Help me with my c172

[MEFISTO]

I have P3D V4, i dont know why my C172 is always making a big left banking It's frustrating

[flapman]

Your software is functioning perfectly!

Enjoy

https://www.youtube.com/watch?v=TYn1GrvtPXU

[Hook]

"At cruise speed an airplane does not want to turn to the left." That is at 2:00 into the video right after the diagram changes to the rear of the plane. And he explains why.

Thanks for posting that. Next time someone claims the left turning tendency in cruise is normal, I have something to show them.

Obviously when climbing under high power you'll need to input some right rudder. When descending at low power you may need left rudder; I did in a real Cessna 150. But when flying level at cruise power there should be no turning tendency. The 172 has a small aluminum tab on the bottom of the rudder that can be bent to adjust it on the ground to fine tune out any turning tendencies.

If you have more fuel in the left tank than in the right, the aircraft will want to turn left in cruise. The pilot sits on the left side of the plane and may cause some turning tendency unless the aircraft model compensates for it, which the A2A Cessna 172 does.

Hook

PS. Is this guy's right eye a prosthetic? It shares characteristics with my wife's prosthetic eye... but hers looks more natural. People can't tell.

[Lewis - A2A]

But when flying level at cruise power there should be no turning tendency.

Sorry but this is simply not true. Unless you put some work in, no aircraft will fly hands off for very long without changing course. Even a great trimmed aircraft will still move around, theirs fluid dynamics in a moving fluid at play here and a whole mess of other dynamic factors. Its not a train on a track.

thanks,
Lewis

[Hook]

"At cruise speed an airplane does not want to turn to the left." That is at 2:00 into the video right after the diagram changes to the rear of the plane. And he explains why.

Quote from the video. Flight sim conventions may be different, possibly because there is no vertical stabilizer cant. This was the first time I'd heard that the wings might also at different angles. I knew about the cant long, long ago.

If you need right rudder in the climb and left rudder in the descent due to the power differences, then there will be a sweet spot between climb and descent power where you do not need rudder.

In the Microsoft Flight Stearman this was obvious. At high cruise power the plane wanted to turn left, and at low cruise power it wanted to turn right. I've never see this in other flight sims.

Thanks again to flapman for providing the video link.

Hook

[Oracle427]

Too little info provided.

What are the conditions?
Weather
Loading
Power settings
Phase of flight

The A2A 172 does trim out quite nicely in cruise, at least for me it does. I would also strongly recommend zero null zones and max sensitivity for controls to allow for the minute corrections that are required with these flight models.

The only way to get a perfect hands off flying experience is with the autopilot. Even in the real plane you will not be able to fly hands off for very long, especially if the conditions are not perfectly smooth air.

[Hook]

Just to be sure, I'm not talking about flying on rails. I'm talking about the tendency of a flight simulator aircraft to always want to turn to the left. People begin to believe that this is natural.

I know the cause, and I believe A2A does too after examining a few of their aircraft.cfg files. I've found that the 172 and Cub do not have a turning tendency, and as long as the fuel loads are balanced side-to-side the Cherokee does not either.

In early morning before the sun heats the ground and the convection layer starts to form, you can find air smooth enough to fly on rails. One real life pilot referred to this as "FSX weather." If your aircraft wants to bank left in these conditions when the loads are balanced and cruise power properly set, it is wrong.

Likely causes of the 172 having a moderate left turn tendency: Climb power, unbalanced lateral loads (mostly fuel), rudder (or possibly aileron) trim set to one side inadvertently (you can do it with keyboard commands), or a possible control conflict.

I used to add a couple of extra gallons to the right Grumman Goose fuel tank to counteract the left turn problem.

Hook

[Hook]

Here's a quote from the Avsim forums many years ago:

Except early morning or in colder weather, a light plane experiences a LOT of air movement. The atmosphere is a sea of air, just like the ocean, with currents and waves and eddies and turbulence at most times. Like the sea, it can occasionally be smooth as glass, but like the sea, that is an exception. A small plane, like a small boat on the sea, usually experiences some bobbing and movement. Planes, like boats, are lifted up and carried down by the movement of the fluid they are riding. Air is a fluid.

I've had this in my notes ever since it was written.

I considered installing CumulusX in P3D v2.5, not necessarily for the thermals but for the "atmosphere texture" it provides, and discovered that P3D apparently supplies its own texture. I was getting the same effect without CumulusX. I've heard that it is possible to get CumumusX running in P3D but I had problems and removed it.

Hook

[Oracle427]

I keep threatening to do it. Next time I go up in daytime with some good weather, I'll record my panel, yoke and external view all at once so that you can see the turning tendencies of the 172.

My experience has been that the airplane will roll off to one side eventually no matter what you do. The question is how long it takes.

[Hook]

I think we can all agree that the airplane is not supposed to fly on rails on any kind of normal atmosphere. That's not the problem. If you are trying to hold a heading within a degree (or two) you *will* be doing control inputs. But there will be an equal number to the left as to the right... assuming the aircraft is trimmed and loaded properly.

