lu
 

i recon the coning hinges on a robinson would never flap seperately because of the weight from the blades forcing the head to be flat with disc attitude, if no flapping , no lead or lagging??

I say tomAto and you say tomAHto.
 

To: vorticey

The rotor and blades are coincident with each other (flat) only when the collective is full down. When collective is pulled the blades cone up to the point where centrifugal forces on the blades are effected by the aerodynamic lift. In a sense the blades have flapped up and will maintain this relative position unless effected by aerodynamic forces or input of cyclic pitch and then they will flap up and down in relation to each other.

Other things that will influence flapping are:

1) Flapback during translational lift (flapping to equality).
2) Gusting
3) Flying out of trim.
4) Side slip
5) Incorrect recovery from a zero G episode.

The extent of flapping is effected by the extent of the maneuver (3,4 and 5 above). This flapping can range from minor or acceptable levels to severe enough to cause mast bumping or rotor incursion.

Now let’s assume you are correct and there is no flapping which would result in leading and lagging. If this is the case please explain what forces are present in the rotor system to cause the elliptical wear pattern on the cone hinges and to a lesser extent on the teeter hinge.


:confused:

Lu,

I agree because the Safety Notice reads like a microsoft answer.

As for the underlying causes, that isn't a debate I wish to be in at this time.

Tammy,

A Dinky refers to something small, like the dinky you possibly wear on your high heels, or your sense of humour perhaps, and why would Army flyers shout any instruction when flying solo?:rolleyes:

Hi gang,

I agree with "buitenzorg"(was it...?)

It seems the whole world cracks down on Robinson when one comes down and everything points to the design.

Why do there have to be SN´s from the factory, warning people from overspeeding the rotor on take off? Well R-Drivers know the trick to get off a little easier on a hot day, just override the governor and take off with 106 - 108% rpm. Normally you are off in 5-10 sec and let go on the throttle and the governor do his work. I was surprised to read in the SN, that there are crackheads who actually pull it to 120% !!!!!

It is always the same, for some idiots there are no rules and when something happens it goes back to the factory.

By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out.

Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal.

If you IGNORE any indications of "out of normal" on ANY HELICOPTER you are bound to get into trouble!! Not just on Robinsons, however I found that the Robinson has an extremly high tolerance on these ocasions and is comparatively inexpensive to fix (ups - repair, I mean...), resulting in little down time. I do not see that on the Bell´s of our competition!

Another feature of the Robinson Rotor is a max lifetime of 2000hrs or 10 years - whatever comes first. That is active safety! No matter how good the blades look - 2000hrs and the go!!

I have been flying Robinsons on the edge for about 4000 hrs now and never had any problems with blades. However I suggest to all Helicopter Schools to do a little sermon now and then on HOW TO NOT ABUSE helicopters!!


:) 3top

The Nr Fairy,

Thanks for that link, I wasn't aware of those accidents. But just imagine what peak stresses an R22 with two aboard must undergo during the hard low-level maneuvering of mustering flights. I wonder if a mustering ship has ever been instrumented to record that? Probably not.

And another one:

Although Robinson is the number 1 in safety - at least in the statistics: I am afraid the relative number of R´s in accidents will increase. There are just so many out there already and getting more everyday, at a high rate. If half the world drives Toyotas, well a lot of Toyotas will be in accidents.
It will still be the safest machine per flighthours!

Besides I think Robinson is very conservative about his helicopters.

Look at the new Raven II, finally we got a max grossweight increase of 100 lb to the new engine! I do not believe that there had to be any structural changes done.

Fly safe!

Last one:

Talking to THE safety course instructor from Robinson about R22 flying, and that man should know, he said he never saw such extreme flying like cattle herding in OZ. I thought I did my share on tuna boats and fumigation with R22. According to the man thats all peanuts compared to the Australian way of cattle mustering!

Out for today!!:) :) :)

Cone hinges Vs Flapping hinges
 

To: 3top

Quote:

"By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out".

"Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal".

