|Letter to the Airline
Pilots Security Alliance regarding their "security-alert",
"Reports of Laser Beams Targeting Aircraft", and subsequent correspondence.
On Januray 1, 2005, the Airline Pilots Security Alliance webpage posted a "security alert" warning pilots about the recent spate of incidents involving lasers being directed at aircraft. This so called "security alert" is so full of undocumented facts, fallacious statements, and erroneous conclusions that I felt it necessary to call them on it. First, I have quoted the contents of this security alert as it appeared on their website on January 14, 2005, the day I first learned of the alert. Second is my letter to David Mackett, the president of the APSA, emailed on Jan 15, 2005.
A response was received on January 16, 2005 from David Mackett.
Added my reply of January 17, 2005.
Added response of January 25, 2005 plus FAA .pdf Report on Laser Pointers.
Added my reply of January 25, 2005.
Added reply from APSA of January 26, 2005.
Reports of Laser Beams Targeting Aircraft
Pilots Security Alliance has confirmed 8 very recent reports of
aircraft cockpits being illuminated by steady or pulsing laser beams in
flight in multiple locales in the United States. We have
additional unconfirmed reports. The reports range from pilots
reporting lasers shining into the skies near their aircraft but not
actually shining in the pilots eyes, to a beam near CLE reported in the
cockpit and appearing to track with the aircraft, for 15-20 seconds,
and damaging the pilot’s eyes, while the aircraft flew at
feet, 15 miles from the airport. A Cessna 172 pilot suffered
temporary blindness when his inboard port wing and cockpit were
illuminated by a very bright green light last month. Among
unconfirmed reports are 3 NWA aircraft reporting laser hits on
12/15/2004. The FBI is investigating some of the reports, but
not clear they are aware of all of them as yet.
The lasers are reported to emanate from the ground, and appear as a green beam when shining into the sky past an aircraft, or as an extremely bright, small green dot in the far distance (up to 30 miles, estimated) when viewed straight on.
Incidents have been reported near CLE (altitude 8500’, 15 miles from airport, 250 kts., 20 second illumination, laser tracking with the aircraft, pilot injured); SLC (Sep 2004, 5 miles from airport on approach, pilot possibly injured); DAB (C172, altitude 1200’ portion of aircraft illuminated, pilot injured); DEN, IAH, TEB, and DET (3 NWA aircraft reporting [unconfirmed]).
Some media have suggested pranksters playing with laser pointers given as Christmas gifts may be responsible. However, some of the incidents happened well before Christmas and we have not experienced similar activity during past Holiday Seasons, even when laser pointers were first marketed. More importantly, some of these reports (particularly where the laser hit an aircraft at altitudes of several thousand feet) are not consistent with low powered, “pen-lasers” or laser pointers, which have a range of only 1600 feet and would have great difficulty being held on an aircraft. These reports imply a much more powerful “industrial” laser or an anti-personnel laser designed to be a weapon, possibly with tracking and/or sighting equipment attached (if the reports of the laser moving with the aircraft are correct). Both of these lasers are much more sophisticated and expensive and generally not possessed by average citizens.
In the CLE incident, the laser was reportedly fired from a point perpendicular to the aircraft’s flight path, requiring the beam to track the aircraft from the side as it traveled at roughly 290 mph.
The damage a laser is capable of doing varies with the power and sophistication of the laser. A laser pointer, with limited range and a pencil thin beam is usually only a nuisance to aircraft and may cause eye damage only when flashed at persons within a few hundred feet). An industrial laser of the type used in the construction industry, especially if it is augmented for use as a weapon, is powerful enough to cause retinal burns and immediate or delayed temporary loss of vision to a pilot from great distances and at intermediate altitudes. During critical phases of flight, a properly targeted industrial laser could obviously be catastrophic to the flight’s safety if it blinds the pilot(s).
A military-grade anti-personnel laser is designed to blind pilots and other targets instantly. The beam may be enlarged to encompass the entire cockpit, lazing both pilots simultaneously. These lasers typically use robust targeting and tracking capabilities to keep them locked on a target, and are of a size that may be mounted in a cargo van or hotel room window near an airport. A few years ago, an American intelligence pilot shadowing a Russian ship received substantial eye damage due to a laser (possibly a laser rangefinder) being shined at him from the ship’s deck.
