As mentioned, the missing parts in the accident picture departed the aircraft in flight which tends to cause severe control issues due to the loss of weight/thrust at such a long arm. How it ended up on the right side is probably more based on chance than any "controlled" effort. A number of helicopters that lose the entire backend tend to roll inverted depending on internal loading. What caused the T/R assy and fin to depart has still not been determined.

I apparently failed to clarify the source of my confusion. In the subject photograph, the aft end of the tail boom is bent to the left, which would indicate a left-hand rotation of the fuselage as it impacted on its right side. I did read the report, and do not doubt that the helicopter rotated violently to the right after the loss of its tail rotor and associated hardware. I'm sure someone on this Forum can explain this apparent (to me anyway) contradiction.

Any way, back to the question at hand. I read with interest the FAA Airworthiness Directive (effective 22 May, 2020) concerning cracks found in the tail rotor blades of certain R-44 and R-44II helicopters. The AD indicated that it was believed that: "The cracks were caused by high fatigue stresses due to resonance when the blades were at high pitch angles from large left pedal inputs." I did not see any mention of this AD in the ATSB Preliminary Report. I'm not sure how long or for how many hours the owner of the accident helicopter operated it out of the industrial estate on the north side of Broome, but from looking at the ATSB Preliminary Report, it could have been for as much as 40 hours or so. It was reported that operating out of the industrial estate required a steep if not vertical departure, which would have required a lot of power and a lot of left pedal to counter act the torque ... just the thing that may have caused the TRB cracks described in the AD. Loss of even a portion of a tail rotor blade would have resulted in severe imbalance, possibly involving forces sufficient to cause separation of the tail rotor gear box. The ATSB report described their examination of the tail rotor gear box, and no defects were detected.

Tail rotor blade loss may or may not have been instrumental in the cause of this crash. At this point, who knows for sure? It's a puzzler, and hopefully, the cause of the crash will be found before any further similar crashes can occur.

Regards,
Grog

It does not take a lot of left pedal to make a maximum performance take-off in an R44.

pistons rarely run out of pedal, torque isn’t in great supply.
they do regularly run out of horses tho.

Very true. I regularly wish that Robinson, who has an done an excellent job of embracing everything that both Garmin and Genesys Aero systems has to offer, still has not offered modern electronic engine instrumentation. I would very much like to see an FLI with audible warnings for approaching power limits, and for high rotor RPM. Low RRPM warning provisions are fine as is.

I disagree with the sentiment. It’s not unusual to have a “limit” that the pilot has to respect. An FLI simply combines several possible limits (NG, ITT/TOT, Torque for example) The “FLI” On an R44 is the MAP gauge. Of course the limit must be calculated for the atmospheric conditions.

The R44 has more installed HP than should be used at sea level.
Long before it “runs out of HP” (RRPM droop), the MAP limit has been ignored, and the drive train has been abused.

Obvious statement. No aircraft will take itself outside of it's performance envelope.
When there is less headroom or margin for error then the possibility of an exceedance increases, more so when at altitude and warmer temps, especially if you didn't plan properly.
Many a robinson has lost its battle with gravity for this reason, all played out with that single note shriek from the panel.

Unfortunately the limit isn't always understood or respected, so perhaps making it more difficult for someone to be foolish isn't a bad idea.
Not that it is relevant to this accident.

Wonder if the TR flex coupling let go, that could have created an effective little circular saw inside the tailboom which would explain the fairly neat cut.

Ridiculous. Guimbal did it right in the G2. I loved the FLI when I flew it. So much simpler and easier, and therefore safer, to manage engine power limits that way.

You're right in saying that. It's actually called an "MLI" (Multiple Limit Indicator) in the Cabri, and it does a cracking job at showing you whether you're limited by torque or throttle and making it very clear to you when the helicopter is unhappy with what you're doing (I've typically seen the switchover from Tq limitation to Throttle at between 3000-4000ft depending on the weather). It's very useful when the atmospheric conditions are always changing (such as when you're climbing / descending), or crossing high terrain in the cruise (knowing how close you are to full throttle etc).

I agree that failure of the aft flex coupling could cause all sorts of havoc, but tail rotor blade failure is still my guess. Take a look at this photo from the ATSB Preliminary Report.

Well, I've not had much luck in posting photos in this forum, and I apologize for my inability to post photos. Just take a look at the report; however, the next paragraph should provide enough information, since it describes a related feature of the photograph.

