Why no aileron trim?

40YearDream

40YearDream

Pre-takeoff checklist
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40YearDream
In the process of learning instrument flight, I've found that (for our club Cardinal) I need to hold the yoke with a hand resting on my knee. Otherwise, the thing wants to roll / turn right (when futzing with GPS, radio, reviewing a plate, etc.) Pretty much every 1960s - 1970s vintage airplane I've flown seems to want to turn one way or another, after getting the elevator trimmed (with maybe 1 exception).
Why didn't Cessna (or Piper) allow for aileron trim, in these trainers? Is having to constantly hold some input a part of the learning process? Or, are these aircraft just not properly maintained / rigged?
 
I'd guess there are rigging issues, though fuel (and crew!) imbalance can have a noticeable effect in all of these.
 
40YearDream said:
In the process of learning instrument flight, I've found that (for our club Cardinal) I need to hold the yoke with a hand resting on my knee. Otherwise, the thing wants to roll / turn right (when futzing with GPS, radio, reviewing a plate, etc.) Pretty much every 1960s - 1970s vintage airplane I've flown seems to want to turn one way or another, after getting the elevator trimmed (with maybe 1 exception).
Why didn't Cessna (or Piper) allow for aileron trim, in these trainers? Is having to constantly hold some input a part of the learning process? Or, are these aircraft just not properly maintained / rigged?
Click to expand...

In many GA singles the manufactures included rudder trim for that.
 
(Note - I have a total of 1.1 hours on one flight in the Cardinal.)

An airplane should fly reasonably straight with hands off the controls when trimmed up properly. Eventually it will likely enter a turn one way or the other, but it shouldn't be a constant control pressure to keep it straight. Some possibilities:
- Rudder trim - set correctly? Too much right rudder trim would also cause the plane to roll right.
- If no rudder trim, are you just using too much right rudder even in level flight?
- Fuel imbalance? If the left tank is feeding more than the right tank, that would cause the right wing to be heavier and start a roll.
- And last, of course, rigging. If all the above is okay, then it likely just comes down to rigging, which you may have to convince your school to fix (too much of "it's always been that way, I've never had a problem...")
 
40YearDream said:
Or, are these aircraft just not properly maintained / rigged?
Click to expand...
Maybe. Or it could be you simply have a heavy wing. It all depends. I put flight control rigging and directional stability right up there with electrical system serviceability when it comes to the least maintained items on small aircraft. Seems owners will put up with regularly replacing batteries and flying with control input vs getting it fixed for whatever reason. As to secondary trim systems (vs trim tabs) they are not usually needed on most SE aircraft. And those that may need some trim help usually stick to rudder trim only.
 
How does your weight compare with your instructor's or safety pilot's weight? The arm is not long but an imbalance between the seats can affect the aileron trim. Even without any in-cockpit control of aileron trim, rest assured that the ailerons and flaps were, at some point in time, rigged with a goal of the plane flying straight and coordinated in cruise flight with some particular loading. If it is far off from that goal, then re-rigging may be in order. A less expensive option for needing constant left aileron is to gain some weight or ask your instructor/safety pilot to lose a few pounds.

Aileron trim comes in a couple of flavors, all of which are a compromise of some sort. The typical light single plane has the compromise of reduced complexity at the expense of simply not having a pilot-controllable aileron trim. Rudder trim does most of the job and the control forces are never that much to begin with. A trim tab adds a lot of complexity (and, for a small plane, a lot of expense relative to the total cost of the plane). A spring-type aileron trim also adds complexity and cost, although not as much, and these are more popular on newer planes. I think all Cirrus non-turbine aircraft use this method, as do many Van's RV kit planes and probably dozens of other types.

But the older singles just don't give you a control over aileron trim, because it wasn't an important enough feature to raise the complexity and cost of a new plane back when Piper and Cessna had these planes on the drawing board.
 
This can be if the aircraft is not rigged properly. At least on the C-182, each wing can be adjusted for angle of incident to rig this out.

But, as others mentioned, it could be due to fuel or people imbalance also.
 
Seems to me the Cardinal had a ground-adjustable trim tab on one aileron. The wing mounting on those airplanes has no incidence adjustments as do the strut-braced airplanes.

