manual or Electric trim

[Scott Hersha]

[quote=Walt;1714616]All modern glass panels have auto trim and speed control based on airspeed

Well, not really. I have a modern glass panel, and it doesn’t have auto trim, or speed control based on airspeed, and I have a two axis autopilot (GRT). It depends on what primary system you are using. The Garmin G3X has an auto trim system, so if you want that feature to work, you’ll need electric trim.

On my airplane, and many others without auto trim, the autopilot performs very well without it. My EFIS indicates when it needs some trim (seldom) and I can then move the trim - either electrically or manually doesn’t matter. I have electric pitch trim in my RV6 and manual aileron trim. My autopilot almost never asks me to change trim. When it does, the pitch trim is controlled by the RAC rocker on the IP right next to my throttle. One bump on that switch moves the trim a tiny amount. I can hold it down for increased trim rate.

Saying you need electric trim for autopilot equipped airplanes just isn’t true, and that’s what the OP was asking for. Depends on what other systems you have in your airplane, and what geewhiz options you want to have.

[MacCool]

Originally Posted by Scott Hersha

Saying you need electric trim for autopilot equipped airplanes just isn’t true, and that’s what the OP was asking for. Depends on what other systems you have in your airplane, and what geewhiz options you want to have.

Exactly. If my airplane on autopilot needs to be re-trimmed, it tells me and I just give the knob a little tweak. No big deal.

[Walt]

Guess it depends on definition of “modern”, Garmin, Dynon/Skyview, AFS all provide auto trim w/speed defined trim speed.
I never said you “need” it, but it’s a very nice feature, take it or leave it.
We don’t “need” lots of features we have these days, but many make flying more enjoyable and safer.

[SonexGuy]

Anyone have their manual trim on the LEFT side, against the fuselage side? I like to fly aerobatics with my right hand on the stick, and the left hand on the throttle, so will have my trim on the left.

I'm going with a UL engine with fuel injection and electric CS prop, which uses a prop control on the panel and not on the throttle quadrant. So my plan is to have a throttle quadrant on the left, with a second handle on the quadrant that will be the manual trim. Think of a throttle quadrant with a throttle and mixture, but the mixture handle would be the trim, instead.

Mostly I'm wondering how the manual trim cable might get routed. I don't have my fuselage kit, yet, so I don't have anything to look at and scratch my head about.

[Scott Hersha]

Originally Posted by SonexGuy

Anyone have their manual trim on the LEFT side, against the fuselage side? I like to fly aerobatics with my right hand on the stick, and the left hand on the throttle, so will have my trim on the left.

I'm going with a UL engine with fuel injection and electric CS prop, which uses a prop control on the panel and not on the throttle quadrant. So my plan is to have a throttle quadrant on the left, with a second handle on the quadrant that will be the manual trim. Think of a throttle quadrant with a throttle and mixture, but the mixture handle would be the trim, instead.

Mostly I'm wondering how the manual trim cable might get routed. I don't have my fuselage kit, yet, so I don't have anything to look at and scratch my head about.

My RV4 (that I didn’t build, but bought) had a manual trim lever on the left wall right next to the throttle quadrant. It was standard build per plans. Maybe you can get a copy of the RV4 plans and duplicate for your RV7.

[bruceh]

One other consideration: the manual trim cable is heavy versus the lightweight wires for the electric trim.

[Desert Rat]

You could argue the pros and cons of each until the cows come home and still not come to a consensus. There are just too many variables that have to do with what other magic boxes you have installed.

Personally, I wouldn't want electric trim if I didn't have some way to speed schedule it. I've been there done that in other planes and the trim gets annoyingly sensitive at high speed.

I have a speed scheduling solution via Garmin, so I went with electric for the simplicity of the installation and the weight savings (especially applicable to the elevator trim).

I have zero concerns about a trim runaway. I've heard about this for 30+ years now and still haven't experienced any autopilot or trim system going rogue terminator and trying to kill me. In the unlikely event that it does happen, that's why those breakers are easy to find by feel.

[Caveman]

Here is another option if you have older glass or steam gauges. I installed it during the build 15 years ago and it has worked flawlessly.
https://www.tcwtech.com/product/safe...vo-controller/
Thanks,
Joe

[BobTurner]

Originally Posted by Caveman

Here is another option if you have older glass or steam gauges. I installed it during the build 15 years ago and it has worked flawlessly.
https://www.tcwtech.com/product/safe...vo-controller/
Thanks,
Joe

This ^^^works. If you’re handy with electronics you can build something like it for just a few dollars. Or, still another option, the Trio autopilot offers speed sensitive auto-trim. e.g., the higher the airspeed, the slower the trim runs (you set the parameters). And you can use it in a manual mode (I frequently do) when hand flying with the servos disengaged.

Side note: I guess I’m getting old, but I find it annoying when internet posters use the expression ‘is a must’ to mean ‘is nice’, when the common English dictionary interpretation of ‘must’ is ‘required’. Looking at the comments I see others are bothered, too.

[Richard Connell]

Originally Posted by BobTurner

Side note: I guess I’m getting old, but I find it annoying when internet posters use the expression ‘is a must’ to mean ‘is nice’, when the common English dictionary interpretation of ‘must’ is ‘required’. Looking at the comments I see others are bothered, too.

Pedants unite! :-)
I had auto trim in my RV7 15y ago. It’s not new technology.
Now speed scheduling and auto trim is affordable and ubiquitous. I doubt many RVs are built with manual trim these day. The weight alone is worth considering.
Trim runaways are the RV bogeyman. Much discussed but never seen.
For those who have seen it would state that the plane is completely flyable at each extreme. We have all tested that in phase 1 right? It’s not a 737.
Plenty of ways to mitigate that extremely low likelihood failure.