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  #1  
Old February 9th 10, 12:16 AM posted to rec.aviation.rotorcraft
Stu Fields
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Posts: 87
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It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. However, lets say that a low
hour helicopter suffers a failure directly attibutable to fatigue. Further
lets assume that the helicopter had had a prior series of hard landings or
other beyond normal stress loadings. Now lets further assume that the
fatigue failure occurred at a point in the helicopter drive system where a
diameter change was machined into the shaft without any radius or attempt at
a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits have
been sold with the same machining flaw.
Should the kit manufacturer issue a service advisory statement advising all
owners of those ships of a potential safety issue caused by those parts?
What should their action be? Recall and supply exchange parts for no
charge? Recall and supply exchange parts for their cost? Change the
machining process and ignore the other parts out there?
How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Ads
  #2  
Old February 9th 10, 04:19 PM posted to rec.aviation.rotorcraft
oldrotor
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Posts: 1
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On Feb 8, 6:16*pm, "Stu Fields" wrote:
It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. * However, lets say that a low
hour helicopter suffers a failure directly attibutable to fatigue. *Further
lets assume that the helicopter had had a *prior series of hard landings or
other beyond normal stress loadings. *Now lets further assume that the
fatigue failure occurred at a point in the helicopter drive system where a
diameter change was machined into the shaft without any radius or attempt at
a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits have
been sold with the same machining flaw.
Should the kit manufacturer issue a service advisory statement advising all
owners of those ships of a potential safety issue caused by those parts?
What should their action be? *Recall and supply exchange parts for no
charge? *Recall and supply exchange parts for their cost? *Change the
machining process and ignore the other parts out there?
How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Anybody know why this guy has such a hard-on?
  #3  
Old February 9th 10, 05:37 PM posted to rec.aviation.rotorcraft
Stu Fields
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Posts: 87
Default credibiltiy


"oldrotor" wrote in message
...
On Feb 8, 6:16 pm, "Stu Fields" wrote:
It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. However, lets say that a low
hour helicopter suffers a failure directly attibutable to fatigue. Further
lets assume that the helicopter had had a prior series of hard landings or
other beyond normal stress loadings. Now lets further assume that the
fatigue failure occurred at a point in the helicopter drive system where a
diameter change was machined into the shaft without any radius or attempt
at
a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits
have
been sold with the same machining flaw.
Should the kit manufacturer issue a service advisory statement advising
all
owners of those ships of a potential safety issue caused by those parts?
What should their action be? Recall and supply exchange parts for no
charge? Recall and supply exchange parts for their cost? Change the
machining process and ignore the other parts out there?
How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Anybody know why this guy has such a hard-on?

I'll answer your question if you answer mine..


  #4  
Old February 11th 10, 04:13 PM posted to rec.aviation.rotorcraft
Steve R.[_2_]
external usenet poster
 
Posts: 31
Default credibiltiy

"Stu Fields" wrote in message
...
It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. However, lets say that a low
hour helicopter suffers a failure directly attibutable to fatigue.
Further lets assume that the helicopter had had a prior series of hard
landings or other beyond normal stress loadings. Now lets further assume
that the fatigue failure occurred at a point in the helicopter drive
system where a diameter change was machined into the shaft without any
radius or attempt at a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits
have been sold with the same machining flaw.
Should the kit manufacturer issue a service advisory statement advising
all owners of those ships of a potential safety issue caused by those
parts? What should their action be? Recall and supply exchange parts for
no charge? Recall and supply exchange parts for their cost? Change the
machining process and ignore the other parts out there?
How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Hi Stu,

You mention a lot of variables here. My thoughts are this - first, why did
the bird have a series of hard landings or other "beyond normal stress
loadings?" Those, to me, sound like a piloting issue and not necessarily
the kit manufacturers problem. Second, if the kit manufacturer discovers
that they're selling parts that do have some kind of defect in design or
machining, I think they should be obligated to making that right, either by
an outright recall or by offering proper replacements to kit owners at cost.
At the very least, they should issue a service advisory statement on the
problem to be certain that the kit owners are aware it.

Having said that, we are talking about "experimental" aircraft here. If I
understand all that correctly, that means the owner/builder "is" the
manufacturer of the aircraft and is ultimately the one responsible for the
safe operation and maintenance of said aircraft. Still, if the kit
manufacturer has any integrity, they'll be doing all they can to assist
their customers with parts and materials that are discovered to be less than
ideal for the job it's asked to do.

