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Tuesday, May 22, 2012

Threat Analysis of Foreign Stealth Fighters Part I: Chengdu J-20

In early 2011 China shocked the world by unveiling its first stealth aircraft, the Chengdu J-20. From publicly disclosed statements, it became evident that few individuals within U.S intelligence community thought that China would possess a stealth fighter this early in the decade. The debut of the J-20 came only a year after The Russian Federation publicly unveiled its own stealth fighter, the PAK FA T-50, for the first time. The unveiling of the J-20 and PAK FA T-50 speak volumes of the pace of technological advancement within their respective countries in relation to the United States. The United States can no longer take its head start and former monopoly on stealth aircraft for granted. This will be a two part article that will assess the capabilities and the U.S military policy ramifications of the J-20 and PAK FA.

Image 1: Artistic rendering of Chengdu J-20 destroying a Japanese F-2 fighter. Note how the J-20 in the illustration retains the data probe on the nose of the aircraft despite the fact that the aircraft shown is in service. Data probes are only featured on prototypes or test aircraft (Image credit: Chinese Military Review)

In terms of empirical facts, very little is actually known about the Chengdu J-20. Much of the publicly available information on the J-20 is not based on hard evidence. Endless speculation abounds on seemingly basic information: How did the Chinese develop a stealth aircraft so fast?  How stealthy is the J-20? What its intended role of the J-20 as an aircraft? How much of a threat does the J-20 actually pose for U.S fighter aircraft and installations as well as the fighter aircraft of neighboring countries?  This article will seek to answer these questions with FACTS and the very best estimates made by unbiased reputable aviation experts rather than the patriotic musings of Chinese internet fanboys.

Figure 2: Crew inspecting first J-20 prototype

How Did China Obtain a Stealth Fighter So Quickly? 

'Between legal, quasi-legal [diverted], and espionage-based tech transfer, I'm sure that China has obtained most of the data available on how we build our stealthy aircraft structures and the materials involved,' the intelligence official says. 'They also have taken full advantage of our open patent system, our open engineering undergrad and grad schools, our publish-or-perish academic promotion process, and the ease with which an integrated, centralized [government] can thwart artificial, social-democratic distinctions between military, police, civil and commercial data.'” - Anonymous intelligence official reporting to Aviation Week, 2012 

The exact origins of the J-20 are shrouded in secrecy. However, it is likely that at least some aspects of the J-20's design are the result of multiple attempts at reverse engineering U.S stealth technology. China's obsession with reverse engineering has an established historical precedent dating back to the origin of the nation itself. (see blog article: Made in China? A History of Reverse Engineering for examples) In 1999 during the NATO mission within Serbia, a single F-117 Nighthawk was shot down by a surface to air missile. Following the crash, Chinese agents were dispatched to recover parts from the wreckage. 

"At the time, our intelligence reports told of Chinese agents crisscrossing the region where the F-117 disintegrated, buying up parts of the plane from local farmers," - Croatian Adm. Davor Domazet-Loso

With one glance it becomes inherently obvious that the J-20 does not look like the Lockheed built F-117 Nighthawk. The two planes utilize a different method of incorporating stealth within the airframe. (REF. NOTE 1) However, the stealth coatings found on the wreckage of the F-117 would be invaluable in determining the composition of the highly classified RAM (radar absorbent material) coatings. Another source of information regarding stealth technology came from former Northrup Grumman engineer Noshir Gowadia. Gowadia provided information relating to his work on the B-2 Spirit stealth bomber and other classified projects to a host of foreign governments including: Israel, Germany, Switzerland, and China. (ABC News, 2006) Lastly, Lockheed Martin and even the Pentagon itself are the constant victim of highly organized and sophisticated Chinese hacking attempts. It is probable that information regarding American stealth technology was obtained through Chinese cyber attacks. For example, In 2009 information was released that indicated the Pentagon was attacked by hackers from China (Journal for Strategic Security, 2011) During 2007-2008 hackers stole information pertinent to the F-35 Lightening II, the future backbone of America's stealth arsenal. 

