Guy arrested for shining lasers at aircraft

On Mon, 10 Jan 2005 17:39:36 -0700, "Bob Myers"
wrote:


"nobody" wrote in message
news:1105393486.fc0a011e5ccee0bb4ab1b6422966850a@ teranews...
Bob Myers wrote:
On the other hand, I for one REALLY doubt that anyone
is actually using a hand-held laser pointer to cause any
problems at all for pilots. Consider the distances involved


Your logic is valid if you think someone actually was aiming for a pilot's
eyes.

But If you "paint" the cockpit by moving your laser around, the odds
aren't so
small that during the movement of the beam, it may pass over a pilot's
eyes.

OK, now figure out how long, if you are "painting" the
cockpit area with a hand-held pointer - or even something
a bit more sophisticated than hand-held - the beam would remain
in any given area of, say, 0.25 sq. inches. To get a bit more
sophisticated, do a similar basic-assumptions calculation
re the amount of light that would actually be delivered to
that area within a given amount of time.

Sorry, but this one just doesn't hold up to the basic
back-of-the-envelope tests...

Such laser beams are well-collimated but they don't hold their
size over long distances. Their is some spread due to aperture
size alone. It certainly seems ripe for simple home
experimentation without the need for speculation or the backs of
envelopes.



************* DAVE HATUNEN ) *************
* Tucson Arizona, out where the cacti grow *
* My typos & mispellings are intentional copyright traps *

On Mon, 10 Jan 2005 17:39:36 -0700, "Bob Myers"
wrote:


"nobody" wrote in message
news:1105393486.fc0a011e5ccee0bb4ab1b6422966850a@ teranews...
Bob Myers wrote:
On the other hand, I for one REALLY doubt that anyone
is actually using a hand-held laser pointer to cause any
problems at all for pilots. Consider the distances involved


Your logic is valid if you think someone actually was aiming for a pilot's
eyes.

But If you "paint" the cockpit by moving your laser around, the odds
aren't so
small that during the movement of the beam, it may pass over a pilot's
eyes.

OK, now figure out how long, if you are "painting" the
cockpit area with a hand-held pointer - or even something
a bit more sophisticated than hand-held - the beam would remain
in any given area of, say, 0.25 sq. inches. To get a bit more
sophisticated, do a similar basic-assumptions calculation
re the amount of light that would actually be delivered to
that area within a given amount of time.

Sorry, but this one just doesn't hold up to the basic
back-of-the-envelope tests...

Such laser beams are well-collimated but they don't hold their
size over long distances. Their is some spread due to aperture
size alone. It certainly seems ripe for simple home
experimentation without the need for speculation or the backs of
envelopes.



************* DAVE HATUNEN ) *************
* Tucson Arizona, out where the cacti grow *
* My typos & mispellings are intentional copyright traps *

On Tue, 11 Jan 2005 07:16:28 GMT, "G. Sylvester"
wrote:

Sorry, but this one just doesn't hold up to the basic
back-of-the-envelope tests...

well one way to find out. Have someone stand at the end of
one football field and have them shine a laser at you
at the other end of the field. I'm serious. Most likely
it is harmless. Nevertheless, if you did this off of
a overpass on a highway, it is not wise. Doing at airplanes
it is not wise either.

We also have yet to account for the problems raised
by the fact that the average airliner will have two pilots,
each of whom are generally equipped with two standard-
issue Mark I eyeballs...

you are right on this but is it worse to kill 1 person flying
that Cessna 152, 1 person flying the Cessna Citation or
kill 350 people flying the 777? Not to mention killing the
people on the ground who decide to build a house 50 meters
from the threshold grin.

Or, for that matter, the people who had a threshold built 50
meters from their house.


************* DAVE HATUNEN ) *************
* Tucson Arizona, out where the cacti grow *
* My typos & mispellings are intentional copyright traps *

On Tue, 11 Jan 2005 07:16:28 GMT, "G. Sylvester"
wrote:

Sorry, but this one just doesn't hold up to the basic
back-of-the-envelope tests...

well one way to find out. Have someone stand at the end of
one football field and have them shine a laser at you
at the other end of the field. I'm serious. Most likely
it is harmless. Nevertheless, if you did this off of
a overpass on a highway, it is not wise. Doing at airplanes
it is not wise either.

We also have yet to account for the problems raised
by the fact that the average airliner will have two pilots,
each of whom are generally equipped with two standard-
issue Mark I eyeballs...

you are right on this but is it worse to kill 1 person flying
that Cessna 152, 1 person flying the Cessna Citation or
kill 350 people flying the 777? Not to mention killing the
people on the ground who decide to build a house 50 meters
from the threshold grin.

Or, for that matter, the people who had a threshold built 50
meters from their house.


************* DAVE HATUNEN ) *************
* Tucson Arizona, out where the cacti grow *
* My typos & mispellings are intentional copyright traps *

Bob Myers wrote:
Actually, you DO...you need to deliver a certain minimum
visible flux for a certain minimum time for the perception
of a flash to occur.

