Most Realistic flight modeling

[warchild]

Wellll, if you can make several seperate printouts of the blueprint and use a micrometer, scale, and slide rule, AND you have a masters in aerodynamics, you might be able to extrapolate most of the data just from the design in a few years. But lets face it.. The Russians had a real B-29 in their possession and even taking years were never able to reverse engineer it to where they had a working B-29.. They had something that flew, but it wasnt a B-29. it just looked like one..
I dont know about anyone else here but i sure dont have a degree in aerodynamics, and its been decades since i used a slide rule.. i got a calculator that tells me if the syntax was wrong, but theres very little to allow for cross checking equations. That introduces massive inaccuracies that sometimes go unaccounted for.
However, external design only counts for so much. i can remember when i was working on the grumman goose, that nothing worked right until after i installed a toilet.. it helped to counter balance the weight of the engines while keeping the Cg in the correct position. i probably underestimated the weight of the toilet though..
All of us FDE engineers put our hearts and souls into what we're doing. We do the job that no one in their right mind would want to do. It's almost as bad as programming gauges ( a seriously thankless job that should be recognized more ). But without detailed diagrams and specifications, and time, there is no way we can produce accurate models. We can make a pretty good simulacrum though..

 

[Sundog]

Wellll, if you can make several seperate printouts of the blueprint and use a micrometer, scale, and slide rule, AND you have a masters in aerodynamics, you might be able to extrapolate most of the data just from the design in a few years. But lets face it.. The Russians had a real B-29 in their possession and even taking years were never able to reverse engineer it to where they had a working B-29.. They had something that flew, but it wasnt a B-29. it just looked like one..
I dont know about anyone else here but i sure dont have a degree in aerodynamics, and its been decades since i used a slide rule.. i got a calculator that tells me if the syntax was wrong, but theres very little to allow for cross checking equations. That introduces massive inaccuracies that sometimes go unaccounted for.
However, external design only counts for so much. i can remember when i was working on the grumman goose, that nothing worked right until after i installed a toilet.. it helped to counter balance the weight of the engines while keeping the Cg in the correct position. i probably underestimated the weight of the toilet though..
All of us FDE engineers put our hearts and souls into what we're doing. We do the job that no one in their right mind would want to do. It's almost as bad as programming gauges ( a seriously thankless job that should be recognized more ). But without detailed diagrams and specifications, and time, there is no way we can produce accurate models. We can make a pretty good simulacrum though..

Actually my primary discipline was Aerodynamics and my secondary was Propulsion. Although, sadly, it's only a measly old Bachelors degree. BTW, the B-29 part is a bad analogy, because their problem wasn't in understanding how it flew or how it worked, it was in being able to duplicate the manufacturing technology to make it. BTW, it was the Tu-4 Bull, but I do know what you mean.

Having slaved over FDE's myself, I know. That's how I've learned what I've learned. Well that and tips from the FDE masters and all of the forums available in that regard. But jets are sort of new to me, in terms of the FDE propulsion section. I have excellent data I'll be able to reference on newer jets, it's the older ones I'm having the trouble with, at least in terms of engine data. So many designs, so little time...

 

[warchild]

So many designs, so little time...

heh.. so few models.. Just more remakes or more remakes.. thank gods for the Bleriot's and other dawn of flight aircraft.. but that goes back to the thread about what planes we need in fsx.. not that anyone will make them of course..

 

[Brett_Henderson]

My point is... that even if you ARE a PHD in aerodynamics.. and have access to perfectly accurate drawings.. and even have a stand-alone, computerized wind-tunnel with the ability to control the virtual, barometric pressure so that you can come up with a set of power-plant parameters that test out on this virtual dynomometer for accurately modeled thrust for the complete range of airspeed/altitude/ N#s ... and then you dial in the exact geometry for the model.. weights, MOIs, apexes, surface-areas and even control-surface deflections..........................................


You will not end up with an accurate performance envelope inside of the MSFS flight-model.

I'm not saying that you cannot come up with reasonable accuracy.. I'm just saying that if your model ends up satisfying the knowledgeable sim-pilot... I.E.. uses up the proper amount of runway to reach rotation-speed per the loading (and will not climb before that speed).. and has it's vertical speed peak AT Vy (while at climb-power).. and has that vertical speed fall off realistically with gains in altitude.. and will maintain accurate, level-flight cruise speed (at accurate cruise-power settings)... and will not exceed maximimum speed at max power settings... and will finally maintain realistic rates of descents per various descent power settings (down to and including flight-idle).. it's gonna have parameters like; wing-efficiency/parasitic-drag/induced-drag/thrust, and most of the Flight_Tuning paragraph entries so mutilated, that your research beyond "close enough", is pointless.

