Fundamental rework of rudder and lateral dynamics on runway

A. Short description
B. Detailed description
C. Own video studies of mentioned aspects
D. Third party videos for explanation
E. Conclusion

A. Short description:
Several aspects of the lateral dynamics deserve to be reengineered.
While touchdown, planes tend to bounce to the side rapidly and heavily.
During rollout, aircraft bank from side to side using rudder inputs.
Yaw movements are often not smooth and transitions are edgy.
At high speeds the rudder has very low effect, runway excursions on crosswind are inevitable.
The handling does not feel smooth, movement transitions are edgy.
All aspects mentioned above intensify with increase of crosswind.

B. Detailed description:

Here i want to elaborate various aspects of the lateral and yaw dynamics that need to be redone in my opinion. All these aspect are equally important and are connected with each other.
But here i am looking at every single aspect, trying to elaborate fundamental causes:

  1. Wheel friction
    The wheels may have an unrealistic friction behavior (maybe too much friction and direction change when touching down).
    Real aircraft tend to „slide a bit“ towards landing direction due to inertia before the friction of the wheels „kicks in“, even on dry runways.
    See this example:
    https://youtu.be/9q2UQqJPwGM?t=30
    The 747 does not rapidly change direction on touchdown. Due to inertia it follows the recent flight path first, and the following direction changes are smooth.
    Even without prior decrab the aircraft does not change the direction that fast.

  2. Nose wheel behavior
    The nose wheel changes the aircraft direction instantly on touchdown, making the aircraft veering and going into the „nose direction“. Best seen on the CRJ Landing in the research video in minute 1:08:
    https://youtu.be/Z5MHVRI-h0M?t=68
    The change is not very smooth and occurs suddenly. Like the change of direction when you enter streetcar rails with the front wheel of your bicycle, as shown here:
    https://www.youtube.com/watch?v=aE3W4kEBhuE
    Here is a footage of a real CRJ 900 landing. Note, that on nose wheel touchdown the aircraft does not cause a severe directional change: https://youtu.be/kDeGoKsHxy0?t=4

  3. Severe bank on touchdown
    Gear struts consist of a spring and a damper. In large aircraft gear struts the spring and damping function is provided by a cylinder filled with gasious nitrogen and oil. Technical details just for interest here:
    https://en.wikipedia.org/wiki/Oleo_strut
    It seems, that the rebound of the gear is exaggerated, leading to a severe banking movement on touchdown. Lets take a 320 crosswind landing as an example. One of the crosswind landing techniques is:
    Touch down with the windward main wheel first, having the aircraft slightly banked into the wind.
    Then touchdown with the other main wheel and bring down the nose wheel last.
    this scenario can be seen in my research video in minute 4:16:
    https://youtu.be/Z5MHVRI-h0M?t=256
    There it seems, that the touchdown of the right main wheel with „200fpm“ causes it to rebound with „400fpm“.
    Due to the damping (dissipation of kinetic energy) and the 3rd law of Newton (actio=reactio)
    the rebound of the touching gear can never be greater than the initial impact.
    (At least without aileron input or gust…)
    Also the other crosswind scenarios shown in this video show that behavior, preferably at asymmetric touchdown.

  4. Rudder effectiveness
    The laws of aerodynamics state, that forces are dependent on speed. Squared.
    That means, that at high speed much rudder deflection has a great effect on an aircraft’s yaw movement. However, in IF even at the relatively high landing speeds the rudder seems to be very ineffective. In my research video these cases are very well shown at the following minutes:
    2:12 and 2:55.
    https://youtu.be/Z5MHVRI-h0M?t=132
    https://youtu.be/Z5MHVRI-h0M?t=175
    In both cases the rudder of the involved aircraft (747-8) is deflected fully to keep the aircraft on the runway, but in both cases a runway excursion could not be avoided.
    Keep in mind that the aircraft is still at high speed at this moment and the rudder has almost no effect in the simulator. Furthermore, it seems that the yawing effect increases at lower speeds. But i am not sure if this is caused by the rudder or the wheel physics.
    Even without decrab the rudder has to be way more effective when on runway.
    This phenomenon occurs for all aircraft to some extent.

  5. Banking on runway while rudder input
    Especially for aircraft with narrow main gears this phenomenon occurs very easily.
    Although it is understandable, that a narrow gear reinforces a potential tumbling behavior, in my opinion it is too much in Infinite Flight.
    To see what i am describing, here again the part of the research video featuring a CRJ-900:
    https://youtu.be/Z5MHVRI-h0M?t=51
    The next video shows the CRJ-900 landing in the real world again. As you can see: despite the rudder inputs by the pilot, the aircraft does not show excessive tumbling behavior. The wheels remain on ground and the wings are level.
    https://youtu.be/kDeGoKsHxy0?t=4

  6. Edgy, rough movement
    Especially on the runway during the landing run, change of direction in my opinion is not smooth enough.


