Speedbrakes effect, Landing Gear and Stab Trim settings

[jerico27]

Hello!

I noticed that landing gear don't deflected same way the real aircraft have.
And after some research I found that flap_cl don't change when speedbrakes are deployed.
But I think, from aerodynamic point of view, flap_cl should have massive drop.
As a result speedbrakes are not so effective as real ones.
On many videos that we can see the aircraft rapidly "drops down" on wheels immediately after touchdown and when speedbrakes come up.

I have wrote a script for FlyWithLua which is fix flap_cl and flap_cm depending of speedbrakes angle deployed. I attach this one for illustration.

Also I change damping constants, and deflection a little bit too, this way:


I have loaded three videos if you wish to see the result:

PS1: Also I've noticed that CDU and Ground Service shows stab trim settings for CG 20 and 22 — 3.6 and 3.4 respectively. But based on AFM for B737-300, stab trim settings for 18 — 22 range should be 4.75 — 4.25 respectively.

PS2: I want to be a beta tester!)


But anyway! Great thanks for this beautiful product!

 

Edited August 28, 2016 by Morten

[jerico27]

Also I noticed that Inner cylinder (pistion) on main landing gear have about 1.5 higher deflection under zero load (in flight, when landing gear not loaded).
I.e. the distance that I mark with red arrow on the image below have about 1.5 times more length under zero load then we see in IXEG 737 now.

 

Edited August 28, 2016 by Morten

[Morten]

Hi Jerico,

Thanks for interesting subject.

You are mixing up speedbrakes and ground spoilers.  We have extensive data on the speedbrakes and spent dozens of hours on testing and finetuning it.  So you can rest assured that the speedbrakes are correct.  You are not supposed to use speedbrakes with flaps, so flap Cl is not there an issue, only wing Cl.  As for the GROUND SPOILERS which is what you are talking about thats another story, we have used XP's default model those. Don't remember exactly how XP models those.  We might look into that if we find some good documentation on it - thanks for sharing.

As for the trim units at different CG's, that also depends on flap setting, but we'll check the numbers again, easy fix.

M

 

[jerico27]

6 hours ago, Morten said:

Hi Jerico,

Thanks for interesting subject.

You are mixing up speedbrakes and ground spoilers.  We have extensive data on the speedbrakes and spent dozens of hours on testing and finetuning it.  So you can rest assured that the speedbrakes are correct.  You are not supposed to use speedbrakes with flaps, so flap Cl is not there an issue, only wing Cl.  As for the GROUND SPOILERS which is what you are talking about thats another story, we have used XP's default model those. Don't remember exactly how XP models those.  We might look into that if we find some good documentation on it - thanks for sharing.

As for the trim units at different CG's, that also depends on flap setting, but we'll check the numbers again, easy fix.

M

 

Yes, I wrote "speedbakes" because in Plane Maker we only have "speedbakes" but we know, It's about GROUND SPOILERS too)
But, however, I think in this case, when we use speedbakes (speedbakes I mean flight and ground spoilers) (and especially ground spoilers), flaps Cl (and I think their Cm) should change too, because spoilers located right before flaps and when spoilers deployed we should have got airflow separation from the flaps and as result Cl and Cm of the flaps should be minimized too and as result overall Cl and Cm of the wing drops too.
In anyway with logic that I described (and with my script) all comes to work just fine.

Edited August 28, 2016 by jerico27

[Morten]

8 hours ago, jerico27 said:

Yes, I wrote "speedbakes" because in Plane Maker we only have "speedbakes" but we know, It's about GROUND SPOILERS too)
But, however, I think in this case, when we use speedbakes (speedbakes I mean flight and ground spoilers) (and especially ground spoilers), flaps Cl (and I think their Cm) should change too, because spoilers located right before flaps and when spoilers deployed we should have got airflow separation from the flaps and as result Cl and Cm of the flaps should be minimized too and as result overall Cl and Cm of the wing drops too.
In anyway with logic that I described (and with my script) all comes to work just fine.

Cl will reduce obviously, both wing and flap, so you get more weight on wheels for the brakes to work better.  Cm will not change very much.  What also happens on deployment of groundspoilers is that the total CENTER of lift is moved FORWARD on the wing.  This again results in a pitch UP tendency right after deployment.  This is why on many airliners there is a timedelay on the outboard groundspoilers deployment (usually 1-1,5s).

[Morten]

About the gear, it is very unclear what you mean and what your reference is.

We are offcourse open to debate flightmodel related stuff, BUT "undocumented claims" and "I think" type of engineering is not how this aircraft is build.

M

Edited August 28, 2016 by Morten

[jerico27]

About landing gear ander zero load...

Real:

In real 733 D1 maybe just a little bit less then D4/2, just a little bit.

 

Lovely IXEG:

It's maybe not so important, but I just noticed.

[K4bel123]

19 hours ago, jerico27 said:

On many videos that we can see the aircraft rapidly "drops down" on wheels immediately after touchdown and when speedbrakes come up.

 

I don´t know too much about all the other things you guys were writing about, but what I did notice is that the real 733 ´ rapidly "drops down" on wheels immediately after touchdown and when speedbrakes come up´ exactly like you wrote. The fix you provided for the IXEG 733 looks very promising and I´m certainly going to have a look at it. But since I´m not a big fan of fixes, I really hope that you, IXEG, look at this too and find a way to put this in a future update for the 733. It already is imho the single best aircraft ever developed for any flight sim, especially concerning the flight and ground dynamics, and therefore this would truly take the 733 even one step further ahead!

Keep up the great work!

EDIT: to apply this fix for now, do I only need to change these constants in plane maker and load the lua fix into my lua scripts folder?

Edited August 28, 2016 by Morten

[jerico27]

12 minutes ago, K4bel123 said:

EDIT: to apply this fix for now, do I only need to change these constants in plane maker and load the lua fix into my lua scripts folder?

Exactly!

[Morten]

Jerico, you obviously do not know what you are doing here.  

1. You have changed the gear SPRING CONSTANTS  and DAMPER CONSTANTS, which we know are spot on!  By doing what you do you are altering aircraft performance on takeoff, crosswind and ground handling in a negative way. We do not want you to encourage people to do this!

2. Your gear comparison photo is very inaccurate to put it mildly

So for these reasons I am deleting your "fix".  Any flightmodel changes need to go through us - which means you need to document everything PROPERLY and submit it to us and we'll take a serious look at it.  XP's ground spoiler model is most likely not perfect, but a "hack" like this is not the way to fix it. 

Topic closed

 

 

Edited August 28, 2016 by Morten