Last Line of Defense - The Pilot!
By Capt. C.W. "Bill" Connor, Ph.D. (Delta, Ret.)
Air Line Pilot, April 2005, p.21
Numerous laser illuminations of flightcrew member cockpits at locations across the United States have recently come to the attention of the news media and regulatory agencies, including the FBI and the Department of Homeland Security.
Previously, accidental laser illuminations have occurred as a result of commercial entertainment groups and hotels using lasers for advertising. Once the FAA, the Food and Drug Administration, and the Center for Devices and Radiological Health became aware of possible safety hazards of flash blinding flightcrew members during critical phases of flight, the agencies revisited and upgraded laser regulations to handle current increasingly powerful and less expensive laser technologies.
Recent laser illuminations seem to be intentional, originating from individuals who are tracking the aircraft. Thus, these laser illuminations are more capable of interfering with the flight crew's ability to safely operate during critical phases of flight.
The terminal area represents the highest visual workload period for flightcrew members and air traffic controllers. Other concerns are associated with laser illuminations within the airspace used by low-flying aircraft, particularly helicopters where no structured airways or climb corridors exist.
The primary issues to address are operational considerations and research into ways for pilots to deal with laser technologies. In addition, flightcrew member procedural protocols for coping with laser illuminations should be developed with a LOFT simulation program to help flightcrew members recognize and neutralize laser interruptions of their vision. Regulations to protect navigable airspace and to standardize reporting procedures should minimize the aeromedical problems.
On January 12, U.S. Transportation Secretary Norman Mineta visited the FAA's Mike Monroney Aeronautical Center in Oklahoma City, to release FAA Advisory Circular 70-2, Reporting of Laser Illumination of Aircraft. During the visit, he saw a laser illumination demonstration in the simulator and discussed the procedures and reporting guidelines with the chief scientist for flight simulation systems, Dr. Archie Dillard. Mineta said, "Any laser illuminations of aircraft cockpits are a criminal act regardless of the source or intention."
A Laser Illumination Incidents Update, informing the aviation industry of the current status and potential threats to flight safety, was held during a January meeting of the Society of Automotive Engineers' Aerospace Behavioral Engineering Technology group, the SAE G-10 Committee. As a result of this meeting, a new SAE G-10 Subcommittee was formed to develop Aerospace Recommended Practice 5598, Operational Laser Visual Interference Guidelines, which will address the operational safety and human factors aspects of unauthorized laser illumination events in navigable airspace. The areas of interest include operational procedures, training, and flightcrew human factors. In addition, recommendations will be developed for procedures and protocols for flightcrew members to best neutralize laser illumination incidents during critical phases of flight and to reduce the risks to the lowest level possible with existing technologies.
The Operational Laser Visual Interference Guidelines Subcommittee, met in early March. Representatives from the U.S. Air Force, the FAA, Northrop-Grumman, Rockwell Collins, and the SAE G-10 Operational Laser Committee, incorporated the two ACs into the operational procedures guidelines. The program will use the FAA's Flight Simulations Systems Facility in Oklahoma City and the Brooks Air Force Research Lab in San Antonio, Tex.
In October 1995, the pilots of a Southwest B-737 departing Las Vegas experienced a laser beam illumination at 500 feet AGL. The laser beam source was reported to have originated from one of the hotels located near the airport, and the beam entered the cockpit through the copilot's window. The copilot reported loss of vision in his right eye for about 15 minutes. The captain said that if the laser had passed through the front windshield illuminating both pilots, he believed that they would have lost control of the aircraft. The laser involved in this event was a high-powered device intended to be visible for many miles.
This incident was just one of a series of 51 laser beam illuminations that pilots of large and express jets and local helicopter operators reported at Las Vegas airport during an 18-month period. After ALPA prompting, the FDA and the FAA both agreed that existing regulations and guidelines were not adequate for the current usage of laser beam technologies in navigable airspace. As SAE G-10 Committee chairman, I contacted the FAA Administrator to offer the Committee's help in revising FAA Order 7400.2. I formed a team that developed a program for the FAA. The team included Dr. Archie Dillard, FAA National Resource Specialist; Van B. Nakagawara, O.D., FAA Aeromedical; Dale Smith, FDA/CDRH; Lt. Col. Leon McLin, O.D., Air Force Research Laboratory; Lt. Col. Ken Burke, USAF Safety Center; Robert Aldrich, U.S. Naval Weapons Systems; and Wesley Marshall and Dr. David Sliney, Aberdeen Proving Ground.
