides of the front and rear each side of a nozzle can be deflected downward, when vertical takeoff and landing four nozzles together to rotate to a vertical down position, to provide the aircraft vertical hovering thrust, horizontal flight is deflected backward to provide the aircraft forward thrust. The engine diameter is too large for the aircraft to fly supersonic due to its shape.
Simply put, the development of the vertical take-off and landing fighter can be summed up as follows: first the upright aircraft, then the upright engine, then the deflector engine, and finally the dawning realization that only deflecting thrust was needed.
F-35 Lightning II: Dual Mode Engines
One of the key conclusions of the U.S. Navy's Sea Based Air Master Study (SBAMS) for the future fleet in 1980 was that with the technology available at the time, it would be much more expensive for the Navy to have an all-STOVL fleet than a conventional ship-based fleet. Based on this conclusion, NASA initiated the Advanced Short Take Off and Vertical Landing (Advanced STOVL) program to develop technologies to reduce the cost of supersonic STOVL aircraft. From 1980 to 1987, NASA funded research by major aircraft companies on a concept for a supersonic successor to the AV-8B, based on the Lockheed tandem fan engine from Rolls Royce.
The tandem fan engine was a longer version of the conventional engine, with the first stage fan moved forward. During the vertical takeoff and landing phase, an auxiliary air inlet was opened to increase airflow, and exhaust gases were injected from a nozzle in the front fuselage. However, changing the airflow of the front fan weakens the engine's supercharge effect, so that in vertical takeoff and landing mode, although the air intake volume increases, the total thrust is less than the cruise thrust, so the engine has to be enlarged to meet the hovering thrust demand. The thrust of the tail engine nozzle, the whole engine as close as possible to the aircraft's center of gravity, the formation of the wing, fuel, load, engine all crowded near the center of gravity, it is difficult to design a streamlined supersonic aircraft shape.
In the summer of 1986, the Department of Defense (DoD) reviewed the results of the various aircraft companies' designs and concluded that there were no significant cost or performance advantages to their concepts, but some of them were good, including Lockheed's tandem fan engine design, and the DoD encouraged the development of new technologies to improve the performance of these designs, and Lockheed continued to work on them until 1991.
During this period, NASA also worked with Lockheed's Shunk Works on the installation of a boost engine on the F-117 to evaluate the technology needed to build a stealthy STOVL Strike Fighter.
The Defense Advanced Research Projects Agency (DRAPA) expanded NASA's research by funding a nine-month study at the Skunk Works to design a supersonic stealth fighter for the Marine Corps that would be capable of performing the F/A-18's air superiority mission, as well as the F/A-18's air superiority mission.
The AV-8's airborne close support mission, which combines supersonic and vertical takeoff and landing performance requirements, means that the engine must not only provide enough thrust for short takeoffs and vertical landings, but also not be so large as to increase supersonic wind resistance. The key to the development of this new fighter was the engine.
The ideal vertical takeoff and landing fighter would have a thrust-to-weight ratio of about 1.2 to provide sufficient vertical acceleration and maneuvering thrust. A conventional F/A-18 typically has a takeoff weight of about 16,783 kg (37,000 pounds) and 9,979 kg (22,000 pounds) of engine static thrust, a thrust-to-weight ratio of only 0.6, which can be increased to 0.95 with power on. the F/A-18 would need 19,958 kg (44,000 pounds, 1.2 times its takeoff weight) of net thrust for a vertical takeoff and landing, and the existing aft thrust provided by the F/A-18 would be about 1.5 times its takeoff weight. The problem with developing a vertical take-off and landing fighter was how to double the thrust, which had to come from the forward fuselage, to balance the plane's center of gravity.
Lockheed used brainstorming to find the answer. The company made a three-column list of how to get power from the high-pressure hot air in the tail engine, how to transfer power from the tail to the nose, and how to convert that power to thrust, then picked any combination of the columns and figured out how to make it work. The engineers at the Skunk Works came up with some very creative ideas in this way, such as the idea of using the power of a tail jet to drive a gas laser, which sends energy to the front fuselage, where it ignites a pulse jet engine (a laser pulse engine that uses laser energy to heat up a neutral propellant or gas medium in the engine, creating a transient high-temperature, high-density plasma that expands rapidly and is then removed from the engine). (Thrust could be generated by spraying out of the nozzle at a very high speed).
However, none of these concepts were feasible, and Lockheed finally came up with the idea of a drive shaft to transmit engine power forward to drive the forward fuselage lift fans, and the aft engine nozzle could be deflected downward, with additional engine bypass airflow arranged at the wingtips on both sides. Adjusting the thrust of the front and rear fuselage controlled the pitch of the fuselage; adjusting the bypass airflow at the wingtips controlled the deflection of the fuselage.
