Robinson helicopters added to safety watchlist

[Thomas coupling]

Dick Deaker - clue's in the name I s'pose.
To be honest, there's a bit of me in that flying but common sense has to prvail because I have responsibilities in life, to my family and to the people who work with and around me.
Flying like Dick in that video is great and exhilarating until of course it goes wrong. The NZ CAA must struggle to police activities like this....
But Robbo's make evolutions like this - much more financially viable so in a way, Robbo's exacerbate the problem. Then you throw in their fragility and voila, the perfect recipe for disaster.

One has to either be desperate for work, or not value one's life much to fly this way in the end.

Great fun - but, alas, those days are over for most of us.

[[email protected]]

Interested to know, if someone can help, some head limits on Robbies.
How much stop to stop teetering range ( degrees) on the 22,44 and how much cyclic range, fore n aft, right to left?
Thanks in adavance

Not sure why you would want that information Birdy - there is no problem with control authority or cyclic response on the Robbie (quite the opposite).

The teetering range is not the same as the flapping range as the hinges are separate and mostly independent of each other.

[WillyPete]

It's a much more modern machine though, flimsy.
I agree with you on why people knock them.
I thought it an incredibly agile and responsive machine (possibly leading to people thinking they can throw it around) and agree that responsible piloting would be the answer to the problem.
As it is, it's simply too unforgiving if it is really striking the cabin as frequently as articles indicate.

[Birdy2]

Not sure why you would want that information Birdy
Working on a hunch Crab.
I know the configuration of the Robbi head, i just need the specs.
I also know theres ample control authority......... .

[JohnDixson]

This NTSB Report:

http://www.rotorshop.com/sir9603.pdf

Makes for interesting but sobering reading and does mention a teetering limit at +/- 12 degrees. No detailed drawing of the head.

Good reading for any DER's in the audience.

[Hot and Hi]

Richard Mornington-Sanford's article about Martin and Simon

Originally Posted by FLY 7

I was never sure about that article. It attributes some justified blame, but is quite protective of the helicopter's design issues.

True. But that aside, with the greatest respect for Richard based on his other work that I am aware of, and with due respect for Martin who if nothing else was a highly qualified, experienced and accomplished competition pilot, I don't know quite what to do with Richard's advice.

Many of the things that Richard identifies (like peer pressure, get-there-ites, scud running, mental expectancy, suckers gap) helicopter pilots around the world experience or do frequently. This is the nature of the game. Else we would be like microlight pilots who only ever venture to the sky in the early hours of the morning, or just before sunset on a picture perfect day. The client wants to leave as late as possible (to get home before dark), and then still eats by 30 min into our buffer time; the clouds are low but we get through; the pax are definitely heavier than declared; the 'hand-luggage' of the paramedic is a 50 lbs heavy equipment bag; ... the list goes on.

The question is not where it starts (as we cannot avoid it in real life) but where to draw the line.

The Robbie flies perfectly well in 40 kts winds. It deals well with mild to moderate turbulence (giving time and opportunity if encountering the latter to fly out of it). +15 kts gusts are seemingly a non event. With very good tail rotor authority you can handle strong crosswinds in the hover. It is highly responsive allowing the pilot to handle any rotors or turbulences that I have ever seen, created by buildings or other structures along the approach path.

So where to draw the line? As Richard points out, none of the pilots who experienced inflight break-up of their helicopter, took off with the intention to die today. How do I know that turbulence is "light to moderate" (and not "moderate to severe", which Robinson disallows)? And are we saying that all those who crashed after encountering turbulence, have done so because they pushed on in conditions of severe turbulence, failed to reduce airspeed, and/or gave incorrect, hamfisted cyclic inputs?

Somebody please tell me. Richard's article is silent about this.

[rotormatic]

Revised Airspeed Limitation

Robinson adding new yellow arc on airspeed indicator:

http://www.robinsonhelicopter.com/se...s/r66_sb19.pdf

[Octane]

I just read the NTSB report. I'm not an aviator. My interpretation of the report indicates the NTSB could not in the end actually determine why the the rotor failures occurred in most of the accidents, particularly with the aircraft that were operating in normal flight conditions.
Is this correct? Disturbing if so...

[aa777888]

I just read the NTSB report. I'm not an aviator. My interpretation of the report indicates the NTSB could not in the end actually determine why the the rotor failures occurred in most of the accidents, particularly with the aircraft that were operating in normal flight conditions.
Is this correct? Disturbing if so...

