Page MenuHomeFeedback Tracker

Plane ROLL physics bug--> It does not TURN!!!!
New, WishlistPublic

Description

When banking a plane to the left or right side it does not turn but it continues to go straight forward.

by {9GU}Eagle_Flying
{F23035}

Details

Legacy ID
444689257
Severity
None
Resolution
Open
Reproducibility
Always
Category
Game Physics
Steps To Reproduce

1-Open Editor
2-Put a fixed wing plane on a runway (Buzzard)
3-Take Off
4-Roll the aircraft left or right
5-Notice it goes straight forward

Additional Information

http://en.wikipedia.org/wiki/Banked_turn

Fundamentals of Flight of the US Army (you can find it on Internet: FM 3-04.203):
7-152. An aircraft, like any moving object, requires a sideward force to make a turn. In a normal turn, this force is supplied by banking the aircraft so lift is exerted inward as well as upward. The force of lift is then separated into two components at right angles to each other. The lift acting upward combined with opposing weight is called the vertical-lift component. The horizontal-lift component (centripetal force) is the lift acting horizontally combined with opposing inertia or centrifugal force (figure 7-42). Therefore, the horizontal-lift component is the sideward force that forces the aircraft from straight flight, causing it to turn. If an aircraft is not banked, no force is present to make the turn unless rudder application causes the aircraft to skid in the turn. Likewise, if an aircraft is banked, it turns unless it is held on a constant heading with the opposite rudder. Proper control technique assumes an aircraft is turned by banking and that IN A BANKING ATTITUDE IT SHOULD BE TURNING.

Event Timeline

EagleFlying edited Additional Information. (Show Details)
EagleFlying set Category to Game Physics.
EagleFlying set Reproducibility to Always.
EagleFlying set Severity to None.
EagleFlying set Resolution to Open.
EagleFlying set Legacy ID to 444689257.May 7 2016, 5:44 PM
Echo added a subscriber: Echo.May 7 2016, 5:44 PM
Echo added a comment.Jan 12 2014, 3:53 PM

This needs to be fixed. Upvote.

Magpul added a subscriber: Magpul.May 7 2016, 5:44 PM

Yeah, i've noticed it, too. Upvote.

UPVOTED. But you DONT need to GO ALL CAPS!!!!!

Same problem with F-18 and other plane addons...

I assume that is because all planes (incl. addons) use the engine's shared flight model. and yes, this needs to be implemented. just like the TOH flight model, but that never happened :/

Who downvoted this...?

I don't know... someone who doesn't care about plane physics....

gutsnav added a subscriber: gutsnav.May 7 2016, 5:44 PM

This x 1000000. Same with the TKOH flight model.

i first want to point out that a3 does infact implement this, if you pay close attention the heading of the plane changes slowly with a bank (and no other controller input, using the a-143) it does seem slow, i wont lie

but, if i recall, doesn't centripetal force affect fighter jets significantly less? (again assuming no control input) and since the game doesnt have any slow movers yet, its hard to guestimate what the implemented effect is. 3rd party mods can't be expected to have properly implemented phyx yet.

your wiki article does also point out that in order to complete a bank turn, it requires the pilot to increase lift, otherwise you're just side slipping and losing altitude - this matches whats currently in the game.

as far as fighter jets go, i'm just remembering that as something i had learned once, but i can't find any clear info at the moment that doesn't require math i can't do :)

(my vote undecided until more i see more info, and other airplanes)

---

someone who plays this game has flown jets. anyone with that experience want to chime in?

Ok man your first point is correct, the plane actually seems to have a really minimal turn when banked on a side but I can disagree with your other points.

I haven't a direct experience with jets (sadly) but I play A-10c on DCS and many other aircraft on X-plane 10 that is considered the world's most advanced flight simulator, is certified by FAA and used for pilot virtual training. I can assure you that ALL PLANES make a cospicuous turn when banked.

Moreover I can cite the manual Fundamentals of Flight of the US Army (you can find it on Internet: FM 3-04.203) that says:

7-152. An aircraft, like any moving object, requires a sideward force to make a turn. In a normal turn, this force is supplied by banking the aircraft so lift is exerted inward as well as upward. The force of lift is then separated into two components at right angles to each other. The lift acting upward combined with opposing weight is called the vertical-lift component. The horizontal-lift component (centripetal force) is the lift acting horizontally combined with opposing inertia or centrifugal force (figure 7-42). Therefore, the horizontal-lift component is the sideward force that forces the aircraft from straight flight, causing it to turn. If an aircraft is not banked, no force is present to make the turn unless rudder application causes the aircraft to skid in the turn. Likewise, if an aircraft is banked, it turns unless it is held on a constant heading with the opposite rudder. Proper control technique assumes an aircraft is turned by banking and that in a banking attitude it should be turning.