In 1995, the FAA revised Order 7400.2, Part 6, Miscellaneous Procedures: Outdoor Laser Operations, which was originally based on the FDA's "Performance Standards for Light-Emitting Products."
The Center for Devices and Radiological Health regulates the product performance for the FDA. The FDA, when it receives an application for laser activities, evaluates it to ascertain if the device will be operating near airports. If so, the FDA contacts the FAA to begin an aeronautical study to determine if there are any objections.
The revised FAA Order 7400.2 established new guidelines for flight-safe exposure limits (FSELs) in specific zones of navigable airspace associated with airport terminal operations, in addition to the preexisting maximum permissible exposure that limited exposure in the normal flight zone (NFZ). Based on consultations with laser and aviation experts, scientific research, and historical safety data, 100 microwatts per centimeter squared (µW/cm2) was identified as the level of exposure at which significant flash blindness and afterimages could interfere with a pilot's visual performance. Similarly, 5µW/cm2 was determined to be the level at which significant glare problems can occur.
When a laser is to be operated outdoors in the vicinity of an airport or air traffic corridor, the FAA may be required to conduct an aeronautical study to identify the zones of airspace around an airport or airway that must be protected by the application of appropriate FSELs. The new zones and FSELs are
o Laser-free zones = 50 nanowatts per centimeter square (nW/ cm2)
o Critical flight zone = 5 µW/ cm2
o Sensitive flight zone = 100 µW/ cm2
o Normal flight zone = 2.5 mW/ cm2
The ICAO Laser Safety Standards Document used the SAE Aerospace Standard 4970 as a core reference document for the ICAO standard. The above restrictions were used as guidelines for the Olympics in Australia and are the standard for ICAO's 184 representative countries.
In 2000, the American National Standard for the Safe Use of Lasers Outdoors (ANSI) Z136.6, chaired by Wesley Marshall, was published and complemented FAA Order 7400.2. This FAA order and Z136.6 standard recommend the implementation of flight hazard zones (see Figure 1). NOTAMS should be issued to alert flightcrew members of any laser activity within 20 miles of an airport.
Pilot visual systems
The eye is particularly vulnerable when focused at a distant object and a direct or reflected laser beam enters the pupil. The combined optical gain of the cornea and crystalline lens will amplify the laser energy by a factor of as much as 100,000 times when it reaches the retina. The use of magnifying optical devices may further increase retinal irradiance. The visible portion of the electromagnetic spectrum is between 400-780 nanometers.
Dynamic scan-pattern chunking
In flight, when flight instruments are the only source of information, flightcrew members must direct their visual attention to interpret and process information from them. This requires a visual-scan technique that uses frequent scans of the instruments to obtain bits of information from the control and performance instruments. The highly proficient flightcrew member assembles the associated bits into related chunks of information that represent dynamic spatial patterns. Control and performance instruments continuously update these scan patterns through a closed-loop feedback. This procedure is commonly referred to as "dynamic scan-pattern chunking." Laser illumination may cancel a flightcrew member's capability to extract any visual information from flightdeck instruments for an unknown period of time.
Flightcrew members must recreate the outside world with flight instruments to form dynamic linear and angular patterns. Images from the outside world are initially upside down and backward when reaching the retina. Visual inputs balance the body through the brain's comparison of visual images transmitted from the retina to the brain's preexisting mental model. This mental model is continuously updated with reference to the outside world for comparison and processing. In fact, the visual system is a pilot's primary control of ability to recognize spatial orientation as evidenced by the fact that humans can fly without a functioning inner ear or balancing system. On the contrary, any visual impairment or interruption will cause the crewmember to revert to less reliable sensory organs, such as the inner ear and sensory neurons in the extremities, the so-called "seat-of-the-pants flying."
Temporary vision impairment can last for several minutes depending upon the laser's power, beam divergence, distance from the power source, and duration of exposure.
Understanding the general principles upon which the human balance system operates is critical for flightcrew members who operate in IMC, or have temporary vision impairment caused by laser illuminations. Loss of outside visual reference with the horizon may cause the balance system to send conflicting information resulting in disorientation and, potentially, vertigo (sensory cross-coupling). This failure of the inner-ear system to provide accurate orientation information to the brain is much more likely to occur when the motion exceeds naturally occurring bounds (e.g., during acceleration, deceleration, and turning involved with the critical phases of flight.)
Flightcrew members receive almost 90 to 95 percent of their information visually to develop patterns, associations, and trend vector analysis options. Loss of visual reference can create startle, distraction, disruption, disorientation, and in extreme cases, incapacitation.
