Is that measured in degrees from the floor board, or inches of penetration into the armpit as indicated by bruising? :8 :}
When we integrate those two dependent variables, the typical result is a decrease in the angle between collective and floorboard. :E :ok:


@John D
I have been told that the cutting edge bearingless rotors (Bell Viper/Venom) required that the design and test teams had to keep an eye on flapping during test and development, but do not have personal experience in that program.

Nick took 4 small paragraphs to neatly explain a few points in a language pilots can understand.

AnFi, you took almost 20 to waffle, obfuscate and generally confuse any logic there was to the arguments here - as usual.:ugh:

Perhaps, rather than perpetually theorising AnFi, you could take an aircraft and fly specific manoeuvres, taking data points, measuring cyclic position, pitch rates (and maybe even coning angle) so that you have some empirical evidence collected in a scientific manner to support whatever it is you are trying to prove this week.

Start with a level, 45 degree AoB turn at constant speed which will give you a feel for 1.4 G, then take it 60 deg AoB which will give you 2 G - perhaps get someone to video the disc so you have some idea of coning angle.

But don't be surprised at 2 G that your aircraft doesn't have enough power to maintain level flight and constant speed but you will be able to experience how pulling hard will help increase the rotor thrust until the speed washes off below about 60 kts.

At least if I thought you had actually done steep turns in a helicopter I might think you knew what you were talking about.

Just one point - it is his inherent training that if he is going to hit the ground/water hard he needs to do it in a level attitude - that and the fact that continuing to pitch nose up would put the TR into the water first. he realised he was going to crash and tried to make it survivable.

you have said that you can use coning angle as an indicator of G load and I know an apache can pull more than 1.7 G so why is the coning angle 'as high as you can get'??

It is not unusual for an instrumented head to provide "flap" angle when developing a rotor system. I've not often seen this fed as a direct instrument to the pilot and I've never seen "coning" angle as a specific monitored value. I was interested to see if anyone on here had.

Crab, shame that Apache didn't have any flotation gear fitted.

Why feed flapping to the pilot? I must not have been clear.



I am referring to instrumentation to measure flapping to see if it was doing as they wanted/needed to get the rotor to perform to their spec/design goals. I think I presented that badly.

Why feed coning angle to the pilots?
By the time you see a problem with coning angle while you are flying, you have either already screwed the pooch, or you are too busy trying to get the bottom of the auto right that it isn't your primary nor your secondary scan. :cool:


I'll go back to reading this thread, there are a few very good posts here from folks who explain things very well, while others are all noise, fuzzall insight.

Flapping Guage for Cockpit?
 

No reason for cockpit indication that I can think of, Lonewolf.

Main rotor shaft bending is a function of flapping and that is important during test operations in various parts of the flight envelope.

For articulated rotor heads with elastomeric bearings, it is important to balance the tail incidence and CG range such that cruise conditions will result in steady state flapping numbers below that of the elastomeric bearing endurance limit. ( Endurance limit defined as that number below which the fatigue loaded part has unlimited life ). Also, because of the flapping vs main rotor shaft bending relationship, this factor is relevant to keeping the steady state ( cruise condition ) main rotor shaft bending below its endurance limit.

Of course the performance engineers care only about ( well, maybe that's being a bit rough on them, but not by much ) keeping the fuselage level at cruise, and devil take the shaft bending, shaft life and bearing life, right? So, for the UH-60 with its FBW stabilator, we spent quite a few flights adjudicating this three cornered discussion. Finally made everyone happy.

Heaven forbid, Nick got something wrong. Obviously failed to attend AnFI's school of aeronautics. Tell us where he is wrong ace, or not correct.

Thanks JohnD, thanks Lone wolf. I was certainly only asking for use in development flight test.

Flap angle is a very interesting parameter to monitor in instrumentation for a few reasons during experimental flight. I was interested to see whether any of the experienced test pilots here had ever had it fed directly to them real time. I've never seen coning angle directly used even in instrumentation, although it obviously can be derived from the other parameters.

dCl according to our guru, AnFi, it is directly proportional to G load so all you need is a G meter with an additional scale on it:E

You're right about the Apache but no-one wants to ditch in one because they are a nightmare to get out of and typically roll inverted due to the high C of G.

Crab
"according to .... AnFi, it is directly proportional to G load"

NO Crab keep up, how can you argue when you don't even understand?

