On 6 Jun 2005 09:48:03 -0500, Dave wrote:

On Mon, 06 Jun 2005 08:01:55 -0400, Gogarty said:

A freewheeling propeller creates more drag than a locked on.. Just
consider a helicopter. Engine out and rotors freewheeling, the aircraft
will go down safely. Rotors locked and it drops like a stone.

Bad analogy. In a helicopter when the rotors are freewheeling after the
engine dies they're still rotating in a direction that generates lift.


Hmmmm, so Dave feels that a boat prop will reverse direction if the
drive is placed in neutral from forward, while under way?

Brian Whatcott Altus, OK

"Brian Whatcott" skrev i en
meddelelse
...
On 6 Jun 2005 09:48:03 -0500, Dave
wrote:

On Mon, 06 Jun 2005 08:01:55 -0400, Gogarty
said:

A freewheeling propeller creates more drag than a locked
on.. Just
consider a helicopter. Engine out and rotors
freewheeling, the aircraft
will go down safely. Rotors locked and it drops like a
stone.

Bad analogy. In a helicopter when the rotors are
freewheeling after the
engine dies they're still rotating in a direction that
generates lift.


Hmmmm, so Dave feels that a boat prop will reverse
direction if the
drive is placed in neutral from forward, while under way?

Brian Whatcott Altus, OK

Being a sailor with no experience with aviation, I do not
understand the helicopter analogy.
In my opinion, a helicopter driven by the engine corresponds
in my understanding to a sailboat, where the propeller is
set to drive the boat *backwards* ..... When the propeller
on the boat 'gets the chance' to run without the force of
the motor, that is just sailing forward by sail, I expect
the propeller to turn in the opposite direction ... that is
'forward' ... If that happens in a helicopter, I would
expect the helicopter to hit the ground very fast ... don't
you? I do not assume, that there is a lot of inertia in a
propeller or shaft en a sailboat - may be that is the case
in a helicopter, and that could explain the smooth landing
without the assistance from the motor - or I'm I completely
wrong here? ...

--
Flemming Torp

In article , "Flemming
Torp" fletopkanelbolle2rp.danmark says...
Being a sailor with no experience with aviation, I do not
understand the helicopter analogy.
In my opinion, a helicopter driven by the engine corresponds
in my understanding to a sailboat, where the propeller is
set to drive the boat *backwards* ..... When the propeller
on the boat 'gets the chance' to run without the force of
the motor, that is just sailing forward by sail, I expect
the propeller to turn in the opposite direction ... that is
'forward' ... If that happens in a helicopter, I would
expect the helicopter to hit the ground very fast ... don't
you? I do not assume, that there is a lot of inertia in a
propeller or shaft en a sailboat - may be that is the case
in a helicopter, and that could explain the smooth landing
without the assistance from the motor - or I'm I completely
wrong here? ...



The boat prop continues to turn in the same direction as it did when it
was the method of propulsion since there is no change in direction of
the water flow. In other words nothing forcing it to counter rotate.

In the case of the helicopter technically you are correct and a reversal
of direction would change the rotation of the blades. However the rotors
are connected to the engine via gears and can only rotate in the "lift"
direction. When the helicopter starts to fall due to loss of power the
rotors, slowed buy the drag of gears and engine, are forced to spin in
the lift direction causing "drag" that slows the copter to a rate where
impact with the ground is, at least, survivable.



--
Mike G.
Heirloom Woods

www.heirloom-woods.net

"Mike G" skrev i en meddelelse
ews.com...
In article ,
"Flemming
Torp" fletopkanelbolle2rp.danmark says...
Being a sailor with no experience with aviation, I do not
understand the helicopter analogy.
In my opinion, a helicopter driven by the engine
corresponds
in my understanding to a sailboat, where the propeller is
set to drive the boat *backwards* ..... When the
propeller
on the boat 'gets the chance' to run without the force of
the motor, that is just sailing forward by sail, I expect
the propeller to turn in the opposite direction ... that
is
'forward' ... If that happens in a helicopter, I would
expect the helicopter to hit the ground very fast ...
don't
you? I do not assume, that there is a lot of inertia in a
propeller or shaft en a sailboat - may be that is the
case
in a helicopter, and that could explain the smooth
landing
without the assistance from the motor - or I'm I
completely
wrong here? ...



The boat prop continues to turn in the same direction as
it did when it
was the method of propulsion since there is no change in
direction of
the water flow. In other words nothing forcing it to
counter rotate.

In the case of the helicopter technically you are correct
and a reversal
of direction would change the rotation of the blades.
However the rotors
are connected to the engine via gears and can only rotate
in the "lift"
direction. When the helicopter starts to fall due to loss
of power the
rotors, slowed buy the drag of gears and engine, are
forced to spin in
the lift direction causing "drag" that slows the copter to
a rate where
impact with the ground is, at least, survivable.



--
Mike G.
Heirloom Woods

www.heirloom-woods.net

I'm sorry - Now, I don't understand the argument or the
analogy from the helicopter to the boat of my brother in law
with three fixed blades ... Should he lock it or let it
'freewheel'?

--
Flemming Torp