Dissymmetry of lift, flapping and blowback...
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DB !
DB: "no idea what the bades are doing."
do you mean blades or 'babes'?
either way I am sure "no idea" is slightly overstating your confusion - but then you don't actually need to know much in order to have quite a fruitful career, as you have proved. After a beverage or 2 pilots can pronounce blades as bades but to spell it that way too must take an extra night cap.
"Still waiting" ...really!? - I have answered Cb on experience and background - he is making it circular - it is not relevant - only the merit of the points in their own right has importance here - besides he published my pm previously.
do you mean blades or 'babes'?
either way I am sure "no idea" is slightly overstating your confusion - but then you don't actually need to know much in order to have quite a fruitful career, as you have proved. After a beverage or 2 pilots can pronounce blades as bades but to spell it that way too must take an extra night cap.
"Still waiting" ...really!? - I have answered Cb on experience and background - he is making it circular - it is not relevant - only the merit of the points in their own right has importance here - besides he published my pm previously.
Last edited by AnFI; 15th Sep 2013 at 08:06.
So, still hiding behind bluster then AnFI - you might have some credibility if you actually came out with your credentials (unless they don't exist) but you keep making confusing posts in answer to straightforward questions from newbies.
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respectively I say..
It must be more confusing for the newbie to receive your self admittedly erroneous post.
And furthermore I do not want to derive credibility, as you think I should, from credentials.
And I still maintain that the view I am espousing is a simple one:
In a nutshell: If for (almost) any reason the lift distribution around the disc is not equal then the ability of blades to flap would equalise it but in practice really just provides the cue that the cyclic position must be changed (and the magic bit) to a place where that inequality no longer exists, and no longer requires flapping to equalise the lift.
This encompasses a variety of effects: Speed inequality (DofLift), inflow roll, cliff recirculation etc
So more simply stated : the pilot holds the stick where he needs to (providing unequal pitch) so that flapping is not needed to equalise lift.
If you don't agree or don't think that's an insight then I'd be happy to hear an alternative explanation.
(Of course there is the red herring of hinge offset and pitch-flap coupling - but they are unnecessary complications at this level)
And furthermore I do not want to derive credibility, as you think I should, from credentials.
And I still maintain that the view I am espousing is a simple one:
In a nutshell: If for (almost) any reason the lift distribution around the disc is not equal then the ability of blades to flap would equalise it but in practice really just provides the cue that the cyclic position must be changed (and the magic bit) to a place where that inequality no longer exists, and no longer requires flapping to equalise the lift.
This encompasses a variety of effects: Speed inequality (DofLift), inflow roll, cliff recirculation etc
So more simply stated : the pilot holds the stick where he needs to (providing unequal pitch) so that flapping is not needed to equalise lift.
If you don't agree or don't think that's an insight then I'd be happy to hear an alternative explanation.
(Of course there is the red herring of hinge offset and pitch-flap coupling - but they are unnecessary complications at this level)
Last edited by AnFI; 15th Sep 2013 at 10:10.
No, strangely enough, it's not an insight to say that the pilot has to move the cyclic in order to control the helicopter!
Is that your magic secret??????FFS
Many thousands of instructors have taught even more thousands (or millions) of people to fly a helicopter by moving the cyclic so that the aircraft goes in the direction you want it to - try 'select and maintain an attitude' as simple method of overcoming flapback, inflow roll - it works and doesn't hide behind some pseudo-science ramblings about flapping.
My error on the R22 lateral spring was an honest one - I don't think I am beyond being corrected, unlike you.
Is that your magic secret??????FFS
Many thousands of instructors have taught even more thousands (or millions) of people to fly a helicopter by moving the cyclic so that the aircraft goes in the direction you want it to - try 'select and maintain an attitude' as simple method of overcoming flapback, inflow roll - it works and doesn't hide behind some pseudo-science ramblings about flapping.
My error on the R22 lateral spring was an honest one - I don't think I am beyond being corrected, unlike you.
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Mr CRAB, an error, tut tut. I suggest you give yourself a damn good thrashing. I did.
You get the same effect as reading "ANFIs World Of Helicopter Magic Insights" without the mental strain of trying to workout the more difficult PoF concepts like "Ascendingbroomstick" effect!!
DB
You get the same effect as reading "ANFIs World Of Helicopter Magic Insights" without the mental strain of trying to workout the more difficult PoF concepts like "Ascendingbroomstick" effect!!
DB
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stick to the point
A) no ... the trim direction was not the only error ... the direction of the swash plate movement was the other. With those two errors in mind I would think it was fairer to say your posts were more confusing to the 'newbie' wouldn't you concede?
B) I said: if you had an alternative view point please make it.
DB ... of course you are right you can just yank the sticks around and it works pretty well.
I hope this is a place where a straight conversation on the point can be genuinely made?
