Lasers and airplanes

[Art Upton]

Lasers and the Eyes,

Glad your ok Mach7,

back in '94 I got a FDDI laser cable shined into my left eye.
I felt eye discomfort so went to two different Eye MDs.
Both did lots of tests. They could find nothing wrong, at that time.

Around winter 2004-2005, my left eye is no longer as strong as my right eye, and now my reading glasses must be offset between the two to compensate.

I still cant help but wonder if that incident had something to do with it.

 

[11bravo]

Actually no. The beam is brightest when you view it on-axis (behind or gasp . . .in front of the beam) The reason being that the light reflects directly back to you when it hits air particulates.

Actually, in the context I used there are no particulates from which light can reflect back.

If they don't hit something on their way to the "target" you don't see them.
You can even see this a bit with a flashlight in a dark room.
From behind the "beam" you really cannot make out the beam at all; you can see stuff to the periphery that is illuminated by stray beams and of course what the light is shining on.

In good nature

 

[Reinhard]

Three reasons:

1. The human eye is considerably more sensitive to green light than red light.

2. Green light scatters more light when it comes into contact with air particulars than longer wavelength red light.

3. Chances are the air where you work is much more "clean" than outdoor air that is filled with dust, moisture, and other particulates. I have a 250mW red laser, and the beam is quite evident outdoors, although, not as bright as a green laser beam of even half the power.

There is not much left to add. This process is called Raleigh Scattering. It is more pronounced with shorter wavelengths. This is the reason why the sky is blue.

Actually, in the context I used there are no particulates from which light can reflect back.

The theory of Raleigh scattering applies to particles that are much smaller than the wavelength. So we're talking about the gaseous atoms of the atmosphere. Bigger particles are described by different theories (eg. Mie Scattering for clouds).

Reinhard

 

[bobkrech]

Mark

I'm glad to hear that you're alright, and I hope they really found the person who painted your plane. He should be going away for a while after the FBI and HSA talk to him because it's a felony to shine a laser at an airplane.

There were many incidents last year, and with the availablity of cheap and illegal high power laser pointers from China, it's only going to increase. Fortunately unless you get a direct hit to your eye, you shouldn't have any long term eye damage. The real danger is the immediate loss of night vision and disorientation that can result in loss of aircraft control. The simplest countermeasure is not to look the out the windscreen and immediately fly on instruments. You may also want to declare an emergency and pullup and away from the laser beam.

Just for completeness the astronomers who might be using laser pointers to point out stars, etc. should be aware it is also illegal to shine a none eyesafe laser in the air unless you have a way to insure that no aircraft are in range. It's easy in the daytime visually, but at night you really need radar. To minimize problems, use only Class I and II laser pointers which are eye safe, and assign several people to watch for aircraft, but realize that you still may be subject to prosecution if you accidently find an aircraft because the FAA and HSA has a zero tolerance policy.

Bob

 

[eastvolt]

He should be going away for a while after the FBI and HSA talk to him because it's a felony to shine a laser at an airplane.

Actually, its not. Many are under the belief there is presently a law specifically against this, but unfortunately, there is not. (See below)

Just for completeness the astronomers who might be using laser pointers to point out stars, etc. should be aware it is also illegal to shine a none eyesafe laser in the air unless you have a way to insure that no aircraft are in range. It's easy in the daytime visually, but at night you really need radar. To minimize problems, use only Class I and II laser pointers which are eye safe, and assign several people to watch for aircraft, but realize that you still may be subject to prosecution if you accidently find an aircraft because the FAA and HSA has a zero tolerance policy.

Bob

Sorry, thats not correct. There are presently no specific federal laws on the book that prohibit the shining of a laser at an aircraft, aircraft cockpit or one for simply shining one in the sky as you state.
HR1615, Securing Aircraft Cockpits against Lasers Act of 2007, which was in direct response to the recent rash of laser incidents and aircraft, was passed by the House, but still needs to go before
the Senate and finally signed by the President prior to being enacted. HR1615, Securing Aircraft Cockpits against Lasers Act of 2005, although passed in both Senate and House, never became a law due to the fact
the law wasn't completely ratified prior to the previous Congress' two year session. This is why its once again being presented for 2007.

