Stop looking at the circular slide rule bezel on your pilot’s watch and actually use it!
Those not so well-acquainted with the pilot’s watch may be forgiven for thinking that bezels are only functional on a dive watch or sports watch. In actual fact, they have long been used as an integral feature of an aviation watch and are multifunctional. Similar to how the moon orbits the earth, the term bezel is a French word that means little moon.
Depending on your budget, you’ll likely come across several bezel types on a watch. While those on a dress watch are fixed and usually unadorned – save for those versions with diamond decoration – and sports watches feature unidirectional rotating bezels with a 60-minute countdown scale, on a pilot’s watch, a bezel can be a relatively complex feature. But don’t let the complicated-looking slide rule bezel put you off. Once you know how to use one, it can be an incredibly helpful and fun Easter egg to play around with – not all of us fly aircraft!
What is a slide rule bezel?
Adding a bezel to a watch is a very clever way of implementing additional features into a timepiece without having to swap or modify the movement inside. A dive watch bezel, for example, is often unidirectionally rotating. This means it will only move in the counter-clockwise direction to eradicate the risk of accidentally extending dive time whilst you’re underwater. This way, your remaining dive time can only ever be shortened, so you’ll never accidentally run out of oxygen or misjudge a decompression stop.
Slide rule bezels are not limited to use in the cockpit exclusively. Any luxury watch collector can enjoy this feature, too!
Still, the slide rule bezel is the most intricate-looking of all. It can be used to convert kilometers to miles or to calculate things like fuel consumption, and the duration of a flight based on remaining fuel. It can also perform simple division and multiplication tasks and calculate speed based on distance. So, there is much more to a circular slide rule bezel than meets the eye. They are a valuable aid for working out quick calculations on the fly, but more importantly, they are not limited to use in the cockpit exclusively. Any luxury watch collector can enjoy this feature, too!
Using the slide rule bezel
What makes the slide rule bezel so innovative and easy to use is the beautiful format of its inner and outer scales that work synergistically with one another. Not only are they designed to be incredibly legible, but you can easily use them to convert units of measurement by aligning your unit and value on one scale and reading off from the other. You can use the bezel in this way for things like converting kilometers to miles or vice versa. If you’re only just starting to learn about the slide rule bezel, a video tutorial may help, but here are a few examples of how it can be used to carry out air-bound calculations, as well as tasks on the ground.
You can use the slide rule bezel for calculating speed based on distance or to convert kilometers to miles, for example. Whether you’re navigating an aircraft or enjoying a spot of motorsport racing, simply align the speed you’re travelling at – in the correct units – on the outer scale with the distance you require, then, read the estimated time given on the inner scale.
This is how the conversion of distances works
Simple calculations with the slide rule bezel
For calculating fuel consumption, all you need to know is your fuel consumption rate and your speed. You simply locate the speed value of your vehicle or aircraft on the outer scale – to do this, you’ll need to use the multiplier of 10 feature on the scale. For example, if your plane is moving at 150 miles, you would select 15 from the outer scale and 10 on the inner: 15 x 10 = 150. Then, find your fuel consumption rate on the inner scale. You can then read your desired fuel consumption rate given the duration you have selected. For a further three hours of travel, for example, you would choose the 3 on the inner scale to multiply your reading by 3.
You can use the slide rule bezel on a pilot’s watch for simple mathematics, too. Basic multiplication and division are easy to calculate. To multiply or divide using two numbers as you would see in a written sum, you simply align one number on the outer scale and one number on the inner. Depending on whether you’re multiplying or dividing, the answer to your equation can be read from the outer or inner scale.
This is how to multiply two numbers
And that’s the slide rule bezel!
You wouldn’t believe the number of watch collectors out there who own a watch with a GMT complication or a slide rule bezel and simply don’t know how to use it! If you thought you had to be a pilot to enjoy the added benefit of this feature you were wrong! This pilot bezel is fun for the gadget-loving type and serves as a quirky, fun tool for anyone to use on a daily. Instead of admiring the look of a slide rule bezel from a distance, give these calculations a go and enjoy telling your friends how your watch actually works!
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The most important manufacturers of pilot’s watches with and without bezels at a glance
