On most sailplanes torque from the rotating slipstream from the tug, specially if you're low behind it, will cause roll :-) So, gliders can suffer from torque roll :-) (but not in x-plane :-(

 

You're asking WAY too much... Slipstream effects from the prop of another aircraft... AFAIK there's no simulator that calculates this. Maybe some flight sim devoted only to soaring/glider? But that would be a very specific case.

 

P.S.: Just 1 more thing! I'm glad you picked the 1900d for your experiments. I confess I liked the model, although I have to set my throttle axis properly because, just as it is, it goes down from beta range to reverse without having to hit the default key used in x-plane for reverse thrust...

 

Unfortunately that B1900 suffers from an unexplicable asymmetry on the roll/yaw axis. Even after removing all the asymmetry effects inside Plane-Maker, the aircraft still tends to yaw/roll in one direction (even after setting counter-rotating props, or after separating engines/props in the failure screen).

 

I don't know what is the reason... Maybe some bug due to the fact that it was originally made in X-Plane 8?

 

So with this abnormal behaviour on the lateral axis, it is impossible for me to deal with the prop torque issue... I'd need at least an aircraft that has simmetric behaviour once all prop effects have been removed.

 

Marco

<br />I'm still not 100% sure it's a bug. John Denker (a pilot himself) writes:<br /><br />"Airplane designers have long since learned about this propeller drag rolling moment, and they take steps to compensate for it. For instance, they set the left wing at a slightly higher angle of incidence than the right wing. This is called, unsurprisingly, asymmetric incidence. It is especially useful to apply this trick to the part of the wing that flies in the propwash, so that the effect increases as engine power increases. On a Piper Cherokee, the roll-wise trim is easily adjustable on the ground — in the flap extension mechanism for each flap there is a turnbuckle that allows the flap to be raised or lowered until the roll-wise trim is just right."<br />

 

I'm not sure about that either. Again, taking my own airplane as an example. Incidence for both wings is exactly the same. Engine is canted to the right. Vertical stab has no offset. This plane has enough power, versus size & weight, to feel the effect of torque on the takeoff roll. On my first test of a touch & go, I thought WOW, when I applied throttle to quickly. It actually pushed the left gear leg down. You can see why P-51's will roll completely over, if full throttle is applied on a go-around. Once my plane airborne & level, it doesn't want to roll. I have plenty of pics with ailerons in perfect trail during the initial climb. I had a aileron trim tab to adjust for loads only. Since my verticle stab had no offset built in, while some newer models do, it required a fixed rudder trim tab, which you'll find on some high wing Cessna's. The plane uses no trim tabs for roll.

 

L.Adamson

 

 

Problem is, yaw should induce roll. What happens if you don't compensate for this yaw? Will the aircraft roll progressively to 90 degress?

 

That's a good question. For the first few cross country flights of my RV6, I had no rudder trim tab to correct yaw. While aileron forces are really light, you have to use some leg muscle on the rudder pedals, or just let the aircraft yaw to the left, which I did. I do not remember a rolling tendency. However, stick forces to correct roll would be light, and perhaps I didn't notice.

 

You're asking WAY too much... Slipstream effects from the prop of another aircraft... AFAIK there's no simulator that calculates this. Maybe some flight sim devoted only to soaring/glider? But that would be a very specific case.

 

Wait a minute, I thought X-Plane was simulating real air! :wink: I consider my plane, and others like it, to be mini 757's (famous for tip vortex). If we get into the lead planes wing tip vortex, it can throw us all over the place. Where are those simulated air particles after they leave those simulated wings ?...

I'm not sure about that either. Again, taking my own airplane as an example. Incidence for both wings is exactly the same. Engine is canted to the right. Vertical stab has no offset. This plane has enough power, versus size & weight, to feel the effect of torque on the takeoff roll. On my first test of a touch & go, I thought WOW, when I applied throttle to quickly. It actually pushed the left gear leg down. You can see why P-51's will roll completely over, if full throttle is applied on a go-around. Once my plane airborne & level, it doesn't want to roll. I have plenty of pics with ailerons in perfect trail during the initial climb. I had a aileron trim tab to adjust for loads only. Since my verticle stab had no offset built in, while some newer models do, it required a fixed rudder trim tab, which you'll find on some high wing Cessna's. The plane uses no trim tabs for roll.

