Sukhoi Su-57 / T-50 / PAK FA - flight testing and development Part II [2012-current]

[kaiserbill]

The slide just shows that it has already achieved supersonic performance during flight tests... not what the maximum possible speed is.

Exactly this.
This is from 2 years ago when the flight programme had half the amount of flights it has now.
It's simply an interesting indication of what they had tested to at that particular point, if it is indeed genuine.

 

[sferrin]

I'm no propulsionist here but I'd love to hear one comment about this.
I mean at such speed, the inlet pressure recovery and mass flow performance start to matter a lot.
Supersonic-wise (shockwave structure), the F-22 intake design seems amazingly simple for pushing significant engine thrust well above Mach 2, but I know very bright engineers have worked hard on this and can do wonders...
Not saying it is impossible, but (as you said in your previous post) it should by no means be close to a "cruise" speed condition.

Check out the XF8U-3 Crusader III's intake. It was also a very fast aircraft with a "fixed" intake.

 

[Sundog]

I'm no propulsionist here but I'd love to hear one comment about this.
I mean at such speed, the inlet pressure recovery and mass flow performance start to matter a lot.
Supersonic-wise (shockwave structure), the F-22 intake design seems amazingly simple for pushing significant engine thrust well above Mach 2, but I know very bright engineers have worked hard on this and can do wonders...
Not saying it is impossible, but (as you said in your previous post) it should by no means be close to a "cruise" speed condition.

The simplest inlet shock structure is a pitot inlet, where the shock wave is vertical (normal to the flow), like in the nose of the F-100. It's also the least efficient, but it's very simple and makes for a lighter structure.

Next is the 2D oblique shock inlet, which sweeps the shock back, like we've seen since the Vigilante and F-104/Mirage III. To adjust the shock, you can use ramps in the inlet to optimize it to minimize spillage drag and maximize pressure recover. The F-104 and Mirage III have a special case of a circular 2D shock wave which is seen in shock cones and half shock cones where the cone can be translated back and forth to adjust the shock for optimum performance. These make for simple efficient intakes where alpha isn't going to come into play much, unless you mount it ventrally, and then it can be good at higher alpha.

Then you have the 3D shock inlets, where the shock wave is swept in two planes allowing even better pressure recovery. Those were first seen on the YF-22, YF-23, and X-36, though that last was just for representational reasons, as the X-36 wasn't that fast. For LO reasons you want them fixed, but they can use internal fluidic controls, boundary layer suction and bleed blowing in the inlet, to adjust the inlet flow field.

 

[bipa]

Then you have the 3D shock inlets, where the shock wave is swept in two planes allowing even better pressure recovery. Those were first seen on the YF-22, YF-23, and X-36, though that last was just for representational reasons, as the X-36 wasn't that fast.

Thanks for your explanation. I see there are some sort of ramps on two sides but definitely no VG. Boundary layer suction (perforated sidewalls) hard to make out.
Also similar "ramps" on the Super Hornet it seems, and (much more visible) on the T-50.
A few months ago, I had noticed the following post which has a (probably illustrative) comparison plot of inlet performances:

http://www.secretprojects.co.uk/forum/index.php/topic,3536.msg264637.html#msg264637

The F-22 inlet performance is not very appealing in those slides (but I know this is in no way comprehensive and may not be the most reliable source).
Was there a difference between YF-22 and F-22 inlet? Were there fluidic control experiments? Don't you think the length and serpentine shape of the ducts may also put a heavy toll on high supersonic performance?

 

[XP67_Moonbat]

Haha! Awesome!

 

[Sundog]

Then you have the 3D shock inlets, where the shock wave is swept in two planes allowing even better pressure recovery. Those were first seen on the YF-22, YF-23, and X-36, though that last was just for representational reasons, as the X-36 wasn't that fast.

Thanks for your explanation. I see there are some sort of ramps on two sides but definitely no VG. Boundary layer suction (perforated sidewalls) hard to make out.
Also similar "ramps" on the Super Hornet it seems, and (much more visible) on the T-50.
A few months ago, I had noticed the following post which has a (probably illustrative) comparison plot of inlet performances:

http://www.secretprojects.co.uk/forum/index.php/topic,3536.msg264637.html#msg264637

The F-22 inlet performance is not very appealing in those slides (but I know this is in no way comprehensive and may not be the most reliable source).
Was there a difference between YF-22 and F-22 inlet? Were there fluidic control experiments? Don't you think the length and serpentine shape of the ducts may also put a heavy toll on high supersonic performance?

