Mast bumping, tailboom chops and two bladed rotors (merged)
Guest
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Mast Bumping
We all know of the risk of rotor separation resulting from mast bumping if Low or Negative G is allowed to develop whilst flying ANY Helicopter with a teetering or semi-rigid head. But does every Pilot know as much as they possibly could about the problem?
I do NOT wish to become embroiled in any argument as to whether the cause is largely due to ‘Pilot error’, design or anything else. That is not the point here.
I DO wish to draw attention to the danger and hopefully prevent another occurrence. Better awareness must always be sought. With that aim in mind I have decided to take an unusual step -To provide this page in the full knowledge that anyone will be able to print it and share it with their Helicopter flying colleagues.
It is still under my copyright, and will remain so, but anyone who wishes to print it and avoid such problems has my permission to do just that. The only conditions are that it must not be sold, resold or republished by any other and that the source is
credited. The item will be available on this site for the next 10 days, after which I will have to use the space on my ISP for another purpose.
Anyone who doubts my sincerity on this is reminded that (A) I provide a website to improve safety awareness (and host this item for Pprune) at my own cost and (B) that this is not a cynical ploy to sell the book itself. The words ‘Gift Horse’, ‘Mouth’ and ’look’ are operative here!
Understand that I just wish to reduce accident figures by DOING SOMETHING to improve awareness of MAST BUMPING, and as I have this item on hand it seems ridiculous that it is not available to every Pilot in the world.
So, if anyone wants to take me up on this offer than all they have to do is push the button. If anyone thinks this is ‘boring R22’s again’, I ask they to remember that it is relevant to other types as well. In any event, the life of a low time Pilot is worth the same as a Space Shuttle Pilot, i.e. ONE.
Fly safe (fly safer) all.
SPS
The early bird catches the worm, but the second mouse gets the cheese.
[This message has been edited by SPS (edited 24 February 2001).]
I do NOT wish to become embroiled in any argument as to whether the cause is largely due to ‘Pilot error’, design or anything else. That is not the point here.
I DO wish to draw attention to the danger and hopefully prevent another occurrence. Better awareness must always be sought. With that aim in mind I have decided to take an unusual step -To provide this page in the full knowledge that anyone will be able to print it and share it with their Helicopter flying colleagues.
It is still under my copyright, and will remain so, but anyone who wishes to print it and avoid such problems has my permission to do just that. The only conditions are that it must not be sold, resold or republished by any other and that the source is
credited. The item will be available on this site for the next 10 days, after which I will have to use the space on my ISP for another purpose.
Anyone who doubts my sincerity on this is reminded that (A) I provide a website to improve safety awareness (and host this item for Pprune) at my own cost and (B) that this is not a cynical ploy to sell the book itself. The words ‘Gift Horse’, ‘Mouth’ and ’look’ are operative here!
Understand that I just wish to reduce accident figures by DOING SOMETHING to improve awareness of MAST BUMPING, and as I have this item on hand it seems ridiculous that it is not available to every Pilot in the world.
So, if anyone wants to take me up on this offer than all they have to do is push the button. If anyone thinks this is ‘boring R22’s again’, I ask they to remember that it is relevant to other types as well. In any event, the life of a low time Pilot is worth the same as a Space Shuttle Pilot, i.e. ONE.
Fly safe (fly safer) all.
SPS
The early bird catches the worm, but the second mouse gets the cheese.
[This message has been edited by SPS (edited 24 February 2001).]
Guest
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Interested to see that Don'ts include diving. I've always presumed that while the transition into a dive should be gentle to avoid negative G, there is nothing wrong with a steady moderate dive at cruise power, within airspeed limits. Is this hazardous and if so, when and why?
Guest
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Thanks for the input.
The main reasoning for this advice is to begin with good habits. If a student is allowed to dive in a limited way from early lessons this may be embedded (and very hard to remove) from their resulting flying style. If they meet a situation in the future that COULD be avoided with a dive then they might just reach for that 'tool' and do it much more quickly or agressively depending on the urgency at the time. Disaster awaits.
