C172 always banks to the left

[AKar]

I actually had spare time today to fly a couple of one hour legs with the Cessna. Wohoo. I had minor differences in loading and fuel balance, of course. On the first flight, the plane wanted to roll to the left on climb, and was just about neutral on cruise. On the second leg, it was almost neutral at climb, but wanted to roll a bit to the right when leveled off.

If I load the aircraft just evenly on purpose (which I find highly unrealistic), it tends to roll to the left slightly on climb, much less so in cruise. During climb it requires some left foot to keep the ball centered, when accelerating to cruise speed I can smoothly relieve the pressure.

In worst case I've had (with some fuel imbalance with more go-go juice in the left wing), the amount of right aileron needed to keep the thing upright was perhaps around 5 % of total joystick travel, probably less. A very small input, though annoying of course with PC controller's centering detend.

Now, I wonder where comes from the assumption that the planes fly straight in real life - all the time? I mean, I assume that the team did some research on these things, and they are based on some documented behavior, right? Actually, the only other sim aircraft I currently use more is the NGX. It's quite interesting why it has simulated aileron and rudder trim. I've never used them, and still having perfect slip bar with 0.000 degrees of bank in straight flight. All the time. I see no one complaining in the appropriate forums that it's too perfect in loading, engine symmetry and airframe properties. Obviously I've never flown an actual -800 in real life, but often these trim controls happen to be displaced from zero during/after the flight in airliners too when I've checked them. Even in fighter jets. I wonder why.

Of course I can't say if this behavior in A2A C172 is exactly correct for all the Cessnas that fly in real skies. Academically, it would be interesting to know how the real Cessna handles when you let go the yoke during 80 kIAS climb - I try to arrange so I could test that myself one day this summer. I'm quite sure it won't go exactly straight. But I think it's safe to assume that the team did not model the banking tendencies out of some weird idea to annoy their customers. Actually, I'm not even caring very much if it's correct to the fourth decimal of delta-phi on an average C172R. I just find it refreshing in the flight sim world to have a GA aircraft that you actually need to fly and manage.

(Sorry about the rant, this just seems to pop out so often these days.. )

-Esa

[Lewis - A2A]

Forget it buddy. I tried talking to them, but for the devs here the left banking is realistic, despite some of us trying to talk every argument there is to prove otherwise.

You could check the topic I Created to discuss this,
http://a2asimulations.com/forum/viewtop ... 08&t=38785

There's a link on my last message there, that I sent to Scott, which is a very good insight on this matter regarding light single prop planes.
http://www.pprune.org/8354233-post13.html

It is realistic according to our hours of test flights, according to our high hour pilot and Instructor developers/testers, according to 2000+ hour C172 pilots etc etc. If you have other first hand experience in the C172R please do share your experiences.

[Alec246]

I don't have any C172R flight time, and it's something I always made clear. The only Cessna I fly is the little C152, with a very very weak 110HP engine. But I do fly two others with 160 and 180HP engine, and I believe planes have the same laws interacting regardless of the manufacturer.

I can get you videos, links from experts discussing the subject , e-mails exchanges with pilots with much more knowledge on this subject than me. If the A2A would show us the data on which it's based that a C172 does have left banking tendencies during flight, I would greatly appreciate it. Remember that it has to show that the ball is centered, the aircraft is being flown coordinated, or it's going to drop the wing, as it should.

Yaw is what comes in effect during a flight in a powered plane, not bank. I would NEVER slam power on a Merlin equipped P-51 during a go around, as I would certainly end up on the ground inverted, but a 180HP doesn't have that power at a critical low speed, high AOA. And we're talking speeds way above minimum control, and AoA way below that of a near stall.

I'm going to leave this post with this one video. If he's doing something, it's a slight constant left bank on the yoke.
https://www.youtube.com/watch?v=yKHdXTqGzVA

[Lewis - A2A]

Alex that video you have posted shows exactly what is modeled. the requirement for hand flying with an almost constant correction on the yoke depending upon power and a trillion other factors.

As stated and as noted in your own thread Alec by some pilots regarded as experts in there field its modeled correctly, theres not much we can do to show you otherwise.

thanks,
Lewis - A2A

[AKar]

Yaw is what comes in effect during a flight in a powered plane, not bank.

