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RD-93 fuel flow and efficiency.


Airhunter

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I have recently done some tests on the max AB times and fuel economies of various jets in DCS and have come across two outliers in my testing. One of which is the JF-17, powered by the RD-93. It has a longer full afterburner time with much less internal fuel than comparable single engine aircraft, the lowest fuel flow of any comparable single engine engine aircraft and one of the lowest TSFC's of any comparable jet.

 

Below are my findings as well as the test conditions.

 

abtimeook6s.png

 

Keep in mind, for the fuel flow chart you'd have to divide the two-engine aircraft values by two to have a direct comparison.

 

fuelflowkfjgz.png

 

zfwvsinternalv1j2d.png

 

tsfc_comparisoneojcl.png

 

From what I've gathered from public sources, the RD-93 is basically the RD-33 with a repositioned accessory gearbox, HIGHER fuel flow and possibly an increased pressure ratio to allow the higher engine rating of roughly 22K lbf, thus reducing maximum engine life.

The RD-33 is a fairly old engine and its performance is widely available and known. Specifically a TSFC of 0,77 with full dry thrust and 2,05 in full afterburner are stated. Currently your RD-93 simulation exhibits veeeery different performance from the RD-33, like, it's not even remotely close. Specifically a fuel flow in max AB of 29910 lbs/h as opposed to roughly 45400 lbs/h of a single RD-33 in the same test conditions. Moreover a TSFC of an unmatched value of 1,35 in full afterburner, while it should technically be even higher than the RD-33's. Since DCS modules are supposedly built on publically available data, what sources have you guys used to model this engine if not data for the RD-33? Could you please show me factual evidence and data of the RD-93's performance as there isn't anything out there specifically for the 93? Because right now such en efficiency is very hard to believe and outmatches even the most modern turbofan engines available.

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Thanks for your feedback and this will soon be revisited.

 

In addition to your info, the TSFC of 2.05 actually happens at H=0 & M=0 with uninstalled engine, in training-combat mode of RD-93. Expect a surge to 2.40 when at H=0 & M=1.0.

 

With combat mode, this would be 2.08 (H=0 & M=0).


Edited by LJQCN101

EFM / FCS developer, Deka Ironwork Simulations.

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Thanks for your feedback and this will soon be revisited.

 

In addition to your info, the TSFC of 2.05 actually happens at H=0 & M=0 with uninstalled engine, in training-combat mode of RD-93. Expect a surge to 2.40 when at H=0 & M=1.0.

 

With combat mode, this would be 2.08 (H=0 & M=0).

 

Thanks for the feedback! Those values sure make a lot more sense. 2.05 at M=0 is rather significant hah.

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Fuel flow depends on speed and altitude,at the same altitude, faster means more fuel flow,Fulcrum is so much faster than Thunder.

 

Correct, theres a mostly linear increase with Mach but its low single decimal digits if anything in those supersonic regions (in terms of TSFC). However the static values should be very comparable, also various other engine types in similar conditions as well. No public source will really give you the exact conditions their values are based on. Most other DCS modules are within the rough ballpark anyway, hence my concern. As you can see my measured TSFC of 2.48 was at M2.3 as opposed to the 2.05 on a supposed static test at sea level.

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What mode did you have the RD-93 in in your tests?

 

I've noticed higher fuel flow when in "combat" mode rather then default or training mode.

 

fuelflow.jpg

 

Just using your test data to make some comparisons between the fuel flow, speed, and fuel capacity between the Mig-29 and Jiff

 

Fuel flow appears to be almost identical (single engine comparison), Its just one plane is alot faster then the other.


Edited by Kazansky222

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What mode did you have the RD-93 in in your tests?

 

I've noticed higher fuel flow when in "combat" mode rather then default or training mode.

 

fuelflow.jpg

 

Just using your test data to make some comparisons between the fuel flow, speed, and fuel capacity between the Mig-29 and Jiff

 

Fuel flow appears to be almost identical (single engine comparison), Its just one plane is alot faster then the other.

