Fatal Crash Broome 4th July 2020
It looks like the helicopter hit on its right side while yawing to the left, yet the Robinson rotor system as viewed from above rotates counter-clockwise (as do most American designs), which upon loss of tail rotor authority would induce a yaw to the right. Or am I missing something again? Was the tail rotor drive train damage pre or post impact?
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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.
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Grog
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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.
pistons rarely run out of pedal, torque isn’t in great supply.
they do regularly run out of horses tho.
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.
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.
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.
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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).
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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
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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
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.
Yes the flex plate is visible, but that is just the shear point when the rest of the tail departed the scene.
Are you qualified to fly a helicopter?
Is English your first language?
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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.
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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?
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.
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.