This doesn't however prevent authorities from charging you with something else, like "general interference of an aircraft."
In particular, to the man (David Banach) who shined a laser pointer at a landing aircraft in NJ back in 2004 was charged with "interfering with the operator of a mass transportation vehicle" which
is a felony under the Patriot Act.

EDIT:
Of course, it is against the law to shine any laser pointer in the sky that is greater than 5mW in the US. This is regulated by the FDA CDRH - which is the only agency in the US regulating lasers. Full details of
their regulations can be found under CFR Title 21, Subchapter J, Part 1040.10. See link: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=1040.10

 

[user 13]

I think the FBI has control here, and I hope they do something. In the past law enforcement has been less than enthusiastic about prosecuting.

 

[Gym_Class_Hero]

Andrew,
Gym class..

I fly the MD-80, the best narrow body airliner in the world!

I love that thing! American Airlines I presume?

Is it the older analogue one or the newer one with some LCD screens?

 

[tonypv]

Mark,
Glade to hear your alright.
Wouldn't want you to miss any CMASS launches.
Hope they put the guy away for a long time.

 

[Nerull]

Clumsy reply is:

It isn't that some are "strong enough to be seen" and others are not, it's that the light waves in a laser beam are all traveling in the same direction and so none of them get to your eyes when you're off to the side.
If they don't hit something on their way to the "target" you don't see them.
You can even see this a bit with a flashlight in a dark room.
From behind the "beam" you really cannot make out the beam at all; you can see stuff to the periphery that is illuminated by stray beams and of course what the light is shining on.
In a dusty or smoky environment you can see the particles suspended in the air that the beam illuminates.
Same thing with a laser.
But without something being illuminated, you don't see either a laser beam or even regular light.

Except that green lasers are scattered by air, no dust required, though you can see those too - they make the beam sparkle, since they reflect considerably brighter than the regular scattering.

As for lighting up the whole cockpit, thats probobly not related to power, but to beam divergence. Consumer laser pointers don't have high quality collimnation, so the beam spreads out quite a bit as you move away from the source. At a range of a few kilometers it could easily be big enough to light up the whole cockpit.

This also means there is less energy at any one point. Your eyes were probobly safe, unless this was a insanely powerful laser. There isn't anything special about laser light that makes it dangerous - light is light. Its the brightness that causes problems - all that light entering your eye produces heat, and its the heat that causes damage.

The main danger in this case is the disorieinting effect of being hit with any source of light in that situation.

 

[stantonjtroy]

The problem is one of breeding, not legislation. As Ron White once said, " You can't fix STUPID!" Truer words were never spoken. Don't misunderstand, I too am a pilot and agree that these actions should be prosecuted but the idea of outlawing these lasers is nuts. It's an example of what I meant by "a problem of breeding". Thanks to laws to protect idiots from themselves, we as a culture, have bread common sense out of the human race in just a couple of generations. There was a time when stupid people did stupid things and suffered injury or death as a result. Sad, but the idiot was removed from the gene pool and those around him or her had a powerful object lesson. Now these idiots are suing others for their own stupidity, getting a book deal and hocking it on Oprah. Meanwhile those of us who use at least a measure of sense and responsibility are forced to suffer these idiots and the moronic legislation that spawns them. We need to stop expecting the government to fix our social woes and start influencing one another. The problem wasn't made overnight and sadly won't be fixed overnight. My opinion, nothing more.

Ladies and Gentelmen, Troy has left the soapbox.

 

[user 13]

I love that thing! American Airlines I presume?

Is it the older analogue one or the newer one with some LCD screens?

Nope, not American. Good guess though. Alaska airlines. We only have 18 MD's left and all but 2 have the EFIS instruments (we have to keep at least one round dial because our Simulator is round dial). They will all be gone in 1 year
Then I'll have to go to the 737.

I'm really glad I posted this here. The information has really set my mind at ease. I guess I should not be suprised that a bunch of rocket guys would know so much about lasers.

