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R44 crashed Alps

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R44 crashed Alps

Old 31st Oct 2020, 14:58
  #21 (permalink)  
 
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Originally Posted by Robbiee View Post
Congratulations! You've just won the "Butthurt over Robinsons" comment of the week!
Hahahahahaha! That literally made me laugh out loud!

On a more serious note, Robinsons are fine machines and clearly capable of being operated in mountainous terrain safely. And, yes, you do that in part by paying attention your speed in accordance with the POH and applicable Robinson Safety Notices, BR. My personal minimums tend more towards gust 25 for mountainous terrain, and I do try to respect the terrain in appropriate ways. But don't take my word for it. There are plenty of schools who teach mountain and high altitude operations in Robinsons. Youtube is full of those videos. You don't see Robinsons dropping from the sky like flies.

TT hit the nail squarely on the head: "Low cost helicopter meets low experience pilot flying in a low discipline environment." That statement could probably preface 90% of all Robinson accident reports.

@Torquetalk please confirm that by "low cost" your meant "more easily accessible and affordable" as opposed to "poorly designed or incapable"?


eta: this topic and this one are so similar you could probably combine them.

Last edited by aa777888; 31st Oct 2020 at 14:59. Reason: added a thought
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Old 31st Oct 2020, 16:01
  #22 (permalink)  
 
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Originally Posted by Arnie Madsen View Post
I am not anti-Robinson but we must acknowledge that very light blades are more sensitive to turbulence & mast bumping.
Heavy blades retain their plane of rotation long enough to handle sudden strong gusts.
But they require extra strength (heavy) laminations & spar at the root end to handle bending loads at the root (blade coning)

Frank came up with a good solution to save ounces and pounds in the rotor system
By incorporating coning hinges at the root which relieved any coning stress
Thus he could build very light blades .... which had the additional benefits of lower centrifugal force on the hub and feather bearings which meant he could build a lighter head.

Early blade de-laminations were the first red flag , but were attributed to outsourced blade manufacturing errors
Then came the numerous unexplained rotor incursions into the cabin or boom. A big red flag ... not to mention further de-laminations through the years

Easy for me to say ... but if he (stubborn frank) had halted production , built a blade similar to the H269 , strengthened the hub to take the extra loads , the problem would have been solved.

Of course those several pounds of weight would have reduced payload .... but extra pitch along with extra power from the de-rated engine should solve that ..... working the Lycoming a bit harder would likely reduce TBO from 2200 hrs to 1800 hrs which is still excellent for piston helicopters.

I am also suspicious of having 3 hinge points on a 2 blade rotor .... if a split second disturbance caused one blade to pivot on a coning hinge it would immediately put everything out of phase and would self-destruct.
There ... you just hit the nail firmly on the head. In 25 years plus of following Robinson rotor issues this seems to be the view of a number of the worlds experts. The numerous unexplained Robinson rotor divergence issues are unique but so is the rotor head design with a teeter and 2 coning hinges. I’m sure this particular accident was due to being out in the wrong kind of weather and the result would have been the same regardless of what type of light helicopter was being flown. More frequent checks on the condition of the coning bolts and closely monitoring preload (resistance to movement) should be introduced. A Robinson operator told a story on here (PPrune) a couple of years ago of finding the broken off end of his coning bolt during a pre flight check in the hangar (a little alarming I know). I’m not a Robinson hater in any shape or form and would be willing to assist in any way I could reducing or solving this issue.


I am also suspicious of having 3 hinge points on a 2 blade rotor .... if a split second disturbance caused one blade to pivot on a coning hinge it would immediately put everything out of phase and would self-destruct.



Last edited by TTSN; 31st Oct 2020 at 18:11.
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Old 31st Oct 2020, 17:16
  #23 (permalink)  
 
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You know, there used to be some cars whose engine would overheat when you drove them uphill with the air conditioning on. Some would whine that this was a design flaw and swear to never drive one of those cars,...others would just turn off the air conditioning, drive over the hill, then turn it back on.

I guess everyone just handles limitations in different ways.
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Old 31st Oct 2020, 21:41
  #24 (permalink)  
 
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Torquetalk The Bells have stronger components which may help in turbulent situations but you cannot tell me that using a Robbo in the Alps is not the wrong tool for the job. Also I dont think low experience of the pilot has anything to do with it, look at the accidents that have occurred in New Zealand over the years.


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Old 31st Oct 2020, 22:14
  #25 (permalink)  
 
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R44's are flown daily around the Alps without issue, because the pilots and companies that operate them do so safely by knowing the limitations of both the aircraft and the pilots. I think many of the posters trying to suggest that they are unsuitable for the environment simply haven't been here and don't have a clear idea of the helicopter operations in & around the Alps.

