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Trim Capability

P

PeteT

I'm New Here
Happy Holidays Everyone!

Our 14A will have Garmin servos for pitch and roll. I have not considered any other “fly by wire” gear as in aileron or yaw trim.

The fuselage is complete with pitch servo and pushrods installed, the wings are just about ready for the bottom skins. We’re reconsidering the aileron trim installation.

Curious if such trim is a “must have” or a nice extra.

Thanks-
Pete
 
I would definitely recommend the aileron trim.while hand flying if you have a heavy tank you can trim that out,well worth the time and money.
 
If you do install the trim, be aware the oem clips that secure the springs in place are too short. They cause the spring to rub on the CS-00012 pushrod. I made a couple new clips that were taller. Got the idea from another builder’s post on VAF.
20220115_161854.jpg
 
mc607 said:
If you do install the trim, be aware the oem clips that secure the springs in place are too short. They cause the spring to rub on the CS-00012 pushrod. I made a couple new clips that were taller. Got the idea from another builder’s post on VAF.
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I found I had squeaking after installing the trim springs, but after I turned the springs over (wire ends away from the push rod, I think), it eliminated the squeaking. Try different orientations. YMMV.
 
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MED said:
I found I had squeaking after installing the trim springs, but after I turned the springs over (wire ends away from the push rod, I think), it eliminated the squeaking. Try different orientations. YMMV.
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I had read that changing orientation could fix it, but it didn’t make a difference with the springs I had. I even added new springs to an order, they were quite cheap. Still rubbed. I agree that changing orientation from what’s shown on the drawings could work, just didn’t work on mine, or the replacements.
 
Bending the control arm a small amount away from the pushrod also helps with spring rubbing.
I preferred the aileron trim system in the RV7 than the pushrod based version in the 10/14. Accessibility is much easier.
But after a lot of fiddling I got satisfactory operation with the 10.
 
Walt said:
I'm not a fan of the aileron trim systems in RV's, just switch fuel tanks.
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Why are you not a fan of it and what if there is a wing heavy, which is more common than not.
Just to get my 2 cents, considering how little work or money it takes, I would certainly recommend it.
 
Bavafa said:
Why are you not a fan of it and what if there is a wing heavy, which is more common than not.
Just to get my 2 cents, considering how little work or money it takes, I would certainly recommend it.
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Fix a heavy wing with proper rigging, don’t compensate an out of rig airplane by using trim. Autopilot will hold normal wing imbalance, use fuel to keep the wings balanced.
 
Walt said:
Fix a heavy wing with proper rigging, don’t compensate an out of rig airplane by using trim. Autopilot will hold normal wing imbalance, use fuel to keep the wings balanced.
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I must very respectfully disagree with Walt. And I do this with a great degree of caution, because Walt's postings on VAF are clearly among the best.

Almost every airplane I have flown has had trim in all three axes, pitch, roll, and yaw.

The Boeing trim procedure when I was flying their products was as follows, (as best as I can remember...)

Once reaching cruise altitude, engage autopilot in Heading Mode. Let things settle down.

If the wings are not exactly level, use the RUDDER TRIM to get the wings to be Level. Yes, Rudder Trim. (Remember, the autopilot is engaged, and is holding a steady Heading.)

Then disconnect the autopilot, and hand-fly the aircraft, noting if there is a heavy wing. Use aileron trim to trim out the forces so that the plane flies hands-off. Re-engage autopilot.

It took me a while to get my head around this procedure...... It is designed to minimize "trim drag" on long flights, thereby saving fuel, in some cases saving enough fuel to complete the flight without having to divert.

Walt is certainly correct when he states that correct rigging will solve the problem. However, "correct rigging" is very difficult to achieve in the end. There's always a little something that isn't just right.

If Boeing can't get "correct rigging" exactly right, I probably can't either!

[Flame Suit On!...]
 
RVs have matured significantly over the years.
When I went to set the incidence on my slow build RV10 the tooling holes on the rear spar and rear spar carry through lined up perfectly.
Put a #30 cleco through them all and measured everything.
Needless to say it was pretty much spot on.
When you couple this with the riveted trailing edge design, it’s very hard to have a 10 or 14 that has a “rigging” issue or incorrect TE shape issue causing an out of trim condition.
However…
I rarely used the aileron trim on my RV7 therefore only put pitch trim on the stick - and aileron on the center console. Big mistake. When I put ER tanks on the 10 even bigger mistake!

In the interest of efficiency on long flights I do actually mostly ignore my tank change alert on the EFIS and look at the trim indicator every time it goes off (5gal -about every 30min) and do as Walt says and burn to keep the trim as close to the middle as possible, but it is highly dependent on airplane loading and speed (VS offset and ball position etc) and doesn’t always work. Inattention to tank switching can easily overcome the roll trim limits.