I'm reminded of something Air Command did many years ago when they finally
came around to the benefits of an in-line thrust design for pusher style
gyroplanes. If I'm remembering correctly, they issued a statement advising
anyone owning the older/original design bird to stop flying them and offered
a new frame upgrade with a center line thrust design to "any" owner, "at
cost," regardless of whether those owners bought the bird directly from Air
Command or from an individual. I think it took a lot of guts for them to do
that and speaks volumes for the integrity of the company.

Does that answer your question? At least it might help spark the
conversation! :-)

Fly Safe,
Steve R.

  #5  
Old February 11th 10, 07:12 PM posted to rec.aviation.rotorcraft
Stu Fields
external usenet poster
 
Posts: 87
Default credibiltiy


"Steve R." wrote in message
...
"Stu Fields" wrote in message
...
It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. However, lets say that a
low hour helicopter suffers a failure directly attibutable to fatigue.
Further lets assume that the helicopter had had a prior series of hard
landings or other beyond normal stress loadings. Now lets further assume
that the fatigue failure occurred at a point in the helicopter drive
system where a diameter change was machined into the shaft without any
radius or attempt at a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits
have been sold with the same machining flaw.
Should the kit manufacturer issue a service advisory statement advising
all owners of those ships of a potential safety issue caused by those
parts? What should their action be? Recall and supply exchange parts for
no charge? Recall and supply exchange parts for their cost? Change the
machining process and ignore the other parts out there?
How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Hi Stu,

You mention a lot of variables here. My thoughts are this - first, why
did the bird have a series of hard landings or other "beyond normal stress
loadings?" Those, to me, sound like a piloting issue and not necessarily
the kit manufacturers problem. Second, if the kit manufacturer discovers
that they're selling parts that do have some kind of defect in design or
machining, I think they should be obligated to making that right, either
by an outright recall or by offering proper replacements to kit owners at
cost. At the very least, they should issue a service advisory statement on
the problem to be certain that the kit owners are aware it.

Having said that, we are talking about "experimental" aircraft here. If I
understand all that correctly, that means the owner/builder "is" the
manufacturer of the aircraft and is ultimately the one responsible for the
safe operation and maintenance of said aircraft. Still, if the kit
manufacturer has any integrity, they'll be doing all they can to assist
their customers with parts and materials that are discovered to be less
than ideal for the job it's asked to do.

I'm reminded of something Air Command did many years ago when they finally
came around to the benefits of an in-line thrust design for pusher style
gyroplanes. If I'm remembering correctly, they issued a statement
advising anyone owning the older/original design bird to stop flying them
and offered a new frame upgrade with a center line thrust design to "any"
owner, "at cost," regardless of whether those owners bought the bird
directly from Air Command or from an individual. I think it took a lot of
guts for them to do that and speaks volumes for the integrity of the
company.

Does that answer your question? At least it might help spark the
conversation! :-)

Fly Safe,
Steve R.



Surprising enough a series of hard landings were experienced by high time
helicopter pilot. Ship didn't have anywhere near 400hrs when a shaft in the
transmission experienced a fatigue failure. The focus was on the hard
landings as the cause and the stress risers of the shaft were ignored.
Another accident occurred where the builder did something not right which
caused some strong vibrations. He corrected the problem but didn't replace
a part that had a near zero radius fillet and that is exactly where the
fatigue failure occurred. This resulted in a fatal accident. Another fatal
accident occurred where another fatigue failure occurred at a place where
the fillet radius was reported as sharp. Again other historical occurences
were logged and the failure occurred at the sharp fillet radius. Again the
focus was placed on the historical occurrences and not on the poorly
machined fillet.
There are a number of kits out there that have been supplied similar
elements. The machinist for these parts had drawings which did not call out
a fillet radius. (That has been changed now.)
Another instance was called to the kit manufacturers attention where a
rubber seal was scarring (0.020 deep jagged groove) in a main rotor shaft.
The response was that they had seen this before and it didn't constitute a
dangerous condition.
To date the kit manufacturer has not sent out any warnings. They merely, on
their website, offer to inspect and replace the parts if you are concerned
about them. It sounds like they don't see a problem, but if you the
builder-flyer does, they will try to make you happy.
All of these parts are enclosed inside elements that come from the kit
manufacturer complete and closed up and evern cotter keyed. Unless the kit
builder tears these elements down and has enough of a technical background
to do a good inspection, he will not be aware of the risk that he is taking.
Yeah the Air Command story speaks highly of someone's integrity. (We
probably know the guy). The "Center Line Thrust" was an arguable issue.
Cdr. Ken Wallis had his opinions about this and he had more than a few hours
in non "Center Line Thrust" ships. On the other hand the Stress
concentrations seen in this other kit is a well known issue to avoid.
Yeah I wish this kit manufacturer of issue would adopt the Air Command
philosphy.

