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Lasers and aviation safety
Under certain conditions, laser light or other bright lights (spotlights, searchlights) directed at aircraft can be a hazard. The most likely scenario is when a bright visible laser light causes distraction or temporary flash blindness to a pilot, during a critical phase of flight such as landing or takeoff. It is far less likely, though still possible, that a visible or invisible beam could cause permanent harm to a pilot's eyes. Although laser weapons are under development by the military, these are so specialized, expensive and controlled that it is essentially impossible for non-military lasers to cause structural damage to an aircraft.
Any aviation hazard from bright light can be minimized or eliminated in two ways. First, users on the ground can exercise caution, to prevent or minimize any laser or other bright light being directed in airspace and especially towards aircraft. Second, pilots should have awareness of laser/aviation hazards and knowledge of basic recovery procedures in case of laser or bright light exposure.
Additional recommended knowledge
Lasers and bright lights
Although this article concentrates on lasers, it should be noted that other bright directional lights such as searchlights and spotlights can have the same dazzling/distracting/flashblinding effects. Searchlight/spotlight operators should take the same basic precautions as laser users. Similarly, pilots and safety officials should keep in mind that a reported "laser" incident may be caused by a non-laser bright light.
In a 1997 demonstration involving a helicopter exposed to laser light and a searchlight, produced for the television show "American Journal", both sources overwhelmed the video camera. The producers were unable to tell which was which, and in fact on the air, they identified the searchlight footage as being from lasers. 
Lasers in airspace
There are many valid reasons that lasers are aimed into airspace. Lasers are used in industry and research, such as in atmospheric remote sensing, and as "guide stars" in adaptive optics astronomy. Lasers and searchlights are used in entertainment; for example, in outdoor shows such as the nightly IllumiNations show at Walt Disney World's EPCOT Center. Laser pointers are used by the general public; sometimes they will be accidentally or deliberately aimed at or near aircraft. (Of course, no unauthorized person should deliberately aim any type of laser at or near an aircraft.)
Lasers are even used, or proposed for use, with aircraft. Pilots straying into unauthorized airspace over Washington, D.C. can be warned to turn back by shining eye-safe low-power red and green lasers at them. At least one system has been tested that would use lasers on final approach to help line up the pilot on the proper guideslope. NASA has tested a Helicopter Airborne Laser Positioning System.
Because of these varied uses, it is not practical to ban lasers from airspace. This would unduly restrict legitimate uses, it would not prevent accidental illumination incidents, and it would not stop someone who deliberately, out of malice or ignorance, targeted aircraft. For this reason, practical laser/aviation safety is based on informed users and informed pilots.
Primary hazards of lasers and bright lights
There are some subjects which laser/aviation safety experts agree pose no real hazard. These include passenger exposure to laser light, pilot distraction during cruising or other non-critical phases of flight, and laser damage to the aircraft.
The main concerns of safety experts are almost exclusively focused on laser and bright light effects on pilots, especially when they are in a critical phase of flight: takeoff, approach, landing, and emergency maneuvers.
There are four primary areas of concern. The first three are "visual effects" that temporarily distract or block pilots' vision. (For lasers, these effects are only of concern when the laser emits visible light.)
(Note: The photos at right flash because most incidents are of flashes and not of steady illumination. In accidental illuminations there may be just one or a few flashes. Even in deliberate illuminations, it is hard to hand-hold a laser on a moving target, so there will be a series of longer flashes. With helicopters at close range, it is possible to have a more-or-less continuous light.)
The three visual effects above are the primary concern for aviation experts. This is because they could happen with lower-powered lasers that are commonly available. The fourth concern, eye damage, is much less likely. It would take specialized equipment not readily available to the general public.
It is extremely unlikely that any of the four elements above would cause loss of the aircraft, especially if the pilots react properly and work as a team.
Analyzing the hazard
The exact hazard in a specific situation depends on a number of factors.
Laser/bright light factors
Accidental vs. deliberate exposure
Laser users must take appropriate precautions to avoid accidents. (Some steps are outlined below in the section "Reducing the hazard".) In most cases, an accidental exposure is likely to be one or a few brief flashes, as the aircraft moves through a stationary beam, or as a hand-held beam sweeps over the cockpit.
