Nick - another why does this happen...

[[email protected]]

Cyclic position vs roll rate.

In a US configuration helo when you roll rapidly to the right (wingover, downwind quickstop etc.) the roll rate increases rapidly and requires cyclic input considerably left of the wings level position to stop the roll and even more to reduce it. To the left - more cyclic is needed to produce the same rate of roll which is easily arrested with a central cyclic position. Why? does this have to do with the fact that the disc is being loaded during the manoeuvre and is therefore a cross coupling or is it something else. A helo with the blades rotating clockwise produces the opposite effect - eg to achieve a given roll rate less cyclic is required towards the advancing side than the retreating.

[Steve76]

Thrust from TR to the right
Thrust from MR to the right
Throw in Gyroscopic effect = answer:D

[Nick Lappos]

I havn't responded mostly because I am baffled. I have not seen the difference in control power or damping in left vs right in the first place, and intend to look some data up to see.

The tail rotor is a possible answer if the effect is real, but the typical Jet Ranger has a very low tail rotor, so there is little roll effect into it. For an S-76, the TR is large and high, but the roll effect is not apparent to me.

I would subscribe to the opposite effect for US helicopters at altitude and at mid to high speed. Left rolling maneuvers unload the retreating blade, and so are much snappier than right rolls, which demand more lift from the retreating side.

[[email protected]]

Nick, I don't believe the TR is an issue but I am prepared to be proved wrong. The rate of roll is not as noticeable as the amount of opposite cyclic required to oppose the roll and recover to wings level. In the Lynx in a 60 degree AoB downwind quickstop to the right or a wingover using 90 degrees AoBto the right, almost full left cyclic is required. The same sort of input is required in the Sea King during similar manoeuvres. One test pilot once muttered something about manoeuvre stability boundary but I didn't fully understand his explanation which I am sure didn't differentiate between the direction of turn.
The Gazelle definitely responds in the same, although opposite way and rolls left much more readily than right and requires a lot of right cyclic to roll out from a left wingover/quickstop.
All the above relates to flying stab out so AFCS/SAS saturation is not a player.
I hope you can find an answer or tell me I am imagining it.

[Nick Lappos]

I don't douibt your assertion, just havn't noticed it. I will look into it, it is interesting!

[ShyTorque]

I have noticed a similar phenomena in the S-76; in a fairly tight turn at about 60 kts, the aircraft tends to "tuck in" to the turn and the nose tends to drop. It needs opposite cyclic to control it.

[sycamore]

10 p`nnth ,which could also be rubbish.. If you are measuring roll-rate in level flight there may be a slight difference due to the rigging of the head/stick to offset translational effects/sideslip,and any gearbox offset/tilt to give a levellish fuselage attitude.If it`s only noticeable during transients,like d/w quickstops,then I think it is a flap-back/roll interaction,with t/rotor interaction from the "attitude" in relation to the rotor and fuselage c of g--ie the a/c wants to change ends ,but quicker than you thought.I`ve seenGreenham Common runway thru` the roof panels of a Sea-king with CO`s and training officers as Display Pilots and thought-I hope the big arrow "L" knows which way it is pointing!! I also saw a new young Sqn.Ldr practicing a d/w q/stop at Ternhill,unfortunately,he didn`t get all the mighty Sycamore`s 550 hp under his armpit ,and ended up running on at about 50 kts and spreading t/r bits all over the airfield,and he didn`t get ground-resonance.We lesser mortals on the course we nt and had another coffee,and contemplated our future.!!! Very observant of you anyway Crab,you should apply for ETPS,and you`ll probably be asked at the interviews"what about roll-rate------??Keep your balls in the middle,I say..:p

[Fortyodd]

Crab,
If you have noticed this on the Lynx then go and speak to Bloo Anderson who will give you a complete demonstration/explanation.

[[email protected]]

Fortyodd, Bloo was my boss on 671 and, as excellent a pilot as he is, did not have the answer to this one.