"The intruders appear to have been interested in data about the design of the plane, its performance statistics and its electronic systems, former officials said. The intruders compromised the system responsible for diagnosing a plane's maintenance problems during flight, according to officials familiar with the matter. However, the plane's most vital systems -- such as flight controls and sensors -- are physically isolated from the publicly accessible Internet, they said… The spies inserted technology that encrypts the data as it's being stolen; as a result, investigators can't tell exactly what data has been taken." - Wall Street Journal, 2009 

"In 2009, there was a forced electronic entry into the Joint Strike Fighter program and large amounts of data were copied.  According to present and former employees at the Pentagon, the attack can be traced to China. This could mean that it would be easy for China to defend itself  against the aircraft (which many western countries expect to acquire) and, assuming the attackers have acquired enough data, they may even be able to copy parts of it.  The American chief of counterintelligence has been reported as saying that "our networks are being mapped" with reference to American flight traffic control, and also as having warned about a situation in which "a fighter pilot can't trust his radar." - Journal of Strategic Security Volume IV Issue 2 2011

China constantly tests the envelope of what qualifies as Casus Belli, an act of war, through its repeated and invasive cyber attacks on the United States. In addition to obtaining information regarding U.S stealth technology, some analysts believe China was able to get information from the Russian Mikoyan 1.42/1.44 Multi Role Fighter (MFI) program. The Mikoyan 1.44 was designed to compete with the winner of the American Advanced Tactical Fighter competition, the YF-22. Although Russia claimed the 1.44 MFI could out preform the YF-22, virtually no foreign observers agreed with that assessment. The claim that the Mikoyan 1.44 was stealthier than the YF-22 was especially dubious.

"The conclusion which can be drawn is that the MFI may outperform the Eurocanards for RCS performance if radar absorbent materials are used generously, the nose chined, the fuselage wing interface and spine blended, and internal weapons carried. It will never be competitive with the edge aligned, faceted, and chined F-22A design (or the chined and blended YF-23 ATF demonstrator). The statements emanating from Russia clearly contradict the technically evident and have been described as a transparent marketing ploy, in the context of the somewhat byzantine post Soviet defence acquisition system." - Air Power Australia, 2005

Despite the MFI's shortcomings, the J-20 bears an uncanny resemblance to the abandoned MFI prototype. Adil Mukashev, an expert on Chinese-Russian ties, asserts that Russia likely sold MFI fighter parts to China. Sources within Russia suggest that China might have gotten access to key information on the MFI design. (The Guardian, 2011)

"It looks like they got access... to documents relating to the Mikoyan - the aircraft that the Ministry of Defense skipped over in its tender to create a stealth fighter" - Anonymous Russian source reporting to The Guardian, 2011

Although both aircraft share a number of design similarities such as the tail, there are important differences between the MFI and J-20. The chined nose employed on the J-20 is characteristic of the F-22A. The trapezoidal engine inlets are also "borrowed" from the F-22A and are utilized in conjunction to the enlarged Diverterless Supersonic Inlet features from the F-35. The flat lower fuselage is also remarkably similar to the F-22A design. (APA, 2011)

Image 3: Mikoyan 1.44 MFI aircraft on debut in 1998

Image 4: The first Chengdu J-20 undergoing flight testing

It is important not to dismiss the J-20 as purely the product of fruitful reverse engineering attempts. While China has no doubt at least obtained some elements or techniques used in the J-20's design from the United States and even Russia, China's ability to create new technological solutions has rapidly improved over the last few decades. Although China's domestic ability to innovate lags behind the United States and Russia, China continues to invest heavily in its science and engineering programs. The theory that China utilized at least some degree of reverse engineering helps answer how China was able to design a stealth fighter quicker than anyone expected.  

How Stealthy is the J-20? 

