MasterHorologer

IWC Schaffhausen UTC Pilot’s Watch (1998)

Originally introduced in 1998, the UTC pilot’s watch from IWC was designed especially for globetrotters and pilots who regularly travel across several time zones and continents. This watch is a perfect companion that will keep track of the time at home but also show the correct time as he or she travels backwards and forwards from one time zone to another, crossing the dateline, even if it means moving back the date.  The dial shows the date in hours, minutes and seconds, as well as the date, but just below 12 o’clock it has a window for a 24-hour display.

In 24 hours, the hour hand, as normal, goes completely round the dial twice while the 24- hour display completes one revolution.After hour hand completes two revolutions, the date advances. If the hands and the 24-hour display are synchronised, the latter shows us whether it is day or night in the time zone in question. If we wish to set or adjust all the watch’s functions, the crown is pulled out to the second, or outermost, position. In this way, the time and the 24-hour display, to which it is linked, can be set synchronously.

The UTC watch’s special feature, however, is revealed when the crown is pulled out to the middle position. Now it is possible to move just the hour hand quickly forwards or backwards in one-hour steps. If it is advanced past midnight, the date display too moves to the next day. If, on the other hand, it is wound backwards past midnight to the previous day, the date display moves back a day. The 24-hour display remains totally unaffected by all these adjustments and continues to show home time or the international time standard used in aviation known as Universal Time Coordinated (UTC).

What does UTC mean?
Effectively the UTC Time corresponds to the Greenwich Mean Time (GMT). We say that the time in Central Europe is one hour ahead of GMT (GMT +1) and that the time in New York, say, is five hours behind (GMT –5). Incidentally, the UTC pilot’s watch handles changes from standard to summer time with absolutely no hassle. Its mechanical movement can be set or adjusted to any of the 24 time zones without ever losing track of standard time.

Starting at GMT, the time advances by one hour every 15 degrees of longitude in an easterly direction or goes back when we travel west. For the sake of completeness, there are a few regional exceptions with half-hourly increments and a number of other irregularities. Since all flight schedules are drawn up on the basis of UTC, the UTC pilot’s watch is ideally tailored to the needs of professional pilots. The use for ordinary travellers is also evident, as they can set the 24-hour display to any other time zone, such as home time.

How UTC mechanism by IWC works?
To understand the basics of the UTC mechanism by IWC, we need to know that the rotations provided by a wheel of the movement (the minute wheel) are converted into coordinated revolutions of the minute and hand hours by a train of cogs located under the dial and known as the geartrain. Actually, in this case we are interested only in the hour hand because the minute display is not normally affected when we adjust the watch to another time zone. The geartrain is usually geared in such a way that the hour hand, or the wheel to which it is attached, rotates once every twelve hours while the minute hand completes 12 revolutions during the same period. In addition, whenever the hour wheel completes two revolutions, a date advance system moves the date on by one position.

For the UTC pilot’s watch, IWC had to develop two completely new gear trains, starting at the hour wheel. Let us begin by seeing what happens in the case of the 24-hour display. Here, the first of these trains reduces the rotation of the 24-hour display wheel (complete with disc) to a ratio of 1:2 relative to the hour wheel: for every two full revolutions of the latter, the 24-hour display completes one. As the basic time display, it never stops running with the movement. If the crown is pulled out as far as possible to position 2, this part of the train is still linked to the hand-setting mechanism.

Pulling out the crown to the middle position activates the adjustable “jumping hour” mechanism, which also requires a train of its own. It includes several sophisticated features and extends from the hour wheel and hour display wheel to the switching finger on the date disc. At the same time, however, the user has to be able to move the hours and date disc located at the end of the train forwards and backwards using the crown. The tiny corrector pinion on the right meshes with the hour display wheel and initiates the process.

Normally, the hour display wheel runs freely with the rest of the movement. However, when the crown is pulled out to the middle position it turns into a form of rapid date-advance mechanism and enables the hour display wheel to be turned in either direction. The hour hand is attached to the hour display wheel pipe. The hour display wheel sits and rotates freely on the hour wheel. Connected to the hour wheel is a 12-toothed hour star with a sprung catch which rests on the hour display wheel.

The catch exerts such great pressure on the hour star that the rotation of the hour wheel is transferred to the hour display wheel. While the corrector pinion turns the hour display wheel (manually), then the swiveling hour star catch jumps over the teeth of the hour star (each tooth representing a distance of 30 degrees or one hour). The hour hand on the hour display wheel pipe is advanced, or turned back, by one hour each time. The interaction between corrector train and pinion has been calculated in such a way that the hours still literally jump into position even if the crown is turned very slowly.

Any adjustment to the hours naturally has to be transferred to the date switching mechanism. This is handled by a gear train which extends from a date reduction wheel and pinion to the date switching wheel and its finger, which is arranged in such a way that the finger moves on a computer-designed Maltese cross stopwork by one-fifth of a revolution every 24 hours.

The Maltese cross is permanently linked to a wheel with ten teeth, which advances by two teeth for every onefifth of a revolution by the cross. This, in turn, moves on the date disc, which has 62 teeth, by 2/62 or 1/31, i.e. one day forwards or backwards. The Maltese cross stopwork was chosen because it facilitates movement in both directions and requires very little force.

Crown Functions

The UTC is thus the first pilot’s watch ever to satisfy the requirements of modern aviation and this purely with a mechanical movement. No matter what other functions the owner chooses to activate – such as moving the hour hand forwards or backwards in one-hour increments to another time zone, or setting the hour hand ahead or after the current date (which also moves with the hour hand) – its 24-hour display constantly shows universal time and with it is the basis for all flying timetables.

This original watchmaking innovation, which is based on a highly sophisticated mechanism, also makes the UTC pilot’s watch the ideal travel companion. This is because the owner can set a standard time – such as the time at home – of his choice.

The 24-hour display then shows this time and the owner is continuously aware of the time of day or night at home or elsewhere. As you might expect, the UTC pilot’s watch also has the invaluable feature for protection against magnetic fields. It also comes with a screw-in crown and convex sapphire crystal and is water-resistant to 60 m.

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