In this feature article from WatchTime’s upcoming May-June 2015 issue, on sale May 19, we tested the Oris Big Crown ProPilot Altimeter on a flight above the Alps. Scroll down to read more and check out original photos by Nik Schölzel and the team at Watch-Insider.com.
It’s late winter and the ground is still frozen when we arrive at the Günzburg, Germany, airport. We’re here to take the Oris Big Crown ProPilot Altimeter, our test watch, for a flight in a Cessna 182 four-seater, and we’re glad the grassy runway won’t be too soft to get enough speed for liftoff. The Oris is the world’s first automatic watch with a mechanical altimeter and we want to see how it performs in the air.
Before we prepare our plane for takeoff, we activate the Oris’s altimeter so it can display the correct altitude on its dial. First we unscrew the large crown at 4 o’clock, which allows air to reach the interior of the barometer. The watch’s altimeter works barometrically and the pressure is also dependent on weather conditions, so the crown must be pulled out and the current air pressure set in hectopascals (0.001 bar) at the red tri- angle at 6 o’clock. When the crown is unscrewed, a red ring becomes visible, reminding us that the watch is no longer water resistant to its stated level of 100 meters. The crown can also be pulled out to a second position to correct the altimeter.
We set the indicator on the dial to the altitude at the beginning of our flight, 1,460 feet. The yellow indicator shows the altitude and the red triangle shows the corresponding air pressure. Then we push the crown back into its closed position and we are ready for takeoff.
We chose the Oris model whose track measurements are shown in feet since that’s the measuring unit used in aviation. This makes it easier to compare the reading on the Oris with the one on the cockpit altimeter. Oris also makes a version of this watch whose track measurements are shown in meters, but it’s better suited for mountain climbers, skiers and other non-pilots. The Oris Big Crown ProPilot Altimeter was introduced in 2014, more than 75 years after Oris made its first pilots’ watch. We start the plane’s engine and roll to our takeoff position. During the pre-flight check we verify that the plane’s altimeter corresponds with the altimeter reading on the Oris. Then, at full throttle, we race along the grassy runway. We’re lucky to have a clear day. After takeoff we can see the Alps in the distance.
We climb to 5,000 feet. The Oris altimeter adjusts to the changing altitude more slowly than the altimeter in the cockpit. This is due mainly to the fact that the aneroid capsule in the watch’s altimeter is considerably smaller than the one in the cockpit. Yet both work according to the same principle: a sealed capsule made of thin metal is compressed by air pressure and a lever transfers the changes to an indicator hand.
The technology for the watch’s altimeter began with the aviation instrument specialty company Thommen, located in Waldenburg, Switzerland, just a few miles from Oris’s headquarters in Hölstein. You can see the aneroid capsule when you open the watch’s caseback, and the entire altimeter can be removed by loosening the three screws that hold it in place. The automatic movement lies beneath the altimeter, suspended in a ring with four spokes, one of which is thicker to encase the winding stem. The patented design shows the altitude on the outer edge of the dial.
Oris uses another patented design to protect the watch’s movement from moisture when the crown is unscrewed to activate the altimeter: a membrane made of PTFE, similar to Gore- Tex, has been inserted behind the crown opening. This allows air, but not moisture, to pass through, just like a “breathable” jacket. When the crown is screwed down, the watch is water resistant to 100 meters. The watch’s altimeter hand is also a patented design. It is made of a carbon fiber composite that is extremely lightweight and easy to move yet is shock resistant.