Japan can’t outgun China’s J-20 with F-35A purchase


This undated handout file image obtained courtesy of the Joint Strike Fighter program site shows the F-35 fighter jet. (Photo/CFP)


As the US is refusing to sell Japan the Lockheed Martin F-22 Raptor fighter, the Japan Air Self-Defense Force (JASDF) will have to settle for the Lockheed Martin F-35 Lightning II instead, according to an analysis piece posted on Sina’s military news web portal.

The F-35 will still allow the JASDF entry into the stealth fighter club, however. China is likely to respond to the Japanese fighter upgrade with appropriate measures of its own, said the website.

F-35 Overall Analysis

There is already a dearth of articles concerning the Joint Strike Fighter (JSF) research and development projects and profiles of the F-35, so the article on the Sina web portal focused on maneuverability, stealth and sensors and electromagnetic interference. From an overall design perspective, the F-35 has a similar conventional aerodynamic configuration to the F-22. Its main wings differ from the delta wing of the medium bomber version of the F-22, in that they take a trapezoid mid-wing configuration, with the back sweep angle of the leading edge of the main wings at 35 degrees and the trailing edge front sweep angle at 15 degrees.

The twin tailfins are canted outward at an angle of 25 degrees. The backsweep angle on the horizontal plane of projection is 35 degrees too. The weapons bay has four pylons and on anti-aircraft missions it typically carries two AIM-120 air-to-air missiles and two AIM-9 Sidewinder short-range air-to-air missiles; when striking ground targets, it typically carries two AIM-120 missiles and two 907 kilogram guided bombs. The F-35 has improved stealth capability in terms of scattering head-on radar; its diverterless suspersonic inlets (DSI) are located on either side of the front of the body of the plane and it has no moving components and the serpentine inlet hides the face of the entire engine.

F-35 Maneuverability

According to an article entitled The Analysis of Aerodynamic and Stealth Characteristic of F-35 Fighter in the Chinese journal Aircraft Design, at subsonic speed, the F-35’s lift coefficient at an angle of attack of 30 degrees and a speed of Mach 0.3 can reach 1.6, while its lift-drag ration at an angle of attack of 5 degrees and a speed of Mach 0.5 can reach a maximum of 16.

As the angle of attack increases, however, the lift-drag ration falls sharply. At an angle of attack of 10 degrees, for example, the lift-drag ratio falls to 8. This is why the F-35 has been able to improve on cruise capabilities at Mach 0.5, useful for long range ground attacks at medium speeds.

However, this optimal cruise speed is a little slow for subsonic air-to-air combat, as even large Boeing passenger planes have a cruise speed of around Mach 0.8. The F-35 is more reliable at a 30 degree angle of attack at subsonic speeds, a major improvement on third-generation aircraft, but because the lift-drag ratio falls rapidly with an increasing angle of attack, the stability of turns for the F-35 is dependent upon a strong engine.

In terms of transonic flow, the lift coefficient of the F-35 is 1.7 at an angle of 35 degrees and a speed of Mach 1.1, the lift-drag ratio at an angle of attack of 5 degrees and a speed of Mach 0.9 can reach a maximum of 8.

Third generation aircraft are designed with transonic maneuverability as a priority, but this is clearly not the F-35’s strong point, even though its maximum lift coefficient approaches the 1.8 of France’s Dassault Rafale. Its lift-drag ratio is poorer, however, as its lift coefficient improves, this explains why the cross-sectional area of the body of the plane is quite large, although the back sweep angle of the wings is smaller, which improves subsonic flight, it also leads to heightened resistance in transonic flight. The maximum angle of attack of the F-35 at transonic speeds is still quite large, however, at a maximum of 35 degrees.

In terms of supersonic flow, the lift coefficient of the F-35 reaches 1.8 at an angle of attack of 35 degrees and a speed of Mach 1.3; while at a 5 degree angle of attack at Mach speed the lift-drag ratio reaches 4, a big gap from the F-22’s supersonic lift-drag ratio of 5.

As the bypass ratio of the Pratt & Whitney F135 afterburning turbofan engine is quite large, its propulsion force at high speeds and high altitudes is lesser, making the F-35 comparable to supersonic third generation fighters, although it can’t match the capabilities of third generation fighters with a canard configuration, and is closer to the capabilities of the General Dynamics F-16 Fighting Falcon.

Overall, the F-35 was designed with subsonic maneuverability and long-range subsonic flight in mind, which explains why it is mainly flown in cruise and aimed at launching ground strikes. The F-35 is notable for its maneuverability at all speeds and angles of attack and its stability in making turns at subsonic speeds, making it more agile than third-generation fighters, although it does not perform well at transonic speeds. In sum, the F-35 sees a clear improvement from the F-16 in angle of attack and turning speed, with a slight upgrade in the stability of turns, although its transonic flight capabilities are slightly worse than the stealth version of the F-16. This suggests that it is most suited to be a ground attack aircraft, although it could also be termed a multirole aircraft.