 

I had it in combat, 101% N1. Yes the 29 will be faster, obviously but you can't really make a legit full AB comparison at the same speed since most aircraft will perform differently. The F-16C does the same speed at that alt in full AB, so that's at least a good reference point. Also TSFC values dont lie, it's literally fuel flow devided by thrust (single engine). But I'm glad Deka has aknowledged this and will adjust it, becuase currently the JF17 is like the most efficient jet out there, trumping Eagles and Tomcats.

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I had it in combat, 101% N1. Yes the 29 will be faster, obviously but you can't really make a legit full AB comparison at the same speed since most aircraft will perform differently. The F-16C does the same speed at that alt in full AB, so that's at least a good reference point. Also TSFC values dont lie, it's literally fuel flow devided by thrust (single engine). But I'm glad Deka has aknowledged this and will adjust it, becuase currently the JF17 is like the most efficient jet out there, trumping Eagles and Tomcats.

 

I see what you're saying, but I mean, But you have to admit, it is odd that when you simulate single engine fuel flow at the Mig-29 design speed and JF17 design speed, provided by your time data, that fuel flow seems to match up almost perfectly with the RD-93 when speed is taken into account.

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I see what you're saying, but I mean, But you have to admit, it is odd that when you simulate single engine fuel flow at the Mig-29 design speed and JF17 design speed, provided by your time data, that fuel flow seems to match up almost perfectly with the RD-93 when speed is taken into account.

 

 

I'm sorry but you just can't make calculations in percentage relations like that. Speed has a linear relation to TFSC and at high M numbers the increase should be roughly in low decimals (.2 - .4). Go read up on TSFC and typical values for modern turbofan jet engines. As a sidenote, the RD33 has a 18k thrust rating and the RD-93 a 22k rating.

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I had it in combat, 101% N1. Yes the 29 will be faster, obviously but you can't really make a legit full AB comparison at the same speed since most aircraft will perform differently. The F-16C does the same speed at that alt in full AB, so that's at least a good reference point. Also TSFC values dont lie, it's literally fuel flow devided by thrust (single engine). But I'm glad Deka has aknowledged this and will adjust it, becuase currently the JF17 is like the most efficient jet out there, trumping Eagles and Tomcats.

 

 

We DO NOT think our fuel flow is wrong.

We only said we'll check our test result VS public data.

Your test method is horrible, and the test result is way too far from reliable.


Edited by L0op8ack
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I'm sorry but you just can't make calculations in percentage relations like that. Speed has a linear relation to TFSC and at high M numbers the increase should be roughly in low decimals (.2 - .4). Go read up on TSFC and typical values for modern turbofan jet engines. As a sidenote, the RD33 has a 18k thrust rating and the RD-93 a 22k rating.

 

I think an interesting test would be to have a Mig-29 and JF-17 sitting on the ground somewhere, near sea level and another test where they are at the highest airport in the game both with the same amount of fuel onboard say the 5100lbs that the Jiff carries. And have them both siting there with 1 engine running, crank them up to full AB or mil or whatever with the brakes held and let them sit and see who burns out of fuel first. and time it. maybe even try to record the fuel drop rate on the gauges. It would be more of an "apples to apples" seeing as they would both be at zero airspeed, same altitude ect....

 

Now if they are wildly different then there is def something going on. But if they are about the same, like the percentages expression from your time tests then I don't think there is a problem, or at least not a huge one.

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As a sidenote, the RD33 has a 18k thrust rating and the RD-93 a 22k rating.

 

The thrust of 22k lbsf or 10,000kgf actually happens at sea level and M0.85.

 

While at 30,000ft and M1.6, the thrust is only around 7,100 kgf, with a Fuel Flow of 16,500 kg/h. So yeah, the in-game FF should tweak up a bit.

 

But weirdly, when I compared the installed RD-93 fuel flow curve (FF vs alt & mach) to the one in GAF T.O.1MIG-29-1, which is the real life MIG-29G manual (you can find that if you could), I even found the RD-93 a bit more fuel efficient.

 

For comparison, the Mig-29G does 30,000ft & M1.6 at 10.25 kg/sec, which is 36900 kg/h for both engines, so 18,450 kg/h for single engine.

EFM / FCS developer, Deka Ironwork Simulations.

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We DO NOT think our fuel flow is wrong.

We only said we'll check our test result VS public data.

