We're reconsidering the role of pilot's watches in the modern era. We've republished the "Praise for Pilot's Watches" feature from Vol. 98 of Chronos Japan on webChronos. In this second installment, we'll look at the "flyback" and "12-hour counter" chronographs, two features that emerged during the evolution of pilot's watches.
Text by Masayuki Hirota (Chronos-Japan)
[Article published in the July 2022 issue of Kronos Japan]
Two new functions brought to the Pilot's Watch: "Flyback" and "12-hour counter"
In the 1930s, as aircraft performance improved dramatically, pilot watches underwent major changes. Among the new mechanisms adopted during this period, two had a major impact later on: the 12-hour counter and the flyback mechanism.
How did the "flyback" and "12-hour counter" come about?
François LeCoultre, a professor at the Geneva School of Watchmaking, wrote in the 1940s that the reason for the creation of long-time counters such as 12-hour counters was as follows:
"As sports became more popular, and perhaps due to the effects of the war, the demand for these instruments (author's note: chronographs) increased significantly, and it is true that many manufacturers began producing mechanisms such as minute counters (omitted)" ("A GUIDE TO COMPILICATED WATCHES")
The impact of the war, more precisely, was the birth of the long-range bomber. In 1935, Boeing developed the B-17 Flying Fortress, a bomber with "long legs" that could fly approximately 3000 km (approximately 6000 km unarmed). From then on, countries around the world began to work on developing aircraft capable of long-distance flight.
It is unknown which manufacturer developed the world's first 12-hour counter. However, from the mid-1930s through the 1940s, manufacturers such as Martell, Eberhard, Valjoux, Venus, and Lemania began to release chronograph movements with 12-hour counters. The U.S. military was perhaps the greatest beneficiary of this trend. For example, Colonel James Doolittle, who commanded the Great Tokyo Air Raid in June 1942, boarded a B-24 using a JARDUR chronograph with a 12-hour counter, the most advanced at the time. This example is on display at the Smithsonian's National Air and Space Museum.
Meanwhile, fighter pilots, who had a short flight range, needed a flyback function that allowed them to restart the chronograph without stopping it. Starting with the Longines 13ZN in 1936, the German UROFA completed the masterpiece flyback chronograph, the 59, in 1941. Approximately 4 of these complex and expensive chronographs were produced, primarily because of the Luftwaffe's demand. Later, the French Air Force recognized the usefulness of the flyback function and included it in their pilot watch specifications. Longines also developed a new 13ZN with a central 60-minute counter, but this was never widely adopted.
Although desired by many pilots, chronographs with 12-hour counters and flyback mechanisms were quite expensive, which is why there are so few pilot watches with these mechanisms. It was not until the mid-1980s that 12-hour counters and flyback mechanisms became widely used.
