I have tried to make an electric "trim" device to improve realism in my FS 98 flights. The problem I have seen with the trim in FS 98 or on the CH VPP is that you can't feel the trim force.

I wanted to build a trim that changed the center point instead of the "offset". So, when you take off and pull the yoke towards you, and you find the climb angle you want, normally you would have to slowly push the yoke forward as you trim nose up until the yoke handle is in its centered position. With this modification, when you find the climb angle you want, you use the trim until you don't have any force left in the handle. The yoke handle has a new centering position.

What you need is:

• Of course a CH Products Virtual Pilot Pro (VPP).
• A low voltage (DC) electric motor (quite small) with a built in gearbox.
• A piece of threaded bar (I used M4) but you can use whatever you want.
• A switch with 3 positions. Or two single switches.
• A power source to supply the motor.
• Some other materials.

Disconnect the VPP from your computer.

The first thing you have to do is to disable the centering mechanism in the VPP. Open the cover and remove the upper arm. It is locked with one screw. Remove the spring in the centering mechanism.

Disconnect the cables from the handle rod at the circuit board. Now you can remove the whole handle rod assembly.

You will need to make a few pieces of aluminum. In order to understand how the pieces should fit see figure 1. The measurements are approximate and im millimeters, so you have to make your own measurements to ensure that the parts will fit.

FIGURE 1
(Click for larger image)

Below you can see the parts.

You must make a slit in the handle rod.

(Click for larger image)

When all the parts are made and fit together well it is time to assemble the whole thing. See Figure 1 for how to do that. Then you just connect the motor, switch and power supply in such a way that when you push the switch one way the motor rotates in one direction and vice versa. And of course you have to assemble the VPP again.

(Click for larger image)

Testing

Push the switch to trim nose down (forward), now the motor should start and the yoke handle should slowly move forward. If this works try to push the switch the other way. Then the yoke should move backwards. If these tests are OK you have done a good job.

Start up Flight Sim 98 or whatever sim you use. Place yourself at the beginning of a runway and use the trim to set the handle in the middle position. Check that the FS 98 trim is set to 00. Apply takeoff thrust and raise gear up. Now you are sitting there and holding the yoke towards you, it is time to test the trim in flight. If you are pulling the yoke towards you try to trim nose up; push the switch backwards and hold the yoke in the same position. Now you should feel the force in the yoke disappearing. When you don't have to hold the yoke any longer release the switch.

If you have any questions or ideas about this project, please send me an email.

Bjorn Almgren
bjorn.almgren@mail.bip.net