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I have always been fascinated by air navigation chronographs. For decades, these high precision instruments helped pilots determine their position and flight path, in real planes and under real flight conditions. In this post we will be examining a piece of equipment which enabled the pilots to determine the position of enemy military targets, among other things.

The instrument in question is the flight chronograph developed by the Soviet Union based on a Jaeger-LeCoultre patent from the 1930s, the АЧХ0 or ¨Soviet Chronofite¨.

In the mid-1930s, the Soviet Union acquired flight timers from the Swiss Jaeger-LeCoultre. The overall modernisation of the Soviet military required precision instruments for new aircraft, such as the Poliarkov I-16. Jaeger-LeCoultre began deliveries of its Chronoflite, which was the first time piece that added a stopwatch and flight hour counter to a cockpit clock. Below we can see the original Chronoflite.


About the same time, the US Air Force had a similar requirement for this type of instrument for its aircraft, such as the Douglas SBD-5, among others.

It is fairly well documented that during the Second World War, Moscow’s First State Watch Factory began to develop its own ¨Chronoflite¨ model. In the images below we can compare the first АЧХ that was built in Moscow, around 1940, with its predecessor, built by Jaeger-LeCoultre. We can compare the movements too.

A number of recurring questions tend to arise when researching these types of instruments. Did the Soviets buy the patent from Jaeger-LeCoultre, or did they just copy it? Why did Jaeger-LeCoultre stop shipping the Chronoflite to the US military around the same time? Could the the Elgin 37500, manufactured for the US military, also be considered a copy of the Chronoflite?

It is common to come across historiography that inevitably assigns the role of plagiarist to the Soviets, whereas it always seem conveniently forgotten when the Americans ¨borrow¨ intelectual property. There are clear examples of the latter. For instance, the Hamilton M21 seems as evidently ¨inspired¨ by a marine chronometer developed by Ulysse Nardin as the Kirov Marine Chronometer, yet only the latter is widely considered a copy.

At the end of the Second World War, Moscow’s First State Watch Factory continued with the build these time pieces, until the mid-1960s. Mere aesthetic and functional changes to the design were introduced during these two decades. I own a unit which was manufactured in the second quarter of 1962 (see further below). It includes a legend of 5-days, instead of the original 8-days. I believe that this substantial reduction in the power reserve was introduced in order to improve the instrument’s precision.

Towards the end of the production run, manufacturing was actually moved to Chelyabinsk (to the Molnija plat). At this stage, the original caliber was heavily modified, with 12 jewels added, alongside a second main spring to ensure more consistent time-keeping as the power reserve was drawn down. The instrument was renamed the АЧC-1. Among important modifications, the luminescent radium was removed from the hands and dial, and replaced with a phosphorus-based lume. Some movements saw the power reserve reduced down to two days, again to increase precision. In addition, a number of tweaked dial configurations were also introduced.

Below you can see the case-back of my time piece.


It was manufactured in Moscow’s First State Watch Factory (the factory seal is visible in the centre). The 27V marking indicates the voltage required for the included heating element. Lastly, its weight of 450 g is also listed. The heater, perhaps a surprise to many, was an absolutely necessary element to operate in the Mig cockpits, as the aircraft were not pressurised and the instruments were exposed to very cold temperatures at high altitudes, and on the ground on a seasonal basis. The label on the back of the instrument dates the piece to the second quarter of 1962, which means it was probably meant for a Mig 15, the type of aircraft in which Yuri Gagarin died in an accident in 1968, training for a second space mission.

The functions of the timepiece are as follows:

  • A 12-hour flight counter, which its operated via the left-hand side red button, and is shown in the 12 o’clock sub-dial. This includes a colour-coded indicator circle to show whether it is active (red), stopped (red and white) or if it has been reset (white).
  • A chronograph, which is operated via the right-hand side silver button. The minute counter in the 6 o’oclok sub-dial curiously moves leftwards, counter-clockwise. At first, I thought it was a countdown function! The central seconds hand only runs when the chronograph is engaged. The same button serves as the stop and reset actuator, and there is no lock mechanism.
  • A normal hours and minutes indication.

The red button is also used to set the clock, pulling on it to extract it like in a wristwatch, and it is also used to wind the instrument. Attention is required when doing this, as power is delivered via counter-clockwise turns, a feature common to both the Jaeger-LeCoultre Chronoflite as well as the АЧХ. This button does not lock either. Because of the unusual wind configuration, it was not uncommon for users to pull the crown, turn it clockwise, and break it.

In the АЧC-1, and subsequent versions, some, but not all, of these potential usage problems were corrected by adding a lock to the chronograph button.

The caliber in my unit has a 5-day power reserve, 13 large jewels (4 mm) and it beats at 21,600 vibrations per hour.


If you ever consider purchasing a time piece of this type, please pay particular attention to the date of manufacture, as the first units are known to be highly radioactive and can be dangerous.

2 comentarios en «The АЧХ0 Soviet Chronoflite»

  1. aviation_watch

    Fascinante pieza Miquel.
    Pero, no soy parte desinteresada porque como piloto el artículo me trae recuerdos de las cabinas de antaño, como las de los Cessna en los que aprendí a volar.
    Ahora ya tenemos todos los instrumentos digitales. En la cabina de mi ultra-ligero sólo queda uno analógico, el ASI, o indicador de velocidad relativa.

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