Trim indicator

[rhtrudder]

My trim indicator , series of leds , is showing out of range , gaps at the bottom , over full at the top, unsure how to adjust, something to do with the trim motor in the elevator I’m thinking , any ideas, thanks , Greg 

[danny_galaga]

I would imagine there's a potentiometer at the motor end to feed back the position. But I'm just guessing. Is it a tecnam?

[skippydiesel]

Just wondering, why you need a trim indicator ??

[facthunter]

So you can set the trim to a required position as part of the pre take off check. If the position of the lever gives the position you don't require anything else.. Sometimes  preflight you run the trim through the full range and check the actual trim moves with it and return it to neutral  or in case of the pitch trim in a position the load sheet Balance dictates. Nev.

[rhtrudder]

Without the indicator I haven’t got a clue where it’s set until I leave the ground 

[Thruster88]

3 hours ago, skippydiesel said:

Just wondering, why you need a trim indicator ??

They say there is no such thing as a stupid question.  I am not so sure. I would not like to takeoff in the RV with full flap landing trim still set. The stick would get very light very quickly. I like the trim indicator. This is a trim tab system not a spring thingy. 

Edited September 27, 2021 by Thruster88

[skippydiesel]

Oh well I am sure you are all correct, however on my Zephyr, trim can be visually assessed by looking at (or even just feeling) the positions set for longitudinal/lateral and although like Thruster's RV I would not like to attempt a TO with full trim in either direction, the landing trim would not be much of a problem (even in a go round) as moderate muscle power can easily overcome the trim setting, at least until you have time to make some comfort adjustments.  So give me manual trim (KISS) on RAA class aircraft any day, no need for indicators (that may go wrong).

[Thruster88]

Visually assessed, so you do have a trim indicator. My Musketeer has manual trim which I like very much, it also has an indicator, good because it is a very powerful system.

Edited September 27, 2021 by Thruster88

[Bruce Tuncks]

The best trim ever was on my Libelle glider. There was a button on the stick, and this got rid of any back or forward pressure immediately.

In use, it became subconscious.  No electronics involved at all.

[skippydiesel]

2 hours ago, Thruster88 said:

Visually assessed, so you do have a trim indicator. My Musketeer has manual trim which I like very much, it also has an indicator, good because it is a very powerful system.

Yeah! Pre-flight, I just look at or feel for the position of the trim lever - not much to go wrong. As for in flight - all adjustments done on control "feel" (nothing visual).

[kgwilson]

I have a trim wheel without a trim tab. The trim just adjusts the entire horizontal stabilator via bungees on the stick & I only use it for hands off cruise. The stabilator is very light in all situations right up to MTOW. 

[danny_galaga]

10 hours ago, skippydiesel said:

Yeah! Pre-flight, I just look at or feel for the position of the trim lever - not much to go wrong. As for in flight - all adjustments done on control "feel" (nothing visual).

Yes but on the electric trim like in a Tecnam, it's just a two way spring toggle. The switch always looks the same. Same with the flaps. Although you can see the flaps visually. 

Edited September 27, 2021 by danny_galaga

[skippydiesel]

44 minutes ago, danny_galaga said:

Yes but on the electric trim like in a Tecnam, it's just a two way spring toggle. The switch always looks the same. Same with the flaps. Although you can see the flaps visually. 

My point exactly - an unnecessarily complicated system for an aircraft of this class.

[danny_galaga]

1 hour ago, skippydiesel said:

My point exactly - an unnecessarily complicated system for an aircraft of this class.

If your argument is that electric trim is unnecessary, I don't disagree. I hate it on the Tecnam. It feels more like a timing thing than a trim thing when you use them

[sfGnome]

I’m not sure about all Tecnams, but my old one had a fully moving stabilator. I expect that a mechanical trim on it would involve a fairly complicated mechanism, so a small motor and a couple of electrical wires seems somewhat simpler. Having said that, we did have a problem where the pot that sensed the trim position got corroded so the indicator became flakey and we had to replace the whole subassembly, so nothing’s perfect. 🤨

[facthunter]

The  advantage of electric is you can have a two way switch on the control column and don't need 3 hands. Nev

[danny_galaga]

1 hour ago, sfGnome said:

I’m not sure about all Tecnams, but my old one had a fully moving stabilator. I expect that a mechanical trim on it would involve a fairly complicated mechanism, so a small motor and a couple of electrical wires seems somewhat simpler. Having said that, we did have a problem where the pot that sensed the trim position got corroded so the indicator became flakey and we had to replace the whole subassembly, so nothing’s perfect. 🤨

Yes, the Golf I hire has the stabilator. But so did the Piper Warrior I learnt to fly with, and its trim was mechanical. Facthunter is right about the control column switch being handier (I said toggle before but I misremembered it with the flap switch- old age I guess 😄 ) . Even so I really don't like the feel of it.

[Steve L]

Give me a mechanical trim wheel any day, more precise control and its not subject to electrical faults. Unless a cable breaks they are generally sound, but an electric trim can run away and unless you can reverse it an aircraft is near impossible to fly in full nose down or full nose up trim, especially with a full flying tail plane. 

[facthunter]

If a mechanical trim wire breaks you'll probably get flutter.   If something small goes to the trim limits you are either in trim at high speed or low speed. It's not as if you can't fly it.. Nev

[skippydiesel]

1 hour ago, facthunter said:

If a mechanical trim wire breaks you'll probably get flutter.   If something small goes to the trim limits you are either in trim at high speed or low speed. It's not as if you can't fly it.. Nev

Not all small aircraft use a trim tab to achieve a trimmed state - many use spring/bungy devises.  If these break,  you just have a slightly heavier stick.

[facthunter]

Probably only one of two would break so you'd have trim remaining in one direction. Quite a lot of planes use spring bias. It means you only have one go at pitch control. Nev

[Steve L]

Yes you may get flutter or a heavy control column in one direction but I presume still flyable,  A runaway electric trim fully in one direction is another story. I dislike electric. 

[facthunter]

The flutter i  refer to is only the trim tab once it's cable is no more. Who knows what it would eventually do it would probably sound like a bullroarer or Kazoo and separate in bits...

  ' Electric is full of problems, runaways and limit switch issues. Big stuff has a trim BRAKE for runaways and it's got a really savage action but usually you are moving the entire horizontal stabiliser. which has enormous authority on the aircraft's pitch, and cant be overpowered by the stick forces unless you do some trick  actions. Nev

[Marty_d]

The answer to this may be completely obvious, but why isn't trim automatic - ie mechanically linked so that when the control surface goes one way, the trim goes the other?

[danny_galaga]

1 hour ago, Marty_d said:

The answer to this may be completely obvious, but why isn't trim automatic - ie mechanically linked so that when the control surface goes one way, the trim goes the other?

I think it did on the Piper Warrior?