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.
Aviation hazards from bright light can be minimized or eliminated in two primary 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.
Pointing a laser at an aircraft can be hazardous to pilots and has resulted in arrests, trials and jail sentences. It also results in calls to license or ban laser pointers. Some jurisdictions such as New South Wales have restricted laser pointers as a result of multiple incidents.
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.
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. The FAA has tested laser-projected lines on airport runways, to increase visibility of "hold short" markings.
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
(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 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.)
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
The U.S. FAA has studied some of these factors . They conducted research using pilots in flight simulators to determine the effects of laser exposure on pilot performance; results were released in August 2003 and June 2004.
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. Note that no one should ever deliberately aim a laser at an aircraft. It can result in pilot distraction, and may well result in searches by authorities to find the source. There have been a number of cases reported where laser pointer users were arrested and tried; a few have even gone to jail. Such incidents also can lead to calls to license or ban laser pointers.
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
There are a number of ways that laser users, regulators and pilots reduce the potential hazard from outdoor laser use. These measures include:
Police have begun using helicopters to patrol and seek out people using lasers to disrupt aviation.
User hazard reduction measures
Regulatory hazard reduction measures
Pilot/aircrew hazard reduction measures
Active hazard reduction (proposed measures)
Some measures have been proposed to protect aircrews including goggles and windscreen filters. These may work in theory (especially against known wavelengths) and may be useful in some situations such as military operations. However, these measures may not be suitable, practical or recommended for widespread civil air operations.
Regulation and control
In the United States, laser airspace guidelines can be found in Federal Aviation Administration Order JO 7400.2 (Revision "G" as of April 2008), Procedures for Handling Airspace Matters, 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. These protect the area around airports and other sensitive airspace from the hazards of safe-but-too-bright visible laser light exposure:
For non-visible lasers (infrared and ultraviolet), the irradiance at the aircraft must be eye-safe -- below the Maximum Permissible Exposure level for that wavelength. For pulsed visible lasers, the irradiance at the aircraft must be both eye-safe and must be at or below any applicable FAA laser zone.
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 with the FAA 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. The language is important; the FAA does not "approve" or "disapprove" as this implies a higher level of regulatory authority which the FAA does not have.
If the laser use is for a show or display in the U.S., there is a more stringent regulatory process. In the U.S., 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 laser 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 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 G-10T, Laser Safety Hazards Subcommittee. 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 G-10T 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 G-10T subcommittee 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 G-10T subcommittee, 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.
Responding to the incidents, the Congressional Research Service issued a study on the laser "threat to aviation safety and security." 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." The bill was passed by the U.S. House and Senate, but did not go to conference and thus did not become law.In 2007, Keller re-introduced the bill as H.R. 1615. It passed the House in May 2007 but as of April 2008 has not been voted on in the Senate.
On March 28 2008, a "coordinated attack" took place using four green laser pointers aimed at six aircraft landing at the Sydney (New South Wales) Australia airport. . As a result of this attack plus others, a law was proposed in mid-April 2008 in NSW to ban possession of handheld lasers, even "harmless classroom pointers". The Australian state of Victoria has reportedly had a similar ban since 1998, but press reports state that it is easy to buy lasers without a permit.
On February 22 2009, a dozen planes were targeted with green laser beams at Seattle-Tacoma International Airport.An FAA spokeswoman said there were 148 laser attacks on aircraft in the U.S. from January 1 2009 to February 23 2009.
Published - July 2009
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