A "Tail rotor blade section" was found approximately 100 meters south of the "tail rotor and gearbox" remains, which indicates an in flight break up to me. That plus the AD on tail rotor blade cracking indicate a possible in flight tail rotor blade failure. Such a failure would also account for the separation of the tail rotor and gearbox and the fragmenting of the aft bulkhead of the tailboom.

Just a thought, but it may be interesting to ask the pilot, who flew the helicopter and discovered the pedal "vibration" on his flight of 29 June, 2020, whether or not the vibration changed with right or left pedal movement.

Just my opinion.

Regards,
Grog

If that turns out to be the root cause, this issue goes all the way back to 2012 when Robinson published service bulletin SB-83.

Since the TR was the focus of attention and experienced eyes were looking at it I doubt there was anything obvious which can be seen from outside was broken/loose/missing. I am guessing something inside the tail cone which was hidden from the view came off

Not so neat, look at the photo at #79

Yes the flex plate is visible, but that is just the shear point when the rest of the tail departed the scene.

Because you “loved the FLI“ (which apparently is an MLI) when you flew the G2; me claiming that the MAP gauge in a Robinson indicates the first power limit is “ridiculous”?

Are you qualified to fly a helicopter?

Is English your first language?

I tend to agree. A turbine helicopter has three possible limits - Ng/N1, Tq and T5/T4/TOT/ITT Add another engine and borderline ambient conditions, and you could be hitting two different limits more or less together. E.g max Ng on one engine while max torque on the other (I’m mainly talking about take off or OGE hover).. This is when an FLI really comes into its own. How many limits are there on an SE piston aircraft? Observe MAP limit per placard and?

"Yes" to all three questions.

With respect to the first question, the point I was trying to make was that there should be automation associated with showing the pilot where the limits are and you didn't appear to agree with that position and, worse, you tried to equate a simple MP gauge with an FLI (or MLI, if you prefer). In both cases I find that ridiculous. That is a far cry from merely confusing a minor point of lexicon, i.e. FLI vs. MLI, both of which perform the exact same function: fully automating the process of indicating to the pilot how much power is being used, and how much power is left, before one or more applicable limits are exceeded, be it torque, time, temperature, pressure, etc.

Have you ever flown a piston helicopter? On both the Robinson and the Cabri, there are limits associated with manifold pressure, outside air temperature, time and available throttle.

On the Robinson the pilot must figure out what the manifold pressure limit is based on the current OAT. This is done by the crude method of looking at a table and interpolating the numbers (or just choosing the more conservative). The pilot must also keep track of time manually if using power in the 5 minute limit range (as determined by the aforementioned tabular lookup). On older Robinsons the table can be seen if you can crane your neck back far enough to see it on the overhead, and it's printed on the Robinson checklist card as well (or the POH if you really want to crack a book while flying). On newer Robinsons they place it on this cool little rotating cuff on the cyclic arm. And there is no indication of how much throttle you are using until you run out, something that can come as a surprise given the action of the throttle governor, unless you are in one of the newer serial numbers that has the "full throttle" indicator light (or an older one with that option, which seems to be a bit rare), which unfortunately gives you little warning of where you stand until you are standing there.

Contrast this with the MLI (see, I can learn ;)) on the Cabri, which takes all that into account and shows you continuously computed power in percent, with the 5 minute limit area being clearly designated by a yellow arc, and a convenient countdown timer when in the yellow arc. Plus the MLI conveniently switches between horsepower limited regimes and throttle limited regimes, the latter occurring at lower density altitudes, of course, thereby clearly indicating how much reserve remains in any situation.

Thus, while the limits and methods of measuring power differ in turbine and piston helicopters, they both can present sufficient complexity such that the presence of automation can be a significant boon to safe and easy operation. Certainly both types can be flown with round dial technology and rely more heavily on pilot computation, skill and attention, but better solutions are readily available nowadays.

There are two practical dynamic limits the pilot has to manage manually: map pressure and Vne. The latter also changes with temperature and altitude (and obviously other fixed factors) for reasons unrelated to the engine but it requires constant placard checks.

Don’t get it really.
For most use cases, the only place that MAP should be a problem is at lift and landing, both are known quantities.
There are more demanding use cases but in those instances your attention would be on avoiding trees and wires.
if power management is so demanding as to be a safety issue then that pilot shouldn’t be given a license.
there are way more complex variables and aircraft to manage and you can’t instrument-out stupid.

Yes I have - thank you for asking. It didn’t have a governor either. I also learned to fly in variable pitch propellor FW, that also had MAP limits. But that was in an era where I was taught to set RPM by aural cues (then glance at gauge to confirm) and could set pitch and bank angles by looking out of the window (see other thread about how you don’t do this in an AW139 it seems).

