Overbanking tendency
Thread Starter
Join Date: May 2001
Location: Italy
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Overbanking tendency
In my years of flying, I've always believed that during a turn, the lift was equal on both wings. Recently I've found in the FAA-H-8033-3B pag. 3-13, a description of overbanking tendency due to a faster travelling outside wing in respect to the inside wing during a turn, so you have to counteract by opposite aileron when the desired bank angle is reached. Being now some years that I retired from flying, so I could be wrong, I can't recall to have ever used such a maneuver during a turn. I did some research in aerodynamics books, but did not find anything about this tendency. Could someone shed light on this aerodynamic fact.
FAA publications are not always 100% correct they’re just the least amount of wrong.
As far as I’ve always understood is that overbanking tendency is a function of static/dynamic stability inherent to the design and the amount of bank used in the turn.
For instance a C172 will slowly roll wings level from a shallow banked turn while it will steepen the bank in a steep turn.
So it displays positive static stability up to a certain bank angle.
Past that bank angle you need a bit of opposite aileron.
As far as I’ve always understood is that overbanking tendency is a function of static/dynamic stability inherent to the design and the amount of bank used in the turn.
For instance a C172 will slowly roll wings level from a shallow banked turn while it will steepen the bank in a steep turn.
So it displays positive static stability up to a certain bank angle.
Past that bank angle you need a bit of opposite aileron.
Aerodynamically speaking it is correct
Can’t find a better picture but visualize a line from the wingtip down to the ground or an imaginary point. This forms a cone shape with the (in this image) right wing higher in the cone then the lower.
So the higher wing has a longer distance to cover.
If your airplane would display static instability or even neutral it would have a overbanking tendency.
Since all GA trainers display stability it’s an academic subject rather then a practical issue unless you’re doing in excess of 45-50 degree banked turns.
As a CFI this is fun and easy to demonstrate after an appropriate ground lesson.
Can’t find a better picture but visualize a line from the wingtip down to the ground or an imaginary point. This forms a cone shape with the (in this image) right wing higher in the cone then the lower.
So the higher wing has a longer distance to cover.
If your airplane would display static instability or even neutral it would have a overbanking tendency.
Since all GA trainers display stability it’s an academic subject rather then a practical issue unless you’re doing in excess of 45-50 degree banked turns.
As a CFI this is fun and easy to demonstrate after an appropriate ground lesson.
Thread Starter
Join Date: May 2001
Location: Italy
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
So, if I've understood right, the right wing has more lift (being faster) and I've to counteract the overbanking tendency with opposite aileron. Is that correct?
Black_Dawn
It’s a heck of a long time since I’ve taught this but if we are talking at ab-initio level certainly I’d be careful of overthinking this…and as has been mentioned characteristics of the aircraft may enter into it…
All your average blogs or bloggess really needs to know is that they should select the attitude required for the turn (30 degree, 45 degree, whatever) and around the aircraft goes with the pilot making making small and appropriate control inputs to maintain the target bank..(and pitch A/R)
I’m a bit
about the implication in one post that the effect is more pronounced at high angles of bank, maybe that’s an aircraft specific thing…..
It’s a heck of a long time since I’ve taught this but if we are talking at ab-initio level certainly I’d be careful of overthinking this…and as has been mentioned characteristics of the aircraft may enter into it…
All your average blogs or bloggess really needs to know is that they should select the attitude required for the turn (30 degree, 45 degree, whatever) and around the aircraft goes with the pilot making making small and appropriate control inputs to maintain the target bank..(and pitch A/R)
I’m a bit
about the implication in one post that the effect is more pronounced at high angles of bank, maybe that’s an aircraft specific thing…..
Not an issue in most training aircraft until you get passed 50 degrees of bank , at 55 degrees of bank you are holding aileron to stop the roll . Most pilots never look at the yoke in a steep bank . But if you glance for just a moment at the yoke position you will see just how much opposite aileron you are using to maintain a steep turn at 55 degrees of bank . To hold that attitude you will have to hold up the wing . With the ball centred of course !
Not quite sure about the explanation of the higher wing travelling faster, therefore creating more lift, and this effect being greater the higher the bank angle . . .
