I once owned and then sold the Hamilton Khaki Field Auto. Regrets? I’ve had a few. So when Canada Watch House offered to send over the Khaki Aviation Converter, I was pretty excited. Hamilton has a proven reputation as a maker of solid tool watches. The Khaki Aviation Converter is no exception.

Traditional aviation watches, inspired by the German B-Uhren–and often referred to as Fliegers–have never really appealed to me. Certain brands have certainly made the most of the somewhat restrictive parameters involved in producing contemporary Fliegers. I think of brands like Sinn, Stowa, Laco and Whitby, here. But strictly speaking, Fliegers remain tied to legibility and a particular simplicity of aesthetic, that as a dive watch fan, leave me wanting something to fiddle with.

Enter the circular slide rule bezel.

Made famous by Breitling’s 1952 introduction of the Navitimer, the circular slide rule is essentially an on-board computer. And, well, it’s something to fiddle with, too.

Unlike the Flieger, there is a degree of tactical sophistication in the pilot’s aviation converter. It has the appearance of a complex dashboard instrument that you might actually find in an airplane. But in reality the bi-directional friction bezel used to operate the slide rule is deceptively simple. Seated just proud of the mid-case beneath it, the Hamilton’s bezel is cut in two finely knurled sections, making it easy to operate. It feels smooth in rotation with just the right level of tension. Being polished, it stands in contrast to the largely brushed case and lugs. The bezel finish is mirrored in the 6.5mm screw-down crown, and there is also a slim chamfer of polish running the length of the lugs.

The 316L stainless steel case comes in at 42mm in diameter, and I would say that anything smaller would reduce the legibility of the slide rule to the point of inoperability. The lug to lug width is on the longer end at 52mm, but the downward slope (which dips below the caseback) allows the watch to be comfortably seated on my 6.75 inch wrist. It is also a relatively slender watch at 11.3mm in thickness. It is water resistant to 100m.

As mentioned earlier, the watch begs comparison to Breitling’s Navitimer Automatic 41, but in one area, at least, I find that the Hamilton has an edge aesthetically, and that is the way its lugs swoop in from the 42mm case edge to a much slimmer 20mm lug width–as opposed to the 22mm of the already smaller Navitimer. I think this factor also helps to visually shrink the watch when on wrist.

The Aviation Converter employs sapphire glass on both the top and bottom of the watch. The use of sufficient AR means the beautiful sunray dial and the stainless steel edging of its applied indices are easily visible. Swiss Super-LumiNova on the hands and markers ensures that this legibility continues long past dark. Through its exhibition caseback, you can see the H10 movement vibrating away at 28 800bph. Its proprietary anti-magentic Nivachron hairspring will keep it sweeping accurately in all manner of environments, and its 80-hour power reserve means you could take it off and set it down over a long weekend and still have waiting accurately and patiently for you on the Tuesday.

The Hamilton Khaki Aviation Converter comes on a leather strap with brushed steel hardware (featured here). For $50 dollars more, you can have it on the bracelet. It is available in both blue and black dials, as well as an all-black reference, and a black and gold variant. The collection also includes a GMT and an automatic chronograph line.

---

Advertisement

---

Specs

Case	316L Stainless Steel 42mm Diameter 52mm Lug to Lug 11.3mm Thick 20mm Lug Width Screwed Exhibition Caseback Screw-down Crown Bezel: Bi-directional Friction /w Circular Slide Rule 100m Water Resistance
Dial & Crystal	Flat Sapphire Sapphire Crystal /w AR Sunray Dial Applied Indices Date @3 O’clock Super-LumiNova
Movement	H10 Calibre 25 Jewels 28 800bph 80-Hour Power Reserve
Strap	Leather Strap /w Steel Hardware  Optional: Stainless Steel Bracelet

Hamilton Khaki Aviation Converter Auto

---

Advertisement

---

Of Interest

A slide rule allows a pilot to quickly calculate any number of things, including air speed, the rate of fuel consumption, or the momentum of climb and descent. As someone who isn’t a pilot, perhaps you will never need to do any of these things. But, as it turns out (I had no idea how to use a slide rule before this watch arrived), a circular slide rule is actually useful in a wide variety of situations. You can do simple multiplication and division, or you can calculate the 18% tip on your restaurant meal (that would be the low end in Canada, btw!). You could convert kilometres into miles, or even nautical miles; how about litres into gallons, kilograms into pounds, or metres into feet?

In fact, as long as you know that the ratio of Fahrenheit to Celsius is 5/9–minus 32 on the Fahrenheit–(I learned this from A Blog To Watch), you can convert Fahrenheit into Celsius with reasonable accuracy. For example, take the temperature you know–say 72 degrees Fahrenheit–and substract 32. The answer is 40. Now spin your bezel so that the outer ring’s 5 (represented as 50 on the Hamilton) is now in line with the inner ring’s 9 (remember 5/9). Then look for 40 on the inner flange. You will see it lines up with 22.2 on the bezel. A quick Google check will show that indeed 72 Fahrenheit is equivalent to 22.2222 Celsius. Amazing, right?

Here’s another cool operation. Now, let’s say that you intend to buy your next Swiss watch. Oh, I don’t know, how about the Hamilton Khaki Aviation Converter? You know that it retails for 1075 CHF. But what if you want to know the price in Canadian dollars? Well, the exchange rate is 1.38 (or 1.4 for simplicity’s sake). You spin the bezel so that the 14 on the outer dial lines up with 10 on the inner flange. Now look for 10.75 on the inner flange. It aligns approximately with 15 on the bezel. The price of your Hamilton, then, in Canadian dollars, is roughly $1500. In fact, at Canada Watch House, you will find it or $1475. What a steal!

Quibbles

Some might say the Hamilton Khaki Aviation Converter is a little too similar to Breitling’s Navitimer Automatic 41. But I would counter that as is the case with B-Uhren Fliegers, if you want to make a pilot watch with a circular slide rule, there is not much room within the functional requirements of the design for variation. The Breitling has an edge in the legibility of its slide rule bezel and flange, but the cleanliness of the Hamilton’s inner dial carries the day. Where I do have a small quibble is with the strap. Its colour, its build quality, and its hardware are top notch. My niggle is with the faux alligator embossing. I would rather see a true ostrich pattern, a rivet, or a rally. Perhaps something distressed would work, as well. Certainly not a deal breaker.

Final Thoughts

Though I have made much of the comparison between the Aviation Converter and the Navitimer here, it would only be fair to point out that Hamilton’s history with aviation and pilot watches is also a storied one. In 1918, the first Hamilton aeronautical watch aided US Airmail pilots servicing between Washington, D.C. and New York City. A Hamilton also accompanied pilots on the very first flight from California to Hawaii in 1927. By the 1930s, Hamilton had even become the official watch of four major American commercial airlines in the United States. Today you can find Hamilton pilot watches on the wrists of Air Zermatt rescue workers, and as the sponsor of the Red Bull Air Race and the Swiss Aerobatic Association. In fact, other than brand loyalty–or that you might need a watch equipped with a COSC certified movement–I find it hard to justify the price difference between largely similar watches. You could purchase four Khaki Aviation Converters for the price of a single Navitimer, and still have enough left over for a new strap.

Hamilton have managed to bring a sense of casual elegance to the Khaki Aviation Converter that put it in the running as a GADA–or go anywhere, do anything–daily wearer. It is slim enough to be worn under a cuff and tough enough (with its anti-magnetic hairspring and 100m of water resistance) to take part in any manner of manual labours or activities. It comes with a tried and true Swiss movement from a heritage brand with a history in aviation, worldwide customer service, and a myriad of authorized dealers where you can “try before you buy.” To boot, even I have to admit that the slide rule is more useful and functional than a dive bezel. So it’s a tool watch you might use in the manner for which it was actually designed. Crazy, right?

The Hamilton Khaki Aviation Converter Auto retails from $1095USD(on leather) to $1145USD (on the bracelet). For more information, please visit the brand website or a reputable authorized dealer.

Thank you to Canada Watch House or providing the review watch.

---

About the author

Brent Robillard is a writer, educator, craftsman, and watch enthusiast. He is the author of four novels. You can follow him on Instagram.

---

Off The Cuff articles are full-length, hands-on reviews of the watch in question and represent the opinion of the author only. All photos are original, unless specified otherwise. If you would like to have your watch reviewed on this site, contact us here.

Please understand that using any links to products on this site might result in us making money.