C175 Trim Challenge

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Here is a CHALLENGE to you – that should convince you that there is something seriously wrong with the aerodynamics of the C172 (and probably most of the other GA planes in FS2020, that NEEDs a strong following to push for a Fix.

Putting aside:
(1) You cannot currently adjust Joystick gain & dead zone, because of the update removing that GUI control.
(2) In fact we can eliminate the joystick from this challenge at all.
(You wont have to touch your Yoke once you are flying, clean, and trimmed for level flight)
(3) Putting aside the Autopilot (keeping it turned off)
(4) Not letting “ROGER” The AI pilot touch the plane

The Challenge is:

(a) Get the C172 up in the air at say 5000ft, with no live weather- Clear skies - No wind
(b) Clean configuration (Flaps all the way up)
© Not in a turn

TRIM the Plane for level flight - At full power with Mixture adjusted correctly, you should be at about 115 Knots

             VSI  = 0   !!!  (good luck with that)

Once you have achieved this level flight, then no more use of the Joystick —
You “should” be able to take your hands off the Yoke, and the trimmed plane should have pitch stability, and maintaining that trimmed vertical speed of 0.

ONLY adjust the TRIM wheel !!!

BUT it wont !!!

IF by some Miracle, you do achieve this, then give a gentle TAP to the Yoke, pushing forward about 10%, for a second and then releasing.
Just enough to pitch down a little.

Plane SHOULD then stabilize, back to the original trimmed level flight, and any small airspeed change, return to its previous value.

BUT it wont…

The Plane will Oscillate , pitching up and down, VSI +, then VSI -, with only a very small decrease in those changes over many many swings of the VSI needle.

ie Plane is UNSTABLE in a trimmed configuration… even in level flight, or up to +/- 500 ft/min.

NO wonder nobody can control the plane with their Joystick – it is now extremely difficult, if not impossible to do, no matter how you adjust your Joystick, because the Planes (or at least the C172) is basically “unrealistically” UNSTABLE.

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Oh, cool. So I’m gifted! It does take a bit of effort but it is possible to trim for hands off, more than there should be and I’ve got suggestions for that in other posts. The trim does not have fine enough control so I agree that is an issue but it isn’t that bad. One I get get trim right I sometimes have to change engine power a fraction to adjust for the lack trim fineness bit it isn’t a big effort.

So yeah, trim isn’t perfect. A massive issue or some issue with the overall flight model. Not at all.

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Agreed that the trim control available is a bit too coarse. My solution is to modify the VS - ever so slightly - with the throttle. Once you’ve got that done, the C152 and C172 both will fly “hands off” just as they should. You will still get lefthand drift due to P factor (again, just like real life) but the slightest right rudder (or trim) will compensate for that. Overall I think the two Cessnas have the best flight model, but those two A/C are also the ones I have the most hours in “for real.” :slight_smile:

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OK, so lets ELIMINATE even the adjustment of the TRIM control from this test. …
Get the plane trimmed in level flight and as stable as you can.

Then just momentarily apply forward pressure, and then release.
Nose dips down correctly
But then as the plane recovers, it oscillates VSI +, VSI - with very little if any reduction in the about it swings.

That is very far from Realistic, and it is this instability that makes the plane so hard to trim in the first place.

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I thought that the RL C172 had a small, manually bendable trim tab on the tail, to adjust that out in level flight at cruise speed ?

Maybe it got “damaged / bent” in the Upload :stuck_out_tongue:

https://cdn.boldmethod.com/images/learn-to-fly/systems/4-types-of-trim-tabs/ground-tab.jpg

unnamed

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Absolutely correct. It works admirably well too! :smiley:

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Yea… for me the real “tell” is watching the aircraft - pick any A/C at cruise - on autopilot “porpoise” slightly from negative to positive pitch. To some extent that’s true-to-life, but I’ve never flown, or flown in, any GA aircraft where you get a true sinus oscillation as is evident in Flight Sim.