Of course, a limited 'dive' can be made, we do that every time we transition away or adopt an accelerative attitude if you wish to see it that way, and in types with different head construction/design a much greater dive is a perfectly acceptable maonevure but for students beginning (and maybe never flying another type in some cases) I decided to stick to this, the safest option.
It is probably due to the way I approach this sort of thing when teaching, ie. with negative G. teach what you must not do first (giving the strongest basic pattern or 'habit')and learn later if that can be modified (if necessary).
If no-one ever 'dives' then Negative G is much less of a risk? Just my view....
The main reasoning for this advice is to begin with good habits. If a student is allowed to dive in a limited way from early lessons this may be embedded (and very hard to remove) from their resulting flying style. If they meet a situation in the future that COULD be avoided with a dive then they might just reach for that 'tool' and do it much more quickly or agressively depending on the urgency at the time. Disaster awaits.
Of course, a limited 'dive' can be made, we do that every time we transition away or adopt an accelerative attitude if you wish to see it that way, and in types with different head construction/design a much greater dive is a perfectly acceptable maonevure but for students beginning (and maybe never flying another type in some cases) I decided to stick to this, the safest option.
It is probably due to the way I approach this sort of thing when teaching, ie. with negative G. teach what you must not do first (giving the strongest basic pattern or 'habit')and learn later if that can be modified (if necessary).
If no-one ever 'dives' then Negative G is much less of a risk? Just my view....
Guest
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I saw nothing wrong with your graphic SPS.
RS:
Thing about the "gentle" dive in a Robbie, or any other teetering head, is it can be done, just not abruptly, a gentle dive doesn't approach the low "G" condition.
You moved the cyclic forward to begin your descent and you stabilized, so now you are in a cruise descent at whatever airspeed, but at 1 "G".
I'll always take a turn to avoid if possible, a dive is just out of the question (I know I know maybe I'll want to, most who ask me this refer to birds, in which I respond that most birds like to "tuck and drop" anyway, so why dive to meet them?
)
BTW, thinking about it, I suppose one could make move in forward cyclic, if you are already in a turn and pulling in collective keeping the head under a load, you would be accellerating and diving at that point, but I wouldn't do it from the level attitude.
Real thing is you don't want to have to make any agressive moves on your controls in the first place.
I got a changce in a British Navy Lynx to see how having a solid head differs, after reaching the top of the ridge, they nosed over and we held onto the backside, a bit of 0 "G" for a moment, something you would never do in a teetering head, but fun when you can!
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Marc
[This message has been edited by RW-1 (edited 25 February 2001).]
RS:
Thing about the "gentle" dive in a Robbie, or any other teetering head, is it can be done, just not abruptly, a gentle dive doesn't approach the low "G" condition.
You moved the cyclic forward to begin your descent and you stabilized, so now you are in a cruise descent at whatever airspeed, but at 1 "G".
I'll always take a turn to avoid if possible, a dive is just out of the question (I know I know maybe I'll want to, most who ask me this refer to birds, in which I respond that most birds like to "tuck and drop" anyway, so why dive to meet them?
)BTW, thinking about it, I suppose one could make move in forward cyclic, if you are already in a turn and pulling in collective keeping the head under a load, you would be accellerating and diving at that point, but I wouldn't do it from the level attitude.
Real thing is you don't want to have to make any agressive moves on your controls in the first place.
I got a changce in a British Navy Lynx to see how having a solid head differs, after reaching the top of the ridge, they nosed over and we held onto the backside, a bit of 0 "G" for a moment, something you would never do in a teetering head, but fun when you can!
------------------
Marc
[This message has been edited by RW-1 (edited 25 February 2001).]
Guest
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Thomas,
Point taken.
The fact that a teetering head may also be semi-rigid has nothing to do with the problem and it is not transferred to types
of head that are semi rigid but not teetering.
