R66 crash in Wikieup, Arizona, U.S.A., kills 2
... few can get it badly enough to cut off the tail boom or skids with the frequency of that particular manufacturer.
https://sites.google.com/site/mthomp...telegramseries
Goodgrief - experiencing mast bumping due to aggressive handling when NOE (which was the main problem in the US military) is not the same as just encountering turbulence or slightly exceeding VNE in a robbie.
Lonewolf - you don't need a vigorous push over to experience it - any unloading of the G, even an entry to auto without aft cyclic to load the disc - can cause it.
As G is reduced, the only thing producing thrust relative to the airframe is the TR which produces yaw and roll that, if there is any untoward movement of the cyclic, will usually cause the MR to chop off the tail. In extreme cases the strain can demolish the pitch change arms as well resulting in even more extreme rotor strikes (like the front of the skids in one fairly recent crash)
Lonewolf - you don't need a vigorous push over to experience it - any unloading of the G, even an entry to auto without aft cyclic to load the disc - can cause it.
As G is reduced, the only thing producing thrust relative to the airframe is the TR which produces yaw and roll that, if there is any untoward movement of the cyclic, will usually cause the MR to chop off the tail. In extreme cases the strain can demolish the pitch change arms as well resulting in even more extreme rotor strikes (like the front of the skids in one fairly recent crash)
@GoodGrief: in the 32 years since the article you cited came out, the semi rigid, underslung, teetering rotorhead on the Jet Ranger has not caused a rash of deaths due to mast bumping. (That design is similar to that of the Huey). The Navy's still flying them at Whiting field (though there have seen better days).
Plenty of two bladed Hueys and Cobras were operated safely and effectively for the 30+ years since the falling firmament articles linked. Heck, they are still being flown, the Air Force with a TH version, even though the Marines are replacing them nowadays with the newer, 4-bladed UH-1Y (Venom) and AH-1Z (Viper) that use bearing-less rotors.
I realize that this thread is about Robinsons, but just thought that I'd report to you that the sky hasn't fallen even though some helicopters now and again fall out of the sky. (Not to mention all of the 212's that have been successfully operating the world over ... )
Some flying basics usually help us operate our aircraft within limits:
You don't pull nine G's in a Cessna
You don't unload the head on a Huey.
Plenty of two bladed Hueys and Cobras were operated safely and effectively for the 30+ years since the falling firmament articles linked. Heck, they are still being flown, the Air Force with a TH version, even though the Marines are replacing them nowadays with the newer, 4-bladed UH-1Y (Venom) and AH-1Z (Viper) that use bearing-less rotors.
I realize that this thread is about Robinsons, but just thought that I'd report to you that the sky hasn't fallen even though some helicopters now and again fall out of the sky. (Not to mention all of the 212's that have been successfully operating the world over ... )
Some flying basics usually help us operate our aircraft within limits:
You don't pull nine G's in a Cessna
You don't unload the head on a Huey.
@GoodGrief: in the 32 years since the article you cited came out, the semi rigid, underslung, teetering rotorhead on the Jet Ranger has not caused a rash of deaths due to mast bumping. (That design is similar to that of the Huey). The Navy's still flying them at Whiting field (though there have seen better days).
I guess it has got a lot to do with sensitivity of the controls, Rotor inertia and margins.
All these seem to be much more benign in the Bells than in the Robbies. Flying into light/moderate turbulence at 80% vne probably won't let you arrive vertically and nose down without the big fan on top in the Bells. In the Robbies I wouldn't bet my Life on that.
I'm not a test pilot or anything, but I have a decent amount of time in 206s and R44s. I only flew an R66 once, two on board full fuel. It immediately occurred to me that it felt very very light, as if the disc was barely loaded, and I made a comment to the owner (who was the passenger) about it.
It reminded me of a lightly loaded R44 with one on board, quarter tanks. And I had gotten into a low G event, with the whole 90 degree right roll and everything, a few years prior in one of those. I had flown it into a mountain wake in Tasmania after dropping some hikers off in the hills.