Sycamore - I don't think the starboard lateral lead of the Sea King mixing unit is a factor, the Lynx doesn't have this and still needs loads of left cyclic to roll out from a quickstop/wingover to the right. Upside down in a Sea King - rather you than me, no problem in a Lynx however. As for ETPS - too old and crap at maths!

Nick - just a thought about the slope of the CL curves on the opposite sides of the disc - the retreating side is at high AoA and a one degree pitch change would produce a bigger increase in CL than the decrease on the advancing side which is operating at low AoA (and therefore presumably on a shallower part of the CL slope). The only problem with this thought is that it ought to work the same way in a roll to the left.....ah well, back to the drawing board!

[vorticey]

crab: i recon the tail rotor would be the magor factor in the roll rate problem. the helicopter naturaly wants to tip over right with the main rotor turning clockwise.

nick: wouldnt the low bell tail rotor have more of a rolling moment than the high 76 one? (if the tail rotor was behind the main rotor, no rolling would take place).
and the pitching up you talk about i would put down as gyroscopic pressesion. with the disc spinning clockwise and right cyclic applied the disc would start tilting right and pressesion would advance the rolling movement in the direction of rotation (tending to a pitching up attitude) but the blades would feather because of the cyclic position leaving the disc at a aft of right rolling position. of cause as soon as the bank angle is reached and the roll rate stopped, the pressesion stops?
:confused:

[[email protected]]

Vorticey, the Lynx and Sea King have rotors which rotate Anti-clockwise when viewed from above so your theory does not hold water. BTW see other threads for my thoughts on precession and rotors systems but don't ask Lu Z.
If the tail rotor was such a major player, each time you put an input in yaw you would get a roll in the opposite direction - in fact the opposite happens (eg yyaw left - roll left)due to changing the relationship of the control orbit to the direction of travel.

[Flare Dammit!]

Every helicopter I've ever flown rolls one way more quickly than the other depending on rotor system direction of rotation. Pilots who haven't noticed this either have very little flight time/experience or haven't been paying attention very closely. I haven't yet figured out exactly WHY they do it, only that they do.

[helmet fire]

I have noticed this tendency as well, particularly evident on the UH 60.

To roll right, as you argue Crab, the CL changes roughly the same on the right as the left, albeit in oppposite directions. It is your assertion that they therefore equal out that I dont agree with. For example, when you roll toward the retreating blade in forward flight, you require more power, and this “roll induced torque spike” is readily demonstrable. This is because the reduction in drag created by the reduction in lift (AoA) on the retreating blade is exceeded by the increase in drag created by the increase in lift on the advancing side. This has the overall net effect of increasing total rotor system drag, thus requiring more torque until the roll rate stops. The imbalance is due to the fact that V is squared in both the lift and drag equations, thus the effects of changing AoA between the advancing blade and retreating are disproportionate. The V squared creates an exponential curve, not a linear one, and if I could remember the correct chart to use, it can be plotted out and demonstrated diagrammatically. Damn those memory cobwebs.

Do you think that this roll induced torque spike may have anything to do with your roll rate question? It would seem logical (though most helo subjects ARE NOT :rolleyes: ) that it would be easier and faster to roll in the direction of less power. Same as it is easier to begin a rate of descent, than it is to start a climb.

Sorry if I have confused the issue.


:)

[[email protected]]

Flare Dammit - I don't know why it does it either - that's why I posted the question to Nick.

Helmet Fire - I completely agree with the business about torque spikes and the overall change in rotor drag (see my post on the Aerodynamics thread). However, in searching for an explanation for the disparity in roll rates I have tried to consider all sorts of different ideas. It is a fact that the slope of most blades CL curve is not constant - generally at low AoA the slope is shallower, increasing in steepness towards CL max. My suggestion therefore, was that as the retreating side is operating at higher AoA than the advancing side, then the increase of CL on the retreating side during the roll was greater than the reduction in CL on the advancing side.