Once the air has passed through the shock waves at the inlet it's subsonic, although they still have to try to keep the flow as laminar as possible in the serpentine duct to prevent losses. One of the obvious examples of how simple fluidic controls could be employed is the boundary layer suction in front of the YF-23's inlet using porous materials that the boundary airflow can be removed through, although I don't think it was too much of a problem with either design due to the length of the ducts. The real trick is keeping the airflow from distorting too much with short serpentine ducts. They lower the weight by not being so long, but the curves of the serpentine portion have to be more severe (Acute?) due to the shorter length which could lead to flow separation issues. That's something that research is going into now for advanced stealth designs and has probably been ongoing since the beginning of usable full spectrum LO tech.

 

[bananaman]

Sukhoi T-50 Dog Fighting Missille Deployed

Found somewhere in a famous Chinese military forum, enjoy!

http://lt.cjdby.net/forum.php?mod=viewthread&tid=2142672&extra=page%3D3

 

[flanker]

Re: Sukhoi T-50 Dog Fighting Missille Deployed

We have a T-50 thread, dont really need another one just for this;

http://www.secretprojects.co.uk/forum/index.php/topic,15626.0.html

Also, inb4 "I am not convinced those are weaponbays" crowd...

 

[RadicalDisconnect]

Those aren't official Sukhoi drawings, and just from a first impression point of view, the way it's depicted in these drawings leaves a very large structural hole. That being said I have no doubt that these fairings are weapon bays, but not in the manner shown above. Besides, I thought the K-74M2 for the PAK FA is supposed to have reduced cross section to help fit in there.

 

[sferrin]

Re: Sukhoi T-50 Dog Fighting Missille Deployed

We have a T-50 thread, dont really need another one just for this;

http://www.secretprojects.co.uk/forum/index.php/topic,15626.0.html

Also, inb4 "I am not convinced those are weaponbays" crowd...

That's too bad. I'd have thought they'd have gone with something a bit more elegant rather than scabbing them on like afterthoughts.

 

[Grey Havoc]

https://www.rt.com/news/318575-pak-fa-square-missiles/

 

[flanker]

Supposedly T-50 was flying with open sidebays containing "R-73's" today... Lets cross fingers, toes, and all the limbs for pics...

Meanwhile; http://russianplanes.net/id183637

Might have been it i guess.

 

[sferrin]

LOVE that paint job.

 

[flanker]

It is funny, people either love it or absolutely loathe it.

I didn't like the original one with defuse camo but prefer this one. Still, splinter is the best.

 

[DrRansom]

New background image...

That side profile looks a ton like the YF-23.

 

[kaiserbill]

New background image...

That side profile looks a ton like the YF-23.

I was just going to say that the T-50 and F-23 both have great visual appeal, to me at least. They just seem to be slim in all the right places, and all the bulges working to enhance that. ;D

 

[bobbymike]

http://www.janes.com/article/58166/singapore-airshow-2016-analysis-pak-fa-s-asian-export-hopes-stymied-by-lack-of-fifth-generation-qualities

 

[RadicalDisconnect]

That's a pretty crappy article, the author can't even get the T-50's radar and engine correct. Then again it's Reuben Johnson, so I'm not expecting much in the first place.

 

[kaiserbill]

Jane's isn't what it used be.

 

[RadicalDisconnect]

The official UAC twitter makes a pretty incredible claim.

https://twitter.com/UAC_Russia_eng/status/700649635103178753

384 m/s climb rate. Any credence to this?

 

[flanker]

Check the source link, then check the source the source is giving...

 

[Deino]

Check the source link, then check the source the source is giving...

But isn't if funny that the official UAC-twitter page the post this BS ???