Hey - I have seen the YouTube video explaining how the MLI works, and the cockpit displays look great (no dispute) and will reduce workload, but there is no getting away from the fact that the MAP is the FLI.

A real thread drift going here, so in an effort to continue the direction, having a bunch of hours on the R22 and Cabri, aa777888 has it bang on and I am amazed at the level of (incorrect) vitriol coming his way. Just because a manual MAP lookup can be done (tricky in flight when conditions change), and has worked (most of the time) over the years, does not mean a simple, clear and dynamic display isn’t a better idea for everyone regardless of experience level. I have also flown in conditions (not even particularly unusual) where fuel flow was the limiting factor before MAP - not that I hit the limit, that would be poor form indeed.

Thinking about it, with Nav, I am sure everyone here can use a map, but isn’t a modern moving map display easier all round? Doesn’t mean someone isn’t worthy to fly - that would only be case if they couldn’t fly without a moving map.

I think the word ‘ridiculous’ may have got people’s attention. Got mine.

So for the number of landings and take offs you are likely to do in a sortie, working out the MAP limits is too difficult and demanding and requires a digital display? How many of you are taking off and landing at vastly differing density altitudes on a regular basis in a Robbie?

Proper Pre flight Planning Prevents Piss Poor Performance - 7 Ps of aviation.

Cabri are obviously superior to Robbies if the MLI is so good.

Quite often in California actually, where I take off at 400', may eventually climb to 6000' en route due to mountains, and land at perhaps 2500' (Las Vegas) while temperatures are all over the place, cooler near the coast and very hot over the desert.

I see lots of temperature variations when operating between sea level and 3 or 4 thousand feet (rarely get above that around here), or on a cross country that starts in the cool early morning then you start to see the heat of the day, or from inland to the shore or vice versa, etc., etc. Nobody said it was hard to manage, or do, or whatever, just that it would be easier and possibly safer if a machine did it for you. Just like it is on a turbine. And don't forget the throttle limit factor, hence an MP gauge cannot be an FLI, it does not account for that, even if you are willing to give it a pass as an FLI because you looked up the exact MP limits vs. temperature for that particular moment in time. And being able to understand your available throttle is a nice safety improvement.

Obvious troll, crab, no bite... :=

aa777888 - as others point out, MAP limits are only a real issue when taking off and landing - are you doing that at varying alts and temps or just cruising through?

The throttle limit is pretty obvious because if you keep pulling the Nr goes down.

Didn't think you'd want to admit to Cabri superiority:)

CCGame - If you don't know what the likely conditions are at your intended LS (you only need a phone to find out) what pre-flight planning are you doing? The conditions in Vegas are very predictable so not much thinking required.

You could have a copy of the MAP placard on your kneepad or even on the ubiquitous I-pad so why crane your neck?

How many owners would pay the extra on a Robbie for an MLI? And are they pestering Robinson to provide one?

Seems like a problem that doesn't need a solution, just a bit of planning required.

Indeed.
Who spends their time staring at a panel or waiting for a caution to light so you can work out you are near a limit.
In the 2 hours or so that these aircraft can manage to fly, density conditions can only change so much.
You plan performance and loading for the highest and warmest condition in flight.
After that, fly with some accuracy, preferably into wind and the aircraft will perform as expected.

When the lever meets the armpit, an exceedance approaches.

I would think they could do metallurgy tests on the pieces and get pretty close to finding out what gave way first. Not sure if they will do that though.

Most of my flights lately are cross country. Interestingly, those are the flights that have peaked my interest in having an MLI or FLI even though it's a piston single. The quick hops are, as you say, not an issue, just figure stuff out for takeoff and landing. But I find when I am trying to make time and run MCP the entire way I keep a critical eye on things. For me it's not unusual to see a OATs variation of 10-20 degrees during cruise on a cross country flight, and elevation changes of 3000 feet or so. It's not just flat, boring terrain around here, it's mountains and seashores and everything in between. Yeah, it's only a difference of an inch or so on the MP limit, but again, it's a want, not a need, and electronic engine instrumentation is less expensive than separate gauges so why not? Bruno liked the idea, obviously, and I know you are all fans of Bruno!

Now you are just being silly.

Map limits don't change drastically in flight but they do change; in my last flight there were times during cruise when MCP was 23+" and other times when it was 21". More relevantly though, Vne changed dramatically, from 130 kts at departure down to 103 kts when going over a mountain at high temperatures. I would absolutely pay extra for something that makes this easier to manage. I may even write my own Android app to show the current map/Vne limits, though I don't know how to feed it OAT so that may have to be selected onscreen (simple slider).