On the other hand, since SFAR 73 took effect in the US, there have been very few "unexplainable" events, in the US at any rate. This would seem to imply that with heightened attention on low G and low rotor RPM recognition the vast majority of R22/R44 issues have been resolved.

On the other, other hand, as one of those people who must make a choice between flying Robinson or not flying, I am extremely vigilant with respect to potential onset of moderate or greater turbulence. I.e. I do not buzz along at Vne unless I am confident of conditions, and, when not confident, fly a rather conservative airspeed. Ridge crossings and valley exit/entries in particular. And, right now, in my rather low time condition, without commercial "pressures", I do not choose to fly when winds are in excess of 25KN, even though I am confident in both the ship and myself at wind velocities above that value.

Those mustering guys whip these machines around with great abandon at rather low airspeeds. That doesn't concern me, hooking a skid on a steer's horn notwithstanding . But at or near Vne one must be vigilant and conservative.

[[email protected]]

It's worth noting that the NTSB report is 20 years old and there should be a lot more data to analyse and perhaps draw some new conclusions from.

Is it just a poor combination of head design and rotor blade manufacture?

If it had been built with a simple teetering head instead of adding the flapping hinges, would that have prevented the extreme levels of flap required to strike the tail?

Hot and Hi

Somebody please tell me. Richard's article is silent about this.

you will just have to use your own judgement - that is what professional pilots do. If you are not sure of the amount of turbulence then don't enter it at Vne - go in slow and test the environment, giving yourself good safety margins and escape routes. You seem happy to be able to identify mild to moderate turbulence so if it starts to feel like the top end of your acceptable range, turn back or land but definitely slow down.

Birdy - didn't mean to patronise, sorry.

[Birdy2]

Yes JD, im sober now.
And for a blade to hit the boom is one thing, but to slice any part of the cab is way past the teetering range, shearing tusks n all.

While low/0 G is an obvious no no with teetering rotors, a couple of the listed breakups were at or near hover.
No bad air and no indication of a collective dump.
Iv spent alot of time watching and in mustering R22s, in all types of air.
These machines are under real stress, way over Franks intended use.
Most attention in the report is on blade instability because of its integrity and inertia.
Hell, what iv seen robbi blades do with a skilled mustering pilot, with never an inflight chop up, i think the tree they are barking at is the wrong one.
Just dont add up.

Time for more reaserch for me.


Didnt feel patronised in any way Crab, my skin is pretty thick mate.

[TTSN]

Originally Posted by Birdy2

Yes JD, im sober now.
And for a blade to hit the boom is one thing, but to slice any part of the cab is way past the teetering range, shearing tusks n all.

While low/0 G is an obvious no no with teetering rotors, a couple of the listed breakups were at or near hover.
No bad air and no indication of a collective dump.
Iv spent alot of time watching and in mustering R22s, in all types of air.
These machines are under real stress, way over Franks intended use.
Most attention in the report is on blade instability because of its integrity and inertia.
Hell, what iv seen robbi blades do with a skilled mustering pilot, with never an inflight chop up, i think the tree they are barking at is the wrong one.
Just dont add up.

Time for more reaserch for me.


Didnt feel patronised in any way Crab, my skin is pretty thick mate.

I think the key difference here is airspeed, in a lot of instances the R22 is operated to extremes in the mustering environment but we never hear about low G mast bumping or in flight break ups with this type of use (unless someone can tell me different?). At the higher air speeds is where forces get to a point where catastrophic failures can happen extremely quickly if the rotor is unloaded for any reason (abrupt control movement, extreme turbulence). It is actually quite easy to exceed Vne in an R22 which makes me think what would happen if through momentary inattention someone was pulling excessive MAP and exceeding Vne when they hit a few small bumpy bits of air which would normally be within the aircraft capabilities? If for example R22's were always flown at 60kts (maybe even 70kts) then I don't think we'd have any of these mast bumping and in flight break up incidents.

[megan]

If it had been built with a simple teetering head instead of adding the flapping hinges

Had not been aware of the flapping hinge, always thought it was just your regular Bell type teetering system, having had nothing to do with Robbies, but upon reading thought exactly the same as you Crab.

So the blade has two axis about which to flap. The head (teeter) and the flapping hinge. Seems a bit odd at first glance.

Would the inability of the blade to lead/lag in such a set up have any role to play?

