BloomerJohn

BloomerJohn

Member
I have an RV6, with manual vernier controlled elevator trim. What is needed/involved to convert to electric. Is ther a conversion kit that makes it simple?

Thank you in advance.

John Nielsen
 
Define 'simple' ...

There are 2 ways to go:
- the Vans method which mounts the servo in the elevator
- mount the servo on the HS deck and run a cable to the trim tab.
(I forget who sells this one)

Technically speaking, the Van's method would require you to rebalance your elevator due to the weight of the servo being mounted on the access panel. That's why the second method may be easiest for you, since no rebalancing is needed.

The tough part is deciding where to put the trim switches (panel, stick, both) and indicators, and modifying the panel and doing the wiring. The wiring that Ray Allen uses is very small.
 
Let me expand upon Sam' question

I have the manual. It is reasonably sensitive in that I can adjust as much or as little as needed. A friend who has the electric is looking to modify it to get less adjustment per "activation." In other words it is too sensitive.

Of course Sam may have meant something better.
 
Ron Lee said:
I have the manual. It is reasonably sensitive in that I can adjust as much or as little as needed. A friend who has the electric is looking to modify it to get less adjustment per "activation." In other words it is too sensitive.

Of course Sam may have meant something better.
Click to expand...

You got it. Just curious why someone would want to change from a good manual trim system to an electric system that offers no advantages (and some disadvantages).

But, the original poster may have valid reasons for making the change (auto-trim with an autopilot?)
 
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EZ Trim

There is a guy that came up with a electric trim comversion for a RV-4 that actuates the trim lever but preserves the capability to manually move the trim. I just installed this on my RV-4. I made some changes to his design that were more personal preference than anything else. I haven't flown it yet but it moves the trim tab just fine sitting in the hangar. I'll try to post a link if I can find one. Also, I don't know how the -6 is set up. This may or may not work for you. Good luck.
 
Weight...

Sam Buchanan said:
You got it. Just curious why someone would want to change from a good manual trim system to an electric system that offers no advantages (and some disadvantages).
....
Click to expand...

Sam... one advantage is quite a measureable weight savings.

The long cable and big knob assembly weighs a lot more than a little Ray Allen servo and two small switches...:)

gil A - above comments are for the weight obsessed RV builders...:)

PS - being an electronics engineer, the electrical solution is more to my liking...:D
 
I Wish I Had Manual Trim...

I love the feedback of the manual trim, where you can feel where the trim needs to be through the knob. I doubt I will convert mine to manual because of the work involved, but I absolutely prefer the manual system.

Hans
 
Reducing electric trim speed

Matronics.com has a very nice unit that reduces trim speeds. Works great. A small screwdriver allows you to make adjustments.
 
The manual trim is a better way to go plus out of 8 airplanes around here that have the electric trim most have had servo problems. Don
 
One good reason for electric trim

I fly an -8 and have been concerned about what would happen if I were incapacitated in the front with someone in the back unable to control throttle and pitch trim. I will be installing the rear seat throttle soon which solves the bigger problem.

While I like manual trim, I am thinking of converting to electric trim so the back seater can set the trim and therefore airspeed and improve their chances of getting down safely.

My health is really good, but you never know...
 
Trim from back seat if front seater incapacitated

I doubt that this is a major issue. Unless you have the trim at one extreme, you should still be able to fly the plane and get on the ground.

Do whatever makes you happy.
 
Bubblehead said:
I fly an -8 and have been concerned about what would happen if I were incapacitated in the front with someone in the back unable to control throttle and pitch trim. I will be installing the rear seat throttle soon which solves the bigger problem.

While I like manual trim, I am thinking of converting to electric trim so the back seater can set the trim and therefore airspeed and improve their chances of getting down safely.

My health is really good, but you never know...
Click to expand...

I've flown my -8 with the trim WAY out (during phase 1, and when the trim relay got sticky), and while not desirable, it is flyable - wouldn't worry that much about it.

If the only reason you're doing a rear seat throttle is for pilot incapacitation, there are simple ways of doing it....here are a few ideas. Of course, without rudder pedals, the landing will be a bit sporty....
 
Ron and Ironflight,

Thanks for the information. I have Van's kit but like the simpler one a lot and will probably just use some of the parts from Vans to make one like Dan Horton's.

I am sure I could handle the plane being out of trim for slow speed flight, but what about my wife who does not have the same finely honed musculature as I do? Also, if she gets tired and lets off some stick pressure will the plane nose down dramatically?