This wonders a bit off topic perhaps, but that's an interesting consideration. I haven't gone through the logic, so I say nothing this evening on how this applies to C172, but in case of classical jet airliner design (a low swept wing, with positive dihedral), the optimum trim in an asymmetrical situation is generally not zero side slip indication (which in case of a simple ball indicator equals to wings level in straight track flying). Instead, the trim is biased towards neutral aileron input as the neutral slip would require a much crossed control, that is, both aileron and rudder input.* That's why the Airbus aircraft automatically bias the side slip target on the PFD in case of an engine failure. so that the pilot intuitively seeks for the optimum side slip indication - not the zero one. The plane trimmed optimally, when it's asymmetrical aerodynamically, actually travels slighlty in a wing-low attitude with some side slip. But if you were just following the ball, the aircraft would travel wings level, with even more side slip and with considerable cross-control input.

Now, without any time in 172 but some in several gliders I feel that the ball simulation in FSX is rubbish. Perhaps not so much in higher airspeeds in directionally stable airplanes, but hypothetically I still wonder how much we chase the wrong targets.

Still I wish to argue that the main cause for perceived annoyance of this banking tendency comes from the fact how the PC controllers are centered.

(*Even more important point in airliners as if you got your aileron input beyond a certain degree, you would get a constant spoiler deployment on one wing - far from optimum!)

[Quickly edited as I mixed my angles and indications...]


-Esa

[Alec246]

Yes, the ball simulation in FS really is strange, I also think it's not showing us the true slip of the plane. As is yaw in many planes, it never seemed right.

Regarding these airliner, it's way beyond my knowledge, but I have read the same, in a multi engine aircraft, you fly with a slightly wing low during failure.

About the video. The amount of movement on the yoke is almost none, but if there is some, it's actually to the side the aircraft would be banking! To the left, not to the right, which would be countering this left banking tendency.

I don't have access to a C172R, neither do I have a GoPro, so there isn't much I can do to prove my point other than showing youtube videos and talking to pilots about this.

[Great Ozzie]

Now, I wonder where comes from the assumption that the planes fly straight in real life - all the time?

Because, imo, in Straight & Level flight, an aircraft should be able to fly "Hands Off" with little to no control input.

Hands off flying was something my initial instructor insisted on during my flight training. I also insisted on it as an instructor -- as it is a valuable skill, particularly when flying IMC.

Several of the aircraft I flew e.g. Warrior IIs, C172N had rudder trim (rarely used tho). So one might need a touch of rudder to keep the plane straight.

Over time e.g. cables become "slack", linkages "creep" / wear, control surfaces can become imbalanced... so flaps / ailerons can droop a bit for various reasons that can result in these turning tendencies.

But don't take my word for it. Rigging FAQs @ CessnaRigging.com

Still I wish to argue that the main cause for perceived annoyance of this banking tendency comes from the fact how the PC controllers are centered.

Could very well be the case. Especially from what I have seen Alec post (in the "other" thread).

In the sim, I don't worry about it so much. For one, I don't think the turn is "that bad". The other reason... the Frasca 141s I trained in during IFR simulation were terribly unstable -- required one to be exceptionally mindful of controls inputs. I felt this greatly enhanced IMC stick skills.

[L.A.]

While discussing this roll issue (actually regarding X-Plane) a few months ago.................I talked to a friend about this. We both built RV6s. His is a taildragger, and mine was a tri-gear. Much was being said, that high power engines contributed more to the torque roll. I knew that he had flown the Douglas Skyraider in Vietnam. This plane had the largest single engine horsepower of any U.S. propeller driven plane. It's a 2600 horsepower plane, with one prop. I specificaly asked, if he had to use aileron on the climb. He said "no, wrong control. You have to use rudder!" This pilot was also a flight instructor for many years.

I also brought this question up, on a RV builders forum. A pilot who owns and flies a turbine powered crop duster, said that torque and roll is actually a factor. And that I was wrong. A week later, he comes back, after testing it, due to our discussion, while flying...................and says any roll from torque is just inconsequental.