[Birdy2]

TTSN,

On November 3, 1987, at approximately 1338 Pacific standard time, N8475A, a Robinson R22 Alpha operated by Helicopter Adventures, Inc., broke up in flight during a dual instructional flight near Moraga, California. The CFI and commercial helicopter pilot student, who was preparing to revalidate his CFI helicopter certificate, were killed. Witnesses reported observing the helicopter hovering at 400 feet agl when they heard the engine noise suddenly decrease, and a loud pop. The witnesses said they observed parts, "like sparklers," fall off the helicopter as it fell to the ground. The flight had originated 8 miles southwest, in Concord, California, about 1230, after having been refueled with 100LL fuel.

Hovering, ( no airspeed) 2 up and full fuel.
They are looking at rotor divergence at speed when light.
Not the case this time.
Every reported case states the machines were being opperated well within Franks limits, in mild conditions.

Quite a few witnesses state a tailwag or left right left right rolling before breakup, but none say a wild left roll ( low/0G) before breakup.

Sounds more like a main rotor phase issue, followed but a serious -AOA input to the MR.

Just an uneducated guess by an interested party.

[Birdy2]

Megan, the light metel robbi blades dont like to be flexed.
The added flap hinges are intended to relieve the bending stresses at the blade root when changes in G load produce changes in the coneing angle.

[Arm out the window]

Maintenance of the hinges would have an effect too, I would have thought - maintainers would know more than me, but the hinges in the Robbie head can vary quite a bit in resistance to movement depending on how old they are and how well they've been looked after, in my relatively limited experience.

They don't just see-saw freely like a Jet Ranger, and I bet the relative stiffness of the flapping hinge vs the coning hinges, and the overall stiffness of individual hinges, would make for quite some variation in the patterns of movement they develop when whirling around at silly speeds.

My thoughts are that if they're properly set up and maintained and the aircraft is flown sensibly, they will work as advertised, but if they were allowed to deteriorate it could be a different story. Again, I'm not massively high hours on type, but I've done quite a bit of throwing them around (smoothly and avoiding low g scenarios) without incident, and without feeling like I was coming close to any limits. Still, you wouldn't know if the blade missed the tail boom by a millimetre or a foot, would you?

I just try to treat them like any other teetering head machine - be smooth, don't bunt and don't flog it through turbulence.

[[email protected]]

Hovering, ( no airspeed) 2 up and full fuel.

From my limited experience a Robbie doesn't have the power to hover OGE with 2-up and full fuel.

Sounds more likely to be engine failure, rapid Nr decay and then self-destruct mode to me.

[Paul Cantrell]

Crab:

The teetering range is not the same as the flapping range as the hinges are separate and mostly independent of each other.

Crab, not sure if you quite realize how the Robby head works, apologies if I just misunderstood you.

Teetering and flapping are indeed the same thing on the Robby. The center hinge is the flapping hinge. The outer two hinges are coning hinges and perform the same function as blade bending in the Bell. It is possible to mis-rig a Robinson to flap around the coning hinges, but (I'm told) it flies really badly and you would know something was wrong with the rigging. Basically you set the friction of the hinges by the shim stack-up... part of the rigging (besides measuring the friction force with a special tool) is to check that when you lift the blades the blades move around the coning hinge: "Check coning hinge friction by lifting blades until spindle tusks clear droop stops. Hold one blade level and cone opposite blade. Rotor hub may not teeter as blade is coned. Repeat check on opposite blade".

There is 12° of flapping authority on the Robinson head.

The head design is indeed unique and patented by Robinson. Using coning hinges instead of a thicker/heavier blade kept the R22 weight low. Keep in mind that at the time, with only a 150 hp engine, Robinson was concerned with saving ounces, let alone pounds.

I've been teaching in Robby's for 30 years and have a great deal of respect for the people who produce them. I do think that the R44 is a better trainer than the R22, however there is a large part of the student population that doesn't seem willing to pay an extra $100/hr for the larger machine. Anyone who thinks it's a cute little trainer is crazy. It's a fun machine to fly, but it's nimble to a fault with not nearly enough inertia for low time pilots, IMHO, and it can bite hard if you don't know what you're doing. The R44 has much higher inertia and lots more available power in a training environment and I think makes a much better trainer than the R22 (but again, money). I learned flying R22s and it was a real financial stretch for me, so I totally understand people going for the absolute cheapest solution they can find.

I personally would welcome a different design head given the large number of inexperienced pilots who fly the Robinson. Of course, every head design has it's limitations, but eliminating the low gee issue probably makes sense.

[aa777888]

From my limited experience a Robbie doesn't have the power to hover OGE with 2-up and full fuel.

It will hover OGE just fine under those conditions.

[evil7]

Hey Birdy2,

The report doesn't say "full fuel" - it only states that the flimsycopter had been refuelled with 100LL!!
No mentioning of quantity!