 

L.Adamson

 

Thanks, that is interesting. So, for example, going from idle to full power on a go-around, would you have to compensate also for roll other than yaw?

 

And another question, are you saying that there is no roll input at all in either climb, cruise or descent? Will it remain wings level hands off?

 

Marco

 

Wait a minute, I thought X-Plane was simulating real air! :wink: I consider my plane, and others like it, to be mini 757's (famous for tip vortex). If we get into the lead planes wing tip vortex, it can throw us all over the place. Where are those simulated air particles after they leave those simulated wings ?...

 

Yes... It's simulating "real air", but only on your aircraft. Of course its flight model has limitations... And regarding wing tip vortex, Austin mentioned it models some sort of wake turbulence, but I doubt it's an accurate modeling, probably just a very rough one... Would probably be too much computationally expensive.

Once my plane airborne & level, it doesn't want to roll. I have plenty of pics with ailerons in perfect trail during the initial climb. I had a aileron trim tab to adjust for loads only. Since my verticle stab had no offset built in, while some newer models do, it required a fixed rudder trim tab, which you'll find on some high wing Cessna's. The plane uses no trim tabs for roll.

 

I think this is the most common among GA prop aircraft. At cruise speeds the lift forces are more than enough to counter any torque-roll tendencies, unless you make power variations, which, being done smoothly as they are supposed to be done, will probably not even produce noticeable roll effects....

Looks like A C-model, Not a D-model.....D Model had a very different

Fuselage Bigger Pratts and a few other niceties.

Thanks, that is interesting. So, for example, going from idle to full power on a go-around, would you have to compensate also for roll other than yaw?

 

And another question, are you saying that there is no roll input at all in either climb, cruise or descent? Will it remain wings level hands off?

 

 

Sometimes, just as the wheels lift off the ground, I'd have to throw in some right aileron, as the wing dips to the left. But that's about it. For the rest of the climb, cruise or descent, I'm not noticing roll, and my ailerons certainly are not showing that their compensating for it.

 

edit: Additional info. When this subject came up, I asked my wife, & also a friend, about their thoughts when flying this plane. Neither are pilots. As far as they were concerned, the stick just stayed centered by the air forces over the wings, and there was no thought of having to hold the stick against a roll force. Just a few corrections here & there to remain on course & altitude.

Flight Unlimited 2, and probably 3 as well, modeled the propwash from other aircraft. It might not be a very detailed model, but it took into consideration the power of the engine/flow... Putting your little Cessna-like aircraft behind an AI Jumbo initiating it's takeoff roll would cause quite a "throw away" effect :-) Parking behind a Cessna would at least show variations in your ASI !!!! Flight Unlimited was quite ahead of it's time...

Flight Unlimited 2, and probably 3 as well, modeled the propwash from other aircraft. It might not be a very detailed model, but is took into consideration the power of the engine/flow... Putting your little Cessna-like aircraft behind an AI Jumbo initiating it's takeoff roll would cause quite a "throw away" effect :-) Parking behind a Cessna would at least show variations in your ASI !!!! Flight Unlimited was quite ahead of it's time...

 

I remember that, it was a nice effect. I don't know to what extent X-Plane models jetwash on other aircrafts. However I doubt FU2 or 3 would model the effects of _helical_ propwash of another aircraft on your aircraft (the one you were referring to in your example of the glider).

 

Marco

I remember that, it was a nice effect. I don't know to what extent X-Plane models jetwash on other aircrafts. However I doubt FU2 or 3 would model the effects of _helical_ propwash of another aircraft on your aircraft (the one you were referring to in your example of the glider).

 

Marco

 

Marco, it was not yet this turn around that I won the European Lotery :-( Our flight simulator project will have to wait ..... :-)

 

It will include the whole Earth, with detail and sharpness like Outerra, weather phenomena fully modeled, including waves for soaring, precise turboprop, prop, jet, rocket, etc... propulsion types, complete avionics of various types and brands, a full hangar of representative GA, Medium and Heavy aircraft (fixed and rotary, as well as gliders, baloons, etc...), etc...