I also read the test reports on Austin Meyer's (the X-Plane author) turbine powered Lancair. These were from a different pilot, conducting test flights. He talked about "heavy wing", and making sure the plane flew level. There was nothing to do with torque. And like we did with the RVs, these builders go to great lengths, to make sure the wing incidence is exactly the same, on both sides. We make corrections, for heavy wing also. It can be right or left. We do prefer perfection in rigging. We don't expect the plane to remain on course and altitude, with hands off..................but we don't expect it to roll over to the side, either. Note: Lancairs and RVs have engine offset, to the right. Lots of other planes do too.

edit.................since we're on this subject, I was asking everyone, and their dog............about this subject, last year. I shared a hangar with two owners of a Pitt's M-12. It has a Russian radial, of about 400 horsepower. They said it's "yaw" on takeoff. Not roll. This plane has the prop going the other way. Takes left rudder, and lots of it. Another pilot, a few hangars down, flies small, but speedy racers in Reno. He also says it's "yaw". Same with some B-17 pilots I talked to. Their four engine bomber doesn't roll either.

[Hook]

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.

[AKar]

Because, imo, in Straight & Level flight, an aircraft should be able to fly "Hands Off" with little to no control input.

Hi Great Ozzie,

That I agree. (The emphasis is mine.) And I've been doing hands-off practices too, it's actually very nice 'test' for very low time pilots like me to check what kind of control pressures I'm actually applying, as when you concentrate for some time it's easy to squeeze the stick with knuckles white without noticing. I recall the only C150 I've flown from startup to shutdown required quite significant (from glider guy's perspective anyway - probably translates to 'perceptible') rudder input to keep the ball somewhat centered during climb, and I also needed to actively fly it to keep the heading I was told to hold. It needed some corrections in level flight too, but it's almost unnoticeable as you can "lock" the rudder pedal with your heel wedged against the floor and support your flying hand with your thigh.

I've never had any significant banking tendencies with A2A Cessna during straight & level flight at cruise power that are not explained by loading or fuel imbalance. I'm surprised if others had. There might be some, but it's perfectly stable in roll in one speed and power only for a single loading configuration. Yes, even that tiny bit of correction needed is rather annoying, as it's usually just 'over' my Warthog's centering detend. It's therefore very hard to keep constantly, but from software side it's nothing I wouldn't think is realistic. If we get a more advanced GA model one day with rudder and aileron trims, I'm actually expecting to see topics on how to trim properly on three axis as in most FSX products you simply don't have to.

Perhaps they could add a customizable rudder trim tab for us to fool around with (a'la certain Katana addon)?

Yes, the ball simulation in FS really is strange, I also think it's not showing us the true slip of the plane. As is yaw in many planes, it never seemed right.

Hi Alec,

I believe that the ball displacement is more or less directly proportional to the slip angle in FSX, though I got no idea of exact definition of slip angle in the sim. In reality, it's far more dynamic of course. As an extreme example, you could slowly and smoothly fly a helicopter sideways while having the ball perfectly in center, but in FSX I believe it would be displaced way to the side, if it's the same ball modeling that you find in the fixed wing aircraft.

[...]

Hi L.A.,

I'm not sure I'm getting you right, but I think that perhaps you are mistaking the aircraft rolling effect that's the subject here to be caused by simulation of engine torque primarily? I'd say the engine torque to be quite insignificant factor in these low-powered aircraft, as you say too. But instead, the power induced roll is created by combination of prop wash hitting the vertical stabilizer asymmetrically and P-factor (asymmetrically loaded propeller disk during high angle-of-attack flying) causing the plane to yaw left, which in turn induce left roll.

but we don't expect it to roll over to the side, either.

But they might do just that if you're not expecting. Slightly unrelated, but there was a case years back when PF, during the climb in ATR42, mistook that the autopilot was engaged on his command by PM, who was actually loading SID to the FMS. The plane flew uncontrolled for 28 seconds, according to report. During that time, the bank angle (left, btw) reached 35,5 degrees (over a degree per second, on average) and uncommanded turn led to heading error of over 80 degrees. Just to add here the only actual figures I quickly recall about hands-off banking in any aircraft. They need to be flown!

