dc ! this thread is about coning angle

it's not about how a ball works !! you could look it up on google, or if it saves you the time it measures the direction element of the acceleration vector in the plane defined by the arc of the little glass tube, thereby indicating what proportion of the g experienced is lateral

re the velocity of the Apache this thead isn't about that either !! and i have answered it 4 times

and given that you don't understand what a balance ball does, can't work out how to measure distance in units of aircraft leangth, can't see that the measurment requiring 10 repetitions to be averaged is the timing (since 2seconds is a very sensitive number in the denominator), have generally been disingenous in not recognising the central point about the ratio of 'lift' to Cf. Your arguement against it is to do with lift not being proportional to Nr^2, whereas to a first degree approximation it is universally considered to be sufficiently relevent (in all published and respected works). It is not surprising that you don't understand, infact I think you maybe do (or should) understand but you just perversly enjoy leading the 'easily led' and rather simple Crab down the garden path. You dismiss my assumptions yet make your own (uniform downwash assumption). How about this (agree if you have any honour) if you take the premis that Lift is proportional to Nr^2 then you agree with what I have said about the limiting coning angle observation ? and better than that the Ultimate CA wrt a/c speed would resemble the graph of Ct/sigma that NL posted it's a novel way to look at coning angle, it brings something constructive to the party. and all you can do is try unsuccessfully to pick little holes in irrelevant aspects in a way that calls into question your undersatnding of those things. play straight and acknowledge the insight into the crude concept of Ultimate Coning Angle.

Furthermore YOU have refused to give YOUR idea of what the dependancy of Lift on Nr is. you didn't answer THAT. and you want to press me on all sorts of stupid (and fairly obvious points which i am mostly patiently responding to). YOU don't answer my points and i have answered most of yours.
CAN YOU? I don't think so. Nr^2 is a pretty reasonable approximation for these purposes.
How about you give the coefficients of the polynomial expansion on Nr? K(a0Nr + a1Nr^2 +a2Nr^3 +a3Nr^4 ...) (or minus power terms if you wish...) etc

I don't beleive that you can't work out how to measure the distance flown from the video LOOP. Please confirm that you can see that loop?

You can't be a helicopter designer, and if you are then I hope the "people on your team" can help you with some of these ideas. Are you a helicopter designer?

Ah, now we are in the full RANTING phase of AnFIs argument strategy - this is where no-one is clever enough to understand his ground-breaking concepts, each person's arguments and logic are systematically rubbished and refuted - without any actual facts or proof.

The only thing he has left is Ad Hominem attacks on the people who dare to contradict or question him and a bit more 'mathematical' obfuscation.

Ever heard the phrase 'When you are in a hole and want to get out - stop digging'?

You don't like those with more relevant experience on a topic than you, you don't like those with a proven track record on your favourite subjects who don't agree with you and you definitely don't like people who are cleverer than you....

At least the AnFI fan club gatherings must be easy to organise................

AnFI - I'm sure a little thread drift would be tolerated. The discussion included a g meter for the Apache, I was interested to find that this was fed to a cockpit instrument. If you recall you were the one who introduced sideslip "wot do they use lateral g for ? sideslip? dCL/da are you actually a helicopter designer?" empahsis was yours.

I have posted the BET equation for lift, that is sufficient for most to grasp the concept of inflow/induced flow and its impact on lift. I don't intend to get in to a deeper discussion on tip or wake models.

No, I can't measure distance from the video as there is nothing clear to refer the distances to.

It can't be done by analysing the frame, as there is no clear indication of the speed at which the frame is moving. If the frame was stationary then the aircraft itself could act as its own reference scale. With the aircraft and the frame moving it can't be derived as there are two unknowns. It can't be done by comparison to the background as the background is clearly a substantial distance away. This introduces, in essence, parallax. Without knowning the difference in distances this cannot be taken out. Further information is required, or gross assumptions made. The only thing that can be seen in plane with the aircraft is its downwash effect on the water. When this is evident there is much too short a clip to analyse without introducing large deviations in the measurement. This is why I asked you what you used as your points of reference.

my post full of logical arguement facts and reasoning, answering the questions to me, refuting the validity of incorrect points made against me, explanation etc

your post pure insult off topic no resoned content no helping to get to the bottom of the facts deferential to 'respected members'


