Transcontinental Airway System

The 1924 U.S. Air mail route

The Transcontinental Airway System was a navigational aid deployed in the United States during the 1920s.

History

In 1923, the United States Congress funded a sequential lighted airway along the transcontinental airmail route. The lighted airway was proposed by NACA, and deployed by the Department of Commerce. It was managed by the Bureau of Standards Aeronautical Branch. The first segment built was between Chicago and Cheyenne, Wyoming. It was situated in the middle of the airmail route to enable aircraft to depart from either coast in the daytime, and reach the lighted airway by nightfall. Lighted emergency airfields were also funded along the route every 15–20 miles.

Construction pace was fast, and pilots wishing to become airmail pilots were first exposed to the harsh wintertime work with the crews building the first segments of the lighting system.^[1]

By the end of the year, the public anticipated anchored lighted airways across the Atlantic, Pacific, and to China.^[2]

The first nighttime airmail flights started on July 1, 1924. By eliminating the transfer of mail to rail cars at night, the coast to coast delivery time for airmail was reduced by two business days. Eventually, there were 284 beacons in service.^[3] With a June 1925 deadline, the 2,665 mile lighted airway was completed from New York to San Francisco. In 1927, the lighted airway was complete between New York and Salt Lake City, Los Angeles to Las Vegas, Los Angeles to San Francisco, New York to Atlanta, and Chicago to Dallas, 4121 miles in total. In 1933, the Transcontinental Airway System totaled 1500 beacons, and 18000 miles^[4]

Technical

These are the remnants of Transcontinental Air Mail Route Beacon 37A, which was located atop a bluff in St. George, Utah, U.S.A. With concrete arrows indicating the direction to the next beacon, a rotating light tower, and a shed that usually held a generator and fuel tanks, these beacons were once situated every 10 miles on air routes across the United States beginning around 1923.

The lighted Airway Beacons were a substantial navigation aid in an era prior to the development of radio navigation. Their effectiveness was limited by visibility and weather conditions.

Twenty four inch diameter rotating beacons were mounted on 53-foot (16 m) high towers, and spaced ten miles apart. The spacing was closer in the mountains, and farther apart in the plains. The beacons were five million candlepower, and rotated six times a minute. "Ford beacons" (named after Ford Car headlights) were also used, placing four separate lights at different angles.^[5] Airports used green beacons and airways used red beacons. The beacons flashed identification numbers in Morse code. The sequence was "WUVHRKDBGM" prompting the training phrase "When Undertaking Very Hard Routes Keep Directions By Good Methods." to remember the sequence.^[6] Engineers believed the variations of beacon height along hills and valleys would allow pilots to see beacons both above ground fog, and below cloud layers.

Towers were built of numbered angle iron sections with concrete footings. Some facilities used concrete arrows pointing in the direction of towers. A small outbuilding was needed, with a generator for power if none was available. Some building also served as weather stations. Many arrow markings were removed during WWII, to prevent aiding enemy bombers in navigation, while 19 updated beacons still remain in service in Montana.^[7]

References

Wikimedia Commons has media related to Transcontinental Airway System.

External links

• Concrete Arrows and the U.S. Airmail Beacon System. Sometimes Interesting. 04 Dec 2013