I've even had to alter actual geometry (wing area, control-surface apexes), becaue flight-tuning tweaks got large enough to alter OTHER parts of the performance envelope beyond tollerable.

I decided long ago, that what the sim-pilot experiences with his hands on the yoke/throttle, is more important than realistic "appearances", in fligh-model documentation.

 

[warchild]

i tend to agree Brett.. *I've wanted a wind tunnel since the time i was working on the F-20. but those are the realm of indy car designers and colleges and out of the reach of the common pockebook such as mine.. but i tend to think that even with it, your right. Mind you, i dont WANT to think that. I refuse to accept that, but your most likely right..
Over the Years Paul and I along with others have pushed FSX to its limits, and it's pushed back.. Wever done flight models that were so tight that if you changed any number by so much as one one hundredth it would change the entire flight model. That was the P-36 before we passed it off for completion.

the bottom line though is that no matter how much we put into a model, its only going to be so close. we can model parasitic drag, and all those other variables you mentioned, but, its what we cant model that has the greatest effect ( the traveling center of lift and the traveling center of balance and other non stationary variables ) that throw a good sized spanner into the works..

I personally never mess with flight tuning. i set everything to one and all the variables to zero before i start my calculations ( and i never use third party programs ot excel plugins to do it for me ), but the people who sell the final product i'm developing for may. They have a keener interest in their market than i do.. Dont get me wrong, i love this community dearly, but i love accuracy more. The developers may tweek things a bit. Thats fine.. Well, except in one case.. but i'll still go on beating my head against the wall ensuring that my work is the absolute best i can do.. I cant be complacent.

A flight model is a set of interlocked relationships. its almost organic.. Like eating.. you get too much of any one thing, it tosses another part off.. getting the balance right though. Thats the hard part.. thats what takes thousand hours or more..

 

[Piglet]

Anyone here ever had the "Fly!" series of sims? I still read thru the manuals. Those manuals were thick with good info. Wish a new version would come out, with open end coding for add-ons.

 

[dominique]

Anyone here ever had the "Fly!" series of sims? I still read thru the manuals. Those manuals were thick with good info. Wish a new version would come out, with open end coding for add-ons.

Fly! died with its creator Richard Harvey in 2003. It was a wonderful sim that was very open to users as most of the scenery and FDE parameters were in .txt type files and compiled at the beginning of a session.

Some fans have been trying to revive it throughout the years. They have a forum at Avsim.

 

[ManuelL]

I think flight sims dedicated to a certain "branch" of aviation (e.g. RoF, Condor, Black Shark) will most of the time have the best flight models. They can focus on the physics and systems that are specific for this type of aircraft and often are limited to a very small part of the world.

When it comes to a sim that covers the whole world and all types of aircraft, I think FSX still allows for the most realistic flight models. The weekness of FSX in my opinion are aerodynamic extremes of the flight model (stalls, high AoA situations) where X-Plane may be a bit superior.

 

[bstolle]

ok..Sit down, grab some coffee, take your blood pressure medicine and think a bit.. Thats all i ask. Please..
I've read a complaint in here about FSX planes flying like they were on rails.. Thats true, and i'll tell you why.. Its because you people dont want real.....

Someone mentioned PMDG as having realistic flight models?? Please.. Their FDE's are nothing but Zero's. they use FSX's main engine to determine the flight characteristics on every plane they have, so you are flying the very same plane every time you fly irregardless of what it looks like.

.....The Little Bombardier RJ-200 stalls just above 40000 feet. The engines flame out. If a specific set of conditions arent met ( turbine speed etc ) those engines will not start back up. More than one RJ has been lost because of that, and it keeps happening because there's idiots out there who think pushing the plane above 40000 feet is some kind of macho milestone..Pam

I disagree on (at least) the above points.

If there's no turbulence and the plane trimmed correctly, many planes fly like on rails. That doesn't imply that they are non maneuverable tanks like some highly praised GA twins for example.
I estimate that at least 75% of the FSX users are non pilots and a lot more which haven't flown the type they are buying. I doubt that they want a 'dumbed down' variant of any plane.
I'm sure that most of are eager to learn to handle a 'difficult' plane.
Unfortunately most people post only when they complain so that might produce a wrong picture about the customers and what they want. Most people excpect a flight sim and not a flight game.

What's wrong with PMDG using the 'main engine'? What should they use to get real behaviour?
I also work just with the air and cfg files and haven't encountered too many problems.

