number of rotor blades

[Rob Fonhof]

Just a theoretical question that someone may be able to help with.
Alot of helicopters have only two rotor blades, ie:Robinsons, Bells, etc.
Others have multiples, ie:dauphins with 4, Hughes etc.
If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
What would happen if you had a 4, 5, or even 6 blade?Would you still be able
to autorotate? I know the airframe would probably vibrate violently, but
would it be survivable in an autorotate, or even low power to at least get
to the ground.
Have there been instances in the past where this has happened with a >2
blade.
Thanks in advance.
Rob Fonhof

[Gyroplanes]

>If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
>What would happen if you had a 4, 5, or even 6 blade?Would you still be able
>to autorotate?

The only thing I've ever heard about a survivable "blade loss incident" was on
an early autogiro (Pitcairn, I think) The test pilot lost one of the four main
rotorblades. The story has it that the opposing blade departed soon after the
first and he was able to sucessfully land.
I also remember that he never flew again.

Tom

[Stan Gosnell]

"Rob Fonhof" > wrote in
:

> Just a theoretical question that someone may be able to help with.
> Alot of helicopters have only two rotor blades, ie:Robinsons, Bells,
> etc. Others have multiples, ie:dauphins with 4, Hughes etc.
> If a blade is thrown on a two blade, bend over and kiss your rear bye
> bye. What would happen if you had a 4, 5, or even 6 blade?Would you
> still be able to autorotate? I know the airframe would probably
> vibrate violently, but would it be survivable in an autorotate, or
> even low power to at least get to the ground.
> Have there been instances in the past where this has happened with a
> >2 blade.

If you lose a blade, the imbalance will be so large as to take the
transmission and everything attached to it out of the aircraft, most
likely. It isn't survivable, just as losing a wing on an airplane isn't
survivable, except in the most unusual of circumstances.

--
Regards,

Stan

[Curious Question]

> Stan Gosnell > wrote:

> It isn't survivable, just as losing a wing on an airplane isn't
> survivable, except in the most unusual of circumstances.

Stan..... Do you have any idea as to how often a blade has been
thrown since the invention of the helicopter, gyro, etc.

How about in the last decade.

[Mike Th...]

A Hughes 369D lost a blade here in B.C. A few years back, it brought up a
whole bunch of issues with the blades.
Here is report:
http://www.tsb.gc.ca/en/reports/air/2000/a00P0208/a00P0208.asp

Mike


"Rob Fonhof" > wrote in message
...
> Just a theoretical question that someone may be able to help with.
> Alot of helicopters have only two rotor blades, ie:Robinsons, Bells, etc.
> Others have multiples, ie:dauphins with 4, Hughes etc.
> If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
> What would happen if you had a 4, 5, or even 6 blade?Would you still be
able
> to autorotate? I know the airframe would probably vibrate violently, but
> would it be survivable in an autorotate, or even low power to at least get
> to the ground.
> Have there been instances in the past where this has happened with a >2
> blade.
> Thanks in advance.
> Rob Fonhof
>
>
>

[Stan Gosnell]

Curious Question > wrote in
:

>> Stan Gosnell > wrote:
>
>> It isn't survivable, just as losing a wing on an airplane isn't
>> survivable, except in the most unusual of circumstances.
>
> Stan..... Do you have any idea as to how often a blade has been
> thrown since the invention of the helicopter, gyro, etc.
>
> How about in the last decade.

It's pretty seldom, I suspect about the same frequency as airplanes losing
wings. The only one I've heard of recently is a Sikorsky S76 which lost a
blade (actually the blade broke off relatively close to the head) over the
North Sea last year. All aboard were lost. The blade had been previously
hit by lightning, and this coupled with a manufacturing defect caused it to
fail. Losing a main rotor blade on a certificated helicopter is very rare,
unless it's in conjunction with a collision, where the blades hit something
and subsequently fail. I fly them for a living, and losing a MR blade is
something I just don't worry about.

The NTSB, and perhaps other national aviation safety agencies, publishes
summaries of all aviation accidents in the US, going back to 1962, and it's
searchable. You should be able to find what you're looking for there, at
least for the USA. http://www.ntsb.gov/aviation/aviation.htm

--
Regards,

Stan

[Hennie]

You will still have to bend over and kiss your behind and
I would suggest that you do it rather quick.



"Rob Fonhof" > wrote in message >...
> Just a theoretical question that someone may be able to help with.
> Alot of helicopters have only two rotor blades, ie:Robinsons, Bells, etc.
> Others have multiples, ie:dauphins with 4, Hughes etc.
> If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
> What would happen if you had a 4, 5, or even 6 blade?Would you still be able
> to autorotate? I know the airframe would probably vibrate violently, but
> would it be survivable in an autorotate, or even low power to at least get
> to the ground.
> Have there been instances in the past where this has happened with a >2
> blade.
> Thanks in advance.
> Rob Fonhof
>

[Helimech]

