The curious story of the first control tower that was erected a century ago.

Nowadays, it is unthinkable to organize air traffic without the emblematic control towers that are present in all the major airports of the planet.

From there, controllers coordinate the movements of thousands of planes so that they remain at a safe distance from each other and from obstacles.

They also direct routes in the event of bad weather and decide when planes should land and take off, trying to avoid delays but, above all, to prevent accidents.

But it was only towards the end of World War I, in the 1920s, when passenger air transport services began to grow, that the world’s first air traffic control tower was erected.

It was at London’s then main airport, which was in Croydon, about 20 km south of the capital.

In February 2020, the 4.5 metre high building with windows on all sides turned 100.

The tower had been commissioned by the Ministry of Aeronautics, a former department in charge of civil and military aviation that ceased to exist in the mid-1960s.

“These were the early years of air travel and there was no sign of a roadmap for how things should work,” Ian Walker, director of the Historic Croydon Airport Trust, told the BBC.

“In 1920, we had no idea how a control tower and even an airport should work. So the pioneers had to develop, test and implement the ideas that would allow air travel to grow safely,” says Walker.

At the time, airfields had radio systems and rooftop-like structures, but none of these facilities were specifically intended to provide transit services to aircraft.

It was the construction of this first tower that began the growth and development of commercial aviation.

Weather Forecast

Initially, the first commercial pilots flew in converted military aircraft and could only do so when the weather conditions were right.

However, when the number of commercial flights started to increase, following strict dates and schedules, the need to be able to fly in different weather conditions arose.

From that moment on, when it was no longer enough for pilots to be guided by their own eyes and maps, the newly formed International Air Navigation Commission established that major airports should send and receive weather reports.

“What these pioneers did was to use the most advanced technology they had at the time, radio, to develop air traffic control,” Walker said.

They simply, he adds, “experimented to see what worked and what didn’t.

The first controllers worked together with the radio operators, giving pilots weather information by radio or by flag or light systems.

Position

At Croydon airport, a service was also used to determine the position of the aircraft in the air.

“When an aircraft makes a radio transmission, we can trace the source of that signal. If the signal is picked up by ground stations, it is possible to triangulate the position of the aircraft,” says Walker.

This information, picked up by three different stations, was transmitted to Croydon, from where the position of the plane was calculated manually on a map, with the help of ropes and pins, and then transmitted to the pilot.

With this information, the controllers were also able to calculate the arrival and departure times of the planes.

Emergency

Another of the great moments in aviation that dates back to this time at Croydon airport was the invention of the distress signal to alert in emergency situations.

The word Mayday (pronounced “meidei”), repeated three times, was coined by Fred Stanley Mockford, one of the first controllers of the Croydon Tower, who was inspired by the French expression m’aider , which means “help me”.

“It’s a word that should not be confused with anything else in aviation: it’s not height, or speed, or visibility, or wind. It is a word different from others, and the industry accepted it in 1927 as an international standard”.

In 1923, a second tower was added in Croydon and the last one was erected in 1928.

The airport continued to operate until 1959 and in 2000 it was transformed into a museum.

By BBC