X-Plane vs. FSX

[dbrucem 0]

I"m sure what Ed intended to say was that an aircraft can stall in ANY ATTITUDE when the wing exceeds the critical angle of attack.

[GoranM 3,762]

Ed, you are wrong. A stall CANNOT and WILL NOT happen until the critical angle of attack is reached and exceeded. If what dbrucem is saying is what you mean, then yes, correct. It can happen at any ATTITUDE. Wind can be variable and sudden updrafts can cause stalls in an aircraft that is flying straight and level. But these updrafts CAN actually cause the AoA to go past critical. So what I am saying is STILL correct and what you are saying (Stalls can happen at ANY AoA) is completely incorrect. I think you're confusing FLIGHT PATH with WIND DIRECTION.If an airliner loses altitude, it can be because of wind shear, thermal pockets, updrafts, etc... The theory is still the same. These things cause the wings AoA to go past critical. Beginner pilots (as you assumed I was) are taught basic stall recovery as part of their GFPT (The first 30-35 hours of learning). At least they do in this country. Instead of arguing the point with me, please read up on stalls and what causes them. It all comes down to critical AoA.

[GusRodrigues 1]

Nose down to recover is the first thing that should be done. A stall is a result of excessive AoA (beyond the critical AoA). That AoA needs to be reduced. Then smoothly apply power, and if a spin is happening, apply opposite rudder.

Incorrect. A stall is a result of not enough lift being generated. It can happen at any angle of attack. You've just made a mistake a great deal of (real world) beginner pilots make.

...WHAT?if it were at any speed, it would be okay, but... this is wrong.(critical mach can stall a wing portion above a certain speed, reducing the overall Critical AoA, but... wow.) Edited February 2, 2012 by Omykron

[Alan_A 1,650]

My system is an Intel quad core Q9550, with 4 gigs of DDR3 and 3 X 9800GTX+ in an SLI configuration. Windows 7 x64bit.

Not to be critical, just to be direct - that was a top of the line system about four years ago. The old (pre-i7) quads were and are great performers when overclocked, and offered very good value, but there's no way that system can run FSX maxxed out. Even my system can't, and from what I can gather the Sandy Bridge CPUs, as capable as they are, are still overmatched in some FSX locations. Ivy Bridge may be the first generation to be able to handle maxxed FSX with ease... though we'll have to see. The 9800, likewise, is an older video card. SLI won't help with FSX, since it's not designed to take advantage of SLI, so you're only getting the benefit of one card that's a couple of generations in the past.You can certainly enjoy FSX or X-Plane on your system and get a lot out of it - but not with sliders to the right, no way. Back them off, follow NickN's advice, and tune your system for smooth running. You'll fly better and have more fun.For low and slow, you might want to try a good payware 172, or a Cub like A2A's, or just the default 172, which is pretty decent.Again, not criticizing, just observing that in purely technical terms, you're just pushing your system way beyond the limits of what it can do.I'll step aside now and let the debate about stalling characteristics roll on... Edited February 2, 2012 by Alan_A

[GoranM 3,762]

I'll step aside now and let the debate about stalling characteristics roll on...

I'm actually amazed that it's even a debate. It's not like "My physics is better than your physics!"It's Ed Wilson, programmer of Eaglesoft aircraft add ons, arguing with me, and all the aviation and aerodynamics books I have, on how a wing stalls??!! I'm still sitting here wondering what the hell he is arguing about! Ed, maybe it's the country I am in, but when learning to fly in Aus, we are told to NEVER let go of the controls under ANY circumstances. I guess flying an Airbus is an exception, but I'm talking about PPL's. If you're on take off, and you pull up a little too high and experience a power on stall, you DO NOT let go of the controls. You lower the nose (within reason) to decrease the AoA and trade altitude (or in this case, climb rate) for airspeed. Obviously, you do not lower the nose to the point it is below the horizon, but you DO lower it to gain airspeed and decrease AoA. The same can be said in any stall. Point being, you lower the nose. I've even spoken to my old flight instructor who holds an ATPL and completed a Masters of Aviation at the University of NSW (he has over 4000 hours in various aircraft) and flies for a major Australian airline and he's just as flabbergasted as I am that you're trying to justify your argument.Is it possible that you were wrong in your terminology? That you really meant SPEED or FLIGHT PATH and not AoA?

