FAA mandates replacement of R22 & R44 main rotorblades
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blakmax
Correct me if I'm wrong, but those -7 blades seem a poor design, stepping to a wider chord half way out towards the tip.Looks like they have designed in a stress point and asking for a crack to appear.
I always assumed a tapering section or parallel (with no steps) would be more efficient and sensible.
Correct me if I'm wrong, but those -7 blades seem a poor design, stepping to a wider chord half way out towards the tip.Looks like they have designed in a stress point and asking for a crack to appear.
I always assumed a tapering section or parallel (with no steps) would be more efficient and sensible.
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Interesting!
Thanks Chopjock
I am intrigued. The previous designs had a relatively uniform chord with the additional TE section added by inserting a metal strip behind the uniform core profile to support the face sheets.
To change the chord length would either require a much larger and thicker strip to support the face sheets (which would add significant weight and centrifugal loading for that weight) or the core profile would have to step at the change in chord. There are two ways to change the core profile: 1. Machine the core block with a step and then expand the core and hope that the machining process provided a good match with the location of the chord change, or they could machine the core in two profiles and join them with core splice adhesive. Alternatively they could make the core in three sections, one for the smaller chord, one for the larger chord and a third block machined with the trailing edge angle incorporated so that the skin is supported in the transition zone. The three segments would then be joined by core splice adhesive.
Now if they didn't get the correlation of the change in core profile correctly aligned with the change in the actual chord change, OR if they didn't actually splice the core at all at the change in chord length, then either condition would lead to undesirable local stresses which could lead to cracking of the skins. In particular if the core splice adhesive was not applied, then this is a real problem. The core transfers shear loads, caused by the blade aerodynamic loading being distributed along the blade. If there is a disconnection such as caused by an absence of core splice or poor design of the transition in core shape then all the shear loads are dumped into the skins, and that would possibly cause a rapid increase in stress in the skins and could possibly initiate fatigue problems.
Alternatively if the core plan profile doesn't match the skin profile, then there will be some unsupported skin material which could experience local buffeting and again initiate fatigue. From a production perspective it would be very difficult to machine the core to the shape of the transition zone between the two different chord lengths.
I hope our Kiwi friends can enlighten us on the presence or absence of core splice adhesive at the step in the chord and the configuration of the core at the change in chord.
Regards
Blakmax
I am intrigued. The previous designs had a relatively uniform chord with the additional TE section added by inserting a metal strip behind the uniform core profile to support the face sheets.
To change the chord length would either require a much larger and thicker strip to support the face sheets (which would add significant weight and centrifugal loading for that weight) or the core profile would have to step at the change in chord. There are two ways to change the core profile: 1. Machine the core block with a step and then expand the core and hope that the machining process provided a good match with the location of the chord change, or they could machine the core in two profiles and join them with core splice adhesive. Alternatively they could make the core in three sections, one for the smaller chord, one for the larger chord and a third block machined with the trailing edge angle incorporated so that the skin is supported in the transition zone. The three segments would then be joined by core splice adhesive.
Now if they didn't get the correlation of the change in core profile correctly aligned with the change in the actual chord change, OR if they didn't actually splice the core at all at the change in chord length, then either condition would lead to undesirable local stresses which could lead to cracking of the skins. In particular if the core splice adhesive was not applied, then this is a real problem. The core transfers shear loads, caused by the blade aerodynamic loading being distributed along the blade. If there is a disconnection such as caused by an absence of core splice or poor design of the transition in core shape then all the shear loads are dumped into the skins, and that would possibly cause a rapid increase in stress in the skins and could possibly initiate fatigue problems.
Alternatively if the core plan profile doesn't match the skin profile, then there will be some unsupported skin material which could experience local buffeting and again initiate fatigue. From a production perspective it would be very difficult to machine the core to the shape of the transition zone between the two different chord lengths.
I hope our Kiwi friends can enlighten us on the presence or absence of core splice adhesive at the step in the chord and the configuration of the core at the change in chord.
Regards
Blakmax
Last edited by blakmax; 23rd Feb 2015 at 01:16. Reason: Had a rethink see later message
Of note -
~ 1200 folks have departed for good in an R product for various reasons.
22/44 at 55/45 percent respectively.
~ 1200 folks have departed for good in an R product for various reasons.
22/44 at 55/45 percent respectively.
Interesting statistic and one I have not heard before. We often hear stats about the number of accidents per hour etc. but how many souls lost is a sobering one.
So is there similar data for other types - I know, its still meaningless without knowing the service hours and type of operations but interesting nevertheless.
