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jcomm

Are you cheating me?

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I really hate to have to use tricks / tweaks / cheats, or be tricked / tweaked to make things look like they're ok, when they aren't...

 

I believe I already mentioned once having told Austin that he should enable aircraft designers to hidden the artificial stab tweaks used to overcome any unwanted effects on a given aircraft, like those that I have been using to overcome prop torque effects... He promptly answered with a round - NO WAY!!!

 

I can only understand him, and I think it's a rather honest position. I hate having to use this sort of 

strategies when designing / fine tuning a model for a flight simulator . It tends to spoil a lot of my joy in using that model. I actually sometimes prefer not to even know what is going on in the dark... ( the cheated husband syndrome :-)

 

Yesterday while I was testing, again, some prop aircraft among X-Plane 10, FSX, DCS and ELITE, namely the prop effects, and something  that very few sims and add-ons simulate correctly - the use of rudder on coordinated turns - I came across the reason why that particular FSX model felt so different from other models - The Aerosoft DR-400 Robin, similar to one used to tow our gliders, and I had the chance to right seat a few times too...

 

This model exhibits a very pronounced roll due to torque from the prop, pretty much resembling X.-plane's models, as well as some more or less plausible demand for rudder input to kick the ball ( well, not perfect because of FSX's intrinsic turn coordinator implementation bugs...). On most occasions it also exhibits, contrarily to normal prop models in FSX, the correct need for use of right rudder, and sometimes opposite left aileron, on right-hand turns, and outside rudder on left-hand turns specially at higher power settings. Still, something felt strange about it, namely the overdone roll due to engine torque.

 

Well, I had edited the airfile, found nothing special, so, it was evident that whatever was causing that behavior came from some DLL ( the fsx's "plugin"... )

 

The real aircraft model and the one depicted by this add-on does not come with a rudder or aileron trim control, but I used to even set aileron trim (possible in fsx just like in x-plane even if the aircraft model doesn't model it...),  just like I do in X-Plane 10, to fight that pronounced left roll at higher power settings, even cruising... I have two buttons assigned to neutralize rudder and aileron trim, 

and yesterday while I was flying it, I accidentally clicked the aileron trim reset button! The aircraft reacted promptly ???? Hmmm weird!!! I almost immediately hit the rudder trim reset button and... Voilá!!!! A sudden yaw to the right was the result and from there on, and as happens to practically all prop aircraft in FSX, my ride was "smooth" and straight again :-)  The moment I made any throttle changes, that rudder and aileron trim trick kicked in again, and there I was fighting that synthetic torque roll and yaw....

 

I don't like this... really :-/  just as I don't like having to use the Art Stab section of Plane Maker or puffers in X-Plane to get a plausible behavior that should result from the direct "design" of an aircraft model.

 

X-Plane already does a lot of things very plausibly - for instance that sometimes counter.intuitive need to use less or opposite rudder on left-hand turns (*) ( even if still very soft / faint, but will probably get better with that upcoming Austin fix... ) in prop aircraft, particularly at higher power settings. So, I can only look forward with great expectations for the fixes Austin will introduce in his slip / propwash / etc calculations. 

 

If there's a better example of an "on-rails" simulator it is certainly ELITE, but the truth is that in that sim all of these effects are modeled / reproduced according to each aircraft type in it's "hangar". You can feel the realistic prop effects, power / picth / trim relations, like in no other flight simulator, with X-Plane closely approaching it, and DCS being just perfect ( I guess, not ever having flown in a p51d... )! It certainly is a LOT on-rails, but excellent for testing and obtaining a very close to real idea of how the real thing behaves... I 

 

 

(*) in all of the above, always assuming a CW rotating prop !

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Do you actually enjoy your simming time:)?

 

Good question... 80% of the time NO.... 80% of the time YES. The extra 60% is shared between me and the anti-me :-)

 

I do enjoy simming of course, although I actually remember only having used true time simming and profiting from the joy of using a simulator on two occasions - when I was a devoted Aerowinx PS1 user, learning and using the most "professional" techniques to fly the simulated 744 in that program, and when I was using MS FLIGHT :-)

 

I start DCS World quite often just for a ride in the P51d or one of the choppers, but the purpose of the sim doesn't appeal to me, and there being no chances to simulate an IFR flight like I wanted it to be, or a flight around some different scenery area, the joy of using DCS vanishes with it's somehow sterile appeal to what I like in a civil flight simulator.

 

I do the same with ELITE, but I miss some action from the weather, some better graphics, and a not so on-rails feel. Other than that it's a great sim...