Although we have no idea what the cause of this incident was (and my personal hunch is that must bumping is unlikely to have been involved), the crash of G-RAMY on the Isle of Man in 2015 is a clear example that any semi-rigid/teetering rotor system is susceptible to mast bumping so we can all agree 3+ blades are best .

Despite the satisfaction of pointing out the numerous shortcomings of the Robinson design, I think posts on this thread would be more constructive and worth everyone's while if they were related to the incident at hand and on the possible causes. Maybe this was whiteout/loss of references? Could icing have brought them down? Maybe the wind did cause the crash with a sudden downdraft when they were close to obstacles/ground? Hopefully there will be some lessons learned out of this one, and it's not just another repeat of last episode on 'R44 wreckage found in challenging terrain.'
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Old 1st Nov 2020, 01:51
  #26 (permalink)  
 
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Exactly. Another question might be how those bloody things were ever certified in the first place. Any other mass produced aircraft that doesnít seen to be able to handle 35 knots?
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Old 1st Nov 2020, 01:59
  #27 (permalink)  
 
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Originally Posted by rottenjohn View Post
Exactly. Another question might be how those bloody things were ever certified in the first place. Any other mass produced aircraft that doesnít seen to be able to handle 35 knots?
I have flown an R22 in 35kts.

,...they can handle it just fine.
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Old 1st Nov 2020, 09:07
  #28 (permalink)  
 
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Originally Posted by aa777888 View Post
@Torquetalk please confirm that by "low cost" your meant "more easily accessible and affordable" as opposed to "poorly designed or incapable"
aa777888, I was simply talking about cost. The Robinsons are what they are and perfectly capable aircraft if flown properly.

The R22 is very light and there is very little energy in the main rotor and little authority margin in the tail rotor. ItĎs a bit like a metal gnat. But gnats bounce of things harmlessly when they hit them, R22s donĎt.

The R44 is as different as it is similar. There is much more energy in the main rotor. R44s accidents are often performance related, with pilots clearly flying into situations which are just accidents waiting to happen. Many will have done a lot of autorotation training, but generally neglected the skills and knowledge needed to fly in performance limited situations. Exactly the kind of situations they are likely to find themselves in because it is a four seat helicopter, whilst training is generally done with 2 on board...

I have also flown an R22 in high winds, but I think you need to be very careful about when and where and why you would do this. Also had LTE through sheer niavety in an R22. Might have happened in other light types, but I reached and passed a limit very quickly in that case.

One of our fellow ppruners was killed ferrying an R22 back from Spain some years ago, encoutering CAT on the lee side of the Pyrenees in high winds causing the aircraft to break up mid-air. They clearly didnít see that coming.

But Robinsons are not reasponsible for bad decsions to fly. At least one of the pilots involved was quite experienced in that case, but clearly failed to anticipate the danger. A counter example would be the Gazelle accident in NE England on a high wind day some years ago. In that case, it also involved a pilot flying in the lee of hills on a high wind day and completely lacking the skills and experience to be in or cope with the situation he put himself in. Nothing to do with the aircraft, he was just too cocky. Sadly not around to learn the lesson.

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Old 1st Nov 2020, 09:16
  #29 (permalink)  
 
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Good for you, so have I. However this is about the R44.
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Old 1st Nov 2020, 09:28
  #30 (permalink)  
 
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Not entirely John, the discussion has also encompassed criticism of Robinsons in general as being unsuitable for mountain flying by design and citing design as the main problem with Robinsons, as opposed to how they are sometimes flown. This discussion applies to all Robbies insofar as it‘s about people either flying an inappropriate design or poor airmanship being involved in many Robbie accidents.

I‘m in the poor airmanship camp.
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Old 1st Nov 2020, 11:28
  #31 (permalink)  
 
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Originally Posted by ApolloHeli View Post
R44's are flown daily around the Alps without issue, because the pilots and companies that operate them do so safely by knowing the limitations of both the aircraft and the pilots. I think many of the posters trying to suggest that they are unsuitable for the environment simply haven't been here and don't have a clear idea of the helicopter operations in & around the Alps.

Although we have no idea what the cause of this incident was (and my personal hunch is that must bumping is unlikely to have been involved), the crash of G-RAMY on the Isle of Man in 2015 is a clear example that any semi-rigid/teetering rotor system is susceptible to mast bumping so we can all agree 3+ blades are best .

Despite the satisfaction of pointing out the numerous shortcomings of the Robinson design, I think posts on this thread would be more constructive and worth everyone's while if they were related to the incident at hand and on the possible causes. Maybe this was whiteout/loss of references? Could icing have brought them down? Maybe the wind did cause the crash with a sudden downdraft when they were close to obstacles/ground? Hopefully there will be some lessons learned out of this one, and it's not just another repeat of last episode on 'R44 wreckage found in challenging terrain.'
Outstanding post, well said!
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Old 1st Nov 2020, 11:57
  #32 (permalink)  
 
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Originally Posted by Torquetalk View Post
aa777888, I was simply talking about cost. The Robinsons are what they are and perfectly capable aircraft if flown properly.
Thank you.

