RuAF News and development Thread part 15

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There is probably an error in the tank capacities in that chart since it shows more total fuel than what can actually be carried. But general layout is correct and it shows the two fuel tanks in rear fuselage.

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Weight limits apply for runway operations. All fuel tanks can be filled to capacity during aerial refueling.

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One of the stated goals of izd.30 is lower maintenance and operating cost. Especially since izd.117 is considered not economical to run. More power is not the only goal of izd.30, higher MTBO and better operating economy are major goals.

Do you have sources for the claim in bold letters? While the reduced number of stages is coherent with claimed easier maintenance, the engines of the Al-31F family are among the ones with better fuel economy. Izd. 117 has essentially state of the art combustion, they would not get a serious improvement in TSFC unless they reduce the BPR, and that makes little sense if you want to produce a high specific thrust engine. Also the maintenance of the 117S is much better than old Al31F with 4,000 h operative life, I don't have the data for the 117 but considering it is the premium, non-export version of the 117S, I would assume it is not worse in that parameter either. Furthermore, Marchukov said izd. 30 keeps the TSFC of the AL-31F, so no apparent improvements are to be expected there. The achievement is to have the specific thrust of a turbojet and the TSFC of a relatively high BPR turbofan.

Here is diagram of F-22 fuel tanks, you can see the two rear tanks by the engine bays.

Great, thanks. Indeed there are two relatively big tanks in the rear fuselage. I wonder what would be their capacity is (the picture posted above seems to overstate the values, see more below) and what was the capacity of the same tanks in YF-22.

From my limited experience fooling around with 3D modelling I can say that nothing adds volume like a good dorsal tank, because it is wide, deep and long, unlike other tanks that are very limited in one or two dimensions. In the case of the F-22, it is easy to see that the dorsal tank is relatively swallow due to the air ducts and loses all the space occupied by the side bays, which would be as big as the rear fuel tanks at least. That is where I would expect improvements to be done, in order to reach internal fuel values in line with those of a Su-35.

The tank capacity shown in the picture by paralay shows a total 13,029 l internal fuel, which taking 0.8 kg/l for JP-8 (I got density values between 0.775 and 0.840) results in 10.423 kg, 2.2 tons more than the supposed internal fuel of the plane (8,200 kg), makes that sense to you?

The much steeper reduction in drag coefficient when Mach increases is for only individual components like the wing or a generic object. When you have a whole aircraft the total supersonic parasite drag buildup will include things like shockwave interference and total area rule and volume distribution. So even with a dedicated interceptor like F-106 where drag reduction was emphasized over pretty much everything else you don't see that steep kind of drag coefficient reduction of just a component.

XB-70 drag coefficient is low because wing is huge (drag force is drag coefficient times dynamic pressure times wing area), and also that aircraft is optimized to the extreme for supersonic flight. Also small wings is why F-104 drag coefficient is so high even though actual drag is actually very low.

I see, that makes sense. The Su-57 has very big wings and is relatively flat / airfoil shaped overall, but of course I cannot quantify in what final Cd that translates.

~35% increase in thrust will get you from Mach 1.3 to Mach 1.6-1.7 at best. For example YF-22 supercruise speed is Mach 1.43 with YF119 and Mach 1.58 with YF120 which is 20% more powerful because of the YF119 didn't have the bigger fan for increase mass flow of production F119, while YF120 did.

You may be right, maybe the Su-57 has a better aero than thought and reaches more than M 1.3 with current engines, if you check I assumed up to M 1.5 in my first post. But my idea is not to produce accurate quantitative values, because that would be absurd given I am no expert and don't have the necessary data. I am only meeting the dots between what makes sense from a program point of view and what known evidence and official claims support, to reach a qualitative estimation. That would be: supercruising available with current engine but with speed values well below those of F-22, with second stage engine cruising speed equal or bigger than that of F-22 and actually the real possibility of it being close to 2 M, given the number of aspects in which the Su-57 /izd. 30 design offer advantages vs. F-22/F119.