I will be very happy if Nick can come up with an explanation.

[vorticey]

my mistake i thought "us configiration" was clockwise rotors.

you said: If the tail rotor was such a major player, each time you put an input in yaw you would get a roll in the opposite direction - in fact the opposite happens (eg yyaw left - roll left)due to changing the relationship of the control orbit to the direction of travel.

not realy! a yaw in direction of rotation even in hover will cause a roll in the same direction, not opposite. the reason it affects roll so much in flight is flap back. if the cyclic is held at the same compass direction during a yaw roll wont occer.
:eek:

[[email protected]]

Vorticey, If you start at the beginning of the thread you will see I have been talking about an aircraft rolling into a turn - not exactly a manoeuvre carried out in the hover is it? You have clearly misread the part in the post you quote where I point out that a yaw input in forward flight (without moving the cyclic or collective) produces a roll in the SAME direction - this is the secondary effect of yaw. I have only demonstrated effects of controls a few thousand times but I seem to remember that the whole point was NOT to mask the secondary and tertiary effects of moving a control in isolation.

[heedm]

In forward flight, the helicopter's equilibrium is affected by CG, lift vector, drag, tail rotor effects, etc.

To roll that helicopter you tilt the disk so the lift vector and weight create a couple. Once they no longer create that couple, rolling stops. Of course, the attitude may not have been level in equilibrium. This means the couple may be a different magnitude for equalt left vs right tilting of the lift vector.

When you input cyclic, you induce a cyclic pitch change that results in the disk tiliting. As pointed out previously, the amount of that change is subject to the blade pitch while in equilibrium, relative flow velocities, amount of flapping, etc.

There's also a rigging factor to consider. If roll in the collective does not create a linear change in blade pitch, then displacement left vs displacement right would only cause the same pitch change if the equilibirum were at a point of symmetry in the roll rigging.

That's some of the stuff I considered may explain this phenomena. After thinking through that list I realized it would be more incredible if the same input resulted in the SAME roll rate vice resulting in different roll rates.

I think the only way that roll rates could be balance would be if it were designed that way...that may come at the cost of something else.

[[email protected]]

Heedm, this rate of roll situation (I am very reluctant to call it a phenomenon) is apparent in every helicopter I have flown and many more besides - witness some other posts on this thread. Each of these helicopters is designed differently with different control systems, different number of blades, different direction of rotation, different hinge offsets etc. etc. The only common factor is that they all exhibit a tendency to roll better/faster towards the advancing side which rather indicates it is a generic helicopter fact of life and not due to specific rigging. The sort of thing you are probably alluding to is Sikorsky's 'starboard lateral lead' , evident on the Wessex and Sea King where the output from the mixing unit is modified so that on application of collective, the starboard lateral jack is displaced slightly more than the port to help counter increased TR drift and roll as AUM and therefore hover power increase. On winching platforms such as these, more TR drift requires more left cyclic to maintain station producing more roll thus affecting the proximity of the winch wire to the fuselage (presuming the winch is on the right).
I know that test pilots carry out a stick plot for sideways flight as well as roll response to ensure sufficient control margins remain for safe flight which is why I asked Nick if he (as a mega test pilot God) could shed some light on what I and others have noticed.
Inherent sideslip (due to the TR thrust) in forward flight would tend to produce an opposite roll due to dihedral effect and flapback which works in opposition to the roll rate 'phenomenon' so I am still stuck for an answer.
This might be one of those sort of questions I have been asked by students where the final answer is " It just does, OK"

[vorticey]

would it have somthing to do with the position of the cyclic during foward flight? ie, right and foward of the hover position (anti clockwise rotation?
would the positions you are talking about be the same distance from the flight position??
:confused:

[Flare Dammit!]

Crab wrote:

(snip)...I point out that a yaw input in forward flight (without moving the cyclic or collective) produces a roll in the SAME direction - this is the secondary effect of yaw.