The human eye is most sensitive to green laser light and less so to red light, therefore a green laser is more dangerous at a given power than a red one. Some lasers operate in non-visible spectrums like infrared, meaning the pilot cannot even know a laser is targeting him/her until he experiences eye pain and/or vision deterioration. There is no evidence an anti-personnel laser has fallen into the wrong hands.
A laser burn occurs in .001 seconds, while it takes the human eye .25 seconds to blink, making it unlikely a pilot may avoid damage by looking away or blinking if the laser hit is direct (we would make the point that looking away from a very bright light is still recommended, since the hit may not be direct – certainly do not look toward a very bright, ground-based light while flying – even if the light appears very far away). The damage a laser is capable of is limited to visual interference. There is no evidence such lasers have the ability to damage the aircraft structure, fuel systems or instrumentation.
Existing protection against lasers usually involves laser goggles. But, since the goggles’ protection is wavelength-specific, they are of little use if the wavelength of the offending laser is not known. Laser detection is being developed now. Optra, Inc., a Boston technology firm, has developed a laser detector not unlike an automobile radar detector. The unit sits on the instrument panel of an aircraft and alarms if a laser is present. It then provides GPS data of the hit, general beam origin, wavelength, exposure time and whether the laser is dangerous. Currently, this detector costs $2500 per unit and can be deployed to an airline within 6 months. The unit has not been deployed to any airlines yet. Optra, Inc. expects to sell the detector for $500 per unit within a few years.
APSA is very concerned some of these incidents appear deliberate and may involve sophisticated equipment. We recommend pilots immediately adopt a policy of never looking directly at bright, ground-based lights (no matter what the distance) during flight, and look away and operate by instruments if they observe a laser directed at the aircraft and include this information in crew briefings.
If you have been involved in a lazing experience, please report it immediately to Air Traffic Control and advise us at David_Mackett@secure-skies.org.
To: David Mackett, President APSA
re: "Reports of Laser Beams Targeting Aircraft" as posted at
I happened to come by your "security alert" from a message posted in a
laser related internet newsgroup. After reading, it was painfully
obvious to me that there are crucial pieces of information in this
"alert" that are unfounded, unsubstantiated, and just plain erroneous.
I am taking the time to write this email to provide some factual
information in an effort to prevent an inappropriate knee-jerk reaction
to these incidents.
I am in no way attempting to minimize the seriousness of the incidents.
Shining a laser indiscriminately at anyone is a foolish thing to do. If
the perpetrators of these incidents can be caught, they should be
punished to the fullest extent of the law.
However, as a laser enthusiast, I don't want to see my hobby adversely
affected due to the actions of a few bad apples. Please don't throw out
the whole barrel. As an experienced hobbyist, I am very aware of the
dangers of lasers to vision. I am also becoming increasingly aware of
the amount of erroneous information that is being spread about lasers.
My fear is that this erroneous information will be used to make poor
decisions about the availability of lasers and their use.
I would like to address these fallacious errors by providing hard
numbers and facts to prove that in at least two of the incidents, the
ones being given the most attention, that it was impossible for the
pilots eyes to have been injured by the laser itself. I will then offer
an alternative explanation.
You cite several incidents in your "security alert", but only give any
useful information for two, the altitudes of the aircraft, 8500 and 1200
feet. Since we do not know from what distance the laser actually was,
I'll assume a worse case scenario and accept those distances as the
actual distance to the aircraft. I am also forced to make the assumption
that this altitude was AGL and not MSL.
Laser beams do not go straight. Although they start out very small, a
couple of millimeters typically, they do spread out. This is properly
called divergence, and is an important quality of a laser that is stated
by the manufacturers. The divergence is stated in units of radians and
typically a laser has a divergence on the order of milliradians.
A simple explanation of a radian is that 1 radian means for X distance
traveled by the light, it will diverge X amount. That is, if the
divergence was 1 radian (which is approximately 57 degrees), at 1 foot
from the laser the beam will have spread in size to 1 foot in diameter.
Since the best lasers have divergences approaching 1 milliradian, I will
assume a best case and use 1 milliradian as the divergence. 1 mR means
that at 1000 foot distance, the beam will be 1 foot in diameter.