What I should have said was 'teetering and
UNDERSLUNG'. The diagram shows clearly how the mast can be contacted by an underslung head in some circumstances. This is the real problem with some types. A teetering head that is not underslung (if made)would not be so susceptible to the effects of Negative G as it would not be able to promote or allow mast bumping.
Coupling 1, Sparrow 0.
(Just for today of course ! )
Point taken.
The fact that a teetering head may also be semi-rigid has nothing to do with the problem and it is not transferred to types
of head that are semi rigid but not teetering.
What I should have said was 'teetering and
UNDERSLUNG'. The diagram shows clearly how the mast can be contacted by an underslung head in some circumstances. This is the real problem with some types. A teetering head that is not underslung (if made)would not be so susceptible to the effects of Negative G as it would not be able to promote or allow mast bumping.
Coupling 1, Sparrow 0.
(Just for today of course
! )
Guest
Posts: n/a
Just an idea or two from an oily rag engineering type...
1) How about a g-meter coupled to a servo which applies aft cyclic (bit like a stick pusher on a jet, but of course it would be a puller)?
or
2) How about a sensor on the mast to catch actual excessive angles, triggering the same servo action? Could be a couple of magnets on the rotating parts and a static hall effect probe or two for instance.
Having said that, SPS has the right idea IMO. Avoidance is the key.
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More volts, Igor
1) How about a g-meter coupled to a servo which applies aft cyclic (bit like a stick pusher on a jet, but of course it would be a puller)?
or
2) How about a sensor on the mast to catch actual excessive angles, triggering the same servo action? Could be a couple of magnets on the rotating parts and a static hall effect probe or two for instance.
Having said that, SPS has the right idea IMO. Avoidance is the key.
------------------
More volts, Igor
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Good use of the forum to get input on issues, thanks all. Glad my normal descent approach technique using 125 kts in a B206 or 135 in a AS350 to claw back a few of those precious seconds lost in the climb doesn't have a mast bumping risk. Certainly having a bit of headroom over fast cruise to Vne/Vma, unlike the 407, does offer a small advantage here; OK it's more psychological but still makes me feel better!
Good point on making it quite clear to any students or low timers that if this technique is used, the initial gentle nose over must be virtually imperceptible.
On teetering types it would be interesting to know what actually is thought to be the catastrophic precipitating manoeuvre - was it intentional or accidental abrupt nose over or was it turbulence. I have certainly had occasional cabin/baggage contents bangs in a 206 from presumably momentary 0 (or worse) G in very turbulent conditions over hills, despite being at reduced power. Presumably mast bumping is aggravated by low G with big cyclic input?
Good point on making it quite clear to any students or low timers that if this technique is used, the initial gentle nose over must be virtually imperceptible.
On teetering types it would be interesting to know what actually is thought to be the catastrophic precipitating manoeuvre - was it intentional or accidental abrupt nose over or was it turbulence. I have certainly had occasional cabin/baggage contents bangs in a 206 from presumably momentary 0 (or worse) G in very turbulent conditions over hills, despite being at reduced power. Presumably mast bumping is aggravated by low G with big cyclic input?
Guest
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'Presumably mast bumping is aggravated by low G with big cyclic input?'
Fully agree with that Rotorspeed.
Low G involves the disc being unloaded, it therefore has no control over the fuselage which may adopt an attitude placing the mast at far less than 90 degrees to the POR in one sector of the 360 degree head cycle.
Add that to large cyclic inputs (worse if made suddenly, aggressively) which can place the underslung hub even closer to the mast and its goodnight nurse.
Of course, it does not have to be fuselage movement relative to the disc which may cause mast bumping. If the disc flaps violently (turbulence is a major cause)the same can happen. This is more likely to occur at high airspeeds with large pitch angles applied to the blades and is a good reason for reducing speed if flying in turbulent conditions.
Chips, my background too. I will mull it over
and reply later, thanks for the ideas. One thing I can say for certainty rightaway is this - No underslinging = a lot less risk.
I'd err on the side of designing the problem right out in preference to preventative measures that may fail to work. I'm not rubbishing the idea, far from it.