Mark

 

[bobkrech]

Actually, its not. Many are under the belief there is presently a law specifically against this, but unfortunately, there is not. (See below)
Sorry, thats not correct. There are presently no specific federal laws on the book that prohibit the shining of a laser at an aircraft, aircraft cockpit or one for simply shining one in the sky as you state. HR1615, Securing Aircraft Cockpits against Lasers Act of 2007, which was in direct response to the recent rash of laser incidents and aircraft, was passed by the House, but still needs to go before the Senate and finally signed by the President prior to being enacted. HR1615, Securing Aircraft Cockpits against Lasers Act of 2005, although passed in both Senate and House, never became a law due to the fact the law wasn't completely ratified prior to the previous Congress' two year session. This is why its once again being presented for 2007.

This doesn't however prevent authorities from charging you with something else, like "general interference of an aircraft." In particular, to the man (David Banach) who shined a laser pointer at a landing aircraft in NJ back in 2004 was charged with "interfering with the operator of a mass ransportation vehicle" which is a felony under the Patriot Act.

EDIT:
Of course, it is against the law to shine any laser pointer in the sky that is greater than 5mW in the US. This is regulated by the FDA CDRH - which is the only agency in the US regulating lasers. Full details of their regulations can be found under CFR Title 21, Subchapter J, Part 1040.10. See link: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=1040.10

There doesn't need to be a specific regulation prohibiting it. While the nature and number of incidents are classified, HSA and the FBI are charging anyone caught painting an aircraft with a laser with a felony for interfering with the safe operation of an aircraft. (I wish they would do the same thing to folks who think it's fun to shine a laser pointer at drivers. 3 of my coworkers have been lased commuting to work in the past 6 months.)

The FDA CDRH CFR Title 21, Subchapter J, Part 1040.10 requires that a laser beam pointed into the sky, at a building, or anywhere else where a human eye could be illuminated be eye safe. A laser pointer that outputs not more than 5 mw is a Class II laser and is considered to be eye safe by classification if no additional focusing optics are used, however more powerful lasers can be made eye safe if the laser beam is expanded so that the intensity is less than ~10 milliwatts/cm2. For example a 500 mw laser beam expanded and collomated in a 4" telescope would have a beam area of ~ 75 cm2 and an intensity of ~6.7 milliwatts/cm2. This would be considered eyesafe. Most of 1040.10 explains how to do these calculations, and my company performs these calculations for every laser system we sell commercially or that we use outside our building.

While a laser beam of this intensity will not cause eye injury to a pilot, it will cause temporary blindness, and disorientation and put an aircraft in jeopardy. The government, universities and companies involved in atmospheric research utilizing lasers are required to monitor for aircraft and are normally required to notify the FAA ATC before they begin laser operations. I think that amateur astronomers are taking a chance without notifying the FAA in advance of their events.

Bob

 

[JDcluster]

Then report them! There was a case just as you describe like that here in NJ.
They found the guy & arrested him.



JD

 

[Peartree]

Only mildly off topic, I was at a monor league ballpark a couple years ago and some doofus was aiming a laser pointer at the pitcher. Play was stopped temporarily because of him.

He was removed from the ballpark by security.

Everyone near him applauded security.

 

[eastvolt]

There doesn't need to be a specific regulation prohibiting it. While the nature and number of incidents are classified, HSA and the FBI are charging anyone caught painting an aircraft with a laser with a felony for interfering with the safe operation of an aircraft. (I wish they would do the same thing to folks who think it's fun to shine a laser pointer at drivers. 3 of my coworkers have been lased commuting to work in the past 6 months.)

Like I said in my previous post.

 

[user 13]

An update. The Huntington Beach PD has a 19 year old suspect, they are contacting the local FAA and looking at charging him with a felony. The City, State, and feds are all looking into it. He was using an astronomy laser call a sky spotter.

 

[DaveCombs]

:congrats:

 

[Nerull]

I can't find any information on "sky spotter" lasers. Is this a brand?