 

ATC will be as complete as possible, dependent on the region of the World you're operating in, AI will accurately follow their flight plans or VFR walks interacting with other aircraft and ATC, diverting from bad weather regions, etc.... There will be random failures, missions, etc... Seasonal effects will of course be there too. Physiological effects of flight / space flight will also be modeled.

 

One of the first free add-ons (of course, it will all be free to play!!!!), will include the Moon, a detailed Moon, and spacecraft to allow for flights Earth-Moon and return....

 

OMG!!!! It will be so good!!!!! I just have to earn that Lotery, the BIG ONE!!! ... c'mon, cross your fingers ....

Even after removing all the asymmetry effects inside Plane-Maker,

 

Did you zero the aileron trim tab too in the control / geometry section of PM?

Did you zero the aileron trim tab too in the control / geometry section of PM?

 

Yes, I also removed/corrected all the asymmetric wings or bodies... Checked for asymmetric fuel tanks... But the asymmetry remain. Very strange!

However, I would like to add some observations. This B1900 is labeled as "professional", and "originally used in professional simulators".

 

However, if you check it in Plane-Maker, you'll see that it's not made in a 100% correct way from an aerodynamic point of view. Some examples:

.the vertical stab should be modeled as two wings stacked vertically, while it's modeled as two wings stacked horizontally (if you see how it's made in Plane-Maker, you'll understand what I mean);

.there is no "hidden" wing inside the fuselage to account for the carryover lift (AFAIK X-Plane does not model the carryover lift on fuselage between the wings, so it must be accounted for by designer);

.the lift along wingspan is discontinuous (this can be observed with the "show flight model" option in X-Plane). Now, this is physically impossible since discontinuous lift would produce a trailing vortex of infinite magnitude. In reality spanwise lift always varies more or less smoothly.

 

Now, these are the most glaring "imperfections" I found immediately. Probably at a deeper observation there are a lot more (airfoils, etc.).

 

This is not to say that it's totally inaccurate. Maybe some of those "imperfections" are not very significant for the final flight model, but others could be. Probably the author obtained satisfaying results in terms of performances compared to the real one if it could be used as a training tool. My observations are just to point out that making an aircraft that is 100% aerodynamically faithful to the real one is not easy, and a 100% fidelity in flight model would most probably require extensive flight tests on the real aircraft (since X-Plane flight model is not perfect, so it needs a certain degree of tweaking in any case).

 

And 99,9% of aircrafts made for X-Plane have some of those "imperfections", or have been made without extensive access and flight tests on the real one, or most probably both.

Those Flight Models are probably tuned to match the performance by the books, they probably weren't looking for having the most correct way under X-Plane to make an aircraft.

 

For example, if I have a simulator for training IFR, I need it to match the Power Setting on the Glideslope for the Configuration of the aircraft, IAS, Rate of Descent, Angle of Pitch. They probably tune it until they matched those numbers, they probably weren't looking for the degree of detail that you guys are looking for in this topic.

 

That's what I think. And I do hope that when you guys can make your observations into the FM of an X-Plane Aircraft, it will fly beautifully! Love reading all these posts

 

And since you guys love reading about Flight Dynamics, read what FSLabs is doing to their A320 regarding FM.

 

http://forums.flightsimlabs.com/index.php?/topic/4490-the-a320-a-medium-ish-update/

 

This is the only way in my opinion for realistic FM, bring the complex stuff outside of the simulator, and do the Code to match the aircraft you're modeling.

Unfortunately that B1900 suffers from an unexplicable asymmetry on the roll/yaw axis. Even after removing all the asymmetry effects inside Plane-Maker, the aircraft still tends to yaw/roll in one direction (even after setting counter-rotating props, or after separating engines/props in the failure screen).

 

That is most likely a result of this bug:

http://forum.avsim.n...3/#entry2490948

 

It's not been fixed yet.

 

+they used a not symmetrical airfoil on vert. stab2

removed it and it still drifts slightly to the right.

Good catch marcus!!! And I missed to check if there were asymmetrical aiirfoils on vertical stabs! Another good catch!

 

EDIT: Well, the roll tendency remains even after making the aircraft completely symmetrical. It's clear that this bug influences and prevents the correction of the prop torque issue. We'll have to wait until Austin resolves the bug.

 

Marco