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IsaacC

Hydraulic suspension on Landings

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1st Post.When traveling I've often experienced the feeling of the aircraft dropping on its hydraulic suspension after the wheels have kissed the ground.Is it possible to simulate this? or is it already possible in PMDG aircraft. I've tried some very soft landings on the MD-11 and 747 and have been unable to reproduce this effect.

I'm sure you guys understand what I'm getting at.Isaac

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I am sure it would be possible. If you set the aircraft down gently enough with all the vibrations and other movements that happen during landing though it would be barely noticeable.. Oleo (nitrogen/hydraulic) filled struts will compress with little rebound unless you take them to max compression and there is not sufficient force to hold them there. Then the struts will try to balance out with the weight of the aircraft. They would have to answer the FSX aspect of it, but overall I would say you would need more of a violent landing than a gentle one. Even then FSX on its own will not reproduce the rebound in the struts that I have seen.

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I am sure it would be possible. If you set the aircraft down gently enough with all the vibrations and other movements that happen during landing though it would be barely noticeable.. Oleo (nitrogen/hydraulic) filled struts will compress with little rebound unless you take them to max compression and there is not sufficient force to hold them there. Then the struts will try to balance out with the weight of the aircraft. They would have to answer the FSX aspect of it, but overall I would say you would need more of a violent landing than a gentle one. Even then FSX on its own will not reproduce the rebound in the struts that I have seen.
What I believe he is refering to is the deployment of the ground spoilers... Gentle landing of not, you're going to feel the spoilers deploy.

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Why would you feel the spoilers? I have done many of idle reverse thrust landings and you don't feel the spoilers. Not from the cockpit anyway.JackColwill

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It would be cool to have that simulated in FSXI'd also like to see the effect of keeping the nose up for as long as possible to slow the plane down. A pilot friend told me that it's more effective than spoilers and reverse thrust

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Is it possible to simulate this?
I doubt it very much. Ole struts is all about what you feel through your seat-of-the-pants, as far as I know FSX doesn't come with its own $500 K motion system. NASA does this sort of simulation exceedingly well in its vertical motion sim (VMS) here where I work at NASA Ames but it only costs a ten million $$. Next time you ask if you can simulate smell of the cabin. There are some basic fundamental limitations what you can simulate on your $2000 PC while seating in your office chair. Of course they may be able to reproduce this in the external view but not the actual 'feeling'.

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I think I know what Isaac means, there is that sense in the passenger cabin that the aircraft really drops onto its haunches as soon as those ground spoilers come up. The trouble is such behaviour is - I believe - a product of the amount of travel between the fully extended oleo and the normally compressed oleo positions. If FS doesn't adequately model suspension, that's where the effect would be lost.

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Mark,You hit the nail squarely on the head. FSX does not accurately model oleo strut compression much like the real thing to a degree. The compression model in fsx has only one strength, you can only model the damping ratio but not the effect of the strut appearing to have a 2 stage compression like we see in the videos. Early in my dev days I've tried to do this without any luck and to simulate this in fsx basically means making the damping really soft which means when you turn corners on the taxi way you will lean heavily into the turn which is highly unrealistic IMO.It would be nice if we could model oleo compression realistically but it isn't possible in FS without affecting low speed ground handling in turns.Maybe the next flight simulator will I dunno...Cheers;

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Yes we know FSX has certain limitations. Yet, for this specific item I can not agree more with IsaaC. One of the best airplanes in FSX - the J41, no matter how hard you try to "kiss" the runway, on every land feels like it touches down on its metal rims. Same applies for the MD-11. Being on daily flying job I must say that even the hardest landing has some sort of dampening effect (bouncing if you wish) - that comes from the combined effects of the wings wiplashing on the touchdown, the shock absorbers of the landing gear and the tires itself. Of course the smaller the airplane the less this effect is, but it is always there.Now, back to FSX. I like to try different creations from different developers. I do have my favorites and hands down that is PMDG. However one airplane witch surprised me with its flying characteristic and in particular the touch down is the Captain SIm B707... 110% pure pleasure just to fly that thing around on the circle and make touch and go's.... The way they modeled the touchdown bounce if quite realistic. You can literately feel the landing gear compressing under the weight. So, if CS can do it, PMDG can do it either. And by the way I have mentioned that before.

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Thank you very much for the reply's they have been very helpful in understanding this. I suppose my original intention was to ask if it was possible to perceive this bounce inside the cockpit of larger jets, but it seems rather complicated to allow for this feeling in a home simulator. I classify myself squarely in the amateur Flight Simmer category, before this thread I never heard of an ole strut so... I almost exclusively fly the MD-11 because of how awesome it is and how much learning I have to do in order to get more out of it. Now I understanding that certain addons do give the experience of shake and rumble, but this is purely aesthetic to the camera as far as I understand (EZdock or something of the sort). I recall watching a YouTube video a while back of the Airbus X from Aerosoft exhibiting some type of visual ole strut movement either on take off or during taxi; For the life of me I`m unable to find this video. If anyone has this aircraft and wishes to confirm if what I`m saying is true, I`d much appreciate it. I suppose this effect at the end of the day will purely be visual and not impact at all the cockpit flying experience, I understand that and hope I`m not shaking this tree too much. If I do find the video I`ll update this post.Isaac

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