Your test method is horrible, and the test result is way too far from reliable.

 

Please explain yourself? Are you telling me a JF-17 is significantly more fuel efficient than a F-16 or Viggen with significantly less fuel at nearly the same test conditions? More than 10 minutes in max afterburner with 5k lbs of fuel?

 

I think an interesting test would be to have a Mig-29 and JF-17 sitting on the ground somewhere, near sea level and another test where they are at the highest airport in the game both with the same amount of fuel onboard say the 5100lbs that the Jiff carries. And have them both siting there with 1 engine running, crank them up to full AB or mil or whatever with the brakes held and let them sit and see who burns out of fuel first. and time it. maybe even try to record the fuel drop rate on the gauges. It would be more of an "apples to apples" seeing as they would both be at zero airspeed, same altitude ect....

 

Now if they are wildly different then there is def something going on. But if they are about the same, like the percentages expression from your time tests then I don't think there is a problem, or at least not a huge one.

 

Yep, I will do just that and run a static seal level test now.

 

The thrust of 22k lbsf or 10,000kgf actually happens at sea level and M0.85.

 

While at 30,000ft and M1.6, the thrust is only around 7,100 kgf, with a Fuel Flow of 16,500 kg/h. So yeah, the in-game FF should tweak up a bit.

 

But weirdly, when I compared the installed RD-93 fuel flow curve (FF vs alt & mach) to the one in GAF T.O.1MIG-29-1, which is the real life MIG-29G manual (you can find that if you could), I even found the RD-93 a bit more fuel efficient.

 

For comparison, the Mig-29G does 30,000ft & M1.6 at 10.25 kg/sec, which is 36900 kg/h for both engines, so 18,450 kg/h for single engine.

 

Can you please give me the source for your RD-93 data? Since it HAS to be public.

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I bet you would see opposite results at low altitude

 

Funny you said that. I just now did some static tests with the Jeff and 29S. 29S was single engine only. Both jets starting with 5126lbs of internal fuel.

 

screen_200502_1511370fk0o.png

 

screen_200502_152847edjgh.png

 

What I found was the following:

 

JF-17 full AB time (CMBT) until flameout: 09m 41s (resulting in 31760 lbs/h FF)

 

Mig-29S full AB time (single engine) until flameout: 10m 39s (resulting in 28879 lbs/h FF)

 

So my question is now how does an older RD93 design perform 20+ % more efficiently at the same conditions and speeds (30000ft, M1.67, ISA) than a more modern GE F110? Even a 15% increase in economy would require an entirely new generation of engine using new materials and possibly a geared fan.

 

Of course I dont have the exact thrust profile and fuel flow charts of the RD33 at various altitudes and high mach numbers, so I can't really reliably compare them and test them. There also isn't any fuel flow gauge in neither the 29 nor the JF17 to make manual tests possible.

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Please explain yourself? Are you telling me a JF-17 is significantly more fuel efficient than a F-16 or Viggen with significantly less fuel at nearly the same test conditions? More than 10 minutes in max afterburner with 5k lbs of fuel?

 

Yep, I will do just that and run a static seal level test now.

 

Can you please give me the source for your RD-93 data? Since it HAS to be public.

 

 

If you are so self-confident about your test result, find the docs yourself, and check again.

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If you are so self-confident about your test result, find the docs yourself, and check again.

 

There are no "docs" to be found. Please provide your reference as evidence, otherwise those are just claims anyone can make.

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Funny you said that. I just now did some static tests with the Jeff and 29S. 29S was single engine only. Both jets starting with 5126lbs of internal fuel.

 

 

What I found was the following:

 

JF-17 full AB time (CMBT) until flameout: 09m 41s (resulting in 31760 lbs/h FF)

 

Mig-29S full AB time (single engine) until flameout: 10m 39s (resulting in 28879 lbs/h FF)

 

 

So it looks to me like the JF-17 has a high fuel flow in a apples to apples static test. So.... looks accurate to me.

 

Your 30k ft tests are invalid because they are at such radically different speeds. And doesn't account for inlet design which can count for almost half the "thrust" of an engine in depending on design, design speed ect... https://www.grc.nasa.gov/WWW/K-12/airplane/inlet.html for informational purposes.

