How would you demonstrate the secondary affects of roll?
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How would you demonstrate the secondary affects of roll?
The secondary affect of roll is yaw, but how would you best demonstrate this to a student? I've found this very hard to eyeball myself, let alone explain it to a student.
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Errrrmmmmmmm wouldn't secondary affects of roll produce a yaw opposite to the roll ?
The way I was taught was to line up the nose with a feature, (we used a church steeple) then roll left and watch the nose move right compared to the feature. Similar the other way.
My instructor made me practice reversing the roll left and right while lined up with the feature as a way of practicing to co-ordinate rudder.
The way I was taught was to line up the nose with a feature, (we used a church steeple) then roll left and watch the nose move right compared to the feature. Similar the other way.
My instructor made me practice reversing the roll left and right while lined up with the feature as a way of practicing to co-ordinate rudder.
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Karl Bamforth
"Errrrmmmmmmm wouldn't secondary affects of roll produce a yaw opposite to the roll ?"
Have a re-read of your Principles of Flight - you have confused secondary effect of Roll with Adverse Yaw. DB6 has described a good way of demonstrating this effect.
Have a re-read of your Principles of Flight - you have confused secondary effect of Roll with Adverse Yaw. DB6 has described a good way of demonstrating this effect.
The way I was taught was to line up the nose with a feature, (we used a church steeple) then roll left and watch the nose move right compared to the feature. Similar the other way.
DB6 has it in one.
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Yes, adverse aileron yaw does happen... but when talking about the secondary effect of the ailerons, remember the following. Demonstrate a 30 degree angle of bank by moving the yoke left/right. The primary effect is roll... then due to the fact that lift is now no longer directly opposing lift, you get slip... this slipping results in a weathercock/fuselage effect. What happens now is that because you have more fuselage area behind the CofP the aircraft will yaw in the direction of the roll.
Adverse aileron yaw i.e. yaw out of turn is completely different to the secondary effect of the ailerons and they are caused by two completely different reasons.
Hope this helps
Adverse aileron yaw i.e. yaw out of turn is completely different to the secondary effect of the ailerons and they are caused by two completely different reasons.
Hope this helps
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Ooooooooooooppppppppppssssssssss
Oooooooooooooohhhhhhhhhh 
My apologies gentlemen, I missunderstood the question. Thought he was asking about adverse yaw.
I really must stop work and concentrate harder when doing important things like responding to Pprune.
Thank you for spotting my mistake.
My apologies gentlemen, I missunderstood the question. Thought he was asking about adverse yaw.
I really must stop work and concentrate harder when doing important things like responding to Pprune.
Thank you for spotting my mistake.
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Thank you for all your replies, especially DB6. I will try that next time and see how it goes.
Yes, demonstration of the secondary effects of Yaw is easy. Kick the rudder in with some force and the nose will yaw about the normal axis, followed by a roll about the longitudinal axis .
The secondary effects of Yaw is Roll.
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What happens now is that because you have more fuselage area behind the CofP the aircraft will yaw in the direction of the roll.
I always understood that when bank is applied by use of ailerons, the aircraft sideslips towards the lower wing. As a result of this sideslip the sideways pressure of air upon the keel surface of the fuselage behind the centre of gravity will tend to yaw the aircraft into the direction of the slip.
VFE.
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Slip and skid
Why is it argued that only the yaw resulting from slip is a secondary effect?
Adverse yaw is not always only as a result of 'adverse aileron drag'. Much has been done in aircraft design to eliminate aileron drag. Cessna introduced the 'Frise' concept in addition to 'differential' methods of eliminating adverse drag many years ago and although adverse aileron drag remains it can be minor. While each method only reduces the degree of adverse drag they do make the secondary effect of adverse yaw less of a consideration. The adverse yaw resulting from skid is still very marked though and must be understood and the skill of prevention practiced.
During roll the result of skid should be considered and in my view the original poster is quite correct to consider it. So we have two secondary effects from roll; Yaw resulting from slip and yaw resulting from skid (in addition to any aileron yaw). Slip is prevented by the the use of elevator (maintaining height) but the effects resulting from skid (in addition to any aileron drag) are prevented by the use of rudder simultaneous with the correct proportional use of aileron.
