Shenyang / Chengdu 6th Gen Demonstrators?

[paralay]

A channel with a volume of almost 8 m3 passes through the 94 m3 aircraft, 8.5% of the useful volume is purely for purging and placing another engine. Isn't it too greasy? And it could be a tank with 6.4 tons of fuel...

PAK DP, J-36 and NGAD

 

[Mike Pryce]

Demonstrators have their place. The YF-22/-23 were not merely demonstrators. The X-32/-35 were. The AFTI F-16, and F-111 were. The SMTD F-15 was. If you want to see if a particular technology is worth including on future production aircraft you put it on a demonstrator, not a prototype.

Things like AFTI are fine (still no history written on AFTI, would love to see one) to try things on modified, existing, aircraft. It's the whole aircraft demos that I think are a waste. You have a whole design/build cycle to make something that is not representative of what you will eventually get. It is procurement procrastination.

 

[red admiral]

It's the whole aircraft demos that I think are a waste. You have a whole design/build cycle to make something that is not representative of what you will eventually get. It is procurement procrastination.

Yeah, it's basically just making a non-representative prototype. And today you're probably not even including the "hard" bits like the real software.

But there's other reasons for doing this sort of activity, like keeping or rebuilding aircraft design and manufacturing skills at much lower cost than a full scale development activity.

 

[Mike Pryce]

Yeah, it's basically just making a non-representative prototype. And today you're probably not even including the "hard" bits like the real software.

But there's other reasons for doing this sort of activity, like keeping or rebuilding aircraft design and manufacturing skills at much lower cost than a full scale development activity.

Until you do a full development you don't have the skills to do it.

The impressive thing about the J-10/J-20/ 'J-36' chain is they seem to have learned that. They appear to be going through full development in less time than others do demos. EAP got the go ahead in 1982 and the RAF got to use Typhoon in 2006. All despite having Tornado before. The demo made them lose experience due to delay.

 

[NMaude]

. "X" is for experimental.

Only as an affix, as a prefix it indicates a prototype.

 

[Avimimus]

That was the gameplan for Typhoon*, and yet it still featured a bubble-canopy and good dogfighting capability. The two concepts aren't mutually exclusive, which makes me wonder "Why?".

* And presumably is for GCAP.

It may be worth noting that the beginning of the Eurofighter program is closer in time to WWII than to the present day (1942 actually).

 

[Avimimus]

Having a third engine for a supersonic aircraft is much more critical than for a subsonic one. We are losing internal volumes to the engine itself and the air intake duct. And there could be fuel there

Well, one needs similar levels of airflow for two large engines as one needs for three small engines - correct? One might have more duct losses due to higher surface area, but it might also be structurally easier to use three smaller ducts rather than two larger ones?

I always saw the decision to go with two engines as a way of reducing engine manufacturing and maintenance costs - but there isn't really anything two large engines can do that three engines 2/3rds their size cannot.

 

[Ainen]

Until you do a full development you don't have the skills to do it.

The impressive thing about the J-10/J-20/ 'J-36' chain is they seem to have learned that. They appear to be going through full development in less time than others do demos. EAP got the go ahead in 1982 and the RAF got to use Typhoon in 2006. All despite having Tornado before. The demo made them lose experience due to delay.

doing things fast is good only when (1)you actually need that you do, and (2)you'll have something else to do.
US, Russia, China design planes nonstop.
For Europe stretching things is vitally important - idle engineering houses degrade, upgrades and paperwork isn't enough.

 

[red admiral]

Until you do a full development you don't have the skills to do it.

I agree, but it's better than nothing. Better still is doing multiple full scale development projects with one design team / company - but China is the only one in that position now. For the West then it's simply priced itself out of this approach e.g. the UK can't afford to drop £20bn+ every 10 years on this

 

[Avimimus]

Better to have SRAAM to shoot down subsonic cruise missiles and helicopters than full blown BVRAAM.

But one can use other platforms for that - one doesn't need a supercruising, stealth, high altitude platform.

 

[BullpupRafale]

The best is a more efficient engine not adding one and carrying it as dead weight.

In example Mirage Balzac V versus harrier, or Yak-141 versus F-35B.

carrying extra engines shows engine inefficiency.

Add 3 engines increase cross section thus you add extra drag, if the Americans have better engines I doubt they will use 3 engines.

Tristar L1011 vs A-300 showed twin engines are better than 3, because they reduce problems.
Drag is one of them.

To early to say until i see the american or European 6th generation aircraft, but 3 engines are to be used otherwise are a waste of fuel and lack of space, this is contradictory since more space means more volume and more volume translates in weight.

