Electric Elevator Trim Installation
 

Hi,

I am considering adding electric elevator trim to my RV9A. I currently have manual trim but would like electric so that the autopilot can automaticlly make trim adjustments. From what I'm gathering on the Van's website, you either have manual or electric, Not both.

Is there any way to add the electic trim without removing the manual?

How difficult is it to add the electric trim to a completed aircraft?


Thanks,
Mark Klepper
N1075 RV-9A

Am I misunderstanding?
 

Mark,

The autopilot servo would connect to the elevator push tube. I have the electric elevator trim on my plane. You would have to remove the cable from the trim in order to install the trim servo in its place. Then you would need to run the five wires from the trim servo to the front of the plane to your switch, power and ground. The trim servo is the one Ray Allen sells.

I already have a Pitch Servo in the tail for a Trio AutoPilot. The pitch servo has an output that will directly control an electric trim.

Just hoping I could leave the manual trim in place. (And working) It looks like you have to choose either Fully manual trim, OR electric trim only. Is that correct???

One option, used by some early -6 builders, is to buy a shorter push-pull cable and mount the Ray Allen trim servo on the flat deck under the fiberglass tail fairing.

This way there is no modification to the metal work of the horizontal tail.

Are there any drawings for the installation of electric trim on a RV-9 ?

I've been flying electric elevator trim for the past 5 yrs and I like it except that it needs to be slowed slightly for cruise adjustments. I decided to use the Ray Allen speed reduction module, purchased but not installed yet. I may install it at the rear deck adjacent to my trim servo connector.

This is what I did when I converted from manual trim to electric trim. It works great. The push-pull cable needs to be about 28 to 30 inches in length for this to work optimally. All cable parts can be purchased through Aircraft Spruce.

I highly recommend using Pat Hatches “Ultimate Trim Relay Board (UTRB)” and mounting it under the copilot’s seat. The use of a trim relay board prevents both pilot positions from inputting trim control inputs at the same time thus either cancelling each other or worse burning up the trim control motor(s).

At the time I converted my aileron and elevator trim from manual to electric I also installed five button Tosten military style grips. (Tosten is another great vendor who will help you think through the grip/button issues.) The UTRB board really helped in the wiring up of the additional switches. My grips now have buttons for PTT, ident, flaps/com swap - depending whether it’s the pilot or copilot stick, freq swap and autopilot engage/disengage. This makes flying real easy and I can pretend its a military jet trainer ie T37 or T38. (I loved flying the T38 when I was a youngster.)

Its sounds like a major wiring job but it actually wasn’t too bad with Pat Hatch’s assistance. He guided me through the process via emails and a few phone calls. He lives in Florida and I live in Oklahoma and my electrical knowledge is minimal. (Accountant by education - good with money/dumb with sparks!) However, Pat still successfully guided me through this process pretty easily. The actual work took two plus long weeks of almost daily effort but I absolutely love the results. By the way, I don’t use a speed control switch on my elevator trim. Didn’t need it.

PS: Document via schematics, pictures and written notes this change. You may need to modify or repair something later on. I also highly recommend getting a small heat printer at Office Depot or some place else plus shrink tubing and label all wiring you install or hook up. Steinair has some great UTube videos on how to do aircraft wiring and will also sell you the tools, wire and connectors you’ll need.

Don’t be intimidated by the project. It’s a very doable and well worth the effort.

Update: share before and after photos..

The trim tab horn on the elevator only has a single connection to the trim manual cable (or Ray Allen actuator for electronic trim). The geometry is different depending on electronic or manual. Take a look at drawing 4 in the plans. You might need to build a new trim tab if the trim tab horn E-918/E-917 has been trimmed as the plans require. The electronic trim kit from Van's has all of the other pieces you need.

Wiring it all up is easy. The electronic trim wires basically can follow the path that was used by the manual cable when you remove it. There are 5 wires to the actuator and you can buy an appropriate length of multi-wire cable (WC3) with all of the correct color codings to match the Ray Allen wires. Two of the wires are +/- voltage to move the motor up/down, and the other 3 are ground, a reference voltage and a return sensor voltage to drive the display for trim position indication.

Vans Electric Aileron Trim Option
 

I don't know if you saw this, but there is a kit that attaches to the access plate that looks really simple. This is right out of Vans product description. I happen to run across it while I was reviewing SB's and notices for my DAR inspection this fall. I had not seen it before, maybe I'm the only one since it's apparently been there since 9/29/2018. :o

Since it can be retrofitted I'm thinking of holding off until I see if it's necessary. I've never flown with aileron trim in 30 years so I'm not sure I'll miss not having it. ;)

Electric Aileron Trim Kit
Add Electric Aileron Trim to Your RV

Description
EA-8 KIT & EA-7/9 KIT
The RV-7/7A,8/8A,9/9A, use a spring bias style of electric aileron trim. The servo is mounted below the seating areas of the airframe. The system applies trim forces directly to the control column and can be retrofit or installed during fuselage manufacture. No external tabs are required.
Current builder/pilots of the RV-4 and 6/6A can adapt these spring bias systems for the 8/8A and 7/9A respectively. We no longer have kits for the older trim kits which utilized a hinged tab on the aileron trailing edge.

EA-10 KIT
For the RV-10 and RV-14/14A. A spring bias system as above, but the servo mounts in the wing, and is attached to the aileron pushrod. Can be retrofitted to flying airplanes.