 

Then there are X-Plane and FSX... I like both for different reasons, but my main attraction right now for X-plane lays in it's potential and in what I expect it to become, because the moment I start flying a prop aircraft in it and fighting the roll, I feel bad :-/

 

FSX is old, and age shows... but I am probably able to spend a full 2hrs flying a short haul flight in the PMDG 777, or a long-haul on that same model thanks to time compression :-)

 

I remember always having been like this regarding every hobby I had, starting with airplane kits, astronomy, soaring, ... It has to be perfect.... if it ain't, I'll fight it as much as I love it :-)

 

As you say in Japanese: 完璧のための無限の検索

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From reading advertisements, I know that one 3rd party developer for FSX has added "roll" back in. Using hidden aileron assignments. He said that FSX basically limits the torque roll just below stall speed. Personally, I would leave it just below stall speed.

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Good question... 80% of the time NO.... 80% of the time YES. The extra 60% is shared between me and the anti-me :-)

 

I do enjoy simming of course, although I actually remember only having used true time simming and profiting from the joy of using a simulator on two occasions - when I was a devoted Aerowinx PS1 user, learning and using the most "professional" techniques to fly the simulated 744 in that program, and when I was using MS FLIGHT :-)

 

I start DCS World quite often just for a ride in the P51d or one of the choppers, but the purpose of the sim doesn't appeal to me, and there being no chances to simulate an IFR flight like I wanted it to be, or a flight around some different scenery area, the joy of using DCS vanishes with it's somehow sterile appeal to what I like in a civil flight simulator.

 

I do the same with ELITE, but I miss some action from the weather, some better graphics, and a not so on-rails feel. Other than that it's a great sim...

 

Then there are X-Plane and FSX... I like both for different reasons, but my main attraction right now for X-plane lays in it's potential and in what I expect it to become, because the moment I start flying a prop aircraft in it and fighting the roll, I feel bad :-/

 

FSX is old, and age shows... but I am probably able to spend a full 2hrs flying a short haul flight in the PMDG 777, or a long-haul on that same model thanks to time compression :-)

 

I remember always having been like this regarding every hobby I had, starting with airplane kits, astronomy, soaring, ... It has to be perfect.... if it ain't, I'll fight it as much as I love it :-)

 

As you say in Japanese: 完璧のための無限の検索

 

I know exactly what you mean with MSFlight. I had so much hope for that sim.

 

Having never piloted in RL I don't get even half of what you guys talk about with various physical forces acting on the plane but I do enjoy watching you talk about it for some reason. And I do enjoy that talking about it on forums like this results in real improvements to the sim. XPlane seems to have a particularly good relationship between community and devs.

 

Good Japanese btw...:)

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Another cheat, in FSX and this time on a Real Air add-on :-)

 

This is good for me because I sometimes feel bad because of having to use artificial stability in X-Plane 10 to overcome the unrealistic part of the prop effects... FSX pretty much uses cheats as well.

 

Even with it's problems, X-Plane 10 flight dynamics models definitely is ahead of MSFS's, that's for sure!

 

Larry Adamson, a progressively converted X-Plane devoted user, who will move to this new platform the day Austin fixes the "Torque Bug", and someone comes out with a convincing model of an RV6 :-) posted a few days ago a link to a very good article on prop effects.

 

On that article there is a very interesting section on coordinated turns in prop aircraft, and namely the part that concerns to having to sometimes use cross-controls to coordinate.

 

While this can be true in gliders ( a normal technique here ) because of their high aspect ratio and pronounced roll-rate / «moment increase due to bank and lateral dynamic stability issues on such aircraft, on most prop aircraft the case is another one, and is connected to the prop-induced  turning / yawing tendencies.

 

ELITE reproduces on most of it's models this effect, whereby you have to use a lot more of rudder to coordinate right turns than left turns, at mid / high power settings. Sometimes on a right turn you even have to use outside yoke and cross-control it with rudder to avoid "over-banking", and in left turns you don't even have to use rudder ( other than the initial input to overcome adverse-yaw) or are even forced to use outside rudder ( right rudder in this case ), all of this assuming CW rotating props.

 

No prop aircraft in FSX simulates this effects unless a cheat is used. On it's recently released Beechcraft Duke V2 Real Air used the cheat of shifting the default ball position in the turn coordinator to the right. With the aircraft standing still and braked in the tarmac / rw you can easily see the ball shifted right. As you start moving the effect dilutes, and comes to play when you perform turns, or while climbing at high power ( requiring right rudder for realism... )

 

Yes X-Plane's prop modelling has problems, and Austin is working on it, but what it does it does very well, and certainly better than MSFS.

