I'm going to risk weighing in from the perspective of a background in physics (as well as avionics). Some of the physical observations here read to a physicist how aviation articles in the common press read to pilots. I think it's important for pilots to understand the mechanics behind this topic.

The power level of "high power" diodes purchased by consumers is typically in the tens to hundreds of milliwatts. Inexpensive visible light diodes which claim to be several watts are invariably mis-sold - I come across them now and again and measure them with a thermal effect laser power meter. I think it's reasonable to generalise that a laser pointer bought on eBay is unlikely to be more than a few hundred milliwatts of output power. It's worth noting that most (almost all) cheap visible light lasers are pumped by a much more powerful IR laser and if an appropriate IR filter is not installed the output power will be much higher than that of the visible component alone. IR light will pass the cornea and heat up the retina as easily as most visible light. Only as the wavelength moves into UV does the effect switch from retinal to corneal damage.

That's not to say that somebody who genuinely wishes to incapacitate a pilot might not have purchased a high quality visible laser with several watts of output power. It will have cost them several hundred pounds and I suspect the attackers under discussion here do not fall into this category.

At close range the output of even a low powered diode in the visible spectrum is very dangerous to sight. An 808nm (green) 50mW laser shone at close range into the eye for more than a few milliseconds will could inflict permanent injury. Laser pointers around 200mW are widely available and these could easily cause loss of sight.

Exposure is considerably reduced by distance. For incoherent light (such as a bulb) the power of the light reduces by the inverse square of the radius, which is not true for a perfectly coherent laser source. An ideal laser will have the same power at any distance because the energy does not diverge. However there are no ideal lasers, and the diodes one might purchase on eBay are very far removed from scientific grade. As the beam diverges a smaller area will contact the retina so the exposure is therefore a function of the radius of the beam at the distance of contact multiplied by duration.

At cruise altitude, or well into the climb, or early in descent, the distance of throw is substantial so the beam radius is large and the ratio of the beam area to the retina area is small. Furthermore the duration of exposure is likely to be short because it is difficult to manually track a moving target even with quite a shallow angle of incidence. As such this exposure is very unlikely to cause any damage to the retina - much higher exposures are experienced in night clubs when scanning the crowd with a moving laser (and those exposures are also calculated to be safe). I would suspect that the greater risk to flight safety in these circumstances is the surprise of the momentary flash of light, and the distraction that could result from this.

I would be far more concerned about exposure closer to the source - shortly after takeoff or on final approach. Beam radius at these shorter distances could be as little as a few centimeters even with a low quality source. There is certainly some risk to eyesight in these circumstances, whether that's permanent scarring of the retina or temporary dazzling (which can last for quite some time and is extremely disturbing). The latter effect is possibly why pilots are reporting prolonged exposure in the cockpit, even though it's unlikely that such tracking could be achieved manually. A 10ms exposure at relatively high power could easily dazzle a victim for several seconds.

In the case of the Virgin incident, I feel the co-pilot would be extremely unlucky to have suffered any permanent injury. That doesn't reduce the impact of the distraction and the distress that uncertainty of the consequences must have caused. I feel that flight crews should receive better training on these matters (beyond the occasional bulletin) which might better equip them for decision making during such events. During critical phases of flight it seems entirely appropriate to handle a laser strike as sudden incapacitation.

As for banning lasers - there's already categorisation and control for laser products. It's a matter of enforcement not legislation.

808 nm is green?

All this time I thought it was infrared... ;)

Are you maybe thinking of the very common green 532 nm DPSS laser with an 808 nm GaAlAs pumping diode?

Aren't you confusing coherence with collimation? It's the collimation that keeps the power from dropping much with distance, not the coherence, right? In fact, don't laser diodes (with a short coherence distance) often use a collimating lens?

Ha, fingers faster than brain!

Knowing the area where this incident reportedly occured quite well iwas curious to try and locate the area where the laser may have been shone from.

The track at the beginning of this thread shows a easterly departure from LHR 9R and assuming a standard Compton departure the captains estimate of about 8 miles from Heathrow puts the plane just south of Lego land themepark situated in the middle of the crown estate at Windsor. That would fit perfectly with estimates that the laser was 1-2 miles off to one side- ie to the north of track.

So I wonder if this was either an errant laser from a show or an employee testing/fooling around with one. They have a lot of laser shows there and it does seem a bit of a coincidence that this occured not just close to lego land but just the right distance to the south-so maybe just an error on an operaotrs or technicians part.