The illuminated Southwest pilot (mentioned earlier), while performing a climbing steady-state turn on departure, stated that he thought another aircraft had come into his airspace with its landing lights on. He was instantaneously flash blinded; the flash blindness lasted for 15 minutes. This is an example of an operational startle-level 3&4, including disruption and disorientation. This condition occurs when the pilot has lost his visual reference with the outside world and must rely upon inner-ear and seat-of-the-pants feedback, which is highly unreliable. Temporary loss of vision can cause spatial disorientation and loss of situational awareness because of the pilot's inability to visually sense the attitude, altitude, or heading of the aircraft.
Two areas in which outdoor laser operations potentially pose a safety concern to flightcrew members are (1) a condition in which maximum permissible exposure (MPE) is exceeded and physical injury to the illuminated eye can occur, and (2) a situation in which MPE is not exceeded but a potential for functional impairment still exists.
Visual functional impairment conditions
o Flash blindness is an effect that persists for a period of time while the eye recovers from an exposure to a bright light source. The ability of any given light source to induce flash blindness is directly related to the brightness of the source and the level of dark adaptation in the target eye at the time of the exposure.
o Afterimages refer to perceptions, so-called aftereffects, that persist after illumination with a bright light source and are described as light, dark, or colored spots following exposure. Such afterimages are essentially a type of flash blindness, although afterimage effects may last for more prolonged periods of time-well beyond the time available for recovery to perform visual tasks required while in the cockpit. Like flash blindness, visual restoration from afterimages is more prolonged in older individuals. The intensity, density, and duration are in direct proportion to the level of the instigating light sources (see Figure 2, page 23).
o Glare and dazzle, two terms often used interchangeably, refer to temporary disruptions in visual acquisition without biological damage. Virtually any light source can cause glare, which is particularly disruptive when an eye is fully adapted to night. However, any glare source in the cockpit is undesirable. Glare effects are diminished as the position of gaze shifts away from the light source. The length of time during which glare is in effect is not only a function of how long the target is viewed, but also the overall adaptation state and size of the eye's pupil.
Glare can be further broken down into discomfort glare and disability glare.
Discomfort glare refers to glare of illumination so bright that it forces the viewer to turn away. Discomfort glare tends to be exacerbated when the overall ambient illumination is low. Disability glare refers to inability to see a target because of the light source. In addition, veiling glare represents the ability of a light source to impede visualization of structures beyond the actual size of the light source.
Permanent eye injuries of illuminated flightcrew members are improbable. However, certain flight hazards are associated with temporary vision loss during critical phases of flight-takeoff and landing and, especially, standard instrument departures that require climbing steady-state turns. Temporary vision loss is associated with
o flash blindness,
o afterimage, and
The visual effects from glare increase with age, which undoubtedly represents a function of age-related changes in the optical capability in the older eye, particularly the lens. In general, a laser light source is a very bright light that can be an extremely effective disability glare source.
Any intervening ocular interfaces, such as windscreens, canopies, and eyeglasses that scatter incident light, can increase disability from glare from an external light source. As more scatter occurs, disability glare increases.
Physiological ocular symptoms include momentary loss of vision, light sensitivity, tearing, and glare. Glare can cause a reduction or total loss of vision, but the effect lasts only as long as the light is present in the observer's field of view.
Protective eyewear (notch filters) can provide excellent protection against 532-nanometer wavelengths. However, notch filters are not yet recommended for airline use because they are capable of protecting vision against only specific wavelengths. The notch filters also limit the wearer's ability to read instruments, must be carefully adjusted, and have other limitations.
Research is being done to develop eyewear that could be useful on airline flight decks.
Unfortunately, windscreen filters are also impractical and expensive.
Last line of defense
Because no practical filters are available yet, flightcrew members are the last line of defense against laser illuminations.
Pilots are the final link in the safety chain that can prevent an incident from becoming an accident. They must have operational laser procedures and protocols to neutralize the effects of startle and flash blindness during critical phases of flight.
ALPA has adopted the procedures and protocols we developed and has published them in ALPA Operations Bulletin 2005-01, Laser Illumination Hazards. To view that Bulletin, go to the Preflight area of crewroom.alpa.org, then click on Operations Bulletins.
|Capt. Connor is chairman of the SAE G-10 Executive Board and the SAE G-10T Laser Hazards Subcommittee, the former ALPA Laser Safety chairman, the U.S. Representative to ICAO on Laser Safety Standards, and Associate Fellow in the Society of Experimental Test Pilots. He holds numerous degrees including PhDs in behavioral psychology and in aeronautical science. He has received several awards for his work with lasers, including citations from ALPA's President and the FAA Administrator.|