Whoa! Hold on! Crab, it has been my experience that in many small helicopters, a slight yaw to the right will absolutely produce a roll to the LEFT due to the extra drag caused by the the cabin being out of trim. And vice-versa. And it's very dangerous at high a/s in underslung systems because it plays hell with the flapping angle and mast/hub clearances. ...As many dead Cobra pilots can attest.

This is the opposite of the "dihedral effect" we've come to know and love in airplanes (where you can pick up a dropped wing with opposite rudder). Remember, our tail rotors are attached to the airframe, so yaw changes do not immediately effect the rotor...which is why it's harder to hold a localizer with pedal adjustments as you can do in a plank.

It is quite easy to maintain straight and level flight in a helicopter with the cyclic frictioned down tightly. Trouble is, yawing also makes the nose drop, so pedal inputs have to be tiny.


To Vorticey. You wrote:

would it have something to do with the position of the cyclic during foward flight? ie, right and foward of the hover position (anti clockwise rotation)?
would the positions you are talking about be the same distance from the flight position??

Sorry, matey, but the roll rates actually don't have anything to do with cyclic position.

[[email protected]]

Flare dammit - no comprendez senor 'roll due to drag cause by the cabin being out of trim'?Que? The back of the aircraft is untidy and causes a roll? no it must lose something in the translation.

I can explain 'yaw left-roll left, yaw right-roll right' which is simply because the control orbit is no longer coincident with the direction of travel and the high point of the flapping back disc has moved. Can you explain yaw left roll right a little more succinctly?

I am no fixed wing guru but I believe dihedral effect is the roll in the opposite direction to a sideslip due to different angles of attack between the 2 wings in this condition. As I remember, the picking up of a dropped wing with opposite yaw makes one wing go faster and the other slower, therfore giving the wing with the higher Vsquared more lift.

As for holding the localiser with yaw, unless you physically move the whole aircraft in space eg turn onto a new heading and change it's position relative to the centreline, you will continue to sideslip left or right of the centreline.

[Flare Dammit!]

Crab wondered:

Flare dammit - no comprendez senor 'roll due to drag cause by the cabin being out of trim'?Que? The back of the aircraft is untidy and causes a roll? no it must lose something in the translation.

Hooooo-kay, here we go.

Not just the back of the aircraft, the WHOLE aircraft (fuselage). Imagine a big rectangular slab of wood (longer in length than height), suspended by one attach link at its midpoint, flying through the air edge-wise. Streamlined, right? Now turn (yaw) the piece of wood to an out-of-trim condition. Which way is it going to lean (bank)? I can assure you that it will not lean in the direction that it is turned.

Speaking mainly of underslung systems (but it happens in even the multi-blade systems I've flown), this is what causes the fuselage of a helicopter to bank in the opposite direction of yaw. Try it! It has nothing to do with the stability or lack of stability of the rotor, which is another story altogether. The rotor will eventually but not immediately respond.

As for holding the localiser with yaw, unless you physically move the whole aircraft in space eg turn onto a new heading and change it's position relative to the centreline, you will continue to sideslip left or right of the centreline.

Well...in a helicopter, yeah. But we have two separate entities flying through the air: the fuselage and the rotor. Sometimes they act with surprising independance. You could yaw the fuselage quite a bit and the rotor will happily continue along on whatever heading it was "trimmed" for (and by that I mean whatever position the cyclic was in that kept things in equilibrium).

But in a plank, yawing the aircraft without a corresponding opposite aileron input will cause the ship to wander off on its new heading, more or less. Making a yaw input in an airplane with positive dihedral effect will cause the ship to roll in that direction. With no ailerons, a fixed-wing can still be controlled well enough.

Hope that clears it up.