In the two cases, that means the beam diameters at the plane would be
8.5 feet and 1.2 feet, respectively. The laser light would be spread out
in an approximately circular area of these diameters. The area is an
important fact here. For these two cases, the areas are:
8500 ft - 8.5 ft = 102 inches = 8171.28 square inches
1200 ft - 1.2 ft = 14.4 inches = 162.86 square inches
The fully dilated human eye, as a pilot might have flying at night, has
a pupil diameter of 7 mm, or about .276 inches. This is an area of about
0.0598 square inches.
Since the amount of light entering the eye is all that is important, we
can calculate how much of the laser actually enters the eye. Since we
have calculated the areas of the laser beams and the area of the pupil,
it is simply a matter of dividing one into the other. For the two cases
8500 ft - .276 divided by 8171.28 = about 0.00338%
1200 ft - .276 divided by 162.86 = about 0.16947%
Now that we know what percentage of light enters the eye we can
determine how much power actually enters the eye. If we assume a good
laser pointer putting out the maximum legal limit of 5 milliwatts:
8500 ft - 5 mW x 0.00338% = 169 nanowatts (nW)
1200 ft - 5 mW x 0.16947% = 8.4735 microwatts (uW)
Now that we know how much laser energy is entering the eye we can then
refer to the appropriate regulations to determine the classification and
safety of this power level. This regulation is 21CFR1040 and is available
from the CDRH on the FDA's website at,
From this document it can be found that a Class I laser for visible
wavelengths is defined as having less than 390 nanowatts of power for
10,000 seconds duration. Class I is described as "levels of laser
radiation are not considered to be hazardous." This is the lowest
classification of lasers by the CDRH.
We can conclude that if the laser was a typical green laser pointer
that it is impossible for there to have been any eye damage to the
However, it is possible that the laser was more powerful than this. We
can work the calculations backwards from the point that would cause eye
damage and determine the power of the laser at the source. The
classification where lasers become an acute viewing hazards is Class
IIIb. The power levels for visible Class IIIb lasers ranges from 5mW to
.5 watt. Since the minimum is 5mW we will use that value.
Working backwards means we must calculate backwards assuming 5mW of
laser power is entering the eye. We've already calculated above what
percentage of the beam enters the eye, so we just do the math in
8500 ft - 5mw / 0.00338% = 147.9 watts
1200 ft - 5mw / 0.16947% = 2.95 watts
For these two cases it has been determined that the laser for the 8500
foot distance must be about 150 watts, and for the 1200 foot distance,
can be about 3 watts. The most powerful 532nm (green) lasers that are
readily available rarely exceed 50 watts. 3 watts is very doable but
still not common to the average person. A used 3 watt 532nm laser still
costs several thousand dollars. Also, this is not even in the realm of
modified laser pointers and lower cost laser modules.
There are other types of lasers that are greenish in color such as an
argon laser. However, these lasers are extremely bulky, weigh hundreds
of pounds, require 3 phase 440v power at 70 amps/leg, and several
gallons of water per minute for cooling. Not exactly something some
prankster is going to be lugging around. The DPSS 532nm laser is much
more compact and more efficient power wise.
Another factor to consider is that a 3 watt laser shining up into the
sky is going to be visible to anyone on the ground for at least five
miles. I would be curious to know if during these incidents anyone on
the ground saw the laser. Until such a story could be confirmed I find
it unlikely then that a high powered laser was used.
Also, I assumed a best case scenario of 1 milliradian divergence. Most
lasers have a higher divergence, which would mean the beam spreads out
even faster and would require an even higher powered lasers. If we
double the divergence to 2 mR, the power required for the same power at
the given distances quadruples. For the two cases this translates to 592
watts and 12 watts. The first has maybe only been seen in the lab, and
the second is possible, but even more expensive and difficult to use.
I think another answer to the pilots "injuries" is more likely. I think
it is much more likely that some stupid person was showing off their
laser pointer and tried aiming it at an aircraft. The pilot was startled
by the light, a light bright enough to cause an afterimage. The pilot
then starts rubbing their eyes. After images don't go away quickly so the
pilot keeps rubbing their eyes until they become irritated and sore.