If you look at the patent application for the three hinge rotor system referenced above Frank Robinson makes the same point about reduction of the bending stresses when compared to a Bell system which has very high bending stresses at the root. Whether the Robinson’s’ cone hinges are the best invention since the underslung rotor is a bit of a stretch. If the cone hinges were not incorporated the rotor system would be so heavy as to minimize any payload for the helicopter.

Adjustment of the friction on the cone hinges preloads the system to minimize any relative movement on the stack-up of the parts in the assembly. The point you made about the change in friction level on one cone hinge causing a vibration is correct however it is also true when there is an imbalance between elastomeric elements in a multi-blade system. For instance if the elastomeric dampers on the Apache differ by more than 5% the aircraft can enter into air resonance and self-destruct. The same is true for hydraulic or friction dampers on other helicopters. The Robinson head is in effect a semi rigid semi articulated rotor system and being semi articulated (free to flap) it is subject to the same forces that generate leading and lagging.

Hi Lu,

unfortunately my theory on helicopter design is rather very limited. I try to argue based more on common sense......
Though I have a mechanical engineering education it just lets me understand the basics what you and guys like Nick Lappos are talking about when the going gets deep...
But I am glad I do not disintegrate in the air when the friction values on the Robinson head change for whatever reason (like those poor guys in their Apaches...).

I had the unfortune to fly one Robinson 44 with one completely lose coning hinge once. It just jumps with one per rev.........
I still could fly it back to the shop.
The unlucky son of a b... of a mechanic did not heed the advice in the maintance manual, that the hinges have to be ABSOLUTELY clean during assembly. Grease - even fat from your own fingers are too much for teflonbased friction bearings. That happens when people (mechanics, pilots, etc.) know it all better than the guys who built the machine and write the manuals!!

3top

PS: Lu, as you are the "one" who started the 18 degree offset discussion: Do you still have all the arguments and responses?
I got to late into PPRUNE to catch that forum. However I would like to read about it. If you can send me an e-mail with some info on that!

Thanks:)

3top

A Search using the string [Robinson AND degre* AND delta] should bring up all the relevant threads.

Dave J

lu
 

i think that the examples of "flapping" you gave are not realy flapping but teetering. the only way the flapping hinges move is by changing the load on the disc either with weight or high 'g' movements.
for example when flap back occures the head tilts back with the disc, not just the blade swiping past the nose.
are you sure that the elipticle holes arent just wear caused by coning under power? this would let the blades lag a bit behind their original line.
what do you recon?;)

In response
 

To: 3top

The Apache example was a bit extreme. The point I was trying to make is that rotor systems are balanced both statically and dynamically and if some thing goes out of balance a vibration will ensue. In the case of the Robinson head if the friction is not the same on both sides you will get a vibration.

To: vorticey

If I understand you correctly you are saying that the only movement on the cone bushes is when the pilot pulls collective and the blades cone up taking on the weight of the helicopter with this upward movement being balanced out by centrifugal loading on the blades. In your explanation you state from that point the blades do not move when cyclic is applied and at that point the rotor system is just like a Bell.

If the increased lift on the blades when lifting off is sufficient to overcome the friction on the cone hinges then it is also possible for the changing aerodynamic loads on the blade due to cyclic pitch changes to be sufficient also to overcome the friction on the cone hinges.

The flapping due to improper control input is also sufficient to overcome the friction to the point that the tusk can strike the stop and fracture either itself or the stop.

Your statement about the loads stemming from coning being the cause of the wear on the cone hinges is true. Even though the head is underslung like a Bell the coning or flapping can cause a difference between the driven axis and the driving axis when cyclic is pushed and at this point the forces of conservation of angular momentum take over and you get leading and lagging. Using Nicks’ explanation this results in edgewise bending which cyclically loads the blade root and the cone hinges causing (I assume) the cracking of the blade spar and the wear on the cone and teeter hinges.

:confused:

for an effective way to show a stude the remarkable fact that the r22 does what it does - show them it in bits in the workshop! to think that when all those fragile little bits do what they do when bolted together might just let some realise the fragility of it.

Personally, you wouldn't get me in one, but that is another story

The other side of the coin.
 

