Curiosity about landing gear compression (shock absorbers)

[Fabio Pittol]

Hello,
 
I always see you guys, talking about customizing a lot of standard behaviors of X-Plane, during the Classic's development. One of these days, while watching some real life videos of aircraft landing, one thing came to mind and I decided to chat about it with you.
 
This is not a feature request or anything like that. Just curiosity!
 
What do you guys think about X-Plane's modeling of landing gear suspension? Did you customized it?
 
I'm asking because in real life, we always see, even on harder landings, the aircraft sitting down nicely. Actually, even on smooth landings, it has a nice effect of transferring the weight from aerodynamics to the suspension. But what I see in the sim, whether it's me flying or not, it doesn't happen. Seems like the bump force of the suspension is too high, so if you land smoothly, it almost doesn't compress at all, and if it's not that smooth (specially if you use 'runway follow terrain contours') it tends to do some small bouncing.
 
I even played-back your "crosswind landing" video a few too many times to check it out, but the landing was so good, it didn't help.
 
Here's a video of what I'm talking about:

 

Jump to 1:05 and/or 2:25

[Morten]

What do you guys think about X-Plane's modeling of landing gear suspension? Did you customized it?

 

I'm asking because in real life, we always see, even on harder landings, the aircraft sitting down nicely. Actually, even on smooth landings, it has a nice effect of transferring the weight from aerodynamics to the suspension. But what I see in the sim, whether it's me flying or not, it doesn't happen. Seems like the bump force of the suspension is too high, so if you land smoothly, it almost doesn't compress at all, and if it's not that smooth (specially if you use 'runway follow terrain contours') it tends to do some small bouncing.

 

XP's gear suspension model is pretty good in my opinion. The problem is - or has been -  more that many designers either don't understand how it works or know how to

find the real spring constants. The suspension consists of a spring and a damper, and both need to be right.

Using XP default settings will in most cases give bad results because it is very soft, which will cause all sorts of problems - especially in a crosswind.  So you need to use custom constants.

XP's "wavey" runways as you say are a challenge though and one needs to compromise a bit on the damper to dampen that out.  Having the right CG location is also a factor.

Edited January 20, 2016 by Morten

[Fabio Pittol]

Kinda what I suspected. Thanks for the explanation, Morten!

[Bibou]

Hello, I have a problem, the shock absorbers on the B737 800  V5.01from EADT are not moving...

Do you know how to change it because, the gear suspensions are running well on the V4.

Thanks !

[K4bel123]

I don´t know what might be causing this but you should probably ask in their forum because this one is for the IXEG 737-300.

[Bidartarra]

When seeing those planes landing videos, the comoression seem to happen in 2 stages : the plane touches down, the compression is light, the wing generate enough lift to make the aircraft light on the gears. then the speed brakes deploy the lift is greatly reduced and the gears compress to their on the ground position.

Touch down, speed brakes, plane "sits".

Never saw that modelled in any sim. 

[rcmarple]

I think I caught the effect quite well here -