B) I said: if you had an alternative view point please make it.
DB ... of course you are right you can just yank the sticks around and it works pretty well.
I hope this is a place where a straight conversation on the point can be genuinely made?
No, your direction of swash plate movement is specific to a helo that has a 90 degree advance angle (like the R22) - my swash plate movement was of a generic helicopter without any advance angle or jack offset, I did explain that clearly but again you weren't listening.
When I make a mistake, I a. admit it and b. try to explain how that mistake came about - you don't either admit or explain, just BS.
When I make a mistake, I a. admit it and b. try to explain how that mistake came about - you don't either admit or explain, just BS.
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let's be nice
and for completeness the third fundamental error which made your posts confusing was "the fact that AoAs are always bigger on the advancing side" yes you did admit you were wrong about that too, but it does add up to confusion. (AND We were talking about the R22 where the swash plate moves not in the direction you stated)
Of course if I am wrong about what I say I'd be delighted to correct my simple and effective model and admit any errors... I like discovering (my) errors it means improvement and learning.
(It might help to describe these things with respect to the Zero pitch (change) plane - but I doubt it!)
Of course if I am wrong about what I say I'd be delighted to correct my simple and effective model and admit any errors... I like discovering (my) errors it means improvement and learning.
(It might help to describe these things with respect to the Zero pitch (change) plane - but I doubt it!)
Is there still a question to be answered here??? I tried to follow along to provide some insight to the OP's question. But now im lost as to the real topic here. it is my belief that the question was just worded poorly. I also believe that it is referring to dissymmetry of lift. one question to ask yourself is "At what point does it become the Advancing Blade?" The way i teach is once it passes over the tail it is the advancing blade, and begins to see an increase in relative wind, this increase "peaks" at the 3 or 9 clock position(dependent on type) and then begins to lose this extra airspeed until passing the nose. SO... if we assume straight and level - unaccelerated flight at say "50 knots". then we can dissect what is happening. lets assume the pilot doesnt make any inputs. If the helicopter airspeed increases due to external factors to 60 knots, the advancing blade will have an increase in Velocity due to this increase in speed, this produces a potential for more lift. The Potential increase in lift will cause the blade to flap up (to equality) as it travels around the advancing side of the aircraft and it reaches its peak at the nose and begins to flap down from this high point all the way to the tail which will be its low point. This causes a nose pitch up moment and the aircraft will try to slow itself down to its trimmed speed over a series of "ups and downs". Now this is a perfect world account of whats happening. this is not what actually happens in real life. first of all, no pilot will just allow the aircraft to pitch up when they sense an increase in speed. and few helicopter rotor systems exhibit this perfect stability. but in terms of the original Question, it is NOT increasing in lift(because it flapped to equality). it is NOT increasing drag for the same reason. but it IS "Going to the highest point". sorry this went so long... but it is freshman level aerodynamics, and many pilots dont have a good grasp on it.
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play the ball. ..
Do you actually disagree with me anyway?
I had thought you believed that Flapping was responsible for nullifying the lift dissymetry arising from speed differences etc Whereas I believe that the dissymetry of pitch is fundamentally responsible for cancelling dissymetries and that does represent a change in thinking on the topic.
Anyone actually disagree?
Please stick to genuine discussion of the points.
I had thought you believed that Flapping was responsible for nullifying the lift dissymetry arising from speed differences etc Whereas I believe that the dissymetry of pitch is fundamentally responsible for cancelling dissymetries and that does represent a change in thinking on the topic.
Anyone actually disagree?
Please stick to genuine discussion of the points.
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yes armyavi8or - that is the classic view
...further to that look at what holding the stick further forwards achieves - it achieves a flatter pitch on the advancing side and an increased pitch on the retreating side - this eliminates the need for flapping to equality to nullify that unequal lift due to unequal speeds.
without getting into the weeds. for a given airspeed, there is a corresponding cyclic position(fore/aft) that allows the aircraft to remain at that airspeed. your average pilot, will continually adjust this "trimmed" position to maintain the desired cruise speed or fuselage attitude. if the aircraft builds up excessive speed, and the pilot doesnt notice it, it will naturally flap to equality, and try to recover to its trimmed speed.(based on cyclic position) so, at any point in flight, you can say that due to FLAPPING, the Pilot must reposition the cyclic forward or aft to maintain the desired attitude/airspeed. one factor is a direct result of the other. and yes, forward cyclic will wash out the flapping tendency of the rotor system so that it may accelerate to the new desired airspeed.
ArmyAV8r - you are wasting your time with the troll known as AnFI - his new and original take on helicopter P of F is nothing more than a deliberately obtuse argument - we say chicken before the egg and he argues egg before the chicken.
