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number of rotor blades



 
 
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  #1  
Old November 26th 03, 03:51 AM
Rob Fonhof
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Default number of rotor blades

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



  #2  
Old November 26th 03, 05:39 AM
Gyroplanes
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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
  #3  
Old November 26th 03, 05:51 AM
Stan Gosnell
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"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

  #4  
Old November 26th 03, 06:01 AM
Curious Question
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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.
  #5  
Old November 26th 03, 06:16 AM
Mike Th...
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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/...8/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





  #6  
Old November 26th 03, 06:47 AM
Stan Gosnell
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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

  #7  
Old November 26th 03, 07:40 AM
Hennie
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Default

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

  #8  
Old November 26th 03, 03:17 PM
Helimech
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Default

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



  #9  
Old November 26th 03, 04:26 PM
Shaber CJ
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Default

Subject: 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
  #10  
Old November 26th 03, 04:58 PM
Stu Fields
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Default

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



 




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