Not an ideal location for laser shows though being under SID tracks from both easterlyand westerly departures from LHR-presumelably they normally operate restricted power versions

Far from perfect, as in Boeings like the B737 and B777 with lcd or led displays you will be unable to read them.

Pax Britanica
 

At last a rational explanation, thank you for researching that.

Would you mind sending that explanation to the BBC who are drooling at the idea of high powered l@sers in the hands of Windsor toffs bringing down aircraft.

Legoland is closed until March.

To the public I presume?

Any chance they might be undergoing any testing/training/other there currently before reopening in March?



Not at all suggesting this is the likely source of the laser, merely open to considering all possibilities at this stage

Legoland opening
 

Sorry Airclues. the place is open:

February half term Junior Builder Week at the LEGOLAND Resort Hotel will take place from 12th — 20th February from just £140 per family!

I actually did wonder if the place was open this early not realsiing it was indeed half term hence my comments about 'testing'. What does interest me is what sort of lasers they use because the pics on the web look pretty spectacular but as I pointed out tis just to the north of the Compton SIDs for easterlies and ty much over it at the point where the 27R SID is in a right turn to pick up the track to Compton.

All that said I am sure legoland would have had to pass some kind of check on laser shows as it is so close to LHR

Some of you will know who I am. Most probably don't. However, I am the Captain in this event. I haven't been involved in Pprune for many years, but I used to be very involved, for which I offer apologies if appropriate!

It's been fascinating to read the speculation, and very interesting to read some of the factual postings in this thread. I don't take offence at those who question my decisions - all captains' decisions should be challenged and tested to see if they are indeed appropriate and proportionate, and this forum is as reasonable a place for that to happen as any.

For now, I won't be offering any significant justification or explanation. There's likely to be more investigations to be carried out, and I don't want to pre-empt, prejudge or influence any of those, or compromise my ability to speak freely to those who need to hear what I have to say. I'd just like to thank those who have some faith that I had some idea of what I was doing and why, and those who helped me get the job done both on the ground and in the air.

For those who have any relevant expertise, it was a red beam, not a green one. It was indeed reported as and when it happened. The pictures we got show its ground position (which wasn't Legoland as far as I can see), and will hopefully help those in the know to estimate its power and provenance.

As was reported in the news, the FO did receive retinal damage from what appeared to be a 'lucky' passing sweep, but it's not permanent and will heal fully. There was no visual impairment during the flight, but there was no way of knowing (for me) that that would continue to be the case.. The symptoms were slow in making themselves apparent. That's about all I'm prepared to say for now.

For the terminally pedantic, yes, I admit my Pan call was incorrectly phrased!

Thanks for the update, we really appreciate it! Great news about the FO's healing prospects. :ok:

As you know, endless debates about proper R/T procedures and how to do practice PAN's are classic PPRuNe topics from the 'old' days. It's a cultural thing I would say. ;)

Good Form scroggs!

i am wondering why the ac cockpit windows cannot be coated with the same material as military ac and equipment against laser.
In the military, many of the weapons systems use lasers for rangefinding and guidance, and I know the gunsights and windows/ports on tanks are coated to reflect the laser from direct and return, with no optical reduction.
They also use this coating on building windows so that a laser cannot be used to listen to conversations inside.

Edit: Found this on a lab website..

A laser is a light source that can be dangerous to people exposed to it. Even low power lasers can be hazardous to a person's eyesight. The coherence and low divergence of laser light means that it can be focused by the eye into an extremely small spot on the retina, resulting in localised burning and permanent damage in seconds. Certain wavelengths of laser light can cause cataracts or even boiling of the vitreous humor, the fluid in the eyeball. Infrared and ultraviolet lasers are particularly dangerous, since the body's "blink reflex", which can protect an eye from excessively bright light, works only if the light is visible.

egsc_h17....people pull them out of color laser printers..very powerful uncontained.

Great job Captain!

Wishing your F/O a speedy recovery!!

Those are - to me at least - good points, and, as I'm the star player in today's teacup tornado, hopefully I'll get a chance to ask some pertinent and hopefully difficult questions which can be tossed into the melting pot as 'the authorities' temporarily agonise over what to do about this before something else moves their attention elsewhere.