It follows then that both 'secondary effects must be demonstrated and understood.Too often I discover that the secondary effect resulting resulting from slip is covered and understood but an ignorance of the yaw resulting from skid continues. The lack of understanding of adverse yaw leads to over control and in-appropiate use of aileron, paricularly at the slower speeds during the approach, but not only.
Adverse yaw is not always only as a result of 'adverse aileron drag'. Much has been done in aircraft design to eliminate aileron drag. Cessna introduced the 'Frise' concept in addition to 'differential' methods of eliminating adverse drag many years ago and although adverse aileron drag remains it can be minor. While each method only reduces the degree of adverse drag they do make the secondary effect of adverse yaw less of a consideration. The adverse yaw resulting from skid is still very marked though and must be understood and the skill of prevention practiced.
During roll the result of skid should be considered and in my view the original poster is quite correct to consider it. So we have two secondary effects from roll; Yaw resulting from slip and yaw resulting from skid (in addition to any aileron yaw). Slip is prevented by the the use of elevator (maintaining height) but the effects resulting from skid (in addition to any aileron drag) are prevented by the use of rudder simultaneous with the correct proportional use of aileron.
It follows then that both 'secondary effects must be demonstrated and understood.Too often I discover that the secondary effect resulting resulting from slip is covered and understood but an ignorance of the yaw resulting from skid continues. The lack of understanding of adverse yaw leads to over control and in-appropiate use of aileron, paricularly at the slower speeds during the approach, but not only.
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Homeguard - possibly correct but a shade too complex at this stage; remember we are talking Effects of Controls 1 here. All that is required is to show Bloggs that if you deflect the ailerons the aircraft first rolls, then yaws for reasons described above (and if left uncorrected a spiral dive will result). Adverse aileron yaw can be demonstrated later - normally during CT&D 1 when teaching how to roll in and out of turns - but will just confuse matters at this stage.
JulieFlyGal - when demonstrating, a good technique is to just use one finger under the yoke (or against the stick) to avoid applying back pressure, as this can mask the effect. To explain to the student, mention how a dart will fall point-down when dropped; same principle but with wings to complicate things a bit.
JulieFlyGal - when demonstrating, a good technique is to just use one finger under the yoke (or against the stick) to avoid applying back pressure, as this can mask the effect. To explain to the student, mention how a dart will fall point-down when dropped; same principle but with wings to complicate things a bit.
Last edited by DB6; 3rd Oct 2008 at 18:36.
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Slip and Skid
DB6, it is not possibly correct, it is correct. The effect from skid is no more complex to understand than the effects resulting from slip.
Demonstrating both does not confuse it illuminates. After all, in the sequence of events once aileron is applied what happens first. Slip or adverse yaw?
Not to be forgotten is that a short period, after an angle of bank has been achieved, will elapse, owing to inertia, before the slip develops and yet after that before the further effect of yaw becomes apparent. The effects of adverse yaw take place almost immediately and during the rolling motion and will be the first effect that the student will experience. Ignoring some elements at the early stage only leads to confusion.
For instance the cause of the yaw from slip is easily cured by the use of elevator to maintain height. No more slip therefore no more yaw. It is too easy to leave the student confused: you say one thing but another differnet control has the desired effect.
Demonstrating both does not confuse it illuminates. After all, in the sequence of events once aileron is applied what happens first. Slip or adverse yaw?
Not to be forgotten is that a short period, after an angle of bank has been achieved, will elapse, owing to inertia, before the slip develops and yet after that before the further effect of yaw becomes apparent. The effects of adverse yaw take place almost immediately and during the rolling motion and will be the first effect that the student will experience. Ignoring some elements at the early stage only leads to confusion.
For instance the cause of the yaw from slip is easily cured by the use of elevator to maintain height. No more slip therefore no more yaw. It is too easy to leave the student confused: you say one thing but another differnet control has the desired effect.
