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

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

"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

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.

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

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

"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

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?

"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)

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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