I think it best if I go flying the -8 this weekend to check out the required forces myself. :)

I do have rear seat rudder pedals already, however my wife is not a pilot so I'm thinking of this more as a "pinch hitter" training opportunity so she can have some chance of getting it down reasonably safely. I also fly a lot with my son in the back, who is a pilot, so a throttle will definately add to his safety.
 
So you are putting in electric trim so your wife...who is not a pilot and may not even be able to maintain altitude (unknown) can land a taildragger from the back seat?:confused:
 
reviewing this thread

Ron - I'm just trying to give my wife every chance to get down safely. If she 1) can control the throttle and 2) can trim for an airspeed and 3) practices with me in front she has a lot better chance to survive than she does today.
Even if she runs off the runway or lands off field her chances will be much better if she is is able to trim the airplane.
It doesn't have to be pretty and it does not have to save the plane. Just save herself.
John
 
To each his own I guess. I prefer electric trim for a lot of reasons, most of which have been stated in this thread. An additional advantage is you can control trim from your stick with your flying hand. One more advantage is that with a Tru-Trak DigiFlight II autopilot, the auto-trim module is a wonderful addition. I have it in my -8 with AFS system and really like it. Once you're on EFIS AP control you don't have to worry about pitch trim - the module does all of the trimming for you.

One way to rectify the sensitive electric trim at higher airspeeds is to install a TCW Tech Safety Trim module with airspeed switch. That system allows two trim speed settings; the slower trim speed is activated by the airspeed switch. Works great, plus this system helps to prevent a run away trim condition.
 
I hadn't flown with manual trim until I bought my -6. Same for the flaps, for that matter. Now that i've flown with the manual trim though, i'm liking it. I find it allows for finer control when I want it, and I can overpower it briefly if I need a larger change and it takes a minute to spin the knob. I wonder if anyone has tried a pushbutton vernier on their trim, so they could spin it for fine adjust, and push the button to push-pull for coarse?

I'm considering switching my flaps over from manual to electric, but I don't think i'll switch the trim. Not yet. The only thing that makes me want it is a possible future upgrade to add an autopilot. If I were to do that, wouldn't I need a servo on the trim? Or would I have to add a second one?
 
Snowflake said:
....... I wonder if anyone has tried a pushbutton vernier on their trim, so they could spin it for fine adjust, and push the button to push-pull for coarse? ........
Click to expand...

There was a button on my -6 when I bought it, and it is WAY too sensitive to push and pull the trim knob. Just turn it, you'll like it much better. (Talk about over-contol!!):eek:
 
I cannot imagine ever needing to make THAT much trim adjustment to require a push-pull knob. Even when getting into the pattern and putting down full flaps, I only end up turning the knob about 2-3 revolutions at most.

greg
 
Snowflake said:
I'm considering switching my flaps over from manual to electric, but I don't think i'll switch the trim. Not yet. The only thing that makes me want it is a possible future upgrade to add an autopilot. If I were to do that, wouldn't I need a servo on the trim? Or would I have to add a second one?
Click to expand...

A pitch autopilot will work fine with either manual or electric elevator trim, no need to change your trim system. You will add an autopilot servo at the elevator bellcrank behind the baggage compartment.
 
I've electric elevator trim (controlled from the hat switch on the stick) in my -7 from the get go and in the 100hrs since haven't had any failures, nor any issues with over/undercontrol. I did have manual aileron trim, and that was a pain -very undersensitive and reaching between the seats when 2-up got awkward at times - so converted to electric aileron trim today.

Will be testing it tomorrow so don't have any feedback on sensitivity, but the replacement was pretty straight forward.
 
Sam Buchanan said:
A pitch autopilot will work fine with either manual or electric elevator trim, no need to change your trim system. You will add an autopilot servo at the elevator bellcrank behind the baggage compartment.
Click to expand...
Ah, I see. So with manual trim if I wanted autopilot I would add a servo at the bellcrank, and then carry the weight of both the servo and my manual trim system. But if I replaced the manual trim with an electric trim, I could use that servo for autopilot as well, right?
 
Snowflake said:
Ah, I see. So with manual trim if I wanted autopilot I would add a servo at the bellcrank, and then carry the weight of both the servo and my manual trim system. But if I replaced the manual trim with an electric trim, I could use that servo for autopilot as well, right?
Click to expand...



No.

You'll add a servo at the bellcrank, and either retain the manual system, or add another servo (much smaller & lighter than A/P servos) for elec. trim.

I have the smaller, lighter, & cheaper "Ray Allen" electric servos for both elevator & aileron trim. In my 6A, it uses a servo operated tab on the aileron, & servo mounted in the elevator.