Stu


  #6  
Old February 12th 10, 04:32 AM posted to rec.aviation.rotorcraft
Steve R.[_2_]
external usenet poster
 
Posts: 31
Default credibiltiy

"Stu Fields" wrote in message
...


Surprising enough a series of hard landings were experienced by high time
helicopter pilot. Ship didn't have anywhere near 400hrs when a shaft in
the transmission experienced a fatigue failure. The focus was on the hard
landings as the cause and the stress risers of the shaft were ignored.
Another accident occurred where the builder did something not right which
caused some strong vibrations. He corrected the problem but didn't
replace a part that had a near zero radius fillet and that is exactly
where the fatigue failure occurred. This resulted in a fatal accident.
Another fatal accident occurred where another fatigue failure occurred at
a place where the fillet radius was reported as sharp. Again other
historical occurences were logged and the failure occurred at the sharp
fillet radius. Again the focus was placed on the historical occurrences
and not on the poorly machined fillet.
There are a number of kits out there that have been supplied similar
elements. The machinist for these parts had drawings which did not call
out a fillet radius. (That has been changed now.)
Another instance was called to the kit manufacturers attention where a
rubber seal was scarring (0.020 deep jagged groove) in a main rotor
shaft. The response was that they had seen this before and it didn't
constitute a dangerous condition.
To date the kit manufacturer has not sent out any warnings. They merely,
on their website, offer to inspect and replace the parts if you are
concerned about them. It sounds like they don't see a problem, but if you
the builder-flyer does, they will try to make you happy.
All of these parts are enclosed inside elements that come from the kit
manufacturer complete and closed up and evern cotter keyed. Unless the
kit builder tears these elements down and has enough of a technical
background to do a good inspection, he will not be aware of the risk that
he is taking.
Yeah the Air Command story speaks highly of someone's integrity. (We
probably know the guy). The "Center Line Thrust" was an arguable issue.
Cdr. Ken Wallis had his opinions about this and he had more than a few
hours in non "Center Line Thrust" ships. On the other hand the Stress
concentrations seen in this other kit is a well known issue to avoid.
Yeah I wish this kit manufacturer of issue would adopt the Air Command
philosphy.

Stu


Well, it certainly sounds like the kit manufacturer isn't much interested in
making this good without a lot more motivation. Considering they know the
tail drive needs updating (and has, in fact, within their organization), I'd
think they'd want to let that fact be known. It's a matter of safety and
it's disappointing that they're not stepping up on this. I assume you're
not in a position to say what company this is?

The tail drive issues are one thing. I'm absolutely flabbergasted that
they'd say that a groove being machined into the "main rotor mast" by a
problem seal "doesn't constitute a dangerous condition!!!" Good, then let
"them" fly the thing!

I understand that the centerline thrust issues was/is a hotly debated issue.
I never understood why that was. I understand that there are relatively
high time pilots out there that learned on HTL machines and have
successfully flown them for many hours but that doesn't counter the fact
that these machines are easily capable of doing the classic bunt over, or
power push over. Too many people have died because of it, including others
who were also described as "experienced" gyro pilots!! A true CLT pusher
style gyro will not do that and is inherently a safer bird because of it.
The fact that some well respected and experienced gyro pilots argued hard in
favor of the HTL side of things left a very bad taste in my mouth way back
when.

Good luck with whatever you're trying to establish with the helicopter kit
manufacturer!

Fly Safe,
Steve R.

