SEPTEMBER 24, 2016
Nate “Buster” Jaros says China will have a fifth generation fighter, and its development of the J-20 (amongst other fifth gen platforms) is significant.
If you haven’t been paying much attention to the jet fighter news lately, you may have missed something big. In fact, it doesn’t get a lot of press and over the past couple of years this new emerging threat really hasn’t been on anyone’s, ahem…radar, much at all.
We’re talking about the Chinese Chengdu J-20. What some are calling “the Chinese F-22 Raptor.” Also known in some circles as the “Black Eagle.”
The J-20 is still shrouded in secrecy, and the political closed doors of modern China are not saying much either. I don’t blame them. They are catching up in technology, and in this case fighter technology, and are committed to not being left behind. China will have a fifth generation fighter, and its development of the J-20 (amongst other fifth gen platforms) is significant.
Let’s take a closer look at the J-20, based on what little information is out there today.
At first glance the J-20 looks kind of like an F-22 Raptor. Why wouldn’t it? The Chinese have beencopying Russian and American technology for decades. In some cases they have even improved on the designs. In the case of the J-20, you may have forgotten that a few years ago, terabytes of classified US documents were lost or stolen by the Chinese. These documents were essentially the “blueprints” for the F-35, and U.S. stealth technology. From that breach, it is surmised that China has been able to piece together the basic tenets of stealth technology and apply them to its modern aircraft designs.
Basics
What we currently know about the J-20 is that it is a single seat, twin engine, canard/delta design, stealthy fighter platform. There are just four copies being tested right now, with fully operational fighters predicted to be ready by 2018.
The Black Eagle has two Saturn AL-31 engines producing about 30,000 lbs of thrust each. With the possibility of more powerful Xian WS-15 engines currently in development, those are speculated to produce 44,000 lbs of thrust each. For reference, the F-22 has roughly 35,000 lbs of thrust per engine.
The Black Eagle is big. It weighs an estimated 43,000 lbs empty / 80,000 lbs MTOW (Max Takeoff Weight). The Raptor weighs in at 43,000 lbs empty / 83,000 lbs MTOW. Personally, I believe that the J-20 will be a bit heavier than this, just based on size alone. These internet procured weight estimates seem a bit light to my best guesses. Here’s why.
Another interesting fighter size comparison chart.
Recall that the Chinese Chengdu J-10, which looks very much like a Eurofighter Typhoon, is actually more comparable in all aspects to the F-16 Viper. The J-10 is within inches of the F-16’s dimensions, yet the J-10 weighs over 3,000 lbs more when empty. The old Russian SU-24 Fencer was almost identical to the F-111 ‘Vark, yet it weighed nearly double the average ‘Vark’s weight. Despite their best efforts, foreign airplane makers just don’t focus on weight savings as much as US manufacturers do.
The J-20 is 67 feet long and has a 44 wingspan. The Raptor, is 62 feet long and sports an identical 44 foot wingspan. Based on size alone, there is no way a J-20 weighs the same as an F-22. The weight estimates above must be light.
Consider that, plus historical facts and now add an additional five feet of airplane in the J-20 Black Eagle over a Raptor, and you’ve got one large turkey. Remember that for later.
J-20 and F-22 length comparison.
It is predicted that the J-20 will carry four to six long range missiles and possibly two short range heat-seeking missiles as well, all inside internal bays. Very ‘Raptor-like.’ The F-22 carries six long range missiles and two heat-seeking missiles, and air-to-ground options too. The Raptor also has a gun, the J-20 does not…we think.
The J-20 shows off it’s weapons bay.
Additionally, the Raptor carries 18,000 lbs of fuel (internal). The J-20 is touted as being able to carry 25,000 lbs of fuel internally, and that’s a lot of dinosaurs. Remember the size differences we talked about? You’ve got to be able to put that fuel somewhere on board.
Stealth
The J-20 is a LO (Low Observable) design. Using outside assessments and making a few of my own predictions from what little is out there on the J-20, most agree that the J-20 is “medium” stealthy in the mid to higher frequencies (acquisition and fire control radars mostly) and from front aspects only.