There have been cases of deliberate intent, where someone through ignorance or malice deliberately aimed a laser at an aircraft. However, it is not easy to hand-hold a laser on a relatively distant target. It is even harder to hand-hold a laser on a moving target. As a result, a deliberate exposure is usually not a constant dazzling light but is more likely to be a series of longer flashes, as the perpetrator tries to keep the beam on the aircraft.
Whether an accidental or deliberate exposure, any pilot seeing a flash should avoid looking in the direction of the light, since it may be quickly followed by additional flashes.
Example laser safety calculations
The graphic at right shows many important laser/aviation safety concepts. For example, it shows that the areas of most concern -- eye damage, flash blindness and glare -- occur relatively close to the aircraft. The distraction risk covers the longest hazard distance, but fortunately also presents the least concern. The photos in the graphic also give an idea of what the visual effect looks like to the pilot, at various distances.
Note that while the distances given are exact ("52 feet", "262 feet"), the laser's brightness is in fact falling off slowly. It is not as if at 51 feet the laser is an eye hazard and at 53 feet it is eye safe. Effects diminish continuously with increasing distance.
Also, the weaker effects are part of any stronger effect. Even if a laser does not cause eye damage at 25 feet, it can still cause flash blindness, glare and a distraction.
For any given laser, the relative distances shown here may change. For example, an invisible (infrared) laser can be an eye hazard for hundreds of feet, but presents no flash blindness, glare or distraction hazard. Because of this, each laser must be analyzed individually.
To give another example, here are calculations of a more powerful laser -- the type that might be used in an outdoor laser show. A 6-watt green (532 nm) laser with a 1.1 milliradian beam divergence is an eye hazard to about 1,600 feet (488 meters), can cause flash blindness to about 8,200 feet (1.5 mi/2.5 km), causes veiling glare to about 36,800 feet (7 mi/11.2 km), and is a distraction to about 368,000 feet (70 mi/112 km).
Reducing the hazard
Successful laser/aviation safety requires effort both on the ground, from laser and bright light sources, and in the air, from pilots. While ground-based laser hazards should be reduced as much as possible, there is always the chance of accidental (or deliberate) exposure. In such a case, the pilot should not panic, should avoid looking at or near the beam, and should continue to "fly the plane".
Laser/bright light hazard reduction
Regulatory and other hazard reductions
Pilot/aircrew hazard reduction
The following three pilot/aircrew recommendations are under study. They may work in theory and in some situations such as military operations. However, they may not be suitable, practical or recommended for widespread use.
Regulation and control
In the United States, laser airspace guidelines can be found in Federal Aviation Administration Order 7400.2 (Revision "F" as of August 2006), Part 6, Chapter 29, "Outdoor Laser Operations". Bright light airspace guidelines are in Chapter 30, "High Intensity Light Operations".
In the United Kingdom, CAP 736 is the "Guide for the Operation of Lasers, Searchlights and Fireworks in United Kingdom Airspace." 
For all laser users, the ANSI Z136.6 document gives guidance for the safe use of outdoor lasers.  While this document is copyrighted by ANSI and is relatively costly, a flavor of its recommendations can be seen in NASA's Use Policy for Outdoor Lasers. 
The U.S. FAA has established airspace zones around airports:
In the UK, restrictions are in place in a zone that includes a circle 3 NM (5.5 km) in radius around an aerodrome (airport) plus extensions off each end of each runway. The runway zones are rectangles 20 NM (37 km) in total length and 1000 meters (3280 feet) wide, centered about each runway.
In the U.S., those persons operating outdoor lasers are requested to file reports at least 30 days in advance, detailing their laser power(s). They must reference their operation location with respect to local airports and describe the laser power emitted within the Sensitive, Critical and Laser Free zones. Note that it is possible to use lasers whose output exceeds the limits of these zones, if other control measures are in place. For example, spotters could be used to watch for aircraft, and turn off the laser if a potential conflict is sighted. (This raises separate issues about the number, training and effectiveness of the spotters; the FAA must be satisfied that these issues are answered for the particular operation.)
FAA Advisory Circular 70-1 "Outdoor Laser Operations" contains two forms plus instructions. One form is a "Notice of Proposed Laser Operations", the other is a "Laser Configuration Worksheet" which is filled out for each laser or each different laser configuration. The FAA will review the report, and will either send a letter of objection or will send a letter of non-objection. Note that the FAA does not "approve" or "disapprove" as this implies a higher level of regulatory authority.