Auto-pilot pitch is done with a TruTrak servo on the bellcrank behind the baggage bulkhead. And a Trio servo is mounted in the right wing tip for roll.

L.Adamson -- RV6A
 
Elliminate the push/pull capability.

PCHunt said:
There was a button on my -6 when I bought it, and it is WAY too sensitive to push and pull the trim knob. Just turn it, you'll like it much better. (Talk about over-contol!!):eek:
Click to expand...

Van's recommends removing the button to disconnect that capability. It has caused problems in the past when inadvertantly operated.
 
In my case I do not have any autopilot and just want to get to where a back seater has some chance of getting down safely. The Ray Allen electric pitch trim looks like the way to go along with a manual throttle control. Those two things would increase safety a lot.
 
L.Adamson said:
No. You'll add a servo at the bellcrank, and either retain the manual system, or add another servo (much smaller & lighter than A/P servos) for elec. trim.
Click to expand...

That seems counterintuitive to me... If i'm flying along in cruise, and give a turn or on my trim, I can effect a significant change in altitude. Presumably an electric trim servo could do the same. Why wouldn't you want to use just *one* servo, for both trim and autopilot?

Maybe there's something about autopilots that i'm not understanding...
 
Snowflake said:
That seems counterintuitive to me... If i'm flying along in cruise, and give a turn or on my trim, I can effect a significant change in altitude. Presumably an electric trim servo could do the same. Why wouldn't you want to use just *one* servo, for both trim and autopilot?

Maybe there's something about autopilots that i'm not understanding...
Click to expand...

First off, you want the plane trimmed before engaging the auto-pilot. It's not fun to disengage an A/P and find the plane way out of trim.
When a trim servo is in position to keep the airplaned trimmed, there is no load on servo motor at that point. If the auto-pilot is forced to maintain trim, then there is always a load on the motor & linkage. Some people feel that using an A/P for trim (especially roll) is good enough. I don't. That's why I like having aileron trim. Some A/P setups can monitor the load on the A/P servo & automatically adjust the trim servo to compensate, or have lights that show which way to adjust.

L.Adamson --- RV6A
 
Snowflake said:
That seems counterintuitive to me... If i'm flying along in cruise, and give a turn or on my trim, I can effect a significant change in altitude. Presumably an electric trim servo could do the same. Why wouldn't you want to use just *one* servo, for both trim and autopilot?

Maybe there's something about autopilots that i'm not understanding...
Click to expand...

Let's see if we can clarify the autopilot system for you.

There has been at least one vendor attempt to control the pitch/altitude hold of an RV via a servo on the elevator trim tab. This did not prove to be practical because the trim servo was always "chasing" the desired pitch/altitude instead of being able to accurately maintain the selected altitude. The trim tab just doesn't have enough control authority and the trim servo is too slow to allow for accurate pitch control. In addition, if you have a servo fast enough to serve as an autopilot, it is far too fast to serve as trim. Been tried, just doesn't work with our planes.

Consequently, a faster, stronger servo input is needed and that is easily supplied by a digital servo attached to the actual elevator control pushrod system. In our side-by-side planes, the servo is attached via a short pushrod to the elevator bellcrank just aft of the baggage bulkhead.

If you have your pitch autopilot engaged and merely make a minor change in the elevator trim setting, the aircraft will continue to fly the selected altitude because the autopilot will sense the trim input, but quickly (probably before you can even feel it) compensate for the new trim pressure by establishing the elevator position needed to hold the selected altitude. If you crank in enough trim to really throw things out of whack (WHY would you do that??) the servo may be overpowered by the heavy control pressure and either automatically disengage or present an indicator that warns the pilot of our very out-of-trim situation.

Maybe this fills in the gaps for you. The digital autopilots are amazing devices and fly our planes very accurately.
 
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Sam and L.Adamson, thanks for the explanations, I understand now. I've flown in a -7 with autopilot, and agree that it's an amazing piece of kit. Maybe if I upgrade my panel in the future i'll add that as well. For now, i'll have to stick with just following someone else's autopilot... :)
 
Autopilot and trim system

So, what you are saying is...............................You can have a manual trim system (elevator/aileron) and have a digital autopilot that is fully capaple of flying a waas coupled approach?
I was thinking that the digital autopilot (ie; TruTrak) would be able to (and need to) automatically trim the airplane via trim servo's during..........say a coupled approach. But you are saying that the autopilot only drives the bellcranks and never the trim motors?
 
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