Going to your data and trying to understand your view:

- How did serial F-22 managed to reach cruising speed of M 1.8, given the values you refer for YF-22? Engines were improved massively or drag reduced also massively?
- What is your expectation regarding cruising design speed of a mature Su-57, considering the data already provided by Marchukov?
- How do you make sense out of the fact that Russia decides to produce a new engine, while still developing the 117, in a sequence that does not even allow it to pay-off? My take is that the 117 is the B-plan or risk reduction measure for the program, that will flow into the Flankers in the future, and which covers the eventual failure of the izd. 30 to deliver. But Russian sources are quite consistent considering that supercruise is a crucial requirement of the 5G planes and identifying that with variable cycle, so I assume that from the beginning the idea was to have an engine pretty much like the izd. 20 but in the appropriate size and with modern technology, which is my understanding of the izd. 30 in few words.

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https://vpk.name/news/317381_v_rossii_nachalos_proizvodstvo_raketonosca_pak_da.html I guess the project is no longer going to be treated like a meme on this board.:applause:

Russian enterprises have begun production of the promising missile carrier PAK DA.

- The Ministry of Defense approved all the technical requirements for the aircraft. Work on the creation of PAK YES has been deployed in a timely manner at Tupolev and at cooperative enterprises, Denis Manturov, head of the RF Ministry of Industry and Trade, told Interfax.

The new bomber-missile carrier will replace the current family of long-range aircraft in the troops: Tu-22M, Tu-95 and Tu-160. PAK DA is designed according to the “flying wing” scheme using stealth technologies. It will be subsonic, the main purpose of the aircraft will be delivery to the launch point of a rocket with artificial intelligence. Depending on the tactical situation, the ammunition will determine when, where, and on what route to fly.

The engine for PAK DA is created by the United Engine Corporation. According to open data, the power plant will provide traction 23 ton-force.

Tests of the missile carrier will be held at the Tupolev base near Moscow in Zhukovsky. Earlier, the head of PJSC "Tupolev" Alexander Konyukhov said that the rolling out of the prototype is scheduled for 2021-2022.

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https://www.kret.com/media/press/kret-primet-uchastie-v-sankt-peterburgskom-arkticheskom-kongresse/ There website is back up.

"KRET will take part in the St. Petersburg Arctic Congress
Avangard OJSC is a part of KRET JSC (part of Rostec State Corporation) will present its solutions for the development of the Arctic zone of the Russian Federation at the St. Petersburg Arctic Congress “The Arctic - Territory of Association of Competencies”.
On August 29, the LENPOLIGRAFMASH congress center will host the St. Petersburg Arctic Congress "The Arctic - the Territory of the Association of Competencies", organized by the St. Petersburg Committee for Arctic Affairs."

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Do you have sources for the claim in bold letters? While the reduced number of stages is coherent with claimed easier maintenance, the engines of the Al-31F family are among the ones with better fuel economy. Izd. 117 has essentially state of the art combustion, they would not get a serious improvement in TSFC unless they reduce the BPR, and that makes little sense if you want to produce a high specific thrust engine. Also the maintenance of the 117S is much better than old Al31F with 4,000 h operative life, I don't have the data for the 117 but considering it is the premium, non-export version of the 117S, I would assume it is not worse in that parameter either. Furthermore, Marchukov said izd. 30 keeps the TSFC of the AL-31F, so no apparent improvements are to be expected there. The achievement is to have the specific thrust of a turbojet and the TSFC of a relatively high BPR turbofan.

It may be from Piotr Butowski article, I'll try to find where I read it. But I know one of the goals is for izd.30 to be cheaper to buy and run.

The tank capacity shown in the picture by paralay shows a total 13,029 l internal fuel, which taking 0.8 kg/l for JP-8 (I got density values between 0.775 and 0.840) results in 10.423 kg, 2.2 tons more than the supposed internal fuel of the plane (8,200 kg), makes that sense to you?

From what djcross said the 8,200 kg fuel commonly stated may be weight limit for runway operations and it can carry more when refueled from the air.