[[email protected]]

FD, Now try deliberately sideslipping the aircraft eg cross controlling on an approach - put left pedal in to hold a heading 20 degrees off your line of approach and which way will you have to move the cyclic to keep flying the approach? Yes... to the right because your rotor disc is trying to flap back along the axis of your travel and has produced a LEFT roll relative to the fuselage.
I agree that a slab sided fuselage will tend to increase drag when presented to the airflow but not enough to roll the aircraft into a turn (maybe 1 or 2 degrees AoB). Otherwise, if you tried to hover in a 30 kt crosswind from the right in your slab sided helo, you would run out of LEFT cyclic trying to oppose the fuselage roll to the right - this clearly doesn't happen.
Some helicopters with more fuselage area forward of the rotor mast than behind it have directional stability issues (Puma for example) but this is going away from the original point of this thread.

Of coures it's easier to fly an ILS in a plankwing, that's why helicopter pilots are so much better (well one of a multitude of reasons really!!!)

[Shawn Coyle]

This thread is getting off the topic of torque increase due to roll rate, but to continue the discussion....
You need to consider the position of the vertical CG and the side area of the fuselage above and below the CG. Put any light helicopter on floats (the permanent kind, as opposed to pop-out) and side slip and you will see a negative dihedral effect- right pedal, which generates a left sideslip will roll you to the left as the greater area below the CG overcomes anything the rotor may do. This could be a problem in a lightly loaded AH-1, but probably not when loaded with weapons as the CG is much lower.
Food for thought.

[heedm]

Crab, my point was that so many factors are involved, that assuming the roll rates to be balanced left and right is erroneous (my opinion).

Helicopters aren't symmetrical. There are some symmetries, but overall nope. When we find things about them to be unbalanced, we shouldn't be surprised.

[[email protected]]

Shawn, I appreciate that it might be possible to end up with a negative dihedral effect but the majority of helos display positive dihedral effect in sideslip which is just as well for safety's sake. BTW this thread is not about torque changes with roll rates but different roll rates in left and right turns on most helicopters.
Heedm, I agree but I would really like to know why it happens and why no-one can answer the question.

[Flare Dammit!]

Crab, your analogy about what happens when helicopters hover in brisk winds is off-base. We're talking about cruise flight here.

You wrote:
Shawn, I appreciate that it might be possible to end up with a negative dihedral effect but the majority of helos display positive dihedral effect in sideslip which is just as well for safety's sake.

Crab, you won't even take the word of a guy who works for the National Test Pilot School? Isn't that being just a teensy bit closed-minded?

Once established in a stable sideslip, yes, the aircraft will behave in the manner you describe. It's getting to that point that's the fun part. If you're cruising along in just about any helo without artificial stabilization (with the possible exception of the 222UT or B or whatever that peculiar model was), squeezing in some pedal will result in a roll in the opposite direction. Helicopters do not exhibit "positive dihedral effect" Might I point out - even though it should be obvious - THEY HAVE NO DIHEDRAL! And in any event, big changes take too long to manifest themselves. "Ruddering" a helicopter around to pick up a "wing" or something is an exercise in futility and will only upset things more because of the undesireable yaw/pitch coupling that many helicopters exhibit.

[[email protected]]

FD, Shaun was talking about a light helicopter with floats on in his example of negative dihedral - a situation where the amount of drag caused by the fuselage is much more than normal and the CofG is unusually high. I agreed with him completely in this situation (I've even bought his book!) I think he would agree that most helicopters do not display this effect and instead display positive dihedral EFFECT (ie the same as a fixed wing would despite the fact helicopters don't have wings).

It is the positive dihedral EFFECT that makes the helicopter roll in the opposite direction to the sideslip (therefore in the same direction as the yaw).

As for the boll*cks you wrote about ruddering around to pick up a wing - you were the one who said this was dihedral effect, not me!

Ask Ray Prouty if helicopters exhibit positive dihedral effect and I think you will get an affirmative answer (I've got his books too!!!)

