Weak Engine Power

[Nedum]

Hello!

I've tested a little bit and I want to know why the full AB thrust is so weak like it is now!

Is it right like it is?

I've tested with a F15C @ 23.000 kg (no weapons, 2 external tanks) and with the Su27 also with 23.000 kg start weight.

With a flying start at full AB + max speed (1420 kph), at 300 meter and an AoA of 45° the Su27 stalls at ~ 25.000 feet.

The same as above and the F15C stalls at ~ 45.000 feet.

All conditions a 100% the same (weather, wind, flight direction, time, etc.).

 

I've had read that the Su27 has a little bit better thrust to weight ratio, so how can this happen and why is the difference so extrem big (20.000 feet)?

 

This was a short test after some display testing with strange behaviors and the feeling of a massive lack of power in each situation.

Is this a Bug or is this like it should be?

[Exorcet]

I put a standard Su-27 (56% fuel, no weapons) into a 45 degree climb and I got to 50,000 ft.

[Ironhand]

Hello!

...and an AoA of 45° the Su27 stalls at ~ 25.000 feet...

Ummm...the Su-27's critical AoA is 31*. At 45*, you're no longer flying. I assume you mean pitch angle of 45*?

 

Somehow, your results don't seem right. I run the your scenario in the AM, if I have time.

 

 

Rich

[x39crazy]

I don't notice any issues until between 11000 and 12000 meters, with a full combat load that is.

[Prefontaine]

What is your climb speed?

 

If you rotate and just point for the moon, you'll probably just achieve the results you posted about.

 

You need to first accelerate to develop excess Ps, and then you can climb dramatically faster -- applies to both MIL power and AB takeoffs.

 

EDIT: and like it's been mentioned before, there's a big difference between climb angle and angle of attack.

[Nedum]

Ummm...the Su-27's critical AoA is 31*. At 45*, you're no longer flying. I assume you mean pitch angle of 45*?

 

Somehow, your results don't seem right. I run the your scenario in the AM, if I have time.

 

 

Rich

 

Yes, you are right, I meant the AoI.

I am at work now. And will test this today again.

If you guys get this high altitudes so easy, there must be something extrem wrong with my game.

I tried both planes at the same angle, with the same weight to fly until they stall. The DCS Su27 loses its good feed round about 1/3 earlier than the F15C.

Perhaps I play another game or my devices are crap (TM Warthog HOTAS)? :huh:

Thrust to weight ratio is all I am talking about.

The Su27 has a little bit better thrust to weight ratio(?), so should the Su27 go up straight to the sky a little bit better as the F15C, but she doens't.

Fly them like rockets straight to the sky (same weight) and look which bird will go higher and then look at the difference between both results.

 

I will test this again today.

[USARStarkey]

You are incorrect about the F-15/Su-27 Thrust. At all heights at equivalent fuel weight the F-15 has a better T/W. Over 10-15,000ft, the F-15 starts to gain a significant advantage. So if you put them into a climb the Eagle will stall later. It is general common knowledge the the Eagle is the climber and the flanker the turner as a generalization

[Ironhand]

...an AoA of 45° the Su27 stalls at ~ 25.000 feet.

I got to 29,300 ft (8930 m) before stalling in a 45* climb. My starting airspeed was a bit slower than yours, though, at 1154 k/h. (There was a hill in the way and I decided I'd might as well start the climb before I hit it.)

[amazingme]

I (used) to enjoy the Flanker but after the latest updates in flight dynamics my opinion changed. There is no more power for the Su and i can easily kill it with the Dora in slow turn fighting because now the Su it's acting very STUPID and UNREALISTIC.

Please restore the previous flight dynamics to the Su.

[Esac_mirmidon]

Really?

 

AI planes don´t have AFM.

[wasserfall]

Well i find the Su27 not stupid and very realistic, you just have to master her than it's a joy to fly:)

[GGTharos]

Lots of opinion here from people who have flown real Su-27's ;)

[Ironhand]

Lots of opinion here from people who have flown real Su-27's ;)

:) OK. I'm going to let my ignorance show. I keep seeing the Su-27's thrust:weight ratio bandied about. My question is always: which weight? Is it a clean aircraft with 50% fuel out of the total 100% possible capacity? Is it something else? Is it something else with the addition of "x" number of missiles hanging off the pylons? I've also seen her combat weight defined as 50% fuel with 4 AAMs. And, then, her thrust:combat weight ratio being 1.1:1.