The rudder system in the Cessna singles is centered by the nosewheel steering, and mechanics often screw that up. The Service Manual for the airplane ALWAYS has the answers, and people who guess at what needs to be done, and that includes mechanics, just end up making things worse. Using rudder trim to counter a wing-heavy condition just results in the airplane skidding sideways (ball will be off-center) and the cruise speed suffers.

From the 177 manual:

upload_2022-12-5_10-0-33.png

upload_2022-12-5_10-0-54.png

upload_2022-12-5_10-2-36.png
 
I can't vouch for the Cessnas, but my Navion has both a bendable trim on the right aileron and the cessna-style tab on the back of the rudder.

A lot of the cessnas get adjusted for roll trim by slightly tweaking the flap resting positions.
 
Clip4 said:
In many GA singles the manufactures included rudder trim for that.
Click to expand...
See above. You don't want a skidding/crabbing airplane. The manufacturers who designed these things specify what needs to be done, and anything less is just dumb. I have fixed control systems, got them rigged properly, and the owners commented that they felt like brand-new airplanes, they flew so nice.

I'm always amazed at what some folks put up with.
 
flyingron said:
A lot of the cessnas get adjusted for roll trim by slightly tweaking the flap resting positions.
Click to expand...
And that is against all the service manual advice. It also causes a wing-drop in a stall and can induce a spin. The stall starts at the inboard trailing edge, and introducing asymmetry there is just asking for bad behavior.
 
RussR said:
(Note - I have a total of 1.1 hours on one flight in the Cardinal.)

An airplane should fly reasonably straight with hands off the controls when trimmed up properly. Eventually it will likely enter a turn one way or the other, but it shouldn't be a constant control pressure to keep it straight. Some possibilities:
- Rudder trim - set correctly? Too much right rudder trim would also cause the plane to roll right.
- If no rudder trim, are you just using too much right rudder even in level flight?
- Fuel imbalance? If the left tank is feeding more than the right tank, that would cause the right wing to be heavier and start a roll.
- And last, of course, rigging. If all the above is okay, then it likely just comes down to rigging, which you may have to convince your school to fix (too much of "it's always been that way, I've never had a problem...")
Click to expand...

Maybe the 1st thing is the main problem: the airplane does have rudder trim, but it's broken! [I should push for our club maintenance guy to get that fixed.]
Along with that, the fuel never draws perfectly evenly from both tanks.
 
iamtheari said:
How does your weight compare with your instructor's or safety pilot's weight? The arm is not long but an imbalance between the seats can affect the aileron trim. Even without any in-cockpit control of aileron trim, rest assured that the ailerons and flaps were, at some point in time, rigged with a goal of the plane flying straight and coordinated in cruise flight with some particular loading. If it is far off from that goal, then re-rigging may be in order. A less expensive option for needing constant left aileron is to gain some weight or ask your instructor/safety pilot to lose a few pounds.

Aileron trim comes in a couple of flavors, all of which are a compromise of some sort. The typical light single plane has the compromise of reduced complexity at the expense of simply not having a pilot-controllable aileron trim. Rudder trim does most of the job and the control forces are never that much to begin with. A trim tab adds a lot of complexity (and, for a small plane, a lot of expense relative to the total cost of the plane). A spring-type aileron trim also adds complexity and cost, although not as much, and these are more popular on newer planes. I think all Cirrus non-turbine aircraft use this method, as do many Van's RV kit planes and probably dozens of other types.

But the older singles just don't give you a control over aileron trim, because it wasn't an important enough feature to raise the complexity and cost of a new plane back when Piper and Cessna had these planes on the drawing board.
Click to expand...


BRB, going to tell the safety pilot (wife) she needs to lose a few pounds, will report back findings . . . :)
 
SoonerAviator said:
BRB, going to tell the safety pilot (wife) she needs to lose a few pounds, will report back findings . . . :)
Click to expand...
Okay, I knew someone would bring that up. It's an exception to the rule. Asking your wife to lose a few pounds "for W&B purposes" is not the less expensive option. Forming a company to R&D an STC to add an aileron trim system to the Cardinal is a better use of your time and money than that conversation.
 
