Gyroscopic precession engineering question

[maxtork]

Ok I have a few questions for the engineer types. Here is what I think I know...the questions comes after:

1-Gyroscopic precession causes the rotor system to react 90 degrees out of phase from the control input (generally speaking, see below). On a 2 bladed teetering system this seems to be the case anyways.
2- The amount of flapping hinge offset can change that 90 degrees to something smaller. The more offset the less phase lag?
3- Pitch link phase angle offset is also a factor. If the pitch link is 45 degrees in front of the blade then that would be 45 degrees removed from the 90 gyroscopic precession. If 45 degrees behind the blade then it would be added to the 90 degrees.

Now here are the questions-
1- Is that everything that would effect the input phase angle? What else am I missing?
2- Is this something that is engineered on paper before they ever make parts? Or does one need to design build and run a rotor system on a whirl tower to see just what the actual phase angle displacement is and then design the flight control system to tilt the swashplate in the right direction? I would guess it is the former not the later but seems like it might be a tough thing to get right on the first shot and difficult to adjust for if you miss the mark.

Thanks
Max

[ShyTorque]

Point 1 is incorrect. A gyroscope is a solid, rotating mass, fixed solidly to the axle. A helicopter rotor system has hinges, albeit in a few different ways. The blades are caused to fly independently to a new position in relation to the rotor axis using aerodynamic forces, rather than gyroscopic precession.

[Jhieminga]

I beg to differ. Any rotating mass is a gyroscope with its accompanying effects. A spinning (fixed wing) airframe can also show the effects of gyroscopic precession. You don't need a fixed axle to identify as a gyroscope, just mass and a rotational speed.

[LRP]

I beg to differ. Any rotating mass is a gyroscope with its accompanying effects. A spinning (fixed wing) airframe can also show the effects of gyroscopic precession. You don't need a fixed axle to identify as a gyroscope, just mass and a rotational speed.
3,2,1, fights on!

[HeliComparator]

I beg to differ. Any rotating mass is a gyroscope with its accompanying effects. A spinning (fixed wing) airframe can also show the effects of gyroscopic precession. You don't need a fixed axle to identify as a gyroscope, just mass and a rotational speed.
Yes but that is not a rotor disc. The spinning fixed wing exhibits precession because external forces are chaning the axis about which the spinning mass is spinning.
With a rotor disc, the disc is not forced to do anything. It flies where it wants to go. The confusion arises from the 90 degree thing because the pitch rods are at a maximum (or minimum) pitch at roughly 90 degrees to the highest point of the blades. But that is because at that (90 degrees "offset") point, the vertical speed of the blades is at a maximum. As the blade approaches its maximum height the pitch reduces until it is flat at the highest point - otherwise the blade would continue to fly up! Ditto when the blade is at its lowest point. So the 90 degrees arises from the difference between blade vertical speed, and blade height. It is nothing to do with gyro precession.

[DuncanDoenitz]

No, "The blades are not not caused to fly independently to a new position in relation to the rotor axis using aerodynamic forces, rather than gyroscopic precession". If that were true, a fixed wing with a positive alpha would always fly up.

A wing, and the airframe to which it may be fixed, will fly in a direction determined by the 4 forces of lift, drag, gravity and thrust.

A rotating wing will do exactly the same, but adds centrifugal and gyroscopic forces into the mix.

[HeliComparator]

No, "The blades are not not caused to fly independently to a new position in relation to the rotor axis using aerodynamic forces, rather than gyroscopic precession". If that were true, a fixed wing with a positive alpha would always fly up.

A wing, and the airframe to which it may be fixed, will fly in a direction determined by the 4 forces of lift, drag, gravity and thrust.

A rotating wing will do exactly the same, but adds centrifugal and gyroscopic forces into the mix.

Well there is of course no such thing as centrifugal force. Nor is there gyroscopic force where the thing is not being forced to do something it doesn’t naturally want to do.

[HeliComparator]

Anyway lots of people believe the earth is flat. Even more believe in an imaginary friend. So there is no point in trying to convince those who have firm beliefs to change their minds.

[Rotorbee]

Not again. Could everybody please read their Prouty before coming up with that again and again and again? It has been debunked several times here. The Robinsons have an offset of 72°. Not 90°. Can't be gyroscopic precession. Other helicopters have other offsets. Yes, Smarter Every Day got it oh so wrong, too. He isn't that smart. Otherwise he would have talked to somebody who actually knows something about it. And yes, the FAA helicopter handbook gets it wrong, too. It's lies to children. Simplifying things to the point where it is wrong.
In a vacuum you would have that effect, but aerodynamic effects are way stronger and therefore gyroscopic precession is not important on a rotor. It is called phase lag.
And there is no centrifugal force either. Centripetal force is the real thing. Goes in the opposite direction.

[RVDT]

Ok I have a few questions for the engineer types. Here is what I think I know...the questions comes after:

1-Gyroscopic precession causes the rotor system to react 90 degrees out of phase from the control input (generally speaking, see below). On a 2 bladed teetering system this seems to be the case anyways.
2- The amount of flapping hinge offset can change that 90 degrees to something smaller. The more offset the less phase lag?
3- Pitch link phase angle offset is also a factor. If the pitch link is 45 degrees in front of the blade then that would be 45 degrees removed from the 90 gyroscopic precession. If 45 degrees behind the blade then it would be added to the 90 degrees.

Now here are the questions-
1- Is that everything that would effect the input phase angle? What else am I missing?
2- Is this something that is engineered on paper before they ever make parts? Or does one need to design build and run a rotor system on a whirl tower to see just what the actual phase angle displacement is and then design the flight control system to tilt the swashplate in the right direction? I would guess it is the former not the later but seems like it might be a tough thing to get right on the first shot and difficult to adjust for if you miss the mark.

Thanks
Max

I was lucky enough to meet this guy a few times before he passed. Maybe not definitive as he always said but good info.

RW Prouty (https://www.actechbooks.com/0624-EES-E.html) was a staff engineer-flying qualities at Hughes Helicopters Inc, in Culver City, Calif. He jokingly refers to himself as a "journeyman engineer who has journeyed, over the past 28 years, from Hughes Helicopters to Sikorsky Aircraft to Bell Helicopter to Lockheed's helicopter program and finally back to Hughes" He further observed that "helicopter people tend to go around in circles." As an aerodynamicist, his experiences included preliminary design. performance and flying-qualities analysis, wind-tunnel testing, and flight testing.

[ShyTorque]

Anyway lots of people believe the earth is flat. Even more believe in an imaginary friend. So there is no point in trying to convince those who have firm beliefs to change their minds.


As a professional helicopter pilot and military trained instructor since 1979 I probably am rather fixed in my beliefs.

Try replacing the rotor blades with lengths of non aerodynamic, 4 x 2 planking and then see if you can make them precess using the same control system.

[maxtork]

Wow....and I thought I was asking an easy question LOL. Good information all around ( from an outsider looking in...not taking sides). By all means keep going. I'll be right back....just gotta go get some popcorn!

[Ascend Charlie]

The books use "precession" as a way of getting stupid students to sort-of understand why the disc behaves the way it does.

The swash plate and links feed in a pitch angle to the blade. Blade's angle of attack goes up, and generates more lift.
Lift is a force. F=mA
The lifting force starts to accelerate the blade upwards, with a rate depending on the mass of the blade. It takes time from when the max input is fed in, with the max rate of acceleration, until the blade reaches its max position.
While this is happening, the blade is rotating about the mast. By the time the blade reaches its max height, the mast has turned ABOUT 90 degrees. (As stated before the R-22 has turned only 72 degrees, mainly because of the light blade.)
In the meantime, the swash plate has been reducing the pitch angle, so the blade is now being told to flap down, and so it goes on around the full circle. The max acceleration up or down happens ABOUT 90 degrees ahead of where the blade reaches its highest or lowest point.

Some helicopters have the lead angle set 45 degrees ahead, but also have the control rods moved 45 degrees around the mast. Others have the control rods running up the side of the mast, so the about-90 degree lead input is easily done.

