How To Use An E6B Calculator

Ahhh the E6B. This simple yet intricate device continues to send shivers up the spines of students and experienced pilots alike. What looks like a complicated piece of equipment is actually a very easy to use, amazing device! With the E6B you can do multiplication/division, time/speed/distance problems, wind correction angles, fuel burn calculations, true airspeed calculations, density altitude problems, conversions, and it'll even make your coffee, although I haven't unlocked that secret yet.

Ok, that was bad. I'll just stick to the teaching part and shy away from the jokes. Let's start with some basic elements of the E6B. The front side is composed of two wheels: a fixed wheel (the outer wheel, a.k.a. the black wheel), and a movable wheel (the inner wheel, a.k.a. the white wheel). The most important thing to remember is that time is ALWAYS on the inner wheel, distances (and amounts if doing a fuel burn calculation) are ALWAYS on the outer wheel. Finally, you'll notice on the inner wheel there is a black arrow above the number 60. This will ALWAYS point at the speed on the outer wheel.

There's one other thing we should cover before we move on. The numbers on these wheels have "floating" decimal points. All this means is that the number 50 could represent the number 5, 50, 500, 0.5, 0.05, etc. You will only find the numbers 10-99 on the device, so if the number you are searching for falls out of that range, you have to move the decimal point to make it fit in that range. For instance, you would use the number 10 to represent 100. Because of this, when you use the E6B to find an answer, you have to think about the value of the number and move the decimal point appropriately. Example: you are burning 10 gallons an hour and want to know how much fuel you'll burn in 20 minutes. Using the E6B you'll get the number 33. Know, if you are only burning 10 gallons per hour, you know there is no way you could burn 33 gallons in less than an hour, so the number 33 represents 3.3.

The inner, movable wheel

The outer, fixed wheel

Let's start with a time/speed/distance calculation. Here's the problem: we are traveling at 107 kts. How much distance will we cover in 45 minutes. The best way to start these problems, if you already know the speed, is to rotate the inner wheel until the arrow points at the speed on the outer wheel. As you can see here we've already done that. Wait, why is it pointing between 10 and 11? Remember, the only numbers on here are between 10 and 99; 107 is outside of that range. We can make it fit in that range by moving the decimal to the left, using 10.7 to represent 107. Now, what other piece of information do we already know? That's right, we know time! As we learned earlier, time is ALWAYS on the inner wheel. So, keep the wheel right where it is with the arrow pointing at 107, and on the inner wheel find the number 45.

Now, what number is opposite of it on the outer wheel? 80. Yep, that's it, you will travel 80 nautical miles in 45 minutes. Let's try another. Same speed, 107 kts, but this time we want to know how long it will take to travel 16 miles. So, we have the arrow pointing at our speed, and we know the distance (16), so look for it on the outer wheel. Now, what number is opposite of it on the inner wheel? 90. Hmm, that doesn't seem right. I doubt that it will take 90 minutes to cover only 16 miles. What if we slid the decimal one place to the left? 9 minutes, yes that makes a lot more sense!

Ok, let's try a fuel burn calculation. We're flying an airplane that burns 19 gallons per hour in cruise, we want to know how much fuel will be burned after 27 minutes. First, I should mention that the rate of fuel burn is just a speed. It is how FAST we are burning fuel. So, since we know the speed, we've turned the inner wheel so that the arrow points at 19. Now, since we know the time (27 minutes) we are going to find 27 on the inner wheel, then find what number is opposite of it on the outer wheel. It looks like it matches up with 85. Now, since we are burning only 19 gallons per hour, we know there is no way that we could've burned 85 gallons in less than an hour. So, let's move the decimal place once to the left, and we get 8.5 gallons. That is correct!

Let's try one more fuel calculation. Still burning 19 gallons per hour, now we want to know how much flight time we could get out of 60 gallons. Since we know the amount, we're looking for 60 on the outer wheel. The number that matches up with it on the inner wheel is 19. Considering that 60 is about 3 times as much as 19, I doubt that we could only fly for 19 minutes. Let's move the decimal once to the right, which gives us 190 minutes, or 3 hours and 10 minutes. Notice on the inner wheel, below the 19 there is a tick mark which sits next to 3:00. Each of those tick marks represent 10 minutes, so the one below the 19 represents 3:10. So when the minutes are greater than 60, you can look below to find the answer in the Hrs:Mins format.

Check back soon for a lesson on how to use the other side of the E6B to calculate wind correction angles and groundspeed.