The F-35’s Stealth Capabilities

The plane features the following mechanisms aimed at electromagnetic scattering, listed in order of intensity: corner reflectors, concave resonators, polished surface reflection and knife-edge diffraction, surface backscatter, creeping wave diffraction, second-order and multiple scattering, as well as discontinuous surface scattering.

The corner reflectors between the fuselage and the wings, the vertical tailfins and the horizontal stabilizers and between the external pylons, as well as the concave shape of the nose-mounted Electro-Optical Targeting System, the cockpit and the air inlets also prove very effective in reducing the craft’s radar cross-section (RCS), at around 10-0 decibels, which corresponds to over 10 square meters to under 10 square meters in (RCS). The diffraction and scattering caused by sharp edges and lines on the plane have less of a contribution, at around 0 or -30 decibels, which corresponds to an RCS of one thousandth of a square meter.

The F-35 is equipped with an AN/APG-81 Active electronically scanned array-radar. The radar array face upwards at a slight angle, which reflects incoming radar waves that enter the radar housing away from the receiver. The serpentine air inlets and DSI covers the entire front of the engine and the cockpit is plated with metal to reflect incoming radar, preventing it from entering the cockpit, resulting in scattering; The internal weapons bay prevents reflection between external equipment held on pylons; the leading edges of the wing, the horizontal tail stabilizers and the vertical tailfins are all parallel, as are the trailing edges of the main wing, the horizontal tail stabilizers and the vertical tailfins, which aids in scattering; the surface of the body of the plane employs a sawtooth design, sending creeping wave away from the receiver.

Currently the F-22’s head-on RCS is between -20 and -30 decibels, or one hundredth to one thousandth of a square meter. Due to the sensors embedded in the body of the F-35, it has limited ability to scatter creeping waves. Taking all of this into account, the face-on RCS of the F-35 is likely between -10 and -20 decibels, or between one tenth and one hundredth of a square meter. This means that the F-35 can cut down the distance at which it can be detected by radar from 100 km to 20-40 km.

The F-35’s Radar and Electromagnetic Interference Abilities

As mentioned above, the F-35 is equipped with an AN/APG-81 Active electronically scanned array-radar, which has strong detection capabilities as well as a multi-function integrated radio frequency system (MIRFS), which can carry out electromagnetic interference, facilitate communications and identify targets.

The F-22 is equipped with the AN/APG-77 low probability of intercept radar, composed of 2,200 transmit/receive modules, each with power of around 10 Watts, giving it peak power of 22 kiloWatts. When operating with a duty cycle of 25%, it operates at around 5 kW. Due to the small size of the nose of the craft, the APG-81 radar has less components than the APG-77, although there is currently no concrete figure, it is likely around 1,200, giving it peak power of 12 kW and average power of around 2 kW.

Currently the APG-81 can detect targets of 10 sq m from a distance of around 250 km. If the head-on RCS of the Chengdu J-20 is to be around the same as the F-22, at between -20 and -30 decibels, then the APG-81 could detect it at a distance of 20-40 km. The F-35 is also equipped with a photoelectric sensor, the range and resolution of which is unclear, but likely of higher quality than the Low Altitude Navigation and Targeting Infrared for Night (LANTIRN) installed in US third-generation fighters.

The fire-control radar on board third-generation fighters have no electronic interference capabilities, so an on board electronic jammer has to be used on board. As there is little space for an antenna and a high-frequency transmitter, this falls short of fire-control radar by a long shot, whereas the APG-81 uses the long range radar itself to engage in electronic interference. As the APG-81 has average power of 2 kW for interference, it beats the radar on board the third-generation fighter, at just several hundred Watts, right out of the water. At long-ranges the radar on third generation fighters is left only with its goniometric function, losing the ability to measure distance at all. This, in turn, leads to a loss of target tracking capabilities and its ability to visually simulate attack, which renders it ineffective.

East Asia Disputes: Threats and Countermeasures

Before 2016, the JSF may only be able to buy a few pre-production versions of the conventional takeoff and landing (CTOL) variant of the F-35, the F-35A, to engage in flight tests and will likely only receive the final version of the F-35A a few years down the line. Countries are cooperating in the manufacturing and testing stage of the F-35’s development in different ways. The UK agreed to invest funds of 10% or US$2 billion, under the JAST (now JSF) program office, which grants it priority access to F-35 equipment. The second way is through an investment of 5% or US$1 billion, through which Italy and the Netherlands are participating in the project.

The third way is as a mid-ranking representative, under which participant countries can only make demands for custom details and invest funds of 1% or US$200-400 million. Countries who have chosen to participate in this way included Turkey, Canada and Australia. Later two more categories of participation were added.