-Esa


(By the way, a reason why this is not only the best flight sim forum I know of, but also a top aviation forum too is that even these rather heated and never-ending issues that pop out every now and then with that initial 'not-again-feeling' on them, almost always remain patient and well informed. Of course there are good arguments for and against, and both 'noobs' and those who've flown in real life and in sims for decades, but the conversations remain remarkably free of flamethrowers, disrespectful comments and "please-lock-this-thread" kind of crap we see too much on many forums these days. Thanks to all posters for that - and especially to the A2A team members!)

[Hook]

Perhaps they could add a customizable rudder trim tab for us to fool around with

You mean like...

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.

Hook

[AKar]

Yes Hook, kind of. Though I would like to have a one which position is remembered and what could be set for taste in maintenance hangar or in other menu. I'm bit uncomfortable in using these default FSX functions which in a way are not part of aircraft simulation, if you know what I mean. I already cheat with D-button every now and then..

That's just me anyway, and I'm perfectly okay with the rudder 'trim setting' as the A2A has modeled it.

-Esa

[Hook]

I've already talked about it being added to the hangar, and think it would be a great idea. But there's this bucket, you see...

I guess we could cobble together an addition to one of the 2D panels to set the trim, but to be honest, using the keyboard is available Right Now and works just fine. I was surprised at how little effect each click had; most rudder trim on FSX aircraft seems to add way too much for even one click.

I suggest making a keystroke that will center the rudder trim if there's not one already defined. Then, before every flight, you can center the trim then adjust it as you wish... 5 clicks right in my case. This value is *usually* saved with a saved flight, but don't count on it. If you start with a saved flight every time (I do) then you can edit the .FLT file for that flight and set:

RudderTrimPct=0.05

which is 5 clicks; you'll probably want a bit less. Just like the real aircraft, it's trial and error.

Hook

[L.A.]

Hi L.A.,

I'm not sure I'm getting you right, but I think that perhaps you are mistaking the aircraft rolling effect that's the subject here to be caused by simulation of engine torque primarily? I'd say the engine torque to be quite insignificant factor in these low-powered aircraft, as you say too. But instead, the power induced roll is created by combination of prop wash hitting the vertical stabilizer asymmetrically and P-factor (asymmetrically loaded propeller disk during high angle-of-attack flying) causing the plane to yaw left, which in turn induce left roll.

but we don't expect it to roll over to the side, either.

But they might do just that if you're not expecting. Slightly unrelated, but there was a case years back when PF, during the climb in ATR42, mistook that the autopilot was engaged on his command by PM, who was actually loading SID to the FMS. The plane flew uncontrolled for 28 seconds, according to report. During that time, the bank angle (left, btw) reached 35,5 degrees (over a degree per second, on average) and uncommanded turn led to heading error of over 80 degrees. Just to add here the only actual figures I quickly recall about hands-off banking in any aircraft. They need to be flown!

Hi,
I'm also one who says that roll will evolve from yaw..........if yaw is unattended. At least with dihedral, high wings such as a Cessna, and swept wings. When I say hands off, it means rigging and trim. You can take your hands and feet off the controls (in cruise) , and not feel or see an immediate yaw, roll, descent or climb. In otherwords, you haven't been constantly fighting opposing forces. However, without being "flown", the airplane will easily vary altitude by a hundred feet, in a matter of minutes, and be heading off in some other direction too. Note: With the RV, I did have aileron trim (to adjust for loads), as well as a two axis A/P, and a fixed rudder tab, that was adjusted for usual cruise speeds. It required some good right rudder on initial climb, which of course eliminates a want to roll left. As airspeed increased rather quickly, the need for a heafty right rudder, also diminished. The built in right engine offset, and fixed rudder tab, kept yaw forces in control. The engine offset, has an advantage of controlling yaw, as the throttle is moved back and forth.........since it's a contributing factor to the yaw, in the first place.

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.

[caliban]

I don't have any real-world aircraft experience,nor the the expertise to go into files and change parameters but I have spent a lot of time in FSX.
I have tried every which way and many hours to stop this 172 from banking to the left but the problem persists.As it seems to be not a problem for some but a chronic one for others,I can only assume there is a problem not with the sim172 but my programme files running the sim or possibly the flight controls(in my case a joystick).
For me,it is an 90% a/p experience.