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Last Updated: Mon Jan 27 11:18:09 UTC 2014






The Chengdu J-20: Peace in Our Time?
Air Power Australia - Australia's Independent Defence Think Tank

Air Power Australia NOTAM
  4th July, 2011


WGCDR Chris Mills, AM, BSc, MSc(AFIT), RAAF (Retd)

Peter Goon, BEng (Mech), FTE (USNTPS),
Head of Test and Evaluation, Air Power Australia

© 2011 C.L. Mills, P.A. Goon
Contacts: Peter Goon
Carlo Kopp

Mob: 0419-806-476 Mob: 0437-478-224


Near head on view of J-20 prototype showing the trapezoidal edge aligned inlet geometry , wing/fuselage join, and flat lower fuselage (Chinese Internet).

One of the strategic arts of maintaining National Security is to accurately forecast the future and assess the potential for credible threats to emerge. When he was Director of the CIA, former Defense Secretary Robert Gates claimed he had this nailed:

Gates also noted a lesson from his years as deputy national security adviser, deputy director of the C.I.A and director of central intelligence during the presidencies of Ronald Reagan and George H. W. Bush. “I learned to ask the question, What’s Chapter 2?” he said. “If we do this, what will they do? Then what? Then what? Try to think two, three, four moves out.”

Washington Times, ‘The Professional’, 10 February 2008

 In light of the Hon Robert Gate’s reliance on the term “Next War-itis” to focus the Pentagon’s political capital on the war-on-terror, this posture shows some dangerous hubris – the underlying assumption is that the USA “calls the shots”, while the rest of the world responds. What if the truth is the converse?

Deftly assisted by Western myopia on near term profitability, China now has an economy that will soon surpass that of the USA in size and capacity to afford ‘discretionary’ investments in overseas aid to garner support, and military capabilities to protect China’s national interests on a global scale. Much is written on the rise of the Chinese Dragon and the demise of the US Eagle. While many claim the US is still in the lead, the trend lines are clearly pointing to an intersection in the very near future where economic and military capability superiorities will reverse.

The Chengdu J-20 prototype is a case-in-point. China has invested substantial amounts of Yuan in this project, which is at the pinnacle of the modernisation of the People's Liberation Army in general, and their air power capabilities in particular.

The aircraft was not made on the whim of a PLAAF General, nor because Chengdu decided that it could make a nice fat ponzi-profit from the sales. This is an aircraft designed with strategic intent in mind. A large, long range, agile aircraft with a substantial internal weapons capacity, it has the potential to project power, not only from China’s shore, but deployed globally. To be successful in locations where powerful sensors are scarce and its main opponent is likely to be counter-air aircraft such as the F-22A, it must have ‘Low Observability’, especially in the forward sector, when it sweeps into an attack.

So, have the Chinese succeeded in meeting these design criteria? The analysis by Dr Michael Pelosi and Dr Carlo Kopp, ‘A Preliminary Assessment of the Specular Radar Cross Section Performance in the Chengdu J-20 Prototype’, examines the observability of the aircraft across a broad range of frequencies, and from all aspects.

By applying the Laws of Physics to this question, they can state some hard facts, rather than opinion, regarding the ‘Observability’ of the aircraft.

Before discussing the facts, here is a cross-section of the opinion that emerged after the aircraft first flew, publicly, on 11 January 2011:
Robert Gates: (Defense News, 19th January, 2011, ‘Gates Clarifies China’s Stealth Capabilities’)

Gates said Saturday. “What I said was that in 2020 or 2025 that there would still be a vast disparity in the number of deployed fifth-generation aircraft that the United States had compared to anybody else in the world. And I continue to stand by that statement.”

“We’ve been watching these developments all along,” Gates told reporters aboard his plane, which arrived in Beijing on Sunday. “I’ve been concerned about the development of the anti-ship cruise and ballistic missiles ever since I took this job. We knew they were working on a stealth aircraft.

“I think that what we’ve seen is that they may be somewhat further ahead in the development of that aircraft than our intelligence had earlier predicted.”

Geoff Morrell: (China Military News, 27th January, 2011, cited from bloomberg.com and written by Tony Capaccio)

The U.S. Defense Department is reserving judgment on the capabilities of China's new J-20 fighter jet, spokesman Geoff Morrell said today.

