Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Overbanking tendency

Tech Log The very best in practical technical discussion on the web

Overbanking tendency

Old 25th Oct 2021, 13:07
  #1 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
Question 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.
Black_Dawn is offline  
Old 25th Oct 2021, 13:16
  #2 (permalink)  
 
Join Date: Dec 2001
Location: FL, USA
Posts: 2,795
FAA publications are not always 100% correct theyíre just the least amount of wrong.
As far as Iíve 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.
B2N2 is offline  
Old 25th Oct 2021, 13:29
  #3 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
Hi B2N2
what about the difference of lift during a turn, is it wrong?
Black_Dawn is offline  
Old 25th Oct 2021, 14:33
  #4 (permalink)  
 
Join Date: Dec 2001
Location: FL, USA
Posts: 2,795
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.
B2N2 is offline  
Old 25th Oct 2021, 15:15
  #5 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
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 is offline  
Old 25th Oct 2021, 15:31
  #6 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,020
But not in FBW. The flight control computers will hold the bank and AoA for you.
vilas is offline  
Old 25th Oct 2021, 15:39
  #7 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,238
Black_Dawn

Itís a heck of a long time since Iíve taught this but if we are talking at ab-initio level certainly Iíd be careful of overthinking thisÖand as has been mentioned characteristics of the aircraft may enter into itÖ

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)

Iím a bit about the implication in one post that the effect is more pronounced at high angles of bank, maybe thatís an aircraft specific thingÖ..
wiggy is offline  
Old 25th Oct 2021, 16:15
  #8 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
Sorry, but I don't understand if there is a difference of lift between the wings during a turn or it is only evident in steep turns.
Black_Dawn is offline  
Old 25th Oct 2021, 17:19
  #9 (permalink)  
 
Join Date: Apr 2008
Location: cowtown
Posts: 391
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 !
fitliker is offline  
Old 25th Oct 2021, 17:28
  #10 (permalink)  
 
Join Date: Nov 2004
Location: Aberdeen
Posts: 165
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!
farsouth is offline  
Old 25th Oct 2021, 17:57
  #11 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
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
Black_Dawn is offline  
Old 25th Oct 2021, 18:14
  #12 (permalink)  
 
Join Date: Jun 2010
Location: Nanaimo, B.C.
Age: 64
Posts: 48
Glider pilots know that their aircraft have a pronounced tendency to overbank if not corrected with aileron and rudder.
dash34 is offline  
Old 25th Oct 2021, 18:37
  #13 (permalink)  
 
Join Date: Aug 2009
Location: Denmark
Age: 66
Posts: 365
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.
sablatnic is offline  
Old 25th Oct 2021, 19:23
  #14 (permalink)  
 
Join Date: Feb 2006
Location: 11 GROUP
Age: 74
Posts: 1,159
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.
POBJOY is online now  
Old 25th Oct 2021, 20:54
  #15 (permalink)  
 
Join Date: May 2011
Location: Australia
Posts: 287
Isnt that why planes have dihedral to counteract overbanking? The inner wing is flatter to the airflow therefore produces more lift to self level...
ChrisJ800 is offline  
Old 26th Oct 2021, 02:26
  #16 (permalink)  
 
Join Date: Feb 2011
Location: usa
Posts: 61
.. 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..
B-757 is offline  
Old 26th Oct 2021, 07:27
  #17 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
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?
Black_Dawn is offline  
Old 26th Oct 2021, 07:54
  #18 (permalink)  
 
Join Date: Apr 2015
Location: Netherlands
Posts: 172
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.
washoutt is offline  
Old 26th Oct 2021, 08:08
  #19 (permalink)  
Thread Starter
 
Join Date: May 2001
Location: Italy
Posts: 57
washoutt
I don't understand how could possibly the trim, which is acting on the elevator, alter the shape of the wings?
Black_Dawn is offline  
Old 26th Oct 2021, 08:51
  #20 (permalink)  
 
Join Date: Feb 2001
Location: The Winchester
Posts: 6,238
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…

Last edited by wiggy; 26th Oct 2021 at 09:01.
wiggy is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.