The difference is of course that the R66 has another 15 or 20kts on such an R44, which makes it scarier to me. A Jet Ranger, at least going by feel, is nothing like it at all.
Just my 2 cents.
It reminded me of a lightly loaded R44 with one on board, quarter tanks. And I had gotten into a low G event, with the whole 90 degree right roll and everything, a few years prior in one of those. I had flown it into a mountain wake in Tasmania after dropping some hikers off in the hills.
The difference is of course that the R66 has another 15 or 20kts on such an R44, which makes it scarier to me. A Jet Ranger, at least going by feel, is nothing like it at all.
Just my 2 cents.
In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.
Yes, until you get the rotor pulling the fuselage with positive G, you have little or no control power and are therefore unable to alter the fuselage attitude - so moving the cyclic first will often make things worse.
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WARNING CRAB
10 hours of flying one before you crashed it and now you don't like it.
and now you are giving advice and the benefit of your suspect PoF on it
you are becoming a danger
10 hours of flying one before you crashed it and now you don't like it.
and now you are giving advice and the benefit of your suspect PoF on it
you are becoming a danger
Last edited by AnFI; 14th Jul 2016 at 05:59.
AnFI - 13 hours actually
I was taught to fly it by a very experienced mil instructor with thousands of hours R22 as well - all the safety issues were well known and discussed at length.
A year or so after I last flew a robbie (early 1990s), the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!
Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?
No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters.
I was taught to fly it by a very experienced mil instructor with thousands of hours R22 as well - all the safety issues were well known and discussed at length.A year or so after I last flew a robbie (early 1990s), the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!
Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?
No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters.
Regarding post #27. This comes as a surprise to me. I thought a low G recovery technique initial action would be application of aft cyclic. Not that I have ever experienced low G in a 206 or 212, but if I did I suspect my reaction would be aft cyclic.
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the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!
From my understanding you cannot get into a low g situation (fuselage roll) entering autorotations.
Don't want to cause a bun fight. As I see the issue being discussed, the head can be unloaded (or at least partially unloaded) by two distinctly different stimuli:
control movements
external stimuli in the forms of turbulent air / down drafts / (up drafts?).
My question might warrant a two part answer, one for each way that the head got unloaded in the first place, though my initial question was about the turbulence kind.
control movements
external stimuli in the forms of turbulent air / down drafts / (up drafts?).
My question might warrant a two part answer, one for each way that the head got unloaded in the first place, though my initial question was about the turbulence kind.
OK, low G is a bit of a variable term ranging from 0.99 G to zero G and the answer to recovery depends on the severity (ie the closer to zero) you are.
At zero G in a teetering head helicopter, you have no control power (ie how much you have to move the cyclic to affect the attitude of the fuselage). You can wave the cyclic around as much as you like but it won't affect the attitude of the fuselage.
At zero G you have no cyclic control power so therefore aft cyclic won't be effective and can make things worse (ie chopping off the tail) - the only thing that will save you is to restore positive G and that would have to be with the collective.
At 0.99 G you have a very small reduction (probably imperceptible) in control power so aft cyclic will immediately (if you have any forward speed) restore normal operation.
There is a big sliding scale between those bookends of performance - the lower the G, the lower the control power and somewhere (I don't know exactly) there will come a point where the control power is sufficiently low to render aft cyclic ineffective in restoring G (and therefore control power).
You don't have a G meter in the cockpit so you can only use seat of the pants to assess any apparent reduction in G. You can feel quite clearly a change from 1.0 to 0.5 G and zero is very floaty indeed.
It seems that Bells cope better with reduced G than Robinsons - it may have a lot to do with rotor inertia, or the extra stability provided by the additional features of the rotor head that aren't on the robbies.
Whatever the reason, any reduction in positive G should be avoided (whether through turbulence, exceeding VNE, poor entry to auto) in a Robbie and zero G should be avoided at all costs in any teetering head helicopter.
