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How to interface CRJ550/700 L-Vars with AxisAndOhs


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  • Aerosoft

How to interface CRJ550/700 L-Vars with AxisAndOhs ?


Due to its complexity and Flight Simulator internal mechanism, some functions, buttons, knobs, etc.
are not assignable directly in Flight Simulator.
However, most of them are with the L-Vars.
The L-Vars are the Local Variables used in the core of the addon programming.


To get access to these variables, several third-party utilities are available.

Among them are Spad.Next and AxisAndOhs.



Utilities like AxisAndOhs or Spad.Next are the bridge between complex aircraft and complex hardware.


This tutorial will describe the basic of interfacing with AxisAndOhs.
It will also show how to enhance the default functions handling of Flight Simulator.
For instance by detecting when a button is pressed or released and acting accordingly.
à Basically allowing the use of ON/OFF switches for instance.


This is NOT a user’s manual for AxisAndOhs.
It shows the basics for you to build your own setup.
Browse the forum, there are several users already offering their own AxisAndOhs setups to download.


Part 1 :

We set the CRJ parking brake and the gear switches on the Thrustmaster TCA Throttle Quadrant.
We will not use the L-vars for these, but the ability of AxisAndOhs to use the ON/OFF switches properly wich isn’t the case in FlightSimulator.

Part 2 :
We will then assign a rocker switch of the TCA to the Autopilot Disconnect function.

This time with the L-Vars.


Let’s go !


First, you need to download and install AxisAndOhs.
Check this site : https://axisandohs.weebly.com/

We won’t cover the installation process as it is quite simple and explained on their website.

Once installed, a icon will be added to your desktop :

STEP 1 :
Start Flight Simulator and load a flight with the CRJ.
In this case, the CRJ 550 is loaded.

STEP 2 :
Start AxisAndOhs
It will automatically detect the aircraft loaded.

Nothing is assigned yet, so the two panes are empty.


STEP 3 :
Click on the “+” under the “Assigned Buttons” pane :


A dialog box appears :

1 – Select the TCA in the Device dropdown.
2 – Rotate the Park Brake handle so that it is detected.



Click the arrow in the Key Down Event field.
A drop down appears with a list of functions categories.

à Click “Aircraft Miscellaneous Systems”


STEP 6 :

The category expands.
Double click on “PARKING_BRAKES: Toggle parking brake on/off”


The list closes and the function is now assigned to the Key Down Event.

Repeat the exact same procedure for the Key Up Event.
à Click “Add”

The function now appears in the Assigned Buttons list.

STEP 10 :
Click on the “+” under the “Assigned Buttons” pane :


and repeat the steps 4 to 9 with the TCA gear rocker switch and the
GEAR_UP (Sets Gear handle in UP position) & GEAR_DOWN (Sets Gear handle in DOWN position)
Click “Save”


Both assignments now appears in the Assigned Buttons pane :



Not really actually, but somewhat different.

We will use the L-Var driving the Auto Pilot Disconnect switch
As the names says, L-Vars are variables, not functions.

It is therefore not possible to assign a button directly to a variable.
We must create a function that will set this variable to a certain value, THEN ONLY assign a button to this function.
In AxisAndOhs, this happens in the Scripts

1 – Click “Scripting” in the upper menu bar
2 – Click Read LVARs from sim. (This will load all the available L-Vars of the aircraft and make them available from within the scripts)


STEP 2 :
The Script editing dialog box opens.
1 – Click “+” to add a new group of scripts.

àThe Scripts Groups box pops up
2 – Choose and enter your group name.
3 – Click “Add”
4 – Click “Close”


1 – Your group name now appears in the scripts group list
2 – Select the script group you want to attach your script to
3 – Choose and enter the script title. We create a first function to disconnect the

4 – Click “Insert sim var”


A drop down appears with a list of functions and variables categories.

à Click “Local Simulator variables” à THESE ARE THE L-VARS

STEP 5 :
The category expands.

Double click on “L:ASCRJ_FCP_AP_DISC, Number | Settable: Y”



It now appears in the script editor.



STEP 7 :
We will set this variable to “1”, meaning “ON”.
Meaning that this script sets the “L:ASCRJ_FCP_AP_DISC” variable to 1 or ON
so disconnecting the autopilot.
1 - To do so, add “1” and a SPACE before the first parenthesis.
2 – IMPORTANT : after the first parenthesis, add a ”>”. This is for scripting syntax reasons.
3 – Click “Save as New”



We now have to create another function to connect the autopilot.
Basically the same as the disconnect one, except that the ASRJ_FCP_AP_DISC variable will be set to 0 or OFF.
To do so, repeat step 7 by creating another function named AP-Conn for instance and
adding a “0” and a SPACE before the first parenthesis.

à Both your own AP-Conn and AP-Disc scripts now appear under you own scripts category.

Press “Close”


STEP 9 :

Click on the “+” under the “Assigned Buttons” pane :

For the test purposes, we will use one of the engine starter rocker switches of the TCA

To demonstrate the uses of our two new scripts.
Do the previously described button assignment procedure.
This time, your own script category will appear in the available functions in the list :


STEP 10 :
Assign both AP-Conn and AP-Disc functions to the Key Down Event and Key UP Event.

Click “Save”

STEP 11:

You are done !

All your three assignments appear.

And they work… !


Simply close AxisAndOhs program.
Everything is automatically saved.
Next time you load a flight with the CRJ 550, the assignments and scripts will be loaded and active. 



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  • 6 months later...
  • Aerosoft
3 hours ago, Agrajag27 said:

Thank you a TON for this. I got a nice assist from @FltsimFlyboy and then found this thread. Within minutes I had the Battery Master set the the "MASTER BAT" switch on my Alpha. Now time to go tackle several more!

Hi Agrajag27,

Thank you 😊

Here are two other ones that maybe can help you :



Best regards.

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43 minutes ago, SimWare said:

Here are two other ones that maybe can help you :


I'll be digging into both of these once I figure out how SU6 has caused me to CTD on my normal test flights while learning the CRJ.


On the funny side I need to also figure out why SU6 is now making the flight attendant tell me the passengers are aboard several times.


I also need to figure out why my third test of adding L-VARs failed. I found the thread on the correct L-VARs for the doors and thought it would be simple to set a throttle button to open and close the MAIN cabin door. I knew I was in trouble when AAO's TEST button failed to do anything.

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