 

And, finally, is there actually a standard definition of the "weight" when thrust:weight ratios are calculated? Or is it whatever each manufacturer decides it is?

 

 

 

Rich

[GGTharos]

That wasn't addressed at you IH, I think you're doing a great job at trying to test and figure things out.

 

 

Stuff follows: TL:DR at the end.

 

You're right about 'which weight', but overall, the empty F-15C is lighter than the Su-27, and the Su-27 only has a little more thrust than the F-15C.

 

Numbers from Wiki and F-15 -1, but here goes:

 

Empty weight:

 

F-15C: 28500lbs

Su-27: 36000lbs

 

Maximum thrust:

 

F-15C: 50000lbs (yes, the 220's will spit out 25000lbs a piece)

Su-27: 55000lbs

 

Right off the bat, the Su-27 loses by 3000lbs in the TWR arena, and that's if you don't have a drop of fuel left.

 

In a loaded configuration, the Su-27 weighs in at 51000lbs, that's with less than 60% fuel. The F-15 weighs in at around 50000lbs, but it can actually light the cans and fight ... the Su-27 will run dry.

 

This is all mumbo-jumbo of course, because, like you said:

 

TWR is difficult to calculate. It's not only because we don't know 'which weight', but also 'which altitude and speed' and 'what is the thrust output at this speed and altitude'.

 

At medium to high altitudes, the F-15 gains a significant advantage in thrust - apparently the pressure recovery mechanism is at least slightly superior, and the difference this makes is acknowledged in the real flanker manuals as well.

 

You don't really want to get into a turning fight with a flanker as an eagle pilot, but all other things being equal, you've got some advantages up high.

 

This doesn't stop a flanker pilot from performing a hail-mary hook maneuver to lob some 73's at you, but they better hit. :)

 

 

 

TL;DR:

 

TWR comparisons are largely meaningless when the sources were 'something you read about'. Even if you have the official aircraft manuals, it is necessary to look at the point of the envelope (or envelope range) that you want to compare. This envelope consists of the aircraft's gross weight, altitude, and speed. You're usually looking for some Ps curve here, and you might find it. Just don't be suckered into thinking that it tells you the whole story.

Edited January 5, 2015 by GGTharos

[Pilotasso]

The problem of planes feeling underpowered may be a by-product of lack of perception when aircraft is being stressed. You pull the aircraft to it's limits and it falls off the sky with little warning.

 

We need to hear a more pronounced airflow noise change from inside the cockpit along with some shuddering, and changes to the contrails, some axis tuning (you get maximum input with little deflection), things like this that also add to immersion. :)

[TAW_Blaze]

The problem of planes feeling underpowered may be a by-product of lack of perception when aircraft is being stressed. You pull the aircraft to it's limits and it falls off the sky with little warning.

 

We need to hear a more pronounced airflow noise change from inside the cockpit along with some shuddering, and changes to the contrails, some axis tuning (you get maximum input with little deflection), things like this that also add to immersion. :)

 

I agree! I feel like the stall warnings are nowhere near to what they were before PFM on the F-15 for instance. Specifically from the betty side. But I guess the PFM adds to it aswell.

[amazingme]

Is it "normal" that i can kill a su27 with dora (Fw190d) in a low speed turning fight? And not against the AI.. Below 400 km/h it feels like the flanker has no power comparing to the flanker before the last update. It's acting like a prop aircraft..which kinda sux :(

[karambiatos]

Is it "normal" that i can kill a su27 with dora (Fw190d) in a low speed turning fight? And not against the AI.. Below 400 km/h it feels like the flanker has no power comparing to the flanker before the last update. It's acting like a prop aircraft..which kinda sux :(

 

I dont see why you shouldn't be able to kill anything in a WW2 aircraft in a turnfight.

 

the 27 shouldnt be turn fighting you when it has an enormous advantage in climb rate and speed.

[Ironhand]

That wasn't addressed at you IH, I think you're doing a great job at trying to test and figure things out...