Consider this: If someone couldn't keep his airplane flying on rails because of turbulence, what would he complain about? "I can't keep my airplane straight!" This is a totally different problem and not the one the original poster is complaining about.

We get lots of complaints in flight sim communities of planes wanting to turn left. I've never seen one where someone complained that their aircraft wanted to turn right.

So where are the flight instructors who can explain to a new pilot what is happening without resorting to technical language? The way I remember it was, "When you are climbing, the plane wants to nose left, so you'll need to hold a bit of right rudder to keep the nose straight. In a descent you'll need to hold a bit of left rudder."

Continuously endeavor to eschew superfluous sesquipedalian verbiage. The beginning student doesn't need to hear about torque, P-factor, gyroscopic precession, etc etc on his first flight. That's for ground school.

There are a handful of other problems related to any left turning tendency in level flight and cruise power. One of them is that our controls do not quite mimic a real aircraft. Some compromises have to be made for the less than totally hardcore simmer.

Hook

[Simicro]

https://youtu.be/gzxt2SzOsAY

[Oracle427]

For the benefit of the OP, I still want to know the parameters that I requested. We still don't know what the circumstances are and whether left turning tendencies are appropriate or not.

The answer is nuanced as made clear by Hook.

[Hook]

Thanks, Oracle.

This person is a beginner and may not understand what you are asking for.

My best guess as to what the problem is: He's running full throttle in cruise.

The A2A 172 will not have a problem with having the only passenger on the plane being the pilot, which will cause left turning tendencies in most non-A2A aircraft (see my comment on the Goose). He likely has the same amount of fuel in both tanks so there shouldn't be a problem there. Lots of problems having to do with controllers but the question comes up far too often for everyone to have the same problem. He may have accidentally set some aileron or rudder trim with the keyboard, but that is unlikely.

I've had times when I had to set some rudder trim on the DC-3 when flying in crosswinds (-2 to +10), so that is a possibility, but you could end up turning in either direction in that case. I don't know if this affects the A2A 172.

Anything else you can think of?

Note: I have the DC-3 rudder trim effectiveness set down from 1.0 to 0.2 for finer control, and I typically have it set for +4... meaning at recommended cruise power it will turn left very slightly. I could probably edit this out in the aircraft.cfg file. Or find a better cruise power setting.

Hook

[flapman]

Out of curiosity, I fired up FSX (Acceleration) and the default C-172 at Friday harbor, and set about 2300-2400 RPM giving me about 115 KIAS (I assume it has a cruise prop)

Once it was stable and in trim, I let go of all controls and watched it maintain almost perfect heading and altitude (using ASN real world weather and Cumulus-X).
This is what I would approximately expect of a Cessna with properly rigged controls in this situation.

It seems there might a misunderstanding as to the difference between deviations from intended flight path due to natural unbalances, turbulence, and oscillations... and the deviation which results from uncorrected turning tendencies.
Having a 172 wander to the left in cruise due to the former is acceptable from my view. However, an aircraft which immediately and consistently rolls/yaws left would indicate an issue with the control centering. An example of this is an improperly set (ground adjustable) rudder trim tab.

Going through turning tendencies in cruise conditions....

P-factor = very little AOA on the propeller disc, negligible asymmetric thrust.
Torque = present, but slightly less than full power. Counteracted by vertical stabilizer incidence/ fixed rudder trim/ control rig.
Gyroscopic procession of the propeller disc = none present due to steady pitch+heading
Spiraling slipstream = greatly reduced due to elongation of the airflow, greatly increased tail effectiveness at cruise speeds, and possible trimming+rigging

If you can consistently predict the deviations from flight path in cruise configuration then you have an aircraft out of trim
And yes... that does happen... often your school/company will have "that one airplane" which flies a little "crooked"

[Hook]

I keep threatening to do it. Next time I go up in daytime with some good weather, I'll record my panel, yoke and external view all at once so that you can see the turning tendencies of the 172.

My experience has been that the airplane will roll off to one side eventually no matter what you do. The question is how long it takes.

https://www.youtube.com/watch?v=Yk-hAomZ3j0

I didn't mention that every time I watch a real world cockpit video I keep a close eye on how they work their controls. This video is a Beaver, fairly interesting. Note how little he moves the yoke to keep the wings level, at least when he's not in slow flight, and how often he takes his hands off the yoke and for how long. The air isn't totally smooth either. What I saw in the video is about what I experience in the sim.

It is not obvious whether he is keeping any kind of pressure on the yoke to keep the wings level, or how he is using the pedals.

I was looking for how much opposite aileron he needed in steeper turns. It was interesting how he pulled the prop control back with the throttle every time he reduced throttle. I hadn't heard of that before.

To make sure we are all using the same definition, when I say "turning tendency" I am talking about a tendency to always turn in the same direction. If it turns in both directions equally, then there is no turning tendency. There may or may not be some instability where you have to work harder to keep the plane level.

Hook