The Birth Of Instrument Flying

In the early days of aviation, navigating in bad weather presented a real challenge for pilots, resulting in the early demise of many pilots.

There were no navigation aids to help pilots easily find their way from one airport to another. Back in the day pilots flew IFR, or I Follow Roads! 

Of course, when the weather turned bad it became more and more difficult to see the roads, and it was very easy to get off course.

These landmarks like roads worked fine for a while, and most pilots had rough maps to find their way, which worked OK during the daytime. 

But with the advent of airmail pilots flew around the clock, making night flight even more demanding.

To solve this problem pilots would enlist the help of post office staff, farmers, and the public to set up bonfires along the expected route. 

By July 1923 U.S. Army Air Service pilot Lt. Donald L. Bruner suggested lighted airport boundaries, lit windsocks, and rotating beacons mounted on towers at the airport. 

Taking this idea a step further, in 1923 the Post Office worked to establish a transcontinental airway system comprised of lighted beacons on towers spaced 15 to 25 miles apart, each beacon capable of being seen for about 40 miles.

An early airway beacon from 1923 consisting of both a rotating beacon and fixed course lights mounted atop 51-foot towers.

While these lighted airways allowed pilots to fly at night, they still had to maintain visual contact with the ground. 

Each tower had site numbers painted on it for daytime identification, at night the beacon light would flash a certain sequence so that pilots could match it up with the printed guide they carried.

In addition, each tower would have a fixed light shining back in the direction the pilot had come from, along with another fixed light shining in the direction the pilot was to fly next.

Postal Service Enhancements

By the mid-1920s the swashbuckling days of airmail operations had begun to fade, and the lone pilot with his leather jacket and white scarf in an open cockpit airplane fighting the elements was exciting but inefficient.

So, the Postal Service decided to focus on safety and reliability along with expanded operations. The Postal Service required minimum lighting requirements for all airmail stations.

The new requirements included a 500-watt revolving beacon which was designed to project a beam along the ground for the pilots to follow. A light was aimed at the windsock, and the aircraft were required to carry flares for forced landings.

The Postal Service also specified that all airports had to be at least 2,000 feet long by 1,500 feet wide to allow plenty of room for aircraft landings.

These lighted airways allowed pilots to fly at night, however, they still had to maintain visual contact with the ground.

Another problem faced by pilots was the only way to find out what the weather was like along their intended route was to talk to other pilots just before takeoff. If the weather changed en route they had no way to know.

Pilots, at that time, had no way to communicate with the ground or with other airplanes.

A Radiotelephone System

The National Bureau of Standards (NBS) was founded by Congress on March 3, 1901, as an authoritative domestic measurement and standards laboratory, and was the first physical science research laboratory of the federal government.

In 1926 the Bureau of Standards began to work on two-way technology, and by April of 1927 had a working ground-to-air radiotelephone system that could communicate over a distance of 50 miles.

Soon a transmitter was installed at Bellefonte, PA on the transcontinental airway which successfully communicated with an airmail plane 150 miles away! 

An early Air Mail radio station located at the Salt Lake City Air Mail Radio Station in March of 1928.

Also in 1928, the first practical radio navigation system became a reality. The system was installed on/near an airport, and it broadcasts low-frequency radio signals in four different directions. 

This system then allowed pilots to navigate directly to the station. Every other leg of the radio range transmitted morse code for the letters A or N (A - dit dah, N - dah dit). 

The first practical radio navigation aid for pilots was in 1928.

Pilots navigated using low-frequency radio by listening through their headsets to a stream of automated "A" and "N" Morse code letters.

As the pilot approached the station he would tune into the radio range station and listen for the signal. He would then turn the aircraft to the right or left upon hearing an "A" morse code signal, or to the right when hearing an "N" morse code signal.

Once the two morse code letters merged into a single tone the pilot knew he was on course for the station.

(As a side note, I had to navigate with this system a couple of times early in my flying career)!

Instrument Flying Becomes A Reality

 It's September 24th, 1929, and a young Lieutenant by the name of James H. Doolittle, a pilot in the U.S. Army Air Corps, made the first flight in a two-place Consolidated NY-2 Husky training aircraft completely blind flight.

The cockpit was covered by an enclosure over the cockpit, and Lt. Doolittle had no visual references. Not the sky, not the ground, none!

Doolittle piloted NX7918 from takeoff, climbed out to cruise altitude, navigated a predetermined 15-mile course, then returned to Mitchel Field and landed.

All using only the instruments in his cockpit.

The instrument panel in NX7918, the Consolidated NY-2 Husky Jimmy Doolittle flew.

Elmer Sperry, Jr. and Paul Kollsman, the names of which most pilots would be familiar, developed the experimental gyroscopic compass, the artificial horizon, and the precision altimeter used by Lt. Doolittle on his flight.

To locate the landing field the aircraft was equipped with a radio receiver attached to an instrument with two reeds which would vibrate if the aircraft was to the right or the left of the direct course to the airport.

Lt. James H. Doolittle sitting in the cockpit of NX7918 just prior to sealing up the cockpit for his record-setting flight.

This proved that flight in dense fog was possible, and made a giant leap in the utility of aircraft.

I hope you enjoyed this trip through some of the history of aviation. If you enjoyed this trip, and are new to this newsletter, sign up to receive your own weekly newsletter here: Subscribe here:

Until next time, keep your eyes safe and focused on what's ahead of you, Hersch!