Su-27 STR graph and fuel

[CypherS]

This graph for the Su-27 with 2 R-73 and 2 R-27 at 50% fuel says that the maximum STR is around 21 deg/sec. I have not been able to achieve these numbers is DCS, instead the max STR I get is around 19ish, however if I drop the fuel to 30% I do indeed get these numbers (up to 20.3) as STR.

 

I can't remember where but I read that the claimed 50% is without the wing tanks as those are considered external tanks. Is this valid?

 

Edited July 6, 2018 by CypherS

[DarkFire]

This graph for the Su-27 with 2 R-73 and 2 R-27 at 50% fuel says that the maximum STR is around 21 deg/sec. I have not been able to achieve these numbers is DCS, instead the max STR I get is around 19ish, however if I drop the fuel to 30% I do indeed get these numbers (up to 20.3) as STR.

 

I can't remember where but I read that the claimed 50% is without the wing tanks as those are considered external tanks. Is this valid?

 

If memory serves all the plots for the Su-27 are done with an all-up weight of 21,400 Kg which should roughly equate to 30% fuel, 2 x R-73 and 2 x R-27R. I would imagine that the wing tanks would be empty at 30% fuel.

 

I've never seen anything which considers the wing tanks to be anything other than part of the total fuel load. That being said, The Su-27SM and any more modern variants do have 2 x wet wing pylons, so maybe that's where the 'no external fuel' thing comes from.

 

Amusing that the graph plots the Su-27 against the Tornado F2 which was a turkey of an aircraft if ever there was one, with it's 'blue concrete' radar :doh:

 

Edited to add: That's a weird graph. Everything I've seen indicates that the corner speed should be around 780 Km/h yet the plot has it at around 950. Interesting :geek:

 

Further edit: Assuming a full gunpad & expendables, 30% fuel with 2 x R-73 and 2 x R-27R results in an all-up weight of 21,193 Kg. 21,400 is achieved with 32.5% fuel.

Edited July 7, 2018 by DarkFire
Extra information.

[CypherS]

If memory serves all the plots for the Su-27 are done with an all-up weight of 21,400 Kg which should roughly equate to 30% fuel, 2 x R-73 and 2 x R-27R. I would imagine that the wing tanks would be empty at 30% fuel.

 

I've never seen anything which considers the wing tanks to be anything other than part of the total fuel load. That being said, The Su-27SM and any more modern variants do have 2 x wet wing pylons, so maybe that's where the 'no external fuel' thing comes from.

 

Amusing that the graph plots the Su-27 against the Tornado F2 which was a turkey of an aircraft if ever there was one, with it's 'blue concrete' radar :doh:

 

Edited to add: That's a weird graph. Everything I've seen indicates that the corner speed should be around 780 Km/h yet the plot has it at around 950. Interesting :geek:

 

Further edit: Assuming a full gunpad & expendables, 30% fuel with 2 x R-73 and 2 x R-27R results in an all-up weight of 21,193 Kg. 21,400 is achieved with 32.5% fuel.

 

I see, so it isn't 50% fuel. Which begs the question, at such fuel levels should the pilot be engaged in a knife fight where he needs wet power almost all the time?

 

if the answer is no, then is the Su-27 really a superior dogfighter given that a pilot will not engage in a dogfight at such low fuel levels?

[Knives]

This is only one curve. But what about the other curves at different fuel level?

 

Noting that. Every time you fire a missile, your weight is reduced. So most probably when you are in WVR, the R-27 are already gone. So your weight and the aerodynamic of the plane is more better even if you are at 50% fuel.

 

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[GGTharos]

Correct, it isn't 50% fuel level - it's 50% of 'basic fuel' which IIRC is tank 1 and tank 4.

 

 

9000-10000lbs of fuel is nothing to sneeze at. It's not at all a low fuel level. The long dogfights are mostly a game thing.

 

 

 

I see, so it isn't 50% fuel. Which begs the question, at such fuel levels should the pilot be engaged in a knife fight where he needs wet power almost all the time?

 

if the answer is no, then is the Su-27 really a superior dogfighter given that a pilot will not engage in a dogfight at such low fuel levels?

[CypherS]

Correct, it isn't 50% fuel level - it's 50% of 'basic fuel' which IIRC is tank 1 and tank 4.

 

 

9000-10000lbs of fuel is nothing to sneeze at. It's not at all a low fuel level. The long dogfights are mostly a game thing.

 

Alright, so in usual cases the Su-27 and J-11 are fueled to 60% is that correct?

[GGTharos]

That is what it sounds like, but it probably depends on the mission profile. Since the flanker wasn't air-refuelable at first, a maritime patrol mission would probably see it fully fueled.

[DarkFire]

I think the performance calculations were aimed at specific circumstances. Take the loadout mentioned here for example: 30% of maximum fuel with 2 x R-73 & 2 x R-27R looks very much like a relatively short range intercept platform, or alternatively a longer range escort mission that has already engaged in BVR combat prior to a WVR engagement.

 

I agree with GGTharos - 30% of maximum fuel would be roughly 2,735 Kg of fuel. For a reasonably high altitude cruise this would still give you a range of roughly 450 Km.