Sendary effect of rudder
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Sendary effect of rudder
Hi all, I am little confused about this phrase.
I do know what happens but do not know why...in details...
The secondary effect of yaw is roll due to the outer wing travels faster than the inner wing.
But how does it travel faster?? Is it because of the outer wing is more exposed to the Relative Airflow than the inner wing? If so, what is exposing got do with increase in velocity?
Anyone who can explain this??please? The simplest way?
I do know what happens but do not know why...in details...
The secondary effect of yaw is roll due to the outer wing travels faster than the inner wing.
But how does it travel faster?? Is it because of the outer wing is more exposed to the Relative Airflow than the inner wing? If so, what is exposing got do with increase in velocity?
Anyone who can explain this??please? The simplest way?
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I can see why you are confused.
the term is actually "the secondary effect of rudder"
ok lets give you a mental word picture to help you.
you are cruising along in straight and level flight, ok.
you pull back the throttle and the aircraft slows down, you trim in a little bit of up elevator to maintain altitude.
ok so you are now flying at a speed well below the manoeuvring speed for the aircraft, that is important for the following.
the centreline of the aircraft is aligned in the direction of flight, everything is in trim and you can take the hands off the controls and the natural stability of the aircraft will keep it flying along just peachy for a while.
ok you hold wings level and very quickly apply a boot full of rudder.
what happens next is that the deflection of the rudder creates air pressure changes to the fin and rudder which causes a force to be applied to the tail of the aircraft. conceptually the force is at the centre of pressure of the fin/rudder and acts horizontally. this horizontal force slews the body of the aircraft about the centre of gravity but the aircraft, at least momentarily, continues along in the original direction.
during this moment the aircraft is flying with one wing a little more forward than the other wing.
a number of things are now changed in regards the wing.
the fuselage will slightly blanket the trailing wing making the forward wing seem slightly longer and thus generate slightly more lift.
as well on wings that have dihedral the forward wing will be at a slightly higher angle of attack than the trailing wing and this will also slightly increase the lift from the forward wing.
you can see this for yourself next time you go flying. slow the aircraft to about 20 knots faster than the stall, get everything trimmed out and stable. then apply a boot full of rudder while looking out along the wing.
the secondary effect of rudder is worth understanding because on a lightie you can use the technique to pick up a dropping wing at the stall.
the term is actually "the secondary effect of rudder"
ok lets give you a mental word picture to help you.
you are cruising along in straight and level flight, ok.
you pull back the throttle and the aircraft slows down, you trim in a little bit of up elevator to maintain altitude.
ok so you are now flying at a speed well below the manoeuvring speed for the aircraft, that is important for the following.
the centreline of the aircraft is aligned in the direction of flight, everything is in trim and you can take the hands off the controls and the natural stability of the aircraft will keep it flying along just peachy for a while.
ok you hold wings level and very quickly apply a boot full of rudder.
what happens next is that the deflection of the rudder creates air pressure changes to the fin and rudder which causes a force to be applied to the tail of the aircraft. conceptually the force is at the centre of pressure of the fin/rudder and acts horizontally. this horizontal force slews the body of the aircraft about the centre of gravity but the aircraft, at least momentarily, continues along in the original direction.
during this moment the aircraft is flying with one wing a little more forward than the other wing.
a number of things are now changed in regards the wing.
the fuselage will slightly blanket the trailing wing making the forward wing seem slightly longer and thus generate slightly more lift.
as well on wings that have dihedral the forward wing will be at a slightly higher angle of attack than the trailing wing and this will also slightly increase the lift from the forward wing.
you can see this for yourself next time you go flying. slow the aircraft to about 20 knots faster than the stall, get everything trimmed out and stable. then apply a boot full of rudder while looking out along the wing.
the secondary effect of rudder is worth understanding because on a lightie you can use the technique to pick up a dropping wing at the stall.
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on a lightie you can use the technique to pick up a dropping wing at the stall.
Not a good practice, I suggest.
Standard rule with stalling is not to permit yaw ... stall+yaw leads to spin.
Not a good practice, I suggest.
Standard rule with stalling is not to permit yaw ... stall+yaw leads to spin.
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Yaw is rotation about the vertical axis. For this example, push the left rudder pedal.
As the airplane yaws to the left, the right wing is temporarily pushed forward, and the left wing is temporarily pushed aft, relative to the yaw axis. The temporary increase in speed of the right wing causes increased lift, while the temporary decrease in speed of the left wing causes decreased lift. Therefore the right wing rises, the left wing drops, and the airplane rolls. When the rudder is released, the opposite happens, and the airplane rolls upright again.
