Helicopter Dynamics: Gyroscopic Precession
Cliff recirculation - have you ever hovered next to a cliff? I get to do it a lot and there is no discernible tendency for the aircraft to move towards the cliff, regardless of what theory might predict.
ANy Fool Is smart enuf to see that...
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All noise Fcukall Insight
...but damned good!
Seems we're all out of step, chaps. What we're privileged to be experiencing here is AlterNative Flight Instruction.
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Yes AC 'precessing' of the cliff recirculation would be at 90deg - if even detectable above the normal attitude correction inputs from the pilot. It was a point of misunderstanding that Crab has learnt here (unlike the CFS notes of his generation, which had people being 'sucked into the cliff'), as were the other points. Yes my point initially was that of CoP moving with Asymetric aerofoils - crab refuted it (with the Gazelle point) etc you're making fun of the wrong person. Furthermore he thought that IIMC was just an inevitable consequence of flight in bad weather. And he put up an arguement along with allsorts of nonsense arguements about people being caught in Vortex ring for numbers of thousands of feet. All ridiculous ideas. Mostly now modified by him through learning here. and as far as i recall crab started out as a 90deg gyroscopic precession proponant before participating here.
Dissymetry of Lift is eliminated by Cyclically Varying Pitch - not Flapping to Equality. Clear enough for you?
(failed to make myself understood by you perhaps. you are still wrong. and argued all sorts of nonsense about flapping referenced to the control plane - which is not a normal reference for flapping. Wouldn't answer the question about which reference for flapping you use.)
Furthermore the descent into name calling is where crab normally goes when he gets himself in a muddle. Don't debase yourself AC you normally are one of the few who makes technical sense.
Dissymetry of Lift is eliminated by Cyclically Varying Pitch - not Flapping to Equality. Clear enough for you?
(failed to make myself understood by you perhaps. you are still wrong. and argued all sorts of nonsense about flapping referenced to the control plane - which is not a normal reference for flapping. Wouldn't answer the question about which reference for flapping you use.)
Furthermore the descent into name calling is where crab normally goes when he gets himself in a muddle. Don't debase yourself AC you normally are one of the few who makes technical sense.
Last edited by AnFI; 26th Mar 2014 at 23:12.
AnFi - there is a saying that goes 'when you are in a hole, stop digging' - you appear to have grabbed the keys to the JCB and started the next channel tunnel.
Your last post could be politely called 'creative remembering' but I can't be bothered to refute such garbage.
You are in the process of making an ar*e of yourself on 2 or 3 threads at the moment - your delusional belief that you alone know the answers to everything related to helicopter flying and that everyone else is wrong is rather worrying - unless it is just trolling.
If you look back on our several encounters, you may note that I am not afraid to admit where I have made errors - can you say the same about yourself???
To err is human, to keep shifting the argument because you cannot lose face is just pitiful - perhaps you should be a politician.
As we KEEP coming back to, publish your experience and qualifications and SOMEONE might take you seriously - until then, keep expecting the sort of replies you are getting as Lu Zuckerman II.
Your last post could be politely called 'creative remembering' but I can't be bothered to refute such garbage.
You are in the process of making an ar*e of yourself on 2 or 3 threads at the moment - your delusional belief that you alone know the answers to everything related to helicopter flying and that everyone else is wrong is rather worrying - unless it is just trolling.
If you look back on our several encounters, you may note that I am not afraid to admit where I have made errors - can you say the same about yourself???
To err is human, to keep shifting the argument because you cannot lose face is just pitiful - perhaps you should be a politician.
As we KEEP coming back to, publish your experience and qualifications and SOMEONE might take you seriously - until then, keep expecting the sort of replies you are getting as Lu Zuckerman II.
This thread is becoming a double-decaf soy latte - known as a "Why Bother?"
There ain't no point responding to Lu AnFi or awblain Zuckerman any more.
Anybody else got something sensible to say about the procession of the blades around their control orbit? Otherwise, let this thread sink into the Zuckerman Swamp of Misinformation and "I don't buy it".
There ain't no point responding to Lu AnFi or awblain Zuckerman any more.
Anybody else got something sensible to say about the procession of the blades around their control orbit? Otherwise, let this thread sink into the Zuckerman Swamp of Misinformation and "I don't buy it".
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Crab rude as ever. The merit (or lack of it) is in the arguement not the CV of the one who states it (I might well have no helicopter experience or knowledge), this is supposed to be anonymous and I don't wish to divulge and you should respect that and stop banging the same old boring drum. Where you have come from does not mean I don't give you a fair hearing, and address your points.