The majorty of lasers sold for astronomy purposes are in the <5mW range.

In reguards to notifying the FAA before astronomy events, that might be a good idea, but at the same time I think it would be pretty difficult to accidently hit the cockpit of an airplane with a laser. Aircraft flying high overhead aren't vulnerable, since you couldn't shine into the cockpit anyway. It needs to be at a low angle, which means either very far away, meaning a very weak beam, or close enough that you couldn't possibly miss it. Anyone who shines a laser into a cockpit is almost certainly doing it on purpose, IMHO. All the regulations, waivers, and notifications in the world won't stop a jackass from being a jackass.

 

[by basher]

Andrew,
That could be the offending laser, what we saw was green. Thanks for posting the link.

Thanks for all your kind words, they are appreciated.

Gym class..

I fly the MD-80, the best narrow body airliner in the world!

After the 727, of course.

As the laser is aimed at the cockpit, do you see it thru the front windscreen or out the side? Being ignorant of your literal point-of-view, does the nose block a forward strike?

As stated, glad you're safe and all under your command.

 

[user 13]

After the 727, of course.

As the laser is aimed at the cockpit, do you see it thru the front windscreen or out the side? Being ignorant of your literal point-of-view, does the nose block a forward strike?

As stated, glad you're safe and all under your command.

Yup the 727 is purdy, Never flew her officially but I did engineer on the whisper jet.

The laser came in through the right front windscreen, the nose slope allows us to see down and the laser to shine in.

Interesting info, when I called my unions medical office they said they get reports of a few laser illuminations a week. The Huntington beach PD said it's helicopters are hit 9-12 times a month! Go figure.

 

[DaveHein]

Fortunately your exposure to the laser should have been fairly low. I can't imagine someone being able to accurately track a small area on a plane travelling a few hundred miles per hour from three miles away. The light from the laser must have entered your eyes for less than a few milli-seconds as it randomly scanned by.

How large was the spot in the cockpit? Did it stay in one place or was it quickly jumping around?

Dave

 

[eastvolt]

Fortunately your exposure to the laser should have been fairly low. I can't imagine someone being able to accurately track a small area on a plane travelling a few hundred miles per hour from three miles away. The light from the laser must have entered your eyes for less than a few milli-seconds as it randomly scanned by.

How large was the spot in the cockpit? Did it stay in one place or was it quickly jumping around?

Dave

The light that would have hit the cockpit at three miles away would have been probably at least 10-20 feet (if not more) in diameter. The beam divergence on these low-cost portable (vs. high cost commercial systems) is pretty poor. I know even with my 120mW laser which is collimated quite well for a hand held laser pointer, at 1000 feet its beam is about 2 feet in diameter.

This is probably also the reason it was easy to hit the plane with such a large beam width at that distance. Plus, with the beam diameter so large and so far away, the actual light entering the eye is minimal.

 

[DaveHein]

So if a laser beam diverges 2 feet for every 1,000 feet at 3 miles the spot would be more than 30 feet in diameter. I wonder if a 150 mW laser would be even noticeable at this distance.

Maybe the culprit was actually on the plane. It may be that the beam reflected off of a shining part on the wing, such as a motor cowling. Or the plane may have one of those vertical structures at the end of the wing (a winglet?) that could serve as a reflective surface.

Dave

 

[bobkrech]

Fortunately your exposure to the laser should have been fairly low. I can't imagine someone being able to accurately track a small area on a plane travelling a few hundred miles per hour from three miles away. The light from the laser must have entered your eyes for less than a few milli-seconds as it randomly scanned by.

How large was the spot in the cockpit? Did it stay in one place or was it quickly jumping around?

Dave

The spot size of an unfocused laser beam is simple the product of the beam divergence times the distance. If the divergence is measured in milliradians and the distance is in kilometers, the product give the beam size in meters. If distance is measured in kilofeet, the spot diameter is in feet.

A typical 5 mw green laser pointer might have a beam divergence of 1.2 milliradians. At 1 kft. the beam diameter is 1.2'. At 1 km the beam
diameter is 1 meter. At 5 km (3 miles) the beam diameter is 6 M or 20'.

