Headlight

Definition

For the French administration, a headlight is a maritime establishment of indication on fixed support comprising at least two criteria among the four below:

Function: establishment of great landing or marking out;
Height: establishment a total height above the ground of more than 20 meters;
Intensity: establishment whose fire is of an intensity higher than 100.000 Candéla S;
Infrastructure: establishment sheltering in its enclosure one or more buildings of the Office of the Headlights & Beacons.

By contrary definition, the Feux are the other establishments.

Etymology

The word headlight, comes from the Greek Pharos, who is the name of the island where was the Phare of Alexandria. This origin is preserved in many languages, as Italian (faro), Spanish (also faro) and Portuguese (farol). However, certain languages like English quite simply created a made up name ( lighthouse ), explaining the function of the headlight clearly.

Maritime headlights

The maritime headlights were the first means for the ships of locating the danger zones and the ports. Today, with the modern systems of positioning, their use rarefies. Thus, there are only 1.500 maritime headlights still in service in the world.

First maritime headlights

The first maritime headlights probably appeared in the Antiquité, when the marine started to develop. They mainly made it possible to locate the ground, as well as the port cities. One can even regard the volcano Stromboli and his small regular eruptions (approximately every fifteen minutes at present) as the oldest (and one of most powerful) headlight of the Mediterranean (sailors making use of it indeed like reference mark).

The first civilizations to build headlights were the Romain S and the Greek S.

Constitution

Turn

The tower is used as support with the system of optics. Its height determines its geographical range, which corresponds to the maximum distance where one can see the headlight.

The shape of the tower is generally round. That enables him to better resist the gusts of wind, which can be very powerful close to the coasts.

Optical system

The system of optics is at the top of the tower. It is consisted of the source of light, of a system of lenses, the whole is then placed in a lantern.

To use the supplied luminous energy as well as possible, it is concentrated:

the beam is flattened on the vertical axis not to scatter unnecessarily.
In the horizontal direction, one or more rays are created simultaneously and sweep the horizon in order to be seen in all the directions.

Traditionally, one concentrates the light by a system of lenses in rotation. In the very old headlights, lighting was ensured by an oil lamp and rotation by a mechanism of clock industry. The frame on which optics rested could rest on mercury in order to reduce the friction. One then used bulbs and electrical motors, supplied with a generator which also provided electricity to the guard of the headlight.

It is not obvious to effectively concentrate a luminous flow starting from an omnidirectional source. To avoid using lenses a too great thickness, one developed the system of the lenses of Fresnel specifically for this employment. Their design makes it possible to obtain a large diameter and a focal Distance sufficiently short, without the weight and volume inherent in traditional lenses. Certain headlights, as those of Cape Race with Newfoundland and the Makap' uu Point of Hawaii use lenses hyperradiantes manufactured by the company Chance Bros.

Not to be confused with other sources of light, the headlights emit an intermittent light.

Evolutions

At the beginning of the 20th century, the inventor Swedish Gustav Dahlén and firm AGA created systems able to automate the operation of the headlights and thus to remove the human presence. However, much of headlights remained still inhabited (until the Années 1990), in particular because the guard could also take part in missions of rescue. Nowadays, that is now exceptional. Certain headlights are maintained only because they are used as tourist attraction, but one still continues to build some in danger zones, some producing a directional Feu. Automation, if it made it possible not to send men in solitary and dangerous places more, however leaves without constant monitoring the buildings of the historical wonders like Ar-Men, the Old woman or Kéréon and, at the beginning of the third millennium, much of these headlights can be considered in danger if no voluntarist protection plan is undertaken. In the modern headlights, uninhabited, the system of lenses in rotation is often replaced by omnidirectional, short and intense flashes (in this case one rather concentrates the light in time than in space). These light signals are similar to those used for air indication. Their power supply is generally ensured by solar energy.

The Soviet Union also built certain of number of headlights using the energy of a thermoelectric Générateur to radioisotope. That poses environmental problems, because the bad maintenance of these uninhabited headlights can involve radioactive contaminations. That also presents security issues, the radioactive element being able to be stolen to make a radiological Bombe.

Luminous signature of the headlight

The light signal emitted by a headlight or a boat headlight has specific characteristics which make it possible to the sailors to identify it and to use it to determine their position and/or their road.

One distinguishes:

fires with short or long glares : they briefly emit one or more signals of light. The periods of extinction are longer than the periods of light.
fires scintillating : the signals of light very short and are very brought closer
fires isophases : the duration of the periods of light and extinction identical
fires to screenings are: the periods of extinction are shorter than the periods of light.

The complete signature of the headlight is provided by:

the color of the light signal: generally white (visible moreover further), sometimes red. The green is reserved for fires with sector because this color is visible only of relatively close (fires with sectors emit a signal of several colors: it generally clarifies in white the zone of healthy navigation, in green and red the danger zones located at Bâbord and Tribord of the healthy zone).
the number of the luminous glares or the phases of darkness
the period at the end of which fire reproduces the same sequence of glares or periods of darkness: for example 15 seconds

To avoid any misidentifying, two headlights located in the same zone of navigation will never have the same characteristics.

The signals emitted by the headlights, the description of the headlights (height of the headlight, height to the top of the sea level), their theoretical range and their position are provided in works published by the hydrographic services (SHOM for France, UKHO for the United Kingdom…) : books of fires/Admiralty List off Lights and Fog Signals . This information also appears in more local guides (for example in France for the Atlantique coast and the English Channel the Almanach of the Breton Sailor).

This information is noted on the sea charts in a shortened form, the codes are available in the work 1D of the SHOM (symbols and abbreviations being reproduced on the French sea charts).

Here an example: " Fl (3) G 12s" mean: fire with 3 green glares, period 12 seconds); the principal elements of this legend are:

the first abbreviation indicates the type of fire: flash-light: Fl (for Flash ), scintillating fire: Q (for Quick ), fire isophase: Iso, light Occ occulting;
the number of glares or screenings is given between brackets (nothing: 1 only glare or screening)
the second abbreviation gives the color: no mention for white fires; G: green (for Green); R for red (Red), Y for yellow (Yellow);
the period is given in seconds;
the height is given in meters (ex: 75m);
the range in miles is indicated in the form " X M" (example: 8M for a range of 8 marine miles);
the complementary aural signals can be appeared in the form of a mention (Horn for a foghorn, Whis (Whistle) for a whistle;
when fire carries a radio beacon, the legend is supplemented by RC (circular radio beacon).

Complex example of legend: Fl 5s 60m 24M Siren (1) 60s RC mean: fire with a white glare every five seconds, of which the lantern is located at a 60 m height, carrying to 24 miles, provided with a siren emitting a signal every 60 seconds and with a radio beacon

Classification by the guards of headlight

According to the hardness of the living conditions inside, the guards of headlight French indicated the headlights according to three names:

the Paradise, headlights located at ground,
the Purgatory S, headlights located on islands,
the Hell S, headlights isolated at sea, which imply in addition to the dangerous changings.

This classification also corresponded to a progression of career, which started in a hell to finish in a paradise.

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