If you look at the two extremes, a flat, rudder only turn would result in the highest difference between the wing speeds through the air, and the closer you get to a 90deg bank, the less the difference between the wing speeds - as the hypothetical cone that B2N2 refers to becomes closer to a cylinder!
If you look at the two extremes, a flat, rudder only turn would result in the highest difference between the wing speeds through the air, and the closer you get to a 90deg bank, the less the difference between the wing speeds - as the hypothetical cone that B2N2 refers to becomes closer to a cylinder!
Thread Starter
Join Date: May 2001
Location: Italy
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
here is a video by an instructor showing a steep turn without touching the yoke. Maybe because he didn't get passed 50 degrees of bank. It seems the wings are producing the same lift. So I'm confused!
from time 1:44
from time 1:44
Black_Dawn
That is absolutely correct when flying slower and or long winged aircraft, especially gliders, but you just correct for what the aircraft does. Not doing anything the aircraft will end in a death spiral, graveyard spiral, have seen several names for it.
Thermalling in a glider you will end up with rudder into the turn, and ailerons out of the turn. (Cross controlled).
Gliders won't turn on ailerons alone because of adverse yaw. I have tried, holding the camera with my hands, the stick with the knees, and no feets free for the rudder - not possible, way better to leave the stick to itself those few moments a picture takes.
That is absolutely correct when flying slower and or long winged aircraft, especially gliders, but you just correct for what the aircraft does. Not doing anything the aircraft will end in a death spiral, graveyard spiral, have seen several names for it.
Thermalling in a glider you will end up with rudder into the turn, and ailerons out of the turn. (Cross controlled).
Gliders won't turn on ailerons alone because of adverse yaw. I have tried, holding the camera with my hands, the stick with the knees, and no feets free for the rudder - not possible, way better to leave the stick to itself those few moments a picture takes.
Getting it around
Oh, I thought you got wings near vertical with the power ON and nose slightly UP to give a bit of fuselage lift, and kept pulling, ensuring if in a suitably strong Cessna (like a 180) you had the Top tank selected so the power stayed ON. A small touch of flap can help. Not recommended for NDB holds or CAA IR renewal.
.. Easy way to visualize the aerodynamics in a turn is to look at a Nascar racetrack ..The curves are tilted..The outer wheels of the racecar have to cover more distance around the curves, therefore they must be spinning at a slightly different speed than the inner wheels.. Same thing with the wings of an airplane in a turn, therefore there must be a difference in lift..
Thread Starter
Join Date: May 2001
Location: Italy
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
B-757
what you say is clear. I quote you "Same thing with the wings of an airplane in a turn, therefore there must be a difference in lift", so how do you explain the video I posted: the aircraft is in a 45 degrees bank steady, the pilot isn't touching the controls ( they are in neutral position) and the aircraft keeps going steady in the banked attitude without rolling; this give me the idea that the wings are producing the same amount of lift even in a turn. Am I missing something?
what you say is clear. I quote you "Same thing with the wings of an airplane in a turn, therefore there must be a difference in lift", so how do you explain the video I posted: the aircraft is in a 45 degrees bank steady, the pilot isn't touching the controls ( they are in neutral position) and the aircraft keeps going steady in the banked attitude without rolling; this give me the idea that the wings are producing the same amount of lift even in a turn. Am I missing something?
Doesn't a trim deflection alter the equal shape of the wings? So the inside wing may have slightly more lift than the outer one or the outer one slightly less. Dash 34 is right, I remember that from my gliding days.
I fear the discussion is headed down a rabbit hole but as a point of order I think the reference was to trim in roll (aileron and/or spoiler trim)…
FWIW I spent umpteen years flying around (gliders, fast pointy things, bigger things, some with FBW) and like you say in your OP I don’t recall ever having to consciously nudge or remind myself to apply out of turn spoiler/aileron…I don’t deny the aerodynamics theory behind this but I suspect like many I just (tried) to waggle the controls around to achieve the desired attitude/result…
FWIW I spent umpteen years flying around (gliders, fast pointy things, bigger things, some with FBW) and like you say in your OP I don’t recall ever having to consciously nudge or remind myself to apply out of turn spoiler/aileron…I don’t deny the aerodynamics theory behind this but I suspect like many I just (tried) to waggle the controls around to achieve the desired attitude/result…
Last edited by wiggy; 26th Oct 2021 at 08:01.