C172 always banks to the left

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Hook
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Re: C172 always banks to the left

Post by Hook »

caliban,

Did you try flying with a perfectly symmetrical load? Same amount of fuel in each tank (full is best) and same weight pilot and right seat passenger? Also, use the 172R prop and set RPM to 2100. If you're still getting banking during cruise flight in this condition, there's something else wrong.

You can test for joystick miscalibration by unplugging it and flying with the keyboard for a bit. If it still banks left with the joystick unplugged and the controls centered (use the 5 key on the num pad), we'll have to look deeper.

Give these a try and let us know what happens. Don't unplug the joystick until you've done the balanced load test. I'd suggest going through the joystick calibration routine before you try unplugging it to see if it helps.

Hook

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AKar
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Re: C172 always banks to the left

Post by AKar »

caliban wrote:As it seems to be not a problem for some but a chronic one for others,
Yes, that's what puzzles me, as it leaves two possibilities:
- The plane is the same for everyone, but folks perceive the banking differently, perhaps due to different expectations and different controllers, or fly it differently (power settings, loadings etc);
- There actually is an issue with sim dynamics or controller behavior with some installations.

I'd like to do some tests just to have numerical figures of how my installation handles in different phases of flight, and to give one user's idea what he thinks very normal and believable. But unfortunately I've been rather busy with work, and will be over the weekend most likely.

I point out that I do have some banking tendencies in most situations, but nothing that I would consider suspicious when thinking of realism.


By the way, does anyone know of good "FDR", or parametric recorder for FSX? I'm not necessarily looking for one with full replay capability, as they often have problems with advanced addons, but a similar module just recording pitch, bank, yaw, hdg, alt, pos, etc for review? Like a black box for FSX. :)

L.A. wrote:P.S. -- if the rigging is bad, such as an old Cessna 172 I flew across country, after getting it's windscreen knocked out by a bird, and replaced...............then it's a constant fight, with the controls. This plane yawed badly, and required constant foot pressure.
These repaired planes can be quite interesting cases indeed. Some fly perfectly after some serious repairs, but others may act weirdly, and require abnormal trimming with seemingly insignificant work done on them. I know a few fine examples.. Anyways, usually they are not rigging problems per se, as the rigging is done to mechanically adjust the controls to neutral and for correct travel, usually not to balance the aircraft aerodynamically after it's bent, beaten and patched up. I'd call it airframe problem, not a rigging problem, it the control surface neutrals and travels are measured to specification. Though of course airframe damage might affect it's rigging too.


-Esa

caliban
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Re: C172 always banks to the left

Post by caliban »

Hook and AKar,

I have just flown with symetrical loading,swapped props supplied and with joystick and with keys only-yawing is in all cases.
Usually,I fly with an asymetric load of fuel/body weight to right and this helps to at least make the Cessna controllable via the joystick.
I use the Cessna in the UK flying out of Wolverhampton.Once established I turn on the A/P until it is time to get ready for landing at destination.
I have the A2A Cub-a very different craft,I know,but it flies S&L as does my 2 other add-ons from Realair.
Interestingly,I have no problems with the general aviation defaults except for the default Cessna which I can establish S&L sometimes and at others not at all despite the parameters looking ok.

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Lewis - A2A
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Re: C172 always banks to the left

Post by Lewis - A2A »

I believe the Accu-sim C172 Trainer is the only simulation for MSFS to simulate these forces which is why you wont get them on any of add-ons or default aircraft.

thanks,
Lewis
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renaissanceman
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Re: C172 always banks to the left

Post by renaissanceman »

Hi caliban,

Sounds like you have eliminated many of the usual problems with the banking tendency - good troubleshooting. I have a two suggestions you may not have tried yet:

1. Rename the C172RLog.dat file C172RLog.bak. This file is normally found in My Documents\A2A\FSX\Cessna172. Restart FSX and you will have a factory fresh C-172. Go flying, see if the left banking tendency is still apparent.

2. When a flight is saved, most of the flight data are included in an .FLT file such as A2A C172.FLT. These files, by default, are located in My Documents\Flight Simulator X Files. While in FSX, save a flight with the C-172 loaded and remember the name you give it. Locate the file and open it with Notepad. Search (Control+F in Notepad) for AileronTrimPct. In mine it is located in the [Controls.0] section and looks like this:

[Controls.0]
SpoilersHandle=000.00
FlapsHandle=000.00
LeftFlap=000.00
RightFlap=000.00
GearsHandle=000.00
Gear1=100.00
Gear2=100.00
Gear3=100.00
YokeY=050.00
YokeX=050.00
Rudder=049.99
LeftBrake=100.00
RightBrake=100.00
ParkingBrake=100.00
ElevatorTrim=050.00
RudderTrimPct=0
AileronTrimPct=0

If AileronTrimPct does not equal 0, then I would say the problem is aileron trim. You can edit this number to 0, save the file and reload the flight to see if it helps. RudderTrimPct should also equal 0.

