Fuel consumption?

[Buzpilot]

Su25 use fuel way too fast, maybe 200% rate from what I could read.

Kamov.net rate Su25 to have a range at 1350km on internal fuel only, probably clean install. DCS Encyclopedia have a Max range 1250.

http://www.kamov.net/versus/a-10-vs-su-25/

 

The first mission in Su-25 Campaign, have a route at about total 400km.

After doing a couple runs with laser missiles, I was almost empty with fuel, first I thought I had a fuel leak, but running the same path in editor, I could not return to base without loosing fuel.

I read somwhere it should have 375km combat range, total 750km, but it's nowhere near that.

It's possible to finish the mission one in Su25 Campaign using at least one extra fuel tank, but I think there still is a bug in fuel economy.

 

Edit;This was in 1.2.7 , and same in 1.2.6

Edited January 12, 2014 by Buzpilot

[Frostie]

Have you tried cruising 80-85% instead of max power? And also add external fuel tanks.

[Buzpilot]

Have you tried cruising 80-85% instead of max power? And also add external fuel tanks.

 

First time in campaign,I tried to keep up with the strike force, they probably run 100% all the way in, could not reach them :)

The test run in Editor I run only 550km/h (checked replay, about 89%, too large to attach), and still need 2 fuel tanks. (I could manage barely with only one, but no room for error then)

FC3-Su-25 Fuel test.miz

Edited January 12, 2014 by Buzpilot

[BavarianPilot]

And what was your altitude?

[Buzpilot]

And what was your altitude?

 

1500m

Edited January 12, 2014 by Buzpilot

[lmp]

Sukhoi's site lists the Su-25K's range at 500km (sea level) to 1000km ("at height" - they doesn't specify what height, but I assume they mean at the aircraft's service ceiling of 7km) without any external stores (link). Add in a combat load, inefficient power setting and some maneuvering in the target area and I can see how that can go below 500km. I can't say if the fuel consumption is right in a game, but be aware that range can change very dramatically based on a lot of factors.

[Buzpilot]

Sukhoi's site lists the Su-25K's range at 500km (sea level) to 1000km ("at height" - they doesn't specify what height, but I assume they mean at the aircraft's service ceiling of 7km) without any external stores (link). Add in a combat load, inefficient power setting and some maneuvering in the target area and I can see how that can go below 500km. I can't say if the fuel consumption is right in a game, but be aware that range can change very dramatically based on a lot of factors.

 

A-10 Thunderbolt II has 10-15% better range, but on same waypoints and altitude as Su-25 ,the A-10 used less than 50% fuel, 11,100-6,400pnd both planes had 97% load from start to target. You are sure the Su-25 use that much less fuel at altitude?

Then at low altitude combat missions, the A-10 can fly 4 times longer. And mission makers on Su-25 Campaign should put in Fuel tanks in default loadout.

 

The Fuel test mission i made are same waypoints as Su25 Campaign mission 1, about 400km.

Edited January 12, 2014 by Buzpilot

[lmp]

No, I'm not sure. As I said, I don't know if the game is right about this or not. I'm just suggesting we don't jump to conclusion. We would need at least some fuel consumption tables or charts that would tell us how much fuel the aircraft should burn at a given speed/power setting at a given altitude with a given payload. Then we would need to run some tests against that data. Unfortunately, I don't know where to look for those tables.

 

Actually, it would be pretty cool if ED provided various performance tables (and not just endurance/fuel consumption) for at least the AFM aircraft. It would help those who like to fly the airplane realistically and know all its limits and at the same time, it wouldn't make life harder for the casual pilots.

[falcon_120]

Take into account that in this mission we use a very low flight profile, which is very fuel inneficient. If you fly higher like 5000m your fuel consuption would be much lower.

[Buzpilot]

Take into account that in this mission we use a very low flight profile, which is very fuel inneficient. If you fly higher like 5000m your fuel consuption would be much lower.

 

Why do you repeat this, we already know?

It's only 400km we are talking about, even climbing to 5000m with target at 200km will use lot of fuel.

 

Edited January 13, 2014 by Buzpilot

[GGTharos]

This combat range involves high-altitude flight.

 

A jet engine can easily burn 2-3x the amount of fuel at low altitude compared to high altitude since it's developing more power AND pushing the aircraft through denser air.

 

Other factors include, as mentioned, inefficient throttle setting, and also stores drag. Drag is a huge factor in fuel consumption - it makes you use higher throttle for the same speed or, if there's enough drag, for a lower speed.

 

Having said that, it's entirely possible that some stores may have incorrectly high or low drag, the fuel consumption is not too accurate (but I have my doubts about this) etc.

 

As for A-10, it uses high-bypass, fuel efficient turbo-fans, so it will probably burn less fuel than a turbojet that develops similar thrust.

 

The first mission in Su-25 Campaign, have a route at about total 400km.

I read somwhere it should have 375km combat range, total 750km, but it's nowhere near that.

[Buzpilot]

As for A-10, it uses high-bypass, fuel efficient turbo-fans, so it will probably burn less fuel than a turbojet that develops similar thrust.

 

I know this, but 400% better loiter capacity, seems off the scale.

 

One more indication something is calculated wrong.

Fuel capacity should be 3500Kg internally, not 2900Kg like now.( 1.2.6 and 1.2.7)

 

[GGTharos]

I know this, but 400% better loiter capacity, seems off the scale.

 

No, the A-10 is designed to have this loiter capacity.

 

One more indication something is calculated wrong.

Fuel capacity should be 3500Kg internally, not 2900Kg like now.( 1.2.6 and 1.2.7)

 

That may be. Like I said, I'm not saying that there isn't a bug. It is hard for us to know though if we don't have the fuel consumption charts.