More powerful lasers have larger diameter output beams and typically have 2 or 3 times smaller beam divergences. A laser beam with a divergence that has a divergence 3x lower than another laser beam of the same energy will be a factor of 10x more intense at a long distance.

A laser point with external focusing optics can product a smaller spot size at a given distance, but the beam size is typically greater at other distances.

Lasers are much brighter than a normal light bulb or led. A standard light bulb is omnidirectional and emitts into a spherical area of 4 pi steradian. The difference in brightness of a coherent directed laser beam compared to a light bulb is (4*3.14)/(0.0012)^2 is a factor of 8,700,000 times the brightness of an equivalent omnidirectional light source. A 5 mW green laser with a 1.2 mr divergence has a brightness equivalent to a 43 kilowatt green lightbulb at the same distance! That a lot.

Bob

 

[heada]

"... blinded me with science..."

 

[shreadvector]

Don't forget to use proper warning labels:

https://www.leftmind.net/safety/laser.pdf

https://chrislawson.net/img/laser_eye.pdf

https://www.cafepress.com/fbod/297253

 

[eastvolt]

The spot size of an unfocused laser beam is simple the product of the beam divergence times the distance. If the divergence is measured in milliradians and the distance is in kilometers, the product give the beam size in meters. If distance is measured in kilofeet, the spot diameter is in feet.

A typical 5 mw green laser pointer might have a beam divergence of 1.2 milliradians. At 1 kft. the beam diameter is 1.2'. At 1 km the beam
diameter is 1 meter. At 5 km (3 miles) the beam diameter is 6 M or 20'.

More powerful lasers have larger diameter output beams and typically have 2 or 3 times smaller beam divergences. A laser beam with a divergence that has a divergence 3x lower than another laser beam of the same energy will be a factor of 10x more intense at a long distance.

A laser point with external focusing optics can product a smaller spot size at a given distance, but the beam size is typically greater at other distances.

Lasers are much brighter than a normal light bulb or led. A standard light bulb is omnidirectional and emitts into a spherical area of 4 pi steradian. The difference in brightness of a coherent directed laser beam compared to a light bulb is (4*3.14)/(0.0012)^2 is a factor of 8,700,000 times the brightness of an equivalent omnidirectional light source. A 5 mW green laser with a 1.2 mr divergence has a brightness equivalent to a 43 kilowatt green lightbulb at the same distance! That a lot.

Bob

Wicked Lasers pointers (most common is 95 or 120mW models) have beam divergence of 0.8 to 1.0 mRad, so at 3 miles, that spot is pretty dang big and the power hardly not enough to be any more than just an annoyance.

 

[bobkrech]

Wicked Lasers pointers (most common is 95 or 120mW models) have beam divergence of 0.8 to 1.0 mRad, so at 3 miles, that spot is pretty dang big and the power hardly not enough to be any more than just an annoyance.

The same brightness as a megawatt lightbulb at the same distance is a bit more than an annoyance to a dark adapted eye.

 

[Sandy H.]

Can anybody give an approximate power for the following lasers?

Pocket Laser Pointer, Surgical Laser, Grocery Store Scanner, Indoor/Outdoor "Laser Show", Metal Laser Cutter and any other lasers that are common knowledge for the average Joe.

This is just for curiosity. I honestly never knew there are lasers that could paint a plane in the sky or that people would do that sort of thing.

Glad you're fared OK Mach7.

Sandy.

 

[user 13]

Maybe the culprit was actually on the plane. It may be that the beam reflected off of a shining part on the wing, such as a motor cowling. Or the plane may have one of those vertical structures at the end of the wing (a winglet?) that could serve as a reflective surface.

Dave

Nope Dave, we saw where it came from on the ground. 1/2 mile south of the Huntington beach pier. As he tried to track us the beam moved off of us and back on 3 times, when it was off just a bit we could see it's location on the ground. Cudos to SoCal control for getting the local PD there so fast.

I agree with what Bob said, That beam was just about the brightest thing I have seen at night.

Mark