  #7  
Old February 12th 10, 08:20 PM posted to rec.aviation.rotorcraft
Stu Fields
external usenet poster
 
Posts: 87
Default credibiltiy


"Steve R." wrote in message
...
"Stu Fields" wrote in message
...


Surprising enough a series of hard landings were experienced by high time
helicopter pilot. Ship didn't have anywhere near 400hrs when a shaft in
the transmission experienced a fatigue failure. The focus was on the
hard landings as the cause and the stress risers of the shaft were
ignored. Another accident occurred where the builder did something not
right which caused some strong vibrations. He corrected the problem but
didn't replace a part that had a near zero radius fillet and that is
exactly where the fatigue failure occurred. This resulted in a fatal
accident. Another fatal accident occurred where another fatigue failure
occurred at a place where the fillet radius was reported as sharp. Again
other historical occurences were logged and the failure occurred at the
sharp fillet radius. Again the focus was placed on the historical
occurrences and not on the poorly machined fillet.
There are a number of kits out there that have been supplied similar
elements. The machinist for these parts had drawings which did not call
out a fillet radius. (That has been changed now.)
Another instance was called to the kit manufacturers attention where a
rubber seal was scarring (0.020 deep jagged groove) in a main rotor
shaft. The response was that they had seen this before and it didn't
constitute a dangerous condition.
To date the kit manufacturer has not sent out any warnings. They merely,
on their website, offer to inspect and replace the parts if you are
concerned about them. It sounds like they don't see a problem, but if
you the builder-flyer does, they will try to make you happy.
All of these parts are enclosed inside elements that come from the kit
manufacturer complete and closed up and evern cotter keyed. Unless the
kit builder tears these elements down and has enough of a technical
background to do a good inspection, he will not be aware of the risk that
he is taking.
Yeah the Air Command story speaks highly of someone's integrity. (We
probably know the guy). The "Center Line Thrust" was an arguable issue.
Cdr. Ken Wallis had his opinions about this and he had more than a few
hours in non "Center Line Thrust" ships. On the other hand the Stress
concentrations seen in this other kit is a well known issue to avoid.
Yeah I wish this kit manufacturer of issue would adopt the Air Command
philosphy.

Stu


Well, it certainly sounds like the kit manufacturer isn't much interested
in making this good without a lot more motivation. Considering they know
the tail drive needs updating (and has, in fact, within their
organization), I'd think they'd want to let that fact be known. It's a
matter of safety and it's disappointing that they're not stepping up on
this. I assume you're not in a position to say what company this is?

The tail drive issues are one thing. I'm absolutely flabbergasted that
they'd say that a groove being machined into the "main rotor mast" by a
problem seal "doesn't constitute a dangerous condition!!!" Good, then let
"them" fly the thing!

I understand that the centerline thrust issues was/is a hotly debated
issue. I never understood why that was. I understand that there are
relatively high time pilots out there that learned on HTL machines and
have successfully flown them for many hours but that doesn't counter the
fact that these machines are easily capable of doing the classic bunt
over, or power push over. Too many people have died because of it,
including others who were also described as "experienced" gyro pilots!! A
true CLT pusher style gyro will not do that and is inherently a safer bird
because of it. The fact that some well respected and experienced gyro
pilots argued hard in favor of the HTL side of things left a very bad
taste in my mouth way back when.

Good luck with whatever you're trying to establish with the helicopter kit
manufacturer!

Fly Safe,
Steve R.


Steve: As an old Bensen pilot from the "Self Taught 60's" when dual
instruction didn't exist, I taught myself to fly the thing as well a my wife
at the time soloed also. However, the advent of the side-by-side ships
presented an aerodynamic "Barn Door" which may have had something to do with
the bunt overs, and there were sure a bunch. I flew in winds and turbulence
with mine strong enough to hover and fly backwards and never had a problem.
In fact our ship never had a ding. It is true that once while doing the
"Brock Spirals" I noticed the nose tipping over more and more. Reduction of
throttle and easing forward on the cyclic and stopping the rotation was all
that was required. Based on my experience, I think that the old Bensens
were relatively safe with their "Rock Guard" horizontal and a relatively
high thrust line. I also noticed flying the Sparrohawk prototype that the
hands off flying thru turbulence had nearly zero pitch disturbance. I guess
if I had a side-by-side gyro I would probably look much closer at the CLT.
However the helicopters have my attention now.
This issue with the scarred main rotor shaft is the fourth separate issue of
what is apparently ignorance or disregard of fatigue problems. Even when I
reference things like the Standard Handbook of Machine Design, they pretty
much ignore me. I don't understand their apparent ignoring what could be a
very nasty liability issue.

