An Overview of Aerial Navigation, Part 1

In the beginning, there was no navigation gear on airplanes. When Cal Rogers made the first flight across the continental U.S., his airplane did not have a compass. He followed railroad tracks across the country (by necessity, as he had a support train following him). He flew by what is now known as “pilotage”, finding one’s way by reference to features on the ground. Not only did he not have a way to use a map in flight, as he had no shelter from the wind, the maps of the day were not drawn for aerial navigation. There were few roads, fewer cars and if people wanted to travel, they took a train.

The first items that were added to airplanes to help in navigation were airspeed indicators, altimeters and compasses. Add to that the watch worn by the pilot (ever wonder why wrist watches became popular) and you could now fly by dead reckoning: Fly a course for a defined period of time. Dead reckoning has its limitations; you have to hold the course and it does not account for winds aloft. But before the beginning of rural electrification in the 1930s, that was all that was available at night over much of the U.S., as only cities were illuminated. A 1920s airmail pilot could fly for four hours on a clear night and never see a light on the ground between the two airports.

Pilotage, especially during the day, is still taught. Every pilot learns how to navigate by use of a sectional chart, a compass, a clock or watch and reference to ground features shown on the chart. This is relatively easy in areas with prominent rivers or roads or coastlines. Over mountain ranges and over the flatlands of the Midwestern prairie, one still has to resort to dead reckoning. At night, the lights of the towns help, but one has to keep a very good navigation plot, as one small town with some lights looks like any other small town.

The solution to the problem of finding one’s way at night for the first airmail pilots was a beacon system. The first beacon system was a series of bonfires in the early 1920s. The bonfires were soon replaced by lighted beacons which were, in essence, a series of lighthouses for aircraft. The beacons were spaced ten miles apart and were installed by 1933. Over 18,000 miles of airways were designated with the lighted beacon system in its heyday.

Lighted beacons are still in use today. The state of Montana maintains a lighted beacon system through some mountain passes. Beacons are still used to designate airports at night. During the day, a lighted beacon at an airport indicates that the weather conditions are too poor for operation by visual flight rules.

However, lighted beacons were limited. Flights could not be made in periods of low visibility. That took two developments: The instruments and skills to fly by instruments and the system to permit navigation by radio signals.

For that, stay tuned