How To Add An Elevator Trim Wheel To Your CH Products Yoke

By Steve Sokolowski (8 February 2007)

If you've been reading my articles found here in FlightSim.Com, you might have noticed that I'm a stickler for realism. Realism in the flight Simulator software I use and the hardware I connect to it. So deciding which flight yoke to add to my cockpit was a no-brainer. CH Products! The FSY21U (Fig. 1) was my first and only choice. Beautifully built, easy of calibration and a thrill to use. BUT! CH Products did miss the point by using three small lever controls in their design (Fig 2). I programmed these levers to control engine RPM (throttle), fuel mix and finally elevator trim control. While this scheme did work for a while but it did become a "drag" after a while. So in-stepped Desktop Aviator. They designed a throttle quadrant with Cessna style push-pull levers, a parking brake and an elevator trim wheel (Fig 3). The elevator wheel has a 7.5 inch diameter plastic wheel mounted to a 100K ohm potentiometer (Model #1065). When I saw this, my own wheels began to turn. What if I can easily modify a CH Flight Yoke to accept Desktop Aviator's Trim Wheel? Well, I tried it, and the end result was fantastic!

Fig. 1
Fig. 2
Fig. 3

In the next few paragraphs, I will show you how you can just plug the trim wheel into the yoke to easily and effortlessly control the pitch attitude of your aircraft by just turning the 7 inch plastic wheel. Rotate the trim wheel down for nose up and rotating the wheel up for nose down attitude. What could be easier?

Don't want to use the trim wheel anymore tonight? Just unplug it; the CH Yoke's levers will automatically be connected for normal operation. So now is a good place for the disclaimer. I do not accept any responsibility for the mis-wiring or any damage any mis-wire might cause. Or any damage or voided warranty made to your CH Products Flight Yoke. But if you follow these instructions and have some knowledge of soldering techniques and electronics, there should be no problem.

Opening The Flight Yoke

Let's first start by turning your Flight Yoke over and take note of the warranty sticker (Fig 4). "Warranty VOID is Seal is Broken". Strong words from the manufacturer. If your yoke is new, I do not recommend breaking the seal. But if the yoke is older then the manufacturer's warranty (see the instruction manual that came with your purchase to determine the length of the warranty), break the seal! And begin to remove the eight Phillips screws located around the perimeter of the base (note: there are six screws that can be easily located. There is another two screws being covered by the rubber feet located in the corners of the base; with a screwdriver, pry the feet up to expose the two screws). With the screws removed, the base easily comes apart (Fig 5). But be careful. A number of wires (the wire harness) connecting the three levers to the USB adapter are also present.

Fig. 4
Fig. 5

In Fig 6, notice the small circuit board in the upper right hand corner of the lower base shell. This is the USB adapter. It contains the programmed HID (Human Interface Device) chip and associated circuitry. You can easily remove this circuit board just by lifting it from its plastic mounting rails. Fig 7 shows what the USB adapter looks like. It is here that we will do a few minor wiring changes. But what type of changes? I'll show you.

Fig. 6
Fig. 7

Retrofit Wiring Changes

Fig 8 shows the small circuit board where the three yoke levers are soldered. To make things simpler, we'll modify the lever located closest to the outside of the yoke (I programmed the same lever as a trim wheel). The three levers are made up of 100k ohm potentiometers wired in parallel. The wiper arms (the terminal located in the center of the three soldering points on the "pot") are brought to three different points of the USB adapter by the wire harness. So what if we parallel solder the same three terminals of the Desktop Aviator's Trim Wheel to these points? We will have a realistic elevator trim wheel.

Fig. 8
Fig. 9

What We Plan To Do

Fig 9 shows a schematic on what we plan to do with this modification. Through the stereo jack, we will connect the Desktop Aviator's Trim Wheel to the BLUE and GREEN wires inside the wire harness (in parallel). The ORANGE wire, also from the wire harness, will be cut and the stereo jack will be connected in series with this wire. That's all there is to it. Desktop Aviator will provide the stereo jack pre-wired using these colors. All you need to do is to follow the color-code as per the schematic.

As seen in Fig 10, locate the BLUE and GREEN wires inside the wire harness closest to the USB Adapter. Carefully strip back the insulation to expose the bare wire (see Fig 11).

Fig. 10
Fig. 11

Take the ORANGE/BLACK wire from the stereo jack and splice it with the BLUE wire from the USB adapter. Then solder. Next, take the BLACK wire from stereo jack and splice the GREEN wire from the USB

Fig. 12
adapter (see Fig 12). Then, using electrical tape, cover the exposed wires, making sure that they are not "Shorted".

Finally, locate the ORANGE wire inside the wire harness and cut it about 2 inches from the USB adapters' Molex Connector. Take the ORANGE wire closest to the Molex connector, splice the BLUE wire (from jack). Take the other side of the ORANGE wire and splice it to the YELLOW wire from the stereo Jack. Solder both connections and cover with electrical tape. The retrofit is now complete.

Mounting The Stereo Jack

The stereo jack supplied with the retrofit kit is a relatively small part. The thickness of the plastic base of the Flight Yoke will not allow the jack to be mounted unless modified slightly.

Locate an area on the bottom base section of the yoke where the mounting of the jack will not interfere with the movements on the mechanism. A good location is illustrated in fig 13. With the area located, place masking tape to protect the yoke's finish and drill a 1/8 inch pilot hole (fig 14). With the pilot hole drilled, change your drill bit to a .237 inch (1/4 inch will also work) and drill the second hole inside the first.

Fig. 13
Fig. 14

Now the tricky part. Take a 3/8 inch drill bit. And BY HAND, rotate the bit inside the 1/4 inch hole just drilled. Fig 15 illustrates this. Twist the drill bit until enough plastic is removed so that the

Fig. 15
mounting nut from the stereo jack can easily fit inside. When enlarged to the proper diameter, carefully insert the jack into the hole and screw it to the base using the supplied nut. Do not over tighten. Re-assembly the Flight Yoke.

Calibrating The Elevator Flight Yoke

If your CH Flight Yoke was calibrated correctly prior to adding the trim wheel, no other calibration is required. The trim wheel and the lever on the yoke are both 100K ohm potentiometers, so no additional calibrating is needed.

Using The Trim Wheel

With your Flight Simulator software running, select your favorite aircraft. Plug in the trim wheel into the stereo jack and rotate it up and down. You will note significant nose up and down attitude.

Use your trim wheel to adjust for level flight at cruising altitude. If you find that rotating the trim wheel UP, the nose of your aircraft goes DOWN, just go into you FS's Assignment Window and click on REVERSE operation for the elevator trim. If you wish to revert back to your normal Flight Yoke levers, just remove the trim wheel from the stereo jack. The yoke's internal lever will automatically be reconnected.

Mounting The Trim Wheel

In the real world, elevator trim wheels are often located just beneath the throttle quadrant and to the right of the flight yoke. Your new trim wheel can be mounted to your flight deck using aluminum "L" brackets. Or better yet, a strip of Velcro, if you wish the wheel to be removed easily.

If you have any comments or just wish to say "Hi", you can email me.

Steve Sokolowski
steve34613@Yahoo.com

[ Back | Home | Main Menu | Logout | Help ]