"you definitely don't like people who are cleverer than you...." that is not a problem I have in your case
I loved NL inputs, clear cool, insightful, enrgy in feet (ft.lbs/ft)
he's just sadly missin'
the point that he's dissin'

dc/da i respect that he has some degree of technical understanding, it is partially your fault in reducing the quality of the debate that he's gone off down a side track about measuring speed, or how the ball works in an aircraft. He is not and has not answered any of my technical questions to him.
megan i respect that he has some technical curiosity and generally a genuine interest in getting to the bottom of the issue, iam am sure he'd like to focus on the point


your only material response on this matter has been a long post about how you should start a pull out high enough to make it.

if you don't have anything to say why don't you try not saying it ?

Do you think it's a fair assumption that the Ultimate Thrust that a rotor disk is capable of is proportional to the Square of the Nr?
(if you do, then you are in good company and you agree with me)

you consistently degrade the quality of other people's discussions, are you literally pointless ?

AnFI - two of us have asked you how you 'measured' the apache speed but you haven't answered - is this refusal an indicator of the weakness of all your arguments ie they are fabrications and bluster?

The 'ball' was introduced by you when dCl mentioned using an accelerometer for turn co-ordination - and you haven't answered his question except to rant about googling balls. Where is the accelerometer in the balance ball tube? When you were corrected you simply called him a - very logical and concise......

You keep emphasising that Nick doesn't get the point that you are making - what does that tell you about the point - is it you in fact who are pointless because you are making stuff up and won't acknowledge a professional's analysis?

Do please try and find someone who agrees with your assertion that the It is such a simplistic statement that it is very unlikely to have any scientific basis because so many other factors are involved - some of which dCL has tried to point out to you.

You have claimed to be a flying instructor on other threads but now you are straying into the realms of being an aircraft designer - a touch of the Walter Mitty's perhaps....

"Side track" ... loving the pun. Also interesting the subliminal way you drop italic emphasis in.
The point of the diversion was lateral g. Rightly or wrongly people use the term sideslip both in terms of turn coordination and in terms of a constant sideways velocity. The first is indicated by an accelerometer the other is much harder to derive.

The distance measurement is still a question of interest as it is pertinent to your "g" calculation.

AnFi is just googling parallax........:E

Still waiting AnFi - it can't be difficult to explain since you said it was easy...........

Crab the answer was given wrt the 'simple accelerometer that is the 'balance ball' "you could look it up on google, or if it saves you the time it measures the direction element of the acceleration vector in the plane defined by the arc of the little glass tube, thereby indicating what proportion of the g experienced is lateral"

The distance can be measured by noting the position of the reference points (which I have answered many times now) wrt the back ground. So note the position of the nose wrt the background, then when the tail reaches that point wrt the background note the new position of the nose and repeat etc . There is no parallax involved because the position of the camera does not change, there is no issue with the pan, the straight lines from the camera to the backgraound are valid (because the camera is in the same position.

Do please try and find someone who agrees with your assertion that theQuote:Ultimate Thrust that a rotor disk is capable of is proportional to the Square of the Nr?I think you'll find Nick agrees, as do most academics. Anyway it is true that it is not exactly correct, but it is correct enough, and in a practical sense would be even more practically correct when the degree of induced flow is less important at speed (although that does bring other minor complications) it is still a valid first order phenomenon that should be interesting to folk interested in PoF.

The extent to which it is not exactly true should be quantified by dc/da so that we can see how relevant it is , I have asked him to do that several times.

It's like claiming that v=d/t is not true because of relativity, but it is true enough for our purposes
(hence the quip about throwing the baby out with the bath water, it is a shame that Nick has not addressed the point, probably because I did not convey it with sufficient clarity ('my bad')

Crab "- very logical and concise......" sarcasm again

So if you fly cross-controlled - ie put in left pedal and right cyclic, you are travelling in a straight line but the ball is out to one side - that is steady state not acceleration.

An accelerometer that feeds into an AFCS to produce coordinated turns senses the lateral acceleration that occurs when you roll into a turn without adding pedal (skid or slip) it then feeds a signal into the yaw channel to reduce that skid (acceleration) thus giving a balanced turn. A balance ball won't do that for you which is why they wire in accelerometers and not balance balls.