The R22 is very light and there is very little energy in the main rotor and little authority margin in the tail rotor.
I disagree with the latter half of that statement. There is plenty of tail rotor authority in the 22, and the same for the 44 and 66. They all will work fine in a 30KN breeze. I'm told by other pilots they work fine in a 40KN breeze but that much wind is beyond my personal limits right now. Obviously one must fly carefully in such conditions.

The R44 is as different as it is similar. There is much more energy in the main rotor. R44s accidents are often performance related, with pilots clearly flying into situations which are just accidents waiting to happen. Many will have done a lot of autorotation training, but generally neglected the skills and knowledge needed to fly in performance limited situations. Exactly the kind of situations they are likely to find themselves in because it is a four seat helicopter, whilst training is generally done with 2 on board...
A very good point. Similar to that being discussed in the other R44 crash thread. All that performance margin helps you survive training. Helps you right up until that very first flight with your newly minted pilot certificate and all the seats filled. I am very happy that the school I used intentionally included lessons at max. gross weight. The extra pressure and cat calls from the other students in the rear are also good training. Made another student airsick once as when it was my turn in the front the instructor had me performing "enhanced training in autorotation procedures", as SFAR 73 puts it. That was pretty funny!

I have also flown an R22 in high winds, but I think you need to be very careful about when and where and why you would do this. Also had LTE through sheer niavety in an R22. Might have happened in other light types, but I reached and passed a limit very quickly in that case.
What were the conditions when you had your "LTE" experience? Not to create a major thread drift, but a paper presented at the EASA Rotorcraft & VTOL Symposium 2019 entitled "The Myth of Losing Tail Rotor Effectiveness" makes some compelling arguments that there is no such thing as LTE and it is hard to refute the research. I have attached it to this post.

One of our fellow ppruners was killed ferrying an R22 back from Spain some years ago, encoutering CAT on the lee side of the Pyrenees in high winds causing the aircraft to break up mid-air. They clearly didnít see that coming.

But Robinsons are not reasponsible for bad decsions to fly. At least one of the pilots involved was quite experienced in that case, but clearly failed to anticipate the danger. A counter example would be the Gazelle accident in NE England on a high wind day some years ago. In that case, it also involved a pilot flying in the lee of hills on a high wind day and completely lacking the skills and experience to be in or cope with the situation he put himself in. Nothing to do with the aircraft, he was just too cocky. Sadly not around to learn the lesson.
Thanks for another excellent post!
Attached Files
File Type: pdf
ERF2019 0017.pdf (1.20 MB, 112 views)
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Old 1st Nov 2020, 15:35
  #33 (permalink)  
 
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Originally Posted by aa777888 View Post

A very good point. Similar to that being discussed in the other R44 crash thread. All that performance margin helps you survive training. Helps you right up until that very first flight with your newly minted pilot certificate and all the seats filled. I am very happy that the school I used intentionally included lessons at max. gross weight. The extra pressure and cat calls from the other students in the rear are also good training. Made another student airsick once as when it was my turn in the front the instructor had me performing "enhanced training in autorotation procedures", as SFAR 73 puts it. That was pretty funny!
This seems to be more of an issue with schools who use the R44 exclusively. If you did your training in an R22 you'd be intimately familiar with flying at max gross weight and not being able to HOGE without busting power limits. An R44 with four on board is just an R22 with two.
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Old 1st Nov 2020, 16:19
  #34 (permalink)  
 
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That is a very good paper aa777888
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Old 1st Nov 2020, 19:39
  #35 (permalink)  
 
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Everyone knows all 2 blade systems can experience mast bumping. Nothing new there.
But the R series has more than double the amount of others.
This was determined by an exhaustive study by NTSB and a high level aviation university
It was a true apple to apple comparison , nothing to do with number of machines sold or pilot experience.

NTSB nomenclature call it "loss of rotor control" or "blade incursion into cabin or boom"
And of course all of them also show mast bumping and broken droop tusks.

But my question has always been ..... what caused the initial loss of rotor control which caused all the other bumping-incursion damage ???

We all know about Zero-G ..... strong gusts ... updrafts ..... downdrafts ... equally applicable to all 2 blade systems .... with some advantage to heavy blades .... but can we blame the R failures on light blades alone ??? .... personally I dont think so.

I have always been suspicious of the 3 hinge points in the R system . It works as advertised and is a clever way to eliminate stress and bending at the blade roots. And at overhaul time mechanics will see wear at the main teeter pin and bushings (normal) and no wear at the coning hinge pins (good)

This indicates the coning hinges will only compensate for coning and pretty well remain fixed (no continuous movement-flapping in flight.) .... just as it was designed to do.