You may be right, maybe the Su-57 has a better aero than thought and reaches more than M 1.3 with current engines, if you check I assumed up to M 1.5 in my first post. But my idea is not to produce accurate quantitative values, because that would be absurd given I am no expert and don't have the necessary data. I am only meeting the dots between what makes sense from a program point of view and what known evidence and official claims support, to reach a qualitative estimation. That would be: supercruising available with current engine but with speed values well below those of F-22, with second stage engine cruising speed equal or bigger than that of F-22 and actually the real possibility of it being close to 2 M, given the number of aspects in which the Su-57 /izd. 30 design offer advantages vs. F-22/F119.

Aircraft design is not contest to see which has better numbers. They're designing aircraft to meet their requirements, not to match or exceed another aircraft number for number. So what if F-22 can reach that speed without afterburner? Why does that matter, and would simply getting that "supercruise" speed even relevant? Besides, just because F-22 can go that fast without afterburner doesn't mean that's the normal supercruise speed since that's not the design speed and its very inefficient there even without afterburner. Even F-22 max speed is probably below F-15, but it doesn't matter for the F-22 either.

Going to your data and trying to understand your view:

- How did serial F-22 managed to reach cruising speed of M 1.8, given the values you refer for YF-22? Engines were improved massively or drag reduced also massively?
- What is your expectation regarding cruising design speed of a mature Su-57, considering the data already provided by Marchukov?
- How do you make sense out of the fact that Russia decides to produce a new engine, while still developing the 117, in a sequence that does not even allow it to pay-off? My take is that the 117 is the B-plan or risk reduction measure for the program, that will flow into the Flankers in the future, and which covers the eventual failure of the izd. 30 to deliver. But Russian sources are quite consistent considering that supercruise is a crucial requirement of the 5G planes and identifying that with variable cycle, so I assume that from the beginning the idea was to have an engine pretty much like the izd. 20 but in the appropriate size and with modern technology, which is my understanding of the izd. 30 in few words.

Again just because F-22 can reach Mach 1.8 without afterburners doesn't mean it's cruising there. But max supercruise speed is better than YF-22 because the production F-22 has better area ruling, especially in the rear fuselage where it's much slimmer than YF-22, so better area ruling. For "mature" Su-57 the supercruise speed is probably similar to F-22, probably not much difference to really matter. Also Marchukov didn't provide "data", just some general statements that you can't really make conclusions on specific performance numbers on.

The plan of PAK-FA program was always planned to have a Stage 1 and Stage 2 engine, with izd.117 being Stage 1. That is just how Russia (and Soviet Union) did fighter development. For example first Su-27 prototypes used AL-21 instead of the AL-31 for production aircraft. Supercruise is a critical requirement of PAK-FA, but they're not going to define it in terms of F-22 supercruise speed, they'll define it on what they need. And even for development of ATF the requirement was never Mach 1.8 supercruise speed, it was always Mach 1.5. In fact I would say if F-22 supercruise speed was reduced to Mach 1.5, but it got better range, it would have been better aircraft.

Even bypass ratio isn't not always best indicator for "supercruise" speed. For example, F-16C with F110-GE-129 is a bit faster in mil than with F100-PW-229, even though PW-229 has much lower bypass ratio.

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F-22 fuel system

F-1A: 380.8 gal (2551.4 lbs; 1157.3kg)
F-1B: 323.6 gal (1558.4 lbs; 706.9kg)
F-2: 710.8 gal (4762.4 lbs; 2160.2kg)
A-1: 380.8 gal (2551.4 lbs; 1157.3kg) x2
A-2: 375.3 gal (2514.5 lbs; 1140.6kg) x2
A-3: 77.3 gal (517.9 lbs; 234.9kg) x2

Total = 3082 gal (20,649.4 lbs; 9366.5 kg)
2 х 592.0 gal (2 х 1799.09 кг) = 3598,18 kg

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It may be from Piotr Butowski article, I'll try to find where I read it. But I know one of the goals is for izd.30 to be cheaper to buy and run.

