Re: Helicopters and courtyards

On May 17, 11:26�pm, emoneyjoe <emoney...@iglou.com> wrote:

On Mon, 16 May 2011 16:50:48 -0700 (PDT), "m...@sushi.com"









<m...@sushi.com> wrote:

On May 6, 11:46�pm, Gosh Darn <kefisc...@iglou.com> wrote:

� � � � �I thought it was well known that a helicopter cannot hover
or land in a courtyard, the walls cause the airflow to form a
doughnut shaped torus of air, instead of being accellerated
downward and outward.

� � � � �This made the news 20 or 30 years a go when a woman
pilot was asked to hover in a church or school courtyard while
a man tossed out prizes of some sort. � �
� � � � �People were decapitated when the hekicopter lost
lift and fell.

� � � � �As far as low radar cross section helicopters go, the
patent office included a 1977 study on the uh-60 in the
office response to the application I mailed on Dec. 22, 1978.
� � � � �It was stamped "Level 12", whatever that meant,
I had no clearance at any time, and that application was
never under secrecy order.

This is the dreaded vortex ring. However they hover in choppers all
the time, so I don't know why it is considered appropriate in some
situations. Pilots given their druthers rather fly tight orbits than
hover to avoid the vortex ring.


� � � � �They don't hover in courtyards less than twice the diameter
of the rotors, it is not possible because the same air is moving
in the only directions it can, the doughnut vortex.

� � � � � Maybe experiments should be done with walls made
of plastic film and supported by light duty twine that would
no break rotors of tail propellor, then data on courtyard
size compared to rotor diameter could be recorded.

I was in a traffic helicopter that was doing tight orbits over a crash
scene. I had a GPS with me and the horizontal velocity was about
60mph. I think the pilot was trying to make me hurl.


� � � � �An up and down roller coaster would do it. :-)

I think you make a helicopter stealthy by flying it in the radar holes
as much as possible. ACE has software to predict the dead spots.
Of course there are civilian programs that can do the same thing, such
as the open source version of GRASS, SPAT!, and radio mobile.


� � � � � I think radar is easy to counter, noise is the big problem,
and too many shoulder missiles are heat seekers.

� � � � � Detecting all possible wavelengths and types of radar
would be difficult, but what do I know, I have never seen a
radar set in operation. :-)

Ken


Spinning blades are apparently a real problem regarding detection.
They produce a Doppler shift that is easy to detect.

I suppose the alternative would have been to do the operation with
some Soviet era choppers that would attract less attention. Kind of
like hiding in plain sight. Hiding in plain sight should never be
underestimated. The cops do this all the time, and after all, this was
just a raid, granted with a high value target.

In a shit hole town where I used to work, the cops did the old "moving
van" trick often for raiding meth labs. The moving van doesn't attract
attention until the cops pile out of it.