A Brief History of Pilot Watch
2019-10-10   Watch 101

 Complicated chronograph to calculate various elements in flight?

Well, Breitling that has such a deep aviation culture is the way to go! 

“breitling history”的图片搜索结果

Established in 1884, as one of the longest watch manufacturers. Yet spread their reputation in early 1950s.

In 1952, The first Breitling Navitimer was made. 


Going into space or even common aviation didn't have help of electronic devices.

Pilots have to calculate of orientation, altitude and speed on enormous amount of mechanical gauges inside tiny cockpit.

Limited space but unlimited needs to meet. Couple dozen gauges won't do pilots any good. They need more.

Hence, this wrist-strapped computer with slide rule was born.


Then again, what the heck is a "Slide Rule", and how does it work?

Now, for general idea, it's a assisting tool that offers an direct method for pilots to do complicated calculation.

Speed, time, distance, arithmetic, conversion between kilometers and miles and so many more.

Shall we begin then, now, pleas pay attention. This is where the magic start.


Rules to learn first:

1. Only the outer chapter ring is able to spin, as to the inner can not.

2.  At the 12 o'clock position of the inner ring, there is an "MPH" mark, which is pretty straight forward what it meant.

3. When calculating with time, please convert the unit of hours into minutes.

4. Slide rule uses miles in terms of distance.

1. Multiply

For example, 13x7. You need to find 13 on the outer chapter ring, spin it to where the red 10 is and line up with it.

Next step, check for 7 in the inner chapter ring, then look what it line up to on the outer chapter ring.

As the picture shown, 91 is the answer.

2. Divide

Again, try 12/8 this time. Use 12 on the outer chapter ring to line up with 8 on the inner.

Then look for what the red 10 is indicating. In this case is 15, which is 1.5.

3. 3 digits multiplying and dividing

Since the biggest limit is 99 on slide rule. You'll need minor markers in between the bigger ones.

132x7, this time you'll line up with two markers over 13, which is stand for 13.2.

Where the 7 is pointing now? Actually somewhere between 92 and 93.

But by 2x7 we know last digit is 4, then 924 it is!

Isn't that truly amazing how little but how powerful this can work!

But that's merely for the beginners, buckle up for the wild ride.

4. Switching unit between MPH and KPH

The conversion factor for miles per hour and kilometers per hour is about 1.6. Which is 1 MPH = 1.6 KPH.

Then line up 16 on outer chapter ring to the inner chapter ring red 10. Therefore the inner ring represents MPH, outer ring is KPH.

For example, 10MPH equals 16KPH, 60MPH equals 96KPH.

5. Switching from MPH to MPM

Line up your current speed to the big white arrow on 12 o'clock says MPH.

Say 157MPH is our speed, you line it up, see what the red 10 is indicating? 26 it is.

Then we know 157MPH equals to 2.6MPM.

6. Calculating speed

Use your chronograph function to acquire the time needed to go across a certain distance.

Say it is 30 minutes to went across 45 miles. Simple thing, use 45 the outer line up with 30 the inner.

Then look for what's MPH big arrow pointing at outer chapter ring. 90 it is, so, 90MPH!

7. Calculating time

Method used over 1 minute :

Known speed as 157MPH, same old deal, line up with that big MPH arrow.

What's the time need for 500 miles, Check the outer chapter ring then.

Indicating backwards into inner ring as 19, that's 190 minutes. 

Method used under 1 minute :

Say 120MPH to go across 1.5 miles, what's the time needed

Use 12 one outer chapter ring to line up with little red arrow where inner chapter ring 36 is.

See where 15 pointing? 45, and that's 4.5 seconds in change.

8. Calculating distance

Known speed as 148MPH, looking for total distance after 28 minutes.

Use the red 60 on outer chapter ring to locate 14.8 on the inner chapter ring.

Then 28 on the outer ring will indicate you the time, which is 6.9, 69 miles.

By the same method utilizing two chapter rings, the slide rule can also be used to calculate fuel consumption rate, cruising time and fuel consumption in total.

Not only but also climb/fall rate, climb/fall time, and climb/fall distance. For further information, an official Breitling manual might do a better job than mine.