No dispute re. maintenance, re. fuel consumption I have my doubts due to the reason named above.

From what djcross said the 8,200 kg fuel commonly stated may be weight limit for runway operations and it can carry more when refueled from the air.

Are there any sources available for this claim? It sounds decidedly weird to me that a plane with MTOW of 38 tons cannot take-off with the full internal fuel @ <30 tons, but who knows...


Aircraft design is not contest to see which has better numbers. They're designing aircraft to meet their requirements, not to match or exceed another aircraft number for number. So what if F-22 can reach that speed without afterburner? Why does that matter, and would simply getting that "supercruise" speed even relevant? Besides, just because F-22 can go that fast without afterburner doesn't mean that's the normal supercruise speed since that's not the design speed and its very inefficient there even without afterburner. Even F-22 max speed is probably below F-15, but it doesn't matter for the F-22 either.
+
Again just because F-22 can reach Mach 1.8 without afterburners doesn't mean it's cruising there. But max supercruise speed is better than YF-22 because the production F-22 has better area ruling, especially in the rear fuselage where it's much slimmer than YF-22, so better area ruling.

While I very much agree that national defence goes a bit further than a pure cock measuring contest, in the end the required capabilities of a new weapons systems are determined by the level of the threat. F-15 as a response to MiG-25, Su-27 as a response to F-15 and so on until PAK-FA. It is simply unavoidable for the VKS to look at what US (F-22) can do in order to counter it. In order to get favourable match statistics, they need to avoid weak spots in each and every one of the aspects. You can reflect on the program and the plane's features to see this holds true for almost all thinkable parameters, because relying on tactics or supporting assets instead of the individual system's capability is not a very robust way of planing force. In terms of cruising speed as said it is not only F-22 that should be of concern, but the newer platforms propelled by adaptive engines, which will be in the best conditions for a very effective supercruise.

> Why F-22's cruise speed matters? Because it allows to reduce engagement chances for the enemy and increases the effectiveness of the own missiles and in general, an advantage to control the engagements. Do we agree on this or am I missing something important? Why is supercruise a crucial requirement of 5G?

> Design speed of the F-22: you say that the series design was modified in order to get better area ruling than the YF-22, if I got it right. Was this done to get better fuel consumption and the increase in cruising speed was circumstantial? Little probable, since you claim the redesign reduced the fuel capacity... In any case it is obvious that if cruising fast is good, the faster you can do it the better, and the more future-proof your design will be. This means increased TSFC of course, but that makes part of the deal once you go for supersonic cruising. A F-22 deployed for CAP in ME for example is not compelled to cruise at 1.8 M, facing peer-level aircraft/SAMs in a high intensity conflict it would be different I am sure!


For "mature" Su-57 the supercruise speed is probably similar to F-22, probably not much difference to really matter.

Thanks for your take on that. I am not implying it will make much of a difference, but probably coming later VKS prefers being a bit in front than a bit behind. The design reserve re. F-22 (in terms of wing sweep, intake size / design) points to them not willing to fall short of further US developments.

Also Marchukov didn't provide "data", just some general statements that you can't really make conclusions on specific performance numbers on.

Agree, as said this is only about qualitative estimations as in "equal or higher than" and so on. For instance, he said the low TSFC of AL-31F will be preserved. He also said specific thrust is highest. This should allow for a relative positioning of the izd. 30 compared to other types and what is the intent of Russia when developing an engine of such characteristics. They never give concrete numbers in general, and with reason.


The plan of PAK-FA program was always planned to have a Stage 1 and Stage 2 engine, with izd.117 being Stage 1. That is just how Russia (and Soviet Union) did fighter development. For example first Su-27 prototypes used AL-21 instead of the AL-31 for production aircraft.

This is done when you are late with your engine, which has been the case with a number of Russian and Soviet programs. With the MFI they invested heavily and early in order to avoid that, but then the program failed and they saw themselves in the same difficult situation again with the PAK-FA. It is IMHO not a desired or reasonable practice, because it creates unnecessary expenses and efforts (for instance by creating production lines twice, which is extremely costly). Only in this case I think the 117 will be used in the Flanker fleet, by which they minimize the downsides of this approach.