Lockheed also showed DARPA a sketch of how this design concept could be applied to the F-117. In the original sketch, the axis of the lift fan was oriented in line with the aft engine axis, and the thrust was deflected downward using a rotating nozzle similar to that of the AV-8.
DARPA was interested in the concept and in January 1989 provided funding to the Skunk Works for the conceptual design of an aircraft using this engine, and DARPA also asked McDonnell Douglas and General Dynamics to conduct their own conceptual design studies for an advanced STOVL fighter.
There were three mission requirements for the conceptual design: air proximity support, Combat Air Patrol, and Deck Launched Intercept. was that the aircraft's empty weight could not exceed 10,886 kilograms (24,000 pounds), about 5 percent more than the empty weight of the F/A-18, and about the same amount of weight added by converting a conventional take-off and landing fighter to a shipboard version.
Lockheed's original concept of the F-117 vertical take-off and landing fighter was quickly shelved because of its excessive wing sweep and unstable pitch attitude even at normal angles of attack. The Lockheed concept of the advanced STOVL fighter was based on a delta-plus-canard configuration. The canard acted as a weathervane during subsonic cruising and maneuvering, generating no lift or drag, but when the center of gravity shifted back during supersonic flight, or the flaps folded, it generated an adjusting torque to keep the nose from dropping. The aircraft's internal weapons bay can carry two AIM-120 advanced medium-range air-air missiles and two short-range AIM-9 Rattlesnake missiles. The model of this aircraft will need to complete wind tunnel blowdown and radar cross-section measurements to verify the accuracy of the analytical predictions.
DARPA was interested in the concept and in January 1989 provided funding to the Skunk Works for the conceptual design of an aircraft with this engine, and DARPA also asked McDonnell Douglas and General Dynamics to conduct their own conceptual design studies for an advanced STOVL fighter.
There were three mission requirements for the conceptual design: air proximity support, Combat Air Patrol, and Deck Launched Intercept. was that the aircraft's empty weight could not exceed 10,886 kilograms (24,000 pounds), about 5 percent more than the empty weight of the F/A-18, and about the same amount of weight added by converting a conventional take-off and landing fighter to a shipboard version.
Lockheed's original concept of the F-117 vertical take-off and landing fighter was quickly shelved because of its excessive wing sweep and unstable pitch attitude even at normal angles of attack. The Lockheed concept of the advanced STOVL fighter was based on a delta-plus-canard configuration. The canard acted as a weathervane during subsonic cruising and maneuvering, generating no lift or drag, but when the center of gravity shifted back during supersonic flight, or the flaps folded, it generated an adjusting torque to keep the nose from dropping. The aircraft's internal weapons bay can carry two AIM-120 advanced medium-range air-air missiles and two short-range AIM-9 Rattlesnake missiles. The model of this aircraft will need to complete wind tunnel blowdown and radar cross-section measurements to verify the accuracy of the analytical predictions.
The Skunk Works also used Pratt & Whitney's engine simulation software to verify that the lift fan engine would indeed get enough power from the main engine to propel the lift fan, and Lockheed turned the direction of the lift fan axis perpendicular to the fuselage to get maximum hover thrust.
Allison Engines innovated with a lift fan consisting of two counter-rotating fans, using two sets of drive gears, each transmitting only half the power and thus halving the load, about the same as today's heavy transport helicopter gearboxes. Allison also designed a secondary clutch to connect the lift fans to the drive shaft, using a multi-plate friction clutch that would first slip to reduce the vibration of the engagement when the lift fans were accelerated from standstill to the same speed as the engine, and then mechanically lock to transmit all the power needed for a short takeoff or vertical landing.
In the fall of 1989, DARPA arranged for Lockheed, McDonnell Douglas, and General Dynamics to brief their respective conceptual designs at Naval Air Command (NAVAIR), and all three companies subsequently renewed their contracts with DARPA to refine their designs and assess the feasibility of adopting a stealth design. The follow-up study was completed in late 1990, and the Marine Corps, after reviewing the complete results, asked Lockheed to further enhance the conceptual design to allow the Marine Corps to choose between a drive-shaft lift fan and an aerodynamic lift fan.
But in December 1990, then-Secretary of Defense Dick Cheney, for the second time, wanted to end the V-22 program. A few weeks later, in January 1991, Cheney terminated the long-running Navy A-12 program, the Secretary of the Navy asked Naval Air Command to focus all of its efforts on the A-FX stealth fighter program to replace the A-6, and Lockheed's focus was shifted from the Advanced STOVL to the Advanced STOVL. In May 1993, Lockheed obtained a U.S. patent for a drive shaft lift fan.
