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 is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...

. 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 ...

building A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and fun ...

s, and even fences located in areas where aircraft may be operating at low

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

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 ...

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

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 a ...

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) is an electric arc lamp designed to produce 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 Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

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 (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

and

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, 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

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) 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 200 and 500 feet (61-152.4 meters). If a medium white strobe is used on a structure greater than 500 feet (152.4 meters), the structure ''must'' be painted. The common medium white strobe flashes 40 times per minute, at an intensity of 20,000 candelas for daytime/twilight, and 2,000 candelas at nighttime. A high-intensity white strobe is used on structures that are taller than 700 feet (213.4 meters). 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 towers, lights may be energized either from the

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

surrounding the energized conductor, or the

magnetic field A magnetic field is a vector 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 to its own velocity and to ...

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 of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gradi ...

around conductors. The second approach is based on

Faraday's law of induction Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (emf)—a phenomenon known as electromagnetic inducti ...

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 weber ( ...

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 typic ...

s, tall buildings,

cranes Crane or cranes may refer to: Common meanings * Crane (bird), a large, long-necked bird * Crane (machine), industrial machinery for lifting ** Crane (rail), a crane suited for use on railroads People and fictional characters * Crane (surname), ...

and

wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...

s. Shorter structures that are located close to airports may also require lighting; an example of such is the south scoreboard at Lambeau Field in

Green Bay, Wisconsin Green Bay is a city in the U.S. state of Wisconsin. The county seat of Brown County, it is at the head of Green Bay (known locally as "the bay of Green Bay"), a sub-basin of Lake Michigan, at the mouth of the Fox River. It is above sea lev ...

built in 2013, which is the tallest structure in the general area of nearby Austin Straubel International Airport. 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 a ...

) 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

'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 lines more visible. Because power lines are often suspended between widely-spaced masts, they present a particularly grave hazard to low flying aircraft. 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 which 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 whic ...

Clampco_Sistemi_inductive_coupling_device

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

surrounding the energized wire, or the

produced by current through the wire. The first approach takes advantage of the high electric potential

between conductors, but a strong enough

capacitive coupling Capacitive coupling is the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit(s) nodes, induced by the electric field. This coupling can have an intentional or accidental ...

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

involving

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 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 insulated against ground and for feeding the lamps on the mast otherwise special devices like

Austin transformer An Austin ring transformer is a special type of isolation transformer with low capacitance and high isolation between the primary and secondary. It is formed of two interlocking rings: one with the transformer core and primary windings, much like ...

s would be required. *

Stuttgart TV Tower Fernsehturm Stuttgart ( en, Stuttgart TV Tower) is a 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 world ...

carries a rotating light assembly mounted atop, like used on lighthouses. These rotating lights were called

aerial lighthouse 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 navigation by airplane pilots along a specified airway corridor. ...

s in the world of European aviation and airway beacons 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

in the United Kingdom is on top of the cupola over the

RAF College The Royal Air Force College (RAFC) is the Royal Air Force military academy which provides initial training to all RAF personnel who are preparing to become commissioned officers. The College also provides initial training to aircrew cadets and ...

main hall at

RAF Cranwell Royal Air Force Cranwell or more simply RAF Cranwell is a Royal Air Force station in Lincolnshire, England, close to the village of Cranwell, near Sleaford. Among other functions, it is home to the Royal Air Force College (RAFC), which trai ...

. * In

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

there are only 12 operational rotating lights or

s in use. They are all of them 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 offici ...

in Beromünster also has an

or rotating lamp above the cabin. In contrast to the Stuttgart TV Tower it is less bright and only operated at dawn. * In the

aerial lighthouses are still in use on top of the mountains of

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

. * The

Eiffel Tower The Eiffel Tower ( ; french: links=yes, tour Eiffel ) 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. Locally nicknamed "'' ...

in Paris, had an

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 ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

the aerial lighthouse that was built in 1929 on top of the

Suomenlinna Church The Suomenlinna Church ( fi, Suomenlinnan kirkko, sv, Sveaborgs kyrka) in Helsinki, Finland, was built in 1854 as an Eastern Orthodox garrison church for the Russian troops stationed at the Suomenlinna sea fortress. The fortress comprises five ...

by the aviation authorities in Helsinki, is still in use. * The main masts of Mühlacker radio transmitter and the former Konstantynów Radio Mast also have aircraft warning lights at the outermost bases of their anchor guys. *

Conductor marking lights Aviation obstruction lighting is used to enhance the visibility of structures or fixed obstacles which may conflict with the safe navigation of aircraft. Obstruction lighting is commonly installed on towers, buildings, and even fences located i ...

and Balisors are sometimes used for marking power lines. * The

Obstacle Collision Avoidance System The Obstacle Collision Avoidance System (OCAS) is designed to alert pilots if their aircraft is in immediate danger of flying into an obstacle. OCAS uses a low power ground-based radar to provide detection and tracking of an aircraft's proximity to ...

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 to set objects apart from their surroundings, similar to safety orange, but deeper and with a more reddish tone. Variations of international orange Aerospace The Advanced Cre ...

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

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 unwanted, inappropriate, or excessive use of artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day ...

and

towerkill Towerkill is a phenomenon in which birds are killed by collisions with antenna towers. In poor visibility, birds may simply fly into the guy-wires. But night illuminations around the towers can also disrupt migration patterns, with disoriented bir ...

of birds.

Gallery

File:Antenna Tower 1.JPG, An antenna tower stands 446 feet (136 m) tall in Springfield, MO with its red and white aircraft warning paint visible File:164-foot television antenna, Tower Life Building, 2006.jpg, An antenna tower 146 feet (44.501 m) tall in San Antonio, TX with its red and white aircraft warning paint visible File:WSB-TV tower.JPG, An antenna tower 1,075-feet (327.5 m) tall in Atlanta, GA with its red and white aircraft warning paint visible File:Hershey Park roller coaster at night.jpg, Hersheypark roller coaster at night with white aviation obstruction lights which enhance the visibility of the ride and act as special effects.

References

{{DEFAULTSORT:Aircraft Warning Lights Aviation lights Aviation safety