To: STANDTO

Along the same line I would suggest that you let a Robbie pilot either high or low time look at a disassembled head that is going in for a 2000 hour check. If you really want to scare the crap out of them have them look at a rotor head removed from a cattle mustering helicopter for its’ 2000 hour check (assuming it lasted that long).

:eek:

Lu,

Remove a mustering heli's head for a 2000hr check............but it's only just been run in:D


Robinson's like any ac can and will bite. It is a testament to the ac's strength when you see what ringers put them through in the australian cattle industry.

One unfortunate accident with loss of life involved a blade seperating at the root. ATSB investigation revealed the ac had overflown hour in the order of of 5-6000hrs ABOVE the 2000hr overhaul:eek:

Must admit I do like the R22 one up:)

Flying cowboys
 

To: Hone22

At the height of my making posts on this forum regarding the restrictions placed on the R-22 and R-44 relative to FAA AD 95-26-04 I had the pleasure of watching a Discovery channel program about cattle mustering in Oz. I was absolutely amazed at the close in maneuverability of the R-22. I had seen many of them flying but not in that way. However what I saw amazed me in the fact that 90% of the flying was in total violation of the AD and its’ attendant restrictions.

I had previously mentioned seeing an R-22 rotorhead that exhibited very strange wear patterns on the cone bushes and the teeter bushes. I saw this rotorhead at Geneva Aviation in Everett, Washington and was told that it was off of an Australian R-22.

:eek:

Hone :

Can you confirm that, please. You're saying the blade was run for about 7,000 hours ?

****ty death ! No disrespect, but if someone knew about that, why the bloody hell didn't it get stopped ?

Yes Lu, those mustering machines can be worked hard. But this is not the only cause of the wear in the hub and other parts of the helicopter. The red dust which is prevalent in most Aussie mustering locations also adds to wear. This dust, usually called ‘bulldust’, is as fine as talcum powder and gets into every nook and cranny of these machines. I suspect the wear you saw had its fair share of visible scoring. Its just a part of outback life.
Maybe Frank should manufacture a dedicated mustering machine. He could use the R44 engine/powertrain and rotors (with the hydraulics of course) in an R22 airframe. :eek:

LU agree, About twelve years ago I found a crack on the underside of an R22 blade. The crack was about three and a half inches long and about 24 inches out from the spindle area.
It had started in a small dent caused by an ejected shell from an SLR. The dent had been there (according to the pilot) for eight months. Yet the pilot had not reported any increase in vibration.

Tammy Tammy Tammy, methinks you had better learn some English before attempting to be pompous.

Verbally-calling-out "...turning left and signing off!"

Frank Robinson does very few "pointless" things.
Low time pilots do many.

Then there are what seems to be low post members of rotorheads...

The question was answered, no need to be , hmmmm ... annoying about it.

Autorotate a R22 in 1.1s ?
 

Perhaps I'm becoming paranoid the more I fly but I worry about being able to react quick enough to autorotate in around 1s during flight.

Robinson explains that in cruise we have 1.1s before Nr goes too low, and this low figure is due to a low inertia main rotor.

Do you ever worry about this ? Are you confident you could react so quickly if surprised by an engine failure ? Do you pray to mother Lycoming or do you not even think about it ?

Also, I believe other machines to be much more forgiving but know of no details - perhaps you have a few examples to show how this can vary ?

Yes, when you put it like that 1.1 seconds to react does sound scary, but think about what happens on the roads.

Most drivers do not obey the two-second rule. If you do you are one of the exceptions (and overtakers will slot into the gap you have left :mad: )

So as you're blasting down the outside lane at 80 mph, what is your reaction time if something goes wrong in front of you ?

That's right: probably 1.1 seconds or maybe even less.

Run into the back of a lorry and you'll be just as dead.

Also - unless you run out of fuel it is very unlikely that the engine will stop suddenly, completely, and without any warning.

So check your fuel and your carb heat. Keep an eye on those T's and P's, and be ready and alert.

But don't get paranoid: it's much more dangerous on the roads !

I'm with G on this.

When you consider that figure alone, it's scary.

But ...