About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a M/R
blade loss. They were on approach, I seem to recall about 100 ft AGL, and
broke a TT strap (badly corroded). The M/R gearbox left the aircraft and all
3 souls were lost. This was the first time a blade had slung in the BO105
(same head) or BK117 history. Then I remember years ago Donald Trumps Agusta
A109 lost a blade up in NY with several of his VP's aboard. All were
killed. Then there were the M/R spindle problems with the S76 when it first
came out. Your right though, a M/R separation is very, very rare. JC

"Stan Gosnell" > wrote in message
...
> Curious Question > wrote in
> :
>
> >> Stan Gosnell > wrote:
> >
> >> It isn't survivable, just as losing a wing on an airplane isn't
> >> survivable, except in the most unusual of circumstances.
> >
> > Stan..... Do you have any idea as to how often a blade has been
> > thrown since the invention of the helicopter, gyro, etc.
> >
> > How about in the last decade.
>
> It's pretty seldom, I suspect about the same frequency as airplanes losing
> wings. The only one I've heard of recently is a Sikorsky S76 which lost a
> blade (actually the blade broke off relatively close to the head) over the
> North Sea last year. All aboard were lost. The blade had been previously
> hit by lightning, and this coupled with a manufacturing defect caused it
to
> fail. Losing a main rotor blade on a certificated helicopter is very
rare,
> unless it's in conjunction with a collision, where the blades hit
something
> and subsequently fail. I fly them for a living, and losing a MR blade is
> something I just don't worry about.
>
> The NTSB, and perhaps other national aviation safety agencies, publishes
> summaries of all aviation accidents in the US, going back to 1962, and
it's
> searchable. You should be able to find what you're looking for there, at
> least for the USA. http://www.ntsb.gov/aviation/aviation.htm
>
> --
> Regards,
>
> Stan
>

[Shaber CJ]

>Subject: Re: number of rotor blades
>From: Stan Gosnell

It isn't survivable, just as losing a wing on an airplane isn't
>survivable, except in the most unusual of circumstances.
>
>--
>Regards,
>
>Stan

I do know a an accident with a glider where the pilot lost a wing, spin down
into a marsh with big fluffy trees and survied. It happened in Florida a few
years ago and the glider was a 1-26.

Craig

[Stu Fields]

Hennie: With the vibration level you would have with a missing blade I
doubt if you could find your behind let alone aim a kiss at it. Having had
one just slip out of track in flight was enough to tell me I would have had
trouble kissing anything.
Stu Fields

"Hennie" > wrote in message
om...
> You will still have to bend over and kiss your behind and
> I would suggest that you do it rather quick.
>
>
>
> "Rob Fonhof" > wrote in message
>...
> > Just a theoretical question that someone may be able to help with.
> > Alot of helicopters have only two rotor blades, ie:Robinsons, Bells,
etc.
> > Others have multiples, ie:dauphins with 4, Hughes etc.
> > If a blade is thrown on a two blade, bend over and kiss your rear bye
bye.
> > What would happen if you had a 4, 5, or even 6 blade?Would you still be
able
> > to autorotate? I know the airframe would probably vibrate violently,
but
> > would it be survivable in an autorotate, or even low power to at least
get
> > to the ground.
> > Have there been instances in the past where this has happened with a >2
> > blade.
> > Thanks in advance.
> > Rob Fonhof
> >

[Sla#s]

"Rob Fonhof" > wrote in message
...
> Just a theoretical question that someone may be able to help with.
> Alot of helicopters have only two rotor blades, ie:Robinsons, Bells, etc.
> Others have multiples, ie:dauphins with 4, Hughes etc.
> If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
> What would happen if you had a 4, 5, or even 6 blade?Would you still be
able
> to autorotate? I know the airframe would probably vibrate violently, but
> would it be survivable in an autorotate, or even low power to at least get
> to the ground.
> Have there been instances in the past where this has happened with a >2
> blade.

Brantly B2s had a problem in the early '70s. I personally saw a blade come
off one. The other blades pulled the gearbox off the airframe. Two on board
but only one was killed as the machine was only at 20 ft.

Slatts

[Stan Gosnell]

"Helimech" > wrote in
:

> About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a
> M/R blade loss. They were on approach, I seem to recall about 100 ft
> AGL, and broke a TT strap (badly corroded). The M/R gearbox left the
> aircraft and all 3 souls were lost. This was the first time a blade
> had slung in the BO105 (same head) or BK117 history. Then I remember
> years ago Donald Trumps Agusta A109 lost a blade up in NY with several
> of his VP's aboard. All were killed. Then there were the M/R spindle
> problems with the S76 when it first came out. Your right though, a M/R
> separation is very, very rare. JC

I had forgotten about the Hermann ship. The BH206 also had TT strap
problems when it was new, and shucked a few blades, IIRC.

--
Regards,

Stan

[Stan Gosnell]

(Shaber CJ) wrote in
:

> I do know a an accident with a glider where the pilot lost a wing,
> spin down into a marsh with big fluffy trees and survied. It happened
> in Florida a few years ago and the glider was a 1-26.

A few people have survived parachute jumps when the chute didn't open, too,
but it's certainly not common. Anything is possible.

--
Regards,

Stan

[Helimech]

I guess that's why Bell still has the 2 year calendar life on their straps.
Bit of a overkill but I guess they never want to see those days again. JC

"Stan Gosnell" > wrote in message
...
> "Helimech" > wrote in
> :
>
> > About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a
> > M/R blade loss. They were on approach, I seem to recall about 100 ft
> > AGL, and broke a TT strap (badly corroded). The M/R gearbox left the
> > aircraft and all 3 souls were lost. This was the first time a blade
> > had slung in the BO105 (same head) or BK117 history. Then I remember
> > years ago Donald Trumps Agusta A109 lost a blade up in NY with several
> > of his VP's aboard. All were killed. Then there were the M/R spindle
> > problems with the S76 when it first came out. Your right though, a M/R
> > separation is very, very rare. JC
>
> I had forgotten about the Hermann ship. The BH206 also had TT strap
> problems when it was new, and shucked a few blades, IIRC.
>
> --
> Regards,
>
> Stan
>

[Micbloo]

>> About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a
>> M/R blade loss. They were on approach, I seem to recall about 100 ft
>> AGL, and broke a TT strap (badly corroded). The M/R gearbox left the
>> aircraft and all 3 souls were lost.

And caused the subsequent grounding
of many BK117s in the EMS community
as they had to do an inspection. But I think most ships were quickly back in
service.

[[email protected]]

Losing a MR blade in flight results in certain death, but what about
having a blade delaminate? That is, part of the skin comes off but
the main chord is still attached?

Dennis.


Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[Helimech]

Well its a rough ride down but definitely controllable. The BK117 has had
this happen numerous times (I would guess about 15 times, all landed
safely). The engine cowling is being left unlatched (this is not the
mechanics or pilots story) and is coming open in flight striking the M/R
blades. The M/R blades tear the cowling off the airframe and upward into
the rotor system. The result is almost always large sections of M/R
skin/foam being ripped off a blade or two. I've seen several BK blades that
had 3 foot sections missing, from the spar back. The worst one I ever saw
was an Omniflight BK that lost the last 6-8 feet of the Skin/foam off 1
blade. All that was left on the outer 6-8 feet of one blade was the spar.
Like swinging a stick around. The pilot did a great run on landing in some
frozen field but he said everything was just a blur all the way down from
the imbalance. I've heard many stories of aircraft loosing large parts of
blades (shot off) in Vietnam. It livable if you just loose the light stuff.
Most of the weight is spar and metal eroision strip, thats the stuff you
want to keep onboard. I've been looking thru my stuff since this tread
started looking for a weight figure I read one time on what the centrifical
load was on a 206 M/R blade but can't find it. I remember it was a whole
lot more force than I ever would have guessed. Made me respect for the
strength of those TT straps.JC

> wrote in message
...
>
> Losing a MR blade in flight results in certain death, but what about
> having a blade delaminate? That is, part of the skin comes off but
> the main chord is still attached?
>
> Dennis.
>
>
> Dennis Hawkins
> n4mwd AT amsat DOT org (humans know what to do)
>
> "A RECESSION is when you know somebody who is out of work.
> A DEPRESSION is when YOU are out of work.
> A RECOVERY is when all the H-1B's are out of work."
> To find out what an H-1B is and how they are putting
> Americans out of work, visit the following web site
> and click on the "Exporting America" CNN news video:
> http://zazona.com/ShameH1B/MediaClips.htm
>

[John Roncallo]

Rob Fonhof wrote:

> Just a theoretical question that someone may be able to help with.
> Alot of helicopters have only two rotor blades, ie:Robinsons, Bells, etc.
> Others have multiples, ie:dauphins with 4, Hughes etc.
> If a blade is thrown on a two blade, bend over and kiss your rear bye bye.
> What would happen if you had a 4, 5, or even 6 blade?Would you still be able
> to autorotate? I know the airframe would probably vibrate violently, but
> would it be survivable in an autorotate, or even low power to at least get
> to the ground.
> Have there been instances in the past where this has happened with a >2
> blade.
> Thanks in advance.
> Rob Fonhof
>
>
>

I did see some article (I don t know where) stating the Sikorsky S-61
could survive a thrown blade. I find this hard to believe, since
throwing a blade would create an enormous out of balance on the order of
60,000 lb at about 5 Hz. If the ship remained in one piece and weighed
20,000 Lb. The pilot would feel the equivalent of someone shaking them
back and forth 5 time per second at 3 g's or more if it were empty. I
see a persons neck breaking in a short time. And in fact this is usually
the scenario I've been told. If you throw a blade the ocupants will be
dead before the aircraft hits the ground.

Opinions posted here are my own and do not represent the company I work for.

John Roncallo

[Dave Jackson]

Sikorsky has a couple of patents for 'Rotor system having alternating length
rotor blades'. [U.S. patent #5,620,303]

This is not to suggest that the removal of a portion of the blade on the
ground is the same as the removal of a portion of the blade in the air.


"Shaber CJ" > wrote in message
...
> >Subject: Re: number of rotor blades
> >From: Stan Gosnell
>
> It isn't survivable, just as losing a wing on an airplane isn't
> >survivable, except in the most unusual of circumstances.
> >
> >--
> >Regards,
> >
> >Stan
>
> I do know a an accident with a glider where the pilot lost a wing, spin
down
> into a marsh with big fluffy trees and survied. It happened in Florida a
few
> years ago and the glider was a 1-26.
>
> Craig

[[email protected]]

I had heard that the centrifugal load on the hub from the blade is
something like 25,000 lbs for a small helicopter. I'm sure that there
is a formula somewhere that takes the total weight of the blade, the
RPM and the length. I don't have it though. I'd have to brush up on
my calculus to figure out the formula. I'm sure that someone here
probably has it already figured out.

Dennis.

"Helimech" > wrote:

> blades (shot off) in Vietnam. It livable if you just loose the light stuff.
> Most of the weight is spar and metal eroision strip, thats the stuff you
> want to keep onboard. I've been looking thru my stuff since this tread
> started looking for a weight figure I read one time on what the centrifical
> load was on a 206 M/R blade but can't find it. I remember it was a whole
> lot more force than I ever would have guessed. Made me respect for the
> strength of those TT straps.JC


Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[Hennie]

The centrifugal force generated by a rotor blade
is (W*r*rpm^2)/2900 W is the blade weight. r is the distance from
the hub center to the CG of the blade

[[email protected]]

Thanks for posting the formula. Let me see if I understand it
correctly. For the hypothetical small helicopter:

Blades are 10' long and the cg is half the length (no tip weights). R
would be 5' plus the distance from the center of the shaft to the
blade mounts. I'll call R as being 5.5' in this example.

I'll say the blades are 25 lbs each and the RPM is 600 (450 MPH tip
speed).

FORCE = (W * R * RPM^2) / 2900 = (25 * 5.5 * 600^2) / 2900
= 17069 lbs.

This is assuming that the units are supposed to be lbs and feet.

The result is less than I thought, but still pretty impressive.

By adding 2 lb tip weights, the CG force increases to about 23,500
lbs. That's a pretty big jump, but the biggest jumps obviously come
with the RPM.

Did I do it right?

Dennis.


(Hennie) wrote:

> The centrifugal force generated by a rotor blade
> is (W*r*rpm^2)/2900 W is the blade weight. r is the distance from
> the hub center to the CG of the blade

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[Cam]

Hi, I was wondering if there was a simplified formula for working out
centrifugal force with a constant mass rotor.
Unfortunately I can't make sence of it, what is the constant 2900 derived
from?
When using, F= MV^2/r
F= force
M= mass
V= velocity
r= radius
By summing each calculation -- say at r=1m, 'X'm/s,M=1Kg
r=2m
'X'm/s,M=2Kg
and so on .(the smaller the increments the better)
The end result is not even close to the formentioned formula.
Where have I gone wrong?

Cheers Cam
(excuse the metric system)

"Hennie" > wrote in message
om...
> The centrifugal force generated by a rotor blade
> is (W*r*rpm^2)/2900 W is the blade weight. r is the distance from
> the hub center to the CG of the blade

[[email protected]]

Just guessing, but your formula uses Velocity and his uses RPM. The
2900 is probably due to the conversion of RPM to velocity in Miles Per
Hour.

V = (2*R*RPM)/28 (where units are V=Miles Per Hour, R=Feet)

Also, your formula is apparently using Kg's and M's instead of Feet
and pounds. Then again, I may be totally wrong as CAC is from South
Africa and they use the metric system too. (I know this because I did
a search for apartments in South Africa and all the square 'footage's
were in square meters.)

It would help if somebody would say for sure what the units are.

Dennis.

"Cam" > wrote:

> Hi, I was wondering if there was a simplified formula for working out
> centrifugal force with a constant mass rotor.
> Unfortunately I can't make sence of it, what is the constant 2900 derived
> from?
> When using, F= MV^2/r
> F= force
> M= mass
> V= velocity
> r= radius
> By summing each calculation -- say at r=1m, 'X'm/s,M=1Kg
> r=2m
> 'X'm/s,M=2Kg
> and so on .(the smaller the increments the better)
> The end result is not even close to the formentioned formula.
> Where have I gone wrong?
>
> Cheers Cam
> (excuse the metric system)
>
> "Hennie" > wrote in message
> om...
> > The centrifugal force generated by a rotor blade
> > is (W*r*rpm^2)/2900 W is the blade weight. r is the distance from
> > the hub center to the CG of the blade
>
>

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[Bob]

IN CLARIFICATION TO THE ABOVE:

THAT WAS NOT "DONALD TRUMP'S AGUSTA THAT WAS LOST IN THE ACCIDENT UP IN NEW
JERSEY. THAT AIRCRAFT WAS LEASED THAT DAY FROM PARAMOUNT AVIATION. TRUMP
HAD FIVE (5) OF HIS L A R G E HELICOPTERS SITTING IN THE HANGAR ON THE DAY
THAT THE LEASED AIRCRAFT WAS LOST.

I WAS THE CHIEF INSPECTOR FOR TRUMPS HELICOPTER OPERATIONS AT THE TIME SO
YOU CAN TAKE THIS INFO TO THE BANK. HIS AGUSTA 109 WAS IN MAINTENANCE THAT
DAY AND WAS UNAVAILABLE. THE BLADE THAT FAILED HAD A "FORGING LAP": LEFT IN
THE M/R/B SPAR SINCE MANUFACTURE WHICH CREATED A "STRESS RAISER", EVENTUALLY
A CRACK, AND THE REST IS HISTORY. For the rest of the commenters, now with
many composite blades out there a better record can probably be expected
although no great inspection methods have yet been developed for composites.
Metal blades departed aircraft many many times, hence Sikorsky's "BIM"
indicators on the blade roots. Hundreds of thousands od pounds of
centrifugal force and cracked blades will always present a problem, huh?

[Hennie]

I got the formula in the rotorcraft forum. If i remember correctly
it was written by Chuck Beaty
The units is in pounds and feet, thus imperial.
Yes we use the metric system but I was still brought up with the
imperial system so I still think that way.

Regards

Hennie


wrote in message >...
> Just guessing, but your formula uses Velocity and his uses RPM. The
> 2900 is probably due to the conversion of RPM to velocity in Miles Per
> Hour.
>
> V = (2*R*RPM)/28 (where units are V=Miles Per Hour, R=Feet)
>
> Also, your formula is apparently using Kg's and M's instead of Feet
> and pounds. Then again, I may be totally wrong as CAC is from South
> Africa and they use the metric system too. (I know this because I did
> a search for apartments in South Africa and all the square 'footage's
> were in square meters.)
>
> It would help if somebody would say for sure what the units are.
>
> Dennis.
>
> "Cam" > wrote:
>
> > Hi, I was wondering if there was a simplified formula for working out
> > centrifugal force with a constant mass rotor.
> > Unfortunately I can't make sence of it, what is the constant 2900 derived
> > from?
> > When using, F= MV^2/r
> > F= force
> > M= mass
> > V= velocity
> > r= radius
> > By summing each calculation -- say at r=1m, 'X'm/s,M=1Kg
> > r=2m
> > 'X'm/s,M=2Kg
> > and so on .(the smaller the increments the better)
> > The end result is not even close to the formentioned formula.
> > Where have I gone wrong?
> >
> > Cheers Cam
> > (excuse the metric system)
> >
> > "Hennie" > wrote in message
> > om...
> > > The centrifugal force generated by a rotor blade
> > > is (W*r*rpm^2)/2900 W is the blade weight. r is the distance from
> > > the hub center to the CG of the blade
> >
> >
>
> Dennis Hawkins
> n4mwd AT amsat DOT org (humans know what to do)
>
> "A RECESSION is when you know somebody who is out of work.
> A DEPRESSION is when YOU are out of work.
> A RECOVERY is when all the H-1B's are out of work."
> To find out what an H-1B is and how they are putting
> Americans out of work, visit the following web site
> and click on the "Exporting America" CNN news video:
> http://zazona.com/ShameH1B/MediaClips.htm

[Cam]

Whooops, I used the radius instead of the CoG of one blade (approx 1/2
radius).
Now it works, far easier than my approach.
Thanks.

ps/ I like to use both metric and imperial as well, it comes in handy when
building international space stations (I'm sure)

Cheers Cam

[[email protected]]

Its probably the same formula used to calculate how fast the space
station must rotate in order to create artificial gravity. Now if the
space station actually did that, it would be really cool.

Dennis.

"Cam" > wrote:

> ps/ I like to use both metric and imperial as well, it comes in handy when
> building international space stations (I'm sure)
>
> Cheers Cam
>
>

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[[email protected]]

Forgive my ignorance, but I need some clarification on your
clarification. Describe exactly what a 'forging lap' is. What do I
look for when inspecting a blade? Can it be seen outright, or is an
X-ray necessary?

Also, I thought that composite blades still used a metal spar. Is
this not correct. If not, please describe their construction.

Dennis.

"Bob" > wrote:

> I WAS THE CHIEF INSPECTOR FOR TRUMPS HELICOPTER OPERATIONS AT THE TIME SO
> YOU CAN TAKE THIS INFO TO THE BANK. HIS AGUSTA 109 WAS IN MAINTENANCE THAT
> DAY AND WAS UNAVAILABLE. THE BLADE THAT FAILED HAD A "FORGING LAP": LEFT IN
> THE M/R/B SPAR SINCE MANUFACTURE WHICH CREATED A "STRESS RAISER", EVENTUALLY
> A CRACK, AND THE REST IS HISTORY. For the rest of the commenters, now with
> many composite blades out there a better record can probably be expected
> although no great inspection methods have yet been developed for composites.
> Metal blades departed aircraft many many times, hence Sikorsky's "BIM"
> indicators on the blade roots. Hundreds of thousands od pounds of
> centrifugal force and cracked blades will always present a problem, huh?
>
>
>
>

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

[Bob]

Unfortunately, my clarification, specifically as to the cause of the
Agusta109 main rotor blade separation is in error. In that particular case,
I was informed that at manufacture too much bonding material was applied to
a weight that is bonded inside of the spar to achieve balance to
manufacturing tolerances. That excess bonding material was "scraped" out
leaving a tooling mark that eventually led to the crack.

Now to briefly answer your questions:
A "Forging Lap" is a flap of metal that should not be present after a
forging or hammering type of process. Those spars are not forged, they are
extruded (pushed or pulled through a die). Typically, manufacturing defects
are not as blatent as to be seen by the naked eye, and many times are inside
of the spar requiring x-ray, eddy current, or some other form of
non-destructive detection.

Composite (meaning totally composite) main rotor blades do not have a metal
spar. Some newer composite main rotor blades incorporate a carbon fibre
reinforced plastic spar and are filled with a Nomex honeycomb material. The
blades are corrosion and damage resistant. Sorry for my error.

[John Roncallo]

Dave Jackson wrote:
> Sikorsky has a couple of patents for 'Rotor system having alternating length
> rotor blades'. [U.S. patent #5,620,303]
>
> This is not to suggest that the removal of a portion of the blade on the
> ground is the same as the removal of a portion of the blade in the air.
>
>

I can garantee that any of these designs still keep the rotor system
balanced.

[Helimech]

SORRY BOB! GUESS MY MEMORY IS FAILING. HOW COULD I FORGET THAT THE
AIRCRAFT THAT DONALD'S PEOPLE WERE USING THAT DAY BACK IN 1989 WAS LEASED
AND NOT OWNED BY TRUMP. I DIDN'T REALIZE THAT THE ACTUAL OWNERSHIP OF THE
AIRCRAFT WAS REALLY THAT CRITICAL TO THIS THREAD ON M/R BLADE FAILURES. ONE
WOULD THINK THAT YOU WOULD HAVE REMEMBERED THE CAUSE OF THE FAILURE AND NOT
HAVE THROWN OUT THAT "FORGING LAP" AS THE CAUSE. huh? JC

"Bob" > wrote in message
...
> IN CLARIFICATION TO THE ABOVE:
>
> THAT WAS NOT "DONALD TRUMP'S AGUSTA THAT WAS LOST IN THE ACCIDENT UP IN
NEW
> JERSEY. THAT AIRCRAFT WAS LEASED THAT DAY FROM PARAMOUNT AVIATION. TRUMP
> HAD FIVE (5) OF HIS L A R G E HELICOPTERS SITTING IN THE HANGAR ON THE
DAY
> THAT THE LEASED AIRCRAFT WAS LOST.
>
> I WAS THE CHIEF INSPECTOR FOR TRUMPS HELICOPTER OPERATIONS AT THE TIME SO
> YOU CAN TAKE THIS INFO TO THE BANK. HIS AGUSTA 109 WAS IN MAINTENANCE
THAT
> DAY AND WAS UNAVAILABLE. THE BLADE THAT FAILED HAD A "FORGING LAP": LEFT
IN
> THE M/R/B SPAR SINCE MANUFACTURE WHICH CREATED A "STRESS RAISER",
EVENTUALLY
> A CRACK, AND THE REST IS HISTORY. For the rest of the commenters, now
with
> many composite blades out there a better record can probably be expected
> although no great inspection methods have yet been developed for
composites.
> Metal blades departed aircraft many many times, hence Sikorsky's "BIM"
> indicators on the blade roots. Hundreds of thousands od pounds of
> centrifugal force and cracked blades will always present a problem, huh?
>
>
>
>

[Bob]

Hey JC er...excuse me HELIMECH

If you had followed the thread you would have seen that the EXACT CAUSE of
the MRB FAILURE WAS CLARIFIED BY ME, not that I would suspect that you might
have caught it seeing that you're still mentioning a "forging lap". The
executives lost in that flight, were known by me and it was QUITE ironic
that they lost their lives in a chartered aircraft. DESPITE YOUR OBJECTION
to my clarification as to the aircrft owner I'm SURE I presented more
factual information as to the cause of that Main Rotor Blade failure, and
others, than any other contributer to that particular subject. By the
way...refresh my memory as to the contextual wisdom of whatever you may have
CONTRIBUTED.

Bob

[Helimech]

My objection was not your clarification to the owners it was the WAY IT WAS
TYPED. Must be a QA thing. JC

"Bob" > wrote in message
.. .
> Hey JC er...excuse me HELIMECH
>
> If you had followed the thread you would have seen that the EXACT CAUSE of
> the MRB FAILURE WAS CLARIFIED BY ME, not that I would suspect that you
might
> have caught it seeing that you're still mentioning a "forging lap". The
> executives lost in that flight, were known by me and it was QUITE ironic
> that they lost their lives in a chartered aircraft. DESPITE YOUR OBJECTION
> to my clarification as to the aircrft owner I'm SURE I presented more
> factual information as to the cause of that Main Rotor Blade failure, and
> others, than any other contributer to that particular subject. By the
> way...refresh my memory as to the contextual wisdom of whatever you may
have
> CONTRIBUTED.
>
> Bob
>
>

[Bob]

JC...
Your point is humbly acknowledged. I really have to stop HOLLARING every
one of the buzillion times somebody says sommething like "hey remember when
TRUMP's Agusta crashed?" Considering that my name is plastered all over
that lAgusta's logbook, and as far as I know it's still tooling around
someplace, you might understand why it kinda ruffles my feathers.
Bob

[Helimech]

Completely understand. If its any consolation I will now never forget that
it was indeed a leased aircraft. (course I'm getting old and the my memory
is not quite what it used to be but I'll try) Cheers, JC

"Bob" > wrote in message
...
> JC...
> Your point is humbly acknowledged. I really have to stop HOLLARING every
> one of the buzillion times somebody says sommething like "hey remember
when
> TRUMP's Agusta crashed?" Considering that my name is plastered all over
> that lAgusta's logbook, and as far as I know it's still tooling around
> someplace, you might understand why it kinda ruffles my feathers.
> Bob
>
>

[[email protected]]

"Helimech" > wrote:

> About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a M/R
> blade loss. They were on approach, I seem to recall about 100 ft AGL, and
> broke a TT strap (badly corroded). The M/R gearbox left the aircraft and all
> 3 souls were lost.

Ok another question. What is a TT strap?

Dennis.


Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm

[Helimech]

The Tension-Torsion (TT) straps are basically 2 bushings a certain distance
apart connected together by thousands of turns (I've heard something like
12,000 turns) of stainless steel wire (around .020" dia.), sealed in a
plastic like covering. These straps (one for each blade) are what hold the
main rotor blades to the rotor hub. The straps have to handle the huge
centrifugal loads (tension) of the blade but still allow for pitch (torsion)
control inputs from the pilot. Here is a link to Lord Corporation and a
picture of some TT straps. Lord is the present manufacture of the straps
for the BK117 and BO105. The strap that failed in Houston was made by
Bendix. http://www.lordmpd.com/aerospace/rotary_wing/tension_straps.asp

Hope this helps, I'm sure someone could describe a TT strap better but this
is the best I can do this early in the morning. JC



> wrote in message
...
> "Helimech" > wrote:
>
> > About 2 years ago Herman Hospital in Houston, TX lost a BK117 due to a
M/R
> > blade loss. They were on approach, I seem to recall about 100 ft AGL,
and
> > broke a TT strap (badly corroded). The M/R gearbox left the aircraft and
all
> > 3 souls were lost.
>
> Ok another question. What is a TT strap?
>
> Dennis.
>
>
> Dennis Hawkins
> n4mwd AT amsat DOT org (humans know what to do)
>
> "A RECESSION is when you know somebody who is out of work.
> A DEPRESSION is when YOU are out of work.
> A RECOVERY is when all the H-1B's are out of work."
>
> To find out what an H-1B is and how Congress is using
> them to put Americans out of work, visit the following
> web site and click on the "Exporting America" CNN news
> video: http://zazona.com/ShameH1B/MediaClips.htm
>

[[email protected]]

Having a picture certainly helps, but I'm still confused as to where
exactly that they go. First, are we talking about a semi-rigid or
fully articulated or other hub?

Essentially, it looks a lot like a box end wrench. However, in
function, it sounds a lot like an elastomeric bearing.

Do you know of any closeup photos with TT straps installed on the hub?

Dennis.


"Helimech" > wrote:

> The Tension-Torsion (TT) straps are basically 2 bushings a certain distance
> apart connected together by thousands of turns (I've heard something like
> 12,000 turns) of stainless steel wire (around .020" dia.), sealed in a
> plastic like covering. These straps (one for each blade) are what hold the
> main rotor blades to the rotor hub. The straps have to handle the huge
> centrifugal loads (tension) of the blade but still allow for pitch (torsion)
> control inputs from the pilot. Here is a link to Lord Corporation and a
> picture of some TT straps. Lord is the present manufacture of the straps
> for the BK117 and BO105. The strap that failed in Houston was made by
> Bendix. http://www.lordmpd.com/aerospace/rotary_wing/tension_straps.asp
>
> Hope this helps, I'm sure someone could describe a TT strap better but this
> is the best I can do this early in the morning. JC
>
>
>

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm

[Bill Chernoff]

look here:
http://www.star-techno.com/clsc/206B%20hub.gif

[Bill Chernoff]

Can anyone identify which helos use elastomeric
bearings in the rotor hub.

As a bonus, can anyone post an exploded view?

Thanks
Bill

[Helimech]

Your right, pictures are great. The problem is with the head assembled you
can't see the TT strap. I'll e-mail you some pictures from the BK117
(semi-rigid) head scanned from the Maintenance Manual and the Part Catalog
and also the same for the A109A/AII (fully articulated) head. JC

> wrote in message
...
>
> Having a picture certainly helps, but I'm still confused as to where
> exactly that they go. First, are we talking about a semi-rigid or
> fully articulated or other hub?
>
> Essentially, it looks a lot like a box end wrench. However, in
> function, it sounds a lot like an elastomeric bearing.
>
> Do you know of any closeup photos with TT straps installed on the hub?
>
> Dennis.
>
>
> "Helimech" > wrote:
>
> > The Tension-Torsion (TT) straps are basically 2 bushings a certain
distance
> > apart connected together by thousands of turns (I've heard something
like
> > 12,000 turns) of stainless steel wire (around .020" dia.), sealed in a
> > plastic like covering. These straps (one for each blade) are what hold
the
> > main rotor blades to the rotor hub. The straps have to handle the huge
> > centrifugal loads (tension) of the blade but still allow for pitch
(torsion)
> > control inputs from the pilot. Here is a link to Lord Corporation and a
> > picture of some TT straps. Lord is the present manufacture of the
straps
> > for the BK117 and BO105. The strap that failed in Houston was made by
> > Bendix. http://www.lordmpd.com/aerospace/rotary_wing/tension_straps.asp
> >
> > Hope this helps, I'm sure someone could describe a TT strap better but
this
> > is the best I can do this early in the morning. JC
> >
> >
> >
>
> Dennis Hawkins
> n4mwd AT amsat DOT org (humans know what to do)
>
> "A RECESSION is when you know somebody who is out of work.
> A DEPRESSION is when YOU are out of work.
> A RECOVERY is when all the H-1B's are out of work."
>
> To find out what an H-1B is and how Congress is using
> them to put Americans out of work, visit the following
> web site and click on the "Exporting America" CNN news
> video: http://zazona.com/ShameH1B/MediaClips.htm
>

[Helimech]

Well I'm going to miss some but the ones I can think of are:
Eurocopters-AS350, AS355, AS365, EC120, EC130. Agusta-A109E, A119 and the
AB139. Bell-407, 427 and maybe Bells big aircraft, I don't know.
Sikorsky-S76. That's all I can think of right now. JC


"Bill Chernoff" > wrote in message
news:5HLDb.732201$9l5.488178@pd7tw2no...
> Can anyone identify which helos use elastomeric
> bearings in the rotor hub.
>
> As a bonus, can anyone post an exploded view?
>
> Thanks
> Bill
>
>

[Stan Gosnell]

"Helimech" > wrote in
news:kgODb.410428$ao4.1341495@attbi_s51:

> Well I'm going to miss some but the ones I can think of
> are: Eurocopters-AS350, AS355, AS365, EC120, EC130.
> Agusta-A109E, A119 and the AB139. Bell-407, 427 and maybe
> Bells big aircraft, I don't know.

The 412 uses elastomeric bearings.

--
Regards,

Stan

[Helimech]

I was a "small" ship mech back in the early 70's at PHI and have always
tried to steer clear of the heavy metal stuff so don't know too much about
them. Always felt it too far to slip and fall from the deck. Had a feeling
the 412 used elastomeric but wasn't sure. What does the 430 have?

JC

"Stan Gosnell" <me@work> wrote in message
...
> "Helimech" > wrote in
> news:kgODb.410428$ao4.1341495@attbi_s51:
>
> > Well I'm going to miss some but the ones I can think of
> > are: Eurocopters-AS350, AS355, AS365, EC120, EC130.
> > Agusta-A109E, A119 and the AB139. Bell-407, 427 and maybe
> > Bells big aircraft, I don't know.
>
> The 412 uses elastomeric bearings.
>
> --
> Regards,
>
> Stan

[Stan Gosnell]

"Helimech" > wrote in
news:fARDb.374117$Dw6.1220465@attbi_s02:

> I was a "small" ship mech back in the early 70's at PHI and
> have always tried to steer clear of the heavy metal stuff
> so don't know too much about them. Always felt it too far
> to slip and fall from the deck. Had a feeling the 412 used
> elastomeric but wasn't sure. What does the 430 have?

No idea. I think they're mechanical, but I've never seen one up
close.

--
Regards,

Stan

[Stan Gosnell]

Stan Gosnell <me@work> wrote in
:

> "Helimech" > wrote in
> news:fARDb.374117$Dw6.1220465@attbi_s02:
>
>> I was a "small" ship mech back in the early 70's at PHI
>> and have always tried to steer clear of the heavy metal
>> stuff so don't know too much about them. Always felt it
>> too far to slip and fall from the deck. Had a feeling the
>> 412 used elastomeric but wasn't sure. What does the 430
>> have?
>
> No idea. I think they're mechanical, but I've never seen
> one up close.
>

Wait, you said 430, not 230. Probably elastomeric, but I've
never seen one up close. ;-)

--
Regards,

Stan

[Dave Jackson]

> As a bonus, can anyone post an exploded view?

This web page has some exploded views. Click on the 3 small pictures, which
are located 1/4 of the way down the page.
http://www.UniCopter.com/0798.html

Dave J

[[email protected]]

The diagram posted here was a lot better. I can see how it fits
inside the cones. I didn't know that they did it that way. I thought
the cones just had a big bolt down the center of them like the one on
the R22. I guess this just prooves that there is more than one way to
skin a cat.

Dennis.

"Helimech" > wrote:

> Your right, pictures are great. The problem is with the head assembled you
> can't see the TT strap. I'll e-mail you some pictures from the BK117
> (semi-rigid) head scanned from the Maintenance Manual and the Part Catalog
> and also the same for the A109A/AII (fully articulated) head. JC
>
>
Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm