How to Use an E6B Flight Computer

Before you start: reading the scales

The calculator side has two logarithmic scales. The outer scale is fixed and the inner scale turns. The numbers repeat every power of ten, so "15" can mean 1.5, 15, 150 or 1,500. The scales are divided more finely at the low end: between 10 and 11 each small mark is 0.1, while between 50 and 100 each mark is 1. Read carefully and you can get about three significant figures.

Two marks matter more than the others. The RATE index (the triangle at 60) represents one hour, and the 10 index represents the number 1 for multiplication. Open the E6B simulator in another tab to follow each example.

Time en route

220 nautical miles at a ground speed of 88 knots. How long?

1. Turn the disc until the RATE index is under 88 on the outer scale.
2. Find 22 (the distance) on the outer scale.
3. Read the inner scale below it: 15.
4. Estimate: 220 miles at almost 90 knots is about 2½ hours, so 15 means 150 minutes, 2:30.

The hours ring inside the minutes scale shows 2:30 next to the 15.

Distance flown and ground speed

Distance. At 120 knots for 45 minutes: put the RATE index under 12, find 45 on the inner scale and read 90 above it: 90 nautical miles.

Ground speed from a timed leg. You flew 32 nautical miles between checkpoints in 16 minutes. Put 16 on the inner scale under 32 on the outer scale and read above the RATE index: 120 knots. Timing a known distance is how you check your planned ground speed in flight.

Fuel

Fuel works exactly like distance, with gallons per hour instead of knots.

• Fuel used. Burning 8.5 gallons per hour for 2:30: RATE index under 85, read above 15 (150 minutes): 21.25 gallons.
• Burn rate. You used 21 gallons in 2:20 (140 minutes): put 14 under 21 and read above the RATE index: 9.0 gallons per hour.

True airspeed

150 knots calibrated at a pressure altitude of 10,000 feet and −5 °C.

1. In the altitude window, turn the disc until 10 (thousand feet) sits over −5 °C.
2. Find 15 (150 knots calibrated) on the inner scale.
3. Read the outer scale above it: about 174.5, so about 174 to 175 knots true.

The exact compressible answer is 174.0 knots; the wheel's density method is within half a knot at this speed. See the true airspeed calculator.

Density altitude

With the same window setting method, set a pressure altitude of 5,718 feet over 21 °C and read the density-altitude window: about 7,700 feet. The exact dry-air value is 7,697 feet. The density altitude calculator explains where the numbers come from.

Unit conversions

Put the known value on the inner scale under the matching arrow on the outer scale and read the others. With 50 under NAUT, the STAT arrow shows about 57.5 statute miles and the KM arrow about 92.6 kilometers.

Multiplication and division

To multiply 2.5 by 36, put the inner 10 index under 25, find 36 on the inner scale and read 90 above it. To divide 150 by 2.5, put 25 under 15 and read 60 above the inner 10 index.

The wind side

The back of the E6B solves the wind triangle. With a true course of 090°, true airspeed 120 knots and the wind from 045° at 40 knots:

1. Turn the rose until 045° is under the TRUE INDEX.
2. Slide the grid so the grommet is on a convenient arc, say 100, and mark a dot 40 knots straight up from the grommet.
3. Turn the rose until the true course, 090°, is under the TRUE INDEX. The dot swings to the left.
4. Slide the grid until the dot is on the 120-knot arc.
5. Read the ground speed under the grommet, 88 knots, and the drift line through the dot, 14° left: the true heading is 090° − 14° = 076°.

The dot left of center means correct left; right of center means correct right. The simulator's wind side runs these five steps for any numbers you enter, and the wind correction angle calculator checks the result.

Practice routine

Work each problem type on the wheel, then check it with the calculator. When the two agree within a percent or so, move on to the next type. On test day, a mechanical E6B or an electronic flight computer is allowed in the testing room; phones are not.