With your reference points you have two rates of movement to contend with - one of the camera panning with respect to the scenery and one of the aircraft moving with respect to the scenery. Therefore two rates of angular change which are different with respect to the observer (the camera).

What magic maths did you use to eliminate the parallax error?????

If I could ask AnFI and Crab to go back a few posts, and edit out (each of you) the bits where you both play the man and not the ball for the last few pages, there would be less FOD in the thread and the points you are each making would be clearer. For example, Crab's last post is mostly content ... but in the past page this back and forth attracted more turbulent flow over the discussion's airfoil than laminar flow.


AnFI: my question on speed calculation, if your use of measurement is valid, will be modified. If we presume the camera to not be moving (which I don't, since I saw the whole video and the camera moved with the aircraft) you are measuring ground speed with the nose to tail technique.


From the earlier video of the Apache accident, my estimate of the breeze from what I saw is that the air (based on the motion of the water) was not moving much, but you might want to account for maybe 5-7 knots. (I'd not guess any higher). That would make for a delta between entry and exit airspeed for the helicopter between 10 and 14 knots if he started into the wind and finished down wind or vice versa. If, on the other hand, there was a gentle cross wind more or less perpendicular to the flight path, that should wash out.


To restate my earlier question regarding your 90 kts estimate:

Is that based on 90kts (in a X axis) with an unknown vertical speed (down) in the Y axis, or, based on your measurement method, is the 90 knots estimate more or less "along the path of flight" and thus the hypotenuse of a triangle with X and Y being horizontal and vertical components?


The triangle we could be constructed by superimposing a grid on the frame and tracing the flight path/hypotenuse and the constructing a right triangle legs from that. I realize that this bit of video does not give us gnat's arse precision, but I am interested as much in method as anything else. The last five seconds of video are not "level flight" but a nose down descent.

The other problem that arises to resolve is the dynamic nature of the event.

The Apache attempts to decelerate (and let's say he started somewhere around 90 knots as a baseline). The pitch isn't oriented in a purely Y or X axis direction: it's a bit of both.

His "nose up" at the end takes him from nose down to a bit above level, if not level, but he was surely in transition, not steady state, in those last two seconds.


Edited upon a second review of the video.

Imagine an object at distance x from an observer subtends an arc of 10 mrad. That object moves 5 times its length, which creates an arc of 50 mrad. That can be said with certainty.
If an identical object were at distance 10x then it would subtend 1 mrad and the movement 5 mrad. Again the ratio holds true. However, in relation to the observer one appears to have travelled ten times further.
Imagine the observer turns through 1 mrad, that movement encompasses a tenth of the object at x but all of the object at 10x. The observer's frame of reference appears to have travelled the length of the object at distance, but only a tenth of it close to.
Without knowing distances/speeds there are too many unknowns. You don't know how much of the movement is due to the Apache and how much to the panning as a "length" at the background does not equal a "length" at the Apache.

As for the lift on a rotor blade being directly proportional to RRPM squared. I've previously pointed out that if you deliberately choose to ignore the change of CL along the blade due to alpha changes then that sums it up.

To throw another factor in - at the apex of the wingover his speed will be at a minimum and as the nose drops on the initial part of the recovery, he will accelerate. At some point as he starts to flare, the speed will start to reduce (or at least stop increasing) once the nose is level with the horizon, the speed will reduce (but not at such a rapid rate as when he hits the water).

Lots of variables in the 'easy' assessment of impact speed......

What you can say for sure is that the speed isn't a constant 90 kts from apex to impact.