[60North 120]

First of all, with regard to airliner deep stall characteristics, there is no public information about this andobviously extremely few have experienced it and are still alive. Second, not even the $15 million full motion simulators model this (I've tried).I've also analyzed FDR data from accidents reports, but it's really hard to draw any conclusions from them.Those who claim to know how an airliner behaves in a deep stall most likely have no idea what they aretalking about unless they work in the inner circles of Boeing or the like.So how an airliner deep stalls is only of pure academic interest with regard to airliner simulation.(unless you have some bizarre interests)In X-Plane we can control the initial stall behavior very accurately on a clean wing which is the usual stall case.Like how fast/much the nose drops etc. Either by the real airfoil data or reverse engineering. We can also controlthe entry point of deep stall, but beyond there we have little control of what happens.With flaps things get a lot more complicated since the clean airfoil properties don't apply anymore. Extending flap+slat meansyou have created a completely new airfoil with regard to stall characteristics. No sim does this very accurate, it's just too complex.Imagine how many combinations of flap types, slat types, slots, gaps, droop, deploy angle combinations on multiple slotted flaps etc etc.With regard to how airliner stalls can occur and how to do a recovery, I suggest reading this;http://www.boeing.co...ly/fo01txt.htmlM

Edited February 2, 2012 by MortenM

[fvapres 7]

A stall occurs due to the fact that the air no longer flows smoothly over the wings and begins to separate from the wing. FLIGHT ceases once lift is not enough to counteract the weight. In order to regain newtoninan lift from air that impacts the lower surface of the wings, the pilot pitches up as the relative wind comes from below the chord line of the wings, increasing angle of attack. Once the critical angle of attack is achieved, the air flow over the wings separates enough that no airspeed allow enough air to flow over the wings smoothly enough to generate enough lift to counteract the weight of the aircraft.Stalls can occur at any airspeed but due to the fact that the relative wind flowing over the wings cannot support smooth airflow.An aircraft like the C90 has a huge thrust/weight ratio and engines that can build up thrust quickly, thus it can usually power out of most stalls as long as the pilot is not continuing the bad control inputs that caused the stall aoa in the beginning. An aircraft like a 737 or any turbofan or light single or twin, dropping the nose (not dramatically, but slightly) to regain airspeed and decrese the angle of attack to get the air flowing smoothly over the wings while giving the engines time to spool up and generate thrust. There is a big difference in an aircraft weight as well when a heavily loaded airliner begins to stall, to get the thrust enough to accelerate the mass versus a near empty airliner, the thrust to weight ratio would determine how necessary dropping the nose would be.

[Johnny Thunder 0]

