Horizontal Stabilizer Trim Setting

[luisgordo]

By the way, I just found this in the "Getting to Grips with Weight and Balance" Airbus official documents:

http://img.photobucket.com/albums/v2...ndbsummary.jpg

[pdpo]

Hi Louis,

I found on avsim the FDE by Pedro version 12. This is the one?
If yes, this is made for PSS visual model . Anything needed for integrating this with project airbus? (example : in the LIGHT section, refering to PSS effect files,...)
I see also in the aircraft.cfg that this FDE has 10 load stations. The project airbus has the same load stations as in your load sheet. How to map these two different load stations then?
(the laod stations of the sheet - the load stations in the aircraft.cfg file)

Greetz Peter

[luisgordo]

Hi Peter,

That is one, but as you say it is optimized for the PSS model. The other FDE from Pedro Oliveira is found in the IFDG Airbus models. It is optimized for use with them. However, I do not get good performance when landing with those models (the plane tends to float and climb again instead of flaring). Have you tested with iFDG?

I am using now a simple merge of the FDE with the Project Airbus model (I substitued the Project Airbus file with this one, and changed reference to it in the .CFG file.) It works quite well taking into account the boldness of the solution, but it lacks some power on climbs.

Still looking for the best solution. It looks like we have to stick with Pedro Oliveira's FDE since FS Communicator is optimized for it. The iFDG model would be the best solution, but as I say, landing performance is far from good.

As you say, when you encounter a model that does not stick to the A320 real compartments, it gets tricky to load the aircraft and configure with the LOAD and TRIM sheet. The Project Airbus and the IFDG models are configured in FS quite similar to the real thing.

I am thinking about another option, which would be to use the PSS model (removing the advanced panel, as it will interfere with PM) and test it. This has the inconvenient that you mention about the payload compartments not being modeled as the real ones. Also the visual model is not so appealing as the Project Airbus and iFDG ones (personally I prefer good performance than nice visuals anyway, but also something to consider).

I will keep testing. Let me know about your progress.

[pdpo]

Hi Louis,

this trim setting has kept me thinking and finally I cam up with the following

We can actually get from FSUIPC offset 2FE8 the %CG directly and this is calculated by FS
for whatever model and aircraft.cfg file used.
Then I have looked at your trim sheet and printed the TakeoffCG/TrimPos scale on paper,
measured a little and came up with following calculation (seems rather linear) :
trimsetting = -0.220264 * %CG + 6,268722
I have put this in my SIOC code and show the %CG and the calculated trim setting on my
radio panel when I set a hidden switch in the cockpit in his setup mode. (setup mode means
I can steer the refueling and now also the trim/CG via the radio panel)

The only thing I havent done yet is finding out the ZFWCG to fill in to the MCDU.
I can off course empty the plane of fuel, note the CG that fsuipc gives and then fill up the plane with fuel again....

I'll keep you posted .....

Greetz Peter

[luisgordo]

Hi Peter,

Thanks for your update. I've realized your adjustment of the trimsetting vs. %CG will give a negative value for DOWN, and a positive for UP (according to the scale). I think it is the other way around (at least that is what is shown in the PM lower ECAM). Hence, it would be trimsetting=0.220264 * %CG - 6.268722.
Maybe I am wrong, but we should check this out.

I have used FS Interrogate to check the FSUIPC offset you mention. It seems to give the %CG for the conditions of the plane (payload and fuel loading). However, this value (per my findings) never matches any of the values calculated on the official A320 LOAD and TRIM sheet. Nevertheless, the trim setting obtained seems to give good results (haven't tested much though).

Good idea that of implementing the calculation based on that offset in SIOC. I could do the same thing in pmSystems if this proves to work. By the way, the aircraft can be refueled via the MCDU INIT B page (setting the block value will change the fuel of the aircraft).

I am not quite sure about what PM uses the ZFWCG in the MCDU for (if it is used at all).

What model and flight dynamics do you normally use in your setup?

[pdpo]

Well,

since the load sheet corresponds with the project airbus 320 .. I started using that one...
however, if this sytem seems to prove working fine I might change again to my ifdg model of the A319 since this is the plane for brussels airlines VA and the A330 of posky.

Also I'll check out that latest FDE V12 by pedro of the A320 with the visual model as suggested by PSS (got PSS). I think that this FDE should be closest to reality in matter of fuel use and handling....

Greetz Peter

[luisgordo]

I have tested the use of the latest FDE v12 by Pedro Oliveira with the visual PSS model (got PSS too). It works great with PM and FS Communicator (works better for me than the ifdg models). The PSS IAE version however, does not work nearly as well as the CFM.

Now I have to dig in to the CG aspect of it.

Will report back.

I see you talk about the A330. I have thought about doing this as well, but have never really got to try. Any particular recommendation for the A330 model / FDE ?

[luisgordo]

Hi Peter,

have you gone further into investigating if the CG given by FS gives good results using the Trim formula you stated?

I tried implementing this in pmSystems, but it seems it does not handle Floating point variables, so couldn't automate the calculations...

If this is finally working well, I may program a little code in Visual Basic to get the calculations done by interfacing with FSUIPC. Otherwise, I may wait until I buy some Opencockpit cards (which I probably will in the future) and program it in SIOC code as you have done...