Or, like me, you can assign aileron and rudder trim to your joystick buttons or hat and and trim while in flight. I know, I know, most real C-172s do not have aileron or rudder trim. For me this makes hand flying much more enjoyable.

Let us know if this helps.

Jim
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caliban
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Re: C172 always banks to the left

Post by caliban »

Rennaisanceman,
I have this morning been able to effect your suggestions but with no luck.I have renamed the C172Rlog.dat file,looked at a saved Cessna FL folder in which the aileron and rudder trim was set at 0 for both.I did assign some buttons on the joystick for aileron trim and this seemed to give me more control over the left tendency but it is still apparent that this is the way the craft wants to go.
Such is life!!

Gabe777
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Re: C172 always banks to the left

Post by Gabe777 »

Hook wrote:A constant turning tendency during cruise (in either direction) in a flight simulator can be a considerable annoyance.

So how do we deal with it? One way is to proclaim loud and long that it's a flaw in the flight model and demand the developer fix it. Another way is to assume the flight model is reasonably correct and compensate for it during flight. Most flight simmers are not going to like holding a constant control correction. But that's not the only way to compensate.

I've found over the years that almost all flight sim aircraft will exhibit some turning behavior if the load is not balanced. I've also found that even a half degree of AoA in cruise will cause a bit of left turning tendency on a balanced aircraft. Running at higher power will also cause a left turning tendency, and lower power will cause the aircraft to want to turn right.

The problem in FSX isn't bank, it's yaw. If the aircraft is yawing, it will also want to bank, caused by yaw-roll coupling in the .air file. As far as I know, this is correct behavior. Changing the power causes yaw, which causes bank which results in a turning tendency. During climb, you'll need to use right rudder to counteract the yaw, and during descent you use left rudder. During cruise, you may need to adjust the power slightly. In MS Flight in the Stearman, I was able to totally neutralize the yaw (and turning tendency) in cruise solely by adjusting the power.

An asymmetrical side load will cause some banking (rather than yaw) resulting in a turning tendency. How do you balance an asymmetrical load? Burn fuel from the heavy wing. No matter what you're flying, if it has a tank in each wing, you can cancel out any turning tendency by burning fuel from one tank until the aircraft is stable. In the A2A C172, if you have a pilot but no passenger, you have an asymmetrical load. I've successfully used this method for years in flight sims. Adjusting the power to compensate for an asymmetrical load usually doesn't help much.

Another way to stabilize the plane, whether the cause is power or loading, is by using rudder trim. While the A2A C172 doesn't have a rudder trim tab, it IS modeled in the aircraft and can be set by the keyboard. The actual aircraft has a small aluminum tab on the bottom of the rudder that can be set by bending it on the ground, so using some rudder trim is not a cheat of any kind.

I typically fly the A2A C172 with a 270 pound pilot, no passengers, and 5 clicks of right rudder trim. Any residual turning tendency is removed by burning fuel from one tank until the aircraft is balanced. If I'm flying with passengers, I obviously need to balance the fuel load a bit. Before I discovered the trim tab, I did all my balancing during flight by burning fuel from one tank until the aircraft was balanced.

Please note that the A2A C172 does NOT always use the same amount of fuel from each tank with the fuel selector set on Both. Also, you may find that if you don't set the fuel selector to Right or Left when you leave the aircraft parked, there will be some cross-feed between tanks and your fuel load won't be the same as when you left the plane.

As far as I'm concerned, the A2A C172 models asymmetrical loads and power induced yaw correctly. I have no problems compensating for the "always banks to the left" problem.

So here's the deal. Either always fly with a perfectly balanced load (which will change during flight because of the asymmetrical fuel use) and proper cruise power (2100 RPM for the C172R), or use a combination of rudder trim and burning fuel from the heavy wing until the aircraft is properly balanced.

Hook

PS. XPlane seems to have a different problem, so this may not work for that sim. If it does, let me know.

H.
Wow, that taught mè stuff I never knew ! Thnx.

I have never usef rudder pedals, being a peasant, so I've never really got that much into the intricacies of such flight dynamics.

But, if I only have a pilot on board and have calm sir, no wind st all, in cruise at around 4000ft, at around 75% Mzp, doing 100 knots, my plane is showing a degree of right roll. It is only tiny, neefing left roll corrections every 20 seconds.

BUT: my auto rudder is switched on ! So, I'm guessing that this simple fact could me messing it all up anyway ? So, maybe I should come back when I grt some rudder pedals ?
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Oracle427
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Re: C172 always banks to the left

Post by Oracle427 »

IRL, if I can take my hands off the controls on the 172 or 182 for more than 10 seconds that is a very calm day. I would consider your behavior to be perfectly normal.
Flight Simmer since 1983. PP ASEL IR Tailwheel
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