Intresting debate about stalls, funny thing is that the FAA is talking about changing the rules for stall recovery and this same debate is going on there as well...Maybe they played a lot of X-plane and where like, do you think this is more realistic then FSX?At anyrate, I'm pretty sure X-plane gets it right and FSX gets it wrong, but I guess we all would need to go do loops in a real 747 to find out, woulden't we?Speeching of which, I just did some loops for the first time in the 747 in X-plane, and stall recovery is a million times easyer then FSX. I started the loop at 3000 feet going 360knots and at 9000 I was upside down and backwords in a total stall with no airspeed whatsoever. And I almost "felt" the 747 fall as it lost all forward momentom, but as it started to fall the wind resistence built up on the hall, as it did, I contuned to pull the stick into my lap prying to recover before I hit the ground.In FSX if you tried a loop at 3000 feet in the 747 you would be dead. At this point the 747 would start to fall like a rock and the only stall recovery is to point the noise straight down to the earth and wait until you get to 140 knots before you started your pull out or else you would just pull up and the plane would continue to fall down like a rock and your wings don't even exsist.However X-plane and FSX differ here because unlike FSX, X-plane is an actual wind/arodynamics simulator. It's trying to figure out how any object would fly, even an upside down stalled 747 that's falling like a rock out of the sky has some arodynamic simulation that can be calculated. It, like all airplanes create force fields of wind resistence as it moves about the sky, like a ship out of water.I could still control the 747 and contiune my loop. Sure the same buzzer went off, and yes the plane did initally fall like a rock, but as the force fields of wind resistence built up on the hall of that big old heavy 747, it pushed the plane back up and forced it into level flight. I ended up recovering at 7000 feet... and I was like man, I can do loops in a 747 all day!You can't do that in FSX, it's basicly impossable to loop the 747 unless you turn off sturctural failures and start the loop at 500 knots, which one is more realistic? Again, dose anyone wanna go loop a 747, because I totaly do after what I've learned in X-plane just now.

Edited February 5, 2012 by Johnny Thunder

[WarpD 824]

If you think doing a loop in a 747 is accurate.... let alone at 3000'... well....

[Guest HowardHughes]

It's not that I can't recover from stalls in FSX, I can. It's just that compared to X-plane it's massivly more diffculy to recover, X-plane gives you a lot more feedback when you are in a stall and it's genaraly easyer to recover. When I was looking at senery I was flying really low and slow, I was also flying the 737 which is not the best choice for low and slow travels. Still, In X-plane when I get into the stall I can useally just flick the noise down, add power and recover rather quickly, maybe I'll drop 400 feet but that's about it. In FSX unless I recover the instent I hear the stall buzzer, I will general fall 500 to 1600 feet before I recover. I think it's because FSX stops genarating any lift when you fall bellow your stall speed, so you need to speed up to above your stall speed in order to get any lift at all. X-plane keeps genrating lift off the body of the plane all the time, even when stalling. So when your in a stall the airplane is still genarating some amount of lift bellow it's stall speed which feels more realistic IMO; It's also a lot easyer.

In a 737 deep stall you'd lose a lot more than 300 feet. Why do you suggest that this is more realistic?

Incorrect. A stall is a result of not enough lift being generated. It can happen at any angle of attack. You've just made a mistake a great deal of (real world) beginner pilots make.

No, you are wrong. Stalling can't happen at any angle of attack - it can only happen past certain angles of attack. It can happen at any airspeed though. This is the first thing taught in regards to the flight envelope during your training. I knew this after 10 hours in the air.

At anyrate, I'm pretty sure X-plane gets it right and FSX gets it wrong, but I guess we all would need to go do loops in a real 747 to find out, woulden't we?Speeching of which, I just did some loops for the first time in the 747 in X-plane, and stall recovery is a million times easyer then FSX. I started the loop at 3000 feet going 360knots and at 9000 I was upside down and backwords in a total stall with no airspeed whatsoever. And I almost "felt" the 747 fall as it lost all forward momentom, but as it started to fall the wind resistence built up on the hall, as it did, I contuned to pull the stick into my lap prying to recover before I hit the ground.In FSX if you tried a loop at 3000 feet in the 747 you would be dead. At this point the 747 would start to fall like a rock and the only stall recovery is to point the noise straight down to the earth and wait until you get to 140 knots before you started your pull out or else you would just pull up and the plane would continue to fall down like a rock and your wings don't even exsist.However X-plane and FSX differ here because unlike FSX, X-plane is an actual wind/arodynamics simulator. It's trying to figure out how any object would fly, even an upside down stalled 747 that's falling like a rock out of the sky has some arodynamic simulation that can be calculated. It, like all airplanes create force fields of wind resistence as it moves about the sky, like a ship out of water.I could still control the 747 and contiune my loop. Sure the same buzzer went off, and yes the plane did initally fall like a rock, but as the force fields of wind resistence built up on the hall of that big old heavy 747, it pushed the plane back up and forced it into level flight. I ended up recovering at 7000 feet... and I was like man, I can do loops in a 747 all day!You can't do that in FSX, it's basicly impossable to loop the 747 unless you turn off sturctural failures and start the loop at 500 knots, which one is more realistic? Again, dose anyone wanna go loop a 747, because I totaly do after what I've learned in X-plane just now.

