Ray Allen Frequently Asked Question's Index

Servo / Relay / Switch FAQ's

My servo is not working correctly.
Do you have any electrical connectors available?
What kind of circuit breaker and wire should I use?
Is there a way to slow down my servo?
Can I replace my MAC 3 light indicator with a newer style, RP2 Needle or RP3 LED Indicator?
Do you have any STC's?
Can a RAC servo "runaway" or travel uncommanded?
I am designing my own electric trim system to use your servo. Suggestions?
Can I use a RAC servo inside the engine cowling?
Will a RAC Servo work with my autopilot?
Do I need aileron trim if I have a wing leveler?

Indicator / Sensor FAQ's

How do I get a label for my Indicator/Rocker Switch?
My Indicator is not working correctly.
How do I connect my POS sensor to my Flaps?

Stick Grip FAQ's

Can a Ray Allen Stick Grip be used with a 1 1/8" control stick?
Does the PTT switch on the G101 work with a handheld radio?
How far does the control stick tube penetrate your grips?
What is the best way to slide the foam grip on my control stick tube?


Servo / Relay / Switch FAQ's

My servo is not working correctly

If the servo is not sending a signal to your indicator, please refer to the Indicator FAQ.

When troubleshooting a suspect servo, we like to work from the servo back to the switch. First, test the servo. You can do this by putting power (a 9 volt transistor radio battery works great) across the two white wires. The servo should move in and out by alternating the polarity of the white wires. Make sure to test the servo all the way until it shuts itself off in either direction.

Next, do you have any connectors in your wire harness? If you are doing a continuity test on your connectors and wire harness, be sure and disconnect the servo and the switch and the indicator.

When you confirm you have an operating servo and a good wire harness, work upstream from the servo to the switch. If you are using a RS2 rocker switch as the only switch in your trim system, make sure you have a good power and ground to the switch.

Does your installation use relays? If your servo is intermittently traveling in one direction and not the other, it probably means you have a relay failure. If the servo is not working in both directions, suspect the switch to relay wire harness.

Still scratching your head? Call us at 760 599 4720. We are here to help.

Do you have any electrical connectors available?

No. However, there are several on-line electric parts distributors that have good selections of connectors. Digikey.com, Newark.com and Radioshack.com are good places to start hunting for your electrical needs.

It is important to note that the majority of the troubleshooting problems builders have with installing our products are faulty connectors. Most RAC products use 26 gage wires which are sensitive to improper crimping. Try doubling over the wire over OR soldering a short 22-24 gage lead to our 26 gage wires before crimping to provide extra strain relief. Whatever kind of connector you choose, they can often be made much smaller by removing the strain relief boot and using shrink tubing.

Of course, you do not have to use connectors. Just solder the wires together with appropriate heat shrink for insulation and strain relief. Where possible, leave a little service loop of wire tied off in case you need to cut the wires to remove anything later.

What kind of circuit breaker and wire should I use?

The full stall current of the T2 and T3 servo is only 800 milliamps. The T4 servo is less than 400 milliamps. A 1 amp circuit breaker can handle 2 trim systems. NOTE: We recommend running the servo off the master bus of your aircraft's electrical system and running the indicators off the avionics bus. This adds another level of protection for the indicators from any stray voltage spikes caused by the engine start/shutdown. It also allows you to shut off power to the indicator should a problem arise and still have your trim servos operational.

Any high quality, multi strand (the more, the better for flexibility) wire down to 26 gage can be used, which is what we use for our servo, indicator and switch leads. It takes a total of 5 wires to connect the servo to the switch and indicator. We have available a 19 strand, 5 conductor, 26 gage Teflon® insulated, color coded wire cable in our accessories section.

Teflon® or Tefzel® insulation is preferred and required for certified aircraft. Teflon® especially is very heat resistant, but very tough and slippery making it difficult to work with unless you have the correct stripper. A company called Ideal makes a great, inexpensive 26 gage wire stripper. It can be acquired from Sears, Frys or any number of electronic distributors.

Is there a way to slow down my servo?

Yes. Our Servo Speed Control does just that. Other companies, (Matronics, aircraftextras, f1-rocketboy) have similar products available. Be advised that our T2 and T3 series servos (and the MAC 4A, 6A and 8A servos) are slower than the MAC S4, S6 and S8 servos. We suggest flying the airplane first and then, if desired, install a speed control. Our speed control is very small and easily wired in afterwards. However....

Our servo motor speed was tailored for use with a RAC rocker switch. This rocker switch is designed to be installed in an instrument panel and tapped by an index finger at higher airspeeds when trim is the most sensitive. Switches mounted on a control stick are commonly activated by a thumb, a naturally more clumsy extremity than an index finger. If you are using a stick mounted switch to control your trim, you may want a speed control. But....

Some experimental airplanes cruise at speeds surpassing 4 times their landing speeds. A servo speed that is slow enough for precise trimming at 200+mph, (especially with a stick mounted switch), is bound to be too slow for pattern speed. When you lower full flaps rolling into a tight base to final turn, you want your trim to operate quickly. A common solution to this problem we've seen homebuilders do is install a speed control defeat switch that takes the servo speed control out of circuit and allows the servo to run at normal speed in the pattern. Some clever builders use the gear down switch to take the servo speed control out the circuit. It's your airplane, wire it any way you please.

Can I replace my MAC 3 light indicator with a newer style, RP2 Needle or RP3 LED Indicator?

No. The older MAC S4, S6 and S8 servos that drive the 3 light indicator lack the feedback potentiometer necessary to drive the needle or LED indicator.

Do you have any STC's?

Yes, and no. Although several newer aircraft have been certified with our trim systems in them, STC's for retrofitting our trim systems are difficult to obtain. There are a few. Call for more information.