AC "Anybody else got something sensible to say about the procession of the blades around their control orbit?" ((sp))
Yea - I have: The picture of wings flying themselves to a new plane of rotation is spot-on. And it is now the concensus here, which is an arguement I have been pressing for over (a long time) years, when it was not widely recognised. It used to be (and still is in exam-land) taught as 'gyroscopic precession' in most text books, (inc CFS, crab), because it was a covenient 'packaging' of the topic. (just like it is convenient to talk about Flapping to Equality being the soloution to DoLift - whereas it isn't really).
It isn't all that bad to use Gyroscopic Precession as a description (even though it misses the beauty of the dynamics of a helicopter), since really a Gyroscope behaves the way it does for approximatly the same reason that a Rotor Disk behaves the way it does. A gyro doesn't respond at 90deg because the Cross-Product of the Angular Momentum Vector with a Force perpendicular with the Axis of Rotation throws out a result at 90 deg. It is just the appropriate mathematical treatment of the phenomenon: A point Mass on the circumference of a gyro experiences a force in one direction for half a cycle and a force in the other direction for the other half cycle. The result can be described as Gyroscopic Precession. A Rotating Wing spends half a cycle being 'flown up' and the other half cycle being 'flown down' - the result looks just like Gyroscopic Precession for the same reason (ie half cycle exposure to up and the other half down) that Gyroscopic Precession for gyros works the way it does.
(not to mention that there is, in a non-teetering head, an element of Gyroscopic Precession-like effects, where the attitude of the Head is different to the attitude of the Disk.)
AC "Anybody else got something sensible to say about the procession of the blades around their control orbit?" ((sp))
Yea - I have: The picture of wings flying themselves to a new plane of rotation is spot-on. And it is now the concensus here, which is an arguement I have been pressing for over (a long time) years, when it was not widely recognised. It used to be (and still is in exam-land) taught as 'gyroscopic precession' in most text books, (inc CFS, crab), because it was a covenient 'packaging' of the topic. (just like it is convenient to talk about Flapping to Equality being the soloution to DoLift - whereas it isn't really).
It isn't all that bad to use Gyroscopic Precession as a description (even though it misses the beauty of the dynamics of a helicopter), since really a Gyroscope behaves the way it does for approximatly the same reason that a Rotor Disk behaves the way it does. A gyro doesn't respond at 90deg because the Cross-Product of the Angular Momentum Vector with a Force perpendicular with the Axis of Rotation throws out a result at 90 deg. It is just the appropriate mathematical treatment of the phenomenon: A point Mass on the circumference of a gyro experiences a force in one direction for half a cycle and a force in the other direction for the other half cycle. The result can be described as Gyroscopic Precession. A Rotating Wing spends half a cycle being 'flown up' and the other half cycle being 'flown down' - the result looks just like Gyroscopic Precession for the same reason (ie half cycle exposure to up and the other half down) that Gyroscopic Precession for gyros works the way it does.
(not to mention that there is, in a non-teetering head, an element of Gyroscopic Precession-like effects, where the attitude of the Head is different to the attitude of the Disk.)
A gyro doesn't respond at 90deg because the Cross-Product of the Angular Momentum Vector with a Force perpendicular with the Axis of Rotation throws out a result at 90 deg
But at least now you seem to understand that the gyro is a "simile" to help the masses grasp the idea of rotor dynamics.
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AC the Cross-Product is not the reason. It's just the maths used in those circustances. The reason is in my post. Just using the cross product without understanding why is as bad (or just as good) as using the term Gyroscopic Precession for the behaviour of a rotor disk - it just becomes a rote learnt process for predicting a result without the understanding part having to trouble the 'victim'.
(perhaps you missed the italics on my post for the word because - the quote is without them)
(perhaps you missed the italics on my post for the word because - the quote is without them)
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AND AC "at least now" is condescending rubbish, I always did !
why don't you rise above the rudeness and just use logic and rational arguement to make your point? you seem like a bright fellow, normally making sense.
why don't you rise above the rudeness and just use logic and rational arguement to make your point? you seem like a bright fellow, normally making sense.
AC - spot on with the chameleon epithet - AnFi will argue that black is white and then, when it is pointed out that black is black, will bang on about different shades of grey and how if they are neither black nor white then black and white must therefore be shades of grey, only with different values of blackness and whiteness.
