The UTC Pilot's Watch from IWC

The following pages are from an IWC special catalogue issued on the release of the UTC pilot's watch. The remainder of the catalogue contains information about the other pilot watches available at the time plus some history.

The catalogue is not dated and has the IWC reference number WA 0311.

The UTC pilot's watch: moving from time past into time future without losing sight of the here-and-now.

In 1884, the lack of orientation that had plagued the world since the beginning of international travel was finally put to an end. For it was then that the major seafaring nations all 27 of them - convened for the Washington Meridian Conference and came to an agreement about how to impose some form of order on the world. The meridian running through Greenwich was henceforth to be known as 0' longitude. At the same conference, the participants decided to create time zones, or areas with the same time of day. The time at the zero meridian was named Greenwich Mean Time, or GMT, and was based on astronomical observations. Starting with GMT, the time zones change by one hour for every fifteen degrees of longitude. As we move west of GMT the time is minus, and to the east plus. There are a total of 24 different time zones. The 180^o longitude line, directly opposite the zero meridian, has since been known as the International Date Line. If we cross this line in an easterly direction, we move back into yesterday. If we cross it travelling west, we jump forward into tomorrow. GMT, which is astronomically determined, was replaced by an atomic time scale known as Universal Time Coordinated or UTC for short - in 1972. All flight schedules for international aviation purposes are coordinated according to UTC.

All in all, then, everything should be as clear as day. The flight schedules are synchronized and the time zones clearly delimited. But is it really all as simple as that? Perhaps the best way of finding out is simply to take off and see what happens. So let's climb aboard a Concorde in Paris, departing at 13.00 hours for Rio de Janeiro. At supersonic speed we fly the 9,000 kilometres in around six hours, arriving in Rio at 15.00 hours local time. All we need to do now is put our watches back by four hours. However, this isn't the end of our journey. We've decided to fly on to the Tonga Islands in the South Pacific and then back to Paris via the same route. On the return journey we cross the International Date Line from west to east, which means putting the date back. And that presents us with a small but tricky problem. Because on most watches we cannot simply turn back the date. And if, after crossing several time zones, we suddenly decide we need to know the time back home, we need to be pretty adept at mental arithmetic.
 

With the UTC pilot's watch, keeping track of time is child's play.

The UTC pilot's watch from IWC finally solves the problems created by flying to and fro around the globe. The watch is a mechanical work of art that actually remembers and displays the time back home while keeping track of the time as we move from one time zone to another: forwards, back wards, to the east and west, over the International Date Line and back again. The UTC pilot's watch is a pilot's watch in the great IWC tradition. Precise and robust with the classical characteristics that set IWC pilot's watches apart: a black dial, Arabic numerals with luminous hour markers, luminous hands and even the tell-tale luminous triangle at the 12 o'clock position. The watch shows the hours, minutes, seconds and date, but also features a 24-hour display in an arched window below the 12. But even more crucial is the way the watch handles this special feature. When the crown is pulled out to its central position, the hour hand and only the hour hand - can be wound forwards or backwards in one-hour steps. If in the process it jumps past midnight, the date also advances automatically to the next day. If we turn the hour hand back to the previous day, the date too moves back at midnight. However, the 24-hour display in the window remains totally unaffected by these movements, and retains the time set for home or, in the case of UTC, Universal Time Coordinated. This feature makes the UTC pilot's watch the first truly time zone-compatible watch ever a timepiece that will fully meet the needs of even the most demanding professionals.
 

The UTC pilot's watch shows the time all over the global village.

Features

- Mechanical 37526 calibre movement
- Self-winding
- 24-hour display (UTC = Universal Time Coordinated)
- Hour hand adjustable in one-hour steps (TZC = Time Zone Corrector)
- Date display
- Centre seconds with stop function
- Inner case made of antimagnetic soft iron
- Screw-in crown
- Water-resistant to 60 m
- Sapphire glass, secured against displacement by drop in air pressure

The ingenious mechanism inside the UTC pilot's watch

To understand the basics of the UTC mechanism we need to know that the rotations provided by a wheel - the minute wheel to be precise - in the movement are converted into coordinated revolutions of the minute and hand hours by a train of cogs located under the dial and known as the motion work. 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 motion work 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.

Reduction for the 24-hour display.

For the UTC pilot's watch, IWC had to develop two completely new gear trains, starting at the hour wheel. Let us begin by looking at 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) by a ratio of 2:1 relative to the hour wheel: for every two full revolutions of the latter, the 24-hour display completes one. As the basic time display, this never stops running with the movement. If the crown is pulled out as far as possible, this part of the train is still linked to the hand-setting mechanism.

The hour hand jumps forwards and backwards.

Pulling out the crown to its middle position activates the adjustable "jumping hour" mechanism, which also requires a train of its own. This has 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 - at the end of the train - forwards and backwards using the crown. The tiny corrector pinion 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 its middle position, the hour display wheel can 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 (see exploded diagram).

The hours never fail to jump.

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 swivelling hour star catch slides 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.

Finally, the date.

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 one-fifth 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.

Greg Steer - October 2002

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