PS My analogy using a crosswind hover was accurate because it highlighted the error in your argument that a sideslip produced a roll in the same direction. A crosswind hover is only an extreme sideslip.

[Flare Dammit!]

Crab wrote:
It is the positive dihedral EFFECT that makes the helicopter roll in the opposite direction to the sideslip (therefore in the same direction as the yaw).

As for the boll*cks you wrote about ruddering around to pick up a wing - you were the one who said this was dihedral effect, not me!

Man! You Robbie pilots sure can get testy! Look, I don't care what any engineer says about what heliochoppers are supposed to do. All I can say is what I've observed based on my many, many, many years of experience and my tens of thousand of hours at the controls. And when blokes like you attain the same level of acheivement and knowledge as the great Flare Dammit!, you too will understand so that I won't have to keep repeating it ad nauseum. Do you little people think that I enjoy hearing myself talk?

You can use the what appears to be "dihedral effect" to your advantage, but it must be understood that the opposite control (anti-torque) input must be made.

Now listen and listen closely.
1) Take a helicopter...a 206 say (your choice whether it's an L or a B). It does not matter whether it's on "standard" floats or pop-outs or low-skids.
2) Set up stabilized cruise flight at MCP.
3) Put enough friction on the cyclic so that it will not move.
4) Squeeze in a little LEFT pedal.
5) Notice that the ****** banks decidedly to the RIGHT!
6) Repeat.

Works every time.

Keep feeding the pedal in and the nose will drop. Do the same thing to the right and you'll notice that the nose drops more quickly.

You can quote all the books you want from now until kingdom come. But I challenge you to go up in an actual aircraft...you know, like an actual, thinking, rational pilot...and set aside your preconceived notions about how someone *says* that the ship will behave...and go see for yourself. Then, and only then, come back to me with your observations. Because I grow tired of this thread and your unbelieveable, galactic ignorance.

It was Nick Lappos who long ago postulated that helicopter rotors didn't actually employ "gyroscopic precession" because the blades (analogous to the vanes of a gyroscope) were not solidly attached to the mast. Further, he said that a rotor blade's reaction to a pitch input was not ninety degrees, but something more or less, depending on a variety of factors. I believe that he mentioned that the Sikorsky S-76 had a 77 degree "precession" or something like that.

When I mentioned this to other, supposedly experienced and knowlegeable helicopter pilots, they acted like I was loony. Why? Because they learned from their original texts and instructors that a helicopter rotor possesses "gyroscopic precession" and that blades react ninety-degrees later than where the force is applied. They learned it that way, they read it that way, and that's the way it bloody is. So there.

Not everything that we read in books is true.

[[email protected]]

FD, I can only assume you are a 'wind-up' merchant as you now doubt the words and wisdom of Nick Lappos and flatly refuse to hear any application of theory that might oppose your own ravings on this topic.
As for experience - well your profile doesn't give any information whatsoever - it is even possible you are a wannabe with very limited experience indeed.
As for me, well as a military A2QHI with 6000 hours in helicopters and 2000 hours instruction - I guess I must be Mr Thickie here as I have only taught effects of controls a few thousand times and probably haven't got enough experience to match your awesome abilities.

PS the nose drops because you are moving the horizontal stabiliser into different ares of downwash (the downwash is stronger behind the retreating side of the disc than it is behind the advancing side).
PPS I have actually flown a 206 and it does not do what you claim.
PPPS. If you believe so strongly in precession as the cause of phase lag (yes that's the phrase you were looking for) then a certain Mr Luckerman might want to add you to his Christmas card list.

I started this thread hoping for an answer to a question but it seems there isn't one.

[Nick Lappos]

FD is dead wrong about the yaw effect, at least in every helicopter I have flown. If the aircraft responded the way he describes, it would be illegal, since the basic Federal Aviation Regulations demand positive dihedral.

In short, at cruise speed, left pedal makes left bank, and requires right cyclic to trim out that bank. The opposite is also true, right pedal makes right bank.