In short the 10 and 10ER would be a massive PITA to fly generally without aileron trim and I imagine the OPs 14 would be similar.
I’ll eventually refit a coolie hat to the stick.
 
Richard Connell said:
In short the 10 and 10ER would be a massive PITA to fly generally without aileron trim and I imagine the OPs 14 would be similar.
I’ll eventually refit a coolie hat to the stick.
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Aileron trim also is a major boon in my 9A. If you had to keep the wings level only through switching tanks, you’d be switching tanks every X minutes, where X is a very small number that would be impossible to know beforehand and that would change on every flight depending on what was in your luggage and where you put your soda. 🤣
 
Let me just say that I suggest you remove the spring bias during your initial flt testing, get the airplane rigged, then decide for yourself.
How do know the airplane really is balanced with a permanent spring bias being applied to the the ailerons?
Control forces are so light in the RV that unless you have a huge fuel imbalance I can’t imagine why y’all seem to have so much trouble. Long range tanks, tip tanks etc. of course will cause more trim problems, personally I’m not a fan of those mods, especially those that move the fuel outboard in larger main tanks.
When I’m cross country I’m usually on autopilot anyway and the servos have no issues keeping wings level, I have my fuel alarm set to 30min but that’s not at all critical, just good practice. With a 5gal imbalance and hands off the airplane will SLOWLY start to bank, almost no pressure on the stick to keep wings level.
I also prefer not constantly fighting spring bias on my nice controls. I do understand that the larger birds like the 10/14 are not quite as nimble as the rest of the fleet but I still think the same principles apply.
https://www.vansaircraft.com/faq-technical-builder-items/how-to-diagnose-and-fix-a-heavy-wing/
 
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Walt said:
Fix a heavy wing with proper rigging, don’t compensate an out of rig airplane by using trim. Autopilot will hold normal wing imbalance, use fuel to keep the wings balanced.
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How would you go about fixing a heaving wing when the plane is rigged correctly and per instructions and yet there is wing heavy? There is no bend trailing edge in a 14 to squeeze or unsqueeze. The aileron hinge points are a fixed points and VANS says "wing heavy is a luck of a draw"

To be fair and since I have looked into it, my info points to a twist in the flap/aileron but VANS allows up to 3 degree twist so they don't consider it an issue on their QB.

The issue to rely on the A/P to keep it balanced is that as soon as you disconnect the A/P, you are faced with an untrimmed plane. My question is why rely on the A/P to keep the imbalance when there is a simple solution to it unless there is a drawback in the electric trim that you are aware of it.
 
Bavafa said:
How would you go about fixing a heaving wing when the plane is rigged correctly and per instructions and yet there is wing heavy? There is no bend trailing edge in a 14 to squeeze or unsqueeze. The aileron hinge points are a fixed points and VANS says "wing heavy is a luck of a draw"
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The last paragraph in the link in Walt's post provides the answer:

"The final solution for all models, if all else fails, is to simply add a trim tab. All of the construction manuals for the aircraft detail a wedge type trim tab that does not affect appearances too much."​
 
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As you know, the RV14, like the 6, 7, 10, and 12 are side by side seating. Passengers or the lack have a large impact on roll trim. My wife is not my same weight. It is nice to trim that difference out. If your passenger is a similar weight or you have trimmed out the difference, then fuel balancing is all that is needed.
 
I have spent my career flying jets with roll trim. I have always counseled my right seaters NOT to use aileron trim as it is hiding something else, most likely a fuel imbalance.

My -10 has neither rudder or aileron trim and I do not feel the need for either. With standard tanks, there is very little roll pressure and two large folks on one side or the other is easily compensated for by using fuel from that side first. I agree with Walt, rig it properly and then manage fuel, don’t hide an imbalance.
 
Wrong ideas…..

Installation of a roll trim system should not be done to resolve actual trim issues.
I agree that those should be dealt with by making rigging adjustments or adding a trim tab. A balanced airplane should fly in trim without any other input.

I disagree that a trim system shouldn’t be used for balancing out influences that are a variable, such as different loading in the aircraft or fuel imbalance.
Sure, fuel can be managed to try and keep the airplane in trim, but it is impractical to switch fuel tanks every 10 minutes.

The very first few gallons burned off of a tank have the biggest influence on role trim because they are the furthest outboard in the tank, so have the highest roll moment.

Having a system to trim out this variability in roll trim makes sense.
Using a roll trim system is not hiding any issue. It is dealing with an issue that is fully expected.
 
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