The hottest point of contention between aviation experts on the J-20 is how stealthy the airframe actually is. Official radar cross section (rcs) figures for the J-20 are impossible to find due to the fact that it is in China's best interest not to release such information. That said, a massive disparity exists between the different rcs estimates for J-20. On the high rcs side estimates, some argue that the J-20 features a merely reduced radar cross section similar to 4.5 generation fighters. Comparatively, some  argue that the J-20 design boasts a very low observable designation similar to the F-22A. In order to understand how stealthy the J-20 airframe is, a better understanding of stealth is required. An aircraft given a stealth designation means that the given airframe will reflect the vast majority of radar waves away from the source and hence has a low radar cross section. It gets more complicated when multiple bands or frequencies utilized in radars are factored into the equation. (e.g. I, J, H, X band radars, etc.) Calculating the rcs of an object is a very complicated and arduous process. 

"The radar cross section (RCS) of a target is defined as the effective area intercepting an amount of incident power which, when scattered isotropically, produces a level of reflected power at the radar equal to that from the target. RCS calculations require broad and extensive technical knowledge, thus many scientists and scholars find the subject challenging and intellectually motivating. This is a very complex field that defies simple explanation, and any short treatment is only a very rough approximation...The units of radar cross section are square meters; however, the radar cross section is NOT the same as the area of the target. Because of the wide range of amplitudes typically encountered on a target, RCS is frequently expressed in dBsm, or decibels relative to one square meter. The RCS is the projected area of a metal sphere that is large compared with the wavelength and that, if substituted for the object, would scatter identically the same power back to the radar." - Global Security, 2011

The radar cross section of an aircraft is different for each side of the airframe facing the radar source. In order to qualify as an all aspect stealth aircraft (e.g. F-22A, B-2) the airframe must not reflect radar waves from all sides of the airframe. The stealth designation is variable and does not mean all stealth aircraft have the same radar cross section. Here are some examples of aircraft and their frontal radar cross section figures and estimates. 

Estimates taken from Global Security (2011 and 2012) and Illinois State University (1997) 

Conventional and reduced radar cross section aircraft 
B-52 radar cross section = 40-50 m^2
B-1B radar cross section = 1m^2
F-15C radar cross section = 5m^2

Stealth aircraft 
B-2 Spirit radar cross section =  .01m^2 (mid range estimate, lowest rcs estimate .0001m^2)
F-35A radar cross section = .0013 m^2
F-22A radar cross section =  .0001 m^2 (-40 dBSM) 

Note: size has nothing to do with an rcs figure. The 51.4 ft long F-35 has an rcs 13 times larger than the highly refined 62ft long design of the F-22A. Yet, both aircraft qualify for the stealth designation. It is also worth noting that there are other components to stealth aside from an aircraft's radar signature. Stealth aircraft also have to reduce their include infrared (IR), radio frequency, and even visual signatures.

Image 5: This image highlights the extensive stealth features Incorporated within the J-20 design. (more details given below)

Now that a better definition of stealth has been provided, an analysis of the J-20's stealth potential can be given. First and foremost it should be noted that the J-20 design features canards. With the exception of the J-20, no verified full aspect stealth aircraft design features canards e.g. F-22A, YF-23, F-35, PAK FA. Russian and American Aerospace companies choose not to incorporate canards for a simple reason, they have terrible stealth characteristics. (Sweetman, 1997) Incorporating canards inherently limits the J-20's stealth qualities from a frontal aspect. Despite the fact that planform alignment is used in regards to the canards and extensive RAM coatings are no doubt utilized, it does not change the fact that canards yield terrible stealth results. Given the usage of the two techniques listed above, the poor rcs qualities of the canards will be mitigated but not completely eliminated. Thus, any estimates that claim the J-20 is stealthier or comparable to the F-22A can be outright eliminated.

