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ahinterl

Airliners more stable in the air in real world?

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As a real pilot I can confirm that maintaining stability in the sim is much more difficult than in real life.For example the VC10 in real life has a fly by wire (long before Airbus) and hydraulic combination with an integrated "feel" computer to make it a little heavier, being as it is a high performance a/c. Coupled with the high momentum of a jet a/c (which is not modelled in the sim)jets generally are very easy to fly. And, I can tell you from personal experience that landing at VHHX was a quite normal event even with cross winds. Because in the a/c you could feel the aeroplane and compensate. Whereas in the sim there is no feel. No feed back from the control surfaces at all. All you have are the visual cues which in themselves are like flying an aeroplane by looking through a keyhole in comparison to reality.vololiberista

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Guest bstolle

The question was if FSX airliners are too unstable or not.I agree that without the feedback and only tiny visual cues it's more difficult, but I don't think that the planes are too unstable.I'm surprised to learn that the VC-10 was a FBW plane! Didn't know that. Always thought the Concorde was the first FBW airliner.If you mean the hydraulic packs located in the vicinity of the flight controls....that was even earlier in the Vickers Valliant

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Just tried the default 737 and I didn't find her to be too unstable in pitch at all(turning behaviour is unrealistic but easy to correct).Pitch feels quite realistic to me.Best regardsBernt
Hi Bernt.Funnily enough, I've always thought the default 737 was OK though I couldn't say the same for the Lear or CRJ.What are you up to these days?

Cheers

 

Paul Golding

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Guest bstolle
Hi Bernt.Funnily enough, I've always thought the default 737 was OK though I couldn't say the same for the Lear or CRJ.What are you up to these days?
Hi Paul, Exactly. If you want I can e-mail you the changes for the FDEs concerning the turning behaviour. It's a real nice plane to fly and you are correct the Lear, CRJ and the especially the A320 aren't too realistic. The only other shortcoming with the 737 is the engine spool up rate, but as I've just finished the new FDEs for the Flight Replicas Me262 I've found a nice solution.The last patch for the Milviz Cessna 310 should be out soon and I've started already working on the FDEs for the next Milviz project. With the little remaining time I'm working on my first own FSX freeware plane, a PZL-104 Wilga35. Any news concerning a FSX 727? Are you still involved in FS projects?Best regardsBernt

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As a real pilot I can confirm that maintaining stability in the sim is much more difficult than in real life.For example the VC10 in real life has a fly by wire (long before Airbus) and hydraulic combination with an integrated "feel" computer to make it a little heavier, being as it is a high performance a/c. Coupled with the high momentum of a jet a/c (which is not modelled in the sim)jets generally are very easy to fly. And, I can tell you from personal experience that landing at VHHX was a quite normal event even with cross winds. Because in the a/c you could feel the aeroplane and compensate. Whereas in the sim there is no feel. No feed back from the control surfaces at all. All you have are the visual cues which in themselves are like flying an aeroplane by looking through a keyhole in comparison to reality.vololiberista
Also, to add to my earlier comments- in FSX when you do have the aircraft trimmed for level flight (and this takes using ALT-HOLD with the AP in some if not most instances, as discussed above), then you bank the aircraft, there is an instantaneous pitch down effect. When I trained for my instrument rating I had picked up real flying after a long hiatus of nearly 10 years since I had flown before, and my CFII continually balked at my climb from level flight when turning, until I identified this as a bad habit from FSX- as you need to apply nose-up input to the yoke on the sim to avoid descending. We discussed this at length after several flights. This is all connected to the lack of pitch attitude stability- if you don't pull back in the sim when turning you descend, AND your speed increases. Now, an aircraft is trimmed for speed, that's why you trim- and while eventually the nose of a real aircraft will start to fall in a turn with no correction (not talking steep turns here), if speed increases then the nose will tend to rise relative to the wing (as long as the angle of bank is not in excess of 40 degrees for a C172 where the over-banking tendency starts to become a factor).I'm not criticizing FSX, I'm just wondering why it has always been this way in a sim- and not just a desktop sim either, as I mentioned before, a multi-thousand $$ Frasca sim does the same. I don;t know enough about how sims work to know why such a critical relationship cannot be better simulated, after all- this attitude stability stuff goes right back to basic stick and rudder theory that pilots get rammed down their throats by frustrated instructors in the first hours of flight.Interesting topic! Bruce.