A genuine question - are you being sarcastic?The fact that you can loop a 747 at 3000 feet at 360 in XPX makes it more realistic? Edited February 5, 2012 by HowardHughes

[Guest HowardHughes]

I'm actually amazed that it's even a debate. It's not like "My physics is better than your physics!"It's Ed Wilson, programmer of Eaglesoft aircraft add ons, arguing with me, and all the aviation and aerodynamics books I have, on how a wing stalls??!! I'm still sitting here wondering what the hell he is arguing about! Ed, maybe it's the country I am in, but when learning to fly in Aus, we are told to NEVER let go of the controls under ANY circumstances. I guess flying an Airbus is an exception, but I'm talking about PPL's. If you're on take off, and you pull up a little too high and experience a power on stall, you DO NOT let go of the controls. You lower the nose (within reason) to decrease the AoA and trade altitude (or in this case, climb rate) for airspeed. Obviously, you do not lower the nose to the point it is below the horizon, but you DO lower it to gain airspeed and decrease AoA. The same can be said in any stall. Point being, you lower the nose. I've even spoken to my old flight instructor who holds an ATPL and completed a Masters of Aviation at the University of NSW (he has over 4000 hours in various aircraft) and flies for a major Australian airline and he's just as flabbergasted as I am that you're trying to justify your argument.Is it possible that you were wrong in your terminology? That you really meant SPEED or FLIGHT PATH and not AoA?

In regards to letting go of the controls, whilst I don't think it is 'taught' anywhere, I believe some aircraft are designed so that if you do let go of the controls (even in a fully developed stall) it will naturally recover. It'd mean more height loss than if you followed the appropriate manual recovery, but the weight and balance is sufficient for the aircraft to sort itself out. A few trainers have this properly. I believe the C150/152's can do it.In regards to lowering the nose, on many aircraft you would want to lower it well below the horizon.

[Johnny Thunder 0]

The main reason I think X-plane is more realistic is because it's easier to land. If FSX was the more accurate candidate for real world flying, airplanes would be falling out the sky so much, no one would be allowed to fly them.Edit: Also every acrobatics pilot would be dead.

Edited February 5, 2012 by Johnny Thunder

[JasonD210 0]

Back to the original question, I'm sure X-plane has a more fluid feel than FSX, but that's not the only factor you can compare. From what I have heard from developers, FSX is a more sturdy platform to develop on. They say it's easier to develop on, and that some things just aren't possible in X-plane when it comes to simulating instruments and avionics. Engine modeling is also hard to according to A2A.I think many frown on X-plane because it is a small "indie" sim, and aren't sure of where it's going in the future or what Austin will do.

[LAdamson 240]

The main reason I think X-plane is more realistic is because it's easier to land. If FSX was the more accurate candidate for real world flying, airplanes would be falling out the sky so much, no one would be allowed to fly them.Edit: Also every acrobatics pilot would be dead.

To make this short .....Real planes will fall to the ground if you stall them. Don't count on a 747 completing a loop, with the yoke pulled all the way back, and airspeed at 0 at the top of the arc. The hull just isn't going to allow the airplane to fly, with wings in a stalled condition. The default XP 747 looping exercise isn't one of realism. I tried it too. BTW--- I also thought the 747 "test" was a bit sarcastic. If not, Boeing, could team up with X-Plane to create safer airliners..... Edited February 5, 2012 by LAdamson

[Johnny Thunder 0]

If Boeing gave me the worlds first Acrobatic 747, I'll would totally go and do that loop.As it stands, the wings might rip off!

Edited February 6, 2012 by Johnny Thunder