Supercruise is a critical requirement of PAK-FA, but they're not going to define it in terms of F-22 supercruise speed, they'll define it on what they need. And even for development of ATF the requirement was never Mach 1.8 supercruise speed, it was always Mach 1.5. In fact I would say if F-22 supercruise speed was reduced to Mach 1.5, but it got better range, it would have been better aircraft.

See above, I do think F-22 is the necessary reference against which the PAK-FA is designed in most aspects. On the one hand US is the obvious, existential threat that shapes the whole Russian defensive structure, on the other covering it the rest of possible rivals are covered too.

As to the range remark, I tend to agree, it was strange that US, in no real hurry to field the F-22, decided against the YF120, that would have been the future-safe solution. Now they are vulnerable to the deployment of a similar engine in Russia, and given the work was already done with the izd. 20, they were (IMO) gambling a bit too much there.

Even bypass ratio isn't not always best indicator for "supercruise" speed. For example, F-16C with F110-GE-129 is a bit faster in mil than with F100-PW-229, even though PW-229 has much lower bypass ratio.

I think that claim is not an obvious call, from what I have seen, given the GE has higher airflow and bigger intake too. Even the manufacturer figures can be disputed by experienced tech guys. But I think I get what you mean.

Re. the BPR, obviously is not the only thing that counts but it is pretty much the main driver, all other technological aspects being equal, and unsurprisingly the path used both by Europe and US when developing supercruising aircraft (see low BPR of both F119 and EJ2000) and also the main issue tackled with the new VCEs.

BTW, I was not aware it but it seems the "supercruising" term was coined in the times of the ATF program meaning cruising speed above 1.5 M. I think this interpretation is not universal or has been forgotten, since many claims appeared recently about planes that can "supercruise" just because they sustain > 1 M without AB, which was already common before the advent of the 5G. So to address Austin's remarks, I doubt Su-57 can currently "supercruise" in that strict sense of the word but can probably cruise in supersonic regime already with the 117.

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More Customers Surface for MC-21 as It Debuts at MAKS

https://www.ainonline.com/aviation-news/air-transport/2019-08-28/more-customers-surface-mc-21-it-debuts-maks

All the three of the test aircraft now flying rely on Pratt & Whitney PW1400G turbofans, while the fourth, now under assembly, will feature PD-14s. The Aviadvigatel design house promises a 3 to 5 percent advantage in operational cost per flight hour through lower maintenance compared to the Pratt geared turbofan

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So a high bypass turbofan engine will turn out to be less expensive to maintain than a GTF one ?

Probably would be the same for LEAP versus GTF

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So a high bypass turbofan engine will turn out to be less expensive to maintain than a GTF one ?

Probably would be the same for LEAP versus GTF

The gear assembly in P&W's 1400G series was intended to be good for the expected lifetime of the engine - needing only routine inspections (fairly low cost outweighed by fuel savings). It hasn't worked out that way. So, yes, airlines will probably get better operating costs operating the LEAP series. And you see that - they primarily buy LEAP powered models.

The Russians seem to be expecting CMCs to yield efficiency benefits before a fan gear assembly too. Out of the evolved versions of PD-14, PD-35 and PD-12V are moving ahead (PD-35 for sure will use CMCs and I don't know about PD-12V). You don't ever hear of any progress being done on PD-18R.

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As the Russian would be using variant of PD-14 and even PD-35 for Civil and Military Transport aircraft , I would assume simplicity of maintenance would be a key factor for the military.

Hence sticking to High Bypass Engine would be a key factor and yes the PD-18R GTF wont see light of the day now.