Soave pilot - I would have to do a search on the AAIB but that is what I remember (it was about 20 years ago) if you lower the lever quickly and push forward with the cyclic (the sort of reaction a FW pilot converting to RW might have to a stall - I have seen this with FW friends) - you will get a reduction in G - how much depends on the rate of application and displacement of the controls.
If you pull up and then put in the same control inputs, you can easily get to zero G ask any military pilot who has bunted a helo in order to scare the troops in the back.
Lonewolf - if you hit a big updraft in the cruise, the natural reaction is to lower the lever to maintain height - if that updraft has caused the nose to pitch up slightly you may well inadvertently push forward on the cyclic as well.
At zero G in a teetering head helicopter, you have no control power (ie how much you have to move the cyclic to affect the attitude of the fuselage). You can wave the cyclic around as much as you like but it won't affect the attitude of the fuselage.
At zero G you have no cyclic control power so therefore aft cyclic won't be effective and can make things worse (ie chopping off the tail) - the only thing that will save you is to restore positive G and that would have to be with the collective.
At 0.99 G you have a very small reduction (probably imperceptible) in control power so aft cyclic will immediately (if you have any forward speed) restore normal operation.
There is a big sliding scale between those bookends of performance - the lower the G, the lower the control power and somewhere (I don't know exactly) there will come a point where the control power is sufficiently low to render aft cyclic ineffective in restoring G (and therefore control power).
You don't have a G meter in the cockpit so you can only use seat of the pants to assess any apparent reduction in G. You can feel quite clearly a change from 1.0 to 0.5 G and zero is very floaty indeed.
It seems that Bells cope better with reduced G than Robinsons - it may have a lot to do with rotor inertia, or the extra stability provided by the additional features of the rotor head that aren't on the robbies.
Whatever the reason, any reduction in positive G should be avoided (whether through turbulence, exceeding VNE, poor entry to auto) in a Robbie and zero G should be avoided at all costs in any teetering head helicopter.
Soave pilot - I would have to do a search on the AAIB but that is what I remember (it was about 20 years ago) if you lower the lever quickly and push forward with the cyclic (the sort of reaction a FW pilot converting to RW might have to a stall - I have seen this with FW friends) - you will get a reduction in G - how much depends on the rate of application and displacement of the controls.
If you pull up and then put in the same control inputs, you can easily get to zero G ask any military pilot who has bunted a helo in order to scare the troops in the back.
Lonewolf - if you hit a big updraft in the cruise, the natural reaction is to lower the lever to maintain height - if that updraft has caused the nose to pitch up slightly you may well inadvertently push forward on the cyclic as well.
Sorry if this has been posted before...
UH1 and AH1 specific, mainly focused on push-overs as the source of mast bumping.
https://www.youtube.com/watch?v=nm8iV_uiBsI
Couple of interesting points in the context of our discussion - 0.5G as the number to stay above, and recovery is gentle aft cyclic followed by left cyclic once disc is loaded. No mention of collective whatsoever.
IIRC the Robinson standard recovery procedure is the same - immediate but gentle aft cyclic followed by left cyclic once the disc has loaded.
UH1 and AH1 specific, mainly focused on push-overs as the source of mast bumping.
https://www.youtube.com/watch?v=nm8iV_uiBsI
Couple of interesting points in the context of our discussion - 0.5G as the number to stay above, and recovery is gentle aft cyclic followed by left cyclic once disc is loaded. No mention of collective whatsoever.
IIRC the Robinson standard recovery procedure is the same - immediate but gentle aft cyclic followed by left cyclic once the disc has loaded.
'The transmission, mast, and second main rotor blade separated as a unit'
Your arguing the wrong point. If it was mast bumping the blades would no longer be attached to the transmission, i'd put money on it being a blade failure at the same place we saw on the 44s last year.
Your arguing the wrong point. If it was mast bumping the blades would no longer be attached to the transmission, i'd put money on it being a blade failure at the same place we saw on the 44s last year.
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At the risk of getting involved in yet another Robbie bashing exercise, I make the following comments - as these may help someone.
