The following is from the main thread about l@ser attacks and is very interesting.
L@ser attacks on Aircraft
Not sure if this has been posted before. Stumbled across this whilst researching topic for a flight safety brief. Pretty sobering final para.
UK: Medical report on commercial pilot injured by blue l@ser at 1300 feet
Jan 24 2016
The journal Aerospace Medicine and Human Performance has published a paper entitled “Blue l@ser Induced Retinal Injury in a Commercial Pilot at 1300 ft”. The case report is as follows:
“An airline pilot presented to our department complaining of a blind spot in the upper left area of his visual field in the right eye (right supero-nasal scotoma) following exposure to a l@ser beam while performing a landing maneuver of a commercial aircraft. At around 1300 ft (396 m), a blue l@ser beam from the ground directly entered his right eye, with immediate flash blindness and pain. Spectral domain ocular coherence tomography highlighted a localized area of photoreceptor disruption corresponding to a well demarcated area of hypofluorescence on fundus autofluorescence, representing a focal outer retinal l@ser injury. Fundus examination a fortnight later revealed a clinically identifiable lesion in the pilot’s right eye commensurate with a retinal-laser burn.”
The paper said the pilot’s symptoms “fully resolved 2 wk later” and that there was no “deficit in visual function.”
The l@ser exposure happened at a “busy international airport within the United Kingdom.” According to the authors, “To the best of our knowledge this is the first documented case report of a likely retinal l@ser injury to a pilot during flight from a l@ser on the ground.” They believe the blue l@ser had a “radiant power of several watts and potentially could have led to permanent loss of central vision in the pilot’s right eye had the fovea, the area of retina responsible for high acuity vision, been involved.”
The case was first publicly announced November 23 2015 by the general secretary of the British Air Line Pilot’s Association (BALPA). He said it occurred in the spring of 2015.
From Aerospace Medicine and Human Performance, Vol. 87, No. 1, January 2016. Full text available here for purchase. Gosling DB, O’Hagan JB, Quhill FM. Blue l@ser induced retinal injury in a commercial pilot at 1300 ft. Aerosp Med Hum Perform. 2016; 87(1):69–70.
Analysis from LaserPointerSafety.com
Summary - What was the l@ser’s power?
Based on the data provided, it would have taken an exceptionally strong l@ser to even have a 50/50 chance of causing an eye injury at 1300 ft. We calculate such a l@ser would be well over 5 watts and possibly 30 or more watts. This is a conservative estimate. It assumes the l@ser and eye were not moving fast relative to each other — unlikely for a handheld l@ser aimed at a moving aircraft. It also assumes a relatively tight beam, and that the l@ser-to-aircraft distance was 1300 ft when it may well have been longer.
As of 2015, the highest power handheld visible l@sers sold on the Internet are roughly 3 watts. Sometimes handheld l@sers are advertised with greater powers, such as 5 or 10 watts, but the claimed power may be grossly incorrect. For example, in 2014 LaserPointerSafety.com purchased a “5 watt” handheld l@ser that was actually about 50 milliwatts, or 1/100th of the claimed power.
We believe one of the following scenarios is what happened:
1) The injury was a very unlucky one; the pilot just happened to experience a statistically unlikely injury that could be caused by a relatively low 3-5 watt handheld consumer l@ser
2) A higher powered l@ser in the range 5 to 30+ watts was used, possibly not handheld (e.g., an AC-powered general purpose l@ser). If so, this may have been a deliberate attempt to cause damage.
3) The injury, or change to the retina, was less damaging (not as serious) compared to the injuries used to determine basic l@ser safety concepts such as the Maximum Permissible Exposure and the Nominal Ocular Hazard distance. The doctors were able to detect subtle retinal changes that, under previous MPE/NOHD studies, might not even be perceived as injuries or damage.
The report is not clear on whether the aircraft altitude was 1300 ft, or whether the l@ser-to-aircraft distance was calculated to be 1300 ft. If the former, there would be an additional horizontal distance so the l@ser could enter the cockpit window (e.g., it did not come 1300 ft straight up through the bottom of the aircraft).
For purposes of this discussion we will be conservative and say the l@ser-to-aircraft distance was 1300 ft.
One of the best-known consumer handheld blue l@sers is the Wicked l@sers S3 Arctic, introduced in 2010. It is called a “1-watt” l@ser but has an actual output around 750 milliwatts (3/4 watt). The Nominal Ocular Hazard Distance of this l@ser, with a 1 milliradian divergence, is 635 feet. This means that beyond 635 feet, there is a “vanishingly small” chance of l@ser exposure causing a minimally detectable change to the eye, under laboratory conditions when the eye and the l@ser are held in fixed positions relative to each other.
So a S3 Arctic could not have caused the injury at 1300 ft. This is more than twice the “safe” NOHD distance.
A more powerful l@ser with an output of 3.1 watts and 1 mrad divergence would have an NOHD of 1291 ft. It is possible that an exposure from a 3.1 watt l@ser could have caused an injury, when the eye and the l@ser are held in fixed positions relative to each other.
However, note that the NOHD has a built-in “reduction factor” or “safety factor”. This means that the chance of injury, if someone is at or just within the NOHD, is still very, very small.
At roughly 1/3 of the NOHD, the chance of injury increases to 50%. Specifically, at 0.316 times the NOHD, there is a 50/50 chance of a l@ser exposure causing a minimally detectable change to the eye, under laboratory conditions when the eye and l@ser are held in fixed positions relative to each other. So what we are looking for is the power of a l@ser that has an NOHD of 4108 ft. (This is because 1300 ft would be at the 0.316x “50/50” point.)
A l@ser with an output of 32 watts and 1 mrad divergence fits this. That means there is a 50/50 chance that a 32 watt/1 mrad l@ser exposure under laboratory conditions could have caused a minimally detectable injury to an eye that is 1300 ft. away.
If the divergence was less — a tighter beam — then the overall l@ser power could be lower as well. This is because a tighter beam will have greater power density at a distance than the same power spread out in a wider beam. Note however, that the higher the power output of a l@ser, the harder it is to make a tight beam. Adding a focusing lens on the front of the l@ser is not significant at long distances. So it is likely that a multi-watt relatively inexpensive consumer l@ser would have a beam of 1 milliradian divergence or wider.
At 8 watts and a tight 0.5 mrad divergence, there would be a 50/50 chance that a l@ser exposure under laboratory conditions could have caused a minimally detectable injury to an eye that is 1300 ft. away. Again, 8 watts at 0.5 mrad is exceptionally tight for a consumer l@ser.
LaserPointerSafety.com received a note from a l@ser safety expert who read the above.
This person wrote “Some of the more important factors are that the aircraft is obviously not stationary, and that the 1300 foot range (as a minimum) is still a very distant target. There is doubtless attenuation in the windscreen, so this even without considering the ED50, for this exposure to turn into a definite injury is highly improbable.”
The expert’s “best guess” was that the exposure was 2-3 orders of magnitude above the MPE “to hope to overcome the ameliorating factors (movement, windscreen, atmospheric effects, etc).” This means that the exposure was 100 to 1000 times above the Maximum Permissible Exposure. Recall that the MPE is the highest irradiance at which injury is unlikely. For a 1/4 second exposure that would be 2.54 milliwatts per square centimeter. So the expert’s best guess is that the actual irradiance, to cause the stated injury, would be around 254 to 2540 mW/cm².
Earlier we established that a l@ser with an output of 3.1 watts and 1 mrad divergence would have an NOHD of 1291. Another way of saying this is that a 3.1 watt, 1 mrad l@ser beam would be just at the Maximum Permissible Exposure, at the aircraft windscreen.
What this expert is now guessing is that the l@ser was 100 to 1000 times more powerful, or around 310 to 3100 watts. For a visible blue l@ser, this is exceptionally powerful. It would not be a consumer-type handheld l@ser.
If true — if a blue l@ser beam was able to cause the injury described in the paper — then it must have been a l@ser with special characteristics such as high power and tripod tracking, which is unlike almost all other reports of consumer l@ser misuse.