[Buzpilot]

I'm starting to think, the Su25 in Afghan war, used to fly from airports empty, and used temporary fields to land and refuel/rearm, less than 100km from targets.

[Dr_Arrow]

I know this, but 400% better loiter capacity, seems off the scale.

 

One more indication something is calculated wrong.

Fuel capacity should be 3500Kg internally, not 2900Kg like now.( 1.2.6 and 1.2.7)

 

 

Why should the fuel capacity be 3500 kg? Standard Su-25 without droptanks has 2750 Kg of internal fuel, the T version is at 3800kg. These figures in DCS are certainly correct.

[Buzpilot]

Why should the fuel capacity be 3500 kg? Standard Su-25 without droptanks has 2750 Kg of internal fuel, the T version is at 3800kg. These figures in DCS are certainly correct.

 

I see, 100% in editor tells me 2835Kg.

Then Su25 is kind of useless in reality, without externals?

And a full stacked Su25 with weapons on all pylons is probably only propaganda?

Edited January 13, 2014 by Buzpilot

[Buzpilot]

Could be a different version of Su-25?

 

Edit; Aha, could be my mistake 3600L is probably 2835Kg

 

http://www.airforce-technology.com/projects/su25/

 

Engines

 

The Russian Air Force Su-25 aircraft is powered by two Soyuz / Gavrilov R-195s turbojet engines rated at 44.18kN. Cooling air is introduced at the end of the tail cone to reduce the temperature of the exhaust gases and minimise the infrared signature of the aircraft.

The aircraft is equipped with self-sealing, foam-filled fuel tanks with a total fuel capacity of 3,600l. The range of the aircraft can be extended by the provision of four PTB-1500 external fuel tanks, which are carried on the underwing pylons.

Performance

 

The Su-25 can climb at the rate of 58m/s. The maximum speed of the aircraft is 950km/h. The combat radius and ferry range of the aircraft are 375km and 7,500km respectively. The normal range of the Su-25 is 750km. The service ceiling is 7,000m.

The take-off and landing roll of the Su-25 are 750m and 600m respectively. The aircraft weighs around 10,740kg and its maximum take-off weight is 17,600kg.

[esb77]

The Su-25 and A-10 are similar in combat role, but not in endurance. Why? Take a quick look at the airframes.

 

The Su-25 is built to be fast, the A-10 is built to be maneuverable at very low speeds. That's even before you account for engine differences. Same sort of wing shape difference you'd see between a falcon and a soaring bird like an eagle.

 

You should be able to get about 600km range at sea level with 2900 kg of fuel and a full weapons load, based on in game testing I did in version 1.2.4. Perhaps a bit more range depending on how you fly. That's with throttle set at 90% or so.

[Buzpilot]

You should be able to get about 600km range at sea level with 2900 kg of fuel and a full weapons load, based on in game testing I did in version 1.2.4. Perhaps a bit more range depending on how you fly. That's with throttle set at 90% or so.

 

1.2.4 was before the new AFM, I could fly 600km. But needed to climb above 5000m, and 93-94% to keep aoa below 10, after 400km i throttle down to 85% and started decending 4-5 degrees. Jettisoned Weapons at 500kg fuel left.

Krashnodar Pashkovskiy - Tblisi-Lochini ca 600km

 

But now at sea level, it's only 250km, and fuel empty. Edit; I guess that one was 95-100%, I did one run at 500m 85%, and managed 400km.

It should mean the Campaign mission one for Su25 is possible if you keep max 85%, and only one attack run.

FC3-Su-25 Range test.miz

Edited January 13, 2014 by Buzpilot

[GGTharos]

When they say 'combat radius 350km' or whatever it was, what kind of payload are they talking about?

 

In all cases when I look at aircraft manuals, the range is not just 'this or this', it's this weight with this drag index (or specific payload) and flight profile.

[Buzpilot]

When they say 'combat radius 350km' or whatever it was, what kind of payload are they talking about?

 

In all cases when I look at aircraft manuals, the range is not just 'this or this', it's this weight with this drag index (or specific payload) and flight profile.

 

I used the default mission payload; 2-25L*2, KH-25ML*2, RBK-500*2, B-8MI*2, R-60M*2 .

Edited January 13, 2014 by Buzpilot

[GGTharos]

That's pretty heavy and draggy I'd say ... I bet the 350km is with two rocket pods :) Or two fuel tanks.

[Buzpilot]

That's pretty heavy and draggy I'd say ... I bet the 350km is with two rocket pods :) Or two fuel tanks.

 

It said combat radius, making it total 700km, but it could be possible with only 2 rocketpods at altitude above 5000m.

The more testing I do, I tend to agree it seem not too far off. Could be it's only the real consumption is in litres, and game consume kg.

Edited January 13, 2014 by Buzpilot

[Dr_Arrow]

I used the default mission payload; 2-25L*2, KH-25ML*2, RBK-500*2, B-8MI*2, R-60M*2 .

 

This is absolutely unrealistic loadout - in real life usualy 4xS-8 pods are carried or 4xFAB-500 or two guided missiles. The figures you are giving are absolutely realistic and I don't think the game would mistake liters for kilograms - all specific engine fuel consumption are using kg or lb in calculations, liters are never used.

[Dima89]

This is absolutely unrealistic loadout - in real life usualy 4xS-8 pods are carried or 4xFAB-500 or two guided missiles. The figures you are giving are absolutely realistic and I don't think the game would mistake liters for kilograms - all specific engine fuel consumption are using kg or lb in calculations, liters are never used.

 

Is it possible to see what you are referencing for that? I don't say it to second guess you, I would like to see for my own load outs :)