lone
FOD - agreed
"the camera moved with the aircraft" no the camera did not move it panned ie just changed angle when it pans the line from the camera to a place in the woods in the background stays the same in space although a different place in the frame so when the tail has the same background that the nose used to occupy it means the aircraft has moved one aircraft length. I really don't think it's that hard to understand that, is it?
Wind yup there is some room for difference there but again it's not a result that's obvious to most pilots (i really dont want to open a new contention, but it is a frequent error, the effect of wind sheer means that pulling out downwind is energy advantagous, that wont be agreed with and is counerintuitive and true, let's do that in another thread if neccessary)
"is the 90 knots estimate more or less "along the path of flight" and thus the hypotenuse of a triangle with X and Y" yes it's along the path of flight so NOT the hypotenuse but the length of the arc
"but he was surely in transition, not steady state," correct so the AVERAGE speed along the arc in the last 2 seconds was 90kts and the AVERAGE pitch change was 21deg/s (which is actually quite fast in practice, try it, i did and it is quite 'meaty' which is one reason why NL's contention that he had no apreciable pitch rate is incorrect (regardless of how much of a super hero we all think he is, he is just WRONG about that)

dcl/da
I am sorry but your analysis of the speed measuring methodology is seriously flawed. calling into question your ability to understand anything. I can try and help but short of drawing diagrams etc the best i can do is to say imagine a stationary helicopter at some distance between the camera and the background and then the camera pans the tail will still have the same background and so will the nose if on the other hand one found that the tail was occupying the backgraounfd that the nose used to occupy one could infer that the helicopter had moved one helicopter length. the rest is obvious if that is difficult to understand then I am not convinced that you have given serious consideration to the point i have been patiently trying to make, it is a serious point and I urge you to reconsider its merits

As for your contention that lift is NOT proportional to Nr squared i have on many occasions now accepted that it is not exactly true (but it is good enough) I have asked you to quantify HOW wrong it is. To what extent is lift NOT proportional to Nr squared you have evaded answering that at least 4 times now. ANSWER IT if you think you have a point IF YOU CAN ( if you can't I could do it for you are you going to MAKE me do that too, or can YOU do it? ooops not just cut and paste eh !?)

Crab it is a pleasure to have you address the points rather than insulting me, thank you
yes you are quite right the speed is not constant but an average so we can say that at some stage it is MORE than that over the period
i am not sure that the speed reduces (although it might) it is hard to say (it could be done with some difficulty) but the speed may be fed with height, (on reflection you are probably right that the speed at the bottom is not a maximum, ie therefore reduced nonetheless too subtle for me and the crude approximations are 'good enough' too much 'fine point' is dc/da's affliction , he doesn't even realise that there is a baby in this bathwater. please try and think about it again freshly (please try), I think you'll see what I am saying

can ANYONE see the video I posted of the last 2 seconds ?????????

and anyway this thread is NOT ABOUT the GREEK Apache !!!

good night



NL time to 'come out' and support me while you can still take the high ground of independance and rational fairness i dont care who you are, just the logic of what you say has to make sense, i am totally irreverant (thats IRREVERANT, (i'll set em up you kick them in)) only your logic counts with me and so far i cant see that you even understand the point that you might be disagreeing with,.

And a dozen posts have followed this

For one who has steadfastly ignored requests for providing some background of his (her?) experience, the sheer gall of demanding and criticising another Rotorhead for choosing to remain anonymous is another facet of AnFIs attitude whereby only his POV can be correct and any rebuttal will be met with more and more pigswill.

A wise man once said "Battle ye not with monsters, lest ye become a monster"
I don't know why you guys do. Even without any/much understanding of helicopter physics, i can see this guy contradicts himself, blusters and switches topic. He's just a troll, ignore him.
Whilst discussion is good, and indeed has brought up all kinds of interesting matters, misinformation written in an authoritative way is dangerous, someone might believe it.
My 2c

Lonewolf50 - I know I have been guilty of playing the man but only one man whereas AnFi sees fit to play everyone who doesn't agree with him.

My transgressions are due to the frustration of having dealt with him many times before and the fact that he follows pretty much the same MO each time - not adding any value and just confusing what could be quite interesting discussion topics because he thinks he is right about everything.

You can see he hasn't repsonded about balance balll vs accelerometer and he hasn't responded to dCL regarding the angular change wrt the observer - that is because he has made his point (usually with insults) and won't see that he might possibly be wrong - (it's an ego thing).

Similarly, he keeps refuting dCL's accuracy of maths - saying it is irrelevant in the same breath as claiming his own maths are beyond reproach, with any terms he hasn't included being 'good enough' to 'prove' his point.

I know I should just leave him to fester and walk away but there are some very good commentators on this forum whose opinions are highly valued - to let AnFI think he is among that number would be doing them a disservice.