The Common Affordable Fighter (CALF)
In mid-1991, DARPA and Lockheed continued to brief the House Budget Committee and DOD officials to ensure adequate funding for research into the technology maturation and risk mitigation of the advanced STOVL strike fighter, which led then-Assistant Secretary for Research, Development and Weapons Acquisition Gerry Cann to deliver the Naval Advisory Committee (NAC) in early 1992. A new effort by the Research Advisory Committee to assess the feasibility and urgency of developing an advanced STOVL strike fighter.
In April 1992, General George Muellner, then Deputy Chief of Staff of the Air Force Operations Command, visited Lockheed's Skunk Works to inspect the latest developments at the facility. As the Air Force was beginning to conceive of the so-called MultiroleFighter to replace the F-16, Lockheed briefed Moline on a stealthy conventional takeoff and landing fighter. Lockheed removed the lift fan and vector nozzle from the advanced STOVL strike fighter and replaced them with a fuel tank and conventional nozzle, which reduced the aircraft's empty weight by about 15 percent, increasing range and reducing costs.
Lockheed recommended that the Air Force and Marine Corps jointly develop a Common Strike Fighter, which would allow both services to obtain the fighter at an affordable price. Since the U.S. Navy, Air Force, and Marine Corps had a history of working together on the F-4 Phantom II, Lockheed found this proposal quite feasible.
Brigadier General Morin asked Lockheed to provide further briefings to the Air Combat Command staff at Langley Air Force Base, and prior to the follow-up briefings, Lockheed persuaded DARPA to arrange a briefing to Air Force Chief of Staff General Merrill McPeak, Chief of Naval Operations Chief of Air Warfare Assistant Vice Admiral Richard Dunleavy, Office of the Secretary of Defense, briefed the Secretaries of the Services on the idea. By the summer of 1992, the Naval Advisory Committee determined that the STOVL strike fighter was feasible and recommended that the Navy and Air Force jointly support the development of a highly interoperable, multi-role fighter for use by both the Air Force and Marine Corps.
With the full support of the Department of Defense, Congress appropriated funds for DARPA to initiate the joint STOVL and Conventional Takeoff and Landing Strike Fighter programs, and in August 1992 DARPA issued a Request for Proposal (RFP) to industry to conduct technology demonstrations of shaft-lift and pneumatic-lift fans, as well as the Common Affordable Lightweight Fighter (CALF). In March 1993, Lockheed and McDonnell Douglas were awarded a contract by DARPA to develop a conceptual design for the Common Affordable Lightweight Fighter, which was the first time the Defense Department made the program public, and the date was set for the birth of the Joint Strike Fighter program.
In March 1993, Lockheed and McDonnell Douglas were contracted by DARPA to refine the drive-shaft lift fan and pneumatic lift fan technologies, respectively. Lockheed chose Pratt & Whitney because the F-22 used Pratt & Whitney's F119 engine, the only new engine in production at the time, and Lockheed believed that Pratt & Whitney was the only company capable of supplying the new engine for the demonstrator. engine, Lockheed also requested that Pratt & Whitney develop a drive-shaft-driven lift fan engine exclusively for Lockheed.
A year later, in March 1994, Congress appropriated an additional $6 million for research into the design of a dual-purpose lift/cruise engine, which was considered less risky because the engine concept had already been used in the AV-8. Boeing said it was willing to provide the same amount of money on its own, and thus was awarded the engine design contract by DARPA.
DARPA required Lockheed, McDonnell Douglas, and Boeing to design production and demonstration aircraft and to conduct ground dynamics tests with full-scale models to reduce development risk. These tests will demonstrate that the lift fan engine concept is feasible, that the hot gases emitted by the lift fans will not damage structures, and that the aircraft has sufficient maneuverability to convert from hovering to forward flight. The full-scale model was requested because DARPA was concerned that the true temperature and turbulence effects of the lift airflow would not be represented if a small-scale model was used because of its size.
The Lockheed's full-scale model has the same profile as the original STOVL strike fighter design: swept-back main wing, canards, vertical-lift fan engine, and built-in weapons bay, but the aircraft's aerodynamics have been recalculated based on F-22 flight test data.
