Control surface authority should decrease when airspeed decrease

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1

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Are you using Developer Mode or made changes in it?

No

Have you disabled/removed all your mods and addons?

yes

Brief description of the issue:

I have several flight time hours on a real Cessna 172, Cherokee 140. There is a physic reality that is badly simulated, or maybe not simulated at all is the effect of airspeed on surface control authority. At very low speed the surface control authority is poor and unresponsive while very sensitive at high speed. That is normal since a bigger airflow is acting on the surface. This have a lot of impact when piloting. For example, when at cruising speed on a real Cessna 172, I do some very gentle input on the yoke to make it turn or change its attitude. However, when landing a real Cessna just before touch down, at near stall speed, I almost fully pull on the yoke just to keep to nose up to the horizon before wheel touch.

In the simulator, when landing for example, the authority at stall speed is almost or the same as in high speed. This makes landing more tricky and not as realistic as with a real plane.

So, i don’t know if it’s a bug or a enhancement, but could you simulate control surface authority relative to indicated airspeed in order to better represent the reality ?

Thank you!

Provide Screenshot(s)/video(s) of the issue encountered:

Detailed steps to reproduce the issue encountered:

Make a flight with a Cessna 172 and test the surface authority at different speed and check the result.

PC specs and/or peripheral set up if relevant:

Build Version # when you first started experiencing this issue:

1.30.12.0

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Do you have the same issue if you follow the OP’s steps to reproduce it?

Provide extra information to complete the original description of the issue:

If relevant, provide additional screenshots/video:

2

I am really just curious; whilst I fully understand your comparative experiences, both airborne and in the sim, are you not able to remedy the situation in the sim by adjusting the axis sensitivity curves?

3

Curves would not address the issue. They only relate to the inputs made regardless of the condition of the aircraft.

1 Like
4

They have something like elasticity_table for every control, just needs to be managed properly, I think. From their SDK:
"A table that allows you to scale down the elevator control surface deflection angle depending on the current dynamic pressure. The table has a maximum of 5 values and has the following format:

dynamic_pressure:correction_factor, dynamic_pressure:correction_factor, etc…

Pressure is expressed as [psf](file:///C:/MSFS%20SDK/Documentation/html/Content_Configuration/SimObjects/Aircraft_SimO/Flight_Model_Definition.htm#) and the yoke correction factor is a [Percent Over 100](file:///C:/MSFS%20SDK/Documentation/html/Content_Configuration/SimObjects/Aircraft_SimO/Flight_Model_Definition.htm#).

The dynamic pressure being airspeed dependent, this allows to reduce deflection based on speed. Dev Mode aircraft debugging tools allow you to get the current dynamic pressure. The dynamic pressure can also be obtained with the following formula:

dynamicpressure = 0,5 * airdensity * airspeed * airspeed

Default value is: 0.0:1.0"

3 Likes
5

As AlpineB4652 said, sensitivity curves will affect the yoke input level at every speed which is not reprensentative of the real thing. However, I decide to flatten the curves a bit as a paliative means to decrease sensitivity at landing time. Because, as explained in the case, an hyper sensitive yoke at low speed is not realistic at all.

2 Likes
6

Thanks for the information. I’ll check those values and try to test it.

7

You’re absolutely correct, but the problem is not simply the effectiveness of controls, but the feedback imparted by the airflow. During real-life slow flight, the controls are less effective, but also less stiff, leading to what we all call “mushiness.”

Conversely, when cruising, the controls have a lot more authority, but are generally stiffer due to the dynamic pressure and stability forces acting upon the control surfaces.

The sim does in fact account for the loss of authority - try bringing in a Cessna at 80 knots versus 50 and see how much elevator authority you have in the flare. What it’s not giving you is the feedback or even the re-centering effect that is imparted by trim at various airspeeds.

And forget the effect of stall buffeting or turbulence, haha.

No two airplanes fly exactly the same in real life (especially when going between makes and models). So I look at the sim, and each aircraft within it, as just another airplane to learn, with all the weird quirks. Trying to compare apples to apples doesn’t work.

3 Likes
8

The stiffness is effectively an excellent point to consider and maybe it influence the perception I have with a 400$ simulation yoke that, by nature, has a fixed stiffness.

I did some intensive tests tonight with the MSFS C172 and I can perceive a decrease of elevator authority near stall speed on the flare but it is very subtle compared to real life. Another factor I think must be considered is that the real 172 yoke elevator pull/push action has more travel than a simulation yoke. This travel difference is contibuting to the subtlety of the decrease in control authority.

having said that, I will get used to the idea that, as you said, the aircraft in the simulator have their own characteristics with which to maneuver.

Thank you for your comment!

1 Like
9

All this is relevant to the absence of force feedback support in the sim. The forces on control surfaces should be calculated, not only for how they affect how the aircraft flies, but also to be able to reflect the pressures on the controls.

4 Likes
10

Exactly. Lack of realistic, dynamic control pressure is one of the three main factors the sim cannot currently recreate to achieve as much realism as possible. Of the three, it is the most achievable.

The other two are:

Spatial proprioception (which I don’t know if we’ll ever achieve, especially at the consumer level).

And realistic risk/consequence, which we don’t want :slightly_smiling_face:

Of course, other things could be improved, weather, ATC, sound, etc, but these three are the areas in which we haven’t even left the gate.

2 Likes
11

If on PC try the excellent ‘input monitor’ freeware from flightsim. This allows you to monitor the exact amount on input - and if you record your screen then you can go back and do analysis.

1 Like