J-20 5th Gen Fighter Thread VI

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Stratton

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Do we have a consensus on where the J-20 is in in terms of the WS-10 integration? Early jets had AL-31F, same as Su-35. Also, what are the physical nuances that differentiate at WS-10 powered aircraft from an AL-31F jet?
 

Deino

Lieutenant General
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Do we have a consensus on where the J-20 is in in terms of the WS-10 integration? Early jets had AL-31F, same as Su-35. Also, what are the physical nuances that differentiate at WS-10 powered aircraft from an AL-31F jet?

No, No, No and I hope this helps .. but slowly step by step.

1. No, we have no common "consensus on where the J-20 is in in terms of the WS-10 integration". IMO there are still only two confirmed prototypes (2021 & 2022) powered by that WS-10C, WS-10C or whatever it is called. Additionally there are reports that one earlier prototype is testing the TVC-engine.

2. No, the earlier J-20s were using the AL-31FN with the gear-box on the bottom, not the F, which is reserved for the Flanker variant with the gear-box on top, whereas later ones used (most likely) the standard AL-31FN Series 3 as most J-10B/C. IMO the current LRIP birds use a dedicated variant based on the AL-31FM2 but modified for the J-20A with higher thrust, but that's unconfirmed.

3. No, as @Air Force Brat noted already but not entirely correct, the Su-35S uses the 117S - not F117 (that's the C-17's engine :p), which has no relation to the one used in the J-20 other than being an AL-31-offspring of some sort.

4. I hope this comparison helps ... both nozzles are so much different, that IMO there's no problem to differ a standard AL-31-powered one from the new WS-10-powered ones:

J-20A WS-10 - AL-31FN.jpg
 

gelgoog

Brigadier
Registered Member
I wonder if the Chinese won't install the 117S on the J-20 as an interim step. Now that they did the Su-35 purchase perhaps the Russians will allow them to buy the engines. But if like you say the gear box is on the bottom that might make things more difficult as it would require a dedicated variant to be manufactured.

PS: Now I noticed the M2 has more thrust. Well that might not make the 117S much of an upgrade then. The only extra thing it has is TVC but that will require avionics changes.
 

Air Force Brat

Brigadier
Super Moderator
I wonder if the Chinese won't install the 117S on the J-20 as an interim step. Now that they did the Su-35 purchase perhaps the Russians will allow them to buy the engines. But if like you say the gear box is on the bottom that might make things more difficult as it would require a dedicated variant to be manufactured.

PS: Now I noticed the M2 has more thrust. Well that might not make the 117S much of an upgrade then. The only extra thing it has is TVC but that will require avionics changes.

Yes, given the current state of air combat, I rather doubt the J-20 will be flying with OVT? drawings notwithstanding, we've seen no photographic evidence of OVT flying on J-20's? As you point out that would require rather complicated changes to the Flight Control System, technically "avionics" refer to the external instrumentation, flight instruments, navigation and weapons systems, that we would generically refer to as "black boxes" sliding in and out on "trays" or rails.

The FCS is run through the onboard computer and part of the aircraft proper, so while more thrust is always needed and wanted, the J-20 like the F-35 likely has a more than high enough "pitch rate" aerodynamically to "put you to sleep"..... and no matter what anybody says, the primary purpose of OVT is to increase "pitch rate". The secondary purpose is to facilitate maneuvering in, and recovery from "post stall"! A flight condition where the aircraft has aerodynamically "departed', typically the nose would "fall through" and the aircraft would be "out of control" until back up to flying speed....

OVT enables you to continue to "point the nose" with engine exhaust vectoring, holding the airplane, against its will, with the nose up, and able to pitch, or in the case of Russian 3D OVT, to yaw the nose and continue to "engage" the other aircraft by firing weapons, even though the aircraft is "stalled"..

Dr. Song made certain that one of the main design criteria of the J-20, was aerodynamic maneuvering post stall, and full recovery to "controlled flight" without the weight, expense, and maintenance complexity of OVT.... I believe he succeeded in that endeavor, the F-35 has also dispensed with OVT, and is quite agile, as evidenced by the RIAT flying display, hopefully we will see the J-20 perform some similar feats at Zhuhai?
 

Stratton

New Member
Registered Member
No, No, No and I hope this helps .. but slowly step by step.

1. No, we have no common "consensus on where the J-20 is in in terms of the WS-10 integration". IMO there are still only two confirmed prototypes (2021 & 2022) powered by that WS-10C, WS-10C or whatever it is called. Additionally there are reports that one earlier prototype is testing the TVC-engine.

2. No, the earlier J-20s were using the AL-31FN with the gear-box on the bottom, not the F, which is reserved for the Flanker variant with the gear-box on top, whereas later ones used (most likely) the standard AL-31FN Series 3 as most J-10B/C. IMO the current LRIP birds use a dedicated variant based on the AL-31FM2 but modified for the J-20A with higher thrust, but that's unconfirmed.

3. No, as @Air Force Brat noted already but not entirely correct, the Su-35S uses the 117S - not F117 (that's the C-17's engine :p), which has no relation to the one used in the J-20 other than being an AL-31-offspring of some sort.

4. I hope this comparison helps ... both nozzles are so much different, that IMO there's no problem to differ a standard AL-31-powered one from the new WS-10-powered ones:

View attachment 48923
Thanks, Deino. Very helpful.
 

Hyperwarp

Captain
Its amazing the amount of deflection the "ruddervators" are capable of,, lots of control throw to assure recovery from any post stall attitude.

I am wondering whether they can act like airbrakes?

By they way deino, are there any photos of production or in service J-20 using airbrakes? I wonder whether they have eliminated them already. The TD 2001/2002 have barn-door sized airbrakes. Eliminating them (like in the Su-35) would save even more weight.
 

Air Force Brat

Brigadier
Super Moderator
I am wondering whether they can act like airbrakes?

By they way deino, are there any photos of production or in service J-20 using airbrakes? I wonder whether they have eliminated them already. The TD 2001/2002 have barn-door sized airbrakes. Eliminating them (like in the Su-35) would save even more weight.

I would say that yes, they do also deflect together to provide aerodynamic braking, not sure whether that would be just on "roll out" or in the air as well??

the F-22 rudders do deflect together to provide aerodynamic braking, but the J-20 does have drag chutes, the F-22 does not..
 
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