Monochrome Watches
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The New Hamilton Khaki Aviation Converter Collection (Review, Live Pics & Price)

A collection of instrumental pilot's watches with solid content, and accessible prices.

| By Brice Goulard | 11 min read |
2020 Hamilton Khaki Aviation Converter Collection - review

Hamilton is no stranger to the instrument watch. In fact, the brand owns multiple collections designed to remind its glorious past as one of the major providers of timepieces for military forces and watches for a specific purpose. This is true, for instance, with the military-inspired Khaki Field watches, a tribute to its mid-20thcentury archives (the Hamilton “Hacked”). Hamilton is no stranger to the pilot’s watch either. With its Khaki Aviation collection, the brand demonstrates its experience in this field. The best example was the recent Khaki Pilot Pioneer. Today, it’s another kind of pilot’s watch that the brand introduces. Meet the brand new Hamilton Khaki Aviation Converter Collection.

Hamilton is proud to own over 100 years of experience in the field of pilot’s watches. The brand, for instance, provided the first U.S. Airmail service with watches, as of 1918. Today, Hamilton is still involved in pilot’s watches with the Khaki Aviation collection, which comprises, for instance, the X-Wind watches – highly technical, modern pieces supplied to air racers. Today’s watch isn’t a vintage re-edition. It isn’t an ultra-modern, technical piece either. The Hamilton Khaki Aviation Converter Collection is a classic pilot’s watch that enables flying calculations to be performed on the wrist, with a so-called “slide rule”.

Hamilton Khaki Aviation Converter Auto Chrono H76726530

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There are multiple ways of seeing the pilot’s watch. As we’ve explained in this technical article, showing the key features of pilot’s watches, this is a pretty large definition. The most common style of pilot’s watches are those created for military purposes, mostly during WWII. On one side are the observation watches – the B-Uhr. On the other side are the chronographs, often equipped with flyback movements and rotating bezels – the French Type 20 or the German Fliegers. But once the war was over, civilian aeronautics emerged quickly and alongside this, the need for purpose-built watches. This gave birth, in the early 1950s, to some of the most iconic models, such as the GMT-Master on one side and the Navitimer and other watches with flight computers on the other. The new Khaki Aviation Converter sits in the latter category. But before we look at the 3 different models in this collection, let’s explore the common features – and mostly the bezel.

The “slide rule” bezel

The most striking element of the Hamilton Khaki Aviation Converter is its bezel, which is found on all 3 versions. It is a so-called “slide rule” or “flight computer” or “logarithmic bezel”. Behind these complex names hide an extremely clever device that enables mathematical calculations while in flight. These bezels were first integrated into wristwatches in the early 1940s – to be precise, in 1940, with MIMO watch manufacture and Breitling almost simultaneously filling a patent, respectively in July 1940 (Swiss patent 216 202) and August 1940 (Swiss patent 217 012).

An example of MIMO Loga “Brevet 216 202” with a logarithmic scale, possibly the first wristwatch with a slide rule (1940) – source

What is a slide rule? It is a mechanical analogue computer, used to primarily perform multiplication and division but also functions such as exponents, roots or logarithms. Why pilots needed those? While today’s aviation is performed with the help of navigation and modern avionics, back in the 1940s and 1950s, pilots needed tools such as a slide rule and a watch to perform calculations, in order to track speed, fuel consumption, distance, rate of climb or descent and flight time. This was done with the help of a pilot’s well-known device, the E6B “Whiz Wheel” – a paper flight computer that’s still used widely in pilot training today.

An E6B flight computer commonly used by student pilots. These flight computers are used during flight planning (on the ground before takeoff) to aid in calculating fuel burn, wind correction, time en route, and other items. In the air, the flight computer can be used to calculate ground speed, estimated fuel burn and updated estimated time of arrival. source: Wikimedia

With the integration of the slide rule on watches, pilots had the ability to perform both timings and calculations on a single device. And the Hamilton Khaki Aviation Converter has a bezel that has been modelled after the famous E6B. The bezel is bi-directional and its logarithmic gradations interact with the fixed scale around the dial. As such, once you have understood the user manual (not the easiest, as trained pilots could tell), you’ll get the ability to calculate distances, speeds and fuel consumptions, but also to carry out various unit conversions, such as kilometres/nautical miles, pounds/kilograms, feet/meters for instance, or currency conversions for those flying internationally.

