Aircraft Warning Light
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Aviation obstruction lighting is used to enhance the visibility of structures or fixed obstacles which may conflict with the safe navigation of
aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...
. Obstruction lighting is commonly installed on
tower A tower is a tall Nonbuilding structure, structure, taller than it is wide, often by a significant factor. Towers are distinguished from guyed mast, masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting ...
s,
building A building or edifice is an enclosed Structure#Load-bearing, structure with a roof, walls and window, windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, a ...
s, and even
fence A fence is a structure that encloses an area, typically outdoors, and is usually constructed from posts that are connected by boards, wire, rails or net (textile), netting. A fence differs from a wall in not having a solid foundation along its ...
s located in areas where aircraft may be operating at low
altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...
s. In certain areas, some aviation regulators mandate the installation, operation, color, and/or status notification of obstruction lighting. For maximum visibility and collision-avoidance, these lighting systems commonly employ one or more high-intensity
strobe A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning ...
or
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
devices which can be seen by
pilots An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators because they are ...
from many miles away from the obstruction.


Lamp types

The lights generally come in two forms: * Red lamps that are either constantly illuminated or turn on and off slowly in a cycle of a few seconds. * White
xenon flash lamp A flashtube (flashlamp) produces an electrostatic discharge with an extremely intense, incoherent, full-spectrum white light for a very short time. A flashtube is a glass tube with an electrode at each end and is filled with a gas that, when tr ...
s. Both types were in use in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
until recently. New regulations stipulate the use of red lamps at nighttime only. Xenon flashers are gradually being phased out. In the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, there are several types of lights: *Obstruction lights (that are constantly illuminated) *Red beacons/red strobes *High-intensity white (strobe) lights *Medium-intensity white (strobe) lights Traditionally, red lamps (or beacons) use incandescent filament bulbs. To improve the otherwise quite short lifespan, they are made with a ruggedised design and are run below normal operating power (under-running). A recent development has been the use of arrays of high-power red
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
s in place of incandescent bulbs, which has only been possible since the development of LEDs of sufficient brightness. LED-based lamps have a significantly longer lifespan than incandescent bulbs, thus reducing maintenance costs and increasing reliability. Several manufacturers have also developed medium-intensity white strobes based on LED technology to replace xenon. Xenon flashers, whilst more visually impressive, tend to require frequent replacement and so have become a less favoured option. With the advent of LEDs, white strobes are still somewhat desired. It is common to find structures using white xenon flashers/white strobes during the daytime, and red lights at night. Red lights are commonly found to be used in urban areas, since it is easier for pilots to spot them from above. White strobes (that flash round the clock) (60 per minute for flashing marking "a unique signal that pilots should interpret as a warning that catenary wires are in the vicinity of the lights") may also be used in urban areas. It has been recommended that flashing white strobes should not be used in densely populated areas, as the lights usually merge with background lighting at nighttime, making it difficult for pilots to spot them, aggravating the hazard. In addition, residents near the lit structure will complain of light trespass. In rural areas, red beacons/strobes may also be used during nighttime. White strobes are (sometimes) preferred since they reduce the maintenance cost (i.e. no maintenance of painting, no red side lights) and there are no background lights that would blend with the strobes. There are a medium-intensity white strobe and a high-intensity white strobe. Medium-intensity white strobes are usually used on structures that are between . If a medium white strobe is used on a structure greater than , the structure ''must'' be painted. The common medium white strobe flashes 40 times per minute, at an intensity of 20,000
candela The candela (symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous to radi ...
s for daytime/twilight, and 2,000 candelas at nighttime. A high-intensity white strobe is used on structures that are taller than . These lights provide the highest visibility both day and night. Unlike a medium strobe, a high-intensity strobe does not provide 360° coverage; this requires the use of at least 3 high strobes at each level. On the other hand, it reduces maintenance costs (i.e. no painting). If the structure has an antenna at the top that is greater than 40 feet, a medium-intensity white strobe light must be placed above it rather than below. The common high white strobe flashes 40 times per minute, at an intensity of 270,000 candelas for daytime, 20,000 candelas at twilight, and 2,000 candelas at nighttime.Tower Lighting Guidelines
/ref> ''Dual'' lighting is a system in which a structure is equipped with white strobes for daytime use, and red lights for nighttime use. In urban areas, these are commonly preferred since it usually exempts a structure from painting requirements. One advantage to the dual system is that when the uppermost red lights fail, the lighting switches onto its backup lighting system, which uses the white strobes (at its night intensity) for nighttime. In the US and Canada, red incandescent beacons are slowly being withdrawn from service and being replaced with red strobes or red LEDs. For high-tension power lines, white strobes are equipped to flash 60 times per minute, using the same intensities as stated above. Unlike common white strobes, these strobes are specified not to flash simultaneously. The FAA-mandated flash pattern is middle, top, and bottom to provide "a unique signal that pilots should interpret as a warning that catenary wires are in the vicinity of the lights."