Why should a CRJ 200 stall at 40000ft and why should the engines flame out ???
More than one has crashed for that reason? How many and how do you know that it keeps happening?
It's certified for 41000ft and I've been there a few times because the tailwind was that strong that it made sense to be up there.
If you are light and on a ferry flight why not fly at 40000ft?
You don't get the chance to be up there with the CRJ very often.
On the other hand I've been in the situation where I couldn't even maintain 30000ft because the cruise tables were a bit on the optimistic side to put it mildly.
This has NOTHING to do with machoism
The CRJ 100 is the worst plane I've ever flown with the worst checklists and lots of wrong information coming from the plane and engine manufacturer, so I'm not too happy about you calling airline pilots idiots....

Still no blood pressure pills needed, yeah!

 

[AndyE1976]

I think this thread is very similar to the 'which plane makes you feel there' thread, at least for non-RW pilots like me.

Warchild is right that it is our perception of what a plane should fly like that determines our evaluation of an 'accurate' flight model, although part of that also comes from manufacturers who sell their aircraft with claims of 'flight tested by real _____ pilots' (insert aircraft name).

When I see that claim I have no reference point to contradict it - I've spent 30mins at the controls of a C152 about 20yrs ago, so I'm not qualified to say whether or not the PMDG 747, A2A B17 or anything else flies as it should do. I'm left with my impression of does it perform as I would expect it to.

I think that the A2A approach of accu-simming aircraft in expansion packs for those that want more realism is a good way to go. I'd pay for a more accurate flight model since for me the attraction of FSX is being able to experience aircraft I wouldn't have a hope of flying in real life.

 

[warchild]

welll, i would humbly submit... http://www.iasa.com.au/folders/Safety_Issues/others/PinnacleCRJ2.html
The Faa and NTSB had a field day with that one.. you can be sure of it..

Why Not use the main physics engine for every single plane??? because although the engine is quite capable of making use in the differences between wingspan wing root fuselage length and various other physical attributes, it doesnt take into account any of the myriad of differences that exist between each plane. For example, it doesnt model the difference between a CFM-56 and a JT-3. it treats both of them the same, if you dont have anything but zero's in your air file.. Thats why i use air files. I want it as true as i can possibly make it..

PS.. The CFM-56 is used on a 737, the JT-3 powered the SR-71 at over mach 3. ( for those who didnt know )

PPS.. I didnt call airline pilots over all idiots. I call this group of idiots idiots..

ppps. this discussion goes OT, but covers the above mentioned's causes and effects.. it is done by real pilots.. http://forums.jetcareers.com/technical-talk/107924-crj-200-climb-speed-envelope-slow-cruise.html

 

[Panther_99FS]

Which one is the most FUN :ques:

 

[warchild]

Falcon 4.0..

 

[bstolle]

That's an easy one. Flying in a war scenario isn't fun at all, x-plane is still very sterile and FSX has easily the highest immersion factor!

 

[Major_Spittle]

My question was more of a " which FS models flight the best " in terms of start out with an airplane at 20,000ft sitting still with no power and drop it and see what happens.

Put a tail wind of 80 knots at 20,000 ft and drop it, side wind....... I'm talking more about accuracy in modeling the physics of flight, not duplicating a particular airplanes specs, stall speeds and such. I could care less if the cessna 172 is stalling at a faster airspeed or takes more runway to take off because I will never fly a cessna 172, but is the simulator duplicating flight? when there is a tail wind gusting does the plane react to it correctly, side wind, prop wash, drag from lowering landing gear, having fuel emptied in one wing and full in the other, speed/lack of airflow over control surfaces....... Which FS do you have to "fly" the airplane in it the most in accordance with real world physics.

To me X-Plane and ROF are better at this than FSX. FSX is prolly better (depending on aircraft) of duplicating " flying by the numbers flight " of particular aircraft. Just don't stall that airplane inverted with a tail wind and expect it to react in accordance with real world physics or your inputs to react in accordance with physics under those circumstances. (with any FS, but ESPECIALLY FSX).

And I disagree that plane feel like they are flying on rails. They feel stable if flying underpower and a speed in which their aerodynamics stablize them, they should feel like on rails while crabbing, slipping, stalling, flaring....... I have rode with a crop duster, I remember nothing better than the feeling of the planes wings washing during a hard pull back from a dive and then hearing/feeling the wings "pop" when they finally loaded with air. The feeling of stability from the airflow giving way to the balance of the aircraft at the top of a wing-over.