The ideal solution would be for the Garmin PFD to be programmed to change its yellow/red IAS arc dynamically based on conditions, because it does know OAT and altitude. (Pilot would have to remember the 2200 lb thing.)

And yet the green arc ends at 110kts IAS and the poh warns against anything above unless in smooth air..

Why? Do you believe that doesn't happen?

Trying to avoid getting roped into this debate, but I believe he's implying it's nicer to have an EFIS tell you how are you are from full throttle (and when you've reached it) so that by the time your Nr is drooping, you're aware of it and making control actions based on that information. I think if the only thing alerting you to the loss of Nr is the warning horn, you're probably stuffed by then. As many have said before, the MAP gauge is sufficient for defining limits, but I'll agree with 'a(whatever the username is)' in saying that the MLI of the Cabri makes it much clearer to the pilot what your limit is and how far from it you are. My 2 cents worth; having a 0-100% gauge on a Robbie might just help the not-so-stellar pilots among us to realise when they're testing the limits of the aircraft and encourage them to calm down - especially the casual pilots who don't necessarily do all the pre-flight planning we all take for granted.

That being said, this is all a massive thread drift from the OP (a fatal crash presumably caused by TR anomalies), so I hope the 'proving people right on the internet' debate can subside to keep this thread relevant.

P.s. The Cabri is better.

Shirley somebody would be smart enough to modify the MAP gauge to have a temperature and a pressure altitude input, which moves the outer scale (0 - 100%) so that with altitude / temp increase, the 100% part of the scale moves anti-clockwise towards the needle.

And don't call me Shirley.

Sadly that would require technology available to us decades old to be put into production.

ApolloHeli - I remember an important part of my R22 conversion was demonstrating the ability to recognise and recover from overpitching (ie rasing the lever past the point of max fuel available). You can't miss the sound of the Nr decaying even before the unfeasibly loud horn goes off.

This should be a basic skill for a SE piston heli pilot.

I could add to the thread drift, or simply point out that lack of power, or the finer points of where the “flight manual limit” was on the day in question, almost certainly did not contribute to the crash in question.

Pax on a mtce test flight would seem to have contributed to the fatalities and serious injuries.
The failure seems to be atypical and as yet unexplained.

Thank you.

Cheers,
Grog

I have been following this thread and other's for some time now. and I, like other's here are interested to see the final ATSB report into what happened in flight.

Let me 1st introduce myself as an A.M.E
Several members here have already mentioned drive shaft damper bearing failure, flex plates cracked RB's etc etc. I am not an accident investigator by any means, however after several R22 and R44 rebuilds and 100 hourly inspections on R22 and R44's being operated in desert country (red dirt, mustering environments) I have come across many times over the years that there has been excessive wear associated with the C121-17 push pull tube connecting to the A120-3 Bellcrank Assembly on the TRGB, has excessive wear from dirt build up between the C121-17 Push pull tube and nylon guides within the tail cone.

The aircraft in question was only operated out of the industrial estate where the incident occurred. Never from bitumen or asphalt helipad as per the ATSB investigation. The aircraft would have spent it's life cycle ingesting dust and dirt each time it left or returned to it's home base. No doubt dust and debris was ingested into the tail cone and associated empennage for some time and probably since aircraft in question was sold in this country. I have seen wear on the C121-17 on many R22 and R44's which are based on the many cattle properties through out this country where the dirt build up between the nylon bushes has worn deep into the push pull rod and required replacement or renewed paint to be applied to effected areas.

To me, it looks as though the push pull tube has worn through which would not have been detected with a ground run and TR balance. The push pull tube has given way causing the TR to swing at an angle which resulted in complete loss of control and the TR blade to cut through the tail cone assembly resulting in the fatal incident currently under investigation.

Anyone who works on R22's or R44's which spend their lives mustering or in dirt\dust would have encounted the wear produced on the C121-17 tube from dirt build up between the nylon bushing.

IN MOST CASES I HAVE EXPERIENCED, THE PUSH PULL TUBE HAS NEEDED TO BE REMOVED TO FULLY INSPECT FOR WEAR BETWEEN THE NYLON BUSHINGS.

My reference book is the R44 IPC found here: R44 IPC - Robinson site *unable to post links until I have reached 10 posts"
65.0 - Item 8
C041-1 Damper Assembly

65.6 - Number 19
C121-17

67.90
C121-17 Push pull tube.

Anyone else able to shed some light on their experiences when removing the C121-17 on mustering choppers?

Cheers

Winfield.