5
$\begingroup$

Microsoft Flight Simulator is supposed to be a "simulator", so following the laws of physics.

However, I'm looking at a gameplay video (at 2:17) and it shows a plane reacting really quickly to the rudder.

By my estimate (I was a physics major), this does not seem realistic (consider the Gs the front and tail must be experiencing). But on the other hand I don't understand why Microsoft would compromise their own game. So I guess the two disbeliefs cancel each other somewhat.

Is the behavior of the plane shown in the video clip realistic?

Improve this question
$\endgroup$
3
  • $\begingroup$ The short of it is yes, but not for the Airbus A320 shown. The control surfaces can initiate that sort of violent movement, the flight computer simply will not allow such command to reach the actuators. $\endgroup$
    – PcMan
    Commented Dec 23, 2021 at 18:24
  • $\begingroup$ @PcMan The rudder on the A320 is not fly-by-wire. The rudder pedals are mechanically connected. The only restriction from the flight control computers (the FAC in this case) is the rudder limit as explained in ymb1's answer. See also this answer for a description of the A320 rudder. $\endgroup$
    – Bianfable
    Commented Dec 24, 2021 at 9:41
  • $\begingroup$ MSFS is rather-well-known for its... quirky physics. $\endgroup$
    – Vikki
    Commented Feb 21, 2022 at 19:11

3 Answers 3

Reset to default
6
$\begingroup$

That is a very rapid and instantaneous motion indeed.

Yes MSFS is a "simulator" - game. Its main selling point is visual reproduction on a PC screen of aircraft instrumentation and out-of-the-window views, and it can help in learning what aircraft systems there are and how to operate them. But how exactly the instruments respond is of secondary concern.

In contrast to this is a Level D Full Flight Simulator, which must demonstrate to aviation authorities that simulated aircraft dynamics are within tight tolerances of flight test data from the aircraft. For instance the sideslip angle response to a pedal input with both Yaw Damper ON and Yaw Damper OFF.

enter image description here

Responses above would be for a Level D sim of a subsonic passenger jet with gear UP, yaw damper OFF, at 10,000 ft and about 160 kts.

  • The pedal is deflected to about 1.5° in 2 seconds - a finite time, there is damping in the pedal feel, plus an opposing force.
  • The rudder deflects much in unity with the pedal, actuated by the hydraulic system.
  • As a result of the rudder deflection, sideslip angle enters a second order response with inertia and damping effects.

Peak value of $\beta$ = 2.4° is reached after 6 seconds, which is indeed not what we see in the video. Plus the response is an acceleration, as can be seen from the gradual increase of $\beta$ starting from zero until a constant yaw rate is reached.

So is the rapid and instantaneous MSFS response realistic? Not really, no. It looks like a rudder deflection equates to an immediate yaw rate, there is room for improvement.

Improve this answer
$\endgroup$
6
  • $\begingroup$ "there is room for improvement" I must say I don't understand why MS didn't get this right, considering that they do have an interest in making the game as realistic as possible. $\endgroup$
    – MWB
    Commented Dec 23, 2021 at 23:07
  • 1
    $\begingroup$ I fully agree with you. It gets even worse with some helicopter responses that I've seen which dive like a fixed wing when moving the stick forward, instead of mainly picking up airspeed. $\endgroup$
    – Koyovis
    Commented Dec 23, 2021 at 23:22
  • $\begingroup$ If the graphs are code generated, i.e. if it's not too much trouble, what would they look like if it were gamepad style input, i.e. full deflection for a short time then back to neutral? $\endgroup$
    – user14897
    Commented Dec 24, 2021 at 18:04
  • 1
    $\begingroup$ @ymb1 They are code generated, but the code resides in a Full Flight Sim with pedals loaded according to the real aircraft, requiring a high force to deflect fully when flying. Recording and matching of responses is done only for circumstances commonly encountered during flight, such a full pedal manoeuvre is not part of that sub-set. But the response to the game manoeuvre would be similar to above: a sine-wave like return and overshoot, continuing for several periods. With a longer period than above since vertical tail damping is higher, inertia stays the same. $\endgroup$
    – Koyovis
    Commented Dec 25, 2021 at 1:25
  • 1
    $\begingroup$ @Vikki Indeed, combined with the elasticity and friction in the linkage between actuator and the rudder, plus the hydraulic compressibility of the actuator (oil is compressible) $\endgroup$
    – Koyovis
    Commented Feb 21, 2022 at 23:33
5
$\begingroup$

It's a simulator as far as using a physics engine (Angry Birds is also a simulator in this regard), but not a simulator in terms of correctly modeling each plane's systems and physics (it gets better with paid add-ons).