If anyone with authoritative knowledge of mitigation measures which can relatively easily be applied to aircraft would like to PM me, I'm happy to include their contributions to the conversation. Please, I don't want - indeed I will actively reject - casual speculation, 'what-ifs', or otherwise non-expert inputs. I have a temporary but hopefully powerful opportunity to have a say, and I want to make sure that what I say has some weight. I'm well aware that terminal obliteration of the scrotes may be the ideal solution, as well as introducing the sellers of these devices to a man-eating monster of my choice, but it's unlikely I'll persuade anyone to legislate for that. Indeed, it's unlikely I'll persuade the legislators to do anything, and I'll leave that argument to the unions and other interested parties. Right now, I'm interested in what we as operators can do.

There have been tests:

Erm, not sure what you are talking about. No aircraft I have ever heard of had laser protective coatings on the windows.
Lasers are very effective against military aircraft which is one reason they are banned I believe. We certainly would never blind an enemy pilot of course. That would be unsportsmanlike.


I'm afraid you have been reading bad fiction.
You cannot stop an optical laser without affecting vision through a port.

Lasers used to listen to conversations are bouncing off the window and the vibration of the window causes doppler shift which is detected. Coatings won't change that one iota.

"Safe" l@ser energies
 

Regarding the "safe" energy levels, does anyone know how what the assumptions of the pupil size are? If the "safe" estimates are based on a normal (day adaptation) pupil, wouldn't the resulting figure be an overestimate for a dilated (night adaptation) pupil?

According to wikipedia, a normal diameter of the entrance pupil is about 4mm, ranging from 2mm (bright) to 8mm (dark), so the underestimate might be with a factor between 4-16.

Just my SEK .10.

Maybe we need to retrofit all aircraft with nuclear blast shades, as installed on the B52:

B-52 Cockpit for Sale, Boeing Stratofortress and other military aviation Memorabilia

That will surely keep our eyes protected?:E

Thank you scroggs.
Above all, it's good to know there was no permanent injury.

I'm also very glad to read that there's no permanent injury - and well handled Scroggs and your team, slightly dodgy but perfectly clear Pan call notwithstanding.

An article that appeared last night on The Conversation is somewhat relevant, but offers no particular hope of any quick fixes.

https://theconversation.com/thousand...ssengers-54863



One question from me, that I hope somebody might be able to answer. What's the investigative mechanism for an incident like this?. It clearly wasn't an accident, so presumably it's not AAIB's job. I know that CAA take a deep interest and publish statistics, and I'm sure the police are interested when there's anything for them to usefully go on. Doubtless Virgin and BALPA are also quite interested.

But what's the exact mechanism for investigating, then reporting, attacks on safety like this - if only so that I can bookmark the likely location of any future reports to read when they come out.

G

Well done scroggs :ok:

It sounds well handled and you don't have to justify your actions, nobody with any real flying experience would have questioned it.

As for the R/T, I wouldn't worry, it may not have been textbook, but it was perfectly unambiguous.
We practice things over and over, getting them perfectly right, so that on the day we get them "right enough". Nobody could have been in any doubt hearing that call.

Glad to hear it's only temporary injury to the FO, hopefully he is fully recovered and back flying again soon.




I'm glad you are trying to make a difference while you still have some influence, hopefully it is enough for the powers that be to sit up and take note of what is probably one of the biggest external threats to aviation safety after drones.

The way I understand these coatings is that they do work. But for only a specific light frequency and do create a reduction of tranceperancy. So as useful as a chocolate tea pot then.

Capt Scroggs

pardon my speculation about Legoland -it did seem to fit the bill well.

Very glad to hear that your colleague is and will be OK , I am sure he must have been very worried for a while given the importance of eyesight in your job.

The HSE document HSg95 (The Radiation Safety of Lasers Used For Display Purposes) has a section on calculating MPE levels. They recommend using a 7mm pupil diameter. This is due to most laser shows taking place at night or inside darkened venues.

Regarding Legoland, as an entertainment based organisation (and I suspect their operations are highly professional) I would expect them to be aware of the requirements for using lasers and searchlights outside and therefore notified the CAA with the relevant paperwork to obtain prior authorisation.

I have used high powered lasers argon lasers (up to 12 watts) and pulsed Copper Bromide lasers (8KW pep) outdoors and often close (under 2 miles laterally of extended runway centreline) to airports. At all times I had complied with CAA and ATC requirements and never had any issues. Although as a professional working in this field, we were far more aware of the consequences and repercussions if we got it wrong.

Sorry if i missed it but do we have now a firm confirmation that the aircraft was around 8000ft ? If so it must have a very powerful beam, something way beyond what could be laying around Legoland...

