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  • How a NaBo 17 ZM survived a Tornado crash

Historic cockpit clock provides design inspiration for 717 model

16 April 1980 was a Wednesday that will forever be remembered in the history of German military aviation. It was on this historic day that a Panavia PA-200 (P04 prototype) combat aircraft – better known as a ‘Tornado’ – crashed on German soil for the first time. Both test pilots working for the company Messerschmitt-Bölkow-Blom died in this tragic accident in Geiselhöring in the district of Straubing.

Sinn NaBo 17 ZM in the Tornado

At the time, the Tornado – a twin-seat multirole combat aircraft – was being used by the German, British, Italian and Saudi Arabian armed forces as a fighter-bomber, interceptor and reconnaissance aircraft. Following the first flight on 14 August 1974 at Manching, series production of 992 planes ran between 1979 and 1998. The German armed forces still haven’t announced the final date for withdrawing this reliable multirole combat aircraft, with 85 of them still in service as it stands. What’s really interesting is that these twin-engine jets with swing wings were equipped with two NaBo 17 ZM navigation cockpit clocks – one for the pilot and the other for the weapon systems officer. And these timepieces were supplied by Frankfurt-based watchmaker Sinn. This type of cockpit clock is still used by the military today in Tornado aircraft. The NaBo 17 model made by Sinn was also used in the F-104 Starfighter, the Breguet Atlantic – a long-range maritime patrol aircraft – and military helicopters such as the Bölkow Bo 105.
The Tornado featured two NaBo 17 ZM cockpit clocks made by Sinn one for the pilot and one for the weapon systems officer.
Cockpit clock with central minute counter
Technical drawing of the NaBo 17 ZM from 1977.
Cockpit clock with central minute counter

The German Federal Office for Defence Technology and Procurement (BWB) chose the Sinn NaBo 17 ZM for purely practical reasons. Frankfurt-based Sinn was the only manufacturer to add a central minute counter (the ZM in the model name) to its cockpit clocks. This extra feature made life easier for both the pilot and the weapon systems officer, who could quickly and easily read off stop times during a flight. Plus, the clock was designed to meet the practical requirements of the job to perfection in terms of its functionality, design and readability. Additional special features of these clocks included the start and reset buttons at the bottom of the case, as well as the orange hands of the chronograph’s central stopwatch display for seconds and minutes.

Investigation by lieutenant colonel Volkart Rothweiler

It’s at this point in the story that retired lieutenant colonel Volkart Rothweiler comes onto the scene. During the 1960s and 1970s, the soldier was a pilot of the Lockheed F-104 Starfighter multirole combat aircraft. With an unbelievable 269 crashes in total in this aircraft leaving 116 pilots dead, the German armed forces had no choice but to turn their attention to flight safety. Due to his in-depth training, exceptional flying skills and extensive experience, especially with the Starfighter, lieutenant colonel Volkart Rothweiler was sent off on the relevant training (in the USA and elsewhere). Following on from this work, he was appointed as the chair of the trinational committee tasked with investigating the Tornado crash of 16 April 1980 by the Flight Safety General in 1980. And his meticulous investigation revealed something quite astonishing... The pilot’s NaBo 17 ZM had survived the horrific crash largely unscathed and was still working perfectly.
Respect and appreciation for the historic NaBo
The old uniform of the pilot who was later commissioned by the German Air Force and aviation industry to investigate flight safety, retired lieutenant colonel Volkart Rothweiler. He was the one who told Lothar Schmidt the incredible story of the NaBo 17 ZM. And that was how Sinn Spezialuhren ended up with the clock and other items that had once belonged to the retired lieutenant colonel.
Respect and appreciation for the historic NaBo