AnFI - place yourself in a position where you can see an object in the near or middle distance clearly with an absolutely perfectly aligned reference point in the far distance.

Close one eye and ensure your objects are lined up perfectly. Now rotate your head - simulating the effect of panning a camera - and you will see a parallax error appear.

The camera, it's lens and its focal plane will move at a distance from the pivot (ie the human holding it) and not rotate simply around the focal plane. There is your parallax error (change in position of the observer) and there is the weakness in your speed assessment.

Your video has no such perfect position references and you don't know the focal length of the camera lens (another variable causing distortion) or whether the camera was held at arms length or close to the camera operators eye - therefore you cannot calculate the amount of parallax and your speed assessment is pure guesswork.

Simple enough really;)

Btw, the oaf in the playground worked that out sitting in a café with a large mocha:)

I was reading that all AH-64D/E's have a Maintenance Data Recorder, so, assuming someone was smart enough to take advantage of that, plus the fact that the machine has digital data for those parameters typically needed for recreating a flight profile, the hard data that answers the conjecture in this thread are probably well known by the investigators.

There is an IQ level below which it is difficult to engage seriously.

People ask me for clarification on a point, when I give it i'm going off on a tagent, when i don't i am criticised for that too.

The point is the point and it isn't parallax its about coning angles.

ONLY dc/da has said it is not correct and I've asked him how much incorrect, a pertinent and important question , on topic, that he has evaded
e)
if he says I am wrong because the induced flow increases with higher induced flow (which is making a set of assumptions that are not neccessarily the case)
then I think it is reasonable for me to ask him 'how wrong?' ( i have said many times the inaccuracy that he points out is true but its throwing the baby out with the bath water, ie it's tru but barely relevant) if he thinks it is relevant he should say so

ie HOW far does the (first order) relationship deviate when you take into account some secondary effects based on a (flawed) model with (flawed) assumptions
HOW WRONG

It like the red herring that crab is pressing, yes he is right there is a parallax error that i ignored, the reason i ignored it is that the measurements i made were not accurate to the extent that the paralax error would be significant. here I am wasting my time and yours coming back on a point of noise from the oaf with the mocha, if we assume that the guy has 2ft long arms and holds the camera at full extention, furthermore lets say the ratio of distance from the camera to the helicopter compared to the helicopter to the background is 1:25, furthermore lets say the camera moves through 30degrees then the distance the camera moves is about 1ft, the error created DOES exaggerate the speed because that helicopter would have travelled a further 1ft times (24/25) during that time. You can see why its a wast of time considering it. You can see why I HAVE to answer it You can see where the waste of time comes from.

SO hoss183 "and switches topic. He's just a troll, ignore him." I am not switching topic they are the topic is the balance of TRT to Cf if people coulsd stay on topic that would be great,
but 183 do you see why I have to answer these dim and off topic points? I am accussed of not answering the question. My post 183 is a waste of everybodies time in having to answer PATIENTLY everyones side issues.


Heli "...steadfastly ignored requests for providing some background of his (her?) experience, the sheer gall of demanding and criticising another Rotorhead for choosing to remain anonymous "
can you see the hyopcritical, contradictory and illogical nature of that absurb statement? I'll spell it out you appear to agree that the desire for a member to stay anonymous is reasonable, yet it becomes a criticism againt me that I chose that. furthermore I am told that I am flying in the face of established expertise of a test pilot and two aircraft designers, well NL is a exTP and megan easily has enough talent to work for Airbus I guess, so I am faced with the implication made to me that dc/da is a designer, I find that astonishing, since his aero BET maths is straight out of an undergraduate degree module on helicopters, and all the designers I have met have allways had a pretty direct grip on the fundamentals, etc etc etc

so you can't win eh
no one will engage on the point they all refute red herrings they won't answer where the disagreement with the point is i you resond to a criticism (eg about parallax, or to what extent a ball is a type of accelerometer) then its a waste of time side track , if I dont respond to a sidetrack I'm avoiding it and repeatedly pressed. can win in a dedate with an idiot. Wasting my time.

