Questions about Aerodynamic Model

[NineLine]

I think it's the only gross shortcoming in the model..... takeoff should and is a delicate thing with some very dark corners that will kill you quickly if you don't know what to expect.... it's just the observed attitude deviations on takeoff roll are too small when loss of control occurs...room for error is too small. It feels as if aerodynamic stability which should start to occur at relatively low speed is missing... as well as flight control effectivity.

 

 

But everything you say, at least to me, sounds like you are saying the controls feel too sensitive to you, which generally points to the short comings of our flight sticks... This was a issue with the P-51 as well.

 

All these out of control take offs look like that... over correction, etc...

[fjacobsen]

In real life we would be able to feel the slighetst lateral movement like skid, yaw and turn.

 

Sitting on an normal chair with a 10 inch stick and rudders with no feedback, looking through tunnelvision into a monitor or even 3 monitors, simply doesn't give the all important subtile feedback and periphical vision You would get in real life.

 

Many expect that developers are able to deliver us 1:1 replicas, but in the end all we get (and what we paid for) are only a virtual aircraft flown with the very same hardware controls we use for jet-airliners, GA-Aircraft, combat jyes, helicopters etc.

 

 

I belong to the croed of hardcore flightsimmers who strive for the ultimate realism, but having been around this business fo almost 2 decades I also know that compromises and ommissions has to be accepted.

 

In 10 years we will wonder how on earth we where pleased with the simultors we fly today and that how it should be.

 

Apart from some angryness about some of the beta modules (not the FW-190D9), I still find that DCS is among the leaders in flightsimulation.

 

That doesn´t mean it´s perfect, but it´s still very good and immersive.

 

 

FinnJ

[NineLine]

Something is off and while I am no engineer I just feel its due to not enough energy bleed off with no power.When my engine cuts out I expect the plane to drop like a rock but it instead just floats on and on.This is ok to live with as I try not to bust my engine BUT it in turn is causing my landings to feel off.With power off and landing I seem to float forever over the runway and find I need to pull too much on the stick which is causing three pointer landings.If I want to do a 3 pointer I would like to be able to initiate it but instead I find that I NEED to pull too much elevator to bleed off speed.

 

With out a track of the issue its impossible to tell... it could be you are coming in to fast, and expecting the aircraft to slow more than its willing to....

[Barfly]

But everything you say, at least to me, sounds like you are saying the controls feel too sensitive to you, which generally points to the short comings of our flight sticks... This was a issue with the P-51 as well.

 

All these out of control take offs look like that... over correction, etc...

 

No, control sensitivity aside, loss of control occurs with too small an attitude deviation of the virtual aircraft. There should be a larger envelope of deviation that can be countered by control forces.

[NineLine]

No, control sensitivity aside, loss of control occurs with too small an attitude deviation of the virtual aircraft. There should be a larger envelope of deviation that can be countered by control forces.

 

Now I think we are going in circles ;)

 

Small envelope of deviation could be cause by the incorrect stick length couldnt it(leverage makes a big deal in many things, why not here)? Or incorrect travel distance in rudder pedals, etc etc...

[Rocky49]

My experience with the 190 led me to explore my Saitek pro rudder pedals setup. I descovered that there is a very slight spiking occurred around my center point. Added with the strong detent type of manufacture (around the self centering point) with Saitek rudders causes too much inconsistant imputs occurring right at the point of crusial right rudder imput. Most of us are over coming this by using very rappid and continuous left and right rudder imputs (or dancing the rudders, as some have described it) to try and dampen out these inconsistant spikes in our hardware. In real life I have only used this technique rarely when landing in gusting conditions. Just my 2 cents worth. BTW, ordered some Crosswind rudders from Milan. I bet those rudders with their much more consistant imput control do need any dancing, just small right rudder imputs.

[NineLine]

My experience with the 190 led me to explore my Saitek pro rudder pedals setup. I descovered that there is a very slight spiking occurred around my center point. Added with the strong detent type of manufacture (around the self centering point) with Saitek rudders causes too much inconsistant imputs occurring right at the point of crusial right rudder imput. Most of us are over coming this by using very rappid and continuous left and right rudder imputs (or dancing the rudders, as some have described it) to try and dampen out these inconsistant spikes in our hardware. In real life I have only used this technique rarely when landing in gusting conditions. Just my 2 cents worth. BTW, ordered some Crosswind rudders from Milan. I bet those rudders with their much more consistant imput control do need any dancing, just small right rudder imputs.

