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1700 km/h needs AOA 8 degrees to fly straight (bug?)


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Posted

Sure looks strange, that must be a tad over 1000km/h IAS, the AoA should be exactly the same as on the deck at that speed (= close to 0°) if I'm not mistaken. As it is not the case, this is a major induced drag source that shouldn't be there at all.

dcsdashie-hb-ed.jpg

 

Posted
Is that a bug or supposed to look like that? As you can see on the screenshot, flying at 1700km/h and to keep the plane level it needs and AOA of 8 degrees.

 

I suggest you post a track of this, else it's difficult to help/ have a look at the issue

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Posted

Not seeing it myself. Properly trimmed, maxes out at 5 degrees AoA in my tests.

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Posted

The AoA will depend on indicated speed, not true air speed.

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Posted

IAS at 1726 TAS / 11.326 ft = 1378 km/h = 744 kt

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Posted
IAS at 1726 TAS / 11.326 ft = 1378 km/h = 744 kt

 

I think the speed indicated in F2 camera is the actual speed at which you move above terrain. Which is not teh same as IAS. Also my units are in metric, so the altitude is 11 km

 

 

Was this after re-arming?
No, it is a new flight
Posted

I have recorded a track. Same behaviour appears. to keep it level it needs and AOA of 8, but once it gets faster than 1800km/h the needed AOA for level flight is only 4-5 also the plane suddenly WANTS to climb and its hard to keep it level

 

The speed I mention here is the one from the f2 camera in metrics which appears to be the TAS.

mig21_drag1.trk

Posted
The AoA will depend on indicated speed, not true air speed.

 

Exactly what I tried to say.

1.000km/h IAS on the deck, AoA = 0°.

1.000km/h IAS at 11.000m, AoA = 5°+.

This is strange...

dcsdashie-hb-ed.jpg

 

Posted

What's the Mach number though? Remember IAS inaccuracies are simulated when flying transonic and supersonic. I wonder if this could be part of what's going on?

Posted

1800kph at 11300 meters. The wings are producing as much lift as they would at 512kts 0 meters. If you account for supersonic differences in lift it'd still be ~475kts.

Posted

I have wondered about this myself. I read that the wing has a symmetrical profile so there is no benoli effect. The wing works more like a fin than a wing... I wonder if that is why it has to fly with high angle of attack. Maybe it is a bug as you say.

Posted (edited)

First, it's Bernoulli. Second, of course there will be Bernoulli effects, no profile can magically transcend physics. Third, this "more like a fin" doesn't even mean anything.

 

A thin symmetric profile may need a little more AoA than thick profiles at low speeds, but we're talking 1700 km/h here (even if it's TAS, comparable IAS has been posted already).

 

 

 

Edit: Okay, this post may have been a bit rude. What I'm guessing is that you've fallen for that "air molecules race along the wing to meet up again with their dear friend molecules on the other side they have been separated from" explanation of aerodynamic lift. Just forget that you ever heard that explanation, it's a big load of nonsense.

Edited by Luzifer
Posted (edited)

Thats ok no offence taken. Bernoulli was the wrong effect... sorry! I noticed myself that it cruises at high angles of attack.

 

I'll explain what I was talking about though. The symmetrical wing means at zero angle of attack there is no lift whereas an asymmetrical wing will produce a low pressure area on the top which can produce lift at zero angle attack. So a piece of cardboard can produce lift if you hold it at high angle of attack. That's what I meant saying it's like a stabilizing fin on a rocket. Rather than like a normal wing. That makes sense doesn't it? Maybe the effect is exaggerated but thats what is going on isn't it?

Edited by Dirty Rotten Flieger
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