The mission requirement for the multi-role fighter has four additional ground attack missions, and the design emphasis has changed from an air superiority fighter with strike capability to a strike aircraft with partial air-to-air self-defense capability. As stealth and long-range air-air missile technology have changed the nature of air combat, the design emphasis is on "first look, first shot", reducing the need for close combat, so the original two AIM-9 Rattlesnake short-range air-air missiles are eliminated, and the in-flight weapons compartment is replaced with a new AIM-9 Rattlesnake missile. In addition to the original two AIM-120 medium-range air-air missiles, two 907-kg (2,000-pound) class Joint Guided Attack Munitions (JDAMs) had to be accommodated, resulting in a small increase in both forward field of view (FLOR) and wave drag (WDR). The air force configuration remains the same as before: lift fans and vector thrust nozzles are removed and replaced by fuel tanks and conventional nozzles.
Although analysis and computer simulations showed that the F119 engine could theoretically provide enough power to drive the lift fan, it was doubtful that it would do so in practice. Lockheed was concerned about the loss of thrust from the engine nozzle deflecting at large angles while the fuselage was hovering; whether the lift fan thrust and the aft nozzle thrust could be adjusted quickly and cooperatively to control the aircraft's pitch attitude; and the weight and reliability of the lift fan's drive shaft, clutch, and gearbox.
The demonstration engine system should be able to clarify these concerns and demonstrate the feasibility of a dual-mode engine and drive system. The lift fan was taken from the first stage fan and inlet guide vane of the YF119 engine. The transmission configuration was identical to that of the future production lift fan, so the gearbox load was the same as the production model. The engine, on the other hand, uses the fan and core of the Pratt & Whitney low-bypass F100-PW-220 engine with the turbine section of the high-bypass F100-PW-229 engine. The turbine was large enough to provide enough power to drive both the lift fan and the engine fan; the engine had openings on the left and right sides of the outer case to channel the bypass airflow into a jet stream that controlled the aircraft's roll; the engine fan rotor was modified to mate with the clutch; and a variable-area vectored thrust nozzle was located at the rear of the engine.
In December 1994, the assembled lift fan, gearbox, and driveshaft were validated at the Allison plant to measure power transmission losses in the gearbox, verify the operation of the lubrication and lubrication system in vertical attitude, establish twist limits for the blades, and demonstrate the ability of the inlet guides to regulate fan thrust. This validation was quite successful, proving that it was feasible to build a lift fan and gearbox for flight with a given power requirement.
The force fan was then sent to Pratt & Whitney's facility in West Palm Beach, Florida, where it was attached to a validation engine in February 1995 and operated in cruise and STOVL modes, demonstrating the ability of the engine's turbine to switch between providing cruise thrust and driving the lift fan, and demonstrating the rapid power transfer between the cruise engine and lift fan, as well as pitch control. The Capabilities.
Following these tests, the complete propulsion system was mounted on a full-scale model airframe made of fiberglass and stainless steel and tested at the outdoor hover test facility at NASA's Ames Research Center. Tests showed that ground effects caused induced sinking forces of less than 3 percent of thrust, and that the lift enhancer effectively limited induced sinking forces at landing gear height to a fairly low 7 percent. When the fuselage was hovering at 0.3 m above the ground, no hot exhaust gases were observed to flow back into the engine inlets over a wide range of pitch and roll angles.
NASA's 37-meter-long wind tunnel tested the model's power conversion characteristics, and based on data from the wind tunnel under a large deflection angle of the flaps, showed that the aircraft could take off and land safely on the Landing Helicopter Dock (LHD) without a landing hook or catapult in deck winds of 20 knots, and was large enough to switch from vertical hover to a vertical hover in a given space. forward flight. The measurements also show that during the transition, even with 20 knots of side wind, the aircraft has sufficient control over acceleration, deceleration, and sideways attitude.
The Joint Advanced Strike Technology (JAST)
In February 1993, at the same time as the start of the Common Affordable Light Fighter program, the United States Department of Defense conducted a Tri-Service Modernization Review (TSMR) to, among other things, evaluate five tactical fighter development programs then underway: the United States Air Force's F-22 and Multi-Purpose Fighter, the United States Navy's F/A-18E/F and A/FX, and DARPA's Common Affordable Light Fighter. The U.S. Navy and Air Force gave a joint briefing to the reviewers, recommending the development of a highly versatile multi-role fighter, called the Joint Attack Fighter (JAF), based on the STOVL strike fighter.
The review, released in September 1993, ended the multi-role fighter and the A/FX program, but continued to approve the development of the technology needed for the Joint Strike Fighter to replace the AV-8, F-16, and F-18, which were scheduled to be removed from service in 2010, and to initiate the Joint Advanced Strike Technology (JAST) program, but this was not done. The program did not initially include the STOVL, which was requested by the Marine Corps.