 

Nice... lets hope they accidentally deliver those Crosswinds to Surrey ;)

[Barfly]

Now I think we are going in circles ;)

 

Small envelope of deviation could be cause by the incorrect stick length couldnt it(leverage makes a big deal in many things, why not here)? Or incorrect travel distance in rudder pedals, etc etc...

 

No, I was not clear enough. I mean deviation of the model, not the control input. The control sensitivity issue is a different problem, but does exacerbate the issue of control.

Edited August 22, 2014 by Barfly

[NineLine]

No, I was not clear enough. I mean deviation of the model, not the control input. The control sensitivity issue is a different problem, but does exacerbate the issue of control.

 

So you are able to tell the issues with control sensitivities from the perceived FM issues? I will have to quote Yo-Yo then....

 

Какие ваши доказательства?

[wolfstriked]

With out a track of the issue its impossible to tell... it could be you are coming in to fast, and expecting the aircraft to slow more than its willing to....

 

Gonna try to see if I can change how I land.Maybe just my way of a harsh stick into the stomach right before touchdown is off.

[NineLine]

Gonna try to see if I can change how I land.Maybe just my way of a harsh stick into the stomach right before touchdown is off.

 

 

Check out some vids people have posted as well... its possible, I am not trying to say its your fault... but cant hurt to check all possibilities :)

[Barfly]

So you are able to tell the issues with control sensitivities from the perceived FM issues? I will have to quote Yo-Yo then....

 

Какие ваши доказательства?

 

Yes! Finally.. lol. Are you asking me in Russian if we are talking about the same simulator? :)

[NineLine]

No, use Google translate... you might change your "Yes! Finally.." response ;)

[Yo-Yo]

I think this item will be discussed again and again like a tide. The first wave was after P-51 beta had been released, then after its public release... the Dora tester's wave was not too high. Now we have the next wave.

 

So, I have to repeat some statements from this discussion.

 

1. The taildragger IS UNSTABLE as it rolls up to the speed when the stability due to its fin begins to prevail over instability due to its undercarriage.

2. Propwash is nothing for the STABILITY because it is almost fixed to the axis of the plane. It turns with the plane so it can not stabilise yaw movement.

3. Propwash is very powerful for the CONTROLLABILITY. The more power is applied the more agile is the plane reaction (at low rolling speeds).

By the way, one can feel it starting TO run in Dora with unlocked tailwheel at full power - it seems that it goes for the pedals "sitting tight" in the propwash.

 

4. Anyone can turn TO assistance on and start roll fixing rudder to 1/5-1/4 right. Watch the track - and notice that your "instructor" tapped as the real pilot does while your plane goes ideally straight. It even applies right rudder as the nose goes down and then release it even more than before rotating. AS in real life.

5. The last but not the least: the main challenge in the virtual world is to learn how to compensate the lack of acceleration info using only visual perception.

 

sic

 

 

 

Google more themselves for "Ground loop"

Edited August 22, 2014 by Yo-Yo

[msalama]

The plane takes off skidding, and out of control in yaw axis, until it iairborne

 

Not true. I can't fly the beast at all yet, but even I can tell from my couple of tries that this just isn't true. So if you're still claiming that, then you'll need to show some tangible and unequivocal evidence. Waiting... :music_whistling:

[sobek]

This one made me smile.

 

The coloured lines are field vectors, most likely of the velocity field, that is, they tell you how fast and in what direction the air packet at the point of origin of that vector is moving. However due to the nature of a field, as soon as that packet has moved on, it may start moving into a different direction. The length and direction of one single velocity vector does not indicate where that packet will end up.

 

Regardless of what field they help visualize, you need to keep one fact about vector fields in mind. A vector of a vector field only contains information about the point where it originates, long story short, the fact that it ends before the rudder says relatively little about the field at the rudder.

 

In fact, if you played with the scaling of the magnitude, you could make these vectors reach to the moon, but that doesn't mean that you would feel the propwash when standing on the moon.

[NeilWillis]

I was sure there was a problem with the Dora at first. Bloody difficult to get it airborne without assists. But now, I have the hang of it, and I have to concur with the majority view here. There is no issue with the aerodynamics, just with my slow responses to yaw. Once it gets out of hand, it can't be recovered, so you just have to make small, fast inputs on the rudder, and then it's sweet as a nut.

 

Plus all that stuff about vector fields too ;)

[Yo-Yo]

CLOUDS! CLOUDS! :)

 

And the second rule: Tap rudder against yaw angular velocity more than against the yaw itself or you will increase the magnitude (PIO).