Stu


  #8  
Old February 20th 10, 12:10 AM posted to rec.aviation.rotorcraft
Stu Fields
external usenet poster
 
Posts: 87
Default credibiltiy


"The OTHER Kevin in San Diego" skiddz "AT" adelphia "DOT" net wrote in
message ...
On Mon, 8 Feb 2010 16:16:59 -0800, "Stu Fields" wrote:

It seems that if there are two possible causes for a helicopter accident,
the preferred one for the manufacturer is the one for which they have no
fault. That certainly is the best for them. However, lets say that a low
hour helicopter suffers a failure directly attibutable to fatigue.
Further
lets assume that the helicopter had had a prior series of hard landings
or
other beyond normal stress loadings. Now lets further assume that the
fatigue failure occurred at a point in the helicopter drive system where a
diameter change was machined into the shaft without any radius or attempt
at
a proper fillet which yielded a strong stress riser.
Lets say that the kit manufacturer is very aware that a number of kits
have
been sold with the same machining flaw.


Should the kit manufacturer issue a service advisory statement advising
all
owners of those ships of a potential safety issue caused by those parts?


You'd hope so.

What should their action be? Recall and supply exchange parts for no
charge?


If it's a machining/design defect, absolutely. Since you mention in a
later post the machine shop was given drawings that don't indicate any
type of fillet where the diameter of the shaft changes, I'd lean
towards a design defect and expect the manufacturer to replace the
shaft on their dime.

Recall and supply exchange parts for their cost?


At a minimum.

Change the
machining process and ignore the other parts out there?


If I'm following what you said, it's not a machining process issue.
It's that the designer (or CAD guy) didn't call out that fillet.

How about sell the business to someone else and just duck and hope that
nothing bad ever comes from the above?


Would that "absolve" the previous owners of any liability, especially
if they were aware of the issue prior to peddling the biz? Common
sense (and the litigous nature of the States these days) says no but
we all know how short in supply THAT is.

This wouldn't have anything to do with your upcoming project, would
it?

Hi Kevin.

Things have moved on. I have found a jagged groove in the main rotor shaft
that is approx 0.020 deep with jagged bottom. I've got a photo from an
optical comparator for more detail. This groove occurs just at the top of a
roller bearing that is the last point of support of the shaft. There is a
rubber seal at this point. Manufacturers instructions were to remove the
spring from the inside of this seal to avoid possible gouging of the shaft.
Well evidently the rubber seal is capable without the spring of generating
this jagged groove. The manufacturer has said that they have seen these
before and they do not constitute a hazardous condition!!
This is a soft (non-heat treated) TI shaft and all my books say that TI
doesn't handle fatigue well if the surface of the shaft is rough with
imperfections. I could be wrong, but I don't believe that the manufacturer
has done a detailed fatigue analysis of the shaft with this kind of groove.
Hell with what I've read about fatigue, it would take a world famous
structural engineer with a bunch of fatigue design experience to convince me
to fly that shaft. Even then I would want to try to borrow a bunch of money
from him before my flight to test his surety.
Apparently, based on written statements, the manufacturer doesn't believe
that any of the accidents that occured were the fault of the poor fillets.
Even in spite of the accident investigating agencies statement that the
fatigue failure had occurred where the fillet was a sharp corner. There
were reportedly other events of exceptional stresses that possibly could
have started a crack in these highly stressed points.
The mfr. has issued drawings that specify radiuses at the flillet locations
and have offered a "Speedy-Sleeve" to protect the shaft from seal wear. All
new ships are supposed to have these mods.
The manufacturer has offered to provide these parts to owners of older
ships. However, there has been no indication that the owners will receive
any cost breaks.
Aah the world of experimental aviation!!! I have sure got a new
appreciation for the depth of the education available to the people who
build, or buy kit aircraft.

Upcoming project has had a closer look at the serious points and so far it
looks good. That isn't to say that I'm not finding some warts on it, but so
far, with the exception of adequate room for a helmet, the warts look easily
handleable.


 




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