Working the wind wheel

The E6B flight computer—also known as the whiz wheel—is a navigation tool with its roots way back in the 1930s, but many of today’s student pilots shy away from using it. Maybe it’s the instrument’s unfamiliar looks, the intimidation factor of all those scales, its two sides (flight computer and “wind side”), or the learning curve required to master its use. But that curve isn’t so steep, really. A few hours are all it takes to be able to spin the wheel like a pro. Even so, the wind side continues to vex even the most diligent. Maybe it’s because we’re completely focused on today’s GPS-based navigation. Look up on the GPS display screen, and there it is: instant—and extremely accurate—groundspeed, course, track, time to destination, and even winds aloft information.

No one can argue that GPS provides essential data, quickly. On the other hand, no one can deny that we have become spoiled by the marvels of GPS, and that relying on GPS alone deprives us of having an extra layer of navigation expertise that may come in very handy the day your GPS acts up, your batteries die, or your alternator conks out.

The wind side of the E6B can be an especially useful aid in determining your groundspeed and wind correction angle during cross-country preflight planning. Some E6Bs even let you calculate the crosswind components prior to landing at runways experiencing strong and/or gusty winds. And while en route, you can update your groundspeed calculations should the winds aloft change.

While there’s no specific regulatory requirement to master the E6B, many flight schools continue to use it as a teaching tool. Yes, you can legally use electronic flight calculators and online flight planning software to come up with heading and groundspeed information—but why not have a foolproof backup?

Before we solve a couple of common flight planning problems using the wind side of the E6B, it’s important to emphasize the difference between true and magnetic courses and headings. True courses and headings are referenced to true north. Magnetic courses and headings take into account the variation of the Earth’s magnetic field, called variation. Another factor, deviation, takes into account the influences created by the magnetic fields generated within the airplane. Together, they produce compass heading. In the end, what’s important to the pilot navigating by dead reckoning are the magnetic and compass headings—because that’s what’s depicted on the instrument panel.

Reference dots

The wind side uses a rotating compass rose with a frosted surface. That surface lets you make erasable reference marks for wind speeds and directions. A second component, a sliding grid, is used to see groundspeeds and visualize crosswind and headwind components.

Planning with known winds

Let’s say flight service has told you the winds aloft on your route—always given in reference to true north (except by control towers)—are 315 degrees at 20 knots. And let’s say the course line you’ve plotted on your sectional—which will also be in reference to true north, so will be a true course—is 250 degrees. Let’s say magnetic variation is 10 degrees west, or plus 10 degrees (the easy way to remember this is east is least, or minus, and west is best, or plus). You’ve already calculated that your true airspeed will be 120 knots.

• Rotate the compass circle until the true index at the top of the computer is above 315, for the wind direction.
• Slide the sliding scale until the central hole at the axis of the circle is over any arc. For simplicity’s sake, let’s put it over the arc corresponding to 120, for your true airspeed. Make a pencil mark 20 units up, at the curved line labeled 140. You’ve now plotted a 20-knot wind out of 315 degrees true.
• Now rotate the circle until 250—your true course—is beneath the true index. Slide the scale, without turning the compass circle, until the wind dot you made earlier is over the 120 arc. Now you can immediately see that the winds aloft require a nine-degree wind correction angle to the right, meaning you must fly a true heading of 269 degrees. You’ve added nine degrees to the right for the wind correction angle, plus 10 more degrees for the magnetic variation.
• Now look down at the circular scale’s center reference hole. It’s over 110, meaning that you’ll have a 10-knot airspeed penalty from the winds aloft.

Finding altitudes for most favorable winds

You can use the same procedure as above to determine the effects of winds aloft at several different altitudes. Identify each pencil dot with the appropriate altitude, and you can quickly see which altitude’s winds will give you the biggest tailwinds (or least headwinds).

Radius of action

Sometimes called the “point of no return,” your radius of action is the time or distance you can fly outbound on a given course, turn around, and still have enough fuel to reach the departure point. Knowing this can be a big help when flying over the mountains, desolate areas, or over water. Here’s the sequence for figuring the turning point:

• After determining both your outbound course from the departure point and the inbound course for the return—which will be the reciprocal of the outbound course—calculate your groundspeed out and your groundspeed back, using your wind and true airspeed information as calculated earlier.
• Determine the endurance of the airplane in hours and minutes, based on the fuel aboard, power setting, and fuel flow rate. Don’t forget to allow for your required fuel reserves.
• Add the groundspeed out to the groundspeed back.
• On the other, flight computer side of the E6B, rotate the inner, C scale so as to put the airplane’s endurance under the total of the groundspeeds out and back.
• Now look on the computer’s outermost A scale to find the groundspeed back. Directly under this, on the C scale, is the time to make the turn and still return safely to the departure airport.

These and many other useful calculations can be made with the help of the E6B’s wind side. Many textbooks and other references can help make you a believer in this ancient art. Remember: your GPS receiver can let you down. Knowing how to revert to old-school practices can make you look like a real pro—and maybe even save the day.

Tom Horne is editor at large for AOPA Publications.