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Nose down AB and do not acelerate?????


Barao
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I do not think that's right. If I'm with 100 knots, AB, in a dive and turn around without pulling too much G (no buffer), the aircraft does not increase speed. In other situations, during horizontal flight and pulling 6 G, with AB too, the plane accelerate ???????

 

Talking with a F-2000 fighter pilot and showing this in DCS to him, he said that this is not real.


Edited by Barao

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I do not think that's right. If I'm with 100 knots, AB, in a dive and turn around without pulling too much G (no buffer), the aircraft does not increase speed. In other situations, during horizontal flight and pulling 6 G, with AB too, the plane accelerate ???????

 

Talking with a F-2000 fighter pilot and showing this in DCS to him, he said that this is not real.

 

I agree completely with this post.

 

When airspeed is lost - the aircraft will respond with less that what is expected when put nose down in full AB. - even with airspeed in the 150+ range.

 

It will accelerate much faster on the runway from stand-still than when you have already got 150+ knots of airspeed and nose down at altitude.

 

This cannot be right.

 

I've lawndarted many times when the aircraft should have recovered in sufficient time.

 

Something not working correctly IMHO, with acceleration at altitude with 100+ airspeed in place.

 

Recovery is far too slow and one might as well have a propeller on the nose.

 

Cats . . . .

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You can be in a dive but with 90° AoA you won't accelerate....

 

No - in a dive, nose down pointing at the ground.

 

I can see one descending with a high AOA but the poster said, and I agree, NOSE DOWN - not pulling on the stick.

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I agree completely with this post.

 

When airspeed is lost - the aircraft will respond with less that what is expected when put nose down in full AB. - even with airspeed in the 150+ range.

 

It will accelerate much faster on the runway from stand-still than when you have already got 150+ knots of airspeed and nose down at altitude.

 

This cannot be right.

 

I've lawndarted many times when the aircraft should have recovered in sufficient time.

 

Something not working correctly IMHO, with acceleration at altitude with 100+ airspeed in place.

 

Recovery is far too slow and one might as well have a propeller on the nose.

 

Cats . . . .

 

Yes, this is the problem, You understood the problem.

 

Later I will check AOA, but it is not to much.

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Later I will check AOA, but it is not to much.

Errr... you're probably mistaken there. :detective:

 

I agree there is a problem in current FM, as you described it.

But it really is related to AoA (and induced drag).

 

General rule of thumb:

Stay below 15° AoA: thrust > drag = you can accelerate.

Go beyond 15° AoA: drag > thrust.

 

Now, currently, there is indeed too much of an effect; this can lead to ~irrecoverable situations if you find yourself low and slow: you don't have enough altitude to trade when you try to unload (go 0g / lower AoA). As your former F-2000 pilot said, the aircraft should be more "gentle" and remain more recoverable (given that the pilot do what he needs to). :thumbup:

 

++

Az'

 

PS: AF447 was lost between Brazil and France because of AoA, not speed.


Edited by Azrayen

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General rule of thumb:

Stay below 15° AoA: thrust > drag = you can accelerate.

Go beyond 15° AoA: drag > thrust.

 

 

This is too binary. There must be a transition algorithm to simulate the increase in drag to the delta wing.

And yes, I noticed this relationship with the 15° AOA, and I say that this transition between the drag-power relationship is exaggerated.

 

And something else, being nose-down, diving in full AB, even if the AOA exceeds a little 15°, there must be an acceleration, until a stone accelerates in a fall.

The algorithm that controls the drag-lift transition can not be the same for horizontal and vertical flight.


Edited by Barao

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This is too binary. There must be a transition algorithm to simulate the increase in drag to the delta wing.

And yes, I noticed this relationship with the 15° AOA, and I say that this transition between the drag-power relationship is exaggerated.

 

Can you say it with charts/math?

 

And something else, being nose-down, diving in full AB, even if the AOA exceeds a little 15°, there must be an acceleration, until a stone accelerates in a fall.
Ok, do we know what this terminal speed is?