Public reports are only speculation when they assert that the Chinese fighter has cutting-edge "fifth-generation" stealth technologies -- such as advanced sensors, avionics and communications gear -- like those used in Lockheed Martin Corp.'s F-22 and F-35 jets, he said.

Dr Loren Thompson: (Lexington Institute – Early Warning Blog, Wednesday, 2nd March, 2011)

Although the J-20 resembles the outline of the stealthy F-22 Raptor when viewed head-on in its forward aspect, the plane clearly lacks many of the features that make Raptor the most capable air-to-air combat system in history.

Early reports that the J-20 exceeds 70 feet in length appear to be wrong.

While the J-20 superficially resembles fifth-generation fighters such as the F-22 and F-35, experts do not believe Chinese designers will be able to produce an airframe that comes close to matching the manoeuvrability, survivability, lethality or situational awareness of an F-22 or F-35.

F-35 Lightning II Program Website (accessed 30th June, 2011, http://www.jsf.mil/f35/f35_technology.htm):

Low Observability - An integrated airframe design, advanced materials and an axisymmetric nozzle maximize the F-35's stealth features.

Richard Aboulafia: (Washington Wire Blogs, 19th January, 2011, China’s J-20 Fighter: Stealthy or Just Stealthy-Looking?)

In an interview with The Wall Street Journal, Richard Aboulafia, an aviation analyst with the Teal Group, an aerospace and defense consulting firm, said China is still years away from perfecting stealth aircraft.

“It’s certainly stealthy-looking,” Mr. Aboulafia said. It looks like it’s got some of the faceting and some of the shaping that characterizes the front of the F-22, for example.

“But then you look the details and you realize this thing is just sort of cobbled together,” he added.

Take, for instance, the canard: forewings close to the nose of the aircraft that provide maneuverability. According to Mr. Aboulafia, “There’s no better way of guaranteeing a radar reflection and compromise of stealth” than adding canards to the aircraft.

“It’s quite possible that in 10 years they have a functioning equivalent of the F-22, but by then, the West will have moved on to something far more impressive,” he said.
Let’s put these august pontifications through the prism of the software simulator running the ‘Physical Optics’ specular reflection model of the J-20. Readers are encouraged to access and digest this analysis, but for the busy, here is the abstract verbatim:
This study has explored the specular Radar Cross Section of the Chengdu J-20 prototype aircraft shaping design.

Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe.

In addition, the performance of a range of Chinese developed radar absorbers was modelled, based on a reasonable survey of unclassified Chinese research publications in the area.

None of the surveyed materials were found to be suitable for use as impedance matched specular radar absorbers.

Modelling has determined, that if the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector.

Conversely, if the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for  robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector.

This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.


Above: L-band RCS, below X-band RCS head on, both in PCSR format (M.J. Pelosi).

Engineers and Scientists who work in ‘stealth’ (AKA ‘Low Observable’) designs have a way for explaining it to lay people: ‘Stealth’ is achieved by Shaping, Shaping, Shaping and Materials (Denys Overholser).

The F-22A is clearly well shaped for low observability above about 500 MHz, and from all important aspects. The J-20 has observed the ‘Shaping, Shaping, Shaping’ imperative, except for the axisymmetric nozzles, and some curvature of the sides that smears a strong, but very narrow specular return into something of a more observable fan. The X-35 mostly observed the ‘Shaping, Shaping, Shaping’ rule, but since then, to quote a colleague, ‘hideous lumps, bumps, humps and warts’ have appeared on the JSF to disrupt the shaping imperative, forcing excessive reliance on materials, which are at the rear-end of the path to ‘Low Observability’.

While discussing ‘rear-ends’, both the F-35 and the J-20 have large signature contributions from their jet nozzles. However, the difference is much like the proverbial ‘Ham Omelette’: the F-35 Pig is committed, but the J-20 Chicken is a participant. If the Chinese decide that rear sector Low Observability is tactically and strategically important, they are at the design stage where they can copy the F-22A nozzle design for the production configuration of the J-20.

In a market now dominated by “a total indifference to what is real”, no such option is now or ever was possible for the JSF, as its design is based upon meeting the bare minimum (a.k.a. “Threshold”) requirements of the JORD wherein “excellence is the enemy of good enough”; as has the STOVL F-35B as the baseline design; and, thus, is heavily constrained by the specified roles for this aircraft as well as the risks to reputations based political imperatives of accelerating a much-delayed and grossly over-budget program.