And don't get into a tizz about "Flapping to Equality" because it only happens if the cyclic is held fixed, and it results in an eventual crash. People think that in forward flight, the advancing blade must flap up to reduce the extra lift from the forward airflow, and the retreating blade flaps down. All you need to do is look at the disc in forward flight, the advancing blade is flapping down, and retreating blade is going up.
As soon as the cyclic is moved to prevent the flap-back, the blades obey the swash plate. Poke it forward, disc goes forward. Simples...

[Robbiee]

Not again. Could everybody please read their Prouty before coming up with that again and again and again? It has been debunked several times here. The Robinsons have an offset of 72°. Not 90°. Can't be gyroscopic precession. Other helicopters have other offsets. Yes, Smarter Every Day got it oh so wrong, too. He isn't that smart. Otherwise he would have talked to somebody who actually knows something about it. And yes, the FAA helicopter handbook gets it wrong, too. It's lies to children. Simplifying things to the point where it is wrong.
In a vacuum you would have that effect, but aerodynamic effects are way stronger and therefore gyroscopic precession is not important on a rotor. It is called phase lag.
And there is no centrifugal force either. Centripetal force is the real thing. Goes in the opposite direction.

I don't recall the Rotorcraft Flying Hanbook ever saying that a helicopter's rotor "is" a gyro. I do recall it saying that its "like a gyro", which is not the same thing, but its been a long time since I've looked so,...

Anyway, the FAA only wants us pilots to have a surface level knowledge when it comes to aerodynamics. I know what they want me to know, and it helps me get through my BFRs,...but I'm not going to teach a class of engineering students, or design my own helicopter with it, lol.

Anyway, I thought the R22 was offset around 60°,...?

[212man]

Gyroscopic precession in a rotor - the gift that keeps on giving. Can we bring Lu Zuckerman back from the dead? Yes, centrifugal force is also not real - it’s a pseudo force.

[maxtork]

So....now that I have had a chance to absorb all this, it appears I don't know what I thought I knew. Now that I think I know what I should have known...I will adjust my question accordingly.

If the phase angle displacement is due to aerodynamic forces and the time it takes each blade to react to the inputs as they are provided, then how does one account for this from a design perspective? Is it a matter of calculating the increase in lift due to a control input and how long that force would take to move the blade to its new position? I'm sure there is a way but just seems like there would be a ton of factors at work and hard to engineer correctly right out of the gate.

Thanks for all the input so far. BTW I did read Prouty's book long ago but can't find my copy to reference for this question.

Thanks
Max

[SplineDrive]

On a teeter rotor with no pitch flap coupling and no hub spring rate, the first flap frequency is at 1/rev, i.e resonance with the rotor rpm. A system in this state has a phase lag of 90 degrees. When a hub spring is added (or an offset flap hinge) the first flap frequency is raised and the phase lag becomes less than 90 degrees. A very stiff out of plane rotor can have this phase lag of 35-40 degrees. This isn't the only factor that influences the geometric arrangement of control inputs vs blade position, though. Pitch flap coupling can be intentionally introduced to either damp out flap responses to pitch inputs or, in some cases, act as a "negative spring" and accentuate flap response to pitch inputs. This is relatively uncommon on main rotors, but can serve to drop the first flap mode below 1/rev.

Generally speaking, a rotor design team does not have to guess at the phase lag as calculating the first flap frequency is pretty straightforward these days. That said, there are more complex rotor stability issues, particularly with articulated rotors in some maneuvers, that can be addressed by shifting control inputs, leaning pitch links, etc. Those adjustments are often made during flight test, even by experienced OEMs.

Also, centrifugal force is "imaginary" to physics textbooks (and perhaps people online) but when working and analyzing in a rotating frame, it is the common and even preferred notation, even down to part names.

[RVDT]

BTW I did read Prouty's book long ago but can't find my copy to reference for this question.

Thanks
Max

Digital versions in the link behind his name in post #10.

[Rotorbee]

Hey Robbie, well yes, it says "like a gyro", but with all the explanation following that statement, it is still wrong.
Directly from the Rotorcraft Flying Handbook:
Gyroscopic Precession
The spinning main rotor of a helicopter acts like a gyroscope.
As such, it has the properties of gyroscopic action, one of
which is precession. Gyroscopic precession is the resultant
action or deflection of a spinning object when a force is
applied to this object. This action occurs approximately 90°
in the direction of rotation from the point where the force
is applied (or 90° later in the rotation cycle). (And so on ...)


I am pretty sure it is 72°.

[finalchecksplease]

All explained fairly well here:https://en.wikipedia.org/wiki/Reactive_centrifugal_force

[Jhieminga]

1-Black magic causes the rotor system to react 90 degrees out of phase from the control input (generally speaking, see below). On a 2 bladed teetering system this seems to be the case anyways.

Fixed that for you.... ;)
The books use "precession" as a way of getting stupid students to sort-of understand why the disc behaves the way it does.
I think we have the basics of the issue summarised here, with apologies to the students. There is a lot at work in and around a rotor disc with mechanics and aerodynamics fighting each other on one end and cooperating on the other. In itself, the principle that we call gyroscopic precession is a simplification of the dynamics of a rotating system of masses, but we needed to boil it down to something comprehensible. I still think that it is safe to say that the properties of gyroscopes have a place within the various influences on a rotor system, but what that place is and how it interacts with the rest is something I will happily leave to others to explain.

A lot of our understanding of things like this are based on simplifications, but we then tend to run into the limitations of those simplifications when something doesn't fit into this mould anymore. That doesn't mean that the principle is wrong. We can get into a lovely discussion on how Bernoulli does not fully explain how a wing produces lift and drag. It does not mean that Bernoulli got it wrong. It means that we've got an opportunity to learn.

[ShyTorque]

Gyroscopic precession in a rotor - the gift that keeps on giving. Can we bring Lu Zuckerman back from the dead? Yes, centrifugal force is also not real - it’s a pseudo force.

Exactly. It’s really all about inertia and “forcing” an object to turn rather than go straight on, as it would naturally do it left to its own devices.

[Ascend Charlie]

Also note that if the rotor system was truly a gyroscope, it would have to follow the first property of a gyroscope - RIGIDITY IN SPACE, i.e. it would be very difficult to disturb it from its axis.

A puff of wind will knock it off, causing flapping and diversion.

Ergo, it is not a gyroscope. But sometimes it behaves LIKE a gyroscope.

[Robbiee]

Hey Robbie, well yes, it says "like a gyro", but with all the explanation following that statement, it is still wrong.
Directly from the Rotorcraft Flying Handbook:
Gyroscopic Precession
The spinning main rotor of a helicopter acts like a gyroscope.
As such, it has the properties of gyroscopic action, one of
which is precession. Gyroscopic precession is the resultant
action or deflection of a spinning object when a force is
applied to this object. This action occurs approximately 90°
in the direction of rotation from the point where the force
is applied (or 90° later in the rotation cycle). (And so on ...)


I am pretty sure it is 72°.

I honestly don't care if its wrong. I'm neither an engineer, nor a physicist, but just a pilot. If they wanted me to tell them on my checkride that 2+2=5 in order to get my license, I would have. I'm not designing helicopters. I just want to fly them,...and knowing why the pitch horns are offset (or even that they are offset) isn't going to affect my ability to do that. :hmm:

[Rotorbee]

Oh, Robbie, my excuses, it wasn't my intention to patronise you, not at all. We have met on this forum quite often and I sometimes get the impression, that you try to be at bit too modest. You have crossed swords with quite a few of our most experienced egos lurking here and I must say, your opinion is much appreciated. You do bring sometimes another perspective and that is needed in a discussion. Discussions are made for changing opinions. If we don't think about what others say and even sometimes get things wrong, we don't learn. Exchanging opinions and not thinking about them, is utterly useless.
Common, admit it, you are interested in all things helicopter related. Even if you think it does not make you a better pilot, I think it does. Every little piece of knowledge changes how you look at it. Even if it is a stupid bolt on an airframe that isn't secured properly. It makes you think and you like that. Otherwise you would not hang out here.

[Wide Mouth Frog]

Robbiee, you'll like this one.