 

BTW: AeroFly FS's flight dynamics model, and of course DCS World, also perfectly match these effects :-)

 

FSX is becoming my PMDG NGX and 777 simulator, and this is ** only ** while I d not have a modern airliner up to those standards available for it!  I believe the 727 is already very very good, and I'll have to try that one sooner or latter ;-)

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To farther mess with someones mind...........there are all kinds of aileron setups, which directly effect the amount of yaw, and required rudder in a turn. Differential, frize, combinations of those two, and so on. Some planes just won't need hardly any rudder in most turns, if at all, while some even require leading with rudder. Since desktop flight, is a complete cheat anyway, I suppose it's a matter, of how far the developer wants to go, to simulate all of these factors; and would the user realize it, anyway.

 

 

When you think about it, the creation of a flight sim, or just the planes themselves, can be overwhelming, if you try to recreate every physic involved, let alone the systems, graphics, etc.

 

 

However, it's a cumulative effort. Year by year, some additional physics are added to the flight models. In a few thousand years, perhaps we'll be close to done...

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To farther mess with someones mind...........there are all kinds of aileron setups, which directly effect the amount of yaw, and required rudder in a turn. Differential, frize, combinations of those two, and so on. Some planes just won't need hardly any rudder in most turns, if at all, while some even require leading with rudder. Since desktop flight, is a complete cheat anyway, I suppose it's a matter, of how far the developer wants to go, to simulate all of these factors; and would the user realize it, anyway.

 

 

When you think about it, the creation of a flight sim, or just the planes themselves, can be overwhelming, if you try to recreate every physic involved, let alone the systems, graphics, etc.

 

 

However, it's a cumulative effort. Year by year, some additional physics are added to the flight models. In a few thousand years, perhaps we'll be close to done...

....and then to complicate it more is pilot technique. I would bet if a pilot crammed the throttle from idle to full power instantly there might be quite a bit of torque roll. I have to bet though and not speak from experience because I've never done that nor would choose to.

 

Some aircraft I have beta tested I've been given a list of things to do in the real aircraft. Usually a third of them I had never done and about 1/4 I refused to do due to safety issues. For instance-spin testing was halted on Barons in the early 60's. They had a nasty habit of getting into unrecoverable flat spins....chopping the throttles suddenly-not gonna do that with expensive engines.

 

When I did my commercial rating it was drummed into me the hallmark of a commercial pilot is not so much doing a perfect Lazy Eight/chandelle but high precision and smoothness, smoothness.

 

I remember taking a new ppl for a ride in my Debonair. He had never been in a constant speed prop aircraft so after takeoff I talked him thru-now I am going to reduce power and pull the prop back. I took us back to 25/25 and he looked at me and said "if you hadn't told me you were doing that I would not even known anything changed". That put a big smile on my face. Starting your reduced power for landing many miles out backing the throttle so gradually so you arrive at the airport at 15" without your passengers knowing anything has changed and more importantly your engines loving your care which adds hours to the TBO.

 

Counter to that was when I was a new pilot flying with a twin pilot on my first twin flight-him suddenly cramming the props full forward on final-the plane yawning and the engines screaming convincing me that something terrible had just happened to the engines.

 

Again though-this manifestation would occur from poor pilot technique and not be a continual occurrence aerodynamically.

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To farther mess with someones mind...........there are all kinds of aileron setups, which directly effect the amount of yaw, and required rudder in a turn. Differential, frize, combinations of those two, and so on. Some planes just won't need hardly any rudder in most turns, if at all, while some even require leading with rudder. Since desktop flight, is a complete cheat anyway, I suppose it's a matter, of how far the developer wants to go, to simulate all of these factors; and would the user realize it, anyway.

 

 

When you think about it, the creation of a flight sim, or just the planes themselves, can be overwhelming, if you try to recreate every physic involved, let alone the systems, graphics, etc.

 

 

However, it's a cumulative effort. Year by year, some additional physics are added to the flight models. In a few thousand years, perhaps we'll be close to done...

 

That's what I always think when seeing threads like this. Trying to simulate all of these diverse factors and forces on a desktop PC? I suspect (just on a hunch) that not even a gazillion dollar commercial simulator could do all what X-plane is being requested to do, not with just 3 or four separate flight models but hundreds or even thousands.

 

Or if it could, LR is seriously undercharging.