The issue of the use of materials to suppress radar signature is interesting. Publications show that the Chinese are making a substantial investment in use of materials to reduce radar signature and have produced large volumes of research results. So far, there have been no Chinese public disclosures on materials that make a substantial reduction of signatures across a broad range of air combat radar frequencies. Come to think of it, there are no United States research papers on the subject. Why is that, one wonders?

Let’s revisit the opinions expressed about the J-20 soon after its maiden flight.

Robert Gates: (Defense News, 19 January 2011, ‘Gates Clarifies China’s Stealth Capabilities’)

Gates said Saturday. “What I said was that in 2020 or 2025 that there would still be a vast disparity in the number of deployed fifth-generation aircraft that the United States had compared to anybody else in the world. And I continue to stand by that statement.”
This could be true. What Robert Gates did not say was whether the disparity in numbers would be on the Chinese or the US side. Air Power Australia’s analyses suggest that the 2,457 US F-35s will lack sufficient ‘Low Observability’ to qualify for genuine  ‘Stealth Status’. If the J-20 designers clean up the signature from the nozzles and other “hot spot” returns with  good materials, it could be in the F-22A class. In that case, the actual situation might be 187 (less attrition) Raptors vs the J-20 production run of perhaps 500 plus. This IS a ‘vast disparity’ of numbers.
“We’ve been watching these developments all along,” Gates told reporters aboard his plane, which arrived in Beijing on Sunday. “I’ve been concerned about the development of the anti-ship cruise and ballistic missiles ever since I took this job. We knew they were working on a stealth aircraft.”

“I think that what we’ve seen is that they may be somewhat further ahead in the development of that aircraft than our intelligence had earlier predicted.”
Another ‘Capability Surprise’ admitted by the former Director of the CIA.
Geoff Morrell: (China Military News 27th January, 2011, cited from bloomberg.com and written by Tony Capaccio)

The U.S. Defense Department is reserving judgment on the capabilities of China's new J-20 fighter jet, spokesman Geoff Morrell said today.

Public reports are only speculation when they assert that the Chinese fighter has cutting-edge "fifth-generation" stealth technologies -- such as advanced sensors, avionics and communications gear -- like those used in Lockheed Martin Corp.'s F-22 and F-35 jets, he said.
Air Power Australia’s analysis indicates that the US Department of Defence no longer need speculate on the specular returns of the J-20. The forward sector will be ‘Low Observable’ and development work on the aircraft could expand the ‘Low Observable’ angular aspects considerably.

The F-35 has some ostensibly spectacular avionics although a sceptical observer might note that the avionics are largely ten-year-old tech, but only if it can meet the required level of quality assurance requirement in delivering millions of lines of ‘bug free’ software. Shame about the ‘Low Observability’ from aspects apart from a few degrees around the nose.
Dr Loren Thompson: (Lexington Institute – Early Warning Blog, Wednesday, March 02, 2011)

Although the J-20 resembles the outline of the stealthy F-22 Raptor when viewed head-on in its forward aspect, the plane clearly lacks many of the features that make Raptor the most capable air-to-air combat system in history.

Early reports that the J-20 exceeds 70 feet in length appear to be wrong.

While the J-20 superficially resembles fifth-generation fighters such as the F-22 and F-35, experts do not believe Chinese designers will be able to produce an airframe that comes close to matching the maneuverability, survivability, lethality or situational awareness of an F-22 or F-35.
Dr Loren Thompson’s now very public underestimation of the actual size of the Chengdu J-20 aircraft is only eclipsed by his continuing failure to ignore the self evident truth arising from the similarities in the cardinal performance capabilities of the Chengdu J-20, F-22A Raptor and the Sukhoi T-50 PAK FA, namely: twin engine performance, highly disciplined low observables design, supercruise, Mach 2 category speeds, high to extreme agility, stratospheric cruise and loiter capabilities and overall large size with incumbent growth margins. The relative shortcomings of the F-35 now place the obsolete JSF in a generational limbo. With the tried and proven US Naval Test Pilot School truism of “systems do not a fighter aircraft make” ringing loudly for all to hear, no amount of ‘avionic systems’ and software can make up for less than capable aero-systems and aero-propulsive design.
F-35 Lightning II Program Website (accessed 30th June 2011) http://www.jsf.mil/f35/f35_technology.htm):
Low Observability - An integrated airframe design, advanced materials and an axisymmetric nozzle maximize the F-35's stealth features.