A while back when this subject was running a physicist got involved, and challenged even the most experienced members on here to justify their reasoning why a rotor is not a gyroscope, or even like a gyroscope. After endless debate, some crusty old naval pilot chipped in with: Sitting in my helicopter on a wild day with rotors running, my AI showed every heave and toss of the ship. My rotor stayed locked in its plane parallel to the deck. The AI is a gyro, the rotor is not. That was the last post on that thread if I remember. A man after your own heart I guess !

[maxtork]

Thanks for all the replies folks. Great info here and lots of new concepts to research. Much appreciated.

Max

[SplineDrive]

Thanks for all the replies folks. Great info here and lots of new concepts to research. Much appreciated.

Max

There’s not new concepts in this thread… this is basic stuff out of a rotor dynamics textbook.

[212man]

There’s not new concepts in this thread… this is basic stuff out of a rotor dynamics textbook.
When you have been here (on Pprune) long enough, it seems like 'groundhog day'! Waiting in the queue, we have HV curves, PC1/PC2/Cat A, and many more topics to bring up

[Robbiee]

Robbiee, you'll like this one.

A while back when this subject was running a physicist got involved, and challenged even the most experienced members on here to justify their reasoning why a rotor is not a gyroscope, or even like a gyroscope. After endless debate, some crusty old naval pilot chipped in with: That was the last post on that thread if I remember. A man after your own heart I guess !

Well, my ass is not a flame thrower, but if I hold a lighter back there and blow a fart, its certainly "like" one. :}

[maxtork]

There’s not new concepts in this thread… this is basic stuff out of a rotor dynamics textbook.
Well they are new concepts for me to look into. If we all knew everything already there wouldn't be anything to talk about !

[Ascend Charlie]

this is basic stuff out of a rotor dynamics textbook.

​​​​​​​It's when the textbook gets it wrong that these topics recur. The FAA handbook is still full of wrong statements and misleading "vector" diagrams.

[Wide Mouth Frog]

Robbiee, by that I meant that here's a practical person, speaking to his own experience to which there is no answer. Take a compliment when it's offered !

[Robbiee]

Robbiee, by that I meant that here's a practical person, speaking to his own experience to which there is no answer. Take a compliment when it's offered !

As amusing as your story is, it points out the major problem that sparks these debates in the first place. The highly complex and often misunderstood concept of a simile.

Anyway, I'm just a bored troll stirring the pot from time to time for his own amusement. I feed on conflict, not compliments. :}

[[email protected]]

So glad I missed this rehash of an old topic - is there a way of getting PPrune to react to the combination of words 'rotor' plus 'gyroscope' so it automatically leads the poster to all the previous discussions we have had on this topic?

I know there is a search function but nowadays people just like to ask the question and wait.

[[email protected]]

Sitting in my helicopter on a wild day with rotors running, my AI showed every heave and toss of the ship. My rotor stayed locked in its plane parallel to the deck. The AI is a gyro, the rotor is not. Pretty perfect illustration:ok:​​​​​​​

[Ascend Charlie]

Remember that the stick would have been held central, with the swash plate level with the deck, so the rotor couldn't have done much different.

[[email protected]]

Remember that the stick would have been held central, with the swash plate level with the deck, so the rotor couldn't have done much different.
But if the rotor was a gyro it would have maintained position in space - it could have flapped around the hinges quite markedly regardless of the swashplate position. But it didn't because it's not a gyro - as I know you know:ok:

[Robbiee]

But if the rotor was a gyro it would have maintained position in space - it could have flapped around the hinges quite markedly regardless of the swashplate position. But it didn't because it's not a gyro - as I know you know:ok:

,...but if it were "like a gyro" then it would have something in common with a gyro.

If the pitch horns weren't offset, then when you push the cyclic forward, you wouldn't go forward, you'd go left (i.e. in the direction of the rotor's rotation),...maybe not a full 90° left, but some degree anyway. What other device does something like that? Oh yeah,...a gyro!

:cool:

[Wide Mouth Frog]

I thought very carefully about whether to add to this post, but on balance I think there's an important point to be made.

What I think good teachers are trying to do is to give you enough information to do the job, and although it may not be the whole truth, they make sure that nothing they offer is wrong. That way anyone coming in later isn't trying to correct mistakes, they're trying to extend and enrich what you know already. If you teach that rotors are 'like' gyros, you're picking on a single common feature that can't support any extension, and is easily proved to be wrong from the example of the helicopter on the ship.

Robbiee, you've already said that your interest is purely flying, and that these aerodynamic curiosities are just hurdles you have to cross to get to do that. I'd say that's completely fine and I wish you luck and success in your flying career. If you ever have to teach though, I think there's a responsibility to dig a little deeper, and acknowledge the simplifications you might choose to make, and to make those simplifications act as foundations not detours.

[Robbiee]

I thought very carefully about whether to add to this post, but on balance I think there's an important point to be made.

What I think good teachers are trying to do is to give you enough information to do the job, and although it may not be the whole truth, they make sure that nothing they offer is wrong. That way anyone coming in later isn't trying to correct mistakes, they're trying to extend and enrich what you know already. If you teach that rotors are 'like' gyros, you're picking on a single common feature that can't support any extension, and is easily proved to be wrong from the example of the helicopter on the ship.

Robbiee, you've already said that your interest is purely flying, and that these aerodynamic curiosities are just hurdles you have to cross to get to do that. I'd say that's completely fine and I wish you luck and success in your flying career. If you ever have to teach though, I think there's a responsibility to dig a little deeper, and acknowledge the simplifications you might choose to make, and to make those simplifications act as foundations not detours.

So, are you saying that just because a spinning rotor doesn't act like a gyro on a pitching ship, that the pitch horns aren't offset because (like a gyro) input is experienced later in the direction of rotation?

Like it or not, its an apt simile that does absolutely nothing (just like whatever the "real" reason is) for a pilot than to help him pass a few tests.

If I were a teacher, I'd teach my students what they need to know to pass the tests. Flight training is unbelievably expensive, and there's no need to make it more expensive by wasting the students time (money) on "Cliff Clavinesque" information!

If pilots want to know more than what the FAA wants them to know, well,...that's what the library (Google) is for,...plus its free!

[megan]

My rotor stayed locked in its plane parallel to the deckIt won't though if SAS is still engaged, all because of a gyro elsewhere in the system. ;)

[Ascend Charlie]

A helicopter is LIKE a hummingbird, it can hover
A helicopter is LIKE an aeroplane, it can fly forwards
A helicopter is LIKE a person on rollerskates on an ice rink, it is somewhat unstable
A helicopter is LIKE an egg with a straw stuck up its fundamental orifice
A helicopter is LIKE a lot of things, but it ain't a gyroscope. Some aspects are LIKE a gyro.

It gives the lowest common denominator (a student) a concept to work with. In the same manner, "Ground Effect is LIKE a cushion of air". The increase of RRPM as the blades cone upward is LIKE a skater spinning round and pulling their arms in. Teaching some students is LIKE practising bleeding.

[[email protected]]

It won't though if SAS is still engaged, all because of a gyro elsewhere in the system. ;)
That's why you don't sit on the deck with the ASE/SAS engaged until you are ready to lift.:ok:

[[email protected]]

If I were a teacher, I'd teach my students what they need to know to pass the tests. Flight training is unbelievably expensive, and there's no need to make it more expensive by wasting the students time (money) on "Cliff Clavinesque" information! depends where you set your personal standards - knowing the wrong thing is worse than knowing nothing at all.

[Robbiee]

A helicopter is LIKE a hummingbird, it can hover
A helicopter is LIKE an aeroplane, it can fly forwards
A helicopter is LIKE a person on rollerskates on an ice rink, it is somewhat unstable
A helicopter is LIKE an egg with a straw stuck up its fundamental orifice
A helicopter is LIKE a lot of things, but it ain't a gyroscope. Some aspects are LIKE a gyro.

It gives the lowest common denominator (a student) a concept to work with. In the same manner, "Ground Effect is LIKE a cushion of air". The increase of RRPM as the blades cone upward is LIKE a skater spinning round and pulling their arms in. Teaching some students is LIKE practising bleeding.