Aside from the canards however, the J-20 design retains a stealthy frontal rcs. The design of the engine inlets,  chined  nose, flat lower fuselage, sawtooth design incorporation on internal bays, and extensive use of planform alignment should reduce the airframe's frontal radar signature considerably. It is hard to say if the J-20 design qualifies for the very low observable designation of -30 dBSM or lower because of its incorporation of canards. Dr. Carlo Kopp of the Australian based think tank, Air Power Australia, conducted a very thorough analysis of the J-20. He concluded that the J-20 qualifies as a very low observable aircraft. Other aviation experts such as Bill Sweetman are more reserved. Overall, the frontal aspect of the  J-20 design has a good chance of qualifying for low observable (-20 dBSM or .01m^2) designation. It is unlikely that it is any stealthier than -20 dBSM because of its incorporation of canards.

Although the frontal aspect of the J-20 qualifies as at least for the low observable designation, the rear of the aircraft is a completely different story. The engine nozzles are completely exposed to both radar and IR detection methods. True all aspect stealth aircraft such as the F-22A shield the rear of the aircraft from detection. Unless the J-20 wants an AIM-9X shot strait up its tail pipe, China better remedy this problem.

Image 6: Rear of J-20. Note the exposed engine nozzles.

Image 7: Rear of F-22A Raptor. Note the protected 2-D thrust vectoring nozzles that both reduce the raptor's rear rcs signature as well as its IR signature.

Because the current J-20 in flight testing is likely a prototype, it is possible that the airframe will undergo numerous design changes. For example, the YF-22 went through numerous design alterations to become the F-22A. It is possible that the rear of the J-20 will be better protected on the final production version of the J-20.  Sawthooth engine nozzles will better protect the J-20 from enemy radars from the rear aspect but will not provide the same level of protection as the 2-D nozzles mounted on the F-22A.

The biggest uncertainty about the design concerns the engine exhausts, which as seen on the prototype are likely to cause a radar cross-section (RCS) peak from the rear aspect. One possibility is that a stealthier two-dimensional nozzle will be integrated later in the program:  however, the nozzles on the current aircraft show some signs of RCS-reducing saw-tooth treatment, suggesting that the PLA has accepted a rear-aspect RCS penalty rather than the much greater weight and complexity of 2-D nozzles.” - Bill Sweetman and David Fulghum, 2011 

"The rear-aspect view of the aircraft is not as stealthy, a feature also seen on the Sukhoi T-50. This is clearly an intentional trade, eliminating the heavy 2D nozzles of the F-22. In this respect, both the T-50 and J-20 reflect the philosophy behind the pre-1986 Advanced Tactical Fighter studies that preceded the F-22, based on the theory that a fast, high-flying, agile aircraft is relatively immune from rear-quarter attacks." - Bill Sweetman, 2012

What its intended role of the J-20 as an aircraft? 

The most mysterious questions regarding the J-20 is what is its purpose? China has not provided an answer as to what the J-20's intended role is. The most compelling theory as to what the role of the J-20 will be is provided by Dr. Kopp. Kopp believes that the J-20 will act as a theatre range strike bomber similar to the proposed FB-22 while maintaining the ability to dogfight. The J-20 is an extremely large aircraft relative to other 5th generation fighters. No official spesifications have been released but estimates suggest the aircraft is nearly 70 feet long. (Some estimates put the J-20 at 75 feet long)

"The J-20 is a single-seat, twin-engine aircraft, bigger and heavier than the Sukhoi T-50 and the F-22... which would suggest a takeoff weight in the 75,000-80,000-lb. class with no external load. That in turn implies a generous internal fuel capacity. The overall length is close to that of the 1960s General Dynamics F-111, which carries 34,000 lb. of fuel." -Global Security 2011

Image 9: With such a large supply of internal fuel, the J-20 could have an unrefueled range of 1,000-1,500 nautical miles. If the J-20 features supercruise, in addition to its high fuel capacity, its combat radius will be extensive. According to the DOD, in a war with the United States, China would likely seek to maintain control over areas up to the second island chain shown on the map. An extended range stealth strike aircraft like the J-20 would fit well into this role. The J-20 would penetrate U.S integrated air defense systems (IADS) and hit U.S installations using its stealthy frontal rcs.  (Image credit: Air Power Australia, Kopp, 2011)

Although the J-20 will likely preform bombing missions, it retains the ability to dogfight. The J-20's incorporation of canards suggests that maneuverability was a key requirement of the design. Although canards will damage the J-20's stealth prospects as mentioned earlier, the J-20 will have excellent angle of attack capabilities and turning abilities because of the incorporation of canards.

