Born To Fly: Testing the Sinn EZM 10 TeSTaF


The Sinn EZM 10 TeStaF has already passed rigorous German testing, certifying it as worthy of a place in the cockpit. We put it to the test again. How did it perform? Julia Knaut reports, with photos by OK-Photography. 

Most people buy pilots’ watches for their dashing, flyboy looks. But our test watch, the EZM 10 TeStaF, from the German company Sinn, has more than that: it is also a useful back-up instrument for pilots in the cockpit.

The Sinn EZM 10 TeStaF has passed strict German test procedures for pilots’ watches established in 2008 by Sinn and the Aachen University of Applied Sci- ences, in Aachen, Germany. Certification is denoted by the acronym TeStaF (“technischen standard fliegeruhren,” or “technical standards for pilots’ watches”). It guarantees that the watch can carry out the necessary timekeeping tasks for manual navigation should the cockpit instruments fail. The test is divided into three parts: functionality, resistance to external stress, and safety and compatibility with other instruments. The previous Sinn EZM 10 model was one of the first watches to receive TeStaF certification, as shown by the small airplane symbol on the dial between 7 and 8 o’clock. Sinn only had to make minor changes to the watch to gain certification: adding luminous coating to the central chronograph minutes hand and expanding the luminous surface on the chronograph seconds hand.


The design of the new model has been updated. The unadorned, bead-blasted titanium case and the black dial with large luminous elements give the watch a clean, functional look. The elongated chronograph pushers follow the outer lines of the case. The watch is designed to reflect modern tastes and to follow TeStaF standards, which specify that the case and the operating elements have no protruding edges to catch on a pilot’s equipment or cockpit instruments. The design of the watch dial also places func- tion above aesthetics. In line with the test requirements, a 24-hour display at 3 o’clock keeps the pilot in sync, while the orange subdial at 6 o’clock tracks the chronograph hours. The chronograph has two orange central minutes and seconds hands; the chronograph minutes hand is identified by its airplane-shaped tip.

The watch’s case was hardened using Sinn’s own Tegiment technology, a chemical process that makes it highly scratch resistant. The bidirectional rotating bezel is fun to use, with its cleanly ratcheting action.

An important point in TeStaF standards is ensuring daytime and nighttime legibility, which is mandatory regardless of visual conditions in the cockpit. The high-contrast dial has many luminous white and orange elements. The pilot can use the stopwatch for timing to 1⁄4 second. The running minutes scale on the count- down bezel is user friendly and highly luminous. In the dark, the chronograph’s generous markers give Christmas lights a run for their money.

If the watch actually needs to be used as an in-flight tool, the pilot must be able to operate it while wearing gloves, so Sinn gave the chronograph a grooved bezel and a large fluted crown. One minor drawback in daily operation is the lack of a quick-set date adjustment.

A grooved bezel and fluted crown enable the wearer to adjust the watch while wearing gloves.
A grooved bezel and fluted crown enable the wearer to adjust the watch while wearing gloves.

In contrast to the easy operation of the bezel and crown, the strap and the buckle seem an odd fit. The carefully finished, padded leather strap is furnished with a plain titanium buckle and a simple bent prong. While the system meets TeStaF standards for strap attachments (which require withstanding a tensile load of 200 newtons, or about 45 pounds, without damage), the clasp does not measure up to the high quality of the watch’s other components.

This does not affect the wearing comfort – you can easily adjust the padded strap and curved lugs for a comfortable fit. But the rather large crown might press against your wrist in some positions.

The simple, pronged buckle is an odd fit with the superior-quality leather strap.
The simple, pronged buckle is an odd fit with the superior-quality leather strap.

The EZM TeStaF can be used both in and out of the cockpit. The specially modified ETA 7750 provides a strong, reliable motor, which is decorated with various finishes and blued screws. Sinn has added the central chronograph minutes hand and a lubricant-free lever escapement using Diapal technology, Sinn’s friction-reducing technique of replacing the ruby pallet stones with diamonds (DIAmond PALlets).

A modified ETA 7750 is housed in a sturdy titanium case.

With regard to its rate results, the watch flies in mid-range. It gains an aver- age of 5.2 seconds per day and the greatest deviation per day between the different positions is 8 seconds. The values are somewhat better when the chronograph is running.

The TeStaF testing process is based on commonly occurring aviation-related stress factors, so the watch was tested for its resistance to environmental pressure, temperature changes, impacts, and liquids like aviation fuel. For those not sit- ting behind aircraft controls, it is good to know that the watch will not be damaged while they’re playing tennis, working at a computer or operating power tools.

Pilots’-watch fans and technology buffs will probably not be fazed by the price of $6,360 and will appreciate the bundle of Sinn technologies and the watch’s functional design. The TeStaF certificate is also a plus for potential buyers.

Manufacturer: Sinn Spezialuhren GmbH, Im Füldchen 5-7, D-60489 Frankfurt, Germany
Reference number: 950.011
Functions: Hours, minutes, seconds, chronograph with central 60-minute counter, date, 24-hour indicator
Movement: Modified ETA 7750 “Top” grade with lubricant-free escapement (Diapal technology), automatic,
28,000 vph, 34 jewels, hack mechanism, Incabloc shock absorber, Glucydur balance, Etachron regulator, power reserve = 46 hours, diameter = 30 mm, height = 7.9 mm
Case: Hardened titanium (Tegiment technology), curved sapphire crystal
with nonreflective coating on both sides, bidirectional countdown bezel, screw- down crown, anti-humidity Ar technology with guaranteed function between -45° and +80° C, fully threaded titanium caseback, low-pressure resistant, water resistant to 200 m
Strap and clasp: Calfskin strap with titanium pronged buckle
Rate results (Deviations in seconds per 24 hours, with chronograph switched off/on)
Dial up           +6 +4
Dial down      +8 +7
Crown up      +4 +5
Crown down +6  +6
Crown left      +7  +5
Crown right    0 +1
Greatest deviation of rate   8 6
Average deviation    +5.2 +4.7
Average amplitude:
Flat positions            326° 304°
Hanging positions   262° 243°
Dimensions: Diameter = 46.5 mm, height = 15.6 mm, weight = 111 g
Variations: With Tegimented titanium bracelet ($6,790)
Price: $6,360
Strap and clasp (max. 10 points): The simple pronged buckle is an odd fit with the meticulously finished leather strap. 7
Operation (5): The grooved bezel and crown make setting the time easy; the hack mechanism makes it accurate. 5
Case (10): The titanium case is sturdy, with superior finishes and solid design. Tegiment and anti-humidity Ar technologies add even more value. 10
Design (15): This technical pilots’ watch design is made more attractive with practical functions. 13
Legibility (5): Highly detailed displays reduce legibility somewhat. The dial and bezel are easy to read at night. 4
Wearing comfort (10): A padded strap and lightweight case make the watch comfortable to wear. 9
Movement (20): Sinn has modified the ETA 7750 with a central minutes counter and added an in-house lubricant-free escapement. The movement lacks a quick-set date adjustment. 14
Rate results (10): Average rate results with considerable positional differences. Great variation in amplitude 7
Overall value (15): A high price for the brand, but justified by the in-house technology, modification of a standard caliber and TeStaF certification. 13


This article first appeared in the October 2014 issue of WatchTime Magazine.

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