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 am designing my own electric trim system to use your servo. Suggestions?

We prefer a trim tab for consistent feel. Springs seem to be less exact and have a tendency to act like, well, springs.

When using an application that requires springs, using the longest travel servo/actuator you can find seems to give the best "feel". Our T3-12A (MAC 8A) servo with 1.2" travel works fine with aileron trim springs which generally have lighter tension (the Van's RV-8 installation is an excellent example). However, some springs in trim systems, (the Glasair III elevator for example), are too powerful for our servos. The springs on..say...a Long-Eze elevator (about 20lbs. of force) are about the strongest springs our servos can be used on.

Moving the entire horizontal stabilizer is complicated and requires a very strong actuator. Our servos cannot be used in this application.

When designing and building a trim tab, remember the following:

You are building a control surface just as important as the one you are trimming. Failure or slop in your trim control linkages can be just as dangerous as failure in the control surface itself. Make the tab large enough so that it doesn't need more than 25 degrees travel (in each direction) to trim the aircraft at both extremes of travel. Try to keep the chord of the tab under 4". Be sure that the servo doesn't bind up throughout it's complete range of travel and that it turns itself off automatically.

Please Do Not be tempted to use too short of a trim tab control arm just for the sake of streamlining your trim tab installation. You will end up with a trim tab that is too sensitive and/or has too many degrees of arc travel. We have a .pdf document (called a trim tab travel computer for lack of a better name) that we use in the shop that shows the relationship of trim tab control arm length and servo travel. It also shows the degrees of arc the tab will travel.

Can I use a RAC servo inside the engine cowling?

We know of our servos that are used successfully inside cowlings, but we are hesitant to recommend it. Although the DuPont Minlon® brand nylon we use is the same basic type that is used in BMW valve covers, the strength of the gears inside get weaker as temperatures climb above 180 degrees F. Try to keep the servo in a ventilated location under the cowl away from exhaust pipes or better yet, behind the firewall.

Will a RAC Servo interface automatically with my autopilot?

Yes, if the autopilot is designed for use with an electric trim. However, it is important to realize that you are inserting what is effectively an electronic switch (the autopilot) in your trim system to automatically power your RAC servo. Do you really want to do that? We would rather see YOU switch on power to the servo, perhaps with the aid of a trim prompter light. Contact your autopilot manufacturer for more details.

Do I need aileron trim if I have a wing leveler?

Not necessarily. But remember, your autopilot roll servo will be working only when your autopilot is on. Click it off and you could be in for a surprise, especially if you've forgotten to change the outboard tip tanks for an hour.


Indicator / Sensor FAQ's

How do I get a label for my Indicator/Rocker Switch?

Send us a self addressed, stamped envelope and we will send any label you need. See the Indicator page for the selection of labels available.

My Indicator is not working correctly.

First, make sure all connections are correct and that the orange wire is not connected to 12V+. If the orange wire has been connected to 12V+, the indicator must be returned for repair.
The RP3 LED Indicator and the RP2 Needle Indicator work very well displaying relative position of the servo output shaft, but are not exact (depending on the servo model). It's normal for these indicators to display slightly off center when the servo output shaft is exactly centered.

Our indicators will not work wth a glass panel display in line.

Specific troubleshooting the LED type indicator:
If one light comes on at the end of travel and doesn't register servo movement, the indicator is probably working correctly, it's just not connected to the servo or sensor. Try checking the continuity between the orange, green or blue wires connecting the servo to the indicator.
If the LED light bar tracks correctly, but has one or more of the lights burned out, the indicator must be returned for repair.
If the LED's register movement when you transmit on the radio, you have an antenna cable running to close to your servo to indicator wire harness.

Specific troubleshooting the Needle type indicator:
If, after wiring your indicator the needle moves in the opposite way you desire, DO NOT flip the needle indicator upside down, simply reverse the orange and blue wires that connect it to the servo or sensor.

How do I connect my POS sensor to my Flaps?

The POS sensor must be pushed in and pulled out to send a signal (via the green wire) to the indicator. A "Z" bend in a 1/8" piano wire works fine. RC model hobby stores have all kinds of cool little connectors. We like R/C model car ball links (see www.dubro.com). These connecting devices are usually tapped 2/56 making adjustments easy.


Stick Grip FAQ's

Can a Ray Allen Stick Grip be used with a 1 1/8" control stick?

Yes, but only the G3 series. The G1 and G2 foam grips usually tear when stretching over anything larger than 1" control stick tube.

Does the PTT switch on the G101 work with a handheld radio?

We've heard that some handheld radios require a double pole, double throw (DPDT) push to talk (PTT) switch. The PTT switch on the G101 grip is single pole, single throw (SPST). Check your handheld radio's specifications carefully to see if this adequate.

How far does the control stick tube penetrate your grips?

The G101 will penetrate 4.3" (109mm). The G101 will need 0.45" (12mm) of clearance above the stick tube. More if you want to activate the PTT without shaving your fingers off under the instrument panel.

The G205/207 will penetrate 4.3" (109mm). The G205 will need 1.1" (28mm) of clearance above the stick tube. The G207 will need 1.3" (33mm) of clearance above the stick. The same G101 finger caution applies here too.

The G3 series will penetrate 2.75" (70mm). The G3 will need an additional 3.75" (95mm) of clearance above the stick. The G3 does need additional finger clearance.

What is the best way to slide the foam grip on my control stick tube?

Blow compressed air when you slide the foam grip on the tube or spacer. This momentarly expands the foam grip allowing it to slide down the tube with hardly any friction. There are other ways, (soapy water, special greases), but compressed air works MUCH better.


Still have questions?

Please call us! We are here to help you build a safe trim system.



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