I was expecting at MAKS they would show some data on Fuel Consumption of PD-14 versus PW 14000G

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Just came across this very recent article by Vladimir Karnozov on Russian Engine , At the end of the article there is a comparision between Western and all Russian engine including PS-90 and PD-14

https://www.aex.ru/docs/3/2019/8/26/2950/

Specific fuel consumption, kg / kgf * h for PW 1400G is 0.51
Specific fuel consumption, kg / kgf * h for PD-14 is 0.525

He mentions in that article

Certification MS-21 / PD-14 is planned by mid-2022. According to the calculations of Perm, they beat PW1500 at the cost of a flight hour of 3-5%. Fuel consumption is slightly higher, but the PD-14 has fewer blade stages, which means it is easier and faster to service on the ground.

Surprise to see in that table SaM146 Engine fuel consumption of Superjet 100

Specific fuel consumption, kg / kgf * h is 0.629 which is worse than PS-90A1 ( 0.604 ) and PS-90A2 ( 0.6 )

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[USER="3598"]Austin[/USER] - I don't know if Aviadvigatel has given up on the idea of the geared turbofan. It just seems that they are prioritizing Ceramic Matrix Composites. In the end it may prove to be a useful endeavor. Rolls Royce is taking a shot at it. They are finishing a variant of their new Advance3 engine core that they intend to market in the mid 2020s which will use a planetary geared fan, and which they are branding as UltraFan.

I'll take a look at the site later.

Surprise to see in that table SaM146 Engine fuel consumption of Superjet 100

Specific fuel consumption, kg / kgf * h is 0.629 which is worse than PS-90A1 ( 0.604 ) and PS-90A2 ( 0.6 )

Not much of a surprise - they both have approximately the same BPR (similar propulsive efficiency) but the PS-90A has somewhat higher OPR (better thermal efficiency). For a regional jet engine (which the SaM146 is) fuel burn is less critical than on a main line aircraft because proportionately not as much time is spent in cruise on frequent short hops as opposed to fewer long sectors. Durability and low maintenance cost gain relative importance which favours a cycle with lower pressures and temperatures to keep wear in check and a simple engine architecture to reduce parts count. The PW6000 bespoke-developed for the Airbus A318 is based on the same kind of thinking and adopts a virtually identical configuration (except scaled up to higher thrust, matching its larger airframe application) and very similar thermodynamic parameters.

By and large, this approach seems to have delivered the desired results - the SaM146 is claimed to achieve an engine-related dispatch reliability of 99.9% (i.e. only 0.1% of flights are cancelled due to an engine breakdown). Where the severe issues plaguing the fleets of Western customers Interjet & Cityjet stem from is poor parts supply - i.e. when an engine is down for scheduled maintenance or does fail once in a blue moon, spares are frequently unavailable. This will of course ground the aircraft just the same and hit the airline's finances every bit as badly as an engine that keeps malfunctioning on-wing all the time - a sound design marred by insufficient support infrastructure. It also explains why Interjet were so happy with their SSJs initially and able to achieve Airbus/Boeing-level overall dispatch reliability of up to 99.7% - everything was fine until the engines came up for maintenance the first time and started ageing a bit.

And it's not like the Russian side of the PowerJet consortium which builds the SaM146 owns all of the mess either - some of the problems are squarely Safran's responsibility:

https://airlinerwatch.com/sukhoi-superjet-underperforms-due-to-a-design-flaw-in-the-engines/

Fortunately, these issues are now being addressed (not a given, as Safran was reluctant to put in an effort because the lacklustre sales performance of the SSJ made the prospect economically unattractive to them - Catch 22):

https://www.flightglobal.com/news/articles/analysis-rostec-funds-give-lift-to-uecs-civilian-p-458905/

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Not only that, but it seems a good portion of this shortage comes, interestingly enough, because of some US vendors that are not increasing their output:

https://www.ainonline.com/aviation-news/air-transport/2019-07-22/safran-urges-russia-make-substitutes-us-engine-parts

For Russia the path is clear, create the PD-8 and say goodbye both to an extremely expensive Safran and to their unsurprisingly unwilling US suppliers.

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As PD-8 will have higher BPR 7-8 over SaM146 4.5 we can also expect better fuel efficiency.

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So, what is going on with this strange MiG-35 display @ MAKS:

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