C. Own video studies:
Note: The video is only visible to people having this link, it can not be found on youtube search.
https://www.youtube.com/watch?v=Z5MHVRI-h0M&feature=youtu.be&t=1

D. Third party videos for explanation

747 crosswind: https://youtu.be/9q2UQqJPwGM?t=30
nose wheel analogy: https://www.youtube.com/watch?v=aE3W4kEBhuE
CRJ-900 crosswind: https://youtu.be/kDeGoKsHxy0?t=4

E. Conclusion:
Let me try to give you a conclusion of what needs to be done in my opinion:
Finding a better compromise between controllability and inertia.
Hard to describe, but: These edgy, bouncy movements often give me the impression of controlling a „toy RC plane“ instead of a „real aircraft“.
The balance between „steering by rudder“ and „directional control by wheels“ is not right for some speeds.
The transition air to ground at crosswind scenarios is problematic.

I will be pleased to hear your thoughts on this, maybe you can provide some more constructive input on this matter!

Note that this is not a request to provide a seperate rudder/tiller system, but a rework of the physics involved. This is why i created a new topic apart from the existing request to seperate rudder and tiller steering.

Thank You for voting!

Hello there

I have watched a few of your videos and some of the things that you had mentioned were respectfully a result of some pilot error. If I may, I’d like to explain some of the issues that I noticed that I believe led to the creation of this topic,

As noticed in your video here, rudder inputs were way too aggressive. At the 1:13 mark, you were just touching down with a cross wind and no rudder input was recognized to remove the aircraft from the crab. Prior to touch down, the nose of the aircraft needs to be parallel to the centerline. At the same, gentle but deliberate usage of the rudder is necessary to keep the aircraft under control.


Similar case in this situation as the previous example above. At 4:21, you touch down with no rudder input prior to touch down. At 4:23, rudder is recognized but it is too late at this point.


I agree and can see where you’re coming from; however, in Infinite Flight, as speed increases, our nose-wheel effectiveness decreases. Rudder effectiveness is there once the nose-wheel is weight off wheels. And again, in this third example, rudder input was not recognized and was input after touch down rather than prior.


I think if you try some of the techniques as I have mentioned above as well as some of the techniques in the link below, you’ll find that the rudder and lateral dynamics of the aircraft are rather done quite well. Friction, drag and any other forces that would otherwise affect an aircraft’s ability to track straight down the runway on a takeoff or landings are mirrored from their real world counterparts. This information is derived from real world pilots that we have within our internal testing team. We continue to do regression testing on all aircraft to ensure that issues don’t slip in where they’re unwanted.

Again, I hope this is of some use, but I think before we request a rework, we’ll need to see some other evidence that indicates to us that one is needed rather than something that can be corrected by the pilot.

Thanks
Matt

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Thank You for your answer!
I accept that own flying techniques can improve the landings of course.
Nevertheless, if the rudder effectiveness in the real world was similar to the Sim, we would have many runway excursions every day.

Here a 747 pilot on the “rudder-matter”:
https://youtu.be/7MXbPHSGveY?t=412

2 Likes

Agreed. And that aircraft in particular is one of the older flight models. Needs a bit of a rework. We do have a 747 rework topic that can be found here:

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Yes, i voted this :)
But it occurs on all aircraft to some extent, that is why i thought it is a general matter not only limited to the 747.
Also MD11, A320 (flown these often here) have this problem

3 Likes

I find rudder control in flight very unrealistic. Although I never got my PPL I did get to do circuits in a Piper Warrior and in one lesson the instructor got me to fly a circuit with just trim and rudder which I managed pretty well (his words!). There is no way you could do that in the Cessna 172 although I did try. The rudder seems slide the plane sideways. I think this is a problem so support the yaw model to be looked at.

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Yaw is definitely the biggest issue. I’ve managed to handle crosswind takeoffs and landings in MFS2020 fairly easy. Doing so in roughly the same conditions in IF and I’ve become a lawn decoration.

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Also, and not sure if this is caused because of similar/same issues in the flight model, but does anyone else find that there is no crosswind effect under rotation. Like, you need to no rudder input at all during T/O roll, but then the moment you begin rotation you suddenly need pretty much full rudder. Sorry if that makes no sense 😂

I have to admit that if nothing else - we definitely need a rework of the rudder and the yaw physics in infinite flight.

I have had it loads of times when you correct the yaw using the rudder and as soon as you release rudder the plane starts bouncing from side to side!!

and I’ve seen a few comments here about yaw so im guessing it’s a fairly well-known issue - but would be awesome to see it improved in the sim!! :)

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