 

[flateric]

That's not funny at all to my sorrow

 

[kaiserbill]

I haven't bothered to click on the link, but why are people assuming something in that range as an initial or maximum rate-of-climb is BS?
It's very high, but not beyond the realms of possibility, or science fiction.
Just from memory, the Mirage F-1 equipped with the M53 turbofan had an initial or maximum rate of climb of about 300m/s and it didn't exactly have the highest thrust-to-weight ratio in the world. As I recall, the Mirage 4000 had a higher rate of initial or maximum climb, somewhere over 300m/s, as did the MiG-29.

 

[overscan (PaulMM)]

384m/s rate of climb is at least 1382.4km/h (Mach 1.1+ at sea level, Mach 1.26+ at 30,000ft) assuming a totally vertical climb - if we are talking any lesser angle its even faster. Not impossible I guess, but unlikely. Funnily enough, the Yak-45 got crucified at PFI design conference when Yakovlev claimed an almost identical climb rate until it was pointed out that meant it was going supersonic, pointing directly upwards.

 

[kaiserbill]

I agree it's unlikely, and as I said, it's very high.
Still, I will hold off on calling it complete BS yet, especially seeing as we have had previous fighters/prototypes that have had stated initial or maximum rates of climb of about 85% of that figure flying for decades.
Apart from those aircraft, over 40 years ago the Streak Eagle maintained a climb rate at over Mach 1 all the way up to 9000m, and that profile included going through Mach 1 whilst in the the first phase of the climb after pulling up from the horizontal, including a speed of Mach of 1.05 whilst climbing through 6000m.
I'm aware the Streak Eagle was specially prepared for the various records, but that was approaching half a century ago.
Without looking deeply into it, I can only imagine that Sukhoi's similarly stripped down P-42 that took a whole slew of records off the Streak Eagle 30 years ago probably attained higher Mach numbers in the climb to beat the previous records.

As I said, probably unlikely, but not beyond the realms of possibility, and as a figure given for a maximum rate of climb, I would hesitate to simply call it BS just yet.

 

[sferrin]

I agree it's unlikely, and as I said, it's very high.
Still, I will hold off on calling it complete BS yet, especially seeing as we have had previous fighters/prototypes that have had stated initial or maximum rates of climb of about 85% of that figure flying for decades.
Apart from those aircraft, over 40 years ago the Streak Eagle maintained a climb rate at over Mach 1 all the way up to 9000m, and that profile included going through Mach 1 whilst in the the first phase of the climb after pulling up from the horizontal, including a speed of Mach of 1.05 whilst climbing through 6000m.
I'm aware the Streak Eagle was specially prepared for the various records, but that was approaching half a century ago.
Without looking deeply into it, I can only imagine that Sukhoi's similarly stripped down P-42 that took a whole slew of records off the Streak Eagle 30 years ago probably attained higher Mach numbers in the climb to beat the previous records.

As I said, probably unlikely, but not beyond the realms of possibility, and as a figure given for a maximum rate of climb, I would hesitate to simply call it BS just yet.

As you said, both aircraft were stripped down. (And the P-42 had it's engines hot-rodded to something like 31k thrust each.)

 

[flanker]

I haven't bothered to click on the link, but why are people assuming something in that range as an initial or maximum rate-of-climb is BS?

Sigh. Clicking on the link would be a start.

 

[Deino]

That's not funny at all to my sorrow

Sorry that I did not use "..." or a certain smiley, since it was meant ironic or even sarcastic !

 

[kaiserbill]

I haven't bothered to click on the link, but why are people assuming something in that range as an initial or maximum rate-of-climb is BS?

Sigh. Clicking on the link would be a start.

Sigh. I did afterwards. And?
To paraphrase, you reading my posts properly would be a start.
I'm addressing the figure given as a performance value, as to whether it is possible, not whether UAC tweeted it, retweeted it or whatever, which I was aware of on other forums before this one. I simply didn't see the need to click on a link I knew I'd already read previously and was aware of the veracity arguments.

A maximum climb figure of just over Mach 1.1 at low alitude is not in the realms of science fiction, going on values stretching back almost 50 years. I'll reiterate again from my posts if you're having difficulties:

why are people assuming something in that range as an initial or maximum rate-of-climb is BS?

I agree it's unlikely, and as I said, it's very high.

As I said, probably unlikely, but not beyond the realms of possibility, and as a figure given for a maximum rate of climb, I would hesitate to simply call it BS just yet.