He has changed the focus of this, and so many other arguments, that he claims a victory where no-one else can be bothered to debate any further.
AnFi - perhaps if you had ever been to CFS, you might understand what is and isn't in the 'notes' and it is certainly not what you believe.
that would about sum it up
He has changed the focus of this, and so many other arguments, that he claims a victory where no-one else can be bothered to debate any further.
AnFi - perhaps if you had ever been to CFS, you might understand what is and isn't in the 'notes' and it is certainly not what you believe.
I might well have no helicopter experience or knowledge)
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Yea - I have: The picture of wings flying themselves to a new plane of rotation is spot-on. And it is now the concensus here, which is an arguement I have been pressing for over (a long time) years, when it was not widely recognised. It used to be (and still is in exam-land) taught as 'gyroscopic precession' in most text books, (inc CFS, crab), because it was a covenient 'packaging' of the topic. (just like it is convenient to talk about Flapping to Equality being the soloution to DoLift - whereas it isn't really).
We have had a change of cast - previously Lu Zuckerman was played by Awblain, but now Anfi* has taken over Lu's role.
I now know relief! Long live Lu II.
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Ok, five years later and I think this thread might need resurrecting.. again! I have read through a lot of it. I'm well aware that what they teach you in flight school is never the full story - cf Bernoulli and Venturi effect when explaining lift - reasonable methods of understanding but not entirely correct as the real answer involves Navier-Stokes equations, lots of nasty vector calculus and computational solutions (as I seem to recall from fluid dynamics lectures many yonks ago). In trying to understand this, my thoughts on the matter thus far are as follows.
"Gyroscopic properties" of a rotor disc
heedm provided the best explanation of conservation of angular momentum that I've seen in a while. All of what he said accords exactly with my understanding of this concept. Conservation of angular momentum is a principle that applies to any rotating body, therefore, to my mind, it applies to a helicopter rotor system. But the question is - a) how does it apply and b) how important is this effect in understanding rotor disc dynamics? I imagine it is small but present, since (pure intuitively) I would have thought that the angular momentum of the rotor disc is on the small side compared to the lift generated by the blades. I agree that a helicopter rotor system is not a gyro, however, the system must obey conservation of angular momentum.
Lift and blade flapping
I'm sure my view on this is incomplete, so here goes. Lets consider at a zero wind hover to start with, and lets not worry to start with about cyclic inputs vs the direction you're trying to fly in.
At some point on the circle blade pitch angle is increased, increasing AOA. This increases lift on that blade, and as the pitch angle increases, the lift on that blade increases. This causes an overall increase in lift at the position of maximum blade pitch angle.
But blade flap acts to counteract that increase in lift, because as the pitch angle increases, the AOA increases, and lift increases, causing the blade to flap up, and the AOA to decrease (somewhat) due to the motion of the blade upwards. However, according to Newton's Second Law, the increase in lift will take a finite time to accelerate the blade upwards (we are now considering linear momentum and elasticity of the blade in the plane perpendicular to the plane of rotation and taking into account the centripetal/tension force on the blade which will depend on Nr amongst other things). So the relative decrease in lift (the flap) will lag the increase in lift caused by the increased AOA, causing a point of net maximum lift at some point between the max blade pitch point and the max blade flap point. I imagine the lag is greater in rigid rotor systems, where the elasticity of the blade is what allows flap.
To change direction of flight, we must tilt the disc in that direction. So, what forces cause the disc to tilt, and in what direction relative to min and max blade pitch angles? This is what I have surmised:
1. If you spun a rigid gyro in zero gravity and applied a force to it, it would demonstrate precession. If you spun a rotor system in zero gravity (but in air) it would still obey conservation of angular momentum, so it would display some precression-like effects, although it would be a 'sloppy' gyro as its spokes can move out of the axis of rotation to a certain degree. So, obviously, the more rigid the rotor system, the more gyro-like effects come into play. Any time a blade is able to exert a force on the mast, and thus tilt the whole disc, the disc will exhibit gyro like properties.
