With the release of update 1.09 users can configure their game to make helicopter collective work with Hands On Throttle-And-Stick input devices. By default the game doesn't know you intend to use a HOTAS controller. - As such we must go into our config files and add a few new lines to enable this feature.

Before beginning I recommend making a backup of ROInput and ROGame in case you wish to undo the changes. Files found here:
Documents\My Games\Rising Storm 2\ROGame\Config

1. Navigate to Documents\My Games\Rising Storm 2\ROGame\Config and open ROGame.ini with a text editor such as NotePad.

2. Find the section labelled [ROPlayerController] and enter the following underneath it:
bAbsoluteCollective=true

Save and close the file.

3. In the same Config folder open ROInput.ini. Locate [ROGame.ROPlayerInput] section and paste the following into that section:
Bindings=(Name="XboxTypeS_LeftY",Command="Axis aHeloCollective",Control=False,Shift=False,Alt=False,bIgnoreCtrl=False,bIgnoreShift=False,bIgnoreAlt=False)

Save and close the file.

This bind is set up to use XInput left control stick to control the collective. To change to right stick you'll need change XboxTypeS_LeftY to Right.

4. Now you will need to go to your HOTAS software to set the throttle axis to emulate a gamepad axis. Assuming you followed step 3, I recommend the left stick, unless you changed it to right for whatever reason.

If you have problems with the collective flickering around the 0 mark, modify the command to be Command="Axis aHeloCollective DeadZone=0.1" or similar to settle it down.

Note that collective does have travel time, meaning if you were to jam the throttle up and down rapidly it won't keep up perfectly. That being said, it does travel much faster than traditional input from a keyboard.