How does an aircraft turn?

Dazzler

Dazzler

Well-Known Member
The majority of pilots are taught that the ailerons turn the aircraft and the rudder is used to stay co-ordinated in the turn. But is that technically true?

A turn, by definition, is a change in heading. This comes about by a change of direction around the vertical axis i.e. yaw, which is controlled by rudder.

Aileron controls the aircraft's roll about the longitudnal axis and doesn't change the aircraft's heading, except by a by-product of using the ailerons, namely adverse yaw, which, by definition, is yaw.

So wouldn't it be more accurate to say instead that the aircraft turns by rudder, and the ailerons keep the turn co-ordinated?

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First off, I was personally taught that both the ailerons and rudder turn the aircraft. However, I can see the advantage in making things simpler by saying "the aileron's turn the aircraft, but dont forget to coordinate the turn with the rudder." - this is a handy way to teach it, but it is by no means 100% accurate.

A turn is a change in heading. A turn is facilitated by an increase in the horizontal component of lift, which is created by using both the rudder and aileron. To some extent, both are capable of creating a horizontal component of lift.

So, in my opinion it's both to some extent.
 
A turn is a function of a change in direction of lift. Usually this is acomplished by banking the aircraft (which then shifts a portion of the lift vector from the vertical plane to the horizontal plane) and then using the rudder to offset the adverse yaw created by the ailerons.

A "boat turn" (just jamming rudder in and yawing the poor old aircraft around) is a function of an unbalanced "lift load" on one side of the Vertical Stablizer which is created by changing the AOA of the Vertical Stab by deflecting the rudder to one sie or the other.

But the easiest answer to "what makes an airplane turn" is: the pilot.
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But the easiest answer to "what makes an airplane turn" is: the pilot.
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Autopilot, coupled to the GPS!!!
 
Thanks...I am way too computer illiterate to do that so I just asted the link in.
And i just feel like using this smiley
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The banked plane wants to fly in a sideways direction, the reason the nose turns is because the vertical stabilizer keeps it aligned with the relative wind.

Ailerons and rudder are just the way you get the plane to bank. You can also use just rudder to turn if you don't mind being glued to the wall for a while.
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The banked plane wants to fly in a sideways direction, the reason the nose turns is because the vertical stabilizer keeps it aligned with the relative wind.

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Huh?????


A plane turns due to the horizontal component of lift.
 
Skyguyed has it right. (what I understand to be right)

When you bank the aircraft the horizontal component of lift moves the aircraft side ways. What turns the aircraft (i.e. causes the nose to change direction) is the new relative wind created by the horizontal component of lift and how it interacts with the fuselage and the vertical stabilizer.

Saying its just horizontal component of lift is not a complete description of what is really happening to cause the turn. It is only part of the equation.
 
I was always taught that it was the horizontal component of lift... and I just looked in the Gleim (private) and the answer to the question of "What force makes an airplane turn?" is, "The horizontal component of lift." That's what the FAA says, so that's what I'll always answer.
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Horizontal component of lift is the basic FAA answer. It is not a complete answer that demonstrates understanding of aerodynamics. This very topic came up on my CFI check ride and my examiner did not like it one bit when I gave him additional info beyond horizontal component of lift. I ended up having him bring in three other examiners and I demonstrated turn aerodynamics to them. All three agreed with me 100% and my examiner had to eat s%#t.

Both Aerodynamics for Naval Aviators & The illustrated guide to Aerodynamics offer better depth on this subject.
 
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Both Aerodynamics for Naval Aviators & The illustrated guide to Aerodynamics offer better depth on this subject.

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Oh, come on...who wants to remember all of that jazz when we can just memorize 3.5 words for the answer??
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Both Aerodynamics for Naval Aviators & The illustrated guide to Aerodynamics offer better depth on this subject.

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And ironically, those are the books used for each of the aerodynamics classes that I've had.
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I guess they give us the basic info and expect us to actually read the books.
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And ironically, those are the books used for each of the aerodynamics classes that I've had.
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Is that really irony ???
 
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And ironically, those are the books used for each of the aerodynamics classes that I've had.
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Is that really irony ???

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ok, sorry, i've had some wine tonight... geez
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A better question is what makes anything turn. An airplane is fairly straight forward. A force is applied that changes the direction of motion, and that force is applied as described. If you want a more interesting challenge, sort out what makes a car turn. An airplane is actually a lot simpler to draw out!
 
Simplifying things a bit, deflecting the rudder does in fact alter the heading of the aircraft, but its velocity remains unchanged. To change velocity, some force must be exerted on the aircraft to accelerate it. Specifically, for a turn to occur, this force must act perpendicular to the current line of motion. In your car, friction from the tires provides a force that acts radially inward during the turn. In a plane, the wings provide this force and resulting acceleration. If you swing a rope with a weight attached to it over your head in a circle, the motion occurs because the tension in the rope accelerates the weight radially inward. To change the direction of the plane's motion, you've got to switch up the alignment of the four fources such that there is a resultant in the centripetal direction. Easiest way to do that is to bank the wings.
 
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