2. Blade position caused by flapping will cause the rotor disc to tilt. Increase the pitch angle of the blade and the blade will flap up, and at the point of maximum flap, the disc is tilted most up. There is a lag between max blade pitch angle and max blade flap up. I think this lag must be designed to be on the order of 90 degrees (but at least between 45 and 135) in order to induce simple harmonic motion (i.e. a sinusoidal path) of the blades round the circle. I imagine on a hinged rotor system the angle is always 90 degrees since the hinge stop (I assume the degree of hinging or tilt is limited?!) could "damp out" the top of the sinusoid curve, or else it has to be designed to be 90 degrees or greater to stop the blade from hitting the hinge stop. In a rigid rotor system I would imagine that the lag angle would vary depending on rotor speed, blade coning (i.e. how much vertical elastic tension the blade is already under due to lift requirements, i.e. variation in gross mass) and I'm sure other things I haven't thought of. Therefore I would assume the designers pick an advance angle for the swash plate somewhere in the middle of this variation and let the pilots do the rest with the cyclic.
Therefore, the total tilt of the rotor disc will be a combination of blade flap angle and a force transmitted to the mast either through the elasticity/tension of a rigid rotor system or the pressure of the blade against the hinge/tilt stop in a hinged/tilted system. The first is a mechanical 'effect' - the disc is being 'tilted' by an alteration in the position of the blades relative to the axis. Gyroscopic like effects don't apply to this type of movement because the individual blades are not acting on the whole system. Incidentally, conservation of angular momentum is conserved on each individual blade by hunting - as the blades centre of mass moves closer to the point of rotation (the mast) as it flaps up, the blade's speed will need to increase to conserve angular momentum. The second only applies if the blade is in a position to affect the movement of the whole disc, because it is constrained in some way, either by the inherent elasticity/tension of the blade or if it hits its hinge or tilt stop. This proportion of the force will act "gyroscopically". This force will generate a vector that will tend to tilt the rotor in a direction at 90 degrees to the max blade flap angle (or at 90 degrees to the max net lift position, I'm not sure which and it might depend on.. things), but in my estimation will be much smaller than the blade flap induced tilt. The resultant of the two tilting forces (I think this is called your phase lag angle?) will therefore be somewhere between the max blade flap up and 90 degrees ahead of this, but it will vary depending on your flight conditions. This might explain why I think I heard that rigid rotor systems are more likely to have an advance angle (I think this is the right terminology - the number of degrees the swashplate input leads the cyclic input direction) less than 90 degrees.
Ok go on then, pick this apart!
"Gyroscopic properties" of a rotor disc
heedm provided the best explanation of conservation of angular momentum that I've seen in a while. All of what he said accords exactly with my understanding of this concept. Conservation of angular momentum is a principle that applies to any rotating body, therefore, to my mind, it applies to a helicopter rotor system. But the question is - a) how does it apply and b) how important is this effect in understanding rotor disc dynamics? I imagine it is small but present, since (pure intuitively) I would have thought that the angular momentum of the rotor disc is on the small side compared to the lift generated by the blades. I agree that a helicopter rotor system is not a gyro, however, the system must obey conservation of angular momentum.
Lift and blade flapping
I'm sure my view on this is incomplete, so here goes. Lets consider at a zero wind hover to start with, and lets not worry to start with about cyclic inputs vs the direction you're trying to fly in.
At some point on the circle blade pitch angle is increased, increasing AOA. This increases lift on that blade, and as the pitch angle increases, the lift on that blade increases. This causes an overall increase in lift at the position of maximum blade pitch angle.
But blade flap acts to counteract that increase in lift, because as the pitch angle increases, the AOA increases, and lift increases, causing the blade to flap up, and the AOA to decrease (somewhat) due to the motion of the blade upwards. However, according to Newton's Second Law, the increase in lift will take a finite time to accelerate the blade upwards (we are now considering linear momentum and elasticity of the blade in the plane perpendicular to the plane of rotation and taking into account the centripetal/tension force on the blade which will depend on Nr amongst other things). So the relative decrease in lift (the flap) will lag the increase in lift caused by the increased AOA, causing a point of net maximum lift at some point between the max blade pitch point and the max blade flap point. I imagine the lag is greater in rigid rotor systems, where the elasticity of the blade is what allows flap.
To change direction of flight, we must tilt the disc in that direction. So, what forces cause the disc to tilt, and in what direction relative to min and max blade pitch angles? This is what I have surmised:
1. If you spun a rigid gyro in zero gravity and applied a force to it, it would demonstrate precession. If you spun a rotor system in zero gravity (but in air) it would still obey conservation of angular momentum, so it would display some precression-like effects, although it would be a 'sloppy' gyro as its spokes can move out of the axis of rotation to a certain degree. So, obviously, the more rigid the rotor system, the more gyro-like effects come into play. Any time a blade is able to exert a force on the mast, and thus tilt the whole disc, the disc will exhibit gyro like properties.