You wouldn't have to shine a laser into an eyeball for very long to distract
the pilot.

level of detail, but I seriously doubt that a handheld laser
pointer from a distance of at least several hundred feet and
likely a good deal more is going to make it here.

The astronauts on the space station say that during magnetic solar storms,
even in the most sheltered areas of the station, when they close their eyes,
they can see some brief flashes as solar particles hit their retina.

At night, very few ground lights are directed up to the skies, and the pilot's
eyes are used to much lower levels of light. So a laser might stll be strong
enough to attract their attention.


Considering the face that we ARE supposedly talking
about a laser, and hence a relatively tight beam (despite
the unavoidable dispersion of such a low-quality source),
exactly how does that work, again?

With a strong flashlight at the cottage at night, shining it upwards will
reveal a quite long beam of light visible as the light passes through humidity
in the air.

A laser will do the same, illuminating tiny particles in the air (dust, water)
along its path, which creates a visible path taken by the light. If such a
beam were to follow more or less the plane, the the pilots would be able to
see a beam of green/red/whatever light that more or less follows the aircraft
instead of quickly fading away.

Which "guy" are you talking about here?

The guy on the ground. He may not see the red/green dot he is painting on the
aircraft, but he can see the trail of light created as the beam of light
travels through the not 100% pure air.

And the farther you are from aircraft, the slower the aircraft moves relative
to you (in terms of angular change). So it isn't that difficult to track it.
You might not be able to focus on a very precise location on the aircraft and
keep your beem on that point, but you should be able to aim it in the general
direction of the aircraft quite easily.

Tell you what - grab your handy laser point, pick out a
building several hundred feet away, and see how you do
both in spotting the beam and keeping it directed toward
a specific area from that distance.

If done at night with some mist, it should be quite easy because you don't
have to see the final dot on the remote building, you can use the beam of
light left as the laser light travels through the mist to gauge where you are
pointing to.

I don't. A pilot is NOT going to "spend time looking out
the side window" or ANYWHERE he or she doesn't NEED
to be looking,


Yet, there have been reports of pilots just doing this.

I am the first one to admit that this story was blown out of proportions. But
I still find it credible that someone aimed a laser at a plane and would have
created a very brief flash in someone'e eyes.

However, it would probably be more likely to be on some passengers who have
their eyes on the side windows than on pilots who are looking ahead.

"nobody" wrote in message
news:1105470390.64d3262bfd373443f48a4701e8c2e4f0@t eranews...
Bob Myers wrote:
Actually, you DO...you need to deliver a certain minimum
visible flux for a certain minimum time for the perception
of a flash to occur.

You wouldn't have to shine a laser into an eyeball for very long to
distract
the pilot.

Well, as has already been stated - you're free to do the obvious
tests to find out.


level of detail, but I seriously doubt that a handheld laser
pointer from a distance of at least several hundred feet and
likely a good deal more is going to make it here.

The astronauts on the space station say that during magnetic solar storms,
even in the most sheltered areas of the station, when they close their
eyes,
they can see some brief flashes as solar particles hit their retina.

And this is relevant how, exactly? It's a totally different
mechanism.


A laser will do the same, illuminating tiny particles in the air (dust,
water)
along its path, which creates a visible path taken by the light. If such a
beam were to follow more or less the plane, the the pilots would be able
to
see a beam of green/red/whatever light that more or less follows the
aircraft
instead of quickly fading away.

Again, try it - or at least run the numbers to verify what you're
talking about before you go too much further down this path.


And the farther you are from aircraft, the slower the aircraft moves
relative
to you (in terms of angular change). So it isn't that difficult to track
it.

The speed of the aircraft relative to the observer is not the issue
here - it's the ability of said person to direct the beam with sufficient
accuracy and stability, which again gets much worse the farther
away you are. And again as already suggested, find yourself a
convenient building the appropriate distance away, put an
eyeball-sized target on it, and see how well you do trying to light
it up with a handheld laser pointer.

You might not be able to focus on a very precise location on the aircraft
and
keep your beem on that point, but you should be able to aim it in the
general
direction of the aircraft quite easily.

Well, yes, in the sense that hopefully you could aim the
"beem" in the general direction of, say, North fairly easily.
Beyond that, I would very much like to see you try.

If done at night with some mist, it should be quite easy because you don't
have to see the final dot on the remote building, you can use the beam of
light left as the laser light travels through the mist to gauge where you
are
pointing to.

Unfortunately, that same mist will serve to quickly disperse and
attenuate the beam. Having anything visible over a distance of
a few hundred feet, in misty/dusty/whatever conditions, is going
to require something with a bit more oomph (that's a technical
term, thar, son...:-)) than your average little pocket pointer.


Bob M.

When I saw Pink Floyd back in the 90's, the FAA restricted the airspace for
several miles around the stadium because of the copper vapor lasers.