This aircraft unveiling shows more a propaganda stunt than real capacity specially if western aircraft are planned with 2 engines

It is not dead weight of any kind to have shut off the middle engine when in process of loitering in some area as otherwise if it were active as other two thus would cause it to go faster thus require to more frequently maneuver back and forth to stay within an area it is stationed at to observe and or defend.

For loitering at some point middle on could be turned on and other two turned off. If weight of aircraft overtime decreases to 40 tons and WS-15 at 90 percent throttle was to have 10 ton force dry thrust output.

 

[Avimimus]

Yet SRAAMs are still integrated, even when people are screaming for the integration work to cover other weapons.

This is precisely my point! The tradeoffs tell us something about the design philosophy, or indicate an element of it we are not seeing.

I wonder if the side-bays are actually for SRAAMs - have we ruled out that they are sized for MRAAMs?

 

[siegecrossbow]

I wonder if the side-bays are actually for SRAAMs - have we ruled out that they are sized for MRAAMs?

They are capable of housing multiple MRAAMs probably. If you want to add SRAAMs I don’t see the difficulty.

 

[Avimimus]

The best is a more efficient engine not adding one and carrying it as dead weight.

In example Mirage Balzac V versus harrier, or Yak-141 versus F-35B.

carrying extra engines shows engine inefficiency.

Add 3 engines increase cross section thus you add extra drag, if the Americans have better engines I doubt they will use 3 engines.

Tristar L1011 vs A-300 showed twin engines are better than 3, because they reduce problems.
Drag is one of them.

To early to say until i see the american or European 6th generation aircraft, but 3 engines are to be used otherwise are a waste of fuel and lack of space, this is contradictory since more space means more volume and more volume translates in weight.

This aircraft unveiling shows more a propaganda stunt than real capacity specially if western aircraft are planned with 2 engines

So, you are saying that - if the NGAD doesn't have a single engine it is a sign of inefficiency and technological inferiority?

 

[siegecrossbow]

Looks like the flaps on J-36 doesn’t have traditional exposed hinges.

 

[paralay]

Well, one needs similar levels of airflow for two large engines as one needs for three small engines - correct?

For two engines of ~25 m3
For three engines of ~27 m3
Yes, this argument does not show a significant difference

 

[DWG]

It may be worth noting that the beginning of the Eurofighter program is closer in time to WWII than to the present day (1942 actually).

I'm talking about planning that was current in the early '90s and specifically related to the Su-27. Still 30 years ago, but closer than WWII. It's worth bearing in mind that when we look at these new aircraft, unless they're really bare bones tech demonstrators, they're likely the result of projects that are a decade old or more at this point.

 

[DWG]

The best is a more efficient engine not adding one and carrying it as dead weight.

Well obviously, but we live in the real world and engines that are efficient for loiter tend not to be efficient for high speeds. MPAs have a long history of optimising loiter by throttling back or shutting down engines. If you need three engines for some segment of flight, but can loiter on one or two, then why use all three for that element when using one or two will extend your loiter time?

 

[F-14ATomcat]

It is not dead weight of any kind to have shut off the middle engine when in process of loitering in some area as otherwise if it were active as other two thus would cause it to go faster thus require to more frequently maneuver back and forth to stay within an area it is stationed at to observe and or defend.

For loitering at some point middle on could be turned on and other two turned off. If weight of aircraft overtime decreases to 40 tons and WS-15 at 90 percent throttle was to have 10 ton force dry thrust output.

same was Balzac V, but harrier showed it is not needed a single engine can do what in Balzac V nine engines did.

I am sure that is not practical but time will show it because more engines mean also higher maintenance, price and lower numbers produced

 

[F-14ATomcat]

So, you are saying that - if the NGAD doesn't have a single engine it is a sign of inefficiency and technological inferiority?

no, i did not say that I say ideally one engine is the best, but 2 are for heavier aircraft, 3 or 4 are too many in fighter aircraft.


That aircraft in my opinion is underpowered, it has solution to built it quickly as propaganda but I doubt the NGAD will use 3 engines, I am sure it will have 2

 

[F-14ATomcat]

Well obviously, but we live in the real world and engines that are efficient for loiter tend not to be efficient for high speeds. MPAs have a long history of optimising loiter by throttling back or shutting down engines. If you need three engines for some segment of flight, but can loiter on one or two, then why use all three for that element when using one or two will extend your loiter time?

how many aircraft have 3 engines these days?

tell me airliners?