2. Blade position caused by flapping will cause the rotor disc to tilt. Increase the pitch angle of the blade and the blade will flap up, and at the point of maximum flap, the disc is tilted most up. There is a lag between max blade pitch angle and max blade flap up. I think this lag must be designed to be on the order of 90 degrees (but at least between 45 and 135) in order to induce simple harmonic motion (i.e. a sinusoidal path) of the blades round the circle. I imagine on a hinged rotor system the angle is always 90 degrees since the hinge stop (I assume the degree of hinging or tilt is limited?!) could "damp out" the top of the sinusoid curve, or else it has to be designed to be 90 degrees or greater to stop the blade from hitting the hinge stop. In a rigid rotor system I would imagine that the lag angle would vary depending on rotor speed, blade coning (i.e. how much vertical elastic tension the blade is already under due to lift requirements, i.e. variation in gross mass) and I'm sure other things I haven't thought of. Therefore I would assume the designers pick an advance angle for the swash plate somewhere in the middle of this variation and let the pilots do the rest with the cyclic.
Therefore, the total tilt of the rotor disc will be a combination of blade flap angle and a force transmitted to the mast either through the elasticity/tension of a rigid rotor system or the pressure of the blade against the hinge/tilt stop in a hinged/tilted system. The first is a mechanical 'effect' - the disc is being 'tilted' by an alteration in the position of the blades relative to the axis. Gyroscopic like effects don't apply to this type of movement because the individual blades are not acting on the whole system. Incidentally, conservation of angular momentum is conserved on each individual blade by hunting - as the blades centre of mass moves closer to the point of rotation (the mast) as it flaps up, the blade's speed will need to increase to conserve angular momentum. The second only applies if the blade is in a position to affect the movement of the whole disc, because it is constrained in some way, either by the inherent elasticity/tension of the blade or if it hits its hinge or tilt stop. This proportion of the force will act "gyroscopically". This force will generate a vector that will tend to tilt the rotor in a direction at 90 degrees to the max blade flap angle (or at 90 degrees to the max net lift position, I'm not sure which and it might depend on.. things), but in my estimation will be much smaller than the blade flap induced tilt. The resultant of the two tilting forces (I think this is called your phase lag angle?) will therefore be somewhere between the max blade flap up and 90 degrees ahead of this, but it will vary depending on your flight conditions. This might explain why I think I heard that rigid rotor systems are more likely to have an advance angle (I think this is the right terminology - the number of degrees the swashplate input leads the cyclic input direction) less than 90 degrees.
Ok go on then, pick this apart!
And awaaaaayyyy we go again....
Some contradictions in the opening statement. A zero-wind hover is (let's assume) neutral cyclic - so you won't be flying in any direction anyway. Then you want the pitch angle increased - without a cyclic or collective movement??
The usual scenario is a puff of wind, coming from ahead, affects the relative airflow. Not a pitch change.
The maximum lift point, under the puff of wind scenario, (not an increase in pitch scenario) is at 90 degrees right, and the maximum flap point is straight ahead, but the extra lifting force from the puff has been decreasing as the blade rotates, to be zero effect straight ahead. But if you insist on using an increase in pitch scenario, it has to come from a cyclic movement of the swash plate, which has been feeding that extra pitch in from the tail boom right around to the 90 right, reaching the maximum pitch at 90 right, and then decreasing to zero over the nose.
BUT!! to make that happen, i.e. max pitch at 90 right, the cyclic has been pulled BACK. Not forward.
The difference between max pitch and max flap position is not always 90 degrees. In the R22 it is 72 degrees. Just the way it is. Google up Lu Zuckerman and his "missing 18 degrees". Apply a force to the blade, and as you correctly say, Mr Newton allows it to start accelerating up. To move forwards, the max pitch and max upward acceleration is at 90 LEFT, on the retreating side. The force keeps lifting the blade, but it is turning as it goes, so by the time the force is expended, the blade has turned about 90 degrees, depending on the design. The back of the disc is high, the front is low, the total rotor thrust is pointing forward, and the aircraft will respond to that force by starting to move forward.
The blade should never hit its stops - the vibration will cause damage. On a B206, the blade stops are of a softer metal than the mast, so the stops will deform before the mast is damaged, or so the theory goes. The lift variations from swash plate inputs will stop the blade from flapping so far that it hits the stops and the mast.
