| Topic: |
Science > Physics |
| User: |
"BllFs6" |
| Date: |
03 Apr 2004 06:19:04 PM |
| Object: |
Physics of Helicopter rotor striking ground...? |
Hi all
Have developed an interest in small gyrocopters....
Anyway, one of the ways these things kill you is this.....
During the landing, due to rough ground, breaking wheels, wind gust or pilot
error the craft tips over and one tip of the spining rotor strikes the
ground...
When that happens, all that energy stored in the spinning rotor gets converted
into a horizontal force that either flings the whole vehicle sideways violently
and or rips the mast that supports the rotor out of the craft....either way
often seriously hurting or killing the passenger.....
So, my question is.....assume a 2 blade rotor of uniform density spinning
about its center at RPM XX......now assume one end strikes the ground and
"sticks" (stops dead in the dirt)......so how much force/momentum/whatever is
now applied to the mast that supported the rotor and is attacted at the center
of the rotor?
thanks
take care
Blll
.
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| User: "Richard Henry" |
|
| Title: Re: Physics of Helicopter rotor striking ground...? |
03 Apr 2004 06:27:40 PM |
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"BllFs6" <bllfs6@aol.com> wrote in message
news:20040403191904.29754.00000656@mb-m11.aol.com...
Hi all
Have developed an interest in small gyrocopters....
Anyway, one of the ways these things kill you is this.....
During the landing, due to rough ground, breaking wheels, wind gust or
pilot
error the craft tips over and one tip of the spining rotor strikes the
ground...
When that happens, all that energy stored in the spinning rotor gets
converted
into a horizontal force that either flings the whole vehicle sideways
violently
and or rips the mast that supports the rotor out of the craft....either
way
often seriously hurting or killing the passenger.....
So, my question is.....assume a 2 blade rotor of uniform density spinning
about its center at RPM XX......now assume one end strikes the ground and
"sticks" (stops dead in the dirt)......so how much force/momentum/whatever
is
now applied to the mast that supported the rotor and is attacted at the
center
of the rotor?
I assume (based on some limited experience) that the blade would shatter or
detach from the hub.
.
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| User: "davidoff404" |
|
| Title: Re: Physics of Helicopter rotor striking ground...? |
03 Apr 2004 11:23:46 PM |
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BllFs6 wrote:
Hi all
Have developed an interest in small gyrocopters....
Anyway, one of the ways these things kill you is this.....
During the landing, due to rough ground, breaking wheels, wind gust or pilot
error the craft tips over and one tip of the spining rotor strikes the
ground...
When that happens, all that energy stored in the spinning rotor gets converted
into a horizontal force that either flings the whole vehicle sideways violently
and or rips the mast that supports the rotor out of the craft....either way
often seriously hurting or killing the passenger.....
So, my question is.....assume a 2 blade rotor of uniform density spinning
about its center at RPM XX......now assume one end strikes the ground and
"sticks" (stops dead in the dirt)......so how much force/momentum/whatever is
now applied to the mast that supported the rotor and is attacted at the center
of the rotor?
Assuming also that the rotation occurs at RPM XX for very large values
of XX, it's extremely unlikely that the rotor will not shear at some
point due to a stress fracture upon hitting the ground. However,
supposing that your question requires an infinitely strong rotor which
*will not* break, the answer to your question is simple: the force on
the mast depends mainly on the rate of rotation and the distance between
the point of impact and the mast. Give us some numbers (tensile strength
of the material from which the mast is made, angular velocity of the
blades, mass of the blades, and mass of the fuselage to which the mast
is attached) and we'll give you some answers.
By the way, rotor blades on modern turbine helicopters are designed to
shear off easily upon impact since it's a hell of a lot less dangerous
to the occupants to have shards of rotor flying around than it is to
have a whole engine assembly ripping out of the fuselage and through the
cockpit.
.
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