 As the Air Power Australia analysis clearly demonstrates, axisymmetric nozzles are not the way to “maximise .....stealth features”. Readers should not be misled by the chevrons on the nozzle tail-feathers derived from 1980’s research into mixing jet exhaust plumes for reducing aircraft noise. Air Power Australia has previously demonstrated the strength of returns from axisymmetric nozzles with ‘serrated’ edges in these works:

http://www.ausairpower.net/APA-NOTAM-070109-1.html

http://www.ausairpower.net/APA-2009-01-Annex.html#mozTocId787784
Richard Aboulafia: (Washington Wire Blogs, 19th January 2011, China’s J-20 Fighter: Stealthy or Just Stealthy-Looking?)

In an interview with The Wall Street Journal, Richard Aboulafia, an aviation analyst with the Teal Group, an aerospace and defense consulting firm, said China is still “years” away from perfecting stealth aircraft.
This could be correct. The use of ‘years’ is technically true for any number larger than one.
“It’s certainly stealthy-looking,” Mr. Aboulafia said. It looks like it’s got some of the faceting and some of the shaping that characterizes the front of the F-22, for example.

“But then you look the details and you realize this thing is just sort of cobbled together,” he added.
Seems like the Cobbler knows his craft. The Air Power Australia modeling shows some very credible ‘Low Observability’ results.
Take, for instance, the canard: forewings close to the nose of the aircraft that provide maneuverability. According to Mr. Aboulafia, “There’s no better way of guaranteeing a radar reflection and compromise of stealth” than adding canards to the aircraft.
What is the difference between an elevator and a canard, apart from the location on the aircraft? Each has a leading edge, a trailing edge, and a tip alignment, so as long as the rules of alignment are observed, there should be no difference. The Air Power Australia simulations do show specular returns from geometric alignments, as is common with all ‘stealth’ aircraft. These are tactically managed with flight-path directional control.
“It’s quite possible that in 10 years they have a functioning equivalent of the F-22, but by then, the West will have moved on to something far more impressive,” he said.
Hmmmn, run that by me again. Developing a new aircraft type in the USA now seems to take up to three decades. What research and development programmes have been funded to produce the (say) competitive X-60 / X-61 replacement for the F-22A and the F-35? And will the debt-laden USA be able to afford the hundreds of billions of dollars needed to develop a competitive new air combat aircraft?

 The pronouncements that China will require until 2020-2025 to produce a competitor to the F-22A seem to have the same hollow ring of Neville Chamberlain’s ‘Peace in our Time’ pronouncement, spoken on the 30th September, 1938.

 IMINT confirms there were two (2) J-20 full scale test articles involved in the public theatre during the Hon Robert Gate’s visit to China in January last – one undertaking the high speed taxi “trials” while the other performed the first “public” flight.

The timing of such theatre, level of completeness of the two test articles and the fact that first flights usually follow high speed taxi work on the same test aircraft were clearly as much for the benefit of the Chinese people as for Western observers, and go a long way to support closed-source information that some analysts have been contemplating for a while; namely:
  • the Chengdu J-20 design has been flying for some time, likely since circa 2006;
  • a number of full scale test articles (>4) have been built and flown;
  • the level of completeness of the two aircraft ‘displayed’ in early 2011 suggests these examples of the J-20 are beyond proof-of-concept and developmental prototypes; likely early pre-production prototypes; and,
  • given the significance of 2010 in terms of regional and global air power planning, waiting till 2011 to introduce the world to the Chengdu J-20 showed, at the very least, consideration for not wanting to upset or interrupt the plans of others - a most ‘Napoleonic’ of gestures befitting a carefully considered and inscrutable strategy to “never disturb your enemy when he is making a mistake”.
Air Power Australia’s application of the Laws of Physics to the J-20 Physical Optic simulation analysis produces facts. Opinions that ignore the facts produce hubristic [Hubristic: Overbearing pride or presumption; arrogance] statements.

 To conclude, here is a very perceptive quotation from McGeorge “Mac” Bundy, National Security Advisor to the Kennedy and Johnson administrations:

“There is no safety in unlimited technological hubris”.
Air Power Australia Website - http://www.ausairpower.net/
Air Power Australia Research and Analysis - http://www.ausairpower.net/research.html






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