See above. In a teetering system, the disc just pulls on the rotor head through a single point, and the pendulous fuselage just dumbly follows along. This is a "zero-offset" situation - the rotor disc has no Moment to make the mast and fuselage follow the tilt of the disc.
In an articulated system, the movable blades apply the force to the fixed rotor head, and because the blades are hinged at a small distance away from the mast, a moment is generated to make the mast and fuselage follow along, making the articulated aircraft more responsive to control inputs.
In a rigid system (Bolkow/MBB/ Euroflopter) there is a virtual hinge point in the flexible blade, and it is even further out, giving a bigger moment and responsiveness. Note the Mast Moment Indicator on such aircraft to limit how much force the dopey pilot feeds in.
Many previous posts have emphasised that there are way too many variables in a rotor system for it to ever qualify as a gyroscope, but to make it easier for people to understand phase lag, it is simply stated:
"A rotor disc is LIKE a gyroscope."
Lets consider at a zero wind hover to start with, and lets not worry to start with about cyclic inputs vs the direction you're trying to fly in.
At some point on the circle blade pitch angle is increased, increasing AOA.
At some point on the circle blade pitch angle is increased, increasing AOA.
The usual scenario is a puff of wind, coming from ahead, affects the relative airflow. Not a pitch change.
net maximum lift at some point between the max blade pitch point and the max blade flap point
BUT!! to make that happen, i.e. max pitch at 90 right, the cyclic has been pulled BACK. Not forward.
The difference between max pitch and max flap position is not always 90 degrees. In the R22 it is 72 degrees. Just the way it is. Google up Lu Zuckerman and his "missing 18 degrees". Apply a force to the blade, and as you correctly say, Mr Newton allows it to start accelerating up. To move forwards, the max pitch and max upward acceleration is at 90 LEFT, on the retreating side. The force keeps lifting the blade, but it is turning as it goes, so by the time the force is expended, the blade has turned about 90 degrees, depending on the design. The back of the disc is high, the front is low, the total rotor thrust is pointing forward, and the aircraft will respond to that force by starting to move forward.
I imagine on a hinged rotor system the angle is always 90 degrees since the hinge stop (I assume the degree of hinging or tilt is limited?!) could "damp out" the top of the sinusoid curve, or else it has to be designed to be 90 degrees or greater to stop the blade from hitting the hinge stop.
the pressure of the blade against the hinge/tilt stop in a hinged/tilted system.
In an articulated system, the movable blades apply the force to the fixed rotor head, and because the blades are hinged at a small distance away from the mast, a moment is generated to make the mast and fuselage follow along, making the articulated aircraft more responsive to control inputs.
In a rigid system (Bolkow/MBB/ Euroflopter) there is a virtual hinge point in the flexible blade, and it is even further out, giving a bigger moment and responsiveness. Note the Mast Moment Indicator on such aircraft to limit how much force the dopey pilot feeds in.
Many previous posts have emphasised that there are way too many variables in a rotor system for it to ever qualify as a gyroscope, but to make it easier for people to understand phase lag, it is simply stated:
"A rotor disc is LIKE a gyroscope."
Consider the origin of this myth. The US Army bought a bunch of UH-1 helicopters. Bell wrote an aerodynamic text which described their 2-bladed rotor system as being subject to gyroscopic precision. The Army needed an aerodynamic text, so it copied the Bell text. The FAA, needed a helicopter handbook, so, it copied the US Army text. And so on... Problem was, the Army substituted "helicopter" in-place of "UH-1." The industry progressed beyond the Bell-Hiller rotor system, but the texts never have.
P.s. I realised I used the same explanatory mistake after watching
The small side
Whatever it is, the angular momentum of a running helicopter rotor system is not small. If it was small, engine-off landings wouldn't work out as well as they do.
P.s. I realised I used the same explanatory mistake after watching this.
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(purely intuitively) I would have thought that with the angular momentum on the "small side" that you could easily enough reach up and stop the rotor with your hand? Especially perhaps in the case where the lift was zero - the helicopter on the ground with the rotors running.
Whatever it is, the angular momentum of a running helicopter rotor system is not small. If it was small, engine-off landings wouldn't work out as well as they do.
Whatever it is, the angular momentum of a running helicopter rotor system is not small. If it was small, engine-off landings wouldn't work out as well as they do.
Even so, small, relative to the lift required to hover an x tonne helicopter does not necessarily imply small enough to stop with your hand :P