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Brief description of the issue:
Aileron and Rudder Trim not working correctly. They seem to have a problem with CONTROL vs RIGHT CONTROL and sometimes work to move surfaces as observed staticly on the ground. Their effect in the air is unpredictable, sometimes causing violent roll. It could be a problem with key binding as I have tried changing CONTROL to RIGHT CONTROL in the key binding to try to work around the problem. Quite often when getting one to work (sort of) the other would quit (aileron vs rudder). I am using a Saitek Pro Flight Yoke programmed with the key bindings. I have also used the key bindings manually from the keyboard and the yoke is not the source of the problem as inputting the key commands from the keyboard yield the same behavior as the yoke.
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I first noticed the problem in the Climb and Descent and the VOR Basics lessons under IFR Navigation in the Flight Training option. Both these lessons use the Cessna 172 (G1000) aircraft. The aileron and rudder trim controls kept requiring me to be constantly correcting for heading drift. I recalibrated the yoke and rudder pedals to hopefully remove the drift, but the constant drift persisted. I perhaps too quickly jumped to observing control surface movement on the ground outside the aircraft. While pitch trim would move the small trim tab on the elevator, I could not discern any movement of either the ailerons or rudder in response to their trim controls. I expected both of these surfaces to be offset or deflected by the trimmed amount when both yoke roll and rudder were in their neutral or center positions. But I could not observe that effect. When they weren’t, I then questioned if I was indeed really entering any trim at all and suspected the keyboard mapping, ergo my post. However, after retesting the aileron and rudder trim while flying in the Cessna 172 (G1000), the Cessna 152, and the G36 Beechcraft Bonanza, their behavior does indeed seem to be correct. Long story short, I have since come to the conclusion that while trim appears not to be modelled on the ailerons and rudder in the external view of the plane on the ground, they do indeed work correctly in the air. That leaves the question of the heading drift unanswered, but that is another story entirely.
In short, I would like to apologize to the Flight Sim Community for my error and would request that my post be deleted or at least marked as resolved. Thank you for your understanding.
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I have looked at the trim tabs on both the elevators and ailerons
on the C172 G1000 and the Cessna CJ4.
They move exactly as the trim is increased or decreased.
Are you looking at the trim tabs themselves.
CJ4 Elevator Trim tab all the way down.
I agree with you about the elevator tabs. But I cannot see tabs on either the ailerons or the rudder for either the C172 G1000 or CJ4. I do see the ailerons and rudders move when commanded by NUM4/ NUM6 (ailerons) and NUM0/NUM ENTER (rudder). These are the commands that you would use if you were flying via the keyboard.
However, the key commands for Aileron trim (CTRL+NUM4/CTRL+NUM6) produce no movement of the ailerons on either plane. Likewise the key commands for Rudder trim (CTRL+NUM0/CTRL+NUM Enter) produce no movement for the rudder.
It is my theory that lacking tabs both the aileron and rudder accommodate trim adjustments by adding the trim position to whatever position is currently commanded by the yoke or rudder pedals. For example, if the aileron is being commanded up 5 degrees by the yoke being turned right and the aileron trim is -1 degree, then the position of the aileron is up by 4 degrees. If the yoke were then rotated back to the “neutral” position, then the aileron would be at -1 degree. Thus the trim is just an “offset” to the commanded position. Unfortunately, the sim doesn’t show this relationship.
I am not a real life pilot and don’t know whether the C172 and the CJ4 have trim surfaces on the rudder and ailerons. If they do, then those are not shown in MSFS. If they do not, then the addition of the trim as biases to the control surface makes sense. But the movement of the control surfaces due to trim is not shown in MSFS either. It seems to me that either one or the other has to be the way it really works. At any rate, MSFS seems to have gotten the math correct for the desired effect.
Just for background I am a real life retired avionics systems design engineer. I have performed both detailed electronic design and written software for display systems.
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You are correct.
Looking at the CJ4, there are 3 Trim Tabs.
1 - Elevator
2 - Rudder
3 - Aileron
All 3 work from the cockpit controls.
Only the Elevator works from the keyboard.
The Rudder and Aileron do not work from the keyboard.
Note:
The Aileron trim tab appears to be on the right wing only.
I never see any movement on the left wing.
Note:
The Aileron and Rudder trim tabs are mapped in my default Keyboard Profile.
They just do not work.
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Thank you very much MSFSRonS. I was not familiar with the CJ4 but you are correct about all 3 trim tabs. I also found a reference on the web to the CJ4 having an aileron trim tab only on the right wing so what you said was spot on. I exercised the in cockpit trim controls and confirmed the movement on all 3 trim surfaces in external view. I also confirmed that there was no effect on the trim surfaces when using the key bindings that you showed in your reply; mine are mapped identically to yours. But I also noticed three entries under Control Trimming Surfaces to which I assigned key bindings as follows:
Toggle Aileron Trim = RIGHT CTRL + RIGHT ALT + NUM1
Toggle Rudder Trim = RIGHT CTRL + RIGHT ALT + NUM2
Toggle Elevator Trim = RIGHT CTRL + RIGHT ALT + NUM3
I then executed Toggle Aileron Trim and Toggle Rudder Trim per the above and was able to move both trims with the key commands that you listed. and when only CTRL is listed, it refers to the left CTRL key.
The same applied to my G36 Beechcraft Bonanza. The Bonanza has no tabs on the wing for aileron trim nor any tabs on the rudder or vertical stabilizer for rudder trim. While the cockpit does provide for aileron trim, the Bonanza does not have any cockpit control for Rudder Trim, yet the rudder and aileron still respond as I described in my previous reply for trim effected not by trim tabs, but by offset. Of course I must first Toggle the trim commands “ON” per the above paragraph.
For my C172 G1000, while in real life it only has “bendable” tabs for aileron roll adjustment and rudder trim that must be adjusted on the ground, it none the less responds to the key bindings that you showed for aileron and rudder trim but the respective surfaces observed on the plane in the sim do not move at all. Of course one can always choose to not use them while flying the C172 and C152.
The conclusion is that each of these aircraft behave slightly differently but in resolvable and predictable ways.
My many thanks for all of your efforts. I have learned a lot from you and it has opened my eyes to better methods of troubleshooting. Happy flying!
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