On 27 January 1994, the JAST Program Office was established to define and develop the airframe, weapons, and sensor technologies required for the future fighter aircraft. The fighter is the most economical way to meet the needs of the three services. After many subsequent trade-off discussions, the plan decided on a single-seat, single-engine version of the utility fighter. The Navy's preference for a two-engine, two-seat fighter required that the future single-seat fighter be capable of performing the full range of missions the Navy expected.
In October 1994, the U.S. Congress directed DARPA to incorporate the General Affordable Light Fighter (GALF) and Marine Corps STOVL into the JAST program, which became the Tri-Service General Purpose Fighter (TPM) development program. The Navy's primary need for this fighter was the ability to take off and land the fighter in 91 meters with deck winds of 20 knots. Lockheed considered three options for how to meet the demand.
Option one was to have the Navy also use the STOVL configuration developed for the Marine Corps. This was the simplest option, but the range and payload capability of this model was less than that of the conventional carrier-based version.
The second option is to remove the lift fans from the STOVL configuration, allow the attitude adjustment jets to flow over the flaps to increase wing lift, reduce the takeoff and landing speed of the aircraft, and add ejectors and blocking hooks. However, the F-4 Ghostbusters used by the Navy in the past had a similar blown flap design that was very difficult to maintain, and Lockheed did not think the Navy would be interested in this option.
The third option Lockheed chose to adopt was to increase the flaps and leading edge flaps, with the wingtips slightly extended outward to increase wing area, reduce takeoff and landing speeds, and add ejectors and blocking hooks. The larger wings reduced induced drag and increased the fuel tank capacity in the wings, so the naval models had a longer range than both the Marine and Air Force models.
Lockheed hooks put a lot of load on the landing gear and fuselage, so Lockheed redesigned the main landing gear. The design specification for the Air Force and Marine models was a maximum rate of descent of the fuselage on landing of 3 meters per second, compared to 7.62 meters per second for the Navy model. The front landing gear was also redesigned to accommodate the ejector, and the fuselage was designed with cushion parts to accommodate the greater loads, replacing them with stronger parts without changing the basic structural arrangement. 1.90 cm thick titanium alloy. This approach was inherited from the F-16 production line, initially to meet different national requirements for subsystem components, resulting in the F-16 having many different configurations under the basic fuselage.
As the concept of a drive-shaft-lift fan was quite new and considered the highest risk, the original duck wing was replaced with a conventional horizontal tail to reduce the overall risk.
In May 1995, Lockheed asked Yak Aircraft Corporation, the Russian company that had developed the Yak-38 and Yak-141 Vertical/Short Take-Off and Landing fighters, to provide the STOVL propulsion system and structural arrangements for the F-16. Independent Review Opinion. Lockheed submitted the published design data for the General Affordable Light Fighter from other companies, as well as Lockheed's own patent application documents for the propulsion system to Jacques, who estimated the performance and risks of the three competing STOVLs based on their own development experience. The company's review report was quite positive about Lockheed's design and provided Lockheed with information on the design performance of the vertical/short takeoff and landing aircraft lift system for Lockheed's reference, giving Lockheed a shot in the arm.
After the final wind tunnel blow tests were completed, the three bidders also completed demo and production aircraft designs. The Lockheed and McDonnell Douglas designs are quite similar: a conventional wing, fuselage and tail profile; the Boeing is a delta-wing fuselage without a tail. Lockheed had already tested hovering and attitude changes on a full-size model; Boeing had only completed lift tests on a full-size model; McDonnell Douglas had asked Lockheed to work with Pratt & Whitney on a shaft-driven lift fan system after completing tests on a gas-driven lift fan system, but was turned down and had to develop a lift engine that had never been tested on a full-size model. At this point, Lockheed's design turned out to be the least risky by comparison of the three companies.
Joint Strike Fighter Program (JSF)
In September 1995, the United States Department of Defense conducted a projected assessment of the 2010 fighter shortfall and reviewed the JAST programme launched to address the problem, with the significant conclusion that an aircraft that meets the requirements of the three services could save up to one third of maintenance costs. In addition, the same maintenance unit, a shared logistics warranty system and increased interoperability would result in a significant reduction in procurement costs, which required the Department of Defense to develop a new general-purpose fighter for the program and to adopt the Joint Strike Fighter development plan in February 1996. The company was required to develop the purpose of the demonstrator's test flight together. Lockheed submitted an offer in June, stating that the company's three main objectives for the demonstrator flight were: first, to prove that it was feasible to build a conventional, STOVL, and carrier-based Joint Strike Fighter; second, to demonstrate unprecedented STOVL performance and supersonic flight in the same flight; and third, to demonstrate the carrier-based fighter's handling qualities and carrier adaptability.