40YearDream said:
Maybe the 1st thing is the main problem: the airplane does have rudder trim, but it's broken! [I should push for our club maintenance guy to get that fixed.]
Along with that, the fuel never draws perfectly evenly from both tanks.
Click to expand...

Ask yourself (and them) if it's even legal to fly an aircraft with a known deficiency in the secondary flight controls.
 
RussR said:
Ask yourself (and them) if it's even legal to fly an aircraft with a known deficiency in the secondary flight controls.
Click to expand...

...while filling out a NASA ASRS form after having now admitted flying such a deficient plane on a public forum? :)
 
iamtheari said:
Asking your wife to lose a few pounds "for W&B purposes" is not the less expensive option. Forming a company to R&D an STC to add an aileron trim system to the Cardinal is a better use of your time and money than that conversation.
Click to expand...

Also consider the hospital stay and the follow up medical forms after she puts multiple pot knots on your head faster than you can wipe them off ... ;)
 
Fearless Tower said:
In most cases that is the problem.

Usually don’t see adjustable aileron trim until you start getting into twins
Click to expand...
Cessna's Columbia/Corvalis/ttX/350/400 had it. Electric trim.
 
I've wondered the same. Even in well rigged planes your fuel burn, loading, etc aren't going to always be identical. I never liked using rudder trim as a solution. The idea of flying in a perpetual skid is bothersome
 
Dan Thomas said:
See above. You don't want a skidding/crabbing airplane. The manufacturers who designed these things specify what needs to be done, and anything less is just dumb. I have fixed control systems, got them rigged properly, and the owners commented that they felt like brand-new airplanes, they flew so nice.

I'm always amazed at what some folks put up with.
Click to expand...

I am always amazed with folks who demand unneeded repairs on club aircraft. Before you run off demanding the rig be checked on a club airplane, check the inclinometer and see if the ball is centered. Clubs are prone to have members who were taught rudder trim is for the purpose of reducing right rudder on takeoff and the rudder trim is screwed up.
 
What are the legalities of adding a bendable trim tab to a standard (non experimental) airplane that didn't originally have one?
 
Dana said:
What are the legalities of adding a bendable trim tab to a standard (non experimental) airplane that didn't originally have one?
Click to expand...

Can be done with appropriate paperwork (STC or Field Approval)

1948 Cessna 170s that had aftermarket metalized wings have ground adjustable metal trim tabs added because once you metalize the original fabric covered wings, you no longer have the ability to adjust the internal rigging.
 
My plane has aileron trim and it makes me wonder what they tried to paper over by installing it. Can't wait to remove it.
 
Mine tracks fine without aileron trim. Now we had a school Cherokee that banked hard if you released the yoke, but the mechanics were able to adjust that out.

D657FAF3-9DB0-4ABB-A28D-FE6AA07802A4.jpeg
 
40YearDream said:
In the process of learning instrument flight, I've found that (for our club Cardinal) I need to hold the yoke with a hand resting on my knee. Otherwise, the thing wants to roll / turn right (when futzing with GPS, radio, reviewing a plate, etc.) Pretty much every 1960s - 1970s vintage airplane I've flown seems to want to turn one way or another, after getting the elevator trimmed (with maybe 1 exception).
Why didn't Cessna (or Piper) allow for aileron trim, in these trainers? Is having to constantly hold some input a part of the learning process? Or, are these aircraft just not properly maintained / rigged?
Click to expand...
My guess is it's not properly rigged.
 
Clip4 said:
I am always amazed with folks who demand unneeded repairs on club aircraft. Before you run off demanding the rig be checked on a club airplane, check the inclinometer and see if the ball is centered. Clubs are prone to have members who were taught rudder trim is for the purpose of reducing right rudder on takeoff and the rudder trim is screwed up.
Click to expand...
Any airplane that needs the wheel held to the left lest it bank right, and has a broken rudder trim (as per OP), need fixing.

Period.

There is a well-established procedure to find out what's misrigged. Hold the ball centered with the rudder, let go of the wheel, and see if the airplane banks. If it does, the wings, or the aileron tab, are off. Then hold the airplane level with the wheel and let the rudders go, and see if the ball is off-center. If it is, the rudder rigging, or its trim tab or trim system is off. This assumes that the turn coordinator is level in the panel. The screws run through slots so that the instrument can be adjusted to center the ball when the aircraft is level as per a level placed across the seat rails.