 

The algorithm that controls the drag-lift transition can not be the same for horizontal and vertical flight.
Of course it can be and in fact it must be. It includes accounting for gravity, but bugs or omissions can easily creep in.
Edited by GGTharos

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No - in a dive, nose down pointing at the ground.

 

I can see one descending with a high AOA but the poster said, and I agree, NOSE DOWN - not pulling on the stick.

 

He said he is in a dive with not too much Gs and turning around, so he may be diving bu he will have a very high AoA which won't let him accelerate

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This is too binary.

This is why I wrote "rule of thumb". It's meant to be remembered by the pilot, I'm not describing how the FM code works.

 

And yes, I noticed this relationship with the 15° AOA, and I say that this transition between the drag-power relationship is exaggerated.

And I agree with you, except that I think power (trust) is not the issue. Drag/AoA is.

 

The algorithm that controls the drag-lift transition can not be the same for horizontal and vertical flight.

The load factor differs, but for the rest I'm not sure I follow you...

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I do not know the exact numbers, and my English is too bad to explain details.

But I think we all know that something is wrong. I do not know exactly what.

 

I hope the company will find the problem before the release version.

 

Even so, I will continue to fly M-2000, It's a great project and a fun module.

 

I only expose my impressions based on the experience of a friend who knows the actual machine and based on my feeling that something is wrong

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Ok, do we know what this terminal speed is?

 

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Ok, do we know what this terminal speed is?

 

Yes, but here we have AB pushing the airplane down. It can make some diference.

 

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I tested again, I believe that the effect is correct, but exaggerated, Maybe something is creating a excessive drag, more than speed brake.


Edited by Barao

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Even with FBW it is possible to drain off enough speed to stall the aircraft and depart from controlled flight and enter an unrecoverable spin, under these conditions even full AB will not do much unless you can bring the aircraft back within the flight envelope.

 

Not saying that this definitely isnt caused by bugs in the FM, just that nothing described is outside of the realms of physical possibility.

 

If the velocity vector is within the HUD when you are powering towards the ground and not picking up speed, then its definitely the FM. If the VV is not in the HUD, you have probably departed.

 

NB: Im not sure how the engine and thrust is modelled, but if you are at say, 90deg AoA, the engine may not be producing all the thrust it can, even with full AB. This is due to problems getting air to flow into the intake.

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Now, currently, there is indeed too much of an effect; this can lead to ~irrecoverable situations if you find yourself low and slow: you don't have enough altitude to trade when you try to unload

 

Thanks Azrayen,

This is it exactly.

 

Also, recovery time at altitude in a combat situation where excessive AOA has induced high drag, the length of time to recover sufficient airspeed when nose down and in AB seems quite long.

 

This drag also makes it a bit tricky in landing also with respect ensuring that airspeed and AOA don't get to extreme or slow because you will sink rapidly and full power won't help. :)

 

Thanks again.

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I was with the AOA slightly higher than 15º (I will test again), nose down in a full AB dive, and the airplanes do not gain a positive attitude to regain speed and flight level. I know that the drag in this situation reduces the thrust, but it is exaggerated.

 

I know that a lot of the required data is confidential, but I think a conversation between the team and some M-2000 pilot could at least reduce the mistakes without compromising the secrecy. This is because the team has competence to understand what the professional describes, it would be something more technical than this our debate.

 

This is a client's suggestion.

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Tested again:

 

30° dive, Full AB, 150 knots, AOA 18°, and 1.6 G

 

In this attitude the aircraft loss speed.

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Tested again:

 

30° dive, Full AB, 150 knots, AOA 18°, and 1.6 G

 

In this attitude the aircraft loss speed.

 

I'm thinking that if you were in level flight with a 48° AOA, you would decelerate very quickly. Get the AOA down to 0 or close, that should help.

 

(amateur DCS pilot here) :pilotfly:

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