The link of Shannon ATC audio I posted on the first page of the thread seems to have gone dead.

Here's a new link to the LiveAtc.net audio, the report of the position of the laser incident is at 2:00 into this nicely edited clip:

http://www.liveatc.net/forums/index.....0;attach=8695

Sounds to me like he said they were on the LON 220 (or 230?) radial at 13 miles, 8000 feet, heading 275. But, I'm not so sure now with the foreign (to a hillbilly like me ;)) accents.

If Captain Scroggs is unable to comment on specifics at the present time I certainly understand.

Check the US attack helicopters, they use laser for rangefinding and guidance.

I am afraid you havent been reading at all. The US main battle tanks have a very powerful laser rangefinder that goes to 5000m. I was on those tanks, and we tested them by burning holes in playing cards at 50m. For obvious reasons, the laser is not in the visible spectrum. All weapons sights and vision blocks are protected. Look online and see the wide range of laser safe glasses, it is just a coating on the glass, and many are clear.

Not true, look at the coatings of the windows at DMAAC. The coating is specifically for laser listening devices. The coating has a radially diffuse pattern that scatters the laser, rather than allowing it to return. No return, no doppler shift.

http://i67.tinypic.com/2i8al4k.jpg

Interesting question Genghis. I don't know the answer so I'll keep my two penneth brief. I suspect it will all kick off with a MOR, then all agencies with an interest will become involved, CAA, police, AAIB (accident prevention) and ATC for starters, plus Virgin.

Uhh underfire ?
 

Suggestion - when one uses an acronym, especially out of range of the subject matter or blog participants- try spellIng it out at least the first time.


You probably meant the Defense Mapping agency aerospace center ?? :ugh:

And where do we find info on window coatings of that agency ?

This definition appears very rarely and is found in the following Acronym Finder categories:

• Military and Government
• Organizations, NGOs, schools, universities, etc.

Underfire.

I don't think you are really making sense.

Laser rangefinders that are not in the visible spectrum can of course be blocked without causing optical degradation through a port. This cannot be done for a visible laser for the simple reason that visible lasers are in the visual spectrum. To stop them you must block that bit of the visible spectrum. This, by definition degrades the optics.
Any goggles are exactly the same, and unless they block multiple frequencies will only protect against one laser frequency despite there being many out there.

Re the window coatings to protect against listening in.

B@llocks. Some energy will be reflected back, and that's all you need.

Quote from PDR and I can't remember how to do quotes, can't be bothered to find out and am even less bothered to provide much by way of justification for my post. It happened.

I was lasered recently at 7000' near MAN

Can you provide any independent cites for this? I'm just baulking a little bit at the marksmanship required to target an aeroplane's cockpit windows from a range of several miles and would like some confirmation that it actually happens (and with what equipment).


No I can't. I just made it up because I was feeling left out.:rolleyes:

Just brainstorming here...

Maybe positioning a tethered balloon/blimp, with laser detection and precise locating ability, in areas of known attacks on aircraft would help in apprehending the perpetrators so they could be prosecuted.

I assume the military must already have such equipment.

Just read at Pope's plane reports laser flash during Mexico landing - BBC News that the Pope's plane has been l@sered just prior to landing at Mexico City.


Cheers!

returning to my Legoland speculation I too would be absolutely amazed if their displays were not very thoroughly checked and approved by CAA and possibly other agencies.

What does intrigue me is the , no doubt informed comment, that their lasers would not represent any threat to aircraft as they wouldnt reach that kind of height. Seeing as they put on quite spectacular display leads me to ask what on earth reason would an individual have ,or be able to obtain, something much more powerful and potentially dangerous than that used in a major entertainment complex where they no doubt have competent professional people operating their system

Hull police get a result.

Hull man jailed for laser attack on police helicopter - BBC News

Hull man jailed for laser attack on police helicopter

They do, however, its normally attached to something.

http://www.raf.mod.uk/rafcms/mediafi...3CA29B8D49.jpg

A So called aviation expert has just Tarred all plane spotters as Nuts Pointing Lasers at Planes (Has he seen any one Doing this?)

"Aviation expert Julian Bray said so-called aircraft spotters would play "laser tagging" games, where they would try to shine a beam onto the fuselage of an aircraft."

I see some one Pointing a Laser at any Kind of flying machine 999 is my 1st response my 2nd :mad::mad:

Virgin Atlantic flight back in UK after 'laser incident' - BBC News