They may even cause slight corneal abrasions. It feels like they have
sand in their eyes. The pilot then concludes that the laser caused eye
True retinal damage from a laser is unfelt and usually unnoticed. The
burn spot is very small and will affect only a tiny part of one's
vision. The blind spot caused by this damage is quickly adjusted for by
the brain and becomes unnoticeable under ordinary circumstances. It
takes an opthamologist experienced with laser eye injuries to detect the
retinal burn, if it can be detected at all.
Further on in your "security alert" you make the statement,
"An industrial laser of the type used in the construction
industry, especially if it is augmented for use as a weapon,
is powerful enough to cause retinal burns and immediate or
delayed temporary loss of vision to a pilot from great
distances and at intermediate altitudes."
I presume you are referring to the lasers used on construction sites as
levels and survey lines. These lasers are Class II lasers, a lower class
that laser pointers. I would also like to know how they can be
"augmented for use as a weapon." It is not possible except in certain
cases to take a laser and increase its power to any great extent. The
most likely case of an "augmented" laser is a modified green laser
pointer. This is only possible because the laser was capable of the
higher powers to begin with and turned down to the legal limit during
calibration. Even so, these 'modded pointers' are still of insufficient
power to cause eye injury in the cases cited.
"A military-grade anti-personnel laser is designed to blind
pilots and other targets instantly."
The problem is that although possible, there just aren't any "anti-
personnel lasers." Such weapons have been banned by treaty. The closest
possibility would be laser range finders, which are available on the
surplus market, but these all operate in the infrared and are thus
invisible to the eye.
"A laser burn occurs in .001 seconds, while it takes the human eye
.25 seconds to blink, making it unlikely a pilot may avoid damage
by looking away or blinking if the laser hit is direct"
What is your evidence for this statement? How do you know how long it
takes for a laser to burn the retina? It is all highly dependent on
how much power there is. An extremely high powered laser could do damage
in milliseconds, but a lower powered laser might take seconds.
I would have to conclude that after reading your "security alert" and
the fallacious statements, undocumented facts, and erroneous
conjectures, that this "security alert" is nothing more than an attempt
to create a state of unfounded fear regarding lasers.
Again, I do not mean to belittle the seriousness of lasers being
pointed at aircraft. These incidents, if found to be true and accurate,
need to be dealt with. However, to imply such things as laser "augmented
for use as a weapon" and to state that pilots have sustained eye damage
when the facts simply do not support such a conclusion is irresponsible
It is in the best interest of all involved that any reactions to these
incidents be based upon the facts once they have been verified.
I request that this "security alert" be retracted due to these errors
can be corrected.
received Jan 16, 2005. (sorry for the formatting, I just cut &
pasted out of my email. I did at least change it from blue text to
Thank you for your very well-presented email. Obviously, you have a wealth of knowledge about lasers that could be helpful in evaluating laser incidents involving aircraft. I hope we can call on you to assist us in areas where we have questions about lasers or their capabilities. The security alert on our site was developed after consultation with the manufacturer of a line of sophisticated green lasers, the senior engineer at a niche firm that manufactures the industry's first laser detector (which garnered a best new product award from AvWeek, and from an FAA bulletin about the capabilities and concerns about the capabilities of lasers used against aircraft, and, finally, from the bulletin the FBI issued to alert crews to terrorists interest in using lasers against aircraft.
Let me address your main points:
> I would like to address these fallacious errors by providing hard
> numbers and facts to prove that in at least two of the incidents, the
> ones being given the most attention, that it was impossible for the
> pilots eyes to have been injured by the laser itself. I will then offer
> an alternative explanation.
In two of the incidents the pilots were removed from flight status, examined at the hospital and diagnosed with retinal burns by a physician. They were not diagnosed with corneal abrasions. You cannot get retinal burns by rubbing your eyes.
> Laser beams do not go straight. Although they start out very small, a
> couple of millimeters typically, they do spread out. This is properly
> called divergence, and is an important quality of a laser that is stated
> by the manufacturers.
Yes, we're familiar with divergence.
> Now that we know what percentage of light enters the eye we can
> determine how much power actually enters the eye. If we assume a good
> laser pointer putting out the maximum legal limit of 5 milliwatts:
The "legal limit" you refer to concerns only lasers manufactured in the U.S. Much more powerful and sophisticated lasers can be imported legally. Lasers of 50mW are easily obtained on the internet for several hundred dollars.
> > We can conclude that if the laser was a typical green laser pointer
> that it is impossible for there to have been any eye damage to the
First, we don't know if the laser was a "typical green laser pointer" and the fact is there WERE retinal burns to two pilots' eyes. Second, retinal burns are not our primary concern. Our concern (eye damage or not) is a laser causing temporary blindness to a pilot during a critical phase of flight (as happened several nights ago in BUR when a SWA airplane was lazed very close to the airport, blinding the pilot). This capability is within that of a sophisticated green laser pointer.
> However, it is possible that the laser was more powerful than this. We
> can work the calculations backwards from the point that would cause eye
> damage and determine the power of the laser at the source. The
> classification where lasers become an acute viewing hazards is Class
> IIIb. The power levels for visible Class IIIb lasers ranges from 5mW to
> .5 watt. Since the minimum is 5mW we will use that value.
Why would you not use the max value instead of the mininmum?
> For these two cases it has been determined that the laser for the 8500
> foot distance must be about 150 watts, and for the 1200 foot distance,
> can be about 3 watts.
Again, this is the minimum value, according to your calculations. The laser's power has not been determined.
he most powerful 532nm (green) lasers that are
> readily available rarely exceed 50 watts. 3 watts is very doable but
> still not common to the average person. A used 3 watt 532nm laser still
> costs several thousand dollars. Also, this is not even in the realm of
> modified laser pointers and lower cost laser modules.
We agree. Our Security Alert pointed to the use of sophisticated lasers in the cases where the pilots' eyes were medically damaged. Doesn't change the fact that flash blindness, not eye damage is our primary concern and THAT can (and apparently has ) been done with a green laser pointer.
> There are other types of lasers that are greenish in color such as an
> argon laser. However, these lasers are extremely bulky, weigh hundreds
> of pounds, require 3 phase 440v power at 70 amps/leg, and several
> gallons of water per minute for cooling. Not exactly something some
> prankster is going to be lugging around. The DPSS 532nm laser is much
> more compact and more efficient power wise.
We have not suggested these incidents are caused by "pranksters" any more than someone shooting at passing cars from an overpass is a "prankster."
> Another factor to consider is that a 3 watt laser shining up into the
> sky is going to be visible to anyone on the ground for at least five
> miles. I would be curious to know if during these incidents anyone on
> the ground saw the laser. Until such a story could be confirmed I find
> it unlikely then that a high powered laser was used.
We have no reports of neighbors seeeing lasers shining into the sky. There are two reports of pilots seeing lasers shining in the sky near their aircraft. We don't believe 3 watt lasers were used.
> I think another answer to the pilots "injuries" is more likely. I think
> it is much more likely that some stupid person was showing off their
> laser pointer and tried aiming it at an aircraft.
Clearly that is a primary possibility in some of the events, particularly AFTER the story made headlines.
The pilot was startled
> by the light, a light bright enough to cause an afterimage. The pilot
> then starts rubbing their eyes. After images don't go away quickly so the
> pilot keeps rubbing their eyes until they become irritated and sore.
> They may even cause slight corneal abrasions. It feels like they have
> sand in their eyes. The pilot then concludes that the laser caused eye
> True retinal damage from a laser is unfelt and usually unnoticed. The
> burn spot is very small and will affect only a tiny part of one's
> vision. The blind spot caused by this damage is quickly adjusted for by
> the brain and becomes unnoticeable under ordinary circumstances. It
> takes an opthamologist experienced with laser eye injuries to detect the
> retinal burn, if it can be detected at all.
A doctor detected retinal burns in two events.
> Further on in your "security alert" you make the statement,
> "An industrial laser of the type used in the construction
> industry, especially if it is augmented for use as a weapon,
> is powerful enough to cause retinal burns and immediate or
> delayed temporary loss of vision to a pilot from great
> distances and at intermediate altitudes."
> I presume you are referring to the lasers used on construction sites as
> levels and survey lines. These lasers are Class II lasers, a lower class
> that laser pointers. I would also like to know how they can be
> "augmented for use as a weapon."
We were referring to powerful industrial lasers with robust tracking equipment attached.
It is not possible except in certain
> cases to take a laser and increase its power to any great extent. The
> most likely case of an "augmented" laser is a modified green laser
> pointer. This is only possible because the laser was capable of the
> higher powers to begin with and turned down to the legal limit during
> calibration. Even so, these 'modded pointers' are still of insufficient
> power to cause eye injury in the cases cited.