How much of a threat does the J-20 actually pose for the United States and its allies? 

With the J-20 likely to enter service between 2017-2019, the United States must be prepared. Before possible and active U.S responses are analyzed its worth mentioning several key potential problems Chengdu is likely to face in the development of the J-20. First an foremost the biggest concern with the J-20 lies in its engines, the Russian designed AL-31F. The AL-31F was designed for use in the Su-27. China has struggled to domestically produce capable jet engines for its growing fighter fleet and heavily relies on Russian exports. The second prototype currently undergoing flight testing, the 2002 aircraft, is said to feature the domestically produced WS-10 which is a copy of the AL-31F. Its unclear if the WS-10 is capable of super cruise or produces enough thrust to keep the large J-20 airframe maneuverable. What is clear is that the WS-10 has experienced numerous performance issues. (Axe, 2011)  

Another key problem with the J-20 and Chinese fighters in general lies in the lack of capable avionics. Chinese built avionic systems are woefully far behind their American and Russian counterparts. Its unclear if the Chinese have actually been able to produce a capable active scanned electronic array (AESA) radar. The domestically produced J-10 features a mechanically scanned radar comparable to U.S fighter radars used in the early 1990s. (Sinodefense, 2009). For example, the radar used in the J-10 can track 10 targets while engaging 4 targets vs the F-15's AN/APG-63 (V) 1 radar built in the 1990s can track 14 and engage 6) Although stealth is the primary qualifier for the designation of a 5th generation fighter, other important qualifiers such as avionics matter. Without a capable AESA radar system, sensor fusion, or and HMD the J-20 will not be able to fullly capitalize on its stealth design. With those limitations in mind, a threat analysis of the J-20 will follow. 

U.S Military Recommendation I: Harden Pacific Airbases 

With a stealthy frontal rcs of around -20 dBSM (.01m^2), the J-20 will likely be able to avoid detection long enough for it to come into weapons range of U.S bases. Given its range and considerable payload capacity, the J-20 could pose a major threat to U.S airbases. If the J-20 is outfitted with long range low observable air to surface missiles the J-20 could pose an even greater security risk.  At the moment, few U.S airbases within the area are hardened (with the exception of Kadena AFB which has limited protection of 30 hardened aircraft shelters). This means that U.S airbases are vulnerable to attack if U.S fighters on patrol fail to intercept an incoming J-20 strike force. The largest U.S airbase in the Pacific region, Anderson AFB, is particularly noteworthy. Anderson AFB is barren in terms of hardened aircraft shelters and runways. Although it's more than 1,500 nautical miles from China, it is no longer safe from attack due to the extended range of the J-20. If flight operations are no longer possible from Anderson AFB, any war effort with China would be severely crippled from the U.S perspective. Due to its poor rear stealth characteristics, the J-20 might be open to reprisal after striking U.S bases but by that point the damage has already been done. 