The short summary of the relevant points are

1 my assertion
2 dc/da's refutation (which is technically correct)
3 my request to quatify that, to see if anyone agrees that it materially alters the assertion

all the time that is happening we are having to contend with the low IQ knee jerk reaction of mad folk screaming and wailling

and the occasional intevention from the very charming and civilised legend who is John Dixon ;)
a few irrelevant but beautiful technical inputs from NL, combined with some erroneous noise (20-30kts for the Greek helicopter, NOT TRUE)

this does not appear to be a place where a fellow can have a substantive conversation, without the mocha drinking oaf baying and goading etc



THE ONLY QUESTION I WOULD LIKE TO BE ANSWERED BY DC/DA (WHO IS THE ONLY PERSON WHO HAS SAID I AM WRONG)
is
HOW WRONG? Quatify it !!! (there's wrong and wrong)

Finally a breakthrough AnFI.
I used a concept from lecture 2 rotorcraft.
Then again you quoted an equation from lecture 1 aerodynamics, so it seemed appropriate.

But we make progress because you now acknowledge that BET is a fundamental concept in rotor blade design. BET gives an equation that has both RRPM squared and RRPM terms. So when you say "how wrong are you?" the answer is "completely." When you chose to "cancel rotor speed squared" you appear to have left a variable based on rotor speed. So your theory is not "independent of rotor speed" as you so clearly stated.

When it is that simple why go further? We could of course introduce forward flight and resolve the different demands on advancing and retreating side. We could introduce tip effects, perhaps play with some vortex wake models. I could task some BEM work ... but then why bother? Something academically accepted as fundamental, admitted by yourself, contradicts your assertion.

Remember that you brought in your ability to extract the Apache's speed from the video in sufficient accuracy to support a calculation of g to one decimal place in order to support your theory.

Your explanation as to how you can use the background as a reference when it is moving at an unknown speed through the frame and is at an unknown distance will not pass the red face with anyone who has tried to optically track targets.

Assuming the MDR doesn't "disappear" everything that needs to be known will be, including the cockpit conversation.

Or is "damaged" beyond recovering data ...

So AnFi - you are 3 nil down now - ball vs accelerometer - failed, speed calculation not including parallax error - failed, maths in rotor calculations - failed.

Anything else to add? Bearing in mind you have said your 'final' piece several times now.........

Oh, I forgot - the ball and parallax were just diverting sidelines that you were forced to argue - except that you introduced them to try and show how clever you were.......

As for MDR - that might not include cockpit information, it depends on whether it is part of CVFDR set up or a stand alone maintenance data recorder.

Crab, my understanding is that the MDR is an ED55 / 56 device, if so then it should have 4 audio channels ... of course depends if they were wired up.

This whole thread is starting to resemble something from a Monty Python sketch

Monty Python: The Argument Sketch

I'm astounded that AnFI hasn't used the 'S' word yet :ugh:

Still, his red-faced and screaming Herr Hilter impression :\ is jolly amusing to a mere know-nothing Ukrainian tractor driver - but at least I can spell - even if I don't understand all this advanced mathematics about conning angles :confused:

Crab "So AnFi - you are 3 nil down now - ball vs accelerometer - failed, speed calculation not including parallax error - failed, maths in rotor calculations - failed."

NO !

ball vs accelerometer ... all i said was that the ball is a crude accelerometer in as far as it shows the direction component of the the g experienced in that plane - TRUE

Speed calculation parallax NO the paralax error is negligable being 50% ish of the length of the arm if at full extension through an assumed 30deg ie about 1ft in 250ft NOT RELEVANT (even if taken to the extreme)

I have allways been saying that there is indeeed a very small (baby out with the bathwater) difference , I have repeatedly asked dc/da to quantify that term which HE HAS REFUSED TO DO. Most experts agree with me that the Nr^2 model is universally accepted to a reasonable degree of accuracy.
How WRONG IS IT ? Answer NOT SIGNIFICANTLY. it is further LESS significant if dealt with at greater speeds and induced flow representing a pullout scenario....
although it is true that that does bring in the additional considerations (that I have already alluded to) of different speeds across the cycle.... and I have suggested that that is well mapped by the Ct/Sigma curve introduced by NL

SO NO !!! it's nil 3 crab


Fohn spelling not my strong point ask Crab (even though I also ironically had to teach him some basic grammer wrt An FI, he was TOTALLY WRONG about that too)

the 'S' word !!! ??? I HAVE used it repeatedly SSSSSSSquared !!!!