As the airplane yaws to the left, the right wing is temporarily pushed forward, and the left wing is temporarily pushed aft, relative to the yaw axis. The temporary increase in speed of the right wing causes increased lift, while the temporary decrease in speed of the left wing causes decreased lift. Therefore the right wing rises, the left wing drops, and the airplane rolls. When the rudder is released, the opposite happens, and the airplane rolls upright again.
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I hope none of you that are spouting this rubbish about the outside wing going faster are teaching it.
If you absolutely hoof the pedals you may get a little effect but most of it is due to a change to the angle of attack. Which direction depends if the wing is anhedral or dihedral.
If you absolutely hoof the pedals you may get a little effect but most of it is due to a change to the angle of attack. Which direction depends if the wing is anhedral or dihedral.
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If you "absolutely hoof the pedals" you will get an enhanced visual confirmation of the effect -- especially effective in a long-winged sailplane.
The OP asked for a simple explanation. Anhedral/dihedral, wing sweep, blanketing, and a host of other details complexify the explanation.
The OP asked for a simple explanation. Anhedral/dihedral, wing sweep, blanketing, and a host of other details complexify the explanation.
As the airplane yaws to the left, the right wing is temporarily pushed forward, and the left wing is temporarily pushed aft, relative to the yaw axis. The temporary increase in speed of the right wing causes increased lift, while the temporary decrease in speed of the left wing causes decreased lift. Therefore the right wing rises, the left wing drops, and the airplane rolls.
When explaining this to my students, I used to get a piece of A4 paper and fold it in half longitudinally. Put a slight bend in half way and then point it at the student getting him/her to say which side they can see more of when rotated in the yaw axis. Then explain that's the side with the greater angle of attack, more lift and why the aircraft will roll when yawed - assuming it wasn't the Extra! For those the other side of the Atlantic, letter will do instead of A4, - but the aspect ratio won't be so good!
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Hoof is rapid application of control input. In English and Scottish.
And thankfully I had already covered the topic in my engineering degree before my ppl faa instructor came out with is over simplistic rubbish.
The whole room of riddle instructors was then slightly disturbed as me and another engineer explained why it was rubbish. Give one his due he did go and read up on it and came and asked sensible questions after the initial shock went through them all that they had spent 100's of thousands of dollars to be taught in correct theory.
And thankfully I had already covered the topic in my engineering degree before my ppl faa instructor came out with is over simplistic rubbish.
The whole room of riddle instructors was then slightly disturbed as me and another engineer explained why it was rubbish. Give one his due he did go and read up on it and came and asked sensible questions after the initial shock went through them all that they had spent 100's of thousands of dollars to be taught in correct theory.
Last edited by mad_jock; 14th Jun 2014 at 07:44.
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2ndry affect of rudder.
Secondary Affect of Yaw.
anything on the outside travels faster. If you yaw right tail goes left reducing the airflow over the right wing right wing - Left wing goes faster because it has got its original forward speed through the sir - plus - an additional forward speed relative to the right wing - momentarily - as the aircraft yaws.
As the Left wing is going faster in relation to the right wing going slower - then:
There is more Lift on the Left wing - compared to less Lift on the right wing.
The Left wing goes up and the right wing goes down - - as you are helping things along but making, letting the aircraft Yaw, as well, then the aircraft rolls to the right.
Ok, only kidding - actually - am not - come forth ye critics with yer span-wise airflow and angle of attack - fair enough then.
Listen Dudes and Duedess-esses -
Smite us as ye may for saying its not a case of the left wing going faster and the other wing going slower - but do dive in with the pickys and the numbers - don't just say its ----, get on in there - life is short, right?
In other words: show us what you mean - (or go and make some tea)
Thank you for your time.
Re: Bootfuls - Don`t bootful anything - as JT says.
It is not the Brazilian World Cup - were not scoring for England here. Don`t "bootful" anything until you have been shown by an instructor and an aerobatic instructor at that.
