Forgotten landmarks: The USA's concrete arrows of aviation history
In the USA, large, overgrown concrete arrows once served as navigational aids. These significant symbols, visible from the air, remind us of a past system that can be considered a forerunner to today’s GPS.
25 November 2024 14:19
These concrete arrows were a part of a visionary project from the early days of aviation. Initially, the primary task for aircraft was the transportation of mail. However, as this task evolved, a challenge emerged: how to navigate effectively to ensure precise delivery? In areas with varied landscapes, distinctive features could serve as guides. The real issue arose on vast plains, where pilots primarily relied on the Sun. When the sky was overcast at night, navigating by the stars was also difficult.
Transcontinental Airway System – how was navigation created?
The solution to these challenges was the ingenious Transcontinental Airway System, which functioned as a large-scale postal infrastructure.
Starting in 1923, markers were constructed – large, several-metre-long concrete arrows coated with bright yellow paint, visible from a substantial distance, even from an altitude of 10 miles. At the tip of each arrow, a concrete platform supported a 52-foot lattice navigation tower, which, like a lighthouse, was equipped with a 24-inch reflector that was turned on at night.
In addition, each installation featured coloured lights emitting Morse code signals with an identifier, and in areas without power lines, small buildings housing electricity generators were constructed.
Within a year, arrows placed every dozen miles outlined a route connecting New York and San Francisco, covering nearly 2,700 miles and utilising 284 markers.
The concrete navigation system proved effective. Previously, mail was transported at night by vehicles, but with the Transcontinental System, flights became feasible around the clock. The infrastructure included emergency runways, illuminated every few dozen kilometres at night.
Concrete arrows on the continent - what are they used for?
Thanks to the Transcontinental Airway System, delivering a letter across the USA took just two days. The system quickly expanded to 1,500 arrows, marking a network of 18,000 miles of air routes.
However, modern technologies, such as radio navigation, soon began to replace this infrastructure. During World War II, some installations were dismantled to prevent them from aiding enemy air forces.
Many concrete arrows have survived to this day. To see them, one can simply use Google Maps. Today, 14 active markers still function in Montana.