Finally, for completeness, the underslung head (hub) is mainly employed to overcome Hooke's Joint Effect. It does so using less parts, maintenance and initial cost. If the blades had the freedom to lead and lag (or flex) then the head would not have to be underslung.
Fully agree with that Rotorspeed.
Low G involves the disc being unloaded, it therefore has no control over the fuselage which may adopt an attitude placing the mast at far less than 90 degrees to the POR in one sector of the 360 degree head cycle.
Add that to large cyclic inputs (worse if made suddenly, aggressively) which can place the underslung hub even closer to the mast and its goodnight nurse.
Of course, it does not have to be fuselage movement relative to the disc which may cause mast bumping. If the disc flaps violently (turbulence is a major cause)the same can happen. This is more likely to occur at high airspeeds with large pitch angles applied to the blades and is a good reason for reducing speed if flying in turbulent conditions.
Chips, my background too. I will mull it over
and reply later, thanks for the ideas. One thing I can say for certainty rightaway is this - No underslinging = a lot less risk.
I'd err on the side of designing the problem right out in preference to preventative measures that may fail to work. I'm not rubbishing the idea, far from it.
Finally, for completeness, the underslung head (hub) is mainly employed to overcome Hooke's Joint Effect. It does so using less parts, maintenance and initial cost. If the blades had the freedom to lead and lag (or flex) then the head would not have to be underslung.
Guest
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This accident report is worth a look - experienced pilot ( both in hours and on type ) but mast bumping killed him and the observer. The suspected cause was turbulence, not mishandling.
http://www.open.gov.uk/aaib/apr99htm/gshrr.htm
[This message has been edited by The Nr Fairy (edited 26 February 2001).]
http://www.open.gov.uk/aaib/apr99htm/gshrr.htm
[This message has been edited by The Nr Fairy (edited 26 February 2001).]
Guest
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RotorSpeed/SPS:
Rotor's question is a good one. From what I have read it is not really the low "G" condition that kills, it's making the wrong move afterwards. If you give that cyclic (lateral is usually it, one should give aft)
movement prior to loading the rotor back up, boom.
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Marc
Rotor's question is a good one. From what I have read it is not really the low "G" condition that kills, it's making the wrong move afterwards. If you give that cyclic (lateral is usually it, one should give aft)
movement prior to loading the rotor back up, boom.
------------------
Marc
Guest
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To: RotorSpeed/SPS and RW 1
"Rotor's question is a good one. From what I have read it is not really the low "G" condition that kills, it's making the wrong move afterwards. If you give that cyclic (lateral is usually it, one should give aft)
movement prior to loading the rotor back up, boom".
This is probably the very first time I have totally agreed with RW 1 as every thing he said in the above quote it 100%correct
I would like to resurrect the dead horse and beat it a few more times. It is my contention that the 18-degree offset on the Robinson head results in a right cyclic bias in order to fly straight-ahead. When the pilot encounters a zero G condition he is warned to bring the cyclic straight back to reload the rotor disc. When he does this with the right cyclic bias he actually introduces a right roll component. This exacerbates the right roll caused by the tail rotor and he enters into a “violent” right roll. If he counters the right roll by pushing left cyclic he encounters violent flapping loads that result in mast bumping and/or fuselage incursion.
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The Cat
"Rotor's question is a good one. From what I have read it is not really the low "G" condition that kills, it's making the wrong move afterwards. If you give that cyclic (lateral is usually it, one should give aft)
movement prior to loading the rotor back up, boom".
This is probably the very first time I have totally agreed with RW 1 as every thing he said in the above quote it 100%correct
I would like to resurrect the dead horse and beat it a few more times. It is my contention that the 18-degree offset on the Robinson head results in a right cyclic bias in order to fly straight-ahead. When the pilot encounters a zero G condition he is warned to bring the cyclic straight back to reload the rotor disc. When he does this with the right cyclic bias he actually introduces a right roll component. This exacerbates the right roll caused by the tail rotor and he enters into a “violent” right roll. If he counters the right roll by pushing left cyclic he encounters violent flapping loads that result in mast bumping and/or fuselage incursion.