Lockheed's plan is to build two demonstrators, one to test the more challenging STOVL and the other to adopt the Air Force configuration before replacing the flaps and leading edge flaps with the carrier-based version. To reduce the manufacturing cost of the demonstrator, some of the subsystems not related to the test target were used off-the-shelf (e.g. front landing gear was taken from the F-15 and the main wheels were slightly modified from the A-6), and the additional weight of these off-the-shelf parts was offset by the absence of mission avionics and weapons bay.
In May 1996, the Department of Defense changed the name of the program to Joint Strike Fighter Program to reflect the actual scope of the program and to let Congress know that it was a fighter development program. In 1997, McDonnell Douglas was acquired by Boeing, and BAE Systems and Northrop Grumman, who had previously teamed up with McDonnell Douglas to bid for the aircraft, joined Lockheed.
Both Lockheed and Boeing are quite traditional in their design profiles, and the F-22 proved that the shape of the aircraft can reduce the radar cross-sectional area, if not the polyhedral approach, so the deciding point for both companies was the propulsion system design of the STOVL. Thrust is the product of airflow and velocity. Lockheed uses a lot of slow airflow to achieve the high thrust required; Boeing uses a small amount of fast airflow. The Lockheed lift fan system emits about 2.5 times more airflow than Boeing's lift system and less than a third of the airflow velocity.
Due to the success of the STOVL wind tunnel at NASA Ames Research Center, Lockheed's plans for the demonstrator were modified to reduce the cost of the aircraft, with one aircraft built to verify carrier performance and another built in the Air Force configuration before removing the forward fuel tank and installing the boost fan. During the following month, the X-35A flew an average of one sortie per day, demonstrating maneuvering and supersonic performance, and fully meeting its intended flight test objectives.
What made the flight test so successful was the X-35A's ability to refuel from the air. The fact that Boeing was unable to use aerial refueling during the test flights, which normally takes a year of test flights for new aircraft to pass this certification, also demonstrates Lockheed's technical capabilities.
In late 2000 and early 2001, the X-35A was converted to a STOVL X-35B with lift fans and vector thrust nozzles, and during the first half of 2001, the aircraft was bolted to a flat-ground steel net to reduce ground effects, inspecting and measuring engines, lift fans, nozzles, and reaction control systems. 23 June 2001, British Aerospace Systems test pilot The X-35B also confirmed its ability to convert from vertical to horizontal flight by completing 38 test flights at Edwards Air Force Base in July 2001, when Simon Hargreaves first throttled the aircraft about six metres above the ground to test the response of the control system in such conditions.
On 20 July 2001, Major Art Tomassetti of the Marine Corps flew the X-35B on the first-ever complete flight of short takeoff, supersonic flight, hover and vertical landing, a capability that Boeing's X-32 was unable to demonstrate, and the aircraft's final flight, on 6 August 2001, was flown by Lockheed test pilot Morganfield. Tom Mongenfield) flew it back to the Palmdale facility.
The second demonstration aircraft configuration, an X-35C naval version, first flew on 16 December 2001 and successfully demonstrated a simulated carrier landing with a side-stick maneuver during 33 flight hours of testing at Edwards AFB. AirStation), becoming the first X-Series aircraft to fly across the continental United States. During an additional 33 flight hours of testing on the Patuxent River, the X-35C completed supersonic flight and more than 250 simulated carrier landings.
The test flights of the Type III X-35 confirmed that Lockheed's Joint Strike Fighter airframe and propulsion systems were mature and viable technologies.
In November 2000, the Joint Strike Fighter Program Office asked the Boeing-Lockheed II competition team to propose a plan for the manufacture and testing of 22 system development verification aircraft, 8 ground test aircraft and 14 air test aircraft. (Roche) said, "Both teams' planning was excellent, but the Lockheed team was superior in terms of strengths, weaknesses and risks. With each step of the selection process, the evidence that the team could provide best value to the DoD became more and more apparent." General defense analysts also believe Lockheed's demonstrator is superior to Boeing in terms of engine design, performance and operational risk, and that Boeing is also more able to absorb the losses associated with a defeat.
The Lightning II
The F-35A/B's wingspan has been increased slightly to improve maneuverability and range; the rudder and horizontal tail have been replaced with a new design to reduce weight; and the ram air cooling system has been replaced with a liquid cooling system similar to that of the F-22. The STOVL's in-flight weapon doors open during vertical landing to trap the lift airflow and reduce the downdraft of ground effects on the fuselage.