Hamilton Khaki Aviation Converter Auto Chrono H76726530

Hamilton Khaki Aviation Converter Auto Chrono H76726530

On the Hamilton Khaki Aviation Converter, whatever the model in the collection, the “slide rule” bezel’s insert is made of K1 mineral glass (hardened glass with scratch-resistant coating) with graduations printed underneath, allowing for great contrast and good protection against scratches. The steel bezel is deeply notched on the side, allowing to be easily manipulated, even with gloves.

The Khaki Aviation Converter, Common traits

As said, the new Khaki Aviation Converter isn’t a re-edition of a past model but a true novelty for Hamilton, launched as a whole collection of 3 different models, with 7 references. The main difference between these 3 models is the complications and movements, the overall design being shared over the collection.

The watch has definitely a classic feel. It isn’t entirely vintage nor hyper-modern, it has a certain timeless appeal that is both pleasant and reassuring. It is the kind of watch that looks great now and that certainly won’t feel outdated in 10 years from now.

Hamilton Khaki Aviation Converter Auto H76615530

The design starts with a robust case – 42mm or 44mm depending on the movement – with an instrumental feel, as most of the surfaces have a satin-brushed finish. Yet some details, like the polished pushers or the polished bevel on the side of the lugs, add to the perceived quality and give a more “civilian” look to the watch. With its slide rule bezel, its large and deeply notched crown and its solid shoulders, the Aviation Converter is, without doubt, to be seen as a toolish pilot’s watch.

All three models share the same design for the dial too, with old-fashioned hands and applied indexes. Both are largely filled with Super-LumiNova for very decent nighttime legibility and the dial, executed in sunray-brushed black or blue, provide great contrast in daylight condition. On top of the watch sits a flat sapphire crystal with a highly effective double anti-reflective coating. Another sapphire crystal sits on the caseback. All the watches are rated to 100m water-resistance – which is rare on pilot’s watches with a slide rule bezel.

Hamilton Khaki Aviation Converter Auto Chrono H76726130

All 3 versions of the Hamilton Khaki Aviation Converter – time-and-date, GMT and Chronograph – are equipped with Hamilton’s latest automatic movements, basically ETA base with upgraded power reserve and kinetic chains. The 3-hand includes a balance spring made of Nivachron alloy, and the chronograph features a silicon balance spring, both with anti-magnetic properties. Certainly an important feature for a pilot’s watch, cockpits being magnetic environments, these anti-magnetic parts will be helpful in our daily lives, as we are surrounded by magnets – and magnetized movements are the main reason why watches are sent to service centres.

Finally, all 3 versions are available either on a brown calfskin leather strap with alligator pattern (with pin buckle) or with a stainless steel bracelet (with folding clasp). And with prices ranging from EUR 1,095 (3-hand on leather) to EUR 2,045 (chrono on steel), it once again confirms Hamilton’s ability to bring excellent value for the money.

Hamilton Khaki Aviation Converter Auto Chrono

The first of the 3 models in the Khaki Aviation Converter collection is a classic chronograph – a complication that makes full sense in this pilot’s context, as extremely helpful in combination with the slide rule bezel, to perform calculations over short (or longer) periods of time. This Auto Chrono version is available only with a black dial and in stainless steel, with the option of a dark brown leather strap or a stainless steel bracelet.

Hamilton Khaki Aviation Converter Auto Chrono H76726530

The dial of this chrono Aviation Converter is the most striking of all three models. It combines a black sunburst background with nice details, such as the chronograph sub-counters that are circled by a metallic frame and decorated with a gradient pattern – in dark grey, with the centre of the sub-dials being lighter. The small seconds, positioned at 9 o’clock, is more discreetly implemented. This version is equipped with a day-date feature, another signature element of the Valjoux-based movements.

The case of this Chrono version measures 44mm and about 15mm in height. It is a watch with great presence on the wrist but that remains comfortable thanks to short, curved lugs. The pushers and the crown are polished, for an extra luxurious touch.

Hamilton Khaki Aviation Converter Auto Chrono H76726530

Powering the Aviation Converter Auto Chrono is the Calibre Hamilton H-21 Si, an improved take on the Valjoux 7750 cam-operated movement. In short, the entire kinematic chain has been refined, from the barrel to the escapement, the mainspring has been improved to increase the power reserve from 42 hours to now 60 hours, but the frequency has been kept at 4Hz. Also, this watch is the first of the serially-produced Hamilton chronographs to feature an anti-magnetic silicon balance spring (it was used previously once on a COSC-certified limited edition). The movement is visible thourhg the caseback with a specific decoration (repetitive pattern on the main bridge).

