DescentBB

This is taken from todays Aviation Daily. Thought some here may be interested.

The House Transportation aviation subcommittee tomorrow will hold a hearing on the threat of lasers to airline safety.

A Delta pilot last September reported an eye injury from a commercial hand-held laser that was beamed into the cockpit during an approach at Salt Lake City.

The FBI in November and the Homeland Security Dept. posted a notice that terrorists may try to bring down an aircraft by shining lasers into the cockpits to blind pilots.

The U.S. Dept. of Defense has developed eye shields that can mitigate the effects of lasers by blocking out their green light, but theyâ??re a hazard in civil aviation because air traffic controllers also use green light. DOD and FAA will propose creating a working
group to evaluate both technical and tactical laser mitigation strategies.

Representatives from the FAA, North American Aerospace Defense Command and Air Line Pilots Association will testify.

outlawing flashlights is a dumb idea

The law isn't against flashlights--it's against high-powered green lasers being shined into the cockpits of planes, temporarily blinding the pilot.

both emit visible light, just at different wavelengths, therefore both are flashlights

ccb056 wrote:both emit visible light, just at different wavelengths, therefore both are flashlights

Um, no. Not in the least. Did you flunk grade-school science or something?

Flashlights can be used to illuminate areas and help you see things better.

Laser pointers can't, or at least not feasibly.

Top Gun wrote:

ccb056 wrote:both emit visible light, just at different wavelengths, therefore both are flashlights

Um, no. Not in the least. Did you flunk grade-school science or something?

He's a moron. Just do a search on his posts and you'll see why.

Sirius wrote:Flashlights can be used to illuminate areas and help you see things better.

Laser pointers can't, or at least not feasibly.

exactly correct, and the reason behind that is the wavelength of the two light sources

using a standard flashlight, you are operating at a much lower frequency than a laser, diffraction, or the bending of waves around obstacles or edges of an opening, causes lower freqency waves to disperse quicker and easier than higher frequency waves

therefore, a flashlight operating at a lower frequency will have a wider beam at the same distance compared to a laser operating at a higher frequency, however, if the amplitude of the laser is high enough, and you can shoot the beam far enogh, there would be a distance where the laser beam has diffracted to such an extent that it can therefore be similiar to a flashlight beam

however, I digress, this isn't a topic about the mechanics of light, rather a topic about the banning of flashlights

Er...

Yes, lasers do disperse eventually, and diffraction is one of the reasons, but they take far longer than flashlights.

To blind someone with a flashlight it'd need to be either about ten thousand watts (which is more like a stadium floodlight, and I don't think they make handheld or discrete versions of those), or held right up to their eye.

OTOH, a 10-watt laser beam can remain coherent enough to cause eye damage for hundreds of metres if not kilometres.

As for the reasons for that behaviour... well, I won't go there. :/

Flashlight : Laser :: skateboard : M1A1 Abrams tank

Lothar wrote:Flashlight : Laser :: skateboard : M1A1 Abrams tank

So we are just gonna park a bunch of M1A1 tanks near airport runways and shoot anyone that walks by with a flashlight?

lasers emit higher FREQUENCY light?
wtf?

by that definition my black light is a laser,
and my red-laser pen isn't.

lasers come in all kinds of frequencys - infra-red to ultra-violet (and more).
and so do flashlights.

my definition of a laser is something which emitts coherent light, and i thought they were rather powerful compared to flashlights because of the inheret focus of coherent focus.

i'm not dissing you ccb056, i'd like you to explain what frequency has to do with lasers - you know, i don't .

light doesn't become a "laser" until it kills someone

Krom wrote:

Lothar wrote:Flashlight : Laser :: skateboard : M1A1 Abrams tank

So we are just gonna park a bunch of M1A1 tanks near airport runways and shoot anyone that walks by with a flashlight?

Yeah... and if somebody walks by with a laser, we'll beat them with our skateboards!

A LASER is a CONCENTRATED BEAM OF COHERENT LIGHT. The word "laser" is actually an abbreviation for "light amplification by stimulated emission of radiation". Laser light is a concentrated stream of amplified light and radiation. This is why it's advised NOT to point on into people's eyes!

For someone to shine a beam that narrow through a plane window (which isn't very big in relation to the rest of the plane) and into a pilot's eyes (which are much smaller than the window) while flying a MOVING plane long enough to blind him would take EXTREMELY unnatural accuracy...or a case of freak coincidence.

Either someone MEANT to blind the guy or this story's hokey.

We've been all over this before. It wouldn't be that hard if the plane's on a landing approach; the plane is flying less than 100 mph. Also, lasers can be wide--IIRC, there's some lasers with a diameter of over 1-1.5 inches. It would also take less than .1 seconds of laser hit time in order to temporarily blind a person, especially at night. The cockpit would also be lighted at night, clearly showing the pilot to anyone standing outside. There are also fairly cheap ways of tracking a moving object mechanically.

In that case, I withdrawl latter statements.

My first statement still stand, for those who don't understand what a laser actually is.