Those in the fourth category have to pay at least US$75 million. There are 12 potential countries that may sign up for this. Israel is the only country in the fifth category, under which it needs to pay US$2 million to access data on the F-35 project. Given the above division of categories, Japan will only be able to take part in the project under the fourth category, which means that at least eight countries will have priority in buying the F-35 aircraft and equipment before Japan.

In addition to this, Japan is only buying around 40 F-35A fighters, a relatively small order, which makes it unlikely that it will get quick delivery on its order, compared to those willing to order more. Japan will likely get permission to assemble the F-35A after 2020, which means that the finished aircraft will come off the production line a lot later. Whether or not Japan is granted the right to assemble also depends on Japan’s finances and on the stability in the country’s relationship with the US.

Given the time frame for Japan’s potential purchase of the F-35A aircraft and Japan’s announcement of a project to develop its JASDF, by around 2025, the JASDF will likely have the following equipment and weapons systems: six E-767 early warning aircraft, around 40 F-35A fighters, around 100 upgraded Mitsubishi F-15J/DJ Eagle fighters and 150 Mitsubishi F-2 multirole fighters. Japan’s air defense zones are divided into three areas, north, central and west.

The north zone is aimed at defending against aircraft from Russia; the west zone is aimed at defending against aircraft from China, while the central zone gives Japan strategic flexibility in deployments. This means it is likely that the F-35A fighters will be divided into two squadrons, with 20 being deployed to the west air defense zone and 20 being deployed to the north air defense zone. Two F-15J fighters and one F-2 from the central air defense zone will likely be deployed to the west and north air defense zones, while the rest of the aircraft will serve as strategic reserves in the central defense zone. This will mean that Japan will have fallen far from its title as the No. 1 air force in Asia that it proclaimed in the 1990s.

Although the JASDF will not be a strategic deterrent for China once it is equipped with the F-35A fighter, the addition of the plane will still have an effect on the Chinese air force and on its strategic anti-aircraft defense systems. The foremost threat it poses is its stealth capabilities, which represent a revolutionary upgrade from third-generation fighters and will shake up the early warning and sensor systems of air combat. The F-35A reduces the RCS of third-generation fighters from several dozen sq m to just one tenth to one hundredth of a sq m, which is enough to half the distance at which it can be detected by radar.

This puts pressure on Chinese early warning craft to increase their coverage to prevent the F-35A making use of blind spots. It also demands a much more concentrated deployment of anti-aircraft weapon systems or an upgrade to their anti-stealth capabilities. Chinese air force formations will also have to adjust their formations, as although the F-35 hasn’t substantially improved on the maneuverability of third-generation fighters, the F-35A has a tactical advantage over Chinese third-generation fighters, due to its ability to see the battlefield more clearly.

This means that the PLA Air Force will have to put fourth-generation J-20 fighters to the front of formations, in order to discover the F-35A fighters as soon as possible. These J-20 fighters can then intercept the F-35 fighters and push them out of Chinese airspace. Given the severe drop in RCS with fourth-generation fighters, adding concentrated deployment of early warning aircraft and radar is a bottomless pit, as no country has been able to make up for the shortfall in their early warning and anti-aircraft defense systems. The only effective means of dealing with this state of affairs is to develop a fourth-generation fighter with similar capabilities, posing an equal threat to the enemy.

China's newest warplane, the J-20 stealth fighter, made its first public flight at an airshow in the southern city of Zhuhai. It bears an uncanny resemblance to US military's F-22 Raptor

China’s newest warplane, the J-20 stealth fighter, made its first public flight at an airshow in the southern city of Zhuhai. It bears an uncanny resemblance to US military’s F-22 Raptor

The J-20 has already undergone several test-flights, suggesting that China’s fourth-generation fighter is almost complete and is on the brink of entering the manufacturing stage. After the final version of the plane is fixed and undergoes test-flights, manufacturing can begin, which means the J-20 will be deployed by 2017 at the earliest and by 2019 at the latest.

If the J-20 is manufactured at the rate of one regiment per year, then by 2025, 5-7 regiments will be equipped, with around 120-170 planes, which makes up around two air force divisions. The US only has 187 F-22 fighters. With China’s J-20 fighters in development, as well as the sheer numbers of third-generation fighters, forming its main strategic combat force, along with early warning aircraft, electromagnetic interference systems and airborne warning and control systems, China will have a clear advantage over Japan in any potential air battle.

If the J-20 is equipped with China’s fourth generation active electronically scanned array radar, and this equals the APG-77 with which the F-22 is equipped, the aircraft will be able to detect an F-35A head on at a distance of 50 km, whereas a F-35A will only be able to detect a J-20 head on at a distance of 20-40 km, giving the J-20 the advantage. The J-20 has similar capabilities to the F-22, including supercruise, electronic countermeasures (ECM) and supermaneuverability, giving it an advantage over the F-35A under all battle conditions.


Editors Note: Want China Times no longer publishes this kind of article.



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