The A320 shown in the video has a rudder travel limiter (as a function of speed) in real life.

The rudder authority in such a plane is sufficient to counteract asymmetric thrust when one engine fails (as long as the plane is not too slow), so without a limiter it is very powerful and can cause damage.

American Airlines 587 is an example of incorrect rudder use that broke the plane:

According to the official accident report, the first officer repeatedly moved the rudder from fully left to fully right. This caused increasing sideslip angles. The resulting hazardous sideslip angle led to extremely high aerodynamic loads that separated the vertical stabilizer.

— Wikipedia: American Airlines Flight 587

Also of note is what input method the person playing is using: gamepad, keyboard, twisting joystick, or rudder pedals with no feedback – all cannot match the real plane, and the first three can cause abrupt inputs leading to the wiggling seen in the video.

Related: Can Microsoft Flight Simulator help me learn to fly (or make me a better pilot)? (yes in some respects, no in others)

Improve this answer
$\endgroup$
7
  • $\begingroup$ So with the limiter removed, you believe that an A320 would show similarly quick wiggling of the tail as in the video at that airspeed? $\endgroup$
    – MWB
    Commented Dec 22, 2021 at 23:54
  • $\begingroup$ @MWB: In this answer I wrote with data from an incident, the sideslip angle was indeed big when the rudder was pushed by an incapacitated pilot. $\endgroup$
    – user14897
    Commented Dec 23, 2021 at 6:42
  • 1
    $\begingroup$ In these simulators the quality strongly depends on the aircraft you install. The default planes are very simple but many third party ones (commercial or not) are modelled to very little details. Certain dynamics aspects are hard to get anyway due to the limitations in the simulator, but the systems for controling the aircraft (FMS, electrics, hydraulics, air, engines) are often extremely detailed and respond as realistically as it gets. $\endgroup$
    – Vladimir F Героям слава
    Commented Dec 23, 2021 at 7:32
  • $\begingroup$ Just to clarify, it's not angle per se that bothers me, but the (angular) acceleration. $\endgroup$
    – MWB
    Commented Dec 23, 2021 at 8:23
  • $\begingroup$ @MWB: RE acceleration: the American Airlines 587 one was about 0.7 g lateral acceleration (from memory, but the report is public), and the other incident I linked to in my previous comment, the x-axis of the graph is time (very fast response). $\endgroup$
    – user14897
    Commented Dec 23, 2021 at 13:29
3
$\begingroup$

Is it realistic that a plane reacts very quickly to rudder input ... ?

It depends on the plane and how much rotational inertia it has in the yaw axis, in comparison to the aerodynamic yaw torque generated by the rudder. In something like a Cessna 152, or a Schweizer 1-26 sailplane, the yaw response to rudder input is pretty quick. Yet even in these aircraft, if the pilot gives alternating left and right rudder inputs, timed in synch with the aircraft's yaw response to the previous input, he or she can "pump up" a yaw oscillation that achieves a significantly larger maximum slip angle (as indicated by the displacement of the slip-skid ball, or the yaw string) than would exist if the pilot simply held one rudder pedal all the way down. (Think of a kid on a swing, reaching a higher altitude with each arc.) This is an indication that even in these lightweight aircraft, yaw rotational inertia is not trivial, which means that the yaw response to a rudder input cannot be instantaneous.

In an airliner, naturally, these dynamics would be much more pronounced.

Improve this answer
$\endgroup$
2
  • 1
    $\begingroup$ I've got video stashed away on some hard drive somewhere, of a hang glider pilot using the alternating left-right adverse yaw torques resulting from a series of alternating left-right weight-shift roll inputs, to "pump up" a yaw oscillation involving sideslip angles vastly larger than could otherwise be obtained in this rudderless aircraft-- again this would not be possible in an aircraft with negligible rotational inertia in the yaw axis-- $\endgroup$
    – quiet flyer
    Commented Dec 22, 2021 at 17:57
  • $\begingroup$ Yeah if you hit the eigenfrequency in yaw you’ll be achieving ever higher amplitudes. But is the response to a step input physically realistic in the video, I reckon it isn’t according to physics. $\endgroup$
    – Koyovis
    Commented Dec 24, 2021 at 2:01

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .