Possiblity of Pilot Eye Damage

[Laser Ben]

With all these claims or pilots being blinded, let’s consider the following...

At 3uW/cm2 Eye distraction occurs
At 20uW/cm2 Temporary Flash Blindness
At 20mW/cm2 Permanent Eye Damage

Assuming an idiot has a 100mw laser with a 1mm beam and 2mRad divergence. 1000 meters away is a plane. Assuming there is no error in the angles and the beam actually can make it inside. This is also assuming the beam is non-gaussian and perfectly round.

At 1000 meters the beam diameter would be almost exactly 2 meters diameter. This means that the area of the beam is 3.141 meters2 or 31410 cm2. This means that the relative brightness of the light hitting the window is 3.183uW/cm2. This is just at the threshold of eye distraction, and NOT permanent damage or even flash blindness as many people have claimed.

1000meters may seem like a lot, but on a runway, it’s not too much, Attached is a picture illustrating what I mean. Lets take the San Jose airport for example. Standing on the closest road, 1000 meters makes id about 1/3 of the way down the runway, the same distance as most of the incidents have been occurring.

Now there would be more losses with the reflections in the windows, the losses in the Rayleigh scattering in the air. All this added up, there is only a chance of minor distraction, but then again, the lights illuminating the runway is going to have more of an effect. I just think that all these claims that people are being blinded by lasers is somewhat bogus. I remember reading one a while back where the person accused of shining the lasers had battery charges for physically hurting the people in the cockpit.

What do you guys think?

[mixedgas]

let us not give people ideas about boresighting a certain widget with a pair of something.
In other words, for Christ sake guys, dont tell the bad guys how to do it in this forum. Dont mention, If I were gonna do this I'd use a .....

Ben, having did some support work for the guys who did a presentation for ILDA to SAE G10,and having done outdoor show reports to the FAA, I want to know where the heck are you going with this,
besides the usual "FAA are overrestrictive" thread? This is very politically charged issue right now and you are on a open forum, readable by the press.

If your gonna continue with this thread, read up on 21 cfr 1040.1 subchapters I and J and FAA reg 7400 revision G (Lasers in Airspace) first.

And before we slug it out, know what a CZED and a NOHD are.

After some political things that have happened lately, there are reasons people go to jail for aiming 300 mW pointers at aircraft. Like this, which happened 20 miles from me:

http://blog.cleveland.com/metro/2008...ing_laser.html
Find the FLIR video on the Cleveland Plain Dealer WEB SITE

Idiot illuminated several choppers and approaching airliners, including a medivac and a police chopper.

IT AINT BOGUS. Then call Greg Makhov at LSDI (ILDA safety Commitee Chair) and ask him for the ILDA aircraft test results with the helicopter video.

then we'll talk.

Steve Roberts

[Things]

He made the thread to talk about the the true facts of lasers & planes, not if its possible or not, and how to do it. The calculations are actually quite interesting. 100mw spread over 2m is tiny.

[mixedgas]

Here:

http://www.pangolin.com/resguide09c.htm


yeah, I know, peopel should not go to jail for a few mW or pointer, but if you dont make a example of a few people,,,,, or you dont enforce the import laws that are on the books....

In several jurisdictions, you can have a cop return fire on you without you shooting first for illuminating them with a pointer.

florida has a your dumb with a pointer law....

Etc.

In the states right now, we dont need the problems OZ has developed with laser licensing, but we do need enforcement of illegal laser imports. etc.

VERY POLITICAL RIGHT NOW!

I dont need my lasers treated as guns, its bad enough that in one town here you can go out in your back yard and shoot, and two miles away you get treated like a felon for driving over the city line with one locked and stowed in the trunk with the ammo in the glove box, which is the way to travel with a gun per federal law.
Steve

[Laser Ben]

Steve,

I didn't mean to encourage people to do this. My intention is completly opposite. I am just wondering about what exactly is happening here and the math behind it. That's all.

If you really feel so strongly about the issue, I can ask Admin to take the thread off, but I don't see it as doing any harm.

If someone wants to shoot a laser at a cockpit, they are going to do so and I don't think that any post on a forum is going to make them want to do so even more.

I had never seen that page on the Pangolin site before, but even with that, I would be interested in seeing the math they used for their numbers as they seem very high.

[Xytrell]

Where did that figure of 20mW/cm² originate?

If a 2mW red laser had a diameter of say 3mm, that's ~0.0705 cm². Wouldn't that make the irradiance (when viewing directly at close range) 28mW/cm²?

Assuming I calculated that correctly, I don't see how a 2mW red laser is going to cause permanent eye damage. Or is this only if you looked into it for 4 hours?

[Laser Ben]

That number came from my father who works with high power LEDs. That is the company standard for "permanent damage". I can check with him about exactly what kind of damage that is.

[White-Light]

I've said this for a long time, that pilots claims are over exaggerated.

Thats not to say I in any way condone shining anything laser or otherwise at planes, I don't and its stupid and potentially dangerous even if just from the distraction factor and those caught should be treated harshly when it occurs.

However, the claims made of "its only a matter of time before we have a major air crash caused by a pilot being blinded by a laser" are rubbish in my opinion as laser powers and divergence just make any kind of blinding, even temporary, highly unlikely from a laser pointer, at least in the UK.

Most incidents occur when pilots are coming into land which means not only do you have to factor in the distance from outside the airfield perimeter to the aircraft but also its height as well. Also, in the UK at least, laser pointers are now limited to I think around 1mw and even pre this most legally sold were around 5mw. At these powers even from near point blank with no real divergence its going to be hard to do any damage at all short of staring down a stationary beam. Factor in the divergence due to distance from the aircraft and you might as well be looking at a torch - the airfield landing lights are probably brighter!!!

Also, finally, how many people are laser scanned in clubs every weekend from lasers of 50-100mw from close distances and without MPE calcs and walk out without even temporary blindness? I'm not saying this is safe, clearly it isn't, but the lack of recorded eye injuries by opticians seems to indicate that they're getting away with it even if only by luck. Here's a still from a club I've been to:




Thats a cheap Chinese laser simply placed onto the speaker. Pink cased, and looking around ebay, probably between 50-100mw.
Nearest person is dancing maybe 4 feet from the aperture!! Don't be fooled by the apparent weakness here - this is a capture of a still from a video. The beams are reasonably bright in real life.

For planes, factor in distance and power differences and you realise you'd need a serious laser such as a multi watt (possibly YAG?) to stand any real chance of posing a serious threat to a flight and most idiots don't possess those thankfully.

Therefore as the original OP said, divergence means its highly unlikely any claim of even temporary blindness from a pointer could be real. At best over exaggerated due to fear, at worst,
psychosomatic symptoms brought on by fear of receiving a hit.

[Xytrell]

I think they're more concerned with the whole concept of distraction during a crucial part of flying rather than flash blinding.

[mixedgas]

Lets start with some definitions, shall we?

NOHD, nominal ocular hazard distance.
SZED= Sensitive Zone Exposure Distance = 100 uW/cm^2
CZED = critical Zone Exposure Distance = 5 uW/cm^2
LFED = 50 nanowatts/cm^2 level

Ok, the class I , class II , class IIa and class III measurements go like this. Origional lab tests using primates, bunnies and some humans, depending on power level.

Class I is intrinsically safe for up to 8 hours, its 320 uW/Cm^2, which is damn annoying.
Most of you would not like have 320 uW into the eye. Now, be aware, that a class I housing can contain a class IV device, provided it is built in such as way to be intrinsically safe.

CLASS II is .95 mW visible light. IE aversion response, you'll blink or turn your head before it can do damage with a uncertainty of 1 , in 99,999, ie once in 100,000 exposures while using a Class II laser might make a tiny retinal lesion. Direct viewing of class II light for more then 15 minutes would probably cause damage. Requires warning stickers, emission indicators, shutter.

Class IIIA is 1-4.95 mW, a direct shot could cause damage 1 time in 9999 exposures, designed for reflective viewing of a scattered laser spot. Blink response will not help you here. Starting to require keyswitch and interlocks, emission indicators, shutter etc.

CLASS IIIB is 5 mW to 500 mW , strong likelyhood of a direct hit causing eye damage, some possible viewing of a diffused beam at the low end, starting of skin lesions, and photochemical effects can kick in, depending on wavelengh. Lots of safety requiremnts, Should not be accessable to untrained general public.

Class IV is 500mW and up, hazardous from even a diffuse reflection.



Now , the FAA numbers come from simulator tests ran after the Los Vegas illumination incidents, ran on volunteer airline and military pilots in a simulator in Oklahoma city. Those tests were ran with a small yag aimed into the sim, then multiplied by a safety factor. On a pilot audience who was probably hostile to any laser light from the getgo
History:

A automated big yag system was installed on a casino in vegas, part of the beam paths took it right into the McCaren Airport Approach paths. The Casino and evidently the company who did the install, supposedly ignored cease and desist warning letters from various government agencies. Evidently there were at least 60 aircraft illumination events based on this system. The FDA director at the time, was a publicity hound, and used the incidents in vegas to impose a mortatorium on laser shows nation wide.
FDA was in pickle over other issuses at the time and needed a political distraction, what better thing to use then a "Star Wars" type event to get peoples attention. So a industry that had a 20 year excellent safety record was a target. Pilots groups and the Airline industry and Tabloid TV Shows, jumped on the bandwagon, and when it was clear to FAA that CDRH was not gonna be up to the task, FAA made their own rules using recommendations from the SAE G10 Lasers in Airspace commitee.

So figure the FAA numbers could have huge buffers in them biased toward the regulators point of view. Then again, they could be scientifically valid.

Like I said, this is largely political. This was really not a problem when you needed a small frame argon running off three phase to do anything outdoors. Now with the proliferation of low cost yags, its gotten worse. With the huge amount of media attention given to the subject, its gotten even worse. When this started , the idea of a 200 mW handheld green laser was a pipe dream.

So if you want to talk about NOHD, CZED, SZED, LFED lets talk. It doesn't need to be damage, it can be inability to perform a task.

Many pilot injuries are caused by rubbing the eyes after a exposure etc, and keep in mid if you just flew cross country for 3 hour in the dark and take a flash hit, thats gonna really screw up your vision and be painful. Also keep in mind flashing one eye can cause skeleto-muscular effects , ie muscle strain in one eye....


Since US Flag Carriers can , by law, only fly into other nation's airspace if their rules match the FAA's rules, this became a world wide thing.

So Ben, you really want to discuss the safety factor multiplier used on the simulator exposure tests????

Plus the fact that the FAA can require between 30-90 days advanced notice before a outdoor show, can be a real problem from a business point of view

look at http://forms.faa.gov/forms/faa7140-1.pdf

gOOGLE: DOT/FAA/AM-04/9

Steve