 

But this one is impossible to fake out. the RD-93 burns more fuel installed in a static test vs the RD-33.

So again, your own results show that its... pretty spot on.


Edited by Kazansky222
added link.

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Air hunter, while something might need tweaks, keep in mind JF-17 should be more efficient then something larger if everything else is the same. The engine is smaller then F110, the plane is around 20-25% lighter then F-16. It is smaller and has less drag. A gallon of fuel does a lot more for smaller plane with a smaller engine and less drag naturally.

 

Your ground test looks about right, becuase the RD-93 short life(both life time and high max FF) likely comes from the fact that they sacrificed MIL power for greater AB thrust.

 

There might be something here, but it being more efficient then a larger plane with a larger engine is not a problem

 

You say it can’t be 15% more efficient then F-16, but it’s more then 15% size/weight/drag difference I’m sure.

 

F110 produces 29,000 lbs and weighs 3980 lbs dry with a diameter of 46.5 inches and length of 181.9 inches. RD-93 produces 22,000 lbs of force at just 2,524 pounds of weight dry, with a 40.94 inch diameter and 166.5 length. A more proper comparison for engine is F404 in Hornet, or Snecma in Mirage

 

Engine has 37% less weight and 24% less thrust

 

For the airframes

F-16 Empty weight: 18,900 lbs

Max takeoff weight: 42,300 lbs

JF-17

Empty weight: 14,520 lbs

Max takeoff weight: 29,762 lbs

 

JF-17 has 23% less empty weight, and almost 30% less max weight


Edited by AeriaGloria
Updated with Thrust numbers from earlier post

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There are no "docs" to be found. Please provide your reference as evidence, otherwise those are just claims anyone can make.

Currently your RD-93 simulation exhibits veeeery different performance from the RD-33, like, it's not even remotely close.

 

 

This is a very serious accusation to a sim team, you need prove it all by yourself, in details.


Edited by L0op8ack
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So my question is now how does an older RD93 design perform 20+ % more efficiently at the same conditions and speeds (30000ft, M1.67, ISA) than a more modern GE F110? Even a 15%

 

From the RD-93 specifications sheet you can find the SFC for the engine is 2.05 kg/kgf*h and the full burner thrust is 8300 kg. This is the test value with the stand along engine. After installation, the SFC will decrease by 25% and the thrust will increase by 16%. These are the value from all different website and you can easily find them.

 

Calculating the FF from public resources: FF = SFC * 0.75 * Thrust * 1.16 * 2.2046 lb = 32634.8 lb/h

 

Your value is 31760 lb/h, there is only 2.7% difference from your value to the real one. You still think this is unrealistic?

 

For example check here: http://www.avia500.ru/eng/production_72

 

The efficiency of the engine does not only depend on the engine itself, it also depends on the inlet design and the nozzel design. If you take out all the engines and test them alone on the test stand, the newer engine might be more efficient than the older one. However, we are talking about combat aircrafts and you need to sacrifice efficiency for other performance, for example for radar cross section. If you put the GE F119 on the table, it might be more fuel efficient than all engines in DCS, however, if you take the F22, it might be less fuel efficient than a lot aircrafts in DCS since it traded in at least 20% of thrust for RCS as far as I know.


Edited by Kumabit
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Can you please give me the source for your RD-93 data? Since it HAS to be public.

 

This assumption is wrong. Most figures from the JF-17 T.O. Dash-1 and RD-93 tech manual like thrust curve/fuel flow curve vs altitude & mach, detailed fuel flow of different cruise settings with different stores etc. are still NOT PUBLIC. We don't just put those docs on the internet by the request of random people.


Edited by LJQCN101

EFM / FCS developer, Deka Ironwork Simulations.

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This is the figure for sea level and M0.55.

 

Are you trying to say "value" instead of "figure"?

 

I am just calculating the value from the resource that I can find and the current ingame SFC for JF17 seems on spot. I don't think the current SFC curve has problem. I am tired of looking at all those posts that people use their imaginary performance to fight against the dev team, and thinking all non-western aircraft should be inefficient and draggy.


Edited by Kumabit
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