As J.T rightly says - an appropriate, amount of rudder is to be used in the event of a wing drop - opposite rudder to the dropping wing - opposite rudder - so that if the Right wing drops, say, IN A STALL, then one would straighten the aircraft that is level the wings - not with the aileron - not with the aileron, but with opposite rudder, not "booting it in" - that's disgusting but apply sufficient rudder, even full rudder, momentarily, momentarily to recover the dropped wing - this is at the stall (or just after the wings have stalled - if the wing has suddenly dropped during the stall)
I won`t go into it - but the reason we do that is so as NOT to use aileron - why? Well using aileron during the stall to pick up the dropped wing can further stall the dropped wing - leading to a spin. If you are trained in spinning you will recover from an incipient spin - i.e., meaning - you will be trained to recover at the pre-stage or onset of the spin before it develops I mean - you will also be able to recover from a developed spin. In reality - if you get into a fully developed spin by accident then you are naughty to fly through a cyclone or you are half asleep or you should have left her on the ground and gone out for a pizza instead . . . . ?
You will get spin training at your local flying club/school as part of your PPL training.
Some of you fly so well that you are daft enough to go and spin - all on your own - why not?
I`ve spun with a student hundreds of times. Can`t quite get myself to do it solo though - seems like an insane way to fly. Unless you are an instructor or aerobatic pilot or a test pilot or a fighter pilot.
If you are not trained in spin recovery - then go and become trained in spin recovery - it may save your life one day.
Don`t put "bootfuls of rudder in" nobody does it - they are just being silly or un-learned.
Secondary Affect of Yaw.
anything on the outside travels faster. If you yaw right tail goes left reducing the airflow over the right wing right wing - Left wing goes faster because it has got its original forward speed through the sir - plus - an additional forward speed relative to the right wing - momentarily - as the aircraft yaws.
As the Left wing is going faster in relation to the right wing going slower - then:
There is more Lift on the Left wing - compared to less Lift on the right wing.
The Left wing goes up and the right wing goes down - - as you are helping things along but making, letting the aircraft Yaw, as well, then the aircraft rolls to the right.
Ok, only kidding - actually - am not - come forth ye critics with yer span-wise airflow and angle of attack - fair enough then.
Listen Dudes and Duedess-esses -
Smite us as ye may for saying its not a case of the left wing going faster and the other wing going slower - but do dive in with the pickys and the numbers - don't just say its ----, get on in there - life is short, right?
In other words: show us what you mean - (or go and make some tea)
Thank you for your time.
Re: Bootfuls - Don`t bootful anything - as JT says.
It is not the Brazilian World Cup - were not scoring for England here. Don`t "bootful" anything until you have been shown by an instructor and an aerobatic instructor at that.
As J.T rightly says - an appropriate, amount of rudder is to be used in the event of a wing drop - opposite rudder to the dropping wing - opposite rudder - so that if the Right wing drops, say, IN A STALL, then one would straighten the aircraft that is level the wings - not with the aileron - not with the aileron, but with opposite rudder, not "booting it in" - that's disgusting but apply sufficient rudder, even full rudder, momentarily, momentarily to recover the dropped wing - this is at the stall (or just after the wings have stalled - if the wing has suddenly dropped during the stall)
I won`t go into it - but the reason we do that is so as NOT to use aileron - why? Well using aileron during the stall to pick up the dropped wing can further stall the dropped wing - leading to a spin. If you are trained in spinning you will recover from an incipient spin - i.e., meaning - you will be trained to recover at the pre-stage or onset of the spin before it develops I mean - you will also be able to recover from a developed spin. In reality - if you get into a fully developed spin by accident then you are naughty to fly through a cyclone or you are half asleep or you should have left her on the ground and gone out for a pizza instead . . . . ?
You will get spin training at your local flying club/school as part of your PPL training.
Some of you fly so well that you are daft enough to go and spin - all on your own - why not?
I`ve spun with a student hundreds of times. Can`t quite get myself to do it solo though - seems like an insane way to fly. Unless you are an instructor or aerobatic pilot or a test pilot or a fighter pilot.
If you are not trained in spin recovery - then go and become trained in spin recovery - it may save your life one day.
Don`t put "bootfuls of rudder in" nobody does it - they are just being silly or un-learned.
Last edited by Natstrackalpha; 14th Jun 2014 at 08:55.
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The whole room of riddle instructors was then slightly disturbed as me and another engineer explained why it was rubbish. Give one his due he did go and read up on it and came and asked sensible questions after the initial shock went through them all that they had spent 100's of thousands of dollars to be taught in correct theory.
I was always very humble when having students with deeper knowledge than myself and tried to use them as a resource in teaching for the benefit of myself and other students.
There are lots of myths out there still being taught as reality by thouse who should know better. The danger of downwind turn springs to mind..
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There is great tendency always to 'compartmentalise' this sort of thing and say "It ia just X" or "Just Y" rather like the pundits on the topic of what controls airspeed and RofD and as with everything it is nearly always a combination of effects.