A coning guage would indicate how close you are to the Ultimate Load independantly of RRPM
whereas a G meter would not. It's subtle and not very important, cept if you're designing, where you need to know what Ultimate Coning angle it's worth trying to accommodate. I doubt pilot's really want to be looking at that, although it would be more useful than a G guage.

(1st order, that ultimate coning angle would reduce for DA for example, but would be valid for different weight, g etc)

you seem to manage it most of the time :E

So you are a helicopter designer now.............

How many engines will it have............

Crab.

You are not really bringing anything useful.

Right or wrong (well above my brain), at least Anfi is trying.

p.s.

I don't agree that the cause of the Apache crash was entering the wingover too low. It is perfectly possible to exit a wingover higher than you enter, particularly in something like an Apache.
I reckon he lowered the lever slightly on the initial entry...

Thank Canute
Seriously, Crab you say "I know an apache can pull more than 1.7 G so why is the coning angle 'as high as you can get'??"

One last sincere try
Because the RRPM may be drooped (as NL postulates) and/or it is heavy. It's the coning angle that's the 'give away'.
ie regardless of whether the RRPM is drooped or not that coning angle would be the maximum reachable in those circumstances. ie you could not pull harder and get more cone.
So
If light weight at normal RRPM, max G would be (say) 2.5g and the coning angle would be (say) 9.5deg
If heavy weight and low RRPM the G would be LESS (say) 1.7g and the coning angle would still be 9.5deg

That's why cone angle is an interesting (useful) indicator (especially in video)

A helicopter coned to 2deg at 1g would be coned by 6deg at 3g
If 3g were it's max capacity, then 6deg would mark it's limit at other weights and particularly RRPMs and the g would be correspondingly different, but the max coning angle would be the same.

Anyone know what the normal coning angle of an Apache is ? (at that weight!?)

(the greek apache averages at 21deg/sec and 90kts during the pull out phase.
That's just the average, it may have been less (1.2g) in the 1st second and correspondingly more (2.2g) in the 2nd second)

It is assumed that one might acheive an unstalled 20deg of cone for example. That would be wrong, since if the blades are going slowly enough to cone that much then the blades would be going too slowly to make the lift required to cone them that much. So you can't cone a 2deg coned helicopter to 20deg unless it is capable of 10g.

Does THAT make sense? yet?

(Examples of this accodent are, Apache at altitude in Afgan, Dennis in da USofA, Italian Lake disintegration, H500 Belarus. I am sure if any of these folk could have pulled harder they would have)

No, not at all to anyone except you

Canute - what don't you understand about a wingover??? Exiting higher than you enter is a climbing turn. not a wingover!

AnFi - I note with interest that you have stopped engaging with Messrs Lappos, Dixen et al because you know your arguments are weak and not technically accurate - strangely because you are not a test pilot or even vaguely close. You claim to be a flying instructor but refuse to declare your qualifications or experience in the field - I am a flying instructor and regularly declare mine. If you want the credibility your ego clearly demands then why not come clean and let people judge you by your achievements rather than your rhetoric?

Not always - "What are the four reasons for a wingover .... Bloggs?"
"Speed to height, height to speed, positioning for further manoeuvres, and lookout ... SIR!"

crab

You are on sticky ground mentioning ego after your willy waving about lynx.

Are you suggesting that a wing over entered at 100ft and exited at 101ft is not a wingover?
I still think that the cause of the crash was not entry height as you stated, rather mishandling the wing over.

yes he is........very trying

I take your point re the wingover, I misunderstood what you were trying to say - it is very probable that he flew the wingover badly - many people do because they haven't been taught properly - he didn't gain enough height for the recovery and his base height was stupidly low - that was my earlier point about entry gates, you have to ensure you reach a height at the apex to ensure you can complete the wingover safely. He clearly didn't.

As for ego - I merely stated my level of experience and knowledge regarding advanced manoeuvres - something that AnFi has repeatedly refused to do (type of licence, types flown, instructor quals, hours etc etc etc) on this and many other threads.

I am sure he is cleverer than me (especially at maths) but he has no skill in putting forward coherent, logical arguments in terms or language normal people can understand.

The fact he sees fit to question those like Nick shows whose ego is out of control.

AnFi - I do understand what you are trying to say - I just think you are wrong.

I don't think there is an 'Ultimate Load' based on coning angle and certainly not anything useful to be gained from trying to measure the coning angle from a video clip.

All you can say with some certainty is that overpitching is taking place because the disc has coned up - to infer that anything else is measurable ie CT/sigma, G load factor etc from that is guesswork and unproven theory.