Flaperons reduce adverse yaw?
12-12-2009, 11:47 PM
#1
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Flaperons reduce adverse yaw?
The PHAN states the following in the flight controls section:
"In an attempt to reduce the effects of adverse yaw, manufacturers have engineered four systems: differential ailerons, frise-type ailerons, coupled ailerons and rudder, and flaperons."
I understand how the first 3 listed counter adverse yaw, but how do flaperons assist in reducing adverse yaw? From what I've read they are simply ailerons that can be lowered together to act as flaps while still being able to move in opposite directions for roll control. I can't figure how this reduces adverse yaw?? The PHAN doesn't give an explanation.
"In an attempt to reduce the effects of adverse yaw, manufacturers have engineered four systems: differential ailerons, frise-type ailerons, coupled ailerons and rudder, and flaperons."
I understand how the first 3 listed counter adverse yaw, but how do flaperons assist in reducing adverse yaw? From what I've read they are simply ailerons that can be lowered together to act as flaps while still being able to move in opposite directions for roll control. I can't figure how this reduces adverse yaw?? The PHAN doesn't give an explanation.
12-13-2009, 08:17 AM
#2
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Posts: 317
Apply your knowledge of differential ailerons, why do we use them?
Background: The downward deflection of the ailerons is about 15 degrees and the upward is about 20 degrees in most trainer aircraft.
Now think about the size of a surface. If we have a 3 foot long aileron going down, will it have to deflect more or less than a 6 foot long aileron to achieve the same result? Apply your answer to the flaps combined with the ailerons for turning.
Finally, apply what you have learned in weight and balance about arm. Do flaps have more or less arm than ailerons? So would they effect adverse yaw more or less, that is, would they have a greater moment?
Hope that helps.
Background: The downward deflection of the ailerons is about 15 degrees and the upward is about 20 degrees in most trainer aircraft.
Now think about the size of a surface. If we have a 3 foot long aileron going down, will it have to deflect more or less than a 6 foot long aileron to achieve the same result? Apply your answer to the flaps combined with the ailerons for turning.
Finally, apply what you have learned in weight and balance about arm. Do flaps have more or less arm than ailerons? So would they effect adverse yaw more or less, that is, would they have a greater moment?
Hope that helps.
12-14-2009, 01:17 PM
#3
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Joined APC: Dec 2009
Posts: 32
Apply your knowledge of differential ailerons, why do we use them?
Background: The downward deflection of the ailerons is about 15 degrees and the upward is about 20 degrees in most trainer aircraft.
Now think about the size of a surface. If we have a 3 foot long aileron going down, will it have to deflect more or less than a 6 foot long aileron to achieve the same result? Apply your answer to the flaps combined with the ailerons for turning.
Finally, apply what you have learned in weight and balance about arm. Do flaps have more or less arm than ailerons? So would they effect adverse yaw more or less, that is, would they have a greater moment?
Hope that helps.
Background: The downward deflection of the ailerons is about 15 degrees and the upward is about 20 degrees in most trainer aircraft.
Now think about the size of a surface. If we have a 3 foot long aileron going down, will it have to deflect more or less than a 6 foot long aileron to achieve the same result? Apply your answer to the flaps combined with the ailerons for turning.
Finally, apply what you have learned in weight and balance about arm. Do flaps have more or less arm than ailerons? So would they effect adverse yaw more or less, that is, would they have a greater moment?
Hope that helps.
Last edited by gestrich19; 12-14-2009 at 01:33 PM.
12-18-2009, 05:34 PM
#5
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Your explanation makes sense - The moments from ailerons mounted more inboard (flaperons usually) should equal less drag moments.
The only part that throws me a litte is just as there would be decreased drag moments around the vertical axis, there also would be decreased moments around the longitudinal axis... To me- this should require greater aileron deflection to roll the aircraft at the same rate as an aircraft with outboard ailerons??
The only part that throws me a litte is just as there would be decreased drag moments around the vertical axis, there also would be decreased moments around the longitudinal axis... To me- this should require greater aileron deflection to roll the aircraft at the same rate as an aircraft with outboard ailerons??
12-18-2009, 06:39 PM
#6
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Joined APC: Jun 2009
Posts: 317
The only part that throws me a litte is just as there would be decreased drag moments around the vertical axis, there also would be decreased moments around the longitudinal axis... To me- this should require greater aileron deflection to roll the aircraft at the same rate as an aircraft with outboard ailerons??
12-18-2009, 08:33 PM
#7
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Yes. Someone can correct me if I am wrong here, as I am not positive on this one, but most aircraft using flaperons still have outboard ailerons using flaps to assist. Hope that makes sense. Point is, they don't take the ailerons off the aircraft, they are used as an assist.
As an aside, the term "moment arm" is synonymous with "leverage"- they mean the same thing.
