WebMaximus

Realistic and neutral stab trim value on the ground

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What would a realistic and neutral stab trim value be when on the ground with the engines running and the HYD pumps on?

Reason for my question is I'm trying to set up a Brunner CLS-E yoke where I can choose between software or hardware trim in the CLS2Sim software that comes with the yoke.

If I use the software setting I need to have the stab trim in the NGX set to about 4 units to get a neutral pitch looking in the CL22Sim software (as well as the actual position of the physical yoke along the pitch axis). I find this a bit strange since the stab trim scale is 0-17 so to me it would make more sense a neutral position would be somewhere around 8.5 units but I guess I'm missing something here?

If I use the hardware trim setting there's no connection between me pressing the trim button on the yoke and the stab trim value in the NGX. I do however feel in the yoke how the force is shifting in a very realistic way. But using this hardware trim setting also causes a weird thing, the yoke "drops" to the right or left if I let go of it. Not sure what that is all about because surely that doesn't happen in the real aircraft and most certainly not when the a/c is all lit with the engines running and the HYD pumps on or does it?

I realize I'm repeating myself a bit here from another post earlier tonight so sorry to those who already read about this. Just feeling a bit frustrated when I'm not sure how to tune everything. The yoke in itself is nothing short of amazing compared to my old plastic CH yoke but all the different settings and parameters in combination with very few people to exchange ideas and questions with makes it a bit difficult.

Oh yeah, forgot to ask about one thing. When using the software setting in CLS2Sim I'm able to trim up but not down. I have the buttons (HOME and END) mapped to the trim buttons on my Brunner yoke via FSUIPC. I have also tried pressing the keys directly on the keyboard but same problem...I'm not able to trim nose down but only nose up. Using the mouse though pointing the cursor at the stab trim wheel in the v/c and using the mouse wheel I'm able to trim in any direction without any issues. I found some other guy asking the very same question back in 2015 still without a single reply so here's me keeping my fingers crossed I'll find myself in more luck ;)

Let me lastly add I'm running P3Dv3.2.3 using FSUIPC for all button and axes assignments with the exception of the yoke axes (pitch and roll) since that is handled directly via the Brunner CLS2Sim software talking directly to the NGX the way I understand it. I don't even see the Brunner yoke as a device in either P3D or FSUIPC. The only reason I can map things to the buttons on the Brunner yoke is I'm using a free tool recommended by Brunner called vJoy that will allow the buttons on the Brunner yoke to be seen by other software such as FSUIPC.

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Strictly speaking in an aircraft with a Trimmable Horizontal Stabiliser (THS) like the B737, the position of the stabiliser should not affect the yoke "neutral point".

The yoke controls elevator deflection, the trim controls stabiliser position. When the aircraft is in trim, the elevators are faired with the stabiliser: i.e. they are in the neutral position, therefore the control column will be centred, whether "in trim" means lots of nose up (not familiar with the 737, so I'll pluck a value from your range out of the air -- let's say 14 units) at low airspeed or lots of nose down (let's say 2 units) at high airspeed: in either case the elevators will be neutral and the control column will be centred.

This is subtly different to an aircraft equipped with elevator trim tabs, where you move the trim tabs in order to aerodynamically hold the elevator in whatever position you have placed it with the stick and thus the stick "neutral point" will physically move.

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Thanks Simon and  this makes me think something is not fully correct either with the NGX, how the Brunner yoke works or a combination of both. This since the yoke indeed does physically move (as well as visually in the v/c) when you use the trim. Trim down and the yoke will move forward and vice versa.

I just completed a flight and for the first time I was using the hardware trim option in the Brunner CLS2Sim software. Having it set to hardware trim SYS page showed the pitch axis perfectly centered and at the same time the physical yoke was in it's centered/neutral position. All good in other words.

The problem though as mentioned above is that whenever I have hardware trim as well as hydraulics enabled in CLS2Sim the yoke continuously want to "drop" to the left/right on the roll axis whenever I let go of it. Noticed this behavior stopped once I switched the ELEC HYD pumps off at my destination. Really odd and guess I need to ask the guys over at Brunner about this. Probably just me doing something stupid with all the different settings in their software.

This is what the SYS page looks like when not using hardware trim in CLS2Sim and after setting the correct stab trim for t/o.

rJ8rsqs.jpg

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15 hours ago, WebMaximus said:

This since the yoke indeed does physically move (as well as visually in the v/c) when you use the trim.

This caught my attention because it countered what I believed to be true, so I launched P3Dv3 with the NGX in the default start configuration (engines running at end of runway).  Made sure the yokes were not in the stowaway position and moved the trim full nose up and nose down and the yoke does not move.  It shouldn't be moving with trim as Simon explained. I'm not sure what you did to your configuration to make that happen.  Also, I am not sure I follow you when you say the pitch axis is centered and the physical yoke is centered.... this is not what trim is about.  A "zero" trim does not correlate to a pitch axis.  I highly recommend you avoid the use of a product that introduces such behavior, or find a way to disable it.

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Sorry for the confusion and honestly I'm not even sure myself anymore exactly what steps got me where I was when writing the posts above. Anyway the remedy was to start all over again with a clean default profile in CLS2Sim and this time I decided to skip hardware trim and instead use software trim and this time it seems to work really good.

I have no longer the issue where the yoke drops to the right and left when I let go of it. Also the yoke doesn't move anymore when I trim which of course is the correct behavior since the elevator controlled by the yoke doesn't have anything to do with the stabilizer controlled by the trim.

Lastly the reason I couldn't trim down but only up yesterday was because I had missed trim down was still assigned to a button on the yoke in P3D and since I do all my assignments in FSUIPC that screwed things up. After removing the assignments in P3D trim down now works just as good as trim up.

So...right now I hope and think everything is actually working really good.

Let me also finish off by saying the yoke I'm using (Brunner CLS-E) is a truly amazing piece of hardware. For anyone looking for the feeling of actually holding a real yoke in a real and live aircraft in your hands I honestly don't think you could find a better option. For the problems I've been having up until now I'm sure they have all been caused by me not knowing exactly what I'm doing tweaking all kind of settings and parameter in the CLS2Sim software which in itself is really impressive looking at all the options you have to tweak thing to suit your specific needs depending on what aircraft you're currently flying.

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It is a confusing subject. When the plane is trimming itself in cruise with the autopilot on, the yoke does move against the trim. So, if the plane senses it's out of trim and needs to apply nose down trim, the wheel will roll forward and the yoke will move aft.

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Good grief 1900 EUR and uses 400 W..., does it make coffee?

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2 minutes ago, downscc said:

Good grief 1900 EUR and uses 400 W..., does it make coffee?

I'm sure it will if I only could find the setting for how strong to make the coffee ;)

It's a lot of money no doubt but after flying for about 15-20 years with a plastic "toy" I felt it was time to treat myself with some real gear. The combination of this yoke and a pair of Oculus Rift glasses is nothing short of amazing!

Here's a couple of nice reviews of the yoke and obviously there's more of them out there for anyone interested.

 

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One might consider taking 2000 EUR down to the local flight school for some actual flying too.

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Plus that will barely get you 10 hours. Am considering the Brunner myself.

Chris

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Waking this thread up again to ask a follow-up question on the elevator/stabilizer in the NGX.

Yesterday I noticed in spot view looking at the external model of the NGX that when adjusting the stab trim the elevator was moving. As has been described in this thread I thought the stab trim would only affect the stabilizer and not the elevator.

Or am I still missing something how all this works on a 737 NG?

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