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I think there are a multitude of different mathematical models to simulate air dynamics. None of them could simulate reality 100% correctly. They all are an approach to what exists in the real world, they model highly complex procedures. They are what they are, models and approximations. Maybe one day when computers are powerful enough there will be an increase in the level of fidelity. I don't expect that FSX simulates a real plane 100%, I just want to dampen some nasty things that annoy me for a long time. The pitch stability problem is high up in my list, guess I'll start to play with config file editing and see where I end up...

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The problem is not really down to mathematical models although they have to be close. The real problem is complete lack of feel. As a pilot you feel the aeroplane. It is telling you what it wants to do and the pilot's control inputs aim to prevent the aeroplane from diverging from the intended trajectory.Go up with a real pilot on a gusty day and you will see him or her constantly adjusting the control surfaces and if he/she is good the wings will stay level. That is just one example. The feedback that an aircraft gives you as a pilot and how you respond is what makes you a pilot and not a simmer. This will never be modelled in the sim so from that aspect it most definately NOT as real as it gets!!!!!!vololiberista

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Guest bstolle

@bruce>This is all connected to the lack of pitch attitude stability- if you don't pull back in the sim when turning you descend, AND your speed increases. >Now, an aircraft is trimmed for speed, that's why you trim- and while eventually the nose of a real aircraft will start to fall in a turn with no correction, if speed increases then the nose will tend to rise relative to the wing If you trim for straight and level flight is not possible to maintain the altitude and/or speed without compensating for the turn. The lift vector is pointed straight up during level flight, but banked during a turn.Hence the vertical component is shorter as the banked part is needed for pulling the plane through the turn. You need to compensate for that.@ahinterl>I don't expect that FSX simulates a real plane 100%, I just want to dampen some nasty things that annoy me for a long time. >The pitch stability problem is high up in my list, guess I'll start to play with config file editing and see where I end up...As vololiberista pointed out, it's more difficult (even a 'real' sim is more diffcult to fly because it can't replicate the 'feel' and motion exactly), but this is NOT a pitch stability problem!You can make it easier but less realistic by simply pumping up the pitch stability in the cfg file.@vololiberistaThere's simply (luckily!) no substitute for flying a real plane and even the best multi million dollar sims are more 'procedure trainers' than 'flight sims'

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Thank you all for your input. Guess I do the ATPL and buy me a customized airliner once I crack the lottery... :(

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@bruce>This is all connected to the lack of pitch attitude stability- if you don't pull back in the sim when turning you descend, AND your speed increases. >Now, an aircraft is trimmed for speed, that's why you trim- and while eventually the nose of a real aircraft will start to fall in a turn with no correction, if speed increases then the nose will tend to rise relative to the wing If you trim for straight and level flight is not possible to maintain the altitude and/or speed without compensating for the turn. The lift vector is pointed straight up during level flight, but banked during a turn.Hence the vertical component is shorter as the banked part is needed for pulling the plane through the turn. You need to compensate for that.
Yes- I know, it's the distortion of over-emphasising this in the sim that is the issue.But- as you say:"There's simply (luckily!) no substitute for flying a real plane and even the best multi million dollar sims are more 'procedure trainers' than 'flight sims'". I agree, but in this age of virtual worlds, it's a shame that something that seems to transgress at least several sim platforms can't be at least made to be behave more realistically. Also agree with you- FSX is great for procedural stuff, sure beats chair flying :)Thanks, Bruce.

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