(U.S. laser light show users have a slightly different regulatory process. Any use of lasers in a show or display requires pre-approval from the FDA Center for Devices and Radiological Health. This is required both for the laser equipment, and separately for the show itself (site, audience configuration, beam effects, etc.). As part of the CDRH's show approval ("variance") process, the CDRH will require a letter of non-objection from the FAA. Without this, the show cannot legally proceed.)
In the U.S., laser activity in a given area is communicated to pilots before their flight via a NOTAM. Pilots exposed to a laser or bright light during flight should follow Advisory Circular 70-2 "Reporting of Laser Illumination of Aircraft".
UK laser operators should report outdoor laser, searchlight or firework operations at least 28 days in advance, using the Notification Form found in annex A of the CAP 736 document. 
Regulatory and standards development
A key group inside the U.S. working on laser/aviation safety is the SAE G10-T, Flight Deck Laser Hazards Safety Committee. It consists of laser safety experts and researchers, pilots and other interested parties representing military, commercial and private aviation, and laser users. Their recommendations have formed the basis of the FAA laser and bright light regulations and forms, as well as standards adopted in other countries and by the ICAO.
The ANSI Z136.6 standard is the "American National Standard for Safe Use of Lasers Outdoors". The Z136.6 committee has worked closely with SAE G10-T and others, to develop recommended safety procedures for outdoor laser use.
Until the early 1990s, laser and bright light aviation incidents were sporadic. In the U.S., NASA's Aviation Safety Reporting System showed only one or two incidents per year. The SAE G10-T began meeting around 1993 as the number of incidents grew. Almost all of the incidents were known or suspected to be due to outdoor laser displays. Almost all of the concern was over potential eye damage; at the time visual effects were felt to be a minor consequence.
In late 1995, a number of illumination incidents occurred in Las Vegas due to new outdoor laser displays. Although the displays had been approved by the FDA as eye-safe for their airport proximity, no one had realized that the glare/distraction hazard would adversely affect pilots. In December 1995 the FDA issued an emergency order shutting down the Las Vegas shows.
Within the SAE G10-T, there was some consideration about cutting back or banning laser shows. However, it became apparent that there were a large number of non-entertainment laser users as well. The focus shifted to control of known laser users, whether shows or industry/research. New policies and procedures were developed, such as the FAA 7200 Chapter 29, and Advisory Circular 70-1. Although incidents continued to occur (from January 1996 to July 1999, the FAA's Western-Pacific Region identified more than 150 incidents in which low-flying aircraft were illuminated by lasers), the situation seemed under control.
Then in late 2004 and early 2005, came a significant increase in reported incidents linked to laser pointers. The wave of incidents may have been triggered in part by "copycats" who read press accounts of laser pointer incidents. In one case, David Banach of New Jersey was charged under federal Patriot Act anti-terrorism laws, after he allegedly shone a laser pointer at aircraft. Because there was no federal law specifically banning deliberate laser illumination of aircraft, Congressman Ric Keller introduced H.R. 1400, the "Securing Airplane Cockpits Against Lasers Act of 2005."
As of September 2006, the wave of laser pointer incidents has died down, and H.R. 1400 is awaiting final passage.
"Laser Pointers: Their Potential Affects[sic] on Vision and Aviation Safety", Van B. Nakagawara, DOT/FAA/AM-01/7, April 2001.
August 2003 FAA study: "The Effects of Laser Illumination on Operational and Visual Performance of Pilots Conducting Terminal Operations", DOT/FAA/AM-03/12.
June 2004 FAA follow-up study: "The Effects of Laser Illumination on Operational and Visual Performance of Pilots During Final Approach", DOT/FAA/AM-04/9. 
Congressional Research Service Report for Congress RS22033, "Lasers Aimed at Aircraft Cockpits: Background and Possible Options To Address the Threat to Aviation Safety and Security" by Bart Elias.
NASA's "Use Policy for Outdoor Lasers" 
A sampling of NASA ASRS laser incident reports can be done by searching for the term "laser".
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Lasers_and_aviation_safety". A list of authors is available in Wikipedia.|