I appreciate the OP asked for 'simple', so faster wing is the best, but yes, there are several factors, and no-one has yet mentioned roll due to fin sideslip yet
(and to get really technical, there is the small roll moment generated by rudder displacement alone...) An a/c with anhedral WILL experience a rolling moment in yaw due to differential wing speeds but it may well be masked by other effects.
I appreciate the OP asked for 'simple', so faster wing is the best, but yes, there are several factors, and no-one has yet mentioned roll due to fin sideslip yet
(and to get really technical, there is the small roll moment generated by rudder displacement alone...) An a/c with anhedral WILL experience a rolling moment in yaw due to differential wing speeds but it may well be masked by other effects.
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NATSTRACK - not sure where you are, but certainly in the UK picking the wing up on stall went out years ago, current teaching is to prevent further yaw with rudder, but you do NOT pick the wing up, wings are rolled level - with aileron, once OUT of the stall.
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Putting aside very old certifications, most reasonably recent designs are required to be able to accept aileron input during stall activity.
Indeed, some, for example the larger KingAirs, generally require lots of aileron activity to achieve the required certification sequence during a stall recovery.
For those of us mere mortals (ie not aerobatic experts) it is not essential to get the wings level in an instant .. more important to unstall and then worry about the other niceties, I suggest.
See, for instance, in FAR 23.201 -
(d) During the entry into and the recovery from the maneuver, it must be possible to prevent more than 15 degrees of roll or yaw by the normal use of controls except as provided for in paragraph (e) of this section.
(e) For airplanes approved with a maximum operating altitude at or above 25,000 feet during the entry into and the recovery from stalls performed at or above 25,000 feet, it must be possible to prevent more than 25 degrees of roll or yaw by the normal use of controls.
Indeed, some, for example the larger KingAirs, generally require lots of aileron activity to achieve the required certification sequence during a stall recovery.
For those of us mere mortals (ie not aerobatic experts) it is not essential to get the wings level in an instant .. more important to unstall and then worry about the other niceties, I suggest.
See, for instance, in FAR 23.201 -
(d) During the entry into and the recovery from the maneuver, it must be possible to prevent more than 15 degrees of roll or yaw by the normal use of controls except as provided for in paragraph (e) of this section.
(e) For airplanes approved with a maximum operating altitude at or above 25,000 feet during the entry into and the recovery from stalls performed at or above 25,000 feet, it must be possible to prevent more than 25 degrees of roll or yaw by the normal use of controls.
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john tullamarine the original poster is a newbie asking a basic question.
so I ask you who in hell does basic training in a king air??
in the strident effort to be top dog you guys loose the plot sometimes.
the aircraft I had in mind with the explanation was the Cessna 150. the Cessna 152 will perform the manoeuvre as well as will a piper cherokee.
back in my training days the pick up the wing exercise was used as a skill builder.
so I ask you who in hell does basic training in a king air??
in the strident effort to be top dog you guys loose the plot sometimes.
the aircraft I had in mind with the explanation was the Cessna 150. the Cessna 152 will perform the manoeuvre as well as will a piper cherokee.
back in my training days the pick up the wing exercise was used as a skill builder.
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And now it's actively discouraged in flight training.
There absolutely no problem what's so ever using full rudder deflection on an Airbus as long as your in the envelope to do so. What you can't do is cycle it max deflection from either side trying to lift the wing in a flight upset. Exactly the same as Boeing and any other aircraft type. Including c150 pa28 and other training types.
The problem with teaching rubbish is that it becomes the default rubbish which everyone believes. If you teach people the correct thing from the beginning then there is never any problem. Just like this pick the wing up with the rudder pish an aircraft and pax is also dead because of it. And people still think it's because of a defective design and not a defective method of controlling an aircraft.
The fact that nothing could have survived a cyclic load input that was applied to that tail doesn't matter.
And we were not smug at the time, genuinely confused because it was such a load of rubbish. The rate of application and the amount of yaw to get a significant induced roll moment is huge. And sail planes are the aircraft which you can get it to work in due to the span of the wing acting as a displacement amplifiyer and the relatively powerfully rudder.
Thinking that a 5 deg yaw squeeze by a student is going to give anything like the amount of roll effect that happens is just stupid.
The amount of control input should be appropriate to get the effect you want. Fixed wing powered it's going to be small, glider not so small in fact it feels huge some might say boot full compared to a light training aircraft.