Transmission towers

On electric
transmission tower A transmission tower (also electricity pylon, hydro tower, or pylon) is a tall structure, usually a lattice tower made of steel that is used to support an overhead power line. In electrical grids, transmission towers carry high-voltage transmis ...
s, lights may be energized either from the
electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
surrounding the energized conductor, or the
magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
produced by current through the conductor. The first approach takes advantage of the high electric potential
gradient In vector calculus, the gradient of a scalar-valued differentiable function f of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p gives the direction and the rate of fastest increase. The g ...
around conductors. The second approach is based on Faraday's law of induction involving
magnetic flux In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the we ...
flowing through a circuit which energizes the warning light.


Use and positioning

These lights can generally be found attached to any tall structure such as broadcast masts and towers, water tanks located on high elevation, electricity pylons,
chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typical ...
s,
tall buildings A skyscraper is a tall continuously habitable building having multiple floors. Most modern sources define skyscrapers as being at least or in height, though there is no universally accepted definition, other than being very tall high-rise buil ...
, cranes and
wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...
s. Shorter structures that are located close to airports may also require lighting; an example of such is the south scoreboard at
Lambeau Field Lambeau Field () is an outdoor athletic stadium in the East North Central states, north central United States, located in Green Bay, Wisconsin. The home field of the Green Bay Packers of the National Football League (NFL), it opened in 1957 Green ...
in
Green Bay, Wisconsin Green Bay is a city in Brown County, Wisconsin, United States, and its county seat. It is located at the head of Green Bay (Lake Michigan), Green Bay (known locally as "the bay of Green Bay"), a sub-basin of Lake Michigan at the mouth of the F ...
built in 2013, which is the tallest structure in the general area of nearby
Austin Straubel International Airport Austin refers to: Common meanings * Austin, Texas, United States, a city * Austin (given name), a list of people and fictional characters * Austin (surname), a list of people and fictional characters * Austin Motor Company, a British car manufactu ...
. The International Civil Aviation Organization (
ICAO The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...
) sets standards, usually adopted worldwide, for the performance and characteristics of aviation warning lamps. Lights are usually arranged in clusters of two or more around the structure at specific heights on the tower. Frequently there will be a set at the top, and then one or more sets equally spaced down the structure. The
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
's Belmont mast has nine clusters of red lamps spaced equally along the full height of the mast.


Conductor marking lights

Conductor marking lights are sometimes used (in conjunction with
overhead wire marker Overhead wire markers are safety instruments applied to the overhead power lines marking transmission lines and ropeways along the flight path during the day.overhead power line An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy along large distances. It consists of one or more conductors (commonly multiples of three) suspended by towers or poles. ...
s more visible. Because power lines are often suspended between widely spaced masts, they present a particularly grave hazard to low flying aircraft (Red power line marker balls for preventing bird / plane collisions). A simple and cost-effective solution to this problem is installing marking lights directly on the wires, but there are significant technical difficulties to low-cost power extraction from a distribution system which carries high voltages and wide-range
AC current Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in w ...
. The ideal warning light must be able to power itself while clamped to a single wire of the line. Lights may be powered either from the
electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
surrounding the energized wire, or the
magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
produced by current through the wire. The first approach takes advantage of the high electric potential
gradient In vector calculus, the gradient of a scalar-valued differentiable function f of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p gives the direction and the rate of fastest increase. The g ...
between conductors, but a strong enough
capacitive coupling Capacitive coupling (electronics), coupling is the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit(s) node (circuits) , nodes, induced by the electric field. This coup ...
is requested to allow capacitive extraction of the power required from the warning light. This means that long conductors must be suspended parallel to the line using glass/ceramic isolators: in fact several meters of suspended conductor are generally required, total length being inversely proportional to the line voltage. The second approach is based on Faraday's law of induction involving
magnetic flux In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the we ...
flowing through a circuit which powers the warning light.