He has no new information, no mystical insight and certainly no technical knowledge above and beyond yours or mine, no matter what he might claim - we say flapping occurs due to inequalities of lift and is corrected by the pilot with cyclic - he says moving the cyclic prevents flapping from occurring.
He likes to think this makes him cleverer than the rest of us and that he has 'discovered' some hitherto unknown secret of aerodynamics.
AnFI's P of F is like one of those secret weight loss technique books that promises new and original methods, guaranteed to give results - however, after pages and pages of guff and bluster, turns out to be eat less and do more exercise.
He did the same with VFR flight in poor weather conditions on a previous thread.
And still he is too ashamed to put his instructional qualifications up for public scrutiny - much like many of the weight-loss quacks.
He has no new information, no mystical insight and certainly no technical knowledge above and beyond yours or mine, no matter what he might claim - we say flapping occurs due to inequalities of lift and is corrected by the pilot with cyclic - he says moving the cyclic prevents flapping from occurring.
He likes to think this makes him cleverer than the rest of us and that he has 'discovered' some hitherto unknown secret of aerodynamics.
AnFI's P of F is like one of those secret weight loss technique books that promises new and original methods, guaranteed to give results - however, after pages and pages of guff and bluster, turns out to be eat less and do more exercise.
He did the same with VFR flight in poor weather conditions on a previous thread.
And still he is too ashamed to put his instructional qualifications up for public scrutiny - much like many of the weight-loss quacks.
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av8or - quite right
yup av8r, on the button, Flapping gives the Flap-back cue which gives the pilot the cue to move the cyclic which eliminates flapping by running the appropriately asymmetric pitch. That moves the thinking on - a little bit, which I think Cb is coming round to gradually.
Crab - that is an outrageously rude and uncalled for personal attack which has nothing to do with the merit of the discussion - I'll probably get in trouble again for YOUR rudeness. "troll, obtuse, ashamed, weight loss quack" - have some dignity man - you are wrong to be so rude and you should admit that error too - perhaps even apologise
Crab - that is an outrageously rude and uncalled for personal attack which has nothing to do with the merit of the discussion - I'll probably get in trouble again for YOUR rudeness. "troll, obtuse, ashamed, weight loss quack" - have some dignity man - you are wrong to be so rude and you should admit that error too - perhaps even apologise
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ANFI just let us know, are you a Flight Instructor (H) and if so what qualifications do you hold.
You should appreciate that your posts are a bit child-like in explanation to most of us on this forum and read a bit like Born Again Christianity. Like you stumbled upon God and need to share this amazing news with the rest of the world.
More importantly, the PofF for rotorcraft recognise that all descriptions are only applicable to a finite blade chord segment somewhere along the blade span, at one point around the disc, for one assumed set of conditions. That is why they are "Principles" and actually do not really reflect what is happening as the blade(s) travel around the head.
However, I have to say your marvel and wonder at how this actually all works is commendable and maybe Crab should cut you some slack and just enjoy your utter enthusiasm, for a subject that most of us have long forgotten, for what it actually is. The seemingly miraculous wonder of rotary flight!!
How bout it Mr Crab!!
DB
You should appreciate that your posts are a bit child-like in explanation to most of us on this forum and read a bit like Born Again Christianity. Like you stumbled upon God and need to share this amazing news with the rest of the world.
More importantly, the PofF for rotorcraft recognise that all descriptions are only applicable to a finite blade chord segment somewhere along the blade span, at one point around the disc, for one assumed set of conditions. That is why they are "Principles" and actually do not really reflect what is happening as the blade(s) travel around the head.
However, I have to say your marvel and wonder at how this actually all works is commendable and maybe Crab should cut you some slack and just enjoy your utter enthusiasm, for a subject that most of us have long forgotten, for what it actually is. The seemingly miraculous wonder of rotary flight!!
How bout it Mr Crab!!
DB
Last edited by DOUBLE BOGEY; 16th Sep 2013 at 01:57.
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Credit where due
Thanks DB.
Yes the helicopter is deeply beautiful and maligned by the confused and i am very enthusiastic about the Principle and Practice of Flight.
The reason for the baby language was that i was previously 'accused' of over-complicating.
Whilst: "PofF for rotorcraft recognise that all descriptions are only applicable to a finite blade chord segment somewhere along the blade span, at one point around the disc, for one assumed set of conditions" - can be true, in this case it is not true since a half cycle integral of 'Flapping' for a whole blade can be observed in the real world as as change of plane of rotation.
The CAA for example use 2 definitions for Flapping and Crab has used a 3rd definition elsewhere - without agreement on terminology it is easy to see how folks can get emotional.
The credentials are off limits I am afraid.
Crab purports to be an upstanding member of HM forces and an Honourable fellow - his behaviour does not match that - and he accuses me of being a troll!
(But would you kindly give me the definition of flapping which you use.)
