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I recently came across the FAA's press release regarding the diffracting laser lights which appear every Christmas:

You might not realize this, but a well-meaning attempt to spread holiday cheer has the potential to create a serious safety risk to pilots and passengers on airplanes that fly overhead. So please make sure all laser lights are directed at your house and not pointing towards the sky. The extremely concentrated beams of laser lights reach much farther than you might realize.

The FAA makes it clear that there is a substantial concern regarding laser-blindeness among pilots. And its clear the FAA will do something about it. But what can they truly do to help, within the limits of their authority?

Doing some research (okay... fine... having Google link me to Wikipedia), I find the following limits:

  • 0.05 µW/cm² - Laser Free Zone
  • 5.00 µW/cm² - Critical Flight Zone (10 nmi around airports)
  • 100.0 µW/cm² - Sensitive Flight Zone
  • 2500 µW/cm² - Normal Flight

I did some calculations on a class 3R laser pointer with a safety factor of 3 built into them, and got results which were quite in line with this infographic from Laser Safety Facts. I'll report the professional numbers, rather than my own, just to avoid uncertainty. These are the distances at which point the laser pointer crosses the threshold and it becomes illegal to point them at an aircraft (according to laboratory conditions. Obviously one should never intentionally point a laser pointer at an aircraft, regardless of power):

  • 10,995 ft - Laser Free Zone
  • 1,096 ft - Critical Flight Zone
  • 245 ft - Sensitive Flight Zone
  • 104 ft - Normal Flight Zone

(Note: these numbers are consistent with those linked in this answer to a related question, and come from the same site)

With a minimum altitude for flight over urban terrain set at 1000ft, it appears it is not possible for a standard green 3R laser pointer to cross the threshold chosen by the FAA for critical flight zones, much less normal flight zones. Over rural areas, the lower 500ft minimum altitude could play a part, but would still never reach the normal flight range. Naturally, there is the possibility of violating requirements near or within a critical flight zone, where landing aircraft may be much lower than 1000ft, but it shows the level of concern that the FAA has for that given brightness threshold.

This seems quite inconsistent with the FAA press release. The holiday laser light shows have a substantially higher dispersion than a typical laser pointer (indeed, they start by fracturing it into dozens of smaller points with cheap optics).

It's possible the FAA is intentionally overstating the risk, but its also possible that the thresholds chosen are simply much higher than is truly comfortable for pilots. With thousands of laser strikes reported per year, pilots' comfort level is clearly surpassed by laser strikes on a regular basis.

Does the data suggest the FAA limits are too high to sufficiently protect pilots? (I'd ask whether they should be changed, but that would turn into a quagmire of opinion based regulation changes quite quickly)

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  • $\begingroup$ I think the question needs a bit of clarification: do you want to know about the risk of eye injury or the risk of distraction? These are completely different issues. Beware that laser safety labels found on lasers often have little relation to reality, and this is especially true for cheaper consumer lasers. In my experience, the laser safety labels never include the nominal hazard zone, which is essential information for aviation safety but does not matter at all for indoor use. $\endgroup$ Dec 7, 2021 at 21:04
  • $\begingroup$ If your visible-frequency laser is not able to create a distraction from 1000 ft away at night when visibility is good, I would say you've got a broken laser. I've used very many lasers but never flown an aircraft. $\endgroup$ Dec 7, 2021 at 21:09
  • $\begingroup$ @AnonymousPhysicist I'm trying to grapple with what appears to be an inconsistency in the messaging. On one hand the argument is that lasers can distract pilots, so you should never ever ever ever do anything remotely like pointing one to the sky. On the other hand, when you look at the numbers they use to define "distraction," a reasonable IIIa or 3R laser falls short of the threshold, and these holiday devices are well over 100x weaker than that! It would be like the DOT saying "driving fast is incredibly unsafe. Never do it" and then setting the speed limits to 150mph. $\endgroup$
    – Cort Ammon
    Dec 7, 2021 at 23:35
  • $\begingroup$ Distraction is not related to the class of a laser. A Class 1 laser may cause distraction. $\endgroup$ Dec 8, 2021 at 0:09
  • $\begingroup$ @AnonymousPhysicist The FAA defines the power density (uW/cm2) which is considered to be a distraction to pilots. Combine the class (which defines maximum power) with a divergence of the beam (which is reasonably well known for laser pointers as a class of devices to be somewhere on the 0.5 to 1.0 mrad range), and an altitude and you get power density. If it turns out that power density was not the correct unit of measure for the FAA, that would probably a decent frame-challenge answer: the limits aren't too high because they're the wrong measurement. $\endgroup$
    – Cort Ammon
    Dec 8, 2021 at 16:20

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A non aviation reason the FAA may be taking the position they do is that many LASER devices are marketed as 'brightest' and sold to people without means to measure actual power level, so it is normal for devices sold to not conform to standards. Further the power is adjustable in many devices so consumers may adjust upwards for a better show regardless. Source - have access to power measuring equipment, ebay and respect for my vision. So FAA cannot take it on faith that consumer devices really are 'safe' at the ranges listed.

Related, it is in the FAA interest to not to normalise aircraft being illuminated with LASERs, so if they push for 'any LASER observed by an aircraft should be investigated and considered a crime by default' they side step the questions of 'was the device legal' and 'was it pointed intentionally' when someone does maliciously dazzle pilots.

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Having a laser illuminate your cockpit is a distraction, at least. If it's a holiday display, you might get one or two quick flashes out of it, but at 150 to 250 knots, you've flown past it before you'll get more than that. And, above 1,000', as the OP points out, you're beyond the range where the household displays have the power to harm you. So the distraction is the main factor there. And a single blip, flying past a brightly lit up neighborhood, doesn't amount to all that much, generally.

When you have a bad actor who is using a green beam to intentionally illuminate an aircraft, that's an entirely different story, and that's when things absolutely get reported to ATC in real time, along with a best estimate of location of the laser, and a police helo (if available) can get dispatched, and if the perpetrator gets caught, I'll gladly non-rev across the country to testify against him. That sort of intentional malice against an aircraft full of people deserves years in prison, whether or not the device being used was actually capable of blinding somebody at the range involved. Since a lot of these devices are from a very large and very unsavory country (which exports lethal drugs in great quantity, tortures their own citizens, lies about a lethal virus they created, etc etc), I wouldn't trust that the devices necessarily meet the stated power limits -- and certainly not when one is being pointed at my cockpit!

As for the question if the limits that the FAA sets should be different, that's really a question of what it takes to damage a person's vision under different conditions. Obviously the goal is to be cautious & conservative, and even without permanent damage, the distraction effects of the bright lights and any after-effects that persist for seconds or minutes can have repercussions for pilots that are more serious than in other settings.

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