You'll likely get some sort of warning of impending engine failure before it drops out. (unless out of gas as G stated)

And if you consider that as soon as you begin moving the collective down, you begin to recover, or at least slow the NR decay itself. (Remember max glide is at a low RPM).

The 1.1 is to stalling the blade if you do nothing, if you get the collective moving when you notice something wrong, more likely than not you wouldn't decay to the rotor stall point.

But to let you know, you're not alone on the train of thought, it hits everyone flying robbies every so often.

Another way you could remove some of that trepidation (so to speak) is to go get some dual with a CFI, and brief for some power failures. Mine just states power failure and expects me to react accordingly. :)

Hi Latecomer,

The 1.1 sec reaction is just that, a reaction, to think about it, to start checking gauges or trying to work out what is wrong and unfortunatly we will all be reading about you, the reaction is what you need, after you have got into the Auto mode then start to check your gauges, That is the time to work out what has happened, if nothing then feed in power and proceed, if in fact all is quiet then your reaction was spot on, hope you train and try this regular, for after all your life relies on your deadstick landing ability
Peter B

Because you're worrying about it now, you'll have the right mental attitude when flying - be surprised when the engine keeps running( and not the other way round)

1. The 1.1 relates to the climb - lots of pitch, and assumes you did absolutely nothing as RW-1 says
2. Keep your hand on the collective as much as poss (especially in the climb
3. Fly airspeeds in excess of 60 kts as much as poss (in case you need to convert airspeed into RRPM during the exciting bit at the top)
4. Use flared entries into Auto, despite what folk may say...
5. Fly as high as practical ( in case you need to convert height into airspeed for the bit at the bottom)

You've got longer than you think (but not a lot!) Don't let it stop you having a fun time:D

nonradio:
"Use flared entries into Auto, despite what folk may say..."
What do folk say? I've only ever heard people say "Use flared entries into Auto."
The 1.1 seconds Frank Robinson talks about is if you don't come back on the stick.
I've had demonstrated from 90kts a throttle roll-off in an R22 with no lowering of collective, but Nr maintained solely by steady backward movement of the stick, for second after second after second... I wasn't timing it precisely, but it was pretty impressive.
I have been unable to find evidence of any engine failure in an R22 that was not due to fuel starvation, oil shortage or carb heat mismanagement. Anyone know of one?

I read in one of the NSTB reports a year or two ago about an engine failure in an R 22 from a stuck exhaust valve while in a 100' hover or something to that fact. May be the reason for the valve guide clearance inspection required every 300 hrs?

t'ain't nat'l - you'd be surprised at how many (inc TREs, sorry "FEs") want to see the attitude held constant (!) during entries. Of course each and every one (because I know at least one who did! ;-) ) would flare like ******* given a throttle chop unannounced, I fancy...

I gave up demo-ing that "1...2...3...4.. etc" after a certain h. experienced FI was killed - he was known for very enthusiastic demos of that and Lo G.

Maybe I'm just getting old

I was always taught flared entries to auto, the main reason being to raise the RPM, or give yourself more chance of doing so if you'd been a bit late on the collective. Then in the US someone told me not to. I can't quite remember why; I just remember thinking it seemed to make more sense to keep doing what I'd been taught.

So what is the thinking on both sides of this one?

Whirly,

The reason why some people get worried about the flared entry in Auto's is that while it's fine in the event of entry from 104% RRPM, in a real failure when RRPM has dropped significantly an enthusiastic flare could quite easily remove your tail!

Still at least you won't have to worry about timing that flare correctly! :D

With regards the 1.1s......it's in the cruise, in the climb it will be much much less. The moral of this story I guess is climb as gentley as possible (min collective pitch) without comprimising safety and only fly over nice soft flat things.

Either that or spend a few more pennies flying something with a bit more inertia.

Fly gentle
CRAN
:)

Piston engines very rarely cut out instantly - even running out of fuel is likely to give you a couple of coughs to warn you before power disappears. As a result, the 1.1 second scenario is highly unlikely.

A well-designed and properly maintained piston engine is a very reliable piece of kit.

The key seems to be keeping your hand near the collective, just in case.

My understanding is that a turbine can cut without warning - perhaps some of you high-time turbine pilots can confirm that through personal experience?