Arguing on Pprune is like trying to put a square peg into a round hole while jumper cables are attached to your plumbs. :ugh: :eek:

depends where you set your personal standards - knowing the wrong thing is worse than knowing nothing at all.

Well, a lot of people on the internet wrongly believe that "Settling with Power" is when you're coming in hot and just wait too long to put on the brakes, or that its "overpitching", so,...

Whatta ya gonna do? :cool:

[RVDT]

Is The Rotor A Gyro? - Ray W. Prouty 1926 - 2014

You might remember your first experience with a toy gyroscope and the amazing things it did in apparent disregard for the obvious laws of nature.

It displayed remarkable stability. If it was set spinning horizontally, it wanted to stay horizontal no matter how you moved the support, but if you were determined to move the axis by brute force, the gyro moved in a strange way—at right angles to the applied moment. Even if you were later exposed to the gyroscopic equations and acquired a confidence in your ability to manipulate them, you were probably still vaguely disturbed by this device's strange behavior (I know I was).

A rotor in a vacuum.

The disc of a spinning helicopter rotor certainly looks much like a toy gyroscope. So does it act like one? Yes and no. The reason for the "no" is the existence of very large aerodynamic forces on the rotor blades. As a matter of fact, if you remove the aerodynamics by running a rotor in a vacuum, it will demonstrate gyroscopic stability.

A rotor with blades hinged at the center of rotation (such as a teetering rotor) for example, in a vacuum, there are no aerodynamic forces, only centrifugal forces acting in the plane of rotation, and these can produce no moments about the flapping hinges. If the shaft is tilted, no changes in moments will be produced and the rotor disc will remain in its original position as if it were a gyroscope. (Of course, if the rotor had had offset flapping hinges, the centrifugal forces would have produced moments that would have aligned the blades perpendicular to the shaft.

A rotor in air.

In air, the aerodynamic forces will cause any rotor to align itself perpendicular to the shaft.

First, there is the tilt of the shaft alone as the rotor disc acts as a gyroscope and remains in its original plane. However, since the blade feathering is referenced to the shaft, the angle of attack of the right-hand blade is increased and that of the left-hand blade decreased by the same amount.

This causes the rotor to flap until it is perpendicular to the shaft, where it will again be in equilibrium with a constant angle of attack around the azimuth and the moments will be balanced. This alignment is very rapid, usually taking less than one revolution following a sudden tilt. Because of this, the flapping motion in hover has practically no effect on the stability of the helicopter in terms of holding a given attitude.

This was not recognized by many people in the early days of helicopters.

A rotor as a gyro.

So, if a rotor does not act like a gyro trying to retain its position in space, when does it act like a gyro? This answer has to do with how the rotor moves if you put an unbalanced aerodynamic lift on the disc. It will respond by moving at right angles to the unbalance just as the toy gyro does, and it does so in exact compliance with the gyroscopic laws that say the angular rate of motion-the "precession rate" —will be proportional to the applied moment.

This is in apparent contrast to Newton's Law that states that an angular acceleration should be the result of an applied moment. (The rotor/gyro is actually obeying Newton's Law but its high rate of rotation is producing this overwhelming side effect.)

The unbalanced lift distribution can come either from external sources such as a gust or from control inputs using cyclic pitch. For example, right stick will lower the angle of attack of the blade over the tail and raise it on the blade over the nose. This noseup unbalance on the disc will cause it to precess down to the right and the rest of the helicopter will soon follow. For a given helicopter, the resulting right roll rate will be directly proportional to the change of cyclic pitch from trim. Not all helicopters, however, will roll at the same rate for the same cyclic pitch. In response to the gyroscopic laws, the rate will be higher for those helicopters whose rotors are lighter or turning faster.

Thus, it may be seen that the rotor is like the mysterious toy gyro as it responds to applied moments but it has practically none of the toy's inherent stability. If required, this last drawback can be compensated. Early Bell helicopters used a stabilizer bar that acted like a gyro and controlled cyclic pitch in a way that transferred some of the gyro stability to the rotor. The Lockheed rotor and gyro system did the same thing. Nowadays, the designer can use a hidden black box containing a small, rapidly turning gyro with appropriate connections to the control system to make the helicopter achieve as much stability as desired.

[[email protected]]

Whatta ya gonna do? https://www.pprune.org/images/smilies/cool.gif let you continue in your little bubble of self-righteous indignation.

​​​​​​​ If you want to revel in ignorance that's your business.

[Robbiee]

let you continue in your little bubble of self-righteous indignation.

If you want to revel in ignorance that's your business.

Wow! I haven't been accused of righteous indignation since my high school English class back in '88. Damn, that takes me back.

Anyway, given the above post, seems this Prouty guy shares my ignorance. So at least now I have someone to tango with. :ok:

[Lala Steady]

Let's play 'Spot the Troll' - oh yes its robbiieee

[Robbiee]

Let's play 'Spot the Troll' - oh yes its robbiieee

Hmm,...if I'm not mistaken, this is how Millennial's say, "I don't agree with you",..right?

[[email protected]]

The British Army have a very quaint expression for those that can't or won't listen to reason - 'You can't educate pork' - somehow seems appropriate here

[Robbiee]

The British Army have a very quaint expression for those that can't or won't listen to reason - 'You can't educate pork' - somehow seems appropriate here

We have an expression in The States when someone has there knickers in a twist about something. There's no emoji here for it, so I'll just go with the closest one. :rolleyes:

[helispotter]

I have enjoyed reading the commentary (debate) on this topic, even if some of you have seen it discussed to death.

The video of the Bo105 main rotor blade filmed in slow-motion (from a camera mounted above the hub) is worth a look:

Helicopter Main Rotor Blade In Flight Slow Motion (youtube.com)

A few things to note: The tail boom comes into view each revolution. This is also when the track of the rotor disk is at about its highest point above the line of the horizon so helicopter is undoubtedly in forward flight. Note that maximum angle of blade incidence had been applied much earlier and is already being reduced again by the time the blade passes over the tail boom. There is also not much "flapping" of the blades themselves, rather the whole rotor disk (as apparent from the movement of the hub relative to the horizon) is tilted relative to the horizontal on this hingeless rotor. Shy Torque gave a nice summary in #2 outlining what is happening, also applicable in this Bo105 case.

All the same, given this is a hingeless rotor, it would certainly have some of the characteristics of a gyroscope. So give a Bo105 a solid shove on its skid while it is in a low hover and the helicopter should partly respond like a gyroscope even if rotor aerodynamics may be a more dominant effect.

[megan]

Have a go at this statement from a US Army training manual FM 3-04.203


https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/726x196/helo_b741f697f7a7150d1a20ed654fb870d1d1e6e3f8.png
https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/724x818/helo0_eeb514fc3a9697c22b1e7e1655e6bcdfb54df264.png

[Ascend Charlie]

Megan, looks like a really old manual, maybe from when Igor Sikorsky was an instructor on your course.

Note that it says "precession is not a dominant force", and adds that a rotor exhibits "some" of a gyro's characteristics.

The second section about nose up or down when rolling into a turn is something that I have never observed in 45 years and 15,000 hours of rotary flying. Either I have been totally blind to such things happening around me, or they are confused about what is happening. Rolling into a right turn means the swash plate is causing the blade pitch to be at a minimum over the tail to reach the lowest point at the right side. The whole disc tilts right, the fuselage follows. The "precession" has already happened over the tail and over the nose to make the disc tilt right, it is not a force applied at the right side to tilt the disc and having a "precession" effect 90 degrees later over the nose.

Or is my brain fried after all these years of being bounced up and down at 2:1 and 4:1?

[megan]

looks like a really old manual, maybe from when Igor Sikorsky was an instructor on your courseHere hang on a minute, date of the publication is 7 May 2007, I graduated 56 years ago, and USN if you please, not Army. ;) I said "have a go at this" thinking it might stir things up.The second section about nose up or down when rolling into a turn is something that I have never observed in 45 years and 15,000 hours of rotary flyingMight one take away that you could detect the change in stick position caused by the S-76 PBA, in 6,000 hours I couldn't. :pwhen does it act like a gyro? This answer has to do with how the rotor moves if you put an unbalanced aerodynamic lift on the disc. It will respond by moving at right angles to the unbalance just as the toy gyro does, and it does so in exact compliance with the gyroscopic laws that say the angular rate of motion-the "precession rate" —will be proportional to the applied moment.Is Prouty wrong?