Much later, at the age of 84, retired lieutenant colonel Volkart Rothweiler came across this indestructible NaBo 17 ZM when he was looking back through the things he had saved over the years. What should he do with such a historic clock? Nobody in his family showed any interest in flying. And yet retired lieutenant colonel Volkart Rothweiler wanted to show his own respect and appreciation for this special timepiece by making sure it ended up in the right hands. Having thought about it long and hard, Sinn Spezialuhren seemed the obvious choice. He wrote to Lothar Schmidt, owner of Sinn Spezialuhren, and told him the unbelievable story in a letter. And that’s how the unscathed NaBo 17 ZM made its way to Frankfurt am Main along with some of the retired lieutenant colonel’s other belongings, including his uniform, model airplanes and a navigation book for the unit’s route from Memmingen/Allgäu to Decimomannu/ Sardinia (with a 90-minute flight time).

From TESTAF to DIN 8330: pilot watch expertise

Anyone who’s familiar with the story behind Sinn Spezialuhren will already be aware that our company was known for its wristwatches for pilots and cockpit clocks for civil and military aviation back in the 1960s. Our extensive expertise in pilot watches is what connects our present to our past. After all, it was always our goal to define the term ‘pilot watch’ and the associated functional requirements more clearly while developing pilot chronographs in the traditional sense.
We managed this for the first time in 2012, when we revealed the first watches with certification in line with the technical standard for pilot watches (TESTAF) initiated by us and developed by the Department of Aerospace Technology at Aachen University of Applied Sciences.The real breakthrough didn’t come until 2016, though. For the first time in decades, the German Institute for Standardisation (DIN) published a new German timepiece standard based on the TESTAF standard: DIN 8330 ‘Timekeeping technology – pilot watches’.The main reason for developing DIN 8330 was to define a DIN pilot watch that can fully replace the prescribed instruments for time measurement in an aircraft in case of emergency. For additional context, a cockpit clock malfunction can restrict in-flight operations and even cause significant financial losses. With this in mind, DIN 8330 – similar to DIN 8306 for diver’s watches – sets out the requirements and testing criteria for functionally demanding, safe and reliable pilot watches. Building on TESTAF, DIN 8330 also widens the pool of certifiable watches and features more stringent test criteria for  readability, vibration stresses and resistance to liquids commonly found in aircraft.

The design and style of the NaBo 17 ZM provided the inspiration for the 717 model.

Inspiration for 717 model

The NaBo 17 ZM played an important role in the early days of Sinn Spezialuhren and it also provided the design inspiration for the 717 model. This cockpit wristwatch is the perfect proof that the Sinn Spezialuhren brand has always stayed true to its roots. The 717 model also features a central stopwatch display for seconds and minutes in the form of large orange hands, which is created using the time-honoured SINN chronograph movement SZ01. The case houses an interior pilot’s bezel, which can be smoothly operated from the outer diameter of the watch. In keeping with its predecessor, the dial is distinguished by its excellent readability, even in the dark, and, thanks to the sapphire crystal glass with anti-reflective coating on both sides, under adverse lighting conditions too.

iF Design Award and German Design Award

The 717 model was awarded two prestigious prizes in 2022. This is the first ever Sinn watch to have been recognised with the acclaimed iF Design Award. The iF Design Award has been one of the world’s most celebrated names in terms of outstanding design since 1954. It is presented by the world’s oldest independent design institution, iF International Forum Design GmbH. The 717 was named a winner in the ‘Excellent Product Design’ category at the German Design Award. The judging panel explained their choice: “The 717 cockpit wristwatch combines the functions of the historical NaBo 17 ZM navigation cockpit clock with the wearer comfort of a sporty wristwatch. With its deep black case and matching sports strap, the 717 model has a timelessly elegant and extraordinarily high-quality design.”

“This fascinating and exclusive timepiece ever so stylishly links the past with the future and perfectly embodies our Sinn Spezialuhren brand’s DNA down to the last detail.”
The cockpit wristwatch won the ‘iF Design Award’ and the ‘German Design Award’ in 2022.
“This fascinating and exclusive timepiece ever so stylishly links the past with the future and perfectly embodies our Sinn Spezialuhren brand’s DNA down to the last detail.”

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