The cockpit of the Developmental is much more advanced than that of the Demo. The X-35B's flight controls are similar to those of the Harrier, with flight controls, throttles and a separate nozzle lever. The cockpit instrumentation on the X-35 included a HUD and two small color displays borrowed from the C-130; the F-35's cockpit used a virtual display projected onto the transparent visor of the pilot's helmet and a small screen that could be divided by the pilot himself. The large instrument display.
The weight of the development model has also risen as a result of enhanced performance requirements, such as increasing the G-value limit of the aircraft from 7.5 to 9 G's, increasing the wing structure to carry external loads, reducing the number of wing joints to simplify assembly, redesigning the fuselage structure to accommodate subsystem components and access space, etc., etc., and by January 2004, the aircraft had gained more than 1,000 pounds. 1360 kg. To offset this extra weight, Lockheed offered an incentive in April 2004, with a $100 bonus for any weight reduction proposal and a $500 bonus for 1 pound of weight loss. By the end of the year, Lockheed had received more than 2,000 proposals, reduced the aircraft's weight by more than 1,225 kilograms and paid out about $1.35 million in bonuses.
On February 19, 2006, the first USAF F-35A left Lockheed's Fort Worth, Texas factory, and after a series of ground tests, it was officially unveiled to the public on July 7, 2006. The USAF named it Lightning II, hoping to continue the glory left by the P-38 and the British Lightning. War Trail, which completed its maiden flight on December 15, 2006. The first STOVL F-35B was introduced a year later on December 18, 2007, completed its maiden flight on June 11, 2008, and after completing a number of conventional takeoff and landing test flights by the end of that year, completed its first short takeoff, hover and vertical landing on March 18, 2010, and its first supersonic flight on June 10, 2009. -35C ex-factory, maiden flight completed on June 6, 2010.
The Joint Strike Fighter program was 13 months behind schedule in early 2010, which changed the original schedule for the completion of Initial Operational Capability (IOC) for the three services. The Navy expects to peak at less than 177 fighters in 2017, and even with contingency measures to extend the service life of the F-18, the shortfall will still be too large to meet readiness requirements. Nearly 100 will be shipped.
The U.S. Government Accountability Office has also warned that the Joint Strike Fighter is expected to ship 360 units before it completes its operational test evaluation, but if any deficiencies are found during the testing process, it will cost a lot of money to modify the production line and it will cost a lot of money to return the aircraft to the factory for modifications, which will have a negative impact on future aircraft. The price must have an adverse effect.
Production challenges
The Joint Strike Fighter was originally intended to replace the Air Force F-16, Navy and Marine Corps F/A-18, and Marine AV-8 with a general-purpose aircraft that would save on production and life-cycle costs, but in reality it has been a major disappointment to the nations involved in its development. By early 2010, the program budget had already exceeded the original estimate by one-and-a-half times, reaching $382 billion, and the projected price of the individual aircraft had risen to $112 million. The Nunn-McCurdy (Nunn-McCurdy) Military Procurement Act called for a mandatory investigation, only to be followed by an April 2010 report indicating that there was no cheaper alternative to the F-35, but that a new feasibility cost and schedule goal would be set, and that the Department of Defense intended to implement a fixed-price contract, with Lockheed taking on the future at its own expense. Risks of rising costs in the production process. In order to stem the upward trend in prices, Loma will reduce the price of its production aircraft with lean production.
The total global demand for the JSF is estimated at nearly 5,000 aircraft, and the production line will have to produce 240 of the three versions of the JSF per year at its peak in the future, almost one per day after weekends and holidays, which is about the same as the production line for civilian aircraft. Although the three JSF types were designed to meet the specific requirements of the different military services, they were still very similar to each other, and the initial airframe design required that their differences not interfere with production and assembly. For example, the carrier-based F-35C has a faster descent speed during landing, so the side frames must be stronger, but the side frames of all three types are forged using the same forging dies and milled using the same machinery to remove superfluous material.
The F-35 is built on a moving assembly line, moving at 1.72 meters per hour, using simple, mobile machinery. Since British Aerospace Systems, which designed the Eurofighter assembly line, was also a JSF production partner, the main JSF assembly was positioned with the same laser tracker as the Typhoon during final assembly, the JSF assembly was designed with simple joints, few rivets, and the entire production system was based on a single numerical model of the aircraft, without the traditional paper-based system. Blueprint.