------------------
The Cat
Guest
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All I have to say on the ressurection:
I leave it for the engineers to figure out why, and I agree with the contention, however I have not seen the aircraft exhibit it.
Avoidance is the best form. Hopefully one is "Far enough ahead of the aircraft" to not have to make sudden cyclic movements, I expand being ahead to include knowing possible traffic conflicts, etc. This limits you to a reaction to that nasty suprise that no one can forsee.
However I would like Lou's opinion on what I stated earlier. Let's say (without bringing in the robbies offset into the equation)
If I decide to pull a hard cyclic turn, pull in a little collective and then am pushing forward right or left cyclic for the turn, would the rotor stay under a good enough load to prevent getting into the low "G" area? (thinking in terms of a good strategy when one does need to lose alt and turn at the same time. My thought is if I'm shoving 45 degrees right or left but pulling in collective, rotor keeps most of the load though I'll start to drop and gain airspeed.
Is there a balance that can be maintained?
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Marc
I leave it for the engineers to figure out why, and I agree with the contention, however I have not seen the aircraft exhibit it.
Avoidance is the best form. Hopefully one is "Far enough ahead of the aircraft" to not have to make sudden cyclic movements, I expand being ahead to include knowing possible traffic conflicts, etc. This limits you to a reaction to that nasty suprise that no one can forsee.
However I would like Lou's opinion on what I stated earlier. Let's say (without bringing in the robbies offset into the equation)
If I decide to pull a hard cyclic turn, pull in a little collective and then am pushing forward right or left cyclic for the turn, would the rotor stay under a good enough load to prevent getting into the low "G" area? (thinking in terms of a good strategy when one does need to lose alt and turn at the same time. My thought is if I'm shoving 45 degrees right or left but pulling in collective, rotor keeps most of the load though I'll start to drop and gain airspeed.
Is there a balance that can be maintained?
------------------
Marc
Guest
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I'm more than a little disturbed this morning.
I have had 2 private mails over the last couple of days from private pilots in the UK that fly teetering/underslung a/c and they both say that that they have not been made aware of this peril and want to know more.
No, I'm not berating UK training or any individual organisation or instructor. I make no judgement at all. I was taught in UK and made WELL aware of this. I later taught students in UK and did all I could to emphasise the problem. It may well be that it HAS been explained to them but they 'forgot', and that may happen anywhere.
A previous Chief Pilot (no, I was an AFI) of the organisation I did my training with had been killed a couple of years earlier (RIP Harry Knapp) whilst demonstrating Low G (it was allowed then, or not specifically forbidden) and that left its mark on me. But does someone have to die before all sit up and take notice? I think not, and that is part of the reasoning behind this thread.
Whatever the reasons for these two pilots not having sufficient knowledge, (BTW it does indicate that pilots read prune but choose not to post replies) the effect is the same. It is plain that MORE awareness of mast bumping and its cause(s)is required and I'm sure the need is NOT isolated to one country only. Do not forget that it is also NOT isolated to only one Helicopter type either.
I'm taking things a little further by adding the mast bumping item to my website, make it more available to all who need it.
One of these chaps could not print the item from prune, maybe he will be able to do so from my site. If that fails and anyone wants the info. but doesn't want to buy the book then that's also fine, I'll send a copy out at my own cost, even if it must be snail mail.
At risk of sounding insincere on this, I will mention that there are another 120 pages of similar information in my book and that also should be out there doing what it was intended to do. It most certainly was not about collecting money. But I cannot provide all for nothing (although I wish I could) as economics rear their head(s).
A copy of the book may be ordered through the website.
To all of you out there, let's begin a campaign aimed at making sure EVERY Pilot can give you back chapter and verse on mast bumping, and not focus on why they can't now.
SPS
If a little knowledge is dangerous, greater
knowledge promotes safety.
I have had 2 private mails over the last couple of days from private pilots in the UK that fly teetering/underslung a/c and they both say that that they have not been made aware of this peril and want to know more.