Non-standard aircraft warning lights

On some tall structures there are or were non-standard aircraft warning lights installed. * The mast of
Deutschlandsender Herzberg/Elster The Deutschlandsender III was a 500 kilowatt longwave transmitter, erected in 1938/39 near Herzberg (Elster), Herzberg, Province of Brandenburg, Brandenburg in Germany. Used for the ''Deutschlandsender'' radio broadcasts, the guyed mast reaching a ...
had no aircraft warning lamps installed. It was instead lit by skybeamers mounted on small masts near the tower. This method was chosen as the mast was a
mast radiator A mast radiator (or radiating tower) is a radio mast or tower in which the metal structure itself is energized and functions as an antenna. This design, first used widely in the 1930s, is commonly used for transmitting antennas operating at l ...
insulated against ground and for feeding the lamps on the mast otherwise special devices like Austin transformers would be required. *
Stuttgart TV Tower Fernsehturm Stuttgart () is a Radio masts and towers, telecommunications tower in Stuttgart, Germany. It was the first telecommunications tower in the world constructed from reinforced concrete, and it is the prototype for many such towers worldw ...
carries a rotating light assembly mounted atop, like used on lighthouses. These rotating lights were called aerial lighthouses in the world of European aviation and
airway beacon An airway beacon (US) or aerial lighthouse (UK and Europe) was a rotating light assembly mounted atop a tower. These were once used extensively in the United States for Visual meteorological conditions, visual navigation by airplane pilots al ...
s in the aviation of the United States. Such lamps were also used on other towers and on top of mountains in the earlier days of aviation until the end of the 1950s. * The last operational aerial lighthouse in the United Kingdom is on top of the cupola over the RAF College main hall at
RAF Cranwell Royal Air Force Cranwell or more simply RAF Cranwell is a Royal Air Force List of Royal Air Force stations, station in Lincolnshire, England, close to the village of Cranwell, near Sleaford. Among other functions, it is home to the RAF Colleg ...
. * In
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
there are only 12 operational rotating lights or aerial lighthouses in use. All of them are on top of very high towers in military airbases. *
Blosenbergturm The Blosenbergturm is a former radio transmission tower built for the German-language radio station DRS at Beromünster in the Canton of Lucerne, Switzerland, in 1937. It radiated first at 529 kHz and later at 531 kHZ, the lowest offic ...
in Beromünster also has an aerial lighthouse or rotating lamp above the cabin. In contrast to the Stuttgart TV Tower it is less bright and only operated at dawn. * In the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
aerial lighthouses are still in use on top of the mountains of
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
. * The
Eiffel Tower The Eiffel Tower ( ; ) is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower from 1887 to 1889. Locally nicknamed "''La dame de fe ...
in Paris, had an aerial lighthouse between 1947 and 1970, when the French aviation authority estimated that it was no longer needed to help aerial navigation, and set instead the standard warning lamps on top of the tower. In 2000 it was decided to uninstall the warning lamps and install again an aerial lighthouse visible by airplanes at 80 km. of distance. * In
Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...
the aerial lighthouse that was built in 1929 on top of the
Suomenlinna Church The Suomenlinna Church (, ) in Helsinki, Finland, was built in 1854 as an Eastern Orthodox Church, Eastern Orthodox garrison church for the Russian troops stationed at the Suomenlinna sea fortress. The fortress comprises five islands joined toget ...
by the aviation authorities in Helsinki, is still in use. * The main masts of
Mühlacker radio transmitter The Mühlacker Broadcasting Transmission Facility is a radio transmission facility near Mühlacker, Germany, first put into service on November 21, 1930. It uses two guyed steel tube masts as aerials and one guyed steel framework mast, which are ...
and the former Konstantynów Radio Mast also have aircraft warning lights at the outermost bases of their anchor guys. *
Conductor marking lights Conductor or conduction may refer to: Biology and medicine * Bone conduction, the conduction of sound to the inner ear * Conduction aphasia, a language disorder Mathematics * Conductor (ring theory) * Conductor of an abelian variety * C ...
and
Balisor Balisor is a system of illuminated beacons for high voltage power lines using a cold-cathode low-pressure neon lamp,David F. Rider '' Jane's airport equipment fifth edition'', Jane's Pub. Co., 1986 page 92 used as an aircraft warning light. D ...
s are sometimes used for marking power lines. * The Obstacle Collision Avoidance System allows the standard lights to remain off until an aircraft is within a given radius, allowing for a significant decrease in light pollution. The OCAS system also provides audio warnings.


Aircraft warning paint

Aviation laws also require towers and masts to be painted with equal length stripes of
international orange International orange is a color used in the aerospace industry and maritime industry to set objects apart from their surroundings, similar to safety orange, but deeper and with a more reddish tone. Variations There are several variants of inte ...
and white paint along their length to improve daytime visibility. This paint scheme is usually required on towers over 200 feet tall, but may vary from state to state and near airports internationally. Because such a paint scheme is expensive to apply, antenna towers and masts are often built to heights just below the level of requirement. Antenna towers and masts often also have other aircraft warning features located at equal distances along their height and at their tops. These may include high powered strobe lights or
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
lights in either red, white, or both colors in an alternating pattern. In such a case red is employed at night, while a white strobe is usually used during daylight hours.


Environmental impact

Warning lights on ground-based towers and buildings contribute to both
light pollution Light pollution is the presence of any unwanted, inappropriate, or excessive artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting sources, during the ...
and towerkill of birds.


Gallery

File:Antenna Tower 1.JPG, An antenna tower stands tall in
Springfield, MO Springfield is the third most populous city in the U.S. state of Missouri and the county seat of Greene County. The city's population was 169,176 at the 2020 census. It is the principal city of the Springfield metropolitan area, which had ...
with its red and white aircraft warning paint visible File:164-foot television antenna, Tower Life Building, 2006.jpg, An antenna tower tall in
San Antonio, TX San Antonio ( ; Spanish for " Saint Anthony") is a city in the U.S. state of Texas and the most populous city in Greater San Antonio. San Antonio is the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the U ...
with its red and white aircraft warning paint visible File:WSB-TV tower.JPG, An antenna tower tall in
Atlanta, GA Atlanta ( ) is the capital and most populous city in the U.S. state of Georgia. It is the seat of Fulton County and extends into neighboring DeKalb County. With a population of 520,070 (2024 estimate) living within the city limits, At ...
with its red and white aircraft warning paint visible.


References

{{DEFAULTSORT:Aircraft Warning Lights Aviation lights Aviation safety