Laser threat defence
Joined: Feb 2016
Posts: 5
Likes: 0
From: Legendary Lighter then Air city, Akron Ohio
Some of you may be wondering why I don’t just specify off the shelf laser safety goggles.
The issue with that is that if Captain Bloggs buys low cost, off the shelf gear, he runs three risks.
Risk One, There are low cost, uncertified, “fake” googles out there, made by the same folks who sell the pointers. While many of the pointer engineers have Masters and PhDs in laser engineering, one does not expect them to be well versed in the design and test of a critical safety device. Please believe me that it is fairly difficult to expect the colored dyes in a 50$ pair of injected molded glasses can withstand high amounts of laser energy without the plastic bleaching or work at the correct laser wavelength, without lab certification to national standards. I find it sad that there are 15$ fakes on auction sites that do not pass even simple home lab tests…
Risk Two, The glasses may be incompatible with the cockpit displays. If the cockpit is Blue-Green ANVIS compatible, for example, most “orange”laser safety glasses for the common 532 green wavelength may adsorb most of the instrument lighting.One would not want a unprepared “Child of the Magenta” to be unable to see a critical display during critical flight. Typically, Aviation Laser Safety Devices must be evaluated for human factors and cockpit compatibility.I’ve hit my head and tripped several times in the lab, because my glasses which protect against all the laser wavelenths present, are too dense to allow me to see obstacles in a darkened lab. Thus “Secondary” hazards must be evaluated.
Risk Three, as we shall see in the following examples, the “Optical Density” of the glasses must be designed to match the level of annoyance provided by the laser. There is no reason to lose sixty five percent of visible light transmission when the “threat” is not great. You may need what is called an “alignment” or “Aiming” goggle vs a full out hazard protection device. You may also need a more expensive custom device which counters the threat(s) but allows the pilot to function with little impairment. Full wrap around laser safety glasses are annoying to wear, and reduce the visual field. They can impair peripheral vision. And what happens when you dim the lights and displays? What happens if both the PF and PNF are wearing protection?
Thus in a flight situation, risk management review by professionals, and safety cases are important when selecting laser protection. Is Captain Bloggs, 1500 Hour CPL, qualified to decide he needs OD6 or OD3, or something custom? In most cases No…One also needs to set in the actual cockpit, light up the instruments, press “self test” on the warning lights, dim everything, and see if one is personally comfortable with the risks. Training is a huge factor.
FAA responded to the initial crisis with the 7400.G rule for professional and scientific users of lasers in airspace. This is based on the ANSI Z136.1 standard for laser safety. In the UK, it is adopted as CAP 736 by the CAA. I can work backwards from this to make a good example of the actual power levels often involved.
First of all the rules define the “Airport No Laser Zone” for two nautical miles either side of the runway centerline and three miles from the runway ends. There is no purpose for a laser to be in this area other than cloud height finders, and in some rare cases “approved laser glideslopes”.
FAA defines the Critical Flight Zone as an area that is 10,000 feet in height and extends for 10 nautical miles from the airport center. In the critical zone, a laser or searchlight shall not exceed 50 nano Watts per Square Centimeter.This level is considered visible but will not constitute a distraction or annoyance to a pilot. For calculations, this is known as the “LFED distance.
The Critical Zone Exposure Distance (CZED) is the distance from the laser source to where it reaches an irradiance of 5 microwatts per square centimeter. This level is considered the lower level for creating annoying glare or attracting attention.
FAA defines the Sensitive Flight Zone as the area where the beam Exceeds 100 microwatts per square centimeter. This level is task disruptive and where significant flashblindness and afterimages occur.This is the “SZED” distance for legitimate users of lasers, when siting their equipment.
Reference for the following data, which is not Slant Range Corrected per FAA rules, from Skyzan Laser Safety Software and the ILDA Laser Safety Officer Coursework:
For a 5 milliwatt, 1 milli-Radian Laser Pointer:
NOHD 52 Feet
SZED 262 Feet
CZED 1,171 Feet (The beam can cause task disruption to this distance)
lFED 11,170 feet, (The beam is considered annoying to this distance)
For a 1 Watt, 1 milli-Radian Visible Laser:
NOHD 726 Feet,
SZED 3,700 Feet
CZED 18,600 Feet
LFED, 186,000 Feet (Not practical in many cases, due to horizon and atmosphere, included as example)
The whole point is that the night adapted eye is amazingly sensitive. The second point is the number of damaging cases is so far miniscule compared to the personal injury cases. However I am concerned that those will rise, given time.
The NOHD is the distance for a 50/50 chance of a large damage spot on the retina.
So do you really need protection "in flight" against a legal device, probably not. But you do have to weight the issues caused by the protective device against the actual laser threat.
For the record, I’ve been “lased” by pointers while in a car, and while working at a concert in the past. At the concert I was able to secure the device involved, and get some data. I was not happy. My laser show friends now have a “No Pointer in Audience” clause on their show riders and contracts, for a couple of reasons, not the least of which is liability for the audience’s safety. ..
There simply is no need for more than 5 milliwatts of laser light to be in the hands of the general public in hand held form. FAA/USCG/US Law makes an exception for laser rescue beacons, which are highly effective.But other than that, the existing world wide 1 and 5 mW limits are enough. This is now a societal addiction problem.The real issue is lack of enforcement with the makers and vendors.The existing laws on the books need to be enforced.
Unless there are questions, my last post will be links to current aviation oriented laser safety devices.
Steve
The issue with that is that if Captain Bloggs buys low cost, off the shelf gear, he runs three risks.
Risk One, There are low cost, uncertified, “fake” googles out there, made by the same folks who sell the pointers. While many of the pointer engineers have Masters and PhDs in laser engineering, one does not expect them to be well versed in the design and test of a critical safety device. Please believe me that it is fairly difficult to expect the colored dyes in a 50$ pair of injected molded glasses can withstand high amounts of laser energy without the plastic bleaching or work at the correct laser wavelength, without lab certification to national standards. I find it sad that there are 15$ fakes on auction sites that do not pass even simple home lab tests…
Risk Two, The glasses may be incompatible with the cockpit displays. If the cockpit is Blue-Green ANVIS compatible, for example, most “orange”laser safety glasses for the common 532 green wavelength may adsorb most of the instrument lighting.One would not want a unprepared “Child of the Magenta” to be unable to see a critical display during critical flight. Typically, Aviation Laser Safety Devices must be evaluated for human factors and cockpit compatibility.I’ve hit my head and tripped several times in the lab, because my glasses which protect against all the laser wavelenths present, are too dense to allow me to see obstacles in a darkened lab. Thus “Secondary” hazards must be evaluated.
Risk Three, as we shall see in the following examples, the “Optical Density” of the glasses must be designed to match the level of annoyance provided by the laser. There is no reason to lose sixty five percent of visible light transmission when the “threat” is not great. You may need what is called an “alignment” or “Aiming” goggle vs a full out hazard protection device. You may also need a more expensive custom device which counters the threat(s) but allows the pilot to function with little impairment. Full wrap around laser safety glasses are annoying to wear, and reduce the visual field. They can impair peripheral vision. And what happens when you dim the lights and displays? What happens if both the PF and PNF are wearing protection?
Thus in a flight situation, risk management review by professionals, and safety cases are important when selecting laser protection. Is Captain Bloggs, 1500 Hour CPL, qualified to decide he needs OD6 or OD3, or something custom? In most cases No…One also needs to set in the actual cockpit, light up the instruments, press “self test” on the warning lights, dim everything, and see if one is personally comfortable with the risks. Training is a huge factor.
FAA responded to the initial crisis with the 7400.G rule for professional and scientific users of lasers in airspace. This is based on the ANSI Z136.1 standard for laser safety. In the UK, it is adopted as CAP 736 by the CAA. I can work backwards from this to make a good example of the actual power levels often involved.
First of all the rules define the “Airport No Laser Zone” for two nautical miles either side of the runway centerline and three miles from the runway ends. There is no purpose for a laser to be in this area other than cloud height finders, and in some rare cases “approved laser glideslopes”.
FAA defines the Critical Flight Zone as an area that is 10,000 feet in height and extends for 10 nautical miles from the airport center. In the critical zone, a laser or searchlight shall not exceed 50 nano Watts per Square Centimeter.This level is considered visible but will not constitute a distraction or annoyance to a pilot. For calculations, this is known as the “LFED distance.
The Critical Zone Exposure Distance (CZED) is the distance from the laser source to where it reaches an irradiance of 5 microwatts per square centimeter. This level is considered the lower level for creating annoying glare or attracting attention.
FAA defines the Sensitive Flight Zone as the area where the beam Exceeds 100 microwatts per square centimeter. This level is task disruptive and where significant flashblindness and afterimages occur.This is the “SZED” distance for legitimate users of lasers, when siting their equipment.
Reference for the following data, which is not Slant Range Corrected per FAA rules, from Skyzan Laser Safety Software and the ILDA Laser Safety Officer Coursework:
For a 5 milliwatt, 1 milli-Radian Laser Pointer:
NOHD 52 Feet
SZED 262 Feet
CZED 1,171 Feet (The beam can cause task disruption to this distance)
lFED 11,170 feet, (The beam is considered annoying to this distance)
For a 1 Watt, 1 milli-Radian Visible Laser:
NOHD 726 Feet,
SZED 3,700 Feet
CZED 18,600 Feet
LFED, 186,000 Feet (Not practical in many cases, due to horizon and atmosphere, included as example)
The whole point is that the night adapted eye is amazingly sensitive. The second point is the number of damaging cases is so far miniscule compared to the personal injury cases. However I am concerned that those will rise, given time.
The NOHD is the distance for a 50/50 chance of a large damage spot on the retina.
So do you really need protection "in flight" against a legal device, probably not. But you do have to weight the issues caused by the protective device against the actual laser threat.
For the record, I’ve been “lased” by pointers while in a car, and while working at a concert in the past. At the concert I was able to secure the device involved, and get some data. I was not happy. My laser show friends now have a “No Pointer in Audience” clause on their show riders and contracts, for a couple of reasons, not the least of which is liability for the audience’s safety. ..
There simply is no need for more than 5 milliwatts of laser light to be in the hands of the general public in hand held form. FAA/USCG/US Law makes an exception for laser rescue beacons, which are highly effective.But other than that, the existing world wide 1 and 5 mW limits are enough. This is now a societal addiction problem.The real issue is lack of enforcement with the makers and vendors.The existing laws on the books need to be enforced.
Unless there are questions, my last post will be links to current aviation oriented laser safety devices.
Steve
Joined: Sep 2016
Posts: 1
Likes: 0
From: Halifax
Thanks for great Info!
Just a word of thanks to Sim Steve, your remarks are very informative and helpful!It would also be nice to hear from the helo guys in the UK, who seem to get lased
100 times a month now, about the measures they take and procedures for dealing with this...