On the topic, I am a UK based low time PPL(H) and recently flew a 44 in a non-eu country effectively as a student under instruction. The pre-flight checks were done by the 'instructor' and I just got in the right hand seat.
While doing a full and free check I noticed definite ripples on the underside of the blade about 18 to 24 inches from the tip. I mentioned it to the MUCH more experienced chap in the left seat and he said that somebody had hit a small branch a few days earlier but that 'the tech guys tell me its within limits'. Now I was fairly happy to accept his explanation as he is well known and considered a bit of a legend in the rotary world and also he was in the aircraft as well and 'he must know what he's doing'
However I believe that if that aircraft belonged to the outfit I normally fly with in the UK it would have been grounded and the blades condemned. Perhaps I am just too cautious, what would you guys have done?
So is there similar data for other types - I know, its still meaningless without knowing the service hours and type of operations but interesting nevertheless.
On the topic, I am a UK based low time PPL(H) and recently flew a 44 in a non-eu country effectively as a student under instruction. The pre-flight checks were done by the 'instructor' and I just got in the right hand seat.
While doing a full and free check I noticed definite ripples on the underside of the blade about 18 to 24 inches from the tip. I mentioned it to the MUCH more experienced chap in the left seat and he said that somebody had hit a small branch a few days earlier but that 'the tech guys tell me its within limits'. Now I was fairly happy to accept his explanation as he is well known and considered a bit of a legend in the rotary world and also he was in the aircraft as well and 'he must know what he's doing'
However I believe that if that aircraft belonged to the outfit I normally fly with in the UK it would have been grounded and the blades condemned. Perhaps I am just too cautious, what would you guys have done?
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Statistics RVDT, can sometimes be useful. If the time was taken to analyse the piloting skill as main contributor I believe you would not get any better or worse than many other products, except for Enstrom which until recently was exceptionally good.
I think you would also be well aware of the problems we had with cracked and broken Bell 47 grips some moons ago which claimed one life and went within minutes of claiming either two or one other, self included.
For example, one of the latest "stars" found mother earth at speed, without IFR training or instruments whilst heading in a westerly direction and the last radio transmission reported following the tail light of the preceding helicopter.
Now, the preceding machine was ten minutes ahead and travelling in an Easterly or NE direction. I know my eyesight is not that good and I guess you being an OZ and I think well experienced in Northern OZ would know what particular piece of illumination sits at an appropriate height above the western horizon about 45 minutes after sundown and could be mistaken as a R22 tail light in close proximity?
For those who live in different climes and may not see it, what we would be looking at would be Mars. Sick to the bottom of your guts reading this? I don't blame you.
There have been plenty, plenty more of those non VFR night time accidents in R22's. No doubt someone will come on here and criticise my post as being in poor taste, as they have elsewhere, but Jesus how f'n stupid do you wish to get to claim a Darwin award and tarnish the statistical reputation of an aviation product? Once again a young family was left behind and everybody is running around falling all over each other wringing their hands and wailing.
There has also been a steady increase of accidents that upon reflection are nothing other than collision with terrain in an out of control situation, usually from the Low Level operated sphere, either by plain stupidity or lack of skill because of an abysmal lack of mentoring and or useful ab-initio training.
Figures relating to catastrophic failure on the other hand are very slight, not that I am any happier as to the latest state of affairs than anyone else, in fact I agree these Robinson blade problems are and have been a massive root right from the first one, the unfortunate victim of which I had met.
I think you would also be well aware of the problems we had with cracked and broken Bell 47 grips some moons ago which claimed one life and went within minutes of claiming either two or one other, self included.
For example, one of the latest "stars" found mother earth at speed, without IFR training or instruments whilst heading in a westerly direction and the last radio transmission reported following the tail light of the preceding helicopter.
Now, the preceding machine was ten minutes ahead and travelling in an Easterly or NE direction. I know my eyesight is not that good and I guess you being an OZ and I think well experienced in Northern OZ would know what particular piece of illumination sits at an appropriate height above the western horizon about 45 minutes after sundown and could be mistaken as a R22 tail light in close proximity?
For those who live in different climes and may not see it, what we would be looking at would be Mars. Sick to the bottom of your guts reading this? I don't blame you.
There have been plenty, plenty more of those non VFR night time accidents in R22's. No doubt someone will come on here and criticise my post as being in poor taste, as they have elsewhere, but Jesus how f'n stupid do you wish to get to claim a Darwin award and tarnish the statistical reputation of an aviation product? Once again a young family was left behind and everybody is running around falling all over each other wringing their hands and wailing.
