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Another bad RAC Relay....

Ironflight

VAF Moderator / Line Boy
Mentor
Well, the good news is that once I change out the pitch trim relay in Louise's RV-6, I should never have to deal with the older "dash 1" RAC trim relays ago - I'll have everything up to "dash 2" (the larger, newer) relays in both airplanes.

For those not familiar, the earlier relays have a tendency to start getting sticky, and fail so that you get no function in one direction. Generally, if you blip them the other way, you can then get it to work the way you want. My past experience has been that you have some time to change it before it quits completely, but this time, Louise had one problem a couple weeks ago, and this morning, it was pretty much dead - made for an interesting morning commute...

My advice for anyone that has the "dash 1' relays and still has access to them if you're building - change them now....unless you like having stuck trim in flight...

Paul
 
I had the same problem in my -4...

I flew with one "intermittent" relay for a while before switching out both for the newer (and larger) version. Both have worked reliably so far...

Dean Pichon
RV-4
 
Rac Relays

My original ones were mark 1, after about 150 hours or so, they started sticking at the end of each flight (heat I guess). I had been making it a point to "tap tap tap" them so they were dead centered after each flight. Probably contributed to the problem. They _always_ worked in flight, just stuck on the ground. (Vibration).

With the engine off, I could hear them clicking, but no motion of the trim motors.

Fortunately, they were mounted just under the pilot seat pan, so a couple of forceful taps with the butt of a screwdriver usually freed them up. I quit doing the "tap tap tap" at the end of each flight and they quit sticking for a long time.

I did switch them out for the large ones during the rebuild. 125 hours so far and no problems.
 
If you are saying RAC is ray allen. Their relays are junk. AFter changing two on my kitfox, I went to these units very nice, never another problem. Oh and the ray allen relays would poop out at 300hrs. Go half way down the page. I put these on my flaps and the elevator trim in the RV.
http://www.aircraftextras.com/Index.htm
 
Well, the good news is that once I change out the pitch trim relay in Louise's RV-6, I should never have to deal with the older "dash 1" RAC trim relays ago - I'll have everything up to "dash 2" (the larger, newer) relays in both airplanes.

For those not familiar, the earlier relays have a tendency to start getting sticky, and fail so that you get no function in one direction. Generally, if you blip them the other way, you can then get it to work the way you want. My past experience has been that you have some time to change it before it quits completely, but this time, Louise had one problem a couple weeks ago, and this morning, it was pretty much dead - made for an interesting morning commute...

My advice for anyone that has the "dash 1' relays and still has access to them if you're building - change them now....unless you like having stuck trim in flight...

Paul

Paul,

I unearthed the above post while doing a search to find a fix for my sticking elevator trim. Is the REL-2 Servo Relay Deck still the best replacement for the older Ray Allen Rel-1 Relay?
 
Paul,

I unearthed the above post while doing a search to find a fix for my sticking elevator trim. Is the REL-2 Servo Relay Deck still the best replacement for the older Ray Allen Rel-1 Relay?

Well, they'e still working fine for me ! (I hesitate to use the term "best" when I haven't tried a variety of things, but from what I hear, the REL-2 is far superior to the REL-1, and I have had good luck with it).

Paul
 
Or better yet install a Safety Trim controller from TCW Technologies and get rid of RAC relays altogether. I installed this device primarily because it prevents runaway trim. And, if you install the airspeed switch, you can get 2 trim speeds - faster for slower airspeeds, and slower for faster air speeds. I have one in my -8 and like it a lot. Plus Bob Newman (TCW Tech owner) is just absolutely super to work with.

http://www.tcwtech.com/Safety-Trim-Page.htm
 
Or better yet install a Safety Trim controller from TCW Technologies and get rid of RAC relays altogether. I installed this device primarily because it prevents runaway trim. And, if you install the airspeed switch, you can get 2 trim speeds - faster for slower airspeeds, and slower for faster air speeds. I have one in my -8 and like it a lot. Plus Bob Newman (TCW Tech owner) is just absolutely super to work with.

http://www.tcwtech.com/Safety-Trim-Page.htm

I'm curious, has anyone actually experienced a runaway trim condition with a RAC system?

The Safety Trim system does look nice (I too have had to replace a RAC relay)
 
Ray Allen

Just a heads up and and shout out for the people at Ray Allen Co. I bought some of their products throuh vans for my -8. I had a few questions several times resulting in calling them. They answered all of my questions, gave me all the time i needed and then some. It was no surprise to find that they are a family owned Co with the owner behind the counter! I could not belive that i did not have to beg to spend my money and that i could get service after the sale! Two thumbs up for Ray Allen Co.

P.S ( he's one of us, building a -6)
 
AircraftExtra Servo installation with Ray Allen Trim

If you are saying RAC is ray allen. Their relays are junk. AFter changing two on my kitfox, I went to these units very nice, never another problem. Oh and the ray allen relays would poop out at 300hrs. Go half way down the page. I put these on my flaps and the elevator trim in the RV.
http://www.aircraftextras.com/Index.htm

I'm doing exactly the same..... aircraftextras' relays going in my RV7.
I've installed a Ray Allen stick, and their trim motor in the tail.
Would you have any wiring info to help me out on the ground work...?

Rgds... Chris
 
I'm curious, has anyone actually experienced a runaway trim condition with a RAC system?

This is copied from the RAY ALLEN website:

"Can a RAC servo "runaway" and travel uncommanded?

"No. Although RAC servos have sensors that feedback information to our indicators, there is no electronic connection between the sensor and the electric motor. The only way to get movement out of a Ray Allen (or a MAC) servo is for the pilot to manually switch on power. Our REL-1 or REL-2 relay failure will not cause a runaway trim.

Some cautions about using any relays (including our REL-1 and REL-2) to control our servos. First is that the relay, not the pilot, is controlling the servo. Second is you are controlling the relay. These relays are activated by a ground signal so a short to ground will lead to servo movement. Make sure the wire leading from your switch to your relay is not shorting to ground!"


I called them to ask about something else and they also added that if the relay is shoddily or improperly wired and it grounds out then the servo will move.
 
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