Elevated Runway Edge Lights By Inversion

 Elevated Runway Edge Lights By Inversion

By OffRoadPilots

When operating in the arctic, subarctic, mountainous areas, or sparsely settled areas, airlines and airports needs a safety management system (SMS) that includes optical illusion by inversion, optical illusion by sun angle, and optical illusion known as the black-hole effect. An optical illusion is real and the same as a mirage. A mirage is a real optical phenomenon that can be captured on camera since light rays are actually refracted form the false image. A mirage occurs when there is a temperature inversion. An inversion is when air at higher altitudes is warmer than the air below. When the air below the line of sight is colder than the air above it and when passing through the temperature inversion, the light rays are bent down, and so the image appears above the true object. Mirages tend to be stable, as cold air has no tendency to move up and warm air has no tendency to move down. Mirages make objects below the horizon, or outside of a normal line of sight, visible at the horizon. A sun angle optical illusion is when color of rocks in mountain combined with sun angle make a large mountain range impossible to see.

The black hole illusion is a nighttime illusion that occurring when only the runway is visible to pilots without surrounding ground lights. With this illusion there is a tendency, or a trap, for pilots to estimate an incorrect required descent angle and causing the approach to be lower than required for the runway. Another illusion caused by the black hole conditions on dark nights with no moon or starlight, or without a visible horizon, triggers pilots to believe that are on approach slope since they have a steady view of the runway in their windshield, causing them to fly a longer and shallower approaches than needed to clear obstacles. Unless a pilot has up to date knowledge and is intimately familiar with

the airfield, thorough pre- approach study and preparation is required to mitigate the black hole hazard. Today, there are online tools and maps available for pilots to become familiar with approaches and departures at most aerodromes and certified airports.

The same black hole illusion occurs during takeoff when the acceleration g-force is applied to the pilot and their cllimbout angle appears as a steeper than normal. On a dark night, without moonlight or starlight, and without a view of the horizon due to the black hole illusion, a tendency is to reduce aircraft pitch and departure angle may be lower than required to clear obstacles or could even be a negative angle. A contributing factor to a King Air accident in 2007 after a missed approach was caused by the illusion of a climb, when the aircraft was descending.

It is a regulatory requirement for an airport operator to identify in their airport emergency plan potential emergencies within a critical rescue and fire-fighting access area that extends 1000 m beyond the ends of a runway and 150 m at 90° outwards from the centreline of the runway, including any part of that area outside the airport boundaries. It is also a regulatory requirement for an airport operator to identify emergencies that can reasonably be expected to occur at the airport or in its vicinity and that could be a threat to the safety of persons or to the operation of the airport. Optical illusions are real and therefore reasonable to be expected to occur for arrivals and departures. The question to answer is how far away from the airport, beyond the 1000 m distance and 150 m from centerline mark an airport operator assess to be reasonable to initiate an emergency response. In 2017 an aircraft crashed and came to a rest beyond a point 150 m from the extended centerline. Since the airport was operating with a safety management system it was reasonable expect that they would initiate their emergency response plan at that time.

It is also reasonable to expect that airports identify their outer identification surface as their outer limits of primary responsibility and with a responsibility to assist upon request beyond that distance. In 2011 an airplane crashed about 3000 m from an airport and 280 m from the extended centerline, and the airport responded to the accident. In another accident in 2011 an aircraft crashed 1500 m from the centerline and the airport activated their response. A safety management system must be tailored specifically to each airport and that airport emergency plan definitions of distance in its vicinity will vary. Since the regulations are not broad enough to cover every detail of airline or airport operations, their SMS must include a practical application of their plan to address hazards and operational tasks. A rule of thumb for an effective SMS is if the regulations does not require it, this now becomes the very same reason why it is incumbent on airlines or airports to do it.

There are several non-certified aerodromes and remote airports operating without vertical or lateral guidance to their runways. At night, a lighted object, e.g. tower, may appear to be just a few miles ahead of an aircraft in cruise flight, while the actual distance could be 100 miles. When pilots are relying on visual clues as their vertical and lateral guidance, there are times when their aircraft has drifted away from an extended centerline or is low or high on approach. In 1993 a twin engine aircraft approach to an airport at night had the runway in sight at 1200 feet, with a flight visibility near minima. On final approach the crew descended blow a virtual glidepath and aircraft crashed in a hilly and snowy terrain located 5 km short of runway 26. Other examples are major carries approaching low on approach to international airports or lined up on the taxiway for landing. Optical illusions could happen at any airport, but there is a higher probability that an aircraft will be low, high, or drifted away from centerline on approach to airports without vertical and lateral guidance systems.

A guidance approach system installed an several airports is the Precision Approach Path Indicator (PAPI), which is a vertical guidance system for aircraft on final approach. Flying the glidepath of a PAPI keeps aircraft within the obstacle protected surface as long as the airport operator is applying their safety management system processes to monitor for unknown, or new obstacles. An optical illusion created by a PAPI system is when there is frost on the PAPI lenses, and their lights are deflected.

A rule of thumb when flying approaches without PAPI installed is to be 1000 feet above the runway at 3 NM and to maintain runway edge lights visible in a fixed view. The illusion without guidance is that an aircraft is too high when the actual altitude may be below the safe approach angle. In Canada, airports standards are only applicable to airports serving scheduled service for the transport of passengers. An aerodrome serving large airlines, with hundreds of passengers onboard, is not required to comply with the Canadian Aviation Regulations standards compliance. This is a flaw in the regulatory system when the method of how tickets are purchased determines monitoring of safety at destination or departure airports. If the same principle was to be applied to highway travel, speed limits would only be applicable to national bus carriers with paying passengers.

Requirements for a certified airport to install PAPI is that they conduct a risk assessment within their SMS to establish the need for a PAPI. One airport determined by their risk assessment that a PAPI was not to be required since there were no data supporting low, high, or off-centre approaches to their airport. When such data is not collected, risk analyses become simple, but do not paint a true picture of their operations. The absence of incidents is not an indication of a healthy safety management system, or a healthy operational environment. Most times things go right because human factors come with built-in resilience, or the ability to correct errors, or bounce back after an occurrence. An occurrence is not just that an aircraft crash, but also when an approach is flown below the slope of a standard approach path. When occurrences go unreported it makes it a simple to fill in the SMS compliance checkboxes, but optical illusions are occurrences to be reported.

On a dark October night an aircraft was on approach to an airport in the Arctic. That night it was a temperature inversion causing an illusion that runway edge lights were raised well above ground level. When runway lights were elevated, they could be seen from a farther distance and appear to be closer. This night the runway lights were raised by optical illusion to a heigh where they could be seen above a mountain range that normally would obscure the lights at this distance. Since the lights were visible, the position of the aircraft was determined to be inside the mountain range and safe of obstructions. However, within a few minutes the airplane crashed, since the viewed runway edge lights was an illusion, and they were still on the backside of the mountain.

In addition to natural made optical illusions, there is a man-made optical illusion that, at night, when an aircraft is parked on the runway in the same direction as an approaching aircraft, makes the park runway aircraft invisible.

Optical illusions are real. Only by knowing of their existence, learning about the nature of this phenomena, and verifying position by aircraft instruments can it be determined that they are illusions. When flying on visual clues illusions are real, aircraft may be invisible and runway edge lights may be elevated several feet above their actual ground level location.

OffRoadPilots