Another discussion on the subject, and where you had the last word AC. :D Me? All this techo stuff is beyond my intellect.

https://www.pprune.org/archive/index.php/t-19678.html

[RVDT]

Megan, looks like a really old manual, maybe from when Igor Sikorsky was an instructor on your course.

Note that it says "precession is not a dominant force", and adds that a rotor exhibits "some" of a gyro's characteristics.

The second section about nose up or down when rolling into a turn is something that I have never observed in 45 years and 15,000 hours of rotary flying. Either I have been totally blind to such things happening around me, or they are confused about what is happening. Rolling into a right turn means the swash plate is causing the blade pitch to be at a minimum over the tail to reach the lowest point at the right side. The whole disc tilts right, the fuselage follows. The "precession" has already happened over the tail and over the nose to make the disc tilt right, it is not a force applied at the right side to tilt the disc and having a "precession" effect 90 degrees later over the nose.

Or is my brain fried after all these years of being bounced up and down at 2:1 and 4:1?

Maybe -

Prouty Helicopter Aerodynamics 2 - Chapter 75 - Some Coupling Considerations

In explaining how a rotor works, we often talk about how the flapping response follows the maximum aerodynamic input a quarter of a revolution later. For our scientific-minded friends, we relate this to a system in resonance or to a gyroscope. It turns out that this is a very good rule-of-thumb that adequately covers most situations, but there are several “Yes, buts”.

Enter Hinge Offset


One of the these is that the resonance theory strictly applies only to rotors with no hinge offset. Thus, the explanation was valid up to about 1950 since all autogyro and helicopter rotors up to that time had been designed that way. The Sikorsky S-52 was the first production helicopter I know of that had hinge offset. The only motivation at the time was that the design of the hub could be made simpler than on the zero-offset S-51. When the test pilots first got in the S-52, they were astounded by the improved control power compared to what they had been used to. We now think of this as the prime motivation for using flapping hinge offset.

With zero offset, as on teetering rotors, if you are on the ground and apply minimum cyclic pitch to the blade directly over the tail boom, the resulting flapping response will be seen to be down on the right side. This also initially happens in the air when the rolling motion is first accelerating. If the helicopter has offset flapping hinges, or a hingeless rotor where flexibility takes the place of an actual flapping hinge, the response angle is not 90 gegrees but something less since the dynamic and centrifugal force effects are not quite balanced and this causes the rotor to operate somewhat off its natural frequency.

Thus, when the minimum cyclic pitch is applied over the tail boom, the rotor produces a large left rolling moment but a small nose-up moment as well (we are talking about American helicopters, of course). The response angle, however, is seldom less than 85 degrees and the resulting cross-coupling is practically unnoticeable to the pilot.

There are exceptions to this. The Eurocopter BO-105, designed in the 1960s, has a very stiff hingeless rotor that acts as if it had a flapping hinge at 13.6% of the rotor radius. Its calculated response angle is 73 degrees and since the moment of inertia in roll is much less than in pitch, the cross-coupling is such that by pulling straight back on the stick, the roll response is more than the pitch response!

As awkward as this might seem, pilots quickly adapt to this characteristic. There are, however, some other adverse effects to so much stiffness and so the next two projects in this line, the BK-117 and the EC-135, have softer hingeless rotors with effective hinge offsets of 12% and 11.8% respectively.

When a Steady Rate is Achieved

What we have been talking about so far is acceleration cross-coupling. A different physical law governs rate cross-coupling. Imagine a helicopter in which the pilot is making the helicopter roll to the right at a constant rate. For this case, there is no rolling moment and therefore no flapping with respect to the shaft; otherwise the roll motion would not be at a constant rate but would be accelerating. (We are ignoring the small aerodynamic roll damping associated with the rest of the airframe.)

To get this steady right roll state, the pilot is holding his stick to the right to obtain an airload distribution that will precess the rotor down to the right as a gyroscope. The airframe will respond by rolling to the right along with the rotor. Since there is no flapping in this steady condition, it does not matter how the blades are attached to the hub.

Where does the rate cross-coupling come from? Compare the environment of the blades on the right and left side. On the right, the blade is going down through the air and thus has a higher angle of attack than the blade on the left, which is going up. This should produce some up-flapping toward the nose, but if the maneuver is such that the helicopter has only rolling motion as we specified, the pilot must be putting in some forward stick to suppress this flapping and its resulting pitching moment.

This results in the minimum cyclic pitch being imposed, not when the blade is directly to over the tail boom, but somewhat later.

The resulting value of this cross-coupling is a function of the ratio of aerodynamic forces to dynamic forces. This ratio is known as the Lock number after a British engineer who developed equations for autogyros in the 1930s. Since the blade flapping inertia is in the denominator of the equation, heavy blades have low Lock numbers and light blades, high. For current helicopters, the range for main rotor blades is from about four to twelve. For a conventional Lock number of eight, the longitudinal cyclic pitch required to keep from pitching is just half the lateral pitch that is being used to maintain the roll rate. The lighter the blade, the more longitudinal cyclic pitch must be used.

The Other Side Of The Coin


The above discussion applies to maneuvering where the pilot is making the rotor do his bidding and the airframe goes along. There is yet another consideration. It is when the airframe is moving and dragging the rotor along with it. This happens, for instance, when the pilot neutralizes his control after a maneuver but the helicopter still has some rolling or pitching rate or when the helicopter has been upset by a gust.

In these cases, the rotor flaps with respect to the shaft to produce a damping moment. For the case of no hinge offset, the cross-coupling effect is the mirror-image of the one that applies in a steady rate case. If the aircraft is rolling to the right without a pilot command, the magnitude of lateral flapping producing a damping moment to the left is equal to the cyclic pitch that the pilot would have used to maintain that right roll rate. This is a result of the fact that flapping and cyclic pitch are related in a one-to-one ratio. For the same reason, there is a corresponding longitudinal flapping producing a noseup pitching moment which is about half the lateral flapping. In other words, there is cross-coupling even in this case.

The situation is a little different if the rotor has offset flapping hinges. Not only is the damping moment larger, but it can be shown that the cross-coupling diminishes with offset and that for conventional blades, a 15% offset would eliminate this coupling entirely so that a rolling velocity would produce no longitudinal flapping. (My thanks to Tom Hanson for pointing this out to me.)

Because all of these cross-coupling effects are different, there is no single adjustment to the control system that will simultaneously eliminate all of them. In most helicopters that I know of, moving the stick directly to the right produces minimum cyclic pitch over the tail boom and the decoupling is left to the skilled pilot. I have been told, however, of two where the designers have attempted to minimize cross-coupling by changing the geometry of the control system within the fuselage. One is Frank Robinson who has designed the control systems on his helicopters such that when the stick is pushed straight forward, the maximum pitch displacement occurs at an azimuth angle of 73 degrees instead of at 90 degrees.

[BraceBrace]

The answer without calculations: it is an effect of highly damped vibrations. If you want to know exact numbers, you would have to apply the theory behind highly damped vibrations, and that theory scared so much the bezjeezes out of me, they were the first papers to hit the bin once I graduated +25 years ago and I decided I wanted to be a pilot.

In the world of "mainstream" pilots, gyroscopic effect is "an explanation" that avoids you have to face reality because that reality is too complex to grasp for many people. If people cannot accept that, I can assure you there are plenty of other "pilot theories" that don't survive any self-respecting bachelor/master in aerodynamics. It's fine. It's not the goal of your/my job. Just keep it simple. Simple keeps the flightdeck alive.

As a pilot you are trained to be an operator, not a designer.

[paco]

I always understood it as simply inertia.

[[email protected]]

Inertia vs aerodynamic damping:ok:

[[email protected]]

So according to Ray Prouty, Lu Zuckerman was wrong - it was 73 degrees not 72 degrees on the R22 rotor head:)

[[email protected]]

Teaching effects of controls on different helicopters with ASE/SAS/STAB off, you can see a nose pitching tendency when rolling into turns - it tends to go up one way and down the other depending on which way your rotors are turning.