The F-35's single-piece wing skin, the largest composite fighter skin ever made, was manufactured by Lockheed with machinery purchased in Switzerland to keep the skin's dimensional tolerance within the range of a hair's breadth. Lockheed's original production of wing skins used polycrystalline diamond router machines, which required up to 24 units to complete a single finished product, and often resulted in severe delamination of the skins, necessitating extensive repairs, which had a highly detrimental effect on manufacturing costs and schedules. Lockheed then turned to the National Center for Defense Manufacturing and Machining in Pennsylvania, which has been using AMAMCO Tool's diamond-coated drill presses since the center's inception. The F-35's planer, which was developed by Lockheed and 3M, reduced the number of planers from 24 to 2 and increased the length of a single planer from 2.74 meters to 17.37 meters.
The F-35's fuselage skin is covered with a coating developed by Lockheed and 3M, which is very different from the paint used on conventional aircraft. It is not technically a coating, but a thin layer of polymeric material that can be applied directly to the skin, so there is no need to paint the skin. The biggest advantage is that it saves money and also reduces the additional weight of the aircraft due to painting, a measure that will save at least 300 kilograms of paint over the life of the aircraft. The new polymer thin layer has already passed feasibility tests on the F-16, and when flying at Mach 1.8, this thin layer is still intact. However, according to current information, the F-35 is still using the traditional coating technique. According to Hanwuji, the stealth paint used on the F-35 has better durability and is easier to maintain. And there is a certain redundancy design, meaning that coating damage is within a certain range and the stealth is still better than the military requirements.The F-35's coating is done by spraying robots and has a fairly high level of flatness. The technology is said to be so advanced that the U.S. is even considering having F-35s assembled overseas flown back to the U.S. for final coating work in order to prevent the spread of the technology. The U.S. Air Force is considering switching to the F-35's stealth paint for the F-22, which is said to require only modest modifications, and the F-35's paint can meet the F-22's requirements at high altitudes and high speeds without degrading its stealth performance.
Lockheed uses a fully automated, numerically controlled stack drilling technique to temporarily fix the outer skin to the fuselage structure, and then uses a drill bit to simultaneously attach the outer skin to the fuselage structure. The holes for the fasteners are drilled to allow for virtually no tolerance between the two structures; to install the fasteners, Lockheed uses a Laser Projection System to project the part numbers on the skins, eliminating the need for contractors to read complex blueprints.
Lockheed's newest tool for inspecting composite structures is Laser Ultrasonic Technology, which was recently developed after 20 years of research and development. This technology uses 400 Hz frequency laser ultrasound to detect cavities, cracks, delamination or other flaws in composite structures, and can scan and inspect composite structures of any shape at a speed of 0.55 square meters per minute, more than 10 times that of conventional instruments. With traditional instruments to perform the F-22 Raptor (Raptor) in the fuselage structure of the fiber overlays of impurities, bubbles, cracks in the non-destructive inspection, would take 24 hours, laser ultrasound technology takes less than an hour.
Concluding Remarks
The F-35 Joint Strike Fighter is a ground-attack based multi-role fighter with the ability to attack any target on land, sea and air at all hours of the day and night. In the future air battlefield, the F-35 will join forces with the F-22 to create a high-low pairing similar to that of the F-15 and F-16. After the F-22 clears the threat from enemy fighters and surface-to-air missiles, the F-35 will carry missiles for all-weather precision strikes against scattered ground targets.
The F-35 has three obvious advantages over the current fighter: First, a single-engine thrust generated by more than twin-engine propulsion of the Eurofighter and F-18E/F Super Hornet (Super Hornet); Second, strong stealth performance, not easy to be detected by enemy radar, can be as stealthy as the F-117 fighter to break through enemy air defenses; Third, the missile weapons do not have to be mounted on the biplane, so that the F-35 will be able to carry a missile on board. The F-35 can be more maneuverable and flexible in engaging enemy aircraft in air combat. In addition, the F-35's ability to conduct precision strikes out of line-of-sight, coupled with the aircraft's stealth capability, will enable it to spot enemy targets first, fire offensive weapons first, and take the initiative on the battlefield, greatly enhancing the F-35's combat performance.
As a result of this superior performance, the program estimates that the three JSFs are expected to replace nearly 5,000 fighters from at least 11 nations and 13 aircraft types worldwide. With the same airframe, engines, avionics, and subsystems, the development and support costs of the three JSFs would be shared among a large fleet of aircraft, each of which would be cheaper, giving the F-35 the opportunity to become the most cost-effective fighter in history, but as it stands, the price per aircraft has risen steadily and is on par with the F-22, contrary to the cost-reduction demands of joint development.
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