HOW WRONG IS IT ? Not significantly! if you want to refute that then QUANTIFY IT !!!!! you have not, probably cannot. You are throwing the baby out with the bathwater and you know it, or PROVE OTHERWISE (you can't) what is the coefficient of the Nr^-1 term normalised to TRT = 1 ?????

You can't or won't because it shows that your clever little nit picking point is essentially irrelevant, and you know it.

NL and most texts in a crude model accept that Nr^2 is valid, it is only in as far as those assumptions are used that I claim that my statement is valid too.nyou can't dispute that and if you do you have no honour

this is not a place where you can have a serious debate with sincere people attempting to explore the validity of a hypothesis, NL has not uderstood the point and has checked out i think I should follow his lead

...and the judge's decision is......reserved.

It is just pure coincidence that the coning angle goes up as the rotor RPM go down. There is no relationship, nothing to see here...everybody please move on and take your angry little arguments with you.

Thank you.

Here is a link to the MDR. Answers some posted questions:

http://ktferrera.com/images/STSI/FTP/MDR.pdf

Looks like it should have survived the crash.

Not really - you constantly claim the moral and intellectual high ground yet when holes in your arguments are exposed, you dismiss them as irrelevant as an excuse for not realising they were there in the first place.

The complete irrelevance is this ultimate coning angle - do the blades cone up as Nr decreases? Yes we all know that.

Is there an ultimate angle beyond which they won't go because of some special mathematical relationship that only you understand? I don't think so.

You are forgetting the practical when dealing with the theoretical - different rotor designs will have different physical limits to their coning - the blades themselves in a teetering head, the physical limits of the hinges in an articulated head, and the limits of deformation in the elastomeric hinges in a semi-rigid head (titanium star bending on a Lynx).

So why postulate that there is an ultimate coning angle? Do designers use it? No. Could or would pilots use it? No. Do engineers consider it? No.

So therefore, on the subject of irrelevance - where does your rather muddled argument and proposed theory stand????

And, just as a reminder - these were the statements from the beginning of the thread Accurate?????Relevant????

AnFI - I don't need to "measure how much". I've posted something that readers of this thread can go check for themselves, think about and come to their own conclusions if they want to.

Ascend Charlie - I agree it is evident to anyone with experience. However to the casual observer, or someone who is ab initio, the simplicity of AnFI's original assertion, accompanied by shiny maths and glittery technical words, may seem quite compelling. This is my concern.


The concept is, from my interpretation of the original posts, as follows


Lift is proportional to rho and v squared
Inertial forcings is proprtional to mass, radius and v squared

given a constant density, mass and radius, and substituting in rotor speed for v then through the mathematics of the equation for coning angle, it is possible to "approximately" cancel out rotor speed leaving a constant relationship between lift and coning angle.

The concept is explored within the context of limiting thrust from the disc, i.e. As rotor speed slows, it is necessary to apply more pitch to the blade to derive the same lift, so you hit CLmax "earlier", beyond that the blade stalls and can no longer sustain the lift required, but the inertial forces are lower due to the reduction in rotor speed. Both the aerodynamic and the inertial forces are proportional to rotor speed squared, and so, according to AnFI's proposition there is approximately an "ultimate coning angle" fixed irrespective of rotor speed.


This concept is used in the original original post to try and explain why by looking at the coning angle it can be determined when a pilot ran out of lift capability during a manouevre and it isn't necessary to concern yourself with rotor speed. But if we turn it on its head things are more worrying

If the CLmax is reached approximately at an "ultimate coning angle" irrespective of rotor speed then the disc is essentially self-limiting. The inertia will balance out the aerodynamics, any attempt to put more pitch on when at that "ultimate coning angle" will result in loss of lift as CLmax is exceeded. What is true for the disc must be true also for the blade, therefore an "ultimate coning angle" must also represent an ultimate self-limiting flap angle ... all independent of rotor speed.

The proposition ultimately leads to a concept that any rotor is self-limiting in flap allowing any amount of blade pitch to be applied at whatever Nr% and the physics just takes care of it as CLmax is always reached at approximately the same angle, close enough that it doesn't matter.