Most of an object’s “stealthy-ness” comes from shaping alone. No amount of RAM (Radar Absorbent Material) can undo a poorly shaped object, it must be designed and built from the ground up with stealth in mind. RAM comes later when designers want to clean up hot spots around various nacelles, apertures, and openings on the aircraft.
Chinese J-20. Note the Raptor like appearance and intake designs.
From what I can see (and read) the J-20 is shaped about as well as can be expected for a fighter aircraft (go figure, it looks like a Raptor, which was heavily tested and tweaked for LO considerations). Front hemisphere designs appear to be in accordance with standard radar laws, with parallel lines, and minimum rough or flat edges. The J-20 uses angled chines along the sides of the aircraft (like the F-22), and a hidden engine intake design both to help lower side-section and front aspect RCS (Radar Cross Section).
Of course, a close-up examination of the J-20 will decide if the Chinese LO craftsmanship is up to par with Western standards. However, no one has been permitted to get up close to one yet. Simple things like blemishes, roughly fit skin panels, screw heads, and the like will destroy the stealth capabilities of any well-shaped stealthy design.
Visually, the J-20 does have some stealth faux pas. The tail section and engine nozzles appear to have little to no LO treatments or shaping. From a tail aspect, it almost appears that the Chinese have just given up on stealth altogether. Keep that in mind for later in our analysis too.
The J-20. Note the tail section and engine nozzles.
Mission
The Chinese are rapidly working toward a future A2/AD (Anti Access / Aerial Denial) concept of force. A2/AD is the future of defensive systems and includes fourth and fifth generation fixed-wing, as well as a Cyber network, and a robust IADS (Integrated Air Defense System). The Chinese currently have all but one part of their A2/AD protective net built…that missing puzzle piece is (you guessed it) a stealthy frontline fighter.
That’s about to change.
Some researchers speculate that the J-20 will have similar performance and agility as a Raptor, some think it will be a fighter/bomber only. I believe it will be more of a “night one” strike asset, with the ability to quickly penetrate enemy defenses, deliver weapons, and safely retreat. It’s not going to be an overly capable dogfighter.
Why do I think this?
From the J-20’s size to wing area alone, one can see that it simply will not be a highly maneuverable fighter. Especially with the weaker Saturn engines. Now add in the weight she will have. Sure, it will be fast, and stealthy by some measure, but looking at the design and numbers we have on the J-20, I just don’t see it performing like a Raptor on most fronts.
Remember those figures from above that I asked you to remember? The J-20 is a large and heavy bird, with primarily front hemisphere LO, can possibly carry a lot of fuel, and it has smallish wings and lower thrust as compared to similar “fighters.”
Based on that, what would you have it do?
Chinese J-20 in full burner. Note lack of LO treatments and designs around engine and tail.
The Black Eagle will certainly be the sharpest and most agile sword in the Chinese inventory, and it will be able to sneak in and deliver some crippling blows to any nearby adversary. Something to keep you up at night if you’re parking C2ISR (Command/Control Intelligence Surveillance Reconnaissance) or Carrier Groups somewhere offshore. Armed with capable air-to-air missiles, and pilots trained in LO tactics, it’s enough the outclass any US fourth generation fighter while BVR (Beyond Visual Range) or provide highly capable strike and standoff to China’s leaders.
We don’t know much about the J-20 Black Eagle yet, but as more are built and tested details will emerge. We have yet to see if the larger WS-15 engines will be fitted, and personally, I’m interested in seeing what kind of LO capabilities the Chinese will be able to incorporate into this large beast. Don’t forget those canards! Traditional canard-carrying aircraft are quite ‘dirty’ and easily spotted on radar.
Modern effective LO is much more than just shaping and angular panels. Time will tell if the Chinese can figure that out as well. I’m also watching for some flight test numbers. Speed, altitudes, and maneuverability (don’t forget those canards here too) might be abysmal, but it could also be off the charts.
Either way you look at it, the Chinese are not far behind us in 5th generation fighter technology. The technology gap continues to narrow.