Specs: 44mm diameter – stainless steel case, brushed with polished accents – sapphire crystal with double A/R coating – bi-directional black “slide rule” bezel with K1 mineral glass insert – 100m water-resistant – Calibre Hamilton H-21 Si, automatic chronograph with day-date – 60h power reserve, 4Hz frequency, 25 jewels, silicon balance spring – leather strap ref. H76726530 priced at EUR 1,995 or USD 1,845 – steel bracelet ref. H76726130 priced at EUR 2,045 or USD 1,895

Hamilton Khaki Aviation Converter GMT Auto

The second model in this Hamilton Khaki Aviation Converter collection is an automatic GMT watch, another favourite complication for pilots, especially civilian pilots crossing borders during longer flights. The Converter GMT is also differentiated from the two other models by its blue sunburst dial and blue bezel’s insert. As such, it is the most elegant and contemporary edition in this new collection.

Hamilton Khaki Aviation Converter GMT Auto Blue H76715140

This Converter GMT is housed in a 44mm case, equally finished and shaped as the chronograph, yet with a slimmer profile. The dial is also cleaner, with just the addition of a 24-hour scale next to the hour markers. This scale is linked to a central, red-tipped GMT hand, which can be adjusted by the crown by one-hour increments. The watch is powered by the Caliber H-14, the GMT version of the calibre H-10, with a 3Hz frequency, upgraded gear train and more powerful mainspring, allowing for a very comfortable 80-hour power reserve (double of a standard ETA movement). A date is positioned at 6 o’clock and adorned with a metallic frame.

The Hamilton Khaki Aviation Converter GMT Auto is available either on a light brown leather strap or on a stainless steel bracelet.

Specs: 44mm diameter – stainless steel case, brushed with polished accents – sapphire crystal with double A/R coating – bi-directional blue “slide rule” bezel with K1 mineral glass insert – 100m water-resistant – Calibre Hamilton H-14, automatic GMT with date – 80h power reserve, 3Hz frequency – leather strap ref. H76715540 priced at EUR 1,445 or USD 1,295 – steel bracelet ref. H76715140 priced at EUR 2,495 or USD 1,345

Hamilton Khaki Aviation Converter Auto

Last but not least, the third watch in the Khaki Aviation Converter collection is a more simple Auto time-and-date model, however still presenting the same features as the other 2 versions, including the same “slide rule” bezel. Compared to the rest of the collection, this Converter Auto is presented in a slightly smaller case of 42mm, allowing for a nice comfort on the wrist. The case remains equally finished and shaped, with polished bevels and deeply notched crown.

Hamilton Khaki Aviation Converter Auto H76615530

In addition to the two classic stainless steel versions with black dial – on leather strap or steel bracelet – the Khaki Aviation Converter Auto is available in a third edition with a black PVD-coated case, giving this model a striking appearance.

Hamilton Khaki Aviation Converter Auto black PVD H76625530

This time-and-date version is equipped with the Hamilton Caliber H-10, an upgraded version of the ETA 2824-2. The gear train and kinetic chain have been upgraded, the frequency lowered to 3Hz and the mainspring reinforced, resulting in a 80-hour power reserve. It now features a balance spring made of Nivachron alloy, with anti-magnetic properties. As explained by Hamilton “In the cockpit, having a watch unaffected by magnetic forces is critical, and by adding this superior balance spring alloy, we ensure precision in any environment. Military pilots’ watches were the first to include anti-magnetic technology that countered the fields generated by radar instruments.

Hamilton Khaki Aviation Converter Auto black PVD H76625530

Specs: 42mm diameter – stainless steel case or PVD-coated stainless steel case, brushed with polished accents – sapphire crystal with double A/R coating – bi-directional black “slide rule” bezel with K1 mineral glass insert – 100m water-resistant – Calibre Hamilton H-10, automatic with date – 80h power reserve, 3Hz frequency, 25 jewels, Nivachron balance spring – steel on leather strap ref. H76615530 priced at EUR 1,095 or USD 995 – steel on steel bracelet ref. H76615130 priced at EUR 1,145 or USD 1,045 – Black PVD on leather ref. H76625530 priced at EUR 1,195 or USD 1,095

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3 responses

  1. At first I though: that’s my summer (or sailing) watch!! 42mm, 100m, nice, nice , nice,
    …. then I zoomed in, and noticed that quite large spacing between the two logarithmic scales: uhmmm … it’s like having a chrono with no, or interrupted, second scale. For me this represents a basic flaw in the design concept.
    I know, for precise calculation there are other means, but still…
    I’ll try to see it in metal.
    Have a nice day,

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