Our information is that a 50mW laser can, in fact, cause eye injury, but, again, that's not our primary concern.
> Another statement,
> "A military-grade anti-personnel laser is designed to blind
> pilots and other targets instantly."
> The problem is that although possible, there just aren't any "anti-
> personnel lasers." Such weapons have been banned by treaty. The closest
> possibility would be laser range finders, which are available on the
> surplus market, but these all operate in the infrared and are thus
> invisible to the eye.
Incorrect. The chinese ZM-87 (or similar; don't have the designate in front of me at the moment) is a military anti-personnel laser currently deployed. Additionally, anti-personnel lasers are currently in use against our troops in Iraq, treaty or no. There ARE in fact antipersonnel lasers and these are exactly what terrorists are interested in buying or converting (as reported by FBI).
> Yet another,
> "A laser burn occurs in .001 seconds, while it takes the human eye
> .25 seconds to blink, making it unlikely a pilot may avoid damage
> by looking away or blinking if the laser hit is direct"
> What is your evidence for this statement? How do you know how long it
> takes for a laser to burn the retina?
> I would have to conclude that after reading your "security alert" and
> the fallacious statements, undocumented facts, and erroneous
> conjectures, that this "security alert" is nothing more than an attempt
> to create a state of unfounded fear regarding lasers.
Brian, let me get emotional for just a second. There is not one fallacious statement, undocumented fact or erroneous conjecture in our alert. We are not attempting to create a state of unfounded fear. We have pilots who suddenly went blind after seeing a bright light on the ground during critical approach phases of flight, endangering the flight's success. We have pilots who were taken off flight status and diagnosed with retinal burns by a doctor. In one case, the pilot simply saw the light on the horizon, didn't rub, didn't blink, didn't think anything of it. Then, he woke up with a puffed up, bloodshot eye the next morning. 33 aircraft have been lazed in the past few weeks. I would expect many copycats once the news got out, and each copycat has the ability to endanger a flight. What concern about the above do you think is unfounded?
> Again, I do not mean to belittle the seriousness of lasers being
> pointed at aircraft. These incidents, if found to be true and accurate,
> need to be dealt with. However, to imply such things as laser "augmented
> for use as a weapon" and to state that pilots have sustained eye damage
> when the facts simply do not support such a conclusion is irresponsible
> at best.
The phrase, "converted for use as a weapon" comes directly from an FBI bulletin. The "facts" are that doctors report pilots have sustained eye damage.
> It is in the best interest of all involved that any reactions to these
> incidents be based upon the facts once they have been verified.
The facts were verified before the alert went out.
> I request that this "security alert" be retracted due to these errors
> can be corrected.
No sir. We represent 25,000 pilots whose health and safety depend on having the information vital to their and their passengers' safety. There are no errors in the alert.
To: David Mackett, President APSA
Thank you for your response to my email.
First, an error in my calculations has been brought to my attention.
I had used a wrong number in figuring out what percentage of light
enters the eye. Here are the corrected calculations with the original
erroneous results in brackets:
assuming 1 mR divergence
8500 ft - 8.5 ft = 102 inches = 8171.28 square inches
1200 ft - 1.2 ft = 14.4 inches = 162.86 square inches
fully dilated human pupil
7mm = .276 = .0598 square inches
percentage of light entering eye
8500 ft - .0598 divided by 8171.28 = 0.000732% [0.00338%]
1200 ft - .0598 divided by 162.86 = 0.036719% [0.16947%]
This is the error, I originally used the diameter .276
instead of the area .0598. I need to divide the areas.
power of light entering the eye from assumed 5mW laser
8500 ft - 5mW x 0.000732% = 36.6 nanowatts [169 nW]
1200 ft - 5mW x 0.036719% = 1.84 microwatts [8.4735 uW]
reverse calculated laser power assuming 5mW enters the eye
8500 ft - 5mW / 0.000732% = 683 watts [147.9 watts]
1200 ft - 5mW / 0.036719% = 13.6 watts [2.95 watts]
As you can see, the error actually works in favor of my argument that
it would take a very powerful laser to cause retinal burns in these
cases. My original results were off by a factor of about 4.6.
Also, something I forgot to address in my first email. I had used
the altitude of the aircraft as the distance from the laser. In
reality, this distance would have to have been greater, perhaps twice
as much, due to the angle required to get the laser to shine through
the cockpit windows and into the pilots eyes. Even when an aircraft is
on approach in a nose down attitude, a laser source straight on would
still be some distance from the ground position of the aircraft. The
effect of this is more divergence and less laser power in the pilots
eyes, necessitating a more powerful laser to reach damage threshold.
I would like to clarify that I am fully aware of the danger to an
aircraft from even a low powered laser causing temporary flash
blindness to the flight crew. The laser would not have to be of
sufficient power to cause damage to be a hazard to operations of an
aircraft during a critical phase of flight. Among my many interests
I am also an aviation enthusiast. Unfortunately I've never had the
opportunity to get my wings. I certainly wouldn't want any bright
light, laser or not, shining at my aircraft while I was attempting
a night landing.
I am still not convinced of the reality of retinal damage to the
pilots eyes. I have discussed this matter with a few people who are
familiar with laser eye injuries. Retinal burns are very difficult to
detect. It requires an exam by an opthamologist experienced in retinal
laser damage, and often times the examination is inconclusive. You
mention that the pilot's condition was determined by "a physician."
Unless this "physician" is experienced in diagnosing laser eye damage
I would be very dubious of the diagnosis. Everyone I know would be
very keen to read the medical reports.
In your reply you state,
"We have pilots who were taken off flight status and diagnosed
with retinal burns by a doctor. In one case, the pilot simply
saw the light on the horizon, didn't rub, didn't blink, didn't
think anything of it. Then, he woke up with a puffed up,
bloodshot eye the next morning."
I'll let the words of someone with first hand experience than I reply,
"I know of cases (in the company where I work) of people receiving
an exposure to a laser (visible) and thinking nothing further of
it until a retinal burn was found at the next eye exam (anyone
working directly with lasers has to be examined for retinal burns
every 2 years), no soreness, no bloodshot eyes, no puffiness.
Corneal damage would cause the symptoms they describe, not (only)
a retinal burn."
In response to why I used the minimum value instead of the maximum
for Class IIIb lasers as the basis for my calculations, it was because
this was the lowest power expected to cause damage. Remember, this was
in the part where I was calculating backwards to find the minimum
power of the source laser. If I were to have used the maximum power in
those calculations, the result would have been a higher powered laser,
which would have worked in favor of my argument. I was attempting to
determine the minimum power required under those circumstances that
might begin to cause eye damage.
In response to my question about witnesses on the ground seeing the
laser, you said you were aware of none. This would be an important
piece of information to find out. If people on the ground were able to
see the laser shining in the sky, especially from a distance, then
that would mean the laser was of significant power. Lower powered
lasers are very difficult to see from an any significant angle. They
are practically invisible except when they are directed toward the
viewer. With all the attention given these incidents, I am surprised
no one has come forward to say "I saw a laser in the sky" to the
authorities or especially the media. People love to be the center of
attention and a chance to be on TV would be tempting. Since only the
pilots have seen the laser, I'm tempted to think the lasers were of
Regarding anti-personnel lasers, I was unaware of the Chinese device
you mentioned. As far as I am aware, there is a treaty signed by most
respectable nations banning such devices as being inhumane. It is of
no surprise to me that some countries wouldn't care. However, I think
we can both agree that it is highly unlikely one of these devices is
being used. From my knowledge of lasers, an anti-personnel laser would
best be infrared. Not only does it make it invisible to the target, it
is also much easier to obtain the higher powers necessary to do
As to this FBI bulletin, would it be possible to obtain a copy of it
for examination? If it's online somewhere, a URL would suffice.
It would also be helpful having more detailed information for these
laser incidents. The only information floating around so far is the
altitude of the aircraft. This leads to too much guessing. What is the
possibility of seeing copies of the incident reports? Also, although I
doubt the possibility of seeing the medical reports themselves, further
more specific information about the eye exams would be of interest as
well. All of this information would be of interest to the laser
community at large and I would like to be able to share it with them.
In a sense the laser community has a vested interest in this problem.