Nate Jaros Nate “Buster” Jaros is a retired USAF fighter pilot with over 2,000 hours in F-16 C/D/CM and T-38A/C aircraft and over 500 hours in General Aviation aircraft. He is currently a Test Pilot, Instructor Pilot, and LO SME with Lockheed Martin Skunkworks. He has a Bachelor of Science degree as well as a Master of Business Administration and owns, operates, and maintains a 1969 V-tail Bonanza. Buster currently resides in Las Vegas, Nevada and is a long-time member of the Aircraft Owners and Pilots Association as well as the American Bonanza Society. You can find his book Engine Out Survival Tactics: Fighter Pilot Tactics for General Aviation Engine Loss Emergencies at most major retailers or at http://engineout.weebly.com
2 comments:
The AL-31FM has thirteen compressor stages and 4 turbine stages. This is a long engine with little or no advanced materials providing high thermal boundaries which means that pressure ratio is low. Add to this a .59BPR and you are talking a subsonic engine as well because there is simply not enough core flow to sustain supercruise.
For comparison, the F135 has a .57BPR and the F119 has a .3BPR.
It's the old 'thumb on garden hose' effect, if you have to cool the core with bypass air, you are not feeding it enough massflow to be able to generate a high speed nozzle efflux to push the jet beyond about Mach 1.15.
Mach 1.15 is a terrible place to be in for any jet because shock configurations on the inlet are unstable and put the engine in a borderline heat evacuation vs. shock stall condition while general transonic flow over the airframe requires maximum throttle to sustain the jet at a very draggy envelope point.
https://defenseissues.net/2014/12/06/fighter-aircraft-engine-comparision/
As the above LINK shows, the AL-41 is the AL-31 with tweaks. It is NOT the AL-41 VC engine as tested on the MiG-1.44. Therefore, it will behave with similar propensities and achieve most of it's supersonics capability through burner.
Half the back end of the J-20 is hollow. The nacelle cutouts, especially on the ventral side, extend almost to the weapons bays. that is how they saved on boat tail drag and weight on this jet. In turn, the long engines steal volume from centerbody tanks which means (along with the weapons bay) that the fuselage is largely a boxframe mounting point for carrying the wings which have the majority of the fuel.
That same long-engine issue keeps the weapons bays small, relative to the AFX, which had a bay long enough to fit GBU-24 and AGM-84E (Concept Art) or carry two JDAMs in tandem. Without tandem stations and given a weapons bay which is actually _narrower_ than the F-22 (no divider needed) you have to consider even the stubbiest of the FT series glide bombs are only going to fit one per hardpoint for a total of two or perhaps three in the bay. This is a pretty poor trade to make for all your BVR armament, especially when the side bays are not compatible with PL-15 and you are fighting an APY-9 + SM-6 equipped threat that can netcentric (shooter:illuminator) shoot you from upwards of 400km away with an airborne UHF surveillance radar providing midcourse guidance on a weapon that doesn't see the 'stealth fighter' at launch.
The J-20 wings are not small, the body is long, to accommodate 1980s engine carcass volumes. What makes this a critical distinction is that the F-22 is _not_ the ideal supersonic body because it is so compact, as an SCM (supercruise and maneuver) platform that it loses out on the ruling and fineness ratio end of drag build. The USAF are very honest when they say that the Raptor is a triumph of thrust minus drag and truly, it doesn't begin to move from Chevy Camaro to Ferrari 458 until it is above 40K where the air density is 200% lower than at sealevel.
That said, the J-20 could very well be faster and faster accelerating, if it uses A/B. Assuming Chinese RFLO works, the Raptor will never know it because we failed to integrate EOSS/AIRST onto the jet.
What the F-22 can do that the J-20 cannot is aggressively maneuver at supersonic speeds. The same 'bunched' compact appearance which ruins ruling also pushes the tails and the short F119s far enough up into the fuselage for most bending loads to be passed through the wing strongback. This includes vectoring and stabilator deflection of the tail booms which would be out of alignment with each other (too far aft on the jet) if it had a conventional empennage.
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