Stab trim setting calculations

[Emalice]

Hi.

Two things :

1) I still have a problem with the manual way of calculating the stab trim setting : unless the aircraft is nearly empty, my lizfw value is always very low. Minus fuel indexes, i am always out of chart to get the %MAC. Quick example : let's say 50 passengers (all adults) with 35 bags (1015lb ; index 8), total A = 22.8 + 10.2 + 1.1 = 34.1, total B = 36.84 + 7.4 + 8 = 52.24 => LIZFW = - 18.15 (and yes, this is using the forward lavatories instead of aft, or 14 pax max in section A and 12 pax max in section D.

So here the index is already out of range, and that's not even counting the fuel.

Also, total A can never exceed total B (max total A = 34.1, and DOI itself is already larger than that), so why is lizfw = total A minus total B ? Is it a typo ? Should it be total B minus total A, or maybe is it a plus ? Anyway, if someone could figure it out, i'd be grateful.

2) With a recent update there is an excel sheet to calculate performance and stab trim index. There are a few mistakes in this one : for the bags, the weight is calculated in pounds (x * 29) but the table to get the index (Sheet 2) is in kg. Also, it is not performing the calculations of total A and total B correctly. Finally, the take-off fuel index is calculated as the subtraction between the total fuel index and taxi fuel index. But the index and fuel weight values are not linear : 7000lb fuel – 772 (taxi burn up) = 6200 lbs.

The index for 6200 lbs is 6.25, while index for 7000 – index for 772 = 6.3 – 0.9 = 5.4

I've made a corrected spreadsheet which I will upload tonight.

Apart from calculating that index (which is only a minor thing, all considered) I am really having a lot of pleasure flying this beautiful aircraft all across Europe. Thank you for a lot of good work.

E.

[Japo32]

There was some mistakes in the calculation of the example in the Mac% but the way to do it it is right. It is corrected inside the Aerosoft tutorial pdf that I think anyone can download for free.

But as said before the CRJ200 (this one) don't have any plugin to put people in the cabin seats so there is no way to calculate correctly the Mac%. The formulas and example was included to show people how is done in real airliners.

Usually what I do is put a positive trim set and while taking off modify continously the trim to stabilize the plane in a positive climb.. then I press the autopilot. Believe me it is very easy.. and working in all configurations.. BUT of course if you do it right with the Mac% tables.. the value is is going to be better.. and better simulation experience.

If I find a way in future to set the position of pass in the seats I will modify the plane.. but for now I don't find how.

[Emalice]

Hi Javier.

Thank you for answering. I know that %MAC is not necessary for the CRJ in Xplane, and that it is onlythere to show what it is like to be a pilot in real life. But still, they make little sense to me as they are, and that really bugs me I will look at the aerosoft tutorial then.

As for the passengers positioning, I suppose you know Jack's Q400, where he has implemented such a feature. Maybe a collaboration between you and him is in order ? Aaah, imagine two of the best aircrafts in XP marching hand in ha... eer, wing in wing towards brighter skies and better than life models...

Take care, Javier, and thanks again for a wonderful aircraft.

E.

[Kyle Sanders]

I am sorry, but what aerosoft tutorial? where can i get it?

I have been having the SAME issue with the MAC% calculations since day one.

I do understand that the CRJ-200 model in XP does not correspond but if you look at the calculation table just by itself- it does not add up correctly.

I too would like to get it down right

[Japo32]

Go to thecrj200 aerosoft page and download the corrected tutorial manual.It is at thebottom. some numbers are corrected

[Cameron]

Hey, Kyle...it's available here.

[Kyle Sanders]

Thank you VERY MUCH CAMERON!!!!!!

This is great! I'm wondering why i was never aware of this... lol oh well. It is here now

[Cameron]

Thank you VERY MUCH CAMERON!!!!!!

This is great! I'm wondering why i was never aware of this... lol oh well. It is here now

Because it's new.

[Emalice]

I downloaded that manual from aerosoft some time ago, and maybe the numbers are corrected, but the method still looks odd. Also, the example shown in the manual is such atypical (one very seldom flies with three passengers) that it is not really helpful to check if i am doing it right.

Anyway, for me that calculation sheet is still systematically producing numbers that are below the charted range for the index.

Best,

T.