There has also been a steady increase of accidents that upon reflection are nothing other than collision with terrain in an out of control situation, usually from the Low Level operated sphere, either by plain stupidity or lack of skill because of an abysmal lack of mentoring and or useful ab-initio training.
Figures relating to catastrophic failure on the other hand are very slight, not that I am any happier as to the latest state of affairs than anyone else, in fact I agree these Robinson blade problems are and have been a massive root right from the first one, the unfortunate victim of which I had met.
Top .... I think you make a very fair point about skills . Putting the Robinson catastrophic failures to one side I think it becomes transparent that although this is the "first" helicopter for most ( due to being cheap ) .... Sadly it is not the most low time pilot friendly machine either . The reason there have been almost no fatal accidents ( I know of the sad recent one ) in the Enstrom is that it is the friendliest helicopter in the world to fly . It has no vices , you can abuse it in so many ways and it still doesn't bite . The Robinson is actually probably only safe , barring falling apart , in very experienced hands , which actually makes it far from ideal as a starter machine !!
Vmc at night for low to middle time pilots especially in the sparsely populated areas is eventually going to go wrong in my view . I just wish the powers that be would push for an IMC for night ops .
Vmc at night for low to middle time pilots especially in the sparsely populated areas is eventually going to go wrong in my view . I just wish the powers that be would push for an IMC for night ops .
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Core issues
I have had another look at the blade profile and I think it is still possible to make the blade with a uniform core profile and no joints.
Disregard the last message from me.
Blakmax
Disregard the last message from me.
Blakmax
Have talked to some engineers today and the thought is that in the next day or so the answer may be for yet another directive to inspect the blades and away you go. Personally I find that hard to believe and would not happy with that outcome. Having seen the photo in the Australian AD of the blade crack/crevasse/shifting of the tectonic plates 
It is hard to have faith in a blade in its seventh revision and I wonder how someone who has changed out dash 6 blades for 7 would feel now. If it turns out the dash 7 is toast and the dash 8 hasn't been invented, where does that leave the world fleet. We went from aluminium to stainless and back to aluminium. How could you have faith in a dash 8? None of this is good news for the helicopter industry. Interesting to see what turns up at Heliflite stand at Avalon! A 22 and a 66 I suppose.
It is hard to have faith in a blade in its seventh revision and I wonder how someone who has changed out dash 6 blades for 7 would feel now. If it turns out the dash 7 is toast and the dash 8 hasn't been invented, where does that leave the world fleet. We went from aluminium to stainless and back to aluminium. How could you have faith in a dash 8? None of this is good news for the helicopter industry. Interesting to see what turns up at Heliflite stand at Avalon! A 22 and a 66 I suppose.
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Another inspect AD would be a fudge but without it You could see Robinson struggle to stay in business. Money talks so they will fudge it and hope that no more crash whilst Robinson are told to make another better blade and guess who will end up paying for it?
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Just to repeat:
I have in my possession an email from Kurt Robinson warning me if I did not purchase a set of -2 main rotor blades before a particular date, Robinson was going to discontinue them and I would be forced to upgrade my Astro with hydraulics to use the newer stainless blades.
Soooo, I heeded his warning and paid close to US $45,000 for a new set of main rotor blades for my Astro that would not entail my having to add hydraulics.
Now, I am being told that my main rotor blades (which came with a 2200 hour or 12 calendar year limit) will have to be taken off in less than five years!
My real issue is the following:
Kurt Robinson HAD TO KNOW this AD was on the horizon, yet he didn't allow that tidbit to get in the way of him convincing me to buy a new set of aluminum blades that would shortly thereafter have their lifespan chopped in half.
After owning several Robinson helis over the last decade plus and being caught up in their multiple abject failures in main rotor blade manufacturing that has required me to replace perfectly good blades MORE THAN ONCE, this is my last go with Robinsons.
They simply cannot admit their engineering failure in being able to make a durable and dependable main rotor blade.
Robinson users can defend the company all they like, but what I've stated here is FACT.
EDIT: Since I made the above post earlier in this thread, we have seen two instances of the -7 main rotor blades FAILING in flight. We now have three separate countries all grounding the entire R44 fleet!!
If anyone here thinks Im now gonna replace my perfectly fine -2 blades with the same old crap only now labeled -7 blades, please tell Elvis and Santa I said hello.
I have in my possession an email from Kurt Robinson warning me if I did not purchase a set of -2 main rotor blades before a particular date, Robinson was going to discontinue them and I would be forced to upgrade my Astro with hydraulics to use the newer stainless blades.
Soooo, I heeded his warning and paid close to US $45,000 for a new set of main rotor blades for my Astro that would not entail my having to add hydraulics.
