How do airplanes turn?

Almerick07

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I know a guy who just busted his CFI checkride with the OKC FSDO. Appearantly the examiner told him he was a student pilot and to tell him how the ailerons turned the airplane. The guy gave a pretty simple answer but the examiner wanted to hear, "the aileron changes the camber of the wing."

Not only does this sound a little fishy, but I know that isnt how I would explain a turn to a student pilot...makes me wonder about these FAA guys.

How would you (CFI) explain a turn to a student pilot?
 

mynameisjim

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I would answer "how an airplane turns" differently then how I would answer "how does an aileron lift a wing".

How was the question asked?
 

Tarzan

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An aileron does not change the camber of a wing. They change the angle of attack. The effect is a banked airplane resulting in a horizontal compentent of lift. Your buddy'd CFI didn't teach him very well.
 

minitour

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Moving an aileron up and/or down changes the chord line of the wing. Chord line and relative wind gives you angle of attack. So assuming the same relative wind, you changed the AOA...change in AOA, change in lift...wings move up/down plane turns.

-mini
 

VNugget

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TiredOfTeaching said:
An aileron does not change the camber of a wing. They change the angle of attack.
It changes both.
 

NookyBooky

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Almerick07 said:
I know a guy who just busted his CFI checkride with the OKC FSDO. Appearantly the examiner told him he was a student pilot and to tell him how the ailerons turned the airplane. The guy gave a pretty simple answer but the examiner wanted to hear, "the aileron changes the camber of the wing."

Not only does this sound a little fishy, but I know that isnt how I would explain a turn to a student pilot...makes me wonder about these FAA guys.

How would you (CFI) explain a turn to a student pilot?
I don't know, but I bet George W. Bush is behind this somehow.
 

HAL

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The question from the examiner was bull. Ailerons do not turn the plane - they change the lift of each wing to roll the plane around the longitudinal axis. Turning requires coordinated use of ailerons, elevator & rudder.

It sounds to me that the examiner was looking for a reason to fail this guy. It happens, especially in CFI checkrides. They have to keep their failure rate up to look good to their bosses.

HAL
 

learflyer

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Flight options acft sometimes quick turn in 8-10 mins. Depending on how quick the line guys are.
 

mzaharis

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It increases circulation, to account for the Kutta condition on a modified flow field. ;)
 

Pilot_Ryan

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The elevator is primarily responsible for turning - as in, changing the flight path - of the airplane. I doubt the examiner would have the veracity to comprehend the true meaning of that statement.
 

FN FAL

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Almerick07 said:
How do airplanes turn?

How would you (CFI) explain a turn to a student pilot?
It's pretty simple. Planes turn because a pilot's ego makes the earth pivot about his axis. I don't know how chick pilot's do it, but...
 

Tarzan

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VNugget said:
It changes both.
Whatever. Go look up the definition of camber. It's how the wing is shaped. The only way to change camber is through wing warping, akin to how the Wright Brothers did it.
 

mzaharis

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TiredOfTeaching said:
Whatever. Go look up the definition of camber. It's how the wing is shaped. The only way to change camber is through wing warping, akin to how the Wright Brothers did it.
Warping only changes the AoA of the wing at various points along the span. The camber (the displacement of the centerline of the wing cross section, or mean camber line, from the straight line connecting the leading and trailing edges) does not change in wing warping.

Here's another definition of mean camber line:

"The mean camber line shown in this illustration is the line that is equidistant at all points between the upper and lower surfaces of the airfoil. The mean camber line shown in this illustration is the line that is equidistant at all points between the upper and lower surfaces of the airfoil. "

I'm posting an interesting link that discusses the definition of camber:

http://www.centennialofflight.gov/essay/Evolution_of_Technology/airfoils/Tech5.htm

By that argument, aileron deflection does change the camber of the wing (at least the section whose chord line crosses the aileron), as it changes the mean camber line. It also changes the angle of attack, by changing the straight line connecting the leading and trailing edges.
 