No, I'm not berating UK training or any individual organisation or instructor. I make no judgement at all. I was taught in UK and made WELL aware of this. I later taught students in UK and did all I could to emphasise the problem. It may well be that it HAS been explained to them but they 'forgot', and that may happen anywhere.
A previous Chief Pilot (no, I was an AFI) of the organisation I did my training with had been killed a couple of years earlier (RIP Harry Knapp) whilst demonstrating Low G (it was allowed then, or not specifically forbidden) and that left its mark on me. But does someone have to die before all sit up and take notice? I think not, and that is part of the reasoning behind this thread.
Whatever the reasons for these two pilots not having sufficient knowledge, (BTW it does indicate that pilots read prune but choose not to post replies) the effect is the same. It is plain that MORE awareness of mast bumping and its cause(s)is required and I'm sure the need is NOT isolated to one country only. Do not forget that it is also NOT isolated to only one Helicopter type either.
I'm taking things a little further by adding the mast bumping item to my website, make it more available to all who need it.
One of these chaps could not print the item from prune, maybe he will be able to do so from my site. If that fails and anyone wants the info. but doesn't want to buy the book then that's also fine, I'll send a copy out at my own cost, even if it must be snail mail.
At risk of sounding insincere on this, I will mention that there are another 120 pages of similar information in my book and that also should be out there doing what it was intended to do. It most certainly was not about collecting money. But I cannot provide all for nothing (although I wish I could) as economics rear their head(s).
A copy of the book may be ordered through the website.
To all of you out there, let's begin a campaign aimed at making sure EVERY Pilot can give you back chapter and verse on mast bumping, and not focus on why they can't now.
SPS
If a little knowledge is dangerous, greater
knowledge promotes safety.
Guest
Posts: n/a
Nr Fairy,
In providing the aaib link (that I have just read) I think you have greatly assisted the purpose of this thread and I'd like to thank you for doing so. I encourage any member to post similar links.
I strongly recommend that all and any use Nr's link.
Read the report it leads to, it is important.
In providing the aaib link (that I have just read) I think you have greatly assisted the purpose of this thread and I'd like to thank you for doing so. I encourage any member to post similar links.
I strongly recommend that all and any use Nr's link.
Read the report it leads to, it is important.
Guest
Posts: n/a
Lu,
At the risk of flogging a dead horse,take another look at the diagram which shows the helicopter in the mast bump situation.
If the disc tilts a little to the right when appling aft cyclic in recovery,it will provide greater clearance between the head and the mast, therefor making mast bump LESS likely.
At the risk of flogging a dead horse,take another look at the diagram which shows the helicopter in the mast bump situation.
If the disc tilts a little to the right when appling aft cyclic in recovery,it will provide greater clearance between the head and the mast, therefor making mast bump LESS likely.
Guest
Posts: n/a
SPS:
I ALWAYS read the AAIB reports the day they come out, and not just the helicopters ones, either. Anything which will help me fill the bag of experience before emptying the bag of luck is most welcome.
On your other post, private emails about people being unaware of mast bumping, I learnt in Oz and was taught about it during training, and also it was stressed during the safety course I went on. It would be nice to know if there's a pattern to where the knowledge isn't being imparted, or whether it's student related.
I ALWAYS read the AAIB reports the day they come out, and not just the helicopters ones, either. Anything which will help me fill the bag of experience before emptying the bag of luck is most welcome.
On your other post, private emails about people being unaware of mast bumping, I learnt in Oz and was taught about it during training, and also it was stressed during the safety course I went on. It would be nice to know if there's a pattern to where the knowledge isn't being imparted, or whether it's student related.
Guest
Posts: n/a
Nr,
Yes, It was bashed into me in UK and then on UK and US safety courses.
I doubt that the problem can be isolated to areas or even schools. I know that everywhere
I've been ( I've been around a little)
has instructors that give warnings on the subject. I'm not trying to make anyone wrong but I do think it more likely that it has been mentioned and then forgotten by the sutdent in some cases.