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Slight thread drift, but unless you have QFE set and are demonstrating this over perfectly flat land would the elevator input not be used for maintaining "altitude"?
May as well get them used to the correct terms, ignoring some elements at the early stage only leads to confusion.
Granted, you could maintain *sufficient" height to avoid a CFIT report - but I doubt you would MAINTAIN any given HEIGHT.
May as well get them used to the correct terms, ignoring some elements at the early stage only leads to confusion.
Granted, you could maintain *sufficient" height to avoid a CFIT report - but I doubt you would MAINTAIN any given HEIGHT.
Have a re-read of your Principles of Flight - you have confused secondary effect of Roll with Adverse Yaw.
The problem is that it's more complex than just "primary" and "secondary" because it depends on where you start and what else is going on.
There's an effect of aileron deflection itself in creation of a yawing moment through "adverse yaw".
There's an effect of roll rate in creation of a yawing moment through differential induced drag on the wings due to different AoAs.
There's an effect of bank angle in creation of a yawing moment through creation of a sideslip angle and thus the effect of directional stability, if the sideslip is permitted to persist.
I'm also at a loss as to why you'd choose to demonstrate yaw in the vertical:
Raise the nose slightly above the horizon, roll the aircraft to about 30-40 degrees bank, and watch as the nose drops sideways back through the horizon.
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Good luck explaining all that in a 15 minute brief Bookworm!
You don't need to be a genius to realise that the above demonstration would work well set against the horizon which is the datum for exercise 4. What are you babbling on about with regards "the vertical"?? Trying to be clever?? 
VFE.
Raise the nose slightly above the horizon, roll the aircraft to about 30-40 degrees bank, and watch as the nose drops sideways back through the horizon.
VFE.
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book - I was always taught to say "FURTHER effect" rather than "secondary effect".
Was also taught that the results of control surface movements are to be viewed and referred to as relative to the pilot.
The fact that the nose of the aircraft is seen, in DB6's method, above and below the horizon does not represent movement in "the vertical". As VFE says - it's a potential 'datum' from which to observe that the movement does occur.
How do you address the third portion - that unchecked roll/yaw results in a spiral dive?
Was also taught that the results of control surface movements are to be viewed and referred to as relative to the pilot.
The fact that the nose of the aircraft is seen, in DB6's method, above and below the horizon does not represent movement in "the vertical". As VFE says - it's a potential 'datum' from which to observe that the movement does occur.
How do you address the third portion - that unchecked roll/yaw results in a spiral dive?
Lord love a duck, it isn't that hard...
Further effect of roll is sideslip, fin generates yaw. Teach with a little aeroplane model.
To demo, roll gently to about 30 deg bank and get the student to watch the relative 'downhill' movement of the nose.
Roll>sideslipe>yaw>roll>more sideslip>more yaw...and eventually a spiral descent. Demo on EoC1.
Adverse aileron yaw can be demonstrated by entering a normal 30 deg AoB turn, then getting the student to watch the motion of the nose as you roll rapidly to wings level. Much easier to demo it that way than trying to roll rapidly into a turn! But to be honest, that's a bit of a nicety as the student should, by the time such information becomes relevant, know that the ball must be kept in the middle!
Further effect of roll is sideslip, fin generates yaw. Teach with a little aeroplane model.
To demo, roll gently to about 30 deg bank and get the student to watch the relative 'downhill' movement of the nose.
Roll>sideslipe>yaw>roll>more sideslip>more yaw...and eventually a spiral descent. Demo on EoC1.
Adverse aileron yaw can be demonstrated by entering a normal 30 deg AoB turn, then getting the student to watch the motion of the nose as you roll rapidly to wings level. Much easier to demo it that way than trying to roll rapidly into a turn! But to be honest, that's a bit of a nicety as the student should, by the time such information becomes relevant, know that the ball must be kept in the middle!
Good luck explaining all that in a 15 minute brief Bookworm!
The fact that the nose of the aircraft is seen, in DB6's method, above and below the horizon does not represent movement in "the vertical". As VFE says - it's a potential 'datum' from which to observe that the movement does occur.