[helispotter]

I thought some of you might be interested to see how John S Fay described rotor phase lag in his 1954 book "The Helicopter and how it flies". He then goes on to indicate that "some rotors can therefore be said to behave like a gyroscope in that their phase lag is 90-degrees". So that association has been around a long time. Relevant pages as follows:

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/2000x1439/the_helicopter_and_how_it_flies_john_s_fay_1954_p30_31_b2285 7e6f8dcf275e54d80640f09d8c89e48ad4a.jpg
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/2000x1481/the_helicopter_and_how_it_flies_john_s_fay_1954_p32_33_51e09 db2e033b0e69f448c896cd48d23fc38c4b2.jpg

[[email protected]]

And most people will see that he says that the 'rotor will behave in a SIMILAR way to a gyroscope', not like a gyroscope just in a similar way - he doesn't say it precesses like a gyro does - perhaps it is in English comprehension that the message is lost.

[helispotter]

I once came across the textbook "Helicopter Flight Dynamics" by Gareth D. Padfield (1996) and bought it thinking it would be an interesting read. But it really was much too heavy for me! None the less, hope Gareth doesn't mind me sharing a pair of extracts from the book, one on "The fundamental 90 deg phase shift" (page 36) and the other on "pitch to roll and roll to pitch couplings" (page 417). Some light bed time reading:

Page 36 extract:
https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/1441x805/helicopter_flight_dynamics_phase_shift_935396b8fbc3cc9de1fff aa5367429759cf86dea.jpg
Page 417 extract:

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/1429x1481/helicopter_flight_dynamics_pitch_roll_coupling_759b0ce0753a2 fdd87578cee421f46ee049e6936.jpg

[paco]

Don't let EASA see that - the silly beggars will turn it into a question :)

Bell once used blades on a Bell 206 that were double the normal weight and they ended up with a gamma of 180°! In fact, the blades had so much energy that there was also no H/V curve.

[JimEli]

I thought some of you might be interested to see how John S Fay described rotor phase lag in his 1954 book "The Helicopter and how it flies". He then goes on to indicate that "some rotors can therefore be said to behave like a gyroscope in that their phase lag is 90-degrees". So that association has been around a long time. Relevant pages as follows:
“Some rotors can therefore be said to behave like a gyroscope in that their phase-lag is 90 degrees.”

FWIW, I believe the reference is to the Bell-Hiller rotor system, although not explicitly stated.

[helispotter]

...Bell once used blades on a Bell 206 that were double the normal weight and they ended up with a gamma of 180°! In fact, the blades had so much energy that there was also no H/V curve.

paco, you motivated me to search the internet for more about these tests and the test report is publicly available at:

https://apps.dtic.mil/sti/tr/pdf/ADA071648.pdf

The report titled "Flight Test Evaluation of the High Inertia Rotor System" was produced by Bell Helicopter Textron in June 1979. The tests used a modified prototype OH-58A and evaluated three different rotor inertias with the lowest being similar to the rotors of the standard OH-58A and the highest being more than double that inertia. Blades were not necessarily double the standard weight, rather the high inertia was achieved by adding more tip masses to the modified rotor system. Page 40 shows the H-V curve for the standard and three different inertias. No limit curve for the highest inertia as you said. Page 96 reports a case of apparent entry into VRS for one of the test points with the helicopter contacting the ground but then becoming airborne again due to the available inertia! Page 97 discusses the more sluggish response of the higher inertia rotor, but addressed by incorporating a "control quickener".

[paco]

Thanks for that - I will add that to my information junkie's reading list!

[Aluminium Mallard]

Robbiee, you'll like this one.

Sitting in my helicopter on a wild day with rotors running, my AI showed every heave and toss of the ship. My rotor stayed locked in its plane parallel to the deck. The AI is a gyro, the rotor is no!

This is a bit misleading, the AI is in a gimbal where the helicopter and rotor system is fixed to the deck.

For the record i'm in team flapping!

[[email protected]]

But the AI accurately represents the position of the horizon demonstrating rigidity in space.

The helicopter wheels may be lashed to the deck but the disc is free to flap, only limited by the pilot's vice-like grip on the cyclic.

[JohnDixson]

The rotor coupling response suggests behavior more like a rate gyro, at least in the machines I’ve been exposed to with reasonably broad maneuver envelopes. The S-67 was an interesting example. It did have the electronics from the CH-54B Skycrane installed, but flew so well without ( it did always have the stick force per G, Feel Augmentation System on ) that we never set up the gains and it remained N/A.

During the demo tours in the USA ( 1971 ) and UK/Germany/Iran/Greece ( 1972 ) probably 2-300 pilots got to fly it, and the standard flight included a split S and a roll: one each by the SA pilot flying with the guest pilot on the controls and one each by the guest pilot with the SA pilot helping as needed*. Roll Procedure was simple: put the nose down 10-15 degrees ( any angle ok-just hold that pitch attitude, then set collective around 70%Q ( anything around that was fine ) when you got to around 170KIAS pull the nose up to around +15 degrees-again, anything around that was OK, and when the speed dropped to around 130-140 or whatever, put the cyclic on the right stop**, and watch the world go around. No need to move anything until the world was level again. Roll took about 4 seconds plus a bit and the aircraft would, without any longitudinal correction, come out about level. So, with that 12 inch flapping offset main rotor, the coupling was absolutely there, but easily manageable.
*One of the gust pilots in Germany was former Luftwaffe Chief of Fighters Adolf Galland. He needed no help doing anything.There was one UK Spitfire WWII pilot of high rank and multiple decorations whose name escapes me now, but who walked very unsteadily with a cane up to the 67, and needed help from two people getting into the 67 front seat, but once there, like General Galland, needed no help in maneuvering the 67..
**And yes, we did rolls to the right only, but not for any aerodynamic or dynamic coupling reasons but because in left rolling maneuvers the tail rotor edgewise stresses were high enough so that we would have to cycle count the maneuvers if we went the other way ( tail rotors had a flapping hinge but did not incorporate a drag hinge ).
This post is a bit off subject but indicative that the coupling induced higher rate maneuvers are handled naturally by the pilots.

[Robbiee]

This is a bit misleading, the AI is in a gimbal where the helicopter and rotor system is fixed to the deck.

For the record i'm in team flapping!

Its also misleading because the comparison of a rotor to a gyro is about how a force applied to it is experienced later in the direction of rotation, not its stability characteristics.

,...but I'm team teeter. :cool:

[Wide Mouth Frog]

So this has been a useful debate.

We seem to agree that the rotor does not demonstrate one key feature of a gyroscope, namely rigidity in space. The question I think we're now trying to answer is whether the control lag for a helicopter rotor is 'like a gyro', ie. governed by the same kinematics as a gyro, or 'like a gyro' in the sense that it has similar observable characteristics but no connection to the kinematics of a gyro.

And then when we've answered that we can debate whether the gyro simile is an appropriate teaching tool for helicopter pilots. I would say that if the former prevails, then there's a qualified case for it. If the latter, then probably not.

[[email protected]]

I think the former is demonstrably wrong and the latter is only true of teetering rotors.

Therefore using gyroscopes as a way to teach rotor behaviour simply ignores the reality of basic aerodynamics - why would you do that?

If you want to be a pilot, learn some aerodynamics - if you want to be a physicist, learn gyroscopes.

Some of the advanced texts quoted here show that in SOME rotors, it is possible to explain cross-coupling effects using gyroscope tendencies but those aren't for PPL, CPL or even possibly ATPL study.

Dumbing down training to make it 'easier' is a great way to cause more accidents through ignorance.

[paco]

"Dumbing down training to make it 'easier' is a great way to cause more accidents through ignorance."

If you want proof, just look at the EASA questions.

[BraceBrace]

If you want to be a pilot, learn some aerodynamics - if you want to be a physicist, learn gyroscopes.

That is only valid up to a certain point, and reality has shown it has an equally dramatic downside: the overthinking pilot. He crashes quicker than anybody else.

