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 The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to ...

corridor. In Europe, they were used to guide aircraft with lighted

beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More mode ...

s at night.

UK and Europe

United Kingdom

A network of aerial lighthouses was established 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 European mainland, continental mainland. It comprises England, Scotlan ...

and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

during the 1920s and 1930s. Use of the lighthouses has declined with the advent of

radio navigation Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination. The basic principles a ...

aids such as NDB (non-directional beacon), VOR (VHF omnidirectional ranging) and DME (distance measuring equipment). 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 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 tra ...

Netherlands

In the Netherlands,

gas holder A gas holder or gasholder, also known as a gasometer, is a large container in which natural gas or town gas is stored near atmospheric pressure at ambient temperatures. The volume of the container follows the quantity of stored gas, with pressu ...

s were painted with an arrow pointing north and two letters identifying their location.

United States

Transcontinental Air Mail Route Beacon 37A

Approximately 1,500 airway beacons were constructed to guide pilots from city to city, covering . Today, most of the beacons have been removed, but the State of Montana continues to maintain several as navigation aids in mountainous terrain. One beacon is preserved for historical purposes in

Saint Paul, Minnesota Saint Paul (abbreviated St. Paul) is the capital of the U.S. state of Minnesota and the county seat of Ramsey County. Situated on high bluffs overlooking a bend in the Mississippi River, Saint Paul is a regional business hub and the center ...

at the Indian Mounds Park on a bluff overlooking the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...

. A rotating airway beacon has been in continuous operation at the summit of Rocky Butte in

Portland, Oregon Portland (, ) is a port city in the Pacific Northwest and the list of cities in Oregon, largest city in the U.S. state of Oregon. Situated at the confluence of the Willamette River, Willamette and Columbia River, Columbia rivers, Portland is ...

since 1929, though it was decommissioned during the 1960s. Recently, the beacon at

Grants, New Mexico Grants is a city in Cibola County, New Mexico, United States. It is located about west of Albuquerque. The population was 9,163 at the 2020 Census. It is the county seat of Cibola County. Grants is located along the Trails of the Ancients B ...

was restored for historic preservation, using original items found at other nearby sites. A large concrete slab, in the shape of an arrow, was located near the base of each beacon. Many of these arrows remain today, some of which are visible from satellite pictures, even in urban settings.

Light characteristics

An airway beacon has two distinct light characteristics: A revolving narrow white light beam about 5 degrees wide in azimuth and a set of fixed colored course lights of about 15 degrees width.

White rotating beacon

The rotating beacon 24 inch (610 mm)

parabolic mirror A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a Mirror, reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface ge ...

and a 110-volt, 1 kilowatt lamp. spinning at 6 rpm, creating a quick one-tenth second flash every ten seconds. In clear weather they could be seen for 40 miles (64 km). Montana took steps to modernize their beacons, encasing newer light systems in clear domes.

Red or green course lights

Just below the white beacon, a set of red or green course lights point along each airway route. Red lights denote an airway beacon between landing fields while green denotes a beacon adjacent or upon a landing field. These course lights flash a Morse code letter identifying the beacon to the pilot. Each beacon is identified with a sequential number along the airway, and flash the red or green course lights with the Morse code ID of one of 10 letters: W, U, V, H, R, K, D, B, G or M. The letters represent the digits of 1 through 10 (W = 1, ..., M = 10). The course lights turn on for 0.5 second for a dot, 1.5 second for a dash with a 0.5 second between each dot or dash. A pause of 1.5 seconds separates each letter. To help remember the letters and their sequence number, pilots memorized the following: "When Undertaking Very Hard Routes, Keep Direction By Good Methods." The beacons are depicted on navigation charts along with their number and Morse code pattern. For example, beacon number 15 would have a code digit of 5 (the units digit), hence the letter ''R'', and Morse code: "dit dah dit" (·−·).

History

Airway beacons in the US were constructed by the

Post Office A post office is a public facility and a retailer that provides mail services, such as accepting letters and parcels, providing post office boxes, and selling postage stamps, packaging, and stationery. Post offices may offer additional ser ...

and the Department of Commerce between 1923 and 1933. The Low Frequency Radio Range system began to replace this visual system in 1929. The last visual airway beacon was supposedly shut down in 1973, but a few airway beacons are still operating in

and

Western Montana Western Montana is the western region of the U.S. state of Montana. The most restrictive definition limits western Montana only to the parts of the state west of the Continental Divide. Other common definitions add in the mountainous areas east ...

. Those in Montana are charted on the Great Falls

sectional chart {{short description, Type of aeronautical chart In United States aviation, a sectional chart, often called a sectional for short, is a type of aeronautical chart designed for air navigation under visual flight rules (VFR). In Australia, Canada an ...

. They are maintained by the

Montana Department of Transportation The Montana Department of Transportation (MDT) is a governmental agency in the U.S. state of Montana, responsible for numerous programs related to the construction, maintenance, and monitoring of Montana's transportation infrastructure and operati ...

Aeronautics Division.

References

External links

"Arrows Across America; Transcontinental Air Mail Routes"
{{Authority control Beacons Aeronautical navigation systems Aviation history of the United States Transportation infrastructure in the United States United States Postal Service United States Department of Commerce 1923 establishments in the United States Lighthouse Lighthouses Communication towers in the United States