This isn't rocket science, yet it totally escapes some people.
 
#%$#%&* Gad! A Cessna 172 in Maryland Wing of CAP was the worst example of mis-rigging I've ever encountered. It was impossible to hold heading wings level. Not difficult. Not hard - it was just not gonna happen. During an annual check ride the check pilot was bitchin' about me holding heading under the hood - I told HIM to take the controls for a few minutes. "Oh. Yeah." I think it took a MAJOR amount of rudder to keep it on heading.

Writing it up had no effect - "It's fine for day VFR." Eventually a person with influence got stuck with it. To be fair the other aircraft were usually in decent shape - but this pig was at Wing HQ where the inner circle had access to glass 182s and and an Airvan; the unwashed flew the 172 so I guess it was "orphaned."
 
Sundancer said:
#%$#%&* Gad! A Cessna 172 in Maryland Wing of CAP was the worst example of mis-rigging I've ever encountered....I think it took a MAJOR amount of rudder to keep it on heading.
Click to expand...
Typical symptom of a broken rudder bar spring, usually the left one, since it gets stretched more often (takeoff and climb rudder) with right rudder being held. That means that one has to hold left rudder all the time in cruise.

With nosewheel centered, stand beside the airplane, reach in and pull one of the rudder pedals toward you. Then pull the other. They should feel about the same and should pop back when released. A broken spring will leave one very soft.
 
I spent several AMUs to have a A&P well known for my type of plane come out and correct my rigging. It was the best money I spent on my airplane. First and foremost he looked at the accident history of the airplane and measured everything with a laser level and checked to see if the fuselage, tail or wings were tweaked. Then he took the planes rigging to stock and adjusted cable tensions to within limits. It was only after that that we adjusted the wing root adjustment to get the plane juuust perfect. It was better money spent than an autopilot and I gained 5-7mph.
 
Mtns2Skies said:
I spent several AMUs to have a A&P well known for my type of plane come out and correct my rigging. It was the best money I spent on my airplane. First and foremost he looked at the accident history of the airplane and measured everything with a laser level and checked to see if the fuselage, tail or wings were tweaked. Then he took the planes rigging to stock and adjusted cable tensions to within limits. It was only after that that we adjusted the wing root adjustment to get the plane juuust perfect. It was better money spent than an autopilot and I gained 5-7mph.
Click to expand...
The flap and aileron cable tensions should be set after the wing incidence is adjusted. Cessna uses eccentric bushings in the aft spar carrythrough to adjust incidence, and those eccentrics not only move the trailing edge up and down, they move it in and out. If the TE ends up more inboard than it was, the cables will be slack. If outward, they get too tight. Only if the eccentric is moved from full up or down to the opposite will the cable tensions remain the same.

I also found that the 180 and 185 had a design flaw: the aileron cable tensions vary with elevator position. Cessna didn't get the yoke pivot/aileron cable pulley locations just right. IIRC, pulling back on the elevator lowered the aileron cable tension. I used to block the elevator in a neutral position when rigging the ailerons.

Gaining 5-7 MPH is an indication that things were a long way off, alright. Typical of too many legacy airplanes.
 
Dan Thomas said:
Typical symptom of a broken rudder bar spring, usually the left one, since it gets stretched more often (takeoff and climb rudder) with right rudder being held. That means that one has to hold left rudder all the time in cruise.

With nosewheel centered, stand beside the airplane, reach in and pull one of the rudder pedals toward you. Then pull the other. They should feel about the same and should pop back when released. A broken spring will leave one very soft.
Click to expand...
This was a few years back - I'm several states away and left CAP in 2014. . .but good to know, thanks.
 
First question - did Cardinals ever have a wing leveler?

Ours died so we started playing with proper rigging. A lot of money to fix the TC (failure point for the single axis). About 1hr or labor - twice for the rigging. But it now it easily flies hand free for 15 minutes at a time or until someone moves around. I thought it would only fly hands free with just one pilot passenger combo but it flies hand free with just me or both of us or if we've switch seats so dig that part. As other have said its all about the rudder trim first though. Love the rudder trim.
 
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