The last point is fairly conclusive, and is also logical because, as in the wiki image I posted, if a plane fly it has portance, if a I bank it a part of this portance became centrifugal force so, for transitivity rule, if a plane fly it makes turns when banked.

Sorry for my english but I'm Italian ;)

but, if i recall, doesn't centripetal force affect fighter jets significantly less? (again assuming no control input) and since the game doesnt have any slow movers yet, its hard to guestimate what the implemented effect is.

This is wrong. The "centripetal force" as you call it depends solely on roll angle - it is L*sin(θ), where θ is the roll angle, and L is lift (which is equal to m*g for a properly trimmed plane at any orientation). There's no "jet/no-jet" factor in the formula.

Example @45 degrees bank:
1-st case: no pilot input, plane is trimmed for level flight (1g, L = m*g)
Lvertical = L*cos(θ) = m*g*cos(θ) = 0.7 * m*g
Lhorizontal = m*g*sin(θ) = 0.7 * m*g
As you can see, the plane would experience a 0.7g lateral acceleration and a 1.0-0.7=0.3g vertical acceleration (losing altitude)

2nd case: pilot is countering loss of altitude by adding pitch input
Lvertical = L*cos(θ) = m*g => L = m*g/cos(θ) = 1.42 m*g
Lhorizontal = L*sin(θ) = 1.42 m*g / 1.42 = m*g

As you can see, lateral acceleration with additional pitch applied is only 42% faster than same without manual input. So, the effect would be VERY noticeable. So, EagleFlying is totally correct here.

Moreover, a jet at bank must experience sharp slide to the side of the roll, unless countered by rudder. This is also missing.

Yup, noticed this as well. I was in favour of overhauling the entire flight model so didn't report it separately. Upvoted.

Also, see:
http://feedback.arma3.com/view.php?id=14463

i stand corrected! and i appreciate the math DarkWanderer, that does make it clearer

I will never fly aircraft in ArmA 3 until they fix it.
Looks like BIS devs don't know anything about flight fundamentals...

Upvoted!

[quote]Who downvoted this...? [/quote]
Im sure that a guy who downvoted it was a kid of BIS dev ;-)

izaiak added a subscriber: izaiak.May 7 2016, 5:44 PM

Simulate a real lift for each wing please ! It will increase the realism.

hladas added a subscriber: hladas.May 7 2016, 5:44 PM

There are also other forces.
see http://forums.bistudio.com/showthread.php?167067-Fixed-Wing-Flight-Model-%28dev-branch%29&p=2782356&viewfull=1#post2782356

edit:

Also, from your picture, the final force - it should only shift the airplane, not turn. If you explain me where the torque comes from, I'll be more than gratefull.
Torque, that will align the airplane with 'descending speed', is present and can be configured (I'm a programmer, not a config guy).

And pitch input will not increase your lift force by 42%, but it will cause torque and, turn your nose up, so the force from engines is used to cover the altitude loss.

Fennek added a subscriber: Fennek.May 7 2016, 5:44 PM

Here is the proper explanation why an aircraft turns.
http://forums.bistudio.com/showthread.php?167067-Fixed-Wing-Flight-Model-(dev-branch)&p=2793625&viewfull=1#post2793625

the banking turn of an aircraft cant be explained with centrifugal force. It's an aerodynamical effect that causes torque and therefore produces centrifugal force. Proof is the simple fact that you cant make a banking turn with an aircraft in vacuum, even if you had "lift" and gravitational force.

Torque that aligns plane with descending speed is physically wrong/ incomplete. It needs to work for all coordinates and speeds.

See here for how it could be done:
http://forums.bistudio.com/showthread.php?167067-Fixed-Wing-Flight-Model-(dev-branch)&p=2793937&viewfull=1#post2793937

Echo added a comment.Oct 13 2014, 11:53 PM

I'm not educated in aerodynamics or anything similar, but isn't torque also produced by the fact that the center of lift and center of mass aren't in the same place on the aircraft?

No it's not a reason why aircrafts do turn when banked.
But yes, discrepancy between center of lift and center of mass produces a torque.
Ideally, center of lift= center of mass. If this is not the case you need to trim your controll surfaces to account for the torque (unless it becomes too extreme in which case the aircraft becomes uncontrollable/unstable)
That's why rules/guidelines exist for all (military and commercial) aircraft how much mass imbalance you are allowed to have, in which order you are allowed to fire your weapon, and in which order you have to deplete your different fuel tank cells and so on.

As we dont have trim in A3 it should be avoided to have center of lift outside center of mass/ vice versa.

Fennek: Thank you, will check it.