I figure it is one more fine-tuning adjustment that will need to be dealt with as the weeks/months go by…

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The possible concern is – is this FS2020 aerodynamic modeling of the parameters set in each individual plane.
If its in the planes, then the planes that have this issue, obviously need to be corrected.
It looks like some have, to some extend … ie the 150X modded plane

But if it is back, deep within the sim engine, then when it is changed/fixed, then that change will affect EVERY plane that currently exists.

I guess is the major reason I am pushing this one so hard. The sooner it is addressed, the less current & future planes might need updating.

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Good point … so the Oscillation may be dues to Both the Planes lack of pitch stability, as well a s an autopilot whose response is not optimized for the plane,

hence my suggestion to leave the AP off when 1st looking at this.

Once the plane has right amount of Pitch Stability, then the Autopilot can be Tuned to match it.

BTW: Our Friend “ROGER”, the AI Pilot, (who is basically acting as an Autopilot), is able to control the plane and stop these oscillations, far better than the AP (or me).

I guess he has “Quicker Reactions” !!!

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I’ve said this many times. Glad to see it’s getting more attention. The problem is you have people come in and say everything works fine for them and they are a real pilot. I’ve only got 10 hours in a real plane and even to me it’s obvious these don’t fly right. Quite honestly we will probably never have it fixed. So just enjoy the scenery and work the autopilot

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Interesting re: Roger… :slight_smile:

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I couldn’t agree more with these findings. I’ve found the aircraft I’ve flown all unrealistically unstable in one way or another.

Whether it’s the core sim aerodynamic engine, or the individual aircraft, I couldn’t tell, but hope improvements are on the way.

(I’ve 1000’s of real hrs in MSFS models, for those who deem that important, even though I don’t)

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Maybe NOW is the time to get this sorted , and with some urgency, because it will also affect many of the future aircraft, yet to be developed for FS2020.

Another reason:- Force Feedback Joysticks & Yokes.
At this early time FS2020’s life, right from the start, would be the time to be thinking about these devices, which will come down in price and be more widely used over the next 10 year.
Associated with Trim, is the control of the FAKE TRIM processing that FSX & “still” FS2020 do, to FUDGE the operation of trim to cater for spring loaded, fixed centering Joysticks & Yokes.

Now is the time to give FS2020 the option to turn this on or off (globally in the system setup), as well as control with Simconnect read & writes.

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yeah i have also thinking over this days ago. The Trim is not much accurate…

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Glad it’s not just me …

It was not too bad in FSX, and it was always possible to “user Edit” the config files to get it better, but now in FS2020 it is ridiculously “unrealisticl”, and with the new DRM being applied to the Premium & Deluxe planes, as well as many Commercial Addon planes, the option for users to “self correct / tweak” this becomes far more difficult – Not Impossible, but more complex that it needs be for most.

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I’ve had no problems with trimming most aircraft, with the Saitek AP panel trim wheel.

Not sure about the return to stabilised flight when entering a dive. As you speed increases so does your lift, so it should start to level off, but I’m not sure about that oscillation. It sounds like fun all the same, so will give it a bash, and record some footage of my efforts, too!

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Are you guys sure your flight model is set to “Modern”?

I can pitch a 172 so it keeps VSI at 0 (takes some tweaking, but it’s also pretty difficult IRL)

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I, for one, am :slight_smile:

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Yep, set to modern. I’m with you: takes some tweaking but you can get both the C152 and C172 to cruise along “hands off” once things have settled down. In smooth(er) air of course. Once you’re headed over California’s coastal range all bets are off… :smiley:

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You can Tweak the STANDARD planes, but the Deluxe and Premium planes are Encoded, so they become a lot more difficult to alter.

The point is – why should we need to tweak them, after Microsoft have made such a big thing about the sim’s sophisticated modeling.

I purchased FS2020 to be a Sim Pilot, not a Sim Aircraft Mechanic

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