A pilot needs skills, not theory. Theory is required to let the person understand and train a certain required skillset, but it is what it is: background foundation. Otherwise Usain Bolt would be an expert in body dynamics. Or the Euler equations would be written down on every pilot kneeboard.

You might feel "better prepared" because your "theory" is of another level. The same applies to you unfortunately. There is a limit to what you know and apply. At the end of the day what the "theoretical" pilot needs to realise is that his "aerodynamics" is nothing more than fluidodynamics with a tuned down vision on compressibility (we consider it incompressible for a lot of our thinking). Once we enter that zone things get quickly rough for many pilots, especially when discussing rotor dynamics.

Keep it simple, that keeps it safe.

[[email protected]]

That is only valid up to a certain point, and reality has shown it has an equally dramatic downside: the overthinking pilot. He crashes quicker than anybody else. got any evidence to back that assertion up?
It flies in the face of what I have experienced in 42 years of flying.

Underthinking pilots who underprepare because they think simply learning to control the machine in a straight line makes them good pilots.

[BraceBrace]

got any evidence to back that assertion up?
It flies in the face of what I have experienced in 42 years of flying.

Underthinking pilots who underprepare because they think simply learning to control the machine in a straight line makes them good pilots.

Plenty of examples after 6 years in engineering, followed by 18 years in aviation of which 7 years in training people with different backgrounds.

The thinker is always late, he is one of the most difficult people to train as his natural problem handling process is to think about it when he's supposed to act. Understanding is not a problem solution. You still die if you understand the reason why you're dying and the acting came to late. Overemphasising technical knowledge creeps into the ego of many people, and claims an idea that "they know". They usually don't, as even the most advanced theoretical pilot training is limited and does not tell full stories.

Ask any old pilot to explain the theory behind his flying, he will not be able. It doesn't matter to know the why. It matters to know how to act appropriatly.

Keep it simple saves lifes. Complicated theory wastes time.

[Robbiee]

"Dumbing down training to make it 'easier' is a great way to cause more accidents through ignorance."

If you want proof, just look at the EASA questions.

No one is dumbing down training. They're only dumbing down the engineering and physics stuff that is absolutely useless in the cockpit.

Unless of course, you want to regale me of the day where knowing the "true reason" the pitch horns are offset saved you from crashing, lol.

[PPRuNeUser0211]

Plenty of examples after 6 years in engineering, followed by 18 years in aviation of which 7 years in training people with different backgrounds.

The thinker is always late, he is one of the most difficult people to train as his natural problem handling process is to think about it when he's supposed to act. Understanding is not a problem solution. You still die if you understand the reason why you're dying and the acting came to late. Overemphasising technical knowledge creeps into the ego of many people, and claims an idea that "they know". They usually don't, as even the most advanced theoretical pilot training is limited and does not tell full stories.

Ask any old pilot to explain the theory behind his flying, he will not be able. It doesn't matter to know the why. It matters to know how to act appropriatly.

Keep it simple saves lifes. Complicated theory wastes time.

Tell you what kills pilots quicker than being over-trained... Being under trained. I've seen plenty of people come a cropper because they didn't understand a system. If you're having to act rather than think about it, you did something wrong a while back. If you subscribe to the "you don't have time to think up there" school of thought, in my opinion you're probably doing it wrong.

[Robbiee]

Tell you what kills pilots quicker than being over-trained... Being under trained. I've seen plenty of people come a cropper because they didn't understand a system. If you're having to act rather than think about it, you did something wrong a while back. If you subscribe to the "you don't have time to think up there" school of thought, in my opinion you're probably doing it wrong.

If you DO have time to think up there, you've never flown an R22. :}

[PPRuNeUser0211]

If you DO have time to think up there, you've never flown an R22. :}
See "you've probably already made a mistake" - by crewing into an R22...

[[email protected]]

If you DO have time to think up there, you've never flown an R22. :}

I have and there is plenty of time to think - more people have been killed in Robinsons by acting without thinking.

[[email protected]]

Ask any old pilot to explain the theory behind his flying, he will not be able. I can and so can many of the experienced aviators on this forum plus many hundreds I have flown with over 42 years (of which 35 have been as an instructor).

Knowing how to act appropriately comes from quality training and practice - especially when under stress from complex scenarios or emergencies.

If you are an engineer then I assume you were taught in some detail and weren't expected to just 'act appropriately' when managing or fault finding complex systems - you relied on detailed knowledge.

[paco]

Theory is important - to paraphrase Oscar Wilde, you can never have too much. Knowing how the vectors move helps you realise why you don't need to move the collective when you come in to ground effect. Just sayin'.

[Ascend Charlie]

Oh, Paco, you just opened the door to the "bubble of high pressure air under the disc" myth. Where's the popcorn...

[BraceBrace]

If you are an engineer then I assume you were taught in some detail and weren't expected to just 'act appropriately' when managing or fault finding complex systems - you relied on detailed knowledge.

In engineering you are thought to think logical and start from A to derive Z. On the flightdeck there is no time to go through that process.

As a pilot you are an operator. Your brain and body cannot even handle information at the input like an engineer. It is not possible. Forget that. What you do is you learn sitting at a desk, processing information, but then once on the flightdeck this has been vastly simplified otherwise you cannot use it in time critical scenario's.

Don't get me wrong, I respect background knowledge, and have had many discussions... at the bar. I am by heart an engineer and love it. But it has very very limited place on the flightdeck. There have been too many cases where you were wondering why the person was not doing anything. He was thinking. And many times a person does not even reach the process of thinking. You wanted examples? AF447 is a prime example of how, if you cannot simplify things on the flightdeck and stay stuck in complexity, you don't even reach the act of thinking. Very basic rules would have saved that aircraft, not complex theory.

Technical knowledge is important yes, but in modern day of aviation it creates a fake bubble where pilots feel protected by their knowledge, while at the end of the day, they don't know sh$t about the tool in their hands. You are an operator, learn to be an operator. That is a SKILL. Not a knowledge.

Keep it simple. Know your theory up to the point where it allows you to stop stupidity. If that is gyroscopic precession, fine. If that is highly damped vibrations, fine. So yes, I love this thread, but it's not going to make you a better pilot. Just nice discussions at the bar (which you can always invite me to :-))

[paco]

Nothing to do with bubbles.... I'm talking about how the machine stops going forward all by itself. And talking of Nock Lappos:

“Pure book knowledge should be impeccable - every second of doubt about "what do I do now?" is worth 30% of workload. Mostly because the self-doubt and second-guessing are real time and mental capacity wasters. The more you know flat cold, the easier it is to fly under the gauges”

[ShyTorque]

In engineering you are thought to think logical and start from A to derive Z. On the flightdeck there is no time to go through that process.

I once went through a recruitment process for a large company who were recruiting both pilots and engineers at the same time.
As part of that process there were various aptitude tests, based on ones used by the military.
One test was to enter a room where an invigilator at a desk (actually the HR manager) pointed out the rules, which were to remove a number of assorted objects, some large and heavy, some small and light, from a taped off area on the floor. There was a bag of "implements" that could be used to remove the objects, but each one could be only used once. No objects could be touched by hand. There was a time limit, twenty minutes iirc.

Myself plus two other pilots were sent in. None of us knew each other and we had only met earlier at the recruitment event - and were in effect competing for a job. As we were told "Go", we emptied out the bag of implements. There were ropes, canes, short pieces of wood etc and not much else. We had a quick individual think, a short consultation and then got on with it. We completed the task in less than half the time. The invigilator said because we had removed all the objects she wanted us to put everything back as it was whilst she kept the clock running. We did that, too, inside the original time.

The HR manager told us in the debrief that we were the first group of pilots she had put through the test and that she was very surprised how well we worked together and got it done. Only engineers had been put through before and NONE of them had ever finished within the time limit because they spent a great deal of time discussing the task and coming up with alternative theories.

[Robbiee]

In engineering you are thought to think logical and start from A to derive Z. On the flightdeck there is no time to go through that process.

As a pilot you are an operator. Your brain and body cannot even handle information at the input like an engineer. It is not possible. Forget that. What you do is you learn sitting at a desk, processing information, but then once on the flightdeck this has been vastly simplified otherwise you cannot use it in time critical scenario's.