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....and then to complicate it more is pilot technique. I would bet if a pilot crammed the throttle from idle to full power instantly there might be quite a bit of torque roll. I have to bet though and not speak from experience because I've never done that nor would choose to.

I was reading through 44 pages of a radio control forum last evening, in which a model of a WWII F4U Corsair was discussed. This model does have a descent motor, which can produce a favorable amount of torque. I should know. Not being use to the newer fad of electric motors, I have several prop slashes on the bottom of my arm, to prove it. There were numerous complaints of heading a hard left, rolling and cartwheeling off the left side of the runway, just after getting airborne.

 

 

Finally, someone with aeronautical experience, explained that they need to apply throttle more slowly, use right rudder, and wait until the ailerons are effective enough.....before getting airborne. Just like the real "big" stuff....

 

His main point, was rudder, rudder, rudder!

 

edit: rudder, rudder, rudder.........is something my wife often says, when we're talking flight dynamics. She was sitting in the back seat, when I was taking a flight lesson in a Piper low wing. This new instructor was telling me to get my foot down there......and HIT that right rudder. Rudder, rudder, rudder. I have never forgotten it.

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I still think that the basic - common-sense - behavior should be reproduced. That's, for instance, the approach followed by ELITE. Inside of the normal envelope you can put their models to test, and the response will always be rather plausible.  It fails in ground handling under x-wind, but so do x-plane and fsx...

 

Then, there are sims like DCS World, even Aerofly FS, and X-Plane in some aspects, which do not use a super-computer, but are still capable of reproducing very plausible flight representations of their real counterparts...

 

Ah... that RC World Larry knows so well - I was always a very poor RC pilot. I never could manage the reverse input when the aircraft starts flying towards me :-/  Everything was great while the gliders were ahead of me but flying from side to side, or away from me... Then, for landing, we had to bring them to the top of the hills, make the base leg, final... and from there on... it was an almost complete disaster :-(  I eventually gave up - really not for my brain :-/ 

 

If I had the money to spend on it, and a good RC model, I would use a camera, and refer to the image from it to do my landings :-)

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Ah... that RC World Larry knows so well - I was always a very poor RC pilot. I never could manage the reverse input when the aircraft starts flying towards me :-/ Everything was great while the gliders were ahead of me but flying from side to side, or away from me... Then, for landing, we had to bring them to the top of the hills, make the base leg, final... and from there on... it was an almost complete disaster :-( I eventually gave up - really not for my brain :-/

 

I left R/C twenty years ago. I was on a show team, back then. Now, I'm back doing it again. Almost the same physics as the big planes. It's just that the air molecules are the same, which has to account for some scaling differences.

 

 

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I still think that the basic - common-sense - behavior should be reproduced. That's, for instance, the approach followed by ELITE. Inside of the normal envelope you can put their models to test, and the response will always be rather plausible.  It fails in ground handling under x-wind, but so do x-plane and fsx...
 
Then, there are sims like DCS World, even Aerofly FS, and X-Plane in some aspects, which do not use a super-computer, but are still capable of reproducing very plausible flight representations of their real counterparts...

 

Agreed! I just think that in the case of those other sims (Aerofly, Dcs) they have relatively few models that they can tweak the poo out of over a long period and to their hearts content. Poor ol' X plane has to stretch its blade element whatsis over zillions of planes, and its not gonna always work out well with all of them. To correct that there almost have to be cheats and workarounds. I betcha even the big simulators have them.  :unsure:

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You're right Devon :-)  (as usual ;-) )

 

And probably even that great fdm behind the DCS modules uses a tweaks / cheats too... I've read that a lot of tallent is required to bring the models to realistic behavior after all....

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You're right Devon :-) (as usual ;-) )

 

And probably even that great fdm behind the DCS modules uses a tweaks / cheats too... I've read that a lot of tallent is required to bring the models to realistic behavior after all....

On the Xplane Wikipedia article it says: http://en.wikipedia.org/wiki/X-Plane_(simulator)

Blade element theory has shortcomings, as it can sometimes be difficult to design an aircraft that performs precisely as would real-world aircraft.[citation needed] However, as the flight model is refined, the simulator can better resemble real-world performance, and aircraft quirks, and design flaws.

I suspect they mean tweaks. (or cheats)

 

I once went on one of my "random knowledge hunts" and read up on blade element theory until my eyes crossed (about 30 seconds!) :P

 

The impression I got was that you could add sampling points to refine the model, but that the computational resources required could easily get out of hand. I suspect Xplane strikes a calculated balance of accuracy and speed.

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