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CRJDog

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Just treat them nice and she won't turn on you.
 

siucavflight

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TiredOfTeaching said:
An aileron does not change the camber of a wing. They change the angle of attack. The effect is a banked airplane resulting in a horizontal compentent of lift. Your buddy'd CFI didn't teach him very well.
Someone is not theaching their students very well, but then I guess that is what you would expect from a CFI who is "tired of taching". It changes both numnuts.
 

mar

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It's the weather vaning silly!!!

Ailerons do NOT turn the airplane. They BANK the airplane.

What happens after you bank the airplane is that you change the horizontal component of lift.

After you change the horizontal component of lift you change the relative wind.

And thanks to the weather vaning tendency (due to the vertical stablizer) the airplane changes heading...or turns!

It's due to the vertical stab and the *change* in the relative wind.

Ailerons only get it started.

Most DEs piss me off. I've only met two who knew what they were talking about.

Good luck.
 

NYCPilot

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I'd like to know how simple an explanation your friend gave thats was unsatisfactory. Maybe he was way off.

All CFI applicants should be able to explain such a basic concept. If the examiner asked how specifically the "Aileron" turned the plane, a proper answer would be that by lowering the aileron on the outside of the turn and raising it on the inside results in an increase in lift on the outside and a decrease of lift on the inside. This occurs due to the outside aileron increasing the camber and angle of attack on that wing. All you're doing in a turn is creating an imbalace in lift between the wings. One wing produces more lift than the other and causes a portion of the the vertical lift component to shift slightly into a horizontal component. Since you are diverting some of this vertical lift into horizontal lift, you will need to increase back pressure to maintain altitude. The back pressure is required since lift that was being generated to support the weight of the airplane has been taken away or shifted, you will need to develop more lift vertical lift to compensate for this. There is also a need to increase back pressure due in part to the increase in load factor. Load factor results when the airplane is moved from steady unaccelerated flight (straight and level as well as a constant speed climb may be consided as such). This added load factor increases the effective weight of the airplane and thus requires a greater amount of air lift to be generated in order to support this additional "phantom" weight. So this will also increase the amount of lift needed to be generated during a turn. While increasing the back pressure you are increasing the angle of attack as well which is the reason you generate more lift. You can increase lift by either increasing velocity or AOA. Here we are initally only using AOA. This increase in AOA has effectively increased drag (as a by product of lift) and so now the airplane begins to slow down due tothe retarding force of drag. In order to maintain your entry speed, a power increase is required to comepensate.

Many pilots mistakely believe that rudder is used to help an airplane turn. All the rudder does is to eliminate the adverse yaw that is created by the additonal drag created by the aileron being moved down. Oncethe controlsd are neutralized, rudder force may be relaxed unless torque is causing an yawing.

It is true that in order to make a coordinated constant speed and altitude turn you require coordinated use of ailerons, rudder, elevator and power.
 

Almerick07

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His answer seemed pretty clear stating the ailerons deflect the airflow either up or down either increasing or decreasing lift and they worked together to roll the airplane. He said he drew it, used a model airplane but the examiner wanted to hear the terms angle of attack and camber.
He was failed on the premise of lack of instructional knowledge by using the term deflection, the examiner said it confused him because he thought of ping pong balls. My buddy said he got a little into a changed horizontal component of lift and what not but wanted to keep it simple because the examiner said he was a student pilot.

That is the story and after doing a little research on my own, i came across the NASA website where it actually uses the term deflection....

http://www.grc.nasa.gov/WWW/K-12/airplane/alr.html

third paragraph down......
 

NYCPilot

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Well, I have to admit that if he excluded the term "angle of attack" I can see why the examiner was not satisfied. That is exactly what the deflected aileron is changing. I don't think the term deflection is incorrect as this is the physical movement of the control surface, but it deflects so that it can change the angle of attack.
 
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