Jet engines are less likely due to fuel use.

unless you talk about drones most modern aircraft with jet engines do not use 3 engines and there is a reason why.

there are very few aircraft with 3 jet engines now, most will use 2 or 1

 

[Mike Pryce]

I agree, but it's better than nothing. Better still is doing multiple full scale development projects with one design team / company - but China is the only one in that position now. For the West then it's simply priced itself out of this approach e.g. the UK can't afford to drop £20bn+ every 10 years on this

Probably not for the new breed of flying 'battlecruisers' but even the share of a joint project can be more than a national one. Warton really wanted the P.120. Bigger, better for UK reqts, and cheaper than EFA. It would even have used some of the EAP demo bits too (FBW). And no 4 nation approval process for mods. Saving a pile of cash for the next big thing perhaps.

China has avoided a lot of the pitfalls of collaboration so they move faster.

 

[Josh_TN]

I think that's more philosphical/ethical. The kill-chain ideally needs eyes on target to confirm no civilians in the area for Western ethics, which is more difficult to arrange for strike than for air-to-air. I'm not sure PLAAF consider that an important consideration.

CCA is, or at least was, part of NGAD - Air Dominance. The current focus is naturally A2A. The strike complex is B-21. That does not preclude the USAF from adopting A2G UCAVs at a later date as CCA or under a different program. But the more pressing need is for more counter air.

PRC CCA analogs might well be driven by different requirements and limitations and be far larger than US equivalents. If nothing else, the engine options for 3,000-8000 lb thrust is probably sparse compared to the US commercial industry. Range requirements might also be completely different; CCA Incr1 is set to be paired with F-35. A Boxer CCA would have to have a lot more range.

 

[Ainen]

I agree, but it's better than nothing. Better still is doing multiple full scale development projects with one design team / company - but China is the only one in that position now. For the West then it's simply priced itself out of this approach e.g. the UK can't afford to drop £20bn+ every 10 years on this

Well, no one force bends UK to design 35-40t class GCAP it can't truly afford as a fighting unit?
Still, it's the choice.

 

[Josh_TN]

Will be quite interesting if side radars and optics are in fact main ones.

I would think anything forward mounted would be redundant at those angles? The B-21 appears to use a pair of side facing radars admittedly with significantly lower sweep, but AESA arrays should still give good forward coverage with some overlap.

 

[Avimimus]

no, i did not say that I say ideally one engine is the best, but 2 are for heavier aircraft, 3 or 4 are too many in fighter aircraft.

That aircraft in my opinion is underpowered, it has solution to built it quickly as propaganda but I doubt the NGAD will use 3 engines, I am sure it will have 2

I am pretty sure the NGAD will have two engines as well.

But the basic point is the same: If you can produce engines of differing thrust but equivalent T/W and SFC... then one could go with a single 240kn dry thrust engine, two 120kn engines, three 80kn engines or four 60kn engines to do the same task.

Now, the scaling of T/W ratios and SFC may not be linear, the engines may perform differently over different parts of the flight regime, and there maybe structural implications etc. So it isn't that simple. But the basic point remains.

Assuming T/W and SFC don't change with the scale of the engine, then the considerations are things like manufacturing and maintenance costs... balanced against having an engine with enough thrust and possibly things like having an ability to switch off an engine and close its intake duct in flight to cruise at 2/3rds power.

 

[Josh_TN]

As for engines, I had thought perhaps the odd arrangement was an attempt to duplicate adaptive engine capabilities in a shorter timeframe, but the posts here have convinced me three of the same type simply for desired performance is more likely. That might not preclude a loiter mode with one shut down.

Either way, the implication to me is that an off the shelf engine design (or designs) is used to shorten development. The B-21 took a similar route. This makes me wonder if the entire Boxer project was not similar to the B-21s approach of only using tech readiness level 6 or above.

 

[red admiral]

Assuming T/W and SFC don't change with the scale of the engine, then the considerations are things like manufacturing and maintenance costs... balanced against having an engine with enough thrust and possibly things like having an ability to switch off an engine and close its intake duct in flight to cruise at 2/3rds power.

They do change with the scale of the engine, but differently. RR claimed EJ200 was at about the peak in terms of thrust/weight. But this optimum point will change with technology advances. SFC should improve with increasing scale due to smaller % losses around fixed size gaps, steps etc but is negligible at this engine scale.

Another factor is engine type availability. If the aircraft has 3 x WS-10 or WS-15 engines then that's 90-120,000lbf total. And China simply doesn't have 2 x 45,000-60,000lbf fighter engines lying around given their 10+ year development timeline. So if you need that much thrust now, then you simply stick 3 existing engines.

 

[DWG]

Jet engines are less likely due to fuel use.

