What is Being Done to Protect Pilots and Aviation Safety

by Van B. Nakagawara, OD

and Ronald W. Montgomery

When we think about lasers (i.e., Light Amplification by Stimulated Emission of Radiation), we often remember old television heroes, like Buck Rogers and Flash Gordon. More recently, science fiction movies, such as the "Star Wars" and "Star Trek" series, have reinforced those stereotypes. In reality, lasers are sophisticated instruments that emit light beams that are so powerful they can cut through metal or so delicate they can perform microscopic surgery.

Outdoor laser light displays have become increasingly popular over the past few years. In theme parks, such as Epcot Center and Disneyland, and in areas where legalized gambling have resulted in large, elaborate casinos, such as in Las Vegas, NV, and Biloxi, MS, laser light shows have flourished in attempts to entertain and attract customers. More recently, special events, such as the NCAA Final Four Basketball Championships in Seattle, WA, have used laser light displays to advertise and glamorize these attractions.

The penetration of laser light into navigable airspace has resulted in temporary visual incapacitation of pilots. Laser light illumination can be similar to being exposed to a camera's flash bulb without warning. Besides momentary shock and surprise, effects can include glare, afterimage, and flashblindness. Glare is the dazzling sensation of a bright light that produces discomfort or interferes with optimal vision. Afterimage is a persistent sensation or image perceived after the causal physical stimulus has been removed. Flashblindness is visual loss following exposure to a high intensity flash of light. Afterimages and flashblindness can last for several minutes! The illumination level for these effects can only be estimated, as individual differences to non-laser light exposure are well documented in clinical practice. Additionally, there is little data on how startle affects the pilot, and the intensity of the illumination for this may be quite low.

Documented incidents of laser light affecting pilots, include:

October 1995: A Southwest Airlines Captain, serving as a First Officer (FO), on a Boeing 737 departing McCarran Airport in Las Vegas, was struck in the right eye by a laser light at about 7000 feet. Unable to see or focus for well over two minutes, the FO was forced to turn over control of the aircraft to the Captain.

June 1994: A Flight Engineer on a US Air Force EC-130E was flashed by a laser light from a casino in Biloxi, Miss. The crewmember was momentarily blinded and could not read his instruments. Post-event symptoms resulted in the airman being put on temporary restriction from flight duty.

November 1993: A laser beam through the right side cockpit window strikes the right eye of the FO of a Southwest Airlines 747 departing Las Vegas. Both the Captain and FO were blinded for 5-10 seconds, and the FO had reduced night vision for 5-10 minutes. The FO later experienced a conjunctival irritation in the right eye.

June 1990: A pilot of a wide body aircraft on approach to Miami reports a green laser light flashed directly into his eyes blinding him for about 2 seconds, resulting in problems with focus and irritation for 2 minutes more. The beam was from a laser light show being performed at the edge of the downtown harbor area.

As the number of laser installations has increased (it is estimated that about 200 operators have licenses for laser shows), so has the number of reported laser strikes to aircraft. Over 50 laser-related encounters by flight crews have been reported to the McCarran control tower in Las Vegas since November 1993! A potentially serious condition exists when the laser flash wipes out the dark adaptive state of the pilot. Partial recovery of dark adaptation is normally achieved in 3 to 5 minutes, but full adaptation typically requires 40-45 minutes. During this period, the pilot would be visually compromised making night flight operations difficult or impossible. As a result, the Food & Drug Administration (FDA) recently established a moratorium on outdoor laser shows in the Las Vegas area, due to the number and severity of some reported incidents. Laser operators argue that their control measures are adequate to prevent exposure of aircraft at hazardous levels. The moratorium is under review.

The adverse effects of laser light exposure on the proper execution of critical flight operations have caught the attention of the aviation community. The Society of Automotive Engineers (SAE) G-10 (Aerospace Behavioral Engineering Technology) Committee has held several meetings to investigate this problem. The SAE G-10 Committee is working with the Federal Aviation Administration (FAA) and FDA investigating aviation issues, reviewing regulations and recommending changes to solve or minimize identified problems whenever possible. Laser hazard safety meetings have included representatives from the Airline Pilot's Association, the laser light show industry, FDA, American National Standards Institute (ANSI), US Air Force, FAA, and other technical experts.

Among other recommendations, the SAE G-10 Laser Hazards Safety Sub-committee is working with FAA, FDA, and other concerned groups to rewrite FAA Order 7400.2D, Chapter 34 (Outdoor Laser Demonstrations), which regulates outdoor laser demonstrations used for entertainment and promotional purposes. Currently, the operator/manufacturer must first apply for permission to project higher power lasers in navigable airspace from the FDA's Center for Devices and Radiological Health, and obtain what is known as a "variance." Both the FDA variance and FAA Order 7400.2D require the laser operator/manufacturer to notify the FAA of the planned laser demonstration. Upon notification, an aeronautical study is conducted by the FAA's Air Traffic Division in the region where the laser installation is being planned. The study determines the laser demonstration's potential effect on air traffic in the immediate area. Once the FAA and all FDA requirements are met, the operator/manufacturer is then permitted to project laser beams into navigable airspace in a controlled and responsible manner.

FAA Order 7400.2D is written in terms of the FDA's "Performance Standards for Light-Emitting Products," 21 CFR (Code of Federal Regulations) 1040. The FDA standard is based on the recommended Maximum Permissible Exposure (MPE) of 2.6 mW/cm2 for continuous wave lasers that establishes the Nominal Ocular Hazard Distance within which biological damage may occur. This MPE was established by the American National Standard for Safe Use of Lasers (ANSI Z-136.1-1993). However, this standard does not protect aircrew members from temporary visual incapacitation. The revised FAA Order 7400.2D identifies interim guidelines for new exposure limits to specific zones of navigable airspace around airports. These include the original MPE covering all uncontrolled airspace, and additional restrictive exposure limits covering "sensitive" and "critical" flight zones around airport runways. A "laser-free" flight zone is also specified for final approach and take-off corridors. The SAE G-10 Laser Safety Hazards Sub-committee has recommended that research be performed to ensure that the new interim guidelines are appropriate. In addition, the SAE considers communication between laser users, the FAA and pilots, as well as specialized technical training for these groups to be important steps in minimizing and/or eliminating this problem.

The FAA's Airspace and Obstructions Evaluation Branch (ATP-240) only required Notices To Airmen (NOTAMs) to be disseminated locally for new laser installations in the vicinity of an airport. In an effort to be proactive on this issue, laser NOTAMs are now issued through the National Flight Data Center and sent throughout the country. The texts of these NOTAMs include: information regarding the installation proximity to an airport or navigational aid, location of light source and direction of beam, and a special notice or warning concerning the possibility of flashblindness.

In summary, commercial laser light shows are used to attract and/or entertain customers at theme parks, casinos, and special events. Although exposures to these laser beams are normally at levels that would not cause biological damage, adverse effects to vision can occur and have been reported. Revision of the Federal regulations concerning the operation of laser shows in navigable airspace is currently in progress to ensure aviation safety is not compromised. Research to validate new guidelines for exposure to outdoor lasers of civilian and military pilot population is being planned.