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Tachymeter watches


Tachymeter scale - why and how?

The tachymeter scale is based on the formula: Speed = distance / time. The scale was developed so that it performs this calculation automatically when the stopwatch function of the watch is used.

The speed displayed in the airplane rarely corresponds to the speed over ground flown. With a tachymeter scale, a pilot can determine his speed based on a known distance. To do this, he stops the time he needs to cover a distance of 1 km, for example.

If the pointer is at 100 on the tachymeter scale after covering the kilometer, for example, the pilot knows that he is currently flying at 100 km/h over ground.

Knowing your exact speed over ground can be important if, for example, you want to reach an airfield in a headwind and need to pay attention to the amount of fuel in the tank. If I still have an hour's worth of fuel left in the tank and know that I am flying at 100 km/h, the destination airfield may only be a maximum of 50 km away. For safety reasons, you must still have half an hour's worth of fuel left in the tank when you land.

Tachymeter scale - why and how?

Time, distance, speed

The tachymeter scale is based on the formula: Speed = distance / time. The scale was designed to perform this calculation automatically when using the stopwatch function of the watch.
Speed
Due to the wind, the speed displayed in an airplane rarely corresponds to the speed over ground. With a tachymeter scale, a pilot can determine his speed on the basis of a known distance. To do this, he stops the time he needs to cover a distance of 1 km, for example. If the pointer is at 100 on the tachymeter scale after covering the kilometer, for example, the pilot knows that he is currently flying at 100 km/h over ground.
Time
Knowing your exact speed over ground can be important if, for example, you want to reach an airfield in a headwind and need to pay attention to the amount of fuel in your tank. If I still have an hour's worth of fuel in the tank and know that I am flying at 100 km/h, the destination airfield must only be a maximum of 50 km away. For safety reasons, you must always have half an hour's worth of fuel left in the tank when you land.

Junkers JUMO Tachymeter