The United States MUST harden the runways and install hardened aircraft shelters on all of its airbases within the Pacific region: Osan (SK), Kunsan (SK), Misawa (Japan), Yokota (Japan), Iwakuni (Japan), Kadena (Japan), and Anderson (Guam). Hardening U.S airbases in the region would not only mitigate the damage from a J-20 strike force, but also it would make U.S airbases more resistant to the hundreds of medium range and theatre range ballistic missiles China is deploying in the region. GPS jamming equipment is also suggested to deny usage of China's GPS system as to reduce the effectiveness of Chinese GPS precision guided munitions

Image 10: B-2 Spirit escorted by F-22A raptors from Anderson AFB Guam 

U.S Military Recommendation II: Improve IADS systems in Pacific Region

The United States must continue to upgrade and deploy Patriot missile batteries and other capable surface to air missiles in the Pacific region to protect its land based assets. Upgrades to enhance the Patriot PAC-2 system's effectiveness towards low observable targets are already underway with the GEM-T upgrades (Raytheon, 2011). Further upgrades to assist in the targeting of low observable aircraft should be considered for the PAC-2 system. PAC-3 Patriot batteries should be deployed in conjunction with the upgraded PAC-2 systems to protect U.S Pacific airbases from Chinese deployed medium range ballistic missiles.

Image 11: The MIM-104 Patriot PAC-2 is the principle surface to air missile system of choice for several western nations. Over the years the Patriot has undergone several upgrades and modifications to keep the system relevant and increase its lethality. Current PAC-2 Patriot missiles have a range of 160 km (100 miles). However, keep in mind the J-20 has a lower frontal rcs, its unlikely that the PAC-2 would be able to detect and engage the J-20 until it was a great deal closer e.g. ~30-40 miles out. The system would have a better chance in shooting down a J-20 once its rear faces the Patriot's radar array. (Image Credit: Global Security)

U.S Military Recommendation III: Deploy more Raptors to the Pacific 

Image 12: The most lethal fighter aircraft ever produced, the Lockheed F-22A Raptor.

Arguably the best defense against the Chengdu J-20 is the Lockheed F-22A Raptor. From what we know of the J-20 in terms of its stealth capabilities, avionics, engine troubles, available surface to air munitions, and Chinese pilot training programs, using the technical term, the J-20 is "toast" against the Raptor. It is also worth noting that only the very best USAF pilots are selected to fly F-22A. In every category comparable, the Raptor exceeds the J-20. [Onboard oxegen generating (OBGS) issues aside of course; OBGS problems should be remedied upon the installation of back-up onboard oxygen generating systems. The entire F-22A fleet will be upgraded with the new system by 2014 at the cost of $44 million USD] - Daily Press, 2012

Currently the United States operates 184 Lockheed F-22A Raptors in active duty. A sizable portion of America's available Raptors should be permanently based in the Pacific region. From time to time Raptors train at Kadena AFB and Anderson AFB but arrangements should be made to increase the number of permanently stationed Raptors in the Pacific. I believe the 36th Operations group based at Anderson AFB fly's Raptor's but I'm not entirely certain. Raptors should be given priority for the proposed hardened aircraft shelters due to their high unit cost and low numbers.

Despite the Raptor's remarkable abilities, the USAF only has 184 Raptors and production of the Raptor has ended. Until the political motivation and financial situation changes, the U.S military will have to make due with what it has already procured. That means ingratiating and improving current 4th generation platforms such as the F-15C and F-16C into operation with 5th generation aircraft e.g. F-22A. Arrangements to upgrade the F-15C and F-15E are already underway with the installation of the new APG-63 (V) 4 radars. Because of its usage of planform alignment, the Raptor has a finite space available in its nose cone for radar upgrades. (Axe, 2012) The non-stealthy F-15C and F-15E is favorable to the F-22A in upgrade mod-ability. These new and improved F-15C's and F-15E's will work in teams with the stealthier F-22A to secure U.S interests in the region.