Nimrod regularly shut down engines for loiter. And fuel use is precisely the reason you'd want to do it.

 

[paralay]

And China simply doesn't have 2 x 45,000-60,000lbf fighter engines lying around given their 10+ year development timeline. So if you need that much thrust now, then you simply stick 3 existing engines.

A new generation aircraft implies a new generation engine, it is not yet available, but it will appear

 

[Ainen]

A new generation aircraft implies a new generation engine, it is not yet available, but it will appear

Is it worth it, when you can use 3 from available pipeline, and still get the capability and unified supply?

Soviet Union used to feed engine design houses by making new engines for everything, didn't end well.
Also, China doesn't have that many of them, to make a separate oversized supercruising engine.

 

[Avimimus]

They do change with the scale of the engine, but differently. RR claimed EJ200 was at about the peak in terms of thrust/weight. But this optimum point will change with technology advances. SFC should improve with increasing scale due to smaller % losses around fixed size gaps, steps etc but is negligible at this engine scale.

Another factor is engine type availability. If the aircraft has 3 x WS-10 or WS-15 engines then that's 90-120,000lbf total. And China simply doesn't have 2 x 45,000-60,000lbf fighter engines lying around given their 10+ year development timeline. So if you need that much thrust now, then you simply stick 3 existing engines.

Speaking of which - from published numbers it seems SFC substantially improves with larger turboprops... any idea why this is the case?

Is it worth it, when you can use 3 from available pipeline, and still get the capability and unified supply?

Soviet Union used to feed engine design houses by making new engines for everything, didn't end well.
Also, China doesn't have that many of them, to make a separate oversized supercruising engine.

I also wonder - if you need a WS-15 class engine for your other fighters, and you might upgrade those fighters with an improved engine of the same size... does it make sense to invest in developing a second larger fighter engine?

What is the cost of running an entire second fighter engine program (that you can't use for your other fighters) compared to manufacturing/supporting 33% more engines for 100 or 200 airframes?

Assuming 200 of this new combat aircraft were built - we'd be talking about manufacturing (and having spares for) 400 of these new engines... or manufacturing (and using spares) for 600 WS-15 engines... which is only 200 additional engines...

 

[Acatomic]

Guys, this whole “engine issue” is getting overblown.

Focusing on internal weapon bay and its size do you think there’s a Chinese equivalent of AIM-174 in the pipeline?

 

[Ainen]

Guys, this whole “engine issue” is getting overblown.

Focusing on internal weapon bay and its size do you think there’s a Chinese equivalent of AIM-174 in the pipeline?

PL-17? it's in service, not in pipeline.

 

[Acatomic]

I could be wrong, but I was under the impression that AIM-174 is bigger in size/range than PL-17.

 

[sferrin]

Only as an affix, as a prefix it indicates a prototype.

Which aircraft was the X-15 the prototype for?

 

[Sintra]

I could be wrong, but I was under the impression that AIM-174 is bigger in size/range than PL-17.

Acording to Douglas Barrie and the IIS, the PL-17 is one meter longer than the AIM-174.

https://www.iiss.org/online-analysis/military-balance/2024/07/phoenix-successor-redux-the-usns-range-riposte-to-chinas-pl-17/

 

[Josh_TN]

Guys, this whole “engine issue” is getting overblown.

Focusing on internal weapon bay and its size do you think there’s a Chinese equivalent of AIM-174 in the pipeline?

They already have PL-17.

 

[Josh_TN]

I could be wrong, but I was under the impression that AIM-174 is bigger in size/range than PL-17.

Only modestly. IMO the next step in long range engagement missiles is an air breather to increase range and decrease flight time. Solid fuel motors like PL-17/AIM-174 achieve high speeds initially but then coast to their targets post burn out. You can employ multiple pulses but this does not shorten the overall flight time much; it mostly just greatly improves terminal kinematics. For multi engine targets that is not especially useful. Engagements at maximum range likely take 10-15 minutes and leave the weapon transonic. A ramjet or scramjet would have a lower peak speed but dramatically shorter total engagement time at long ranges.

 

[totoro]

I could be wrong, but I was under the impression that AIM-174 is bigger in size/range than PL-17.

Approximate volume of aim174 is 0.410 cubic m. Pl17s is around 0.390 cubic m. That's a rather small difference. Given that aim174 kept the internals of the rim174, and its mid body fins, all optimized for different trajectory starting from a fairly low altitude of a few km, it's plausible pl17 can (more than?) compensate for the small difference in volume. And then there is likely bigger drag that aim174 suffers due to its fins and in small part its diameter. I wouldn't be surprised if pl17 actually outranged aim174 by a small margin.