Now, I am being told that my main rotor blades (which came with a 2200 hour or 12 calendar year limit) will have to be taken off in less than five years!
My real issue is the following:
Kurt Robinson HAD TO KNOW this AD was on the horizon, yet he didn't allow that tidbit to get in the way of him convincing me to buy a new set of aluminum blades that would shortly thereafter have their lifespan chopped in half.
After owning several Robinson helis over the last decade plus and being caught up in their multiple abject failures in main rotor blade manufacturing that has required me to replace perfectly good blades MORE THAN ONCE, this is my last go with Robinsons.
They simply cannot admit their engineering failure in being able to make a durable and dependable main rotor blade.
Robinson users can defend the company all they like, but what I've stated here is FACT.
EDIT: Since I made the above post earlier in this thread, we have seen two instances of the -7 main rotor blades FAILING in flight. We now have three separate countries all grounding the entire R44 fleet!!
If anyone here thinks Im now gonna replace my perfectly fine -2 blades with the same old crap only now labeled -7 blades, please tell Elvis and Santa I said hello.
Helilog56 said : "Arm chair quarter backing from an RC enthusiast.....this forum just keeps getting better...."
I just have to say something here, because I find this somewhat amusing...don't be so quick to knock the RC crowd now...
Here is the "acid test" in terms of the RC crowd VS full-scale pilots...
I will bet you my bottom dollar that if you took an average RC pilot and put him in (say) a full-scale 172 in an emergency situation (where the real pilot was suddenly incapacitated)...chances are pretty good he would get back on the ground again, having never flown before - his chances would not be "nil".
The reverse however, is not true...(put a full-scale 172 pilot behind the sticks of an RC transmitter with a model 172 up in the air for the first time and tell him to put it down again safely), and he will create matchsticks in short order...guaranteed....so respect them RC pilots...
I have seen it time-and-again, where a gung-ho full-scale pilot comes to fly a "toy" (RC) plane / chopper for the first time, and has the attitude it should be a doddle, since, after all (he is a FULL SCALE pilot), and, it all ends in tears within a couple of minutes with a broken model and a severely dented ego...
I just have to say something here, because I find this somewhat amusing...don't be so quick to knock the RC crowd now...
Here is the "acid test" in terms of the RC crowd VS full-scale pilots...
I will bet you my bottom dollar that if you took an average RC pilot and put him in (say) a full-scale 172 in an emergency situation (where the real pilot was suddenly incapacitated)...chances are pretty good he would get back on the ground again, having never flown before - his chances would not be "nil".
The reverse however, is not true...(put a full-scale 172 pilot behind the sticks of an RC transmitter with a model 172 up in the air for the first time and tell him to put it down again safely), and he will create matchsticks in short order...guaranteed....so respect them RC pilots...
I have seen it time-and-again, where a gung-ho full-scale pilot comes to fly a "toy" (RC) plane / chopper for the first time, and has the attitude it should be a doddle, since, after all (he is a FULL SCALE pilot), and, it all ends in tears within a couple of minutes with a broken model and a severely dented ego...
Namaste topendtorque
Very intelgent & typical comment from a blinded Robi worshiper. That is about all you guys can muster-up as you have no real valid arguments pro the Crapinson's other than slag off at those who offer real experiences with Fank made garbage
Happy landings
Very intelgent & typical comment from a blinded Robi worshiper. That is about all you guys can muster-up as you have no real valid arguments pro the Crapinson's other than slag off at those who offer real experiences with Fank made garbage
Happy landings
Originally Posted by TET
Figures relating to catastrophic failure on the other hand are very slight, not that I am any happier as to the latest state of affairs than anyone else, in fact I agree these Robinson blade problems are and have been a massive root right from the first one, the unfortunate victim of which I had met.
One way this turns out is the beginning of the end for Robinson.
Another way is that it is addressed well and confidence is restored.
We shall see.
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Originally Posted by as350nut
I wonder how someone who has changed out dash 6 blades for 7 would feel now
I fly in a French territory, no AD from EASA so far but we decided to ground our 44 for the duration.
RHC have issued a Safety Alert
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Robinson issue R44 Safety Alert
http://www.robinsonhelicopter.com/se...fety_alert.pdf
Looks like the advice is to check and fly. Not sure I like the idea of getting airborne under a pair of dash 7 blades for the time being.
Looks like the advice is to check and fly. Not sure I like the idea of getting airborne under a pair of dash 7 blades for the time being.
Last edited by Egg whisk driver; 23rd Feb 2015 at 20:04.