Yes the helicopter is deeply beautiful and maligned by the confused and i am very enthusiastic about the Principle and Practice of Flight.
The reason for the baby language was that i was previously 'accused' of over-complicating.
Whilst: "PofF for rotorcraft recognise that all descriptions are only applicable to a finite blade chord segment somewhere along the blade span, at one point around the disc, for one assumed set of conditions" - can be true, in this case it is not true since a half cycle integral of 'Flapping' for a whole blade can be observed in the real world as as change of plane of rotation.
The CAA for example use 2 definitions for Flapping and Crab has used a 3rd definition elsewhere - without agreement on terminology it is easy to see how folks can get emotional.
The credentials are off limits I am afraid.
Crab purports to be an upstanding member of HM forces and an Honourable fellow - his behaviour does not match that - and he accuses me of being a troll!
(But would you kindly give me the definition of flapping which you use.)
Last edited by AnFI; 16th Sep 2013 at 06:46.
AnFI - Having read back through this thread, and your lovely PM, I have to agree that you are enthusiastic about your P of F and you may know more about aerodynamics than me but, if that is the case, you have a huge difficulty in explaining yourself in clear terms.
That shortcoming would lead me to believe your PPrune handle of AnFI, apart from being grammatically incorrect (vis - a flying instructor not an flying instructor) means you don't have any instructional qualifications - backed up by your assertions that
If you really as good as you say you are, come out with the truth and enlighten everyone, in clear and unambiguous terms.
The P of F which I use to try and explain things to newbies like baobab (where we started in post#40) is a simple explanation of things that occur and not in any way mathematical proof of the complexities of a rotor system. That P of F has been tried and tested over many years in many parts of the world because learning and understanding what actually happens in a rotor system requires degree level maths and a lot of study.
The simple concepts of flapping to equality and dissymmetry of lift are taught from the viewpoint of what happens to the blades if an inequality is introduced - without adding the complication of needing to move the controls to create that inequality. Once the effect is understood, then the action of moving the controls to compensate for the effect can be considered, such that you get the idea that either your autopilot or your right hand reacts to a change in attitude which has been brought about by an inequality of lift.
If you insist on saying that keeping the cyclic in the correct place ensures that there is no inequality, you are technically correct but ignore a huge chunk of understanding that is required by the student.
That shortcoming would lead me to believe your PPrune handle of AnFI, apart from being grammatically incorrect (vis - a flying instructor not an flying instructor) means you don't have any instructional qualifications - backed up by your assertions that
The credentials are off limits I am afraid.
The P of F which I use to try and explain things to newbies like baobab (where we started in post#40) is a simple explanation of things that occur and not in any way mathematical proof of the complexities of a rotor system. That P of F has been tried and tested over many years in many parts of the world because learning and understanding what actually happens in a rotor system requires degree level maths and a lot of study.
The simple concepts of flapping to equality and dissymmetry of lift are taught from the viewpoint of what happens to the blades if an inequality is introduced - without adding the complication of needing to move the controls to create that inequality. Once the effect is understood, then the action of moving the controls to compensate for the effect can be considered, such that you get the idea that either your autopilot or your right hand reacts to a change in attitude which has been brought about by an inequality of lift.
If you insist on saying that keeping the cyclic in the correct place ensures that there is no inequality, you are technically correct but ignore a huge chunk of understanding that is required by the student.
Avoid imitations
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The credentials are off limits I am afraid.
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Closure
Thanks Crab I am pleased that you now agree.
"understanding what actually happens in a rotor system requires degree level maths and a lot of study." Yes I have found that it helps.
Grammar/decode - debatable.
I'm not going to keep re-stating it anymore - sorry if it's not clear - maybe a re-read?
Thanks for being a decent chap in the end.
( Regarding how students are taught: Control is a (feedback) loop - it needs closure - DoL, Flap to Eq, Fl back, Cyclic Pitch change; resulting in a loop-closing elimination of the DoL.
This is a basic understanding of how to fly and is not taught in the basic art at the moment.
The alternative which DB identifies well is the 'wiggle the stick around to achieve a pleasing view' which seems to work quite well, to a point)
"understanding what actually happens in a rotor system requires degree level maths and a lot of study." Yes I have found that it helps.
Grammar/decode - debatable.
I'm not going to keep re-stating it anymore - sorry if it's not clear - maybe a re-read?
Thanks for being a decent chap in the end.
( Regarding how students are taught: Control is a (feedback) loop - it needs closure - DoL, Flap to Eq, Fl back, Cyclic Pitch change; resulting in a loop-closing elimination of the DoL.
This is a basic understanding of how to fly and is not taught in the basic art at the moment.
The alternative which DB identifies well is the 'wiggle the stick around to achieve a pleasing view' which seems to work quite well, to a point)
Last edited by AnFI; 16th Sep 2013 at 08:41.