I'm not going to recommend any pilots give it a go on rotor run down that's for sure.

However - the pig is getting tired:E
but you don't know any of the distances involved - the helicopter is at least many hundreds of feet from the camera and your super accurate reference points (somewhere in the woods) are thousands of feet away.

Given how 'exact' you claimed your speed measurements were and the fact that you ignored (because you hadn't even realised it existed) the parallax - how on earth is anyone expected to trust any of your other 'approximate' assertions and convenient assumptions.

I admire the many reasonable attempts to arrive at a sensible conclusion through logic, science and debate. However if logic and common sense always prevailed we wouldn't need nearly as many warning labels as seem to exist, one of which springs to mind - don't feed the animals..

Ah, but did it survive saltwater immersion? Hopefully, yes. Thanks for that tidbit, not sure how "public" the Greek armed forces have to be in their accident reports.

Yes dc/da !!!

that is very close to exactly what I am saying, the points of difference are not worth getting into at this stage, you are the first person (other than perhaps AC) who seems to be getting it. If we can keep this constructive then I think we could make a difference.

I still think to have the difference would be interesting
If you have a think about it it would be a curve (i suspect fairly subtle, practically irrelevant) of how UCA changes with Nr, to go with the function that is dUCA/rho (straight line?)
I think it would be fair for YOU to elucidate the difference to UCA that the departure from Nr^2 would give. can you quantify it ?

After all I accepted your challenge to derive some maths and did so within the assumptions that I made, (including addressing points you LATER made wrt twist etc) Anyway don't bother if you don't feel like it, I might do it if I get the chance.



[Crab ONLY - do we really have to waste our time arguing about an irrelevant point that you are disingeuously abusing to try and demean me?
Especially when you are not even right. [i]I was assuming that the camera was stationary as far as is relevant whilst panning. If we allow for your (ridiculous) supposition that it moves laterally as it pans, and we take the MOST EXTREME example of moving the camera whilst panning, we say the holder of the camera has 3 ft arms, we assume the ratio of distance to the helicopter to distance from helicopter to background is about 1:25 seems reasonable we find that it makes no difference within the tolerance of the measurments 1 part per 250 is not relevant {{{EDIT INSERT, that is 1 in 250 of the measured path length, NOT the distance of the helicopter or background which is completely unimportant}}} and I most definately don't claim such an irrelevant degree of accuracy.
and in any case the measurments I never claimed were particularly accurate. The only accurancy I was going for at that stage were to see if the EXPERT OPINION was anywhere near correct , which it WAS NOT (20-30kts, ridiculous !!! ). please don't come back to me on this parallex w.o.t. please try and understand what dc/da has said, he's really close, and I think you would enjoy the point if you 'got it'. try it you'll like it ]

Crab "So why postulate that there is an ultimate coning angle? Do designers use it? No. Could or would pilots use it? No. Do engineers consider it? No."
If they don't they should, and i think most do, if there are any that don't don't even go there of course there aren't ANY designers that don't get that idea and its importance

the danger is that helicopters will be designed according to criteria that regulators understand/mandate and they definately don't understand THAT.
Nick can you speak with SKSY designers, what Coning angle to they aim to accommodate?

AnFi - even I, who greatly enjoys pricking your pomposity whenever it rears its ugly head, have tired of your pointless, circular arguments.

You are not a test pilot, nor an aerodynamicist, nor an aircraft designer nor a recognised academic in aviation-related fields yet you seek to lecture, browbeat and harangue on what is a professional pilot's forum.

I do not understand why, nor do I really care, what motivates you to believe you have such an intellectual grasp of factors that even those who design, make, test and produce the things we professional pilots fly do not (according to you) but perhaps you would be better off writing your scientific treatises to Airbus, Boeing, Sikorsky et al and see how far you get.

Perhaps you should look at the impeccable conduct of someone who clearly is a professional in his field, dCL, and compare the quality and humility of his posts to your insulting and fractious ones.

If you want to be taken seriously - and it would appear your ego demands it - then try logical, concise, scientific and relevant arguments. You never know, someone might actually think you have a point.

Lonewolf, the document for the MDR says that it meets ED 55 and ED 56A. Those are the specs governing airline FDR/CVR equipment crash conditions, so the answer looks like yes,indeed.