But what is to say that a rare aerodynamic situation could not occur that causes one blade to flap up on its coning hinge .... it would put the rotor system out of balance , plus without a lead-lag hinge a lot of stress on the (un-reinforced) blade root.

Other 2 blade rotor systems have a rigid head and are stiff and reinforced at the first few feet of each blade , thus the disturbance would be dampened and partly transferred to the other blade.

The R system is like a limp noodle by comparison with those 3 hinge points. And yes .... I realize centrifugal force tries to keep the coning hinges "stiff" but maybe a split second disturbance could alter that

I could be creating a monster that does not exist .... just trying to reason out why the R rotor experiences almost double the rotor incursions of other 2-bladers when all other circumstances are equal. (apples to apples )
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Old 1st Nov 2020, 20:02
  #36 (permalink)  
 
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Originally Posted by TTSN View Post
There ... you just hit the nail firmly on the head. In 25 years plus of following Robinson rotor issues this seems to be the view of a number of the worlds experts. The numerous unexplained Robinson rotor divergence issues are unique but so is the rotor head design with a teeter and 2 coning hinges. Iím sure this particular accident was due to being out in the wrong kind of weather and the result would have been the same regardless of what type of light helicopter was being flown. More frequent checks on the condition of the coning bolts and closely monitoring preload (resistance to movement) should be introduced. A Robinson operator told a story on here (PPrune) a couple of years ago of finding the broken off end of his coning bolt during a pre flight check in the hangar (a little alarming I know). Iím not a Robinson hater in any shape or form and would be willing to assist in any way I could reducing or solving this issue.


I am also suspicious of having 3 hinge points on a 2 blade rotor .... if a split second disturbance caused one blade to pivot on a coning hinge it would immediately put everything out of phase and would self-destruct.
Too add to that there is another unusual thing about the R rotor head.

ALL OTHER 2-blade systems connect the swash plate linkage to the blade pitch arm exactly at the teeter hinge position.

That way pitch is never altered when the rotor teeters, Pretty much an industry standard .

HOWEVER in the R system the pitch link is offset of main teeter point.

I could never wrap my head around how they get that to work




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Old 1st Nov 2020, 20:21
  #37 (permalink)  
 
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Originally Posted by [email protected] View Post
That is a very good paper aa777888
@crab thanks! There's also a Youtube video, but I found it superfluous after reading the paper. I just hope if the day ever comes when I let the shit get all spinny that I have the presence of mind to put the boot in and keep it there properly!

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Old 1st Nov 2020, 21:20
  #38 (permalink)  
 
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And that is why there are a lot of Robbie accidents, esp R44: Low cost helicopter meets low experience pilot flying in a low discipline environment.
Every pilot has started to fly without experience. I think that it's not about experience, I think it's about discipline. I do know my limits, they depend on my experience on type, my recency, my overall experience, fatigue, stress etc.
If you know your limits and only fly missions within your personal flying envelope, you're professional
If you want to fly out of your personal flying envelope you are taking chances.
Experience doesn't change that. Experience expands your personal flying envelope but does not immunise you against accidents.
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Old 1st Nov 2020, 22:17
  #39 (permalink)  
 
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Originally Posted by Arnie Madsen View Post
Too add to that there is another unusual thing about the R rotor head.

ALL OTHER 2-blade systems connect the swash plate linkage to the blade pitch arm exactly at the teeter hinge position.

That way pitch is never altered when the rotor teeters, Pretty much an industry standard .

HOWEVER in the R system the pitch link is offset of main teeter point.

I could never wrap my head around how they get that to work




Arnie,
We use the offset pitch link system on model helicopters. It adds in negative feedback to the blade during gusty conditions. Imagine advancing blade flaps up but the pushrod from the swash plate holds the grip where it is, the result is the blade introduces momentary less pitch during the flapping (up) event and automatically twists the blade back down again at the same time. This happens for both teetering and flapping events when the pitch link is offset in this manner.

Last edited by chopjock; 1st Nov 2020 at 22:32.
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Old 1st Nov 2020, 22:57
  #40 (permalink)  
 
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Originally Posted by aa777888 View Post
@crab thanks! There's also a Youtube video, but I found it superfluous after reading the paper. I just hope if the day ever comes when I let the shit get all spinny that I have the presence of mind to put the boot in and keep it there properly!

https://youtu.be/MGC0jeDUD9Q
That video seemed less about disproving the existence of LTE and more about the pilots just not putting in enough left pedal to stop it. I think?,..I was having trouble following him.

Anyway, I remember once during my commercial training back in '06, while in a hover the instructor jammed in the right pedal and I was to react by chopping the throttle. I did, the yaw stopped and we set down.

I don't recall this guy mentioning that as an option?
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