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 conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respiratory ...

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 Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

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 waves to geolocalization, determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of Radiodetermination-satellite servi ...

aids such as

NDB NDB may refer to: Finance * National development bank, set up by a country's government to improve that country's economy * New Development Bank, a development bank jointly operated by the BRICS nations * NDB Bank, Sri Lankan commercial bank Pol ...

(non-directional beacon), VOR (VHF omnidirectional ranging) and

DME DME may refer to: Chemicals * DME (psychedelic), 3,4-dimethoxy-beta-hydroxyphenethylamine, a psychedelic drug * Dimethoxyethane, a solvent * Dimethylethanolamine, a precursor molecule for C-choline * Dimethyl ether, a fuel and an aerosol spray pro ...

(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 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 ...

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 (coal gas or formerly also water gas) is stored near atmospheric pressure at ambient temperatures. The volume of the container follows t ...

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 (often abbreviated St. Paul) is the List of capitals in the United States, capital city of the U.S. state of Minnesota and the county seat of Ramsey County, Minnesota, Ramsey County. As of the 2020 United States census, 2020 census, ...

at the Indian Mounds Park on a bluff overlooking the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

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

Rocky Butte Rocky Butte (previously known as Mowich Illahee and Wiberg Butte) is an extinct cinder cone butte in Portland, Oregon, United States. It is also part of the Boring Lava Field, a group of volcanic vents and lava flows throughout Oregon and Was ...

Portland, Oregon Portland ( ) is the List of cities in Oregon, most populous city in the U.S. state of Oregon, located in the Pacific Northwest region. Situated close to northwest Oregon at the confluence of the Willamette River, Willamette and Columbia River, ...

since 1929, though it was officially 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 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 generated ...

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 Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...

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

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 unit's 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 letter (message), letters and parcel (package), parcels, providing post office boxes, and selling postage stamps, packaging, and stationery. Post o ...

and the

Department of Commerce The United States Department of Commerce (DOC) is an United States federal executive departments, executive department of the Federal government of the United States, U.S. federal government. It is responsible for gathering data for business ...

between 1923 and 1933. The

Low Frequency Radio Range The low-frequency radio range, also known as the four-course radio range, LF/MF four-course radio range, A-N radio range, Adcock radio range, or commonly "the range", was the main Radio navigation, navigation system used by aircraft for instrumen ...

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 o ...

. Those in Montana are charted on the Great Falls

sectional chart In United States aviation, a sectional aeronautical chart, often called a sectional chart or a sectional for short, is a type of aeronautical chart designed for air navigation under visual flight rules (VFR). In Australia, Canada and some other ...

. Montana was the last state to officially maintain airway beacons, through the state's Aviation Division. In 2017, the decision was made by Aeronautics Division to discontinue their maintenance of the system, due to the system's obsolete nature and budgetary concerns. The system was to be shut down entirely by December 31, 2021. In spring of 2018, fourteen of the seventeen beacons were shut down by MDT. The Montana Department of Transportation's Communications Bureau took over care of beacons at St. Regis and Lookout Pass. Six beacons are now in the care of the owners of the land they were erected on, six are in the care of a non-profit, Idaho Aviation Heritage, and four are in the care of local governments. Due to their historical significance in the state, the beacons at Homestake Pass, Canyon Resort, MacDonald Pass, Silver Bow, Spokane, Lookout Pass, St. Regis, Whitetail are in the process of being listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...

. The strawberry Mountain beacon was demolished in the summer of 2021. MDT's Aeronautics Division removed the beacon and donated it to the Montana Historical Society.

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 A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lens (optics), lenses and to serve as a beacon for navigational aid for maritime pilots at sea or on inland waterways. Ligh ...

History of lighthouses Communication towers in the United States