As currently envisioned, the F-15s would fly with extra fuel tanks and AMRAAM missiles and with radars blaring, while the F-22s, carrying less gas and fewer missiles, would turn off their radar and sneak up on the enemy for ninja-style jabs. 'Our objective is to fly in front with the F-22s, and have the persistence to stay there while the [F-22s] are conducting their [low-observable] attack,' Maj. Todd Giggy, an F-15 pilot, told  ." - Axe, 2012

Note: The reason the Raptors would turn off their radars is to insure that they cannot be jammed and tracked by enemy planes. Even with low probability intercept modes featured on the AN/APG-77 AESA radar (utilized by the Raptor), it does not provide complete protection from jamming and detection. By utilizing this innovative method, Raptor pilots can take full advantage of the stealthiness of the F-22A airframe and remain completely undetectable while F-15E and F-15C pilots with upgraded radars provide targeting information for the Raptors.

Image 13: F-15E flying in formation with F-22A at Anderson AFB.

Military Recommendation to U.S Allies: Purchase the F-35

Image 14: F-35A roll out ceremony at Eglin AFB Flordia. (Image Credit: Samuel King Jr, retrieved from Defense Media Network 2012) 

The United States Government has banned the possibly of exporting the F-22A Raptor. The next best aircraft available to U.S allies is the F-35 Lightning II. Despite the whole host of problems Lockheed is experiencing in the development of the jet, F-35 remains the best bet for U.S allies. Japan has already announced that it plans to acquire 42 F-35A's in its F-X competition. Japan might seek to order more than 100 F-35's if the jet wins its J-XX competition to replace Japan's aging fleet of F-15J's. In terms of standing on even footing with the J-20, no other aircraft currently in the competition even comes close to the F-35A. Given what we know about the J-20, a full production J-20 would likely make short work of 4 and 4.5 generation fighters without the aid of 5th generation fighters. A dogfight between the F-35 and the J-20 would be closer than a dogfight between the F-22A and the J-20. However, the F-35 is still stealthier and features better avionics and sensors than the J-20. Though it is likely less maneuverable than the J-20 (assuming China gets a capable engine for the J-20). It would be prudent of South Korea to order the F-35 for its F-X phase 3 competition. If the F-35A won, South Korea would likely order dozens of jets to supplement its F-15K "Slam Eagles" (upgraded derivative of F-15E Strike Eagle).

In conclusion, the United States and its allies should not fear the deployment of the J-20 a great deal. If the proposed U.S Military recommendations are put into effect,  the United States and its allies will be in a good position to deny Beijing  air control over the Pacific region.

RELATED READING: Threat Analysis of Foreign Stealth Fighters Part II: Sukohi PAK FA 




Note 1: The F-117 utilized first generation stealth technology composed of flat geometrically arranged panels to deflect radar waves. This method was effective in reducing the F-117's radar signature but resulted in an aerodynamically unstable airframe. The J-20 utilizes the planform alignment method of reducing an aircraft's radar signature.  Planform alignment is a more advanced method of stealth technology that allows one to construct an aerodynamically feasible airframe while deflecting radar waves. Planform alignment is achieved through arranging the flight surfaces of the aircraft in such a way that they have identical angles that reflect incoming radar waves away from the source. This technique was pioneered on the YF-22 and YF-23 designs in the Advanced Tactical Fighter competition of the 1990s. 

Image 15: F-35A with F-22A flying behind. The USAF plans to acquire a total of 1,763 F-35A aircraft to supplement its force of 187 F-22A Raptors. The USAF will maintain the largest fleet of highly capable 5th generation aircraft in the world even if a few hundred F-35A's are cancelled due to budget cuts. (Image Credit: Darin Russel, retrieved from Defense Media Network 2012)


  1. Great article. Very informative!

  2. Excellent article.

  3. I would say J-20 design probably got more lineage from this design than the Mig 1.44.

    LM came to this canard design after their work with F-22, so I would say that "poor rcs qualities of the canards" is probably overstated. Is there any actual study that prove it does do worst than just one writer(Sweetman)'s claim?

    1. I was aware LM did some work on a canard F-35 concept, but I was not aware any credible images existed. What is the source? As for canards and RCS, I think it would still disrupt the planform alignment if its consistently moving thereby mitigating at least some degree of its low rcs. But I'm not a physicist, if LM says its good it probably is.