 

..TWR comparisons are largely meaningless when the sources were 'something you read about'. Even if you have the official aircraft manuals, it is necessary to look at the point of the envelope (or envelope range) that you want to compare. This envelope consists of the aircraft's gross weight, altitude, and speed. You're usually looking for some Ps curve here, and you might find it. Just don't be suckered into thinking that it tells you the whole story.

:) Thanks. I knew the statement wasn't directed at me. I was hoping to get public confirmation of my private conclusion that cited t/w ratios were fairly meaningless, since you never know exactly what went into them. Apples to apples; or apples to oranges? I was finding that the more I researched, the less I knew.

 

The problem of planes feeling underpowered may be a by-product of lack of perception when aircraft is being stressed. You pull the aircraft to it's limits and it falls off the sky with little warning.

 

We need to hear a more pronounced airflow noise change from inside the cockpit along with some shuddering, and changes to the contrails, some axis tuning (you get maximum input with little deflection), things like this that also add to immersion. :)

To compensate for the lack of perceptual clues that you would presumably get in real life, I find myself flying with a close eye on the AoA/G meter. Once I started doing that, I found it much easier to keep the aircraft within its flight envelop and still ride its edge.

[GGTharos]

That Su-27 could get out of your way if it wanted - that's all I'll say to this.

 

If he stays in a turn with you in that particular situation though, I don't see why you couldn't nail him. He's playing YOUR game now, he's out of HIS best flight envelope and you're right on yours.

 

Is it "normal" that i can kill a su27 with dora (Fw190d) in a low speed turning fight? And not against the AI.. Below 400 km/h it feels like the flanker has no power comparing to the flanker before the last update. It's acting like a prop aircraft..which kinda sux :(

[Pilotasso]

To compensate for the lack of perceptual clues that you would presumably get in real life, I find myself flying with a close eye on the AoA/G meter. Once I started doing that, I found it much easier to keep the aircraft within its flight envelop and still ride its edge.

 

Anyone could do that but it is distracting you from what is happening outside because if you had those clues you wouldn't spend as much time looking in just one direction.

 

The clues would be a major differentiation feature to other SIM's. :)

[Ironhand]

Anyone could do that but it is distracting you from what is happening outside because if you had those clues you wouldn't spend as much time looking in just one direction.

 

The clues would be a major differentiation feature to other SIM's. :)

You're right, of course. That's simply my workaround for the type of flying I do right now.

[MiG21bisFishbedL]

Is it "normal" that i can kill a su27 with dora (Fw190d) in a low speed turning fight? And not against the AI.. Below 400 km/h it feels like the flanker has no power comparing to the flanker before the last update. It's acting like a prop aircraft..which kinda sux :(

 

I doubt many swept-wing fast fighters would be able to turn with a straight-wing piston fighter. When you hear that the Flanker has good low-speed performance, realize that this is all relative.

 

350km/h is slow for a more contemporary turbine-engined fighter, but it's pretty speedy for an old piston fighter like the Dora. Their best maneuvering speed may even be around 340-360km/h.

[FLANKERATOR]

It all depends on speed; above 450km/h, the jet will turn and sustain speed better, not to mention the ability to engage and disengage at will (far superior thrust and aerodynamics) on top of far better vertical maneuvering capabilities.

 

Below 450km/h, a prop fighter can turn better, but then all a jet needs to do is to build separation by either extending away or going vertical.

 

Su-27 is way too much to handle for any prop fighter, just take a look at the far more modest Me-262 combat record vs allied prop fighters.

[amazingme]

You're right Flankerator, but you're talking about real life ACs I was talking about DCS.

I got used with the new flight dynamics especially the magical S key which disables the FBW system and I use it all the time to make fast turns @ very high speeds. I can do a chandelle in a couple of seconds (20Gs turns). I think this model is very UNREALISTIC inspite of everybody here on the forum says that they respected the manuals. Hmm.. anyone can test this:

-Speed around 1000km/h

-fly horizontally

-pull the stick a little (nose up) to prevent the nose going down and in the same time press the S key and start the chandelle. After the maneuvre is completed you'll climb ~500 m and lose ~500 km/h from the airspeed but THAT turn.. you'll make it so fast.