The Nr decelerationspeed depends on various direct and nondirect factors. Due to the constructiontype, weights of dynamic components, blade profil with specific characteristics,.... there are significant "fixed" differencies between the helicopters.
Flight conditions are responsible for the next input. On a climb Nr will decrease faster than on descent. With an airspeed in the the upper range of the approved speed limits Nr will be decrease faster or on some helicopters it's not possible on higher airspeeds to reestablish a 100% Nr (on steady AR, without flare). A/C weight is important...
Therefore it's not possible to determine the one and only special time to an uncontrollable Nr or uncontrollable flight. And what's the limiting factors? Bladebending with cracks, blade stall, airframe strikes, .... ??? There is a time window, that depends on the named factors.
The publishing of such times is in my opinion to alert the pilots and to give also the unexperienced jocks an impression.
It's not necessary to press water out of the pitch. "Dead man" curve is important and to feel the situation. I'm on safe conditions, unsafe or really dangerous flight conditions.

R22 International Operating Cost
 

Could anybody help me...

I am trying to determine the cost of operating a new R22 BII and a mid-life R22B commerically in the UK, US & AUS.

Would it be possible for some of our UK, US and AUS operators to give me an honest breakdown... perhaps

Cost of finance (if applic.)
Overhaul Allowance
12 year deval.
Scheduled Maint.
Unscheduled Maint.
Insurance
Hangerage
Fuel
Oil
Others/Misc

Please state the country of your operation.

Many Thanks
CRAN
:confused:

I am about to do an endorsement on the Robbo...so am quite interested in this topic.

Surely the flare-or-not-to-flare question depends on your heigh/velocity predicament? I was always taught to just lower the bloody lever, keep it in balance and go for the correct speed - depending on your aimpoint. Automatically entering a flare could be risky, lest you be left at the wrong height with no speed?

My main focus is on the 'surprise' aspect.

It's true that the piston engine will generally warn us before a major failure, and of course, we should all aim for flight parameters that 'help' the autorotation (speed, rate of climb, height...).

It's also true that we learn a 'reaction' to move before we think.
And maybe that should just be 'get the collective down' asap.

Flare or not on entry - is it not a theoretical question ? Given the (huge) surprise of having to aurotate, I would agree to dropping the collective, then stabilising balance & speed - if the surprise is real, this is the reaction moving before my mind starts thinking.

To me, this (re)action should be as simple as possible. And practising this is how be build the re in the action no ?

A recent overspeeded engine failed for a friend (who was hovering and is OK) and real un-announced engine failures do happen.

It does seem that I might be right to be a little uneasy whilst VOR or COM twiddling, or even touching my map...
I cannot say that all the time I fly, I'm ready for it... I wish it was true but it's not.

If this was 3 or 4s then we're in another world no ? Is it only large turbines that can offer such a margin ?

I've never had an engine failure on a single engined helicopter, thank god, but one of my instructors did once. I see that there has been some discussion as to the best method of entering autorotation. His biggest point was that it will not happen the way you practice it.
When the nasty instructor says "practice engine failure, GO", you smoothly lower the lever and keep the aircraft straight with pedal. In reality, he didn't immediately realise that the engine had failed. The first thing he noticed was that his Huey was flying sideways due the pedal he was using to counteract the tourque that the engine wasn't producing anymore. He was still trying to figure that one out when the low NR warner went off. Luckily the Huey has legendary amounts of inertia in the blades and he was able to recover.
I accept that he was flying a turbine and that pistons are less likely to cut suddenly, but even so, it is impossible to truly simulate an engine failure into autorotation.

