Pilot’s watches

Five firms built the German air force’s observation watch: A. Lange & Söhne, Laco, Stowa and Wempe in Germany and IWC Schaffhausen in Switzerland. Laco, Stowa and IWC still make watches on its pattern. Two other German makers came to the subject later: Sinn, which makes cockpit clocks as well as pilot’s watches, and Damasko, whose DC 56 chronograph test pilots at Airbus Defence and Space in Manching have worn since 2007. Before any of them, Longines made a navigation watch for Charles Lindbergh.^{1, 2, 4, 5, 6, 7, 8}

Before radio aids and satellite positioning, a navigator over open water fixed his position from the sun and stars, and that needed the exact time; GPS has since taken over the task.^2, 4, 9

After his non-stop flight from New York to Paris in 1927, timed by Longines, Charles Lindbergh sought help from the navigator Philip Van Horn Weems and drew up a watch to serve as an air-navigation instrument. Longines made it from 1931 as the Lindbergh Hour Angle watch, with a turning bezel and a rotating centre dial that let a pilot work out longitude from the hour angle of the sun.^2, 9

The German air ministry (the Reichsluftfahrtministerium) set the design of a watch for its bomber navigators, the B-Uhr, short for Beobachtungsuhr, observation watch. It was a 55 mm wristwatch built around a pocket-watch movement, with a black dial, a crown large enough to turn in gloves, and seconds that stopped when the crown was pulled so that it could be set exactly against the chronometer before a flight. Each case was engraved FL 23883.^1, 4, 5

The early dial (Baumuster A) carried the hours in the usual way; the later Baumuster B put a large minute ring outside and the hours on a small inner ring. Accounts of when Type B arrived differ: 1941 in one, around 1942 in another.^1, 4

Stowa reissued its own in 1997, and Laco recreated its wartime watches in a limited series in 2000. Both firms now build most of their pilot’s watches on the two dial patterns.^{4, 5, 10, 11}

DIN 8330, published in March 2016, sets out what a pilot’s watch must do and how it is tested. Part 1 covers legibility, vibration, resistance to fluids used in flight operations, magnetism and, new to watch standards, compatibility with night-vision equipment; part 2 sets out how conformity is assessed, as the basis for certification. The requirements change with the flight rules: for instrument flight a chronograph is needed as well as a rotating bezel.^3, 12

The standard grew out of TESTAF, a test scheme presented in 2012 by Sinn and FH Aachen University of Applied Sciences. Sinn says it initiated TESTAF and proposed it as the basis for a DIN standard; Stowa says it was among the companies that worked on DIN 8330. Laco’s certified watches pass sixteen tests in three groups, some of them at FH Aachen.^{4, 7, 12, 13}