This effect was invented by the Wright brothers, and is true for all aircraft I have tested. On helicopters it is a natural outcome of the coning that the disk has, since the sideslip produces an increase in the angle of attack on the side of the disk that "leads", and a decrease on the side that "trails" when sideslip is applied.

A high tail rotor tends to wash out this effect, since it produces a roll in the opposite direction of the yaw, but most helicopters have relatively low tail rotors.

[vorticey]

you wrote

Sorry, matey, but the roll rates actually don't have anything to do with cyclic position.

BUT, the first thred from crab was entirely related to the cyclic position and roll rate!

if the cyclic is allready off centre duing flight then more cyclic is neaded to make a roll in the same direction. then centering the cyclic would stop the roll.
centering the cyclic duing forward flight would cause a roll to the oposite side. to stop the roll, an awfull lot of cyclic is going to be needed.

CRAB

in flight or hover, whats the difference with tailrotor roll?, its always going to be there when power is applied. sure less peddal is required but the anti torque is still in the same place.

[[email protected]]

Vorticey, absolutely right, hence when you have wings level and ball in the middle you are actually sliding a right a bit - this is inherent sideslip.
The only way to fly straight ie fuselage exactly pointing the way you are going is with a little left bank and the ball slightly out. Or you could have a piece of string (wool in the case of the Gazelle) mounted centrally on the outside of the cockpit which will indicate the true direction of the airflow (except in a climb where the whirl of the rotating downwash can alter it's accuracy). Or you could tilt the rotor mast in the opposite direction to TR thrust.
Back to the point - I hope we have sufficiently thrashed out that sideslip in one direction, almost always gives roll in the other direction (positive dihedral effect again) and that therefore, other than with a very high TR position, there is unlikely to be any rolling couple caused by the TR.

Nick, I guess the original question regarding roll doesn't have an answer - it just does it?

[helmet fire]

Crab,

I am still waiting to hear your thoughts on the power requirement slowing down the roll rate.

Also, if you have an aircraft available to check, does the roll rate speed difference vary with forward speed? I.E. the difference in roll rate is relatively easy to notice at 120KIAS, but how about at 20KIAS?

[Nick Lappos]

Crab,

Regarding the original question of assymetrical roll rate response to cyclic:

I had a chance to check some data, and at least on the aircraft I fly regularly, there is no significant difference between the roll rate due to 1 inch of cyclic from trim for left or right turns. This holds until you get very much toward blade stall, whence (wow, I am starting to sound British!) there is much less right roll control power than there is left.

I will get some data and post it on my web site in a day or so.

The rate damping is the measure of the amount of opposite stick you need to stop the rate once started - low damping means you have to stop the roll rate with opposite stick, high damping means it stops when the stick is returned to the trim position. Teetering rotors have very little damping, and I seem to recall that right rolls take more left stick on recovery than left rolls take right stick. I touched the left stops in a Cobra in a right rolling maneuver, and that cured me of playing around (for about a week or so, anyway).

Articulated rotors have higher damping by far, and need very little opposite stick, and "rigid" rotors have very high damping, and stop crisply when the stick is recentered.

Nick

[[email protected]]

Nick, Thanks for persevering with this question. I think it is definitely the differences in rate damping which I have found most noticeable in manoeuvres. Strangely enough the Lynx was ths worst offender and it has a very high effective hinge offset - I wonder if the amount of left cyclic required to stop a roll right is partly due to the rate of roll you can achieve thanks to it's huge control power.
Helmet fire, I don't know whether rolling towards the low power side (torque spikes in roll) makes any difference - the rate of roll seems to be purely decided by control power and damping. My original question had to do with manoeuvres like downwind quickstops and wingovers where the typical speed during the middle of the manoeuvre would be 40 - 60 kts. I could try experimenting next time I'm on shift but the rearcrew moan like bugg**y when you try to roll their yellow SAR bus upside down!!!