Two flight instructors, with together more 8000 h on helicopters and more than 4000h only on Bell 206 on a checkride. Big airfield for us alone. Let's going to see an AR not the normal (entering, hundreds of time practiced and teached) way ... Simulated hostile area take off, light a/c, in 400 ft ground, IAS 50 kt, climb rate >1200 ft/min, 100% Nr, rolling the engine to idle. Great astonishment on the next seconds about what happens. Rapidly decreasing NR (<90% initially), immediately audio warning, in line with the same way, rapidly decreasing IAS (<35 kt). Lowering the pitch to hold the Nr decrease, pushing the stick to get some IAS and to level or nosedown the helo.
First impressions on our mind to get low G, MR vibrations. Never experienced bad a/c control (aerodynamics and it needs time to establish the AR airflow on the blades). Really impressive descending rate.
Pushing the stick and making airspeed decelerate Nr (on AR transition, also aerodynamics) and a light a/c on AR with complete downed pitch (without flare) works hard to get some extra MR rounds.
What is to do? Flare for Nr, or going for 50-60 kt AR Speed?
Seconds running away, good old earth, we are coming...
Story ended in the badest AR touch down, i have ever made with a very long running distance on the ground and praise the lord and the light a/c, without any a/c damage. (Nr all the time no more than 95%, landed with leveled a/c, IAS 35 kt, and skidding on the ground)
Eye to eye view between us, never, never on that way...

:( :( :(


Hey all you single engine helo drivers! On how much missions you have started the flight with an equal entry situation???????

How much pilots makes thousends of hours around the world alldays within the "dead man". Longlining, cropdusting, seismic or measuring missions,....,.....,.....,.....,............... ???

But don't worry! Flying is leaving the ground with technical assistance. And how much important parts could fail on a helicopter :) :) :) ?

(Only gearboxes, drive shafts, controls, engines, blades, fuel systems, ignition, hydraulics and some other parts ........... :)

And unfortunately tec failures ar not the specific dangerous part of our job :(

If your mind is blocked now, stay on the ground and start a career in a tax office! But sometimes you have to drive a car and the brakes could fail.....

Obviously, as tecpilot pointed out, the actual auto entry that you will use depends a lot on which flight regime you're in.

Helicopters like the B47 and such have cruise speeds that are only slightly above their autorotation speeds, so it's not surprising that inexperienced or low-time pilots like What-ho Squiffy are confused as to auto entry techniques.

However, if you're in a faster ship and you're cruising along, fat, dumb and happy at a speed above your "best auto" speed when the engine quits, then it is proper to make an aft cyclic input either slightly before (if you happen to be tuning a comm radio with your left hand) or simultaneously with lowering the collective. PHI trains this technique and only half-jokingly calls it "graduate-level flying." The idea being: don't just simply slam the collective down when the donk bites the big one.

This gives you the advantage of TIME, mates. As you decelerate to best-auto speed, you can look for a spot, turn into the wind, crap your britches, or make a mayday call on the radio.

Lowering the collective alone at high a/s has a tendency to make the nose drop. At high a/s, lowering the nose and the collective will produce a very nice sink rate, indeed! This is obviously not desireable.

At lower speeds and altitudes (at or below best-auto speed), it should also be obvious that making an aft cyclic input would be wrong. In this case, all you can do is lower the collective as expeditiously as possible and land right underneath where you are. Good luck. And if you have enough altitude, you *might* have time to lower the nose to pick up "best auto."

A worst-case-scenario for any helicopter would be an engine-failure during a high-power/low airspeed take-off. It seems that the R-22 is particularly unforgiving in this area. For this reason, it would probably be wise to avoid such a technique in a Robbo unless absolutely necessary (e.g. people shooting at you, or no other alternative).

In cruise flight, R-22 pilots can probably tune their radios, fold their maps or pick their noses with impunity, safe in the knowlege that if they do run out of gas and the engine quits, the rotor won't come to a complete stop in the time it takes them to get their boogery fingers from their mouth to the collective.

But on take-off, HOTAS at all times!

Trivia:

"It may be of interest that the Flettner ships [intermeshing configuration] have been landed from vertical descents in the manner characteristic of autogiros, (by pulling back on the control stick after nosing down from vertical descent). Collective pitch was not used."

" .. the [rotor, not engine] governor was set at 160 rpm. The collective pitch lever allows the pilot to override the governor and adjust the pitch.
_______________________

The above is reprinted from the June 1947 issue of American Helicopter. :eek:
How far have helicopters advanced, over the years? :confused: :confused: :confused:


The complete article can be found at; http://www.unicopter.com/0474_2.html

Dave J.