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Aerodynamics for dummies


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  • Senior Technical Moderator

I think it is just physics.

 

Here is the situation:

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-Most of the slipstream is actually cut by your wings. It implies that even though you will have some yaw effect, you do not have the full effect as the wings will partially disrupt the flow.

-Your tail being away from your center of gravity, you have a nice torque which counteracts the yaw will little to not effort.

- When you have some speed, your vertical stabilizer + the whole fuselage will naturally keep your plane from slipping by design.

The main purpose of the rudder is to counteract the slip effect, and it is often

 

On the torque-roll effect, the is different.

-You have the engine torque by the simple fact that you convert rotation to propulsion.

-You have the torque from the wing disrupting the slipstream.

-You have the torque from the rudder being pushed by the slipstream.

 

The ailerons will have to be readjusted for every change of power.

 

At "high" speed, the yaw is naturally damped by the rudder. The roll hoever must be trimmed / corrected as there is not part of the aircraft with the sole purpose to counter it, unlike the vertical stabilizer and the rudder.

 

Torque roll is something quite significant for fighter planes, the MC.202 has asymmetrical wings for this reason.

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  • Senior Technical Moderator

That's a fair point.

 

The only other explanation I can think off is that the take-off speed of a 109 or a P-40 is about the same if not higher than the cruise speed of the Cessna 172 that I am used to fly.

 

So assuming that you don't have much effect on yaw at 100knots with the Cessna, I would expect the same for a fighter.

 

But that's my best guess.

 

It could also be the game limitation, but I remember seing my rudder moving to the side when increasing power, and you have a strong yaw at low speed when accelerating on the ground

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  • Senior Technical Moderator
4 hours ago, jcomm said:

Was that in SIM mode

mostly RB.

 

I don't expect the rudder to move without any input of any kind in a video game.

 

SB and RB have the same physics and everything.

RB allows mouse aim and 3rd person view, SB force mouse joystick (therefore limited instructor) and 1st person view.

 

that is the only difference

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  • 2 years later...
On 11/03/2014 at 13:13, Joao611 said:

Very good informative post! Thanks! :D (needs some typo corrections, tho)

 

But I didn't understand the "Compressibility" part, starting where you wrote "you will have some air going at the speed of sound". Where does this air speed happen?

Air impacts the wing at the LE and then either travels over the top of or under the wing, and the two streams converge at the TE and creates some turbulence. The air flowing under the wing "collects" in the pocket before continuing rearwards (generating higher pressure) and the air on top of the wing has a longer distance to travel along the airfoil than the air underneath and is thus spread out (lower pressure), but both streams take the same amount of time to converge at the TE because there continues to be fresh air at the LE displacing the air under/over the wing. Rate of speed is distance/time = speed (like miles/hour or Km/hour) and if air on top has more distance to cover in the same amount of time, wingtop air speed = wingtop length/time to pass = (under wing length + some distance)/time to pass. The P39 for example became transonic (some air travelling past the airfoil at/above the speed of sound and some under the speed of sound) at a relatively low speed compared to its structural rigidity and that's why it's hard to control in extended dives. Also, just take a look a the wing profile -- especially close to the fuselage -- and you'll notice the longer top/ shorter bottom design of the wing.

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  • 4 months later...

Can someone explain to me how "takeoff flaps" work with respect to the following context?

 

When I was a kid, I realized that with a paper airplane, if you fold the top-back/tail of the wings up (like a static elevator), that when you drop it, the air pressing against that folded section will pull the nose of the plane up. On the other hand, if you fold the top-back/tail of the wings down, then the air pressing against that folded section will pull the nose of the plane down.

 

When I think of the "takeoff flaps" on a plane, which extend downward, the paper airplane example would have me think that that the takeoff flaps would pull the nose of the plane down. Even with the whole pressure differential, I don't understand how with takeoff flaps the plane is then better at generating lift (and therefore going up). Is it because the flaps are towards the center of the plane, whereas in my paper airplane example the folded section was in the tail of the plane (similar to the elevator on a real plane)?

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29 minutes ago, YossiMan said:

Can someone explain to me how "takeoff flaps" work with respect to the following context?

 

When I was a kid, I realized that with a paper airplane, if you fold the top-back/tail of the wings up (like a static elevator), that when you drop it, the air pressing against that folded section will pull the nose of the plane up. On the other hand, if you fold the top-back/tail of the wings down, then the air pressing against that folded section will pull the nose of the plane down.

 

When I think of the "takeoff flaps" on a plane, which extend downward, the paper airplane example would have me think that that the takeoff flaps would pull the nose of the plane down. Even with the whole pressure differential, I don't understand how with takeoff flaps the plane is then better at generating lift (and therefore going up). Is it because the flaps are towards the center of the plane, whereas in my paper airplane example the folded section was in the tail of the plane (similar to the elevator on a real plane)?

 

It's simple... by extending flaps you change the geometry of the wings in such way that you are able to achieve lift off at slower speed, but you are creating more drag... so when you are taking off you extend flaps to lift off in slower speed and when you are safely in the air you retract them to gain speed... but regarding your paper airplane behavior I must say that you were recreating rather effect of elevator than flaps...

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