My request for a retraction of your security alert should probably be
restated as a request for something less embellished. I agree that
pilots should be aware of the potential danger to flight operations
and to know how to react should they become a target. However, I
still feel that it is unnecessary to include statements about lasers
"augmented for use as weapons", "anti-personnel lasers", and possible
tracking systems. Until there is evidence of such, this is just
speculation. Speculation if not qualified can lead to rumor and rumors
have a way of taking on a life of their own.
I thank you for taking the time to have this dialog with me. With
more information on these incidents, I and my fellow laserists will
have a better understanding of the issue. Because of our combined
knowledge of lasers, with the information currently available, we are
very doubtful of the accuracy of these reports.
|Sent small note January 24, 2005 re lack of response.|
January 25, 2005.
Yes, I did get it. Sorry, we've been swamped. As to your calculations, it
is clear you're much more knowledgeable on laser capability than I am, so I
won't attempt to debate. What's really important about the laser events
(and the lasers used ) is they have caused diagnosable damage to pilots'
eyes and interfered dramatically with their ability to safely pilot an
aircraft, endangering themselves, their careers and their passengers.
Whatever power they were (visible or not visible to witnesses, sophisticated
or amateur, powerful or not) the lasers used were dangerous to aircraft. I
would like to believe (and said in interviews) these were probably
sophisticated lasers costing hundreds of dollars. I don't want to see
overregulation of a hobby either. Accepting they are lower power and STILL
capable of interfering with flight, leads down a path to increased
regulation on even small lasers, which we don't think is supportable right
I agree there's no evidence a ZM-87 was used in any of these incidents.
But, at least in two incidents (SLC, A/C 5 miles from airport; eye damage to
pilot and exposure for several seconds while the aircraft moved, and CLE,
A/C 15 miles from airport at 8500 MSL; eye damage to pilot), the reports by
professional pilots suggest (as you allude) a very powerful laser (powerful
enough to cause eye damage at great range) with the capability to track the
aircraft for 15-20 seconds. The only way to avoid that conclusion is to
discount the accuracy of these reports, which we don't have the luxury of
doing. In these cases, a laser was deliberately used as a weapon and had
the capability of being so used. The timing and scope of these incidents,
combined with a very recent FBI report suggesting their possibility, made
the allusion to "weaponized lasers" prudent.
I am trying to get permission to share the FBI bulletin. If I receive it,
it will be posted on our site. I am attaching a copy of an FAA bulletin
regarding laser dangers to pilots. [click to read PDF file]
We also are expecting two 50mW lasers soon for testing. We'll have more
information when it's complete.
Additionally, our security alers expire four weeks after the last confirmed
report on their content.
To: David Mackett, President APSA
I think we can both agree that any laser of any power is a hazard to
air traffic. Also, thank you for the document from the FAA and thank
you for the effort to share the FBI memo.
I realize that you are a busy person, but I would like to continue our
dialog focusing on the issue of pilots receiving eye damage. I'm sure
you can understand that from our point of view having a knowledge of
lasers, we find it difficult to believe that there has in fact been any
actual eye damage. I and my fellow laserists would really appreciate
any help in obtaining more detailed information on the diagnoses. To be
blunt, I guess we need proof. I am hoping you are in a position to help.
If in fact there has been verifiable eye damage from a laser, then this
implies that these incidents may represent a concerted effort by someone
to target aircraft with malicious intent as opposed to someone playing
around negligently. But until we see some evidence that there is laser
induced eye damage, we are hard pressed to accept this conclusion
knowing what it would take to accomplish.
I see your group is going to do some testing. I would appreciate being
informed of the results and being able to share it with my fellow
Once again, I thank you for your time.
January 26, 2005
I have only the information I received, which is that several pilots in the
early incidents had medically diagnosed eye damage and were removed from
flight status. It's well-beyond my purvue to see their medical records and
I rely on reports from their airlines, the FAA and, in one case, first hand
The reason our bulletin was worded the way it was is that we were (and
remain) very concerned that the early incidents were NOT consistent with
amateurs playing with laser pointers and may have been something more. The
fact that police have made two arrests in the subsequent incidents has led
the public to believe this was all an amateur prank. That's just not
consistent with the information we have about the first incidents in their
I also believe a malicious laser attack would take a very sophisticated and
concerted effort - almost beyond the realm of beliveability. But, if you'd
told me on September 10, terrorist teams would hijack multiple airliners,
fly them into buildings and collapse the WTC with them, I would have laughed
in your face.