I'm completely disinterested in the veracity of the exact claim, and nowhere have I stated I believe the actual claim. I'm saying that although it will probably be unlikely in my view, I wouldn't exactly say that a figure in the 380m/s range is an absolute impossibility.

???

 

[flanker]

People are mostly assuming it is BS because of the BS source, not necessarily dismissing it because "It is impossible!".

 

[overscan (PaulMM)]

Wikipedia has now added it, which means it will now be self-sustaining. Note that Wikipedia references the Russian News site article, but fails to note that it quotes a second Russian News site, which quoted Facebook. So really, Wikipedia is using a Facebook Group post as a valid source. Go Wikipedia.

Next, the BBC will steal the data from Wikipedia without attribution, Wikipedia will edit the reference to be the BBC article, and noone will ever recall where this came from.

Welcome to the 21st century

 

[kaiserbill]

That succinctly sums the mass media and social networking. ;D

 

[overscan (PaulMM)]

What I find hilarious about wikipedia is I know an engineer who worked on a specific aircraft who tried to correct some of the huge mistakes in an article and had all his edits reverted because he couldn't provide a printed or online source. So, he'd have to publish a book or web article then quote himself in order to fix bad information on a plane he helped to design.

 

[flateric]

Wikipedia has now added it, which means it will now be self-sustaining. Note that Wikipedia references the Russian News site article, but fails to note that it quotes a second Russian News site, which quoted Facebook. So really, Wikipedia is using a Facebook Group post as a valid source. Go Wikipedia.

Next, the BBC will steal the data from Wikipedia without attribution, Wikipedia will edit the reference to be the BBC article, and noone will ever recall where this came from.

Welcome to the 21st century

As Berkut noted, FB group refers to http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=782
as source of 384 m/s climb rate, but there's no any mention of this figure there - they list 361 m/s figure.
Well, they also repeat BS about 8 internal hardpoints, wrong dimensions, etc. in specs section.

 

[RadicalDisconnect]

To be fair the source on Wikipedia has been flagged as unreliable. It would be nice if they got rid of it altogether. Though you'd think that the official UAC twitter would be better than retweeting something like that.

EDIT: Well, it's been stated in this Russian news channel as well. https://youtu.be/CxSSLCioEV8?t=8m50s

I think the climb figure may be doable with the izd.30 engines, though I find it less likely with the interim ones. The T-50 is heavier than the Su-27 by at least 10% (18 tons vs 16.3 tons), with 27% more wing area, with only 20% thrust with the 117. But since such climb rate is well into the transsonic region, the T-50 may very well have better drag characteristics at those speeds since it's optimized for supersonic performance. Accounts from Dozer several years back documented that the F-22 can reach 310 m/s fully loaded and in less than ideal climb profile, so with definitive engines I think it's possible for the T-50 to do something similar.

 

[flateric]

The T-50 is heavier than the Su-27 by at least 10% (18 tons vs 16.3 tons)

 

[RadicalDisconnect]

I would be surprised if it's under 18,000 kg. That's the value PiBu listed in his latest publication. That's already quite a bit lower than the F-22's 19,700 kg empty weight, and the T-50 is both longer and has greater wingspan, with slightly larger wing area. Reports suggest that the T-50 is about 25-30% composites structurally, pretty similar to the F-22. Also, given that the T-50 allegedly carries more fuel than the Su-27 (and more than the F-22), and can carry larger weapons internally, I would be quite astounded if its empty weight is substantially lower than the F-22's, especially if they were to have similar performance. If so, then it would be an astounding advance in structures.

 

[Grey Havoc]

Wikipedia has now added it, which means it will now be self-sustaining. Note that Wikipedia references the Russian News site article, but fails to note that it quotes a second Russian News site, which quoted Facebook. So really, Wikipedia is using a Facebook Group post as a valid source. Go Wikipedia.

Next, the BBC will steal the data from Wikipedia without attribution, Wikipedia will edit the reference to be the BBC article, and noone will ever recall where this came from.

Welcome to the 21st century

https://xkcd.com/978/

;D​

 

[Rhinocrates]

I kid you not, I once received an essay from a student with exactly one entry in the bibliography: google.com.