The Custom A-13A Pilot Chronograph Built to Survive a Spy Plane

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You know what it’s like. You’re hanging out with one of your pals who just happens to fly a U-2 spy plane for a living. The sort of chap who spends his working day looking down on the world from 70,000 ft. Probably the sort of fellow who’s pretty bored with the “high flier” jokes already. He mentions that he’d quite like a custom-made watch that he can take up in the office. So you offer to make him one.

This is exactly the scenario that engineer and watchmaker Paolo Fanton found himself in last year. As a pilot himself, Paulo knows some of the headaches associated with wearing a watch and flying at high altitudes.

As early aviators discovered, the rarefied atmosphere around the Armstrong Line (circa 60,000 ft) is not a friendly place for either pilots or their watches. As pilots found themselves moving from (relatively) unsophisticated, low-level piston-engined planes to high-speed, jet-propelled, high-altitude aircrafts, these new high speeds and altitudes necessitated the introduction of pressurized cockpits and suits. As far as watches were concerned, with sudden changes in altitude pilots found that the crystals on their watches would pop—they’d be lifted off by the expansion of the gasses inside the watch case.Aircrafts, of course, have cockpit clocks, but pilots are notorious for wanting both belt and braces, so their backup wristwatches needed to cope. The simple solution was to have a lip on the bezel that restricted the crystal’s movement if air pressure dropped, or to fit the crystal from inside the case.

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But speaking with Paolo Fanton, one gets the sense that he rather likes trying to do things a little differently. In response to his U-2 pilot pal’s request, he decided to design a version of his A-13A watch that would survive very low pressure as well as rapid changes in pressure.


Click here for Mark McArthur-Christie’s hands-on take with the A-13A Pilot Chronograph.


He began by testing his existing A-13A Pilot Chronograph in a vacuum chamber to simulate extremely high altitude. That would make sure that any air trapped inside the case wouldn’t cause the glass to pop out or shatter. As Paolo reports, “The test went fine and the basic design showed a significant safety margin, but I thought that a fail-safe would be more appropriate for aerospace applications.” Belt and braces again.

He started looking for solutions and hit on the the idea of installing a tiny, automatic bleed valve in the side of the watch case. It would equalize the differential pressure (the difference between the pressure inside and outside the watch) as soon as it exceeds 4 kPa (0.6 psi). This is different from the helium bleed valves you’ll find on a saturation diving watch, simply because a “normal” helium valve is designed to operate at far higher pressures.

Paolo began looking for a valve to do the job. As a professional engineer, he’s pretty well-placed to know where to look, but it was a struggle. “It was very frustrating since it seemed nobody could meet my requirements. I was very close to giving up the whole project.”

But the gods—and serendipity—favor the determined. “During an oil and gas exhibition, just in front of my company’s booth, there was an aerospace company called Lee Corporation. I spotted that they made valves and had a tiny valve I thought could fit my watch.”

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Paolo explained the problem only to discover that not only did Lee have the product he was looking for, but also that they’re aviation enthusiasts. The result? A micro-valve of just 2.5 mm in diameter with a protective filter that fit perfectly into the A-13A’s stainless steel case. No matter the change in pressure—or how quickly it happens—the valve design means the case and crystal are fail-safe. Paolo had his A-13A HA (High-Altitude) ready to launch at the Armstrong Line.

Remember the pressure suit I mentioned earlier? It wouldn’t be ideal to have to hoick up the sleeve to check your watch. So for its specific mission, Paolo sourced two specifically designed straps: one 35-inch long strap fits over the sleeve of the pilot’s pressure suit, and the other has a separate 3M Velcro patch that holds the watch on the back of a pressurized glove. He’s made both straps from flame retardant material including the Kevlar threads and the velcro. The HA watch also got its own laser-engraved case back.

Late last year, the A-13A HA took flight. And as you can see, the watch was absolutely happy climbing to and descending from 70,000 ft. The valve worked just as it should and the crystal stayed in place throughout.

The practical everyday uses of an HA for most of us probably aren’t extensive, but the boasting rights for a 70,000 ft watch are significant. That doesn’t really bother Paolo. He just enjoys the engineering challenge.

Photography courtesy of Paulo Fanton.

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Mark developed a passion for watches at a young age. At 9, he was gifted an Omega Time Computer manual from a local watch maker and he finagled Rolex brochures from a local dealer. Today, residing in the Oxfordshire village of Bampton, Mark brings his technical expertise and robust watch knowledge to worn&wound.
markchristie mark_mcarthur_christie
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