 

[fliger747]

I was somewhat involved in PMDG's development of their 747's for FSX. Having some 12 years flying captain on said airplane I do think they are pretty good as far as performance and flight manners. Aircraft with such a myriad of high lift devices are not particuarly easy to model in FSX.

Actually most of the flight dynamics are hidden in the aircraft module, using much wizardy to get around the limitations of the FS engine. Just looking at the .air and .cfg files won't tell much of the story.

Cheers: T

 

[Ken Stallings]

RoF feels "right" to me. Those early planes were quite the handful to fly. But RoF has only modeled the 1914-1918 era, so far. How would that sim represent a FW-109, or F-86? Or Ken's C-310R? Comparing "study sims" with "survey, or general" sims is inconclusive, at best.

I was about to mention that point myself, but figured I had already said enough in my first post!

But, you are right. Those World War I fighters (especially the Camel and Tridekker) were absolute death traps. I'm not sure a flight sim could make them unstable enough to be realistic!

Ken

 

[warchild]

I was about to mention that point myself, but figured I had already said enough in my first post!

But, you are right. Those World War I fighters (especially the Camel and Tridekker) were absolute death traps. I'm not sure a flight sim could make them unstable enough to be realistic!

Ken

get me drunk enough and i can make any plane fly like C%%p.
truth told, now that i have a grasp on the su-37 i can say that yes, the instabilities can be programmed in in fsx. i dont do anything with X plane so i dont know.. but with a little effort, those negative characteristics could be modeled,. it just isnt easy..

 

[Ken Stallings]

welll, i would humbly submit... http://www.iasa.com.au/folders/Safety_Issues/others/PinnacleCRJ2.html
The Faa and NTSB had a field day with that one.. you can be sure of it..

Why Not use the main physics engine for every single plane??? because although the engine is quite capable of making use in the differences between wingspan wing root fuselage length and various other physical attributes, it doesnt take into account any of the myriad of differences that exist between each plane. For example, it doesnt model the difference between a CFM-56 and a JT-3. it treats both of them the same, if you dont have anything but zero's in your air file.. Thats why i use air files. I want it as true as i can possibly make it..

PS.. The CFM-56 is used on a 737, the JT-3 powered the SR-71 at over mach 3. ( for those who didnt know )

PPS.. I didnt call airline pilots over all idiots. I call this group of idiots idiots..

ppps. this discussion goes OT, but covers the above mentioned's causes and effects.. it is done by real pilots.. http://forums.jetcareers.com/technical-talk/107924-crj-200-climb-speed-envelope-slow-cruise.html

The talk about idiots suddenly reminded me of Johnny Damon's claim that the Red Sox were "just a bunch of idiots," because they didn't put any stock in the so-called "curse of the Bambino." Funny thing -- these idiots killed that curse by winning the World Series that year and putting the Yankees on notice that their mojo was nojo by coming back from a three game to zero deficit to win the ALCS.

But, anyway ... I digress!

I think the only way to make a particular aircraft accurate is to have pilots who fly that actual aircraft type and model to "wring it out," by flying it and making detailed observations about how well it matches the real airplane.

If you can get a good partnership between real-world pilots and talented FDE modelers, then you can achieve really nice results. But, while I don't mean any insult, the only way to know is to recruit those who fly the actual aircraft types and models.

It's not merely matching performance tables either. For two reasons this is true. First, let's face hard reality, manufacturers in the dog-eat-dog of GA often outright lie in the performance tables! Yeah, I know, sacreligious! But, it's true!

Also, even if you nail the real world numbers plum, there's also the point about doing it accurately! That requires a measurement of feel. One example is modeling what happens when the first notch of flaps are dropped at a given airspeed. You need a real-world pilot who has experienced the result to tell the FDE modeler if the reaction is right in immediate pitch-up (or down) and altitude plus airspeed change.

When the plane stalls, how does it react? That's not in a manual. It takes actual experience to measure the virtual replication. So, again, I say FSX can achieve very realistic results. But, it takes a lot of tweaks and tailoring. And yes, due to some limitations in the code for FSX, it also means perfection is not possible. You just try to make the compromises as small as possible and hope the real-world pilots don't complain too loudly!

Cheers,

Ken

 

[delta558]

I don't know that "death traps" would really be a suitable phrase for the early machines, it was probably more the inadequate training time during the first world war. Okay, they may not fly in such a straightforward manner as many modern machines but take, for example, the Shuttleworth collection - they have a large number of aircraft of that era and a very impressive safety record. Worst I can remember is engine cowlings detatching from the Sopwith Triplane.