There absolutely no problem what's so ever using full rudder deflection on an Airbus as long as your in the envelope to do so. What you can't do is cycle it max deflection from either side trying to lift the wing in a flight upset. Exactly the same as Boeing and any other aircraft type. Including c150 pa28 and other training types.
The problem with teaching rubbish is that it becomes the default rubbish which everyone believes. If you teach people the correct thing from the beginning then there is never any problem. Just like this pick the wing up with the rudder pish an aircraft and pax is also dead because of it. And people still think it's because of a defective design and not a defective method of controlling an aircraft.
The fact that nothing could have survived a cyclic load input that was applied to that tail doesn't matter.
And we were not smug at the time, genuinely confused because it was such a load of rubbish. The rate of application and the amount of yaw to get a significant induced roll moment is huge. And sail planes are the aircraft which you can get it to work in due to the span of the wing acting as a displacement amplifiyer and the relatively powerfully rudder.
Thinking that a 5 deg yaw squeeze by a student is going to give anything like the amount of roll effect that happens is just stupid.
The amount of control input should be appropriate to get the effect you want. Fixed wing powered it's going to be small, glider not so small in fact it feels huge some might say boot full compared to a light training aircraft.
Last edited by mad_jock; 14th Jun 2014 at 18:04.
I was going to keep out of this one, because I knew it would turn into a pxxxxxg contest, but I can't help but chip in and say that I am entirely with MJ and JT on this.
Guys. Please stop telling people (especially students) that they should 'pick up the downgoing wing with the rudder', during and beyond the stall.
The rudder should be used to prevent further yaw, whilst, at the same time, stopping the wing drop by un-stalling the wings.
Then, after you have un-stalled the wings, level the wings with co-ordinated use of aileron and rudder!
Guys. Please stop telling people (especially students) that they should 'pick up the downgoing wing with the rudder', during and beyond the stall.
The rudder should be used to prevent further yaw, whilst, at the same time, stopping the wing drop by un-stalling the wings.
Then, after you have un-stalled the wings, level the wings with co-ordinated use of aileron and rudder!
Last edited by Mach Jump; 14th Jun 2014 at 15:51. Reason: Punctuation
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so I ask you who in hell does basic training in a king air??
.. methinks you may have missed the point of my post .. ? if so, my apologies for any confusion arising from my text.
The KingAir just happens to be an example for which I know, specifically, the requirement applies. Indeed, you won't achieve the OEM's stall figures without aileron input and some knowledge of the relevant certification technique ..
The concern with this thread is not the training/competence/licence level of any given pilot .. rather an outdated, and generally incorrect, belief that applies as much to the 20,000 hour pro as to the 10 hour first solo trainee ..
.. methinks you may have missed the point of my post .. ? if so, my apologies for any confusion arising from my text.
The KingAir just happens to be an example for which I know, specifically, the requirement applies. Indeed, you won't achieve the OEM's stall figures without aileron input and some knowledge of the relevant certification technique ..
The concern with this thread is not the training/competence/licence level of any given pilot .. rather an outdated, and generally incorrect, belief that applies as much to the 20,000 hour pro as to the 10 hour first solo trainee ..
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John - it would seem this thread is going to 'run wild' away from the OP so I will take the opportunity to ask
.
How is this achieved? Are the basic rules of aerodynamics (use of aileron on a fully stalled wing causes that wing to drop) re-written or is, perhaps, the King Air 'stall' for certification purposes not a 'stall' as such but an incipient stall? One of the essential exercises in training is (used to be!) to demonstate wingdrop if aileron is used on a stalled wing. Does the KingAir have roll spoilers perhaps? A 'standard' basic aircraft will definitely enter an incipient spin if aileron is used and this lesson needs to be re-inforced. It will be highly dangerous if the new pilots go away with the idea that aileron is 'ok'.
Indeed, some, for example the larger KingAirs, generally require lots of aileron activity to achieve the required certification sequence during a stall recovery.
How is this achieved? Are the basic rules of aerodynamics (use of aileron on a fully stalled wing causes that wing to drop) re-written or is, perhaps, the King Air 'stall' for certification purposes not a 'stall' as such but an incipient stall? One of the essential exercises in training is (used to be!) to demonstate wingdrop if aileron is used on a stalled wing. Does the KingAir have roll spoilers perhaps? A 'standard' basic aircraft will definitely enter an incipient spin if aileron is used and this lesson needs to be re-inforced. It will be highly dangerous if the new pilots go away with the idea that aileron is 'ok'.