MDX wrote:For someone to shine a beam that narrow through a plane window (which isn't very big in relation to the rest of the plane) and into a pilot's eyes (which are much smaller than the window) while flying a MOVING plane long enough to blind him would take EXTREMELY unnatural accuracy...or a case of freak coincidence.

Either someone MEANT to blind the guy or this story's hokey.

I've said this same thing a few months back. Also, last I checked they don't let joe sixpack within a half mile of an airport runway unless he buys a ticket. The whole airport is fenced off to prevent people from running onto the runways and getting squashed by a 747 that's landing.

While I agree with you Ferny, that fact remains in ever larger numbers, pilots are seeing laser light in their cockpits. Perhaps the lasers are mounted or attached to a telescopic sight for better aiming?

even if that's the case you'd have to control the telescope with a very high degree of precision. A degree that the human hand cannot accomplish.

Besides if a pilot sees a laser light in the cockpit, he's probably not paying attention to where he's going.

Makes you wonder if he saw it when the plane was parked.

Ferno wrote:even if that's the case you'd have to control the telescope with a very high degree of precision. A degree that the human hand cannot accomplish.

Again, there are very cheap ways of mechanically controlling a precise path. My dad owns a telescope with a tracking engine on it--set it up, tell it the course whatever it's tracking will take, set its initial position etc using GPS coordinates and a laptop, and it will track an object (even be it as small as a star) perfectly through 180 degrees of motion.

Hitting an aircraft with a laser can be done quite easily actually. Just pick an airport that has a fairly flat glide slope with little obstruction along the final approach path. Position yourself directly on the approach path as close as you can to the runwayâ??s centerline. As the plane is on final and approaching the threshold of the runway, it will be coming straight at you with very little relative vertical or lateral movement. Point and shoot. From a relative movement standpoint, you are practically hitting a stationary target. You also have the added benefit that the pilot and co-pilot will be looking straight at you at the time.

Lindbergh field in San Diego comes to mind. Even though its glide slope is moderately steep, there is a 3 story parking garage less than 300 yds from the runway threshold. As the aircraft fly directly over the garage, they are low enough you could hit it by throwing a rock at it. You could easily park on the top deck, open up your carâ??s moon roof, steady the laser on top of the car and shine away.

Neat huh?

With all that heightened security since 9-11, you'd think they coulda stopped something like some jerk with a laser pointer.

Airport security can't do much to defend pilots from someone shining a beam of light at an aircraft from outside an airport.

ya'd think someone would notice a person or two setting up a tripod near an airport where people usually don't go.

Also, don't planes land with the nose up and have autopilot assist?

Autopilot, not necessary but I think usually, these days.

Nose up, definitely. Would make getting the right angle a bit tricky.

Ferno wrote:ya'd think someone would notice a person or two setting up a tripod near an airport where people usually don't go.

Depends on the airport and the level of police activity around it. I work at Hartsfield-Jackson here in Atlanta. I see people setting up cameras on tripods just outside the airport perimeter from time to time to take pictures of the aircraft as they land. As long as they aren't on airport property and aren't breaking any laws, the police seem to leave them alone.

Ferno wrote:Also, don't planes land with the nose up and have autopilot assist?

Depends greatly on the aircraft type and the distance from the touchdown point. Some ailiners, the 757 for example, have a relatively low angle of attack while in final aproach until right before touchdown when they flare. I believe the 737 is the same way. You usually don't really see them flare unitl they cross the runway threshold.

I'm also wondering about the tracking system used on telescopes. In relation to an aircraft the tracking system on a telescope moves very slowly, right? so, the only thing that's fast enough to track an aircraft is a military weapon system, such as a mobile SAM launcher.

They move slowly not because the motor is that slow but because of their gearing. Modify the thing slightly by reversing two of the gears and it can move very quickly. Heck you could even build a custom plastic casing for the thing if you're that interested. You'd need to redo the programming of the tracker slightly to adjust for the increase in speed, but it is most certainly possible.

Such hackjobs as this would actually be preferable to a potential terrorist rather than detrimental; the knowledge necessary to set up a telescope tracking engine to move faster and the knowledge to set up the program to use the faster system is quite rudimentary--I could do it myself, if Dad would let me screw around with the motors of the one he has, which I'm pretty sure he won't--since it would be much, MUCH harder to track anyone using a custom system, since the government couldn't track where it came from.

Ferno wrote:I'm also wondering about the tracking system used on telescopes. In relation to an aircraft the tracking system on a telescope moves very slowly, right? so, the only thing that's fast enough to track an aircraft is a military weapon system, such as a mobile SAM launcher.

Why would you need a tracking system?

To actually get the thing on target. Unless you have the eyesight of an eagle and a hand as steady as a machine, it's going to be essentially impossible to actually get the laser in the right place otherwise...

Sirius wrote:To actually get the thing on target. Unless you have the eyesight of an eagle and a hand as steady as a machine, it's going to be essentially impossible to actually get the laser in the right place otherwise...

I completely disagree. Read my second post of this thread.

Maybe we should get Mythbusters on the case. heh!

A tracking system was brought up so I simply decided to explore that.