I flew the first 66 in Australia, within a week of it being in Aus. Obtained one of the first endorsements for it. 5 years ago ? I have flown 3 machines on / off since then.
First thing I noticed, like others, is that when 2 up & low fuel it it feels very light. Rule number one, keep the disk loaded (thanks to many high hour pilots that told me this 10 or so years ago when I started flying helis - about ALL machines).
Second thing, the 66 is really powerful (3/4 fuel, 5 up, confined area, 30 degrees, up, up and away) and fast. 60% torque, 130 knot cruise.
One of my good mates has around 1,000 hours on one now, and we both AGREE - never fly the 66 "light". Fill it up with fuel, people, golf sticks, beer, or whatever else you can find.
Keep that disk loaded, and do not fly it at 130 knots, by yourself, in the mountains.
The 44 is quite different, after all it has that big lump of metal (the motor) in it all the time !
I hope that helps.
Arrrj
PS _ as someone else said, 2 blade helis have flown a "few" hours over the last 40 years or so !
I flew the first 66 in Australia, within a week of it being in Aus. Obtained one of the first endorsements for it. 5 years ago ? I have flown 3 machines on / off since then.
First thing I noticed, like others, is that when 2 up & low fuel it it feels very light. Rule number one, keep the disk loaded (thanks to many high hour pilots that told me this 10 or so years ago when I started flying helis - about ALL machines).
Second thing, the 66 is really powerful (3/4 fuel, 5 up, confined area, 30 degrees, up, up and away) and fast. 60% torque, 130 knot cruise.
One of my good mates has around 1,000 hours on one now, and we both AGREE - never fly the 66 "light". Fill it up with fuel, people, golf sticks, beer, or whatever else you can find.
Keep that disk loaded, and do not fly it at 130 knots, by yourself, in the mountains.
The 44 is quite different, after all it has that big lump of metal (the motor) in it all the time !
I hope that helps.
Arrrj
PS _ as someone else said, 2 blade helis have flown a "few" hours over the last 40 years or so !
Quote:
In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.
In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.
In saying all that, I have experienced a roll in an R22 once (out of approx 400+ hrs Robinson time, mostly 44 but sprinkled with 22 and 66 time). It happened so quick that i was at 50-60 degrees before I could think about responding. Luckily my hand stayed still and did not correct the roll and we sort of swung out of it. From that point I decided that I probably dont have quick enough reactions to fix the problem after the roll, so decided that I would just slow down and/or not fly on really windy days in the Robbies.
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Crab this is an absolute disgrace
"Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?
No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters. "
You ask the question. The answer is actually YES YOU ARE WRONG
So your own answer of "NO" and the susequent acusation you make is unacceptable. You are a disgrace.
The fact that you have 13hrs on type before crashing it and not 10hrs still does not instill one with much confidence in your advice. The fact that you were taught by an ex mil pilot on it also does not seem to have helped you. That is either a reflection of your teacher or your ability to understand, most likely the latter judging from your inability to understand weather for the VMC pilot, dissymetry of lift and many other basic PoF and other priciples. Perhaps you could join the regulator and really make a (totally useless) difference?
No I am not going to correct you.
Stop your dangerous rambling insulting b****cks and do some research and sort it out for yourself.
"Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?
No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters. "
You ask the question. The answer is actually YES YOU ARE WRONG
So your own answer of "NO" and the susequent acusation you make is unacceptable. You are a disgrace.
The fact that you have 13hrs on type before crashing it and not 10hrs still does not instill one with much confidence in your advice. The fact that you were taught by an ex mil pilot on it also does not seem to have helped you. That is either a reflection of your teacher or your ability to understand, most likely the latter judging from your inability to understand weather for the VMC pilot, dissymetry of lift and many other basic PoF and other priciples. Perhaps you could join the regulator and really make a (totally useless) difference?
No I am not going to correct you.
Stop your dangerous rambling insulting b****cks and do some research and sort it out for yourself.