Don't get me wrong, I respect background knowledge, and have had many discussions... at the bar. I am by heart an engineer and love it. But it has very very limited place on the flightdeck. There have been too many cases where you were wondering why the person was not doing anything. He was thinking. And many times a person does not even reach the process of thinking. You wanted examples? AF447 is a prime example of how, if you cannot simplify things on the flightdeck and stay stuck in complexity, you don't even reach the act of thinking. Very basic rules would have saved that aircraft, not complex theory.

Technical knowledge is important yes, but in modern day of aviation it creates a fake bubble where pilots feel protected by their knowledge, while at the end of the day, they don't know sh$t about the tool in their hands. You are an operator, learn to be an operator. That is a SKILL. Not a knowledge.

Keep it simple. Know your theory up to the point where it allows you to stop stupidity. If that is gyroscopic precession, fine. If that is highly damped vibrations, fine. So yes, I love this thread, but it's not going to make you a better pilot. Just nice discussions at the bar (which you can always invite me to :-))

****in aye bubba.

There's a reason its called a "Pilot Certificate" and not a "Pilot Degree". Being a good pilot is about skill and experience, not book smarts.

[helispotter]

...Only engineers had been put through before and NONE of them had ever finished within the time limit because they spent a great deal of time discussing the task and coming up with alternative theories.

Speaking as an engineer, and at risk of generalizing, we are probably not the best time managers!
But I wonder if those engineers may have done better if left to do the task individually rather than debating alternative approaches as a group!?

We did an exercise along these lines years back in a mixed group. One instruction was that nobody could put their feet over a marked line. Simple enough instruction. I thought the team needed a "guard" to make sure this rule wasn't breached, but I couldn't even suggest that before someone had already stepped over the line and we were "out".

As for theoretical knowledge vs applied ability, I understand how sailing boats operate in wind and water but when in sailing competitions, our team always came last or near last, so we gave up!!

Now: back to the theory of rotor dynamics... haaa haaa, haaa.

[[email protected]]

On the flightdeck there is no time to go through that process. That is patently untrue and the existence of emergency checklists demonstrates this - the flashing white glove around the cockpit has caused far more accidents than knowing too much about the aircraft.

The Air France accident was caused by not knowing how the AP worked or understanding the hierarchy of control on the sidesticks - yes Attitude Power and Trim would have saved the day but being swamped with information and panicking because you don't understand it is how to kill hundreds of people.

Perhaps people get too hung up on the word pilot - your abilities as a pilot depend greatly on how you were trained, not just for your PPL/CPL, but beyond that to do the required job with the aircraft.

A PPL can call him/herself a pilot but is generally only capable of basic manoeuvres and simple navigation - CPL takes that up a notch and allows you to earn money flying - ATPL goes up several extra notches again.

What is the difference between these levels? Experience, training and KNOWLEDGE.

If all you do is GA flying as a PPL or tour flying as a CPL, do you really think you have the skills and knowledge of an ATPL holder?

Now plenty of people are happy with the level they get to and that is great but on this forum there are a lot of very experienced and well-qualified pilots from all walks of life who have pushed themselves (or been pushed) to expand their skills and knowledge to make them better pilots.

So when statements are made regarding pilot skills, knowledge and abilities, especially with regard to the training required just remember there is a very long way between PPL and Test Pilot and what suits PPL training won't cut the mustard with more advanced levels.

[JimEli]

If you DO have time to think up there, you've never flown an R22. :}

April Fool.

[BraceBrace]

That is patently untrue and the existence of emergency checklists demonstrates this - the flashing white glove around the cockpit has caused far more accidents than knowing too much about the aircraft.

The Air France accident was caused by not knowing how the AP worked or understanding the hierarchy of control on the sidesticks - yes Attitude Power and Trim would have saved the day but being swamped with information and panicking because you don't understand it is how to kill hundreds of people.

Did you re-read your post? You just made my point. The checklists is the most basic simple protection humans have designed because... the brain ain't that good. This has nothing to do with the white glove. The Air France accident was caused by overreliance in automation and pilots inadequate to pick up the error because... the brains were overloaded.

If they had kept their brain focused on basic & simple aerodyn - hence disregarding all technical messages - they would have realised that high altitude, a pitch up of 20° is simply not surviveable as TOGA power is nothing compared to what is available on the ground. And exactly this SKILL is the part UNDERtraining is discussing and where all regulations have been adapted with extra high altitude upset recovery excercises.

Pilot technical knowledge as explained in FCOMs is what I call "blackbox theory". It says a little about what comes in, and a little about what comes out. The rest is a giant black box. That knowledge is basic and not to be overrated. Our job is to stay within the controllable flight envelope. If a system is not working, we switch it off. If there is an alternate, we use the alternate. Simple.

Anyway, I'm going to leave it at that, I made my point boringly enough. Back to rotor dynamics (if one still dares :-))

[[email protected]]

Did you re-read your post? You just made my point. The checklists is the most basic simple protection humans have designed because... the brain ain't that good. This has nothing to do with the white glove. The Air France accident was caused by overreliance in automation and pilots inadequate to pick up the error because... the brains were overloaded.
Yes, I wrote what I meant to write - mandating the use of an emergency checklist isn't because our brains are no good, its because we are often too quick to assume we know what has gone wrong and are often incorrect.

Many complex failures have only been survived because of the detailed knowledge of the systems by the crews involved.

Most of the pilots I trained with in the military could do the whole start and stop checklist from memory along with the emergency drills so the brain isn't the problem there - stress is the problem where the brain tries to go from A to Z ignoring B to Y on the way and why dumbing down to Pavlovian responses based on very basic information just doesn't work.

The Air France pilots were confused by the number of alerts and warnings they received and the unexpected response from the aircraft since they were both trying to fly it at the same time (doesn't work with sidesticks). They simply failed to fly the aircraft - and when that happens you are on a hiding to nothing whether you know everything or nothing about the machine.

[JimEli]

Lion Air Flight 610 crashed on 10/29/2018, twelve minutes after takeoff killing all 189 passengers and crew. Five months later, Ethiopian Airlines Flight 302 crashed six minutes after takeoff killing all 157 people aboard.

Both aircraft were Boeing 737 Max 8s with a Maneuvering Characteristics Augmentation System (MCAS). MCAS is activated without the pilot’s input, which has led to some frustration among pilots of the 737 Max jet. Both jets crashed because MCAS responded to faulty inputs.

The FAA pilot transition into the Max 8 didn’t involve any flight training (simulator or otherwise). Pilots instead simply learned about the 737’s new features on an iPad. Pilots at United Airlines had a 13-page guide to learn the 737 Max. They didn’t mention the MCAS.

MCAS was deemed unnecessary information by Boeing and hence the FAA and EASA.

Knowledge beyond what the FAA/EASA requires isn’t worthless and extraneous book facts. And experience isn’t just a learned skill a pilot pulls out at a suitable time like a parroted bit of rote memorization.

Some of what I read here is disconcerting and downright idiotic. The best pilots I’ve met are the ones who thirst for knowledge beyond the required, think and then apply it up there.

[megan]

Some of what I read here is disconcerting and downright idiotic. The best pilots I’ve met are the ones who thirst for knowledge beyond the required, think and then apply it up thereAn example of the thirst for knowledge is represented by the attached take off data chart.for a S-76C. Depending on the circumstances complying with this chart was guarenteed for your day to end badly should you think you had Cat A ability. The company refused to address the issue for years and the broad body of pilots were unaware they had their necks in a noose.


https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/696x1000/fr003_7311a7c2f1c553df277bfe7a65659b801e9c1326.jpg

[ShyTorque]

I just read this thread again after a few days away. It seems to have suffered from terminal precession because what I missed has nothing to do with the title.

[JimEli]

I just read this thread again after a few days away. It seems to have suffered from terminal precession because what I missed has nothing to do with the title.





I once went through a recruitment process for a large company who were recruiting both pilots and engineers at the same time.

…
Only engineers had been put through before and NONE of them had ever finished within the time limit because they spent a great deal of time discussing the task and coming up with alternative theories.


https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/256x171/facepalm_d080bacbec296adc4bb3e3e49e6605391dcd1072.png