BUT! If that is the case, it also means it has NOT BEEN MENTIONED OFTEN ENOUGH!
Interesting point from Outside loop. I've been trying to avoid the 18 deg. issue because I am still 'processing' on it and do not wish to centre on one type (read Nr's link to the 206 occurrence) but this has me thinking....
Hmmmmmm...
Yes, It was bashed into me in UK and then on UK and US safety courses.
I doubt that the problem can be isolated to areas or even schools. I know that everywhere
I've been ( I've been around a little)
has instructors that give warnings on the subject. I'm not trying to make anyone wrong but I do think it more likely that it has been mentioned and then forgotten by the sutdent in some cases.
BUT! If that is the case, it also means it has NOT BEEN MENTIONED OFTEN ENOUGH!
Interesting point from Outside loop. I've been trying to avoid the 18 deg. issue because I am still 'processing' on it and do not wish to centre on one type (read Nr's link to the 206 occurrence) but this has me thinking....
Hmmmmmm...
Guest
Posts: n/a
Some reflections -
RW 1 - During your 45 degree turn the disc loading has increased way beyond 1G. The limit for the R22 (done well keeping myself off types until now I guess) is 53 degrees angle of bank resulting in the max. permissible disc loading (1.7G). At 45 degrees it is likely to be 1.4 or 1.5 G
and this would give you a greater margin against low or negative G so there is less of a problem than there would be in forward flight.
LZ-
'When he does this with the right cyclic bias he actually introduces a right roll component. This exacerbates the right roll caused by the tail rotor and he enters into a “violent” right roll. If he counters the right roll by pushing left cyclic he encounters violent flapping loads that result in mast bumping and/or fuselage incursion.'
OK. I do see your point but have one problem with this train of thought.
The main reason that low or negative G is a problem for this type of head is that cyclic
(and therefore disc) authority over the fuselage has been lost, This is what enables TR thrust to induce fuselage roll to the right and the possiblity of the hub and mast being in contention exists only because of this.
Why should a right cyclic bias exaserbate right fuselage roll? The cyclic (disc) has lost authority and cannot affect fuselage attitude. Add to that Outside loop's point about the hub/ mast clearance being increased
(not decreased) if any authority were present and it begins to look as if this particular type may have no more of a problem
than any other that is similarly constructed
and designed.
Chips - On balance I think I would go for a 'design out' rather than remedial acton but ecomomics may give it to the latter, as with many things in life.
Keep it coming - It can only be good for everyone in Aviation.
SPS
RW 1 - During your 45 degree turn the disc loading has increased way beyond 1G. The limit for the R22 (done well keeping myself off types until now I guess) is 53 degrees angle of bank resulting in the max. permissible disc loading (1.7G). At 45 degrees it is likely to be 1.4 or 1.5 G
and this would give you a greater margin against low or negative G so there is less of a problem than there would be in forward flight.
LZ-
'When he does this with the right cyclic bias he actually introduces a right roll component. This exacerbates the right roll caused by the tail rotor and he enters into a “violent” right roll. If he counters the right roll by pushing left cyclic he encounters violent flapping loads that result in mast bumping and/or fuselage incursion.'
OK. I do see your point but have one problem with this train of thought.
The main reason that low or negative G is a problem for this type of head is that cyclic
(and therefore disc) authority over the fuselage has been lost, This is what enables TR thrust to induce fuselage roll to the right and the possiblity of the hub and mast being in contention exists only because of this.
Why should a right cyclic bias exaserbate right fuselage roll? The cyclic (disc) has lost authority and cannot affect fuselage attitude. Add to that Outside loop's point about the hub/ mast clearance being increased
(not decreased) if any authority were present and it begins to look as if this particular type may have no more of a problem
than any other that is similarly constructed
and designed.
Chips - On balance I think I would go for a 'design out' rather than remedial acton but ecomomics may give it to the latter, as with many things in life.
Keep it coming - It can only be good for everyone in Aviation.
SPS