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Why Some Pilot Watches Have a Slide Rule

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An appreciation of watches often takes you back in history. That is especially the case when you find yourself asking "what is that for?" A commonly misunderstood feature on some pilot watches is the slide rule bezel. This feature was made popular by Breitling in the 1950s when they released the Navitimer collection. 2012 is the 60th anniversary of the Navitimer, and it remains one of the brand's top selling timepieces today.

Around the periphery of the Navitimer is a rotating bezel that contains a functional circular slide rule - a calculation tool that existed in a pre-electronic calculator world. The particular slide rule that Breitling uses contained features making a host of pilot-appropriate calculations possible. These include metric to standard conversions, fuel consumption, air speed and distance calculations, and more. The only catch is that you need to know how to use it.

In today's world very few people are familiar with what a slide rule is or how it works. True enough, it is a bit more complicated than simply punching some numbers in a digital calculator. Though a slide rule never needs any batteries. It was my guess that Breitling retained the feature on the Navitimer and some other watches because it looked neat and was a fascinating historical vestige. I was wrong. Turns out that even today many pilots are taught how to use a slide rule bezel in flight school - both civilian and military. So it would seem that this feature still does have some use.

To discuss this topic a bit more I was lucky enough to speak with famous retired Navy pilot and US astronaut Mark Kelly. I was trying to determine whether most pilots were familiar with this tool, and if they were used very often. Kelly happens to be a rather dedicated Breitling watch lover, and has a long history with precision tools and machines. He mentioned to me that in pilot school he did in fact learn how to use a slide rule and watch bezel slide rule. Not only that, but he said that he would frequently use his watch to perform some of the calculations slide rule bezels were designed for when he was a Navy pilot. It turns out that the Navitimer watch isn't just a piece of history that is still sold today. This information was later confirmed when interviewing other pilots as well.

Breitling knows that most people don't know how to use a slide rule bezel - even many pilots. They have a dedicated slide rule tutorial on their website for those eager to learn about this semi-archaic piece of computational technology. Though strictly speaking, you don't need to know how to use it if you want to own a Breitling Navitimer, or other watch that has a slide rule bezel feature.

The newest Bretiling Navitimer models are the 01 pieces with in-house made Breitling automatic chronograph movements. They are 43mm wide and come in steel or gold cases. The above model seen in this article is actually a limited edition "Navitimer Blue Sky" watch made for the 60th anniversary of the collection and is limited to 500 pieces in steel. Instrumental by nature, the Navitimer collection is one of the original "tool watches," which continues to find appeal today. The recent lesson for this watch lover was that the principle feature of the Navitimer isn't something that is merely left to history.

Ariel Adams publishes the watch review site aBlogtoWatch.