1969 Cherokee 140B Rudder trim indicator

RonP

Pre-takeoff checklist
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Jan 6, 2019
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RvP
The indicator showing where the rudder trim is set on my ‘69 Cherokee 140B is a thin flat bar inside the panel. It is really hard to see where the trim is at in day light and impossible at night. This makes it hard to set to neutral trim prior to taking off. Was there an external indicator? Anyone else have a solution to making the trim indicator easy to read?
 
Get some white nail polish and give the needle a couple of coats. The only time I have ever moved mine is when I’m lubing pulleys at annual time so I’m not sure why you need to see it prior to take-off.
 
Get some white nail polish and give the needle a couple of coats. The only time I have ever moved mine is when I’m lubing pulleys at annual time so I’m not sure why you need to see it prior to take-off.


The plane is at the airport so I can’t take a picture until the weekend. I adjust the rudder trim in the air to center the ball when cruising. My understanding is since there is no rudder trim tab the rudder trim is a bungee type of setup. As such it affects the nose wheel steering. I would prefer on takeoff the rudder input is to compensate for torque and not bungee. For example if during the flight I trimmed right rudder. If I don’t neutralize the rudder trim for takeoff I have to give left rudder to start roll out straight and then right rudder for torque. If the rudder trim was neutral then the start of the takeoff would be more straight with little rudder input until I have to compensate for torque. First am I correct the rudder trim is a bungee type of trim?
 
I leave the trim set for cruise and I’ve never really needed enough rudder trim on climb-out to mess with it—unlike say a C210 or C182. The only time I have ever used rudder trim in the Cherokee was when the right wing had full fuel and the left only 10 gallons. It’s just not something I’ve ever given much thought to. I’ll go up this week and pay attention to how the plane flies and see if I notice how rudder trim affects ground and flight operations.

The Cherokee does have a bungee setup although it’s not bungee like bungee cords.

Screen Shot 2022-05-23 at 4.29.50 PM.png Screen Shot 2022-05-23 at 4.30.53 PM.png
 
I've never played with rudder trim on any of the PA-28's I've flown. I probably should when using ones with an autopilot, as that's apparently the thing to do to have it flying straight. But that said, I've never noticed having to use any significant rudder in cruise on any of them, nor having the aircraft try to drift left or right when taxiing. And that's on maybe 8-10 different PA-28s flown? Maybe I'm just heavy on my feet and don't notice it. But maybe your aircraft is a little bit out of being rigged straight? That's a complete guess...but maybe worth flying/renting another PA-28 that is known to fly straight and see if yours is distinctly different? Again...a guess. I can fly the things, more or less, but tuning them up is NOT one of my skill sets.
 
I used to rent a Warrior and an Archer and they required a small amount of rudder trim to keep the ball centered during cruise. The Cherokee takes a lot more than I remember adjusting on the latter. Most of the time it is right rudder trim and when I am by myself. I weigh around 170 and I keep the fuel in both wing tanks balanced. Sometimes though it is left rudder trim to keep the ball centered. It could also be the airplane is not rigged properly after decades of flying. Regardless it would be nice to easily see where the trim indicator is. Centering the rudder trim before takeoff must not have been considered a critical item since it is not mentioned in the POH as something to set before takeoff as the POH notes to set the elevator trim for takeoff.
 
It's the same on my Cherokee. Really hard to see and I'm looking for a solution to make it more visible since I use rudder trim on every flight. But, yeah, to answer your question, it appears to be a Cherokee thing, not just the case on yours.
 
I use rudder trim in cruise a lot, particularly on longer flights. Not as diligently as stab trim, but it's relaxing to set trim, lounge back, get the feet off the pedals, and put one leg in the passenger wheel well.
 
The white fingernail polish is a good suggestion. You’re only painting the edge of what looks like a washer on the shaft of the trim barrel.
 
But maybe your aircraft is a little bit out of being rigged straight? That's a complete guess...but maybe worth flying/renting another PA-28 that is known to fly straight and see if yours is distinctly different? Again...a guess. I can fly the things, more or less, but tuning them up is NOT one of my skill sets.
I'm mostly a Cessna guy, but my wrenching experience has shown me, for many years, that out-of-rig is almost the default position of most airplanes. It is obvious to me that many mechanics make adjustments without referring to the service manuals, and so manage to screw everything up. Here's the thing: these systems are often not intuitive, and if you don't follow the manuals you end up adjusting the stuff that didn't need it, and failing to correct the stuff that did.

Aileron and rudder systems are commonly messed up. Flaps sometimes, too. Trims? Almost every airplane. Once in a while I'd find the elevator system so far off that the control column was striking either the panel or the firewall at the ends of its travels, liming the control surface movement.

Annual inspections are supposed to check this stuff, and it doesn't take long.
 
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