[Barfly]

I think this item will be discussed again and again like a tide. The first wave was after P-51 beta had been released, then after its public release... the Dora tester's wave was not too high. Now we have the next wave.

 

So, I have to repeat some statements from this discussion.

 

1. The taildragger IS UNSTABLE as it rolls up to the speed when the stability due to its fin

 

Personally I don't disagree with anything you said, and I think the low speed characteristic are excellent.

 

The problem some of us are identifying is the transition between prop forces and ground dynamics at low speed, where there is essentially no aerodynamic control except for prop wash and wind, and where stability and better control occurs due to increasing airflow over the airframe and control surfaces. Those "flying" forces should occur well below takeoff speed, and should permit attitude and inappropriate control deviations that are relatively easy to correct.

[NeilWillis]

Doesn't prop wash spiral, and add to the instability issues rather than negating them?

[NineLine]

Doesn't prop wash spiral, and add to the instability issues rather than negating them?

 

I was just wondering this myself...

[Yo-Yo]

FM critics, do you recognise your TO? :)

 

[Yo-Yo]

I think this item will be discussed again and again like a tide. The first wave was after P-51 beta had been released, then after its public release... the Dora tester's wave was not too high. Now we have the next wave.

 

So, I have to repeat some statements from this discussion.

 

1. The taildragger IS UNSTABLE as it rolls up to the speed when the stability due to its fin

 

Personally I don't disagree with anything you said, and I think the low speed characteristic are excellent.

 

The problem some of us are identifying is the transition between prop forces and ground dynamics at low speed, where there is essentially no aerodynamic control except for prop wash and wind, and where stability and better control occurs due to increasing airflow over the airframe and control surfaces. Those "flying" forces should occur well below takeoff speed, and should permit attitude and inappropriate control deviations that are relatively easy to correct.

 

THey should. But only if you do not fight with these forces applying wrong input.

Edited August 22, 2014 by NineLine

[Yo-Yo]

By the way - no circus, no tricks, no pedals, no sticks...

 

[aaron886]

Doesn't prop wash spiral, and add to the instability issues rather than negating them?

 

That's over-simplifying the effect. You have to quantify how it changes stability characteristics. "Spiraling slipstream" or "helical propwash," at low speeds, produces a right-rolling moment until angle of attack is increased so as to induce a stall, in which case the left wing (partially as a result of helical propwash) will stall first and result in a spin. (Compounded by other "left-turning" effects.) Typically, while on the ground at low speed, the intensity of helical propwash is at its highest, and causes propwash to hit one side of the vertical stabilizer more than the other, contributing to the aircraft's low-speed/high-power turning tendency. The FW-190, like the P-51 and most "Western" designs, has a counter-clockwise propeller rotation, and therefore will produce a left-turning moment.

 

Controllability, the counterpart of stability, should be quite high when power is applied at low speeds. In fact this is often part of the problem... a small input by the pilot made in the wrong direction or at the wrong intensity can result in a divergent condition. That's what you're seeing in those ground-loop videos Yo-Yo is posting. It's a "chicken and the egg" discussion in some ways, but the pilot is responsible for each of those situations, therefore largely as a result of the aircraft's controllability rather than its lack of stability.

 

And the second rule: Tap rudder against yaw angular velocity more than against the yaw itself or you will increase the magnitude (PIO).

This is very insightful, although difficult to parse in English. This is a reaction that is difficult to learn quickly, and something I regularly attempt (and fail) to teach in real life... it's just tricky. The point is recognizing the difference between yaw angle (officially "sideslip" or "Beta") and yaw rate (how quickly that yaw angle is changing.) If you react by increasing the size of your rudder inputs as a result of yaw ANGLE, you are going to make the problem worse and enter a "pilot-induced oscillation." (PIO) If you adjust the size of your yaw inputs to match yaw RATE, you will have a damping effect and act as an artificial stability. (...powered by beer and snacks.) In my experience, this is difficult for the inexperienced primarily due to the quick recognition required to see yaw rate changes. If you miss the change in yaw rate, the next thing you'll see is the change in yaw angle, and it's too late.

 

There are times when I've questioned the effect of propwash and free-stream deformation in Mr. Yo-Yo's models, but truth be told, that's splitting hairs. The detail in these flight models is fantastic, and they can be flown properly through most of their envelope with each effect attributed to real aerodynamic responses. Sometimes that means adapting to an unfamiliar response, once you've determined that the response is plausible. It's likely that the lack of physical feedback and plastic flight controls are responsible for many serious complaints, but "it doesn't turn when I tell it to" does not qualify.