Part 4 - Displaying the relative wind

by Ihab Awad, Founder of Airball.aero

If you missed it: Part 3 - Measuring the relative wind.

We now know that the relative wind is a simple vector and that we can measure it cheaply; but remember the X-15 control panel? We don't want that! Well it turns out, there's an alternative. If you were in the cockpit of this airplane, looking out the window, what would you see?

The vector would look like a dot, and it would move relative to your airplane. We can imagine it would get bigger and smaller depending on the strength of the relative wind. And that's all there is to it! We can build an instrument based on this principle:

The ball shows where the relative wind is coming from relative to your airplane, just like your artificial horizon shows you the ground relative to your airplane. And the cool thing is, if you are yawed left, the wind is coming from the right, which means the ball is on the right, and to get back in coordination, you ... step on the ball! That's right! This ball works the same in yaw as your slip indicator!

But you have to fly with it to feel the full effect. Rather than three variables -- angle of attack, angle of yaw, and airspeed -- you have a direct feel for the physics of flight. You can point to where the wind is coming from, and you instantly know how to re-orient your airplane to meet it. You hit a patch of turbulence and you can instantly tell what happened: your airspeed remains the same momentarily, and the ball moves up or down with your "G" forces. You can tell right away when you are close to a stall, and you can feel very clearly the sensitivity to maneuvering and how close to the edge you are. There are no bar charts or tapes or dials trying to show you a number.

And of course, this means that your entire aerodynamic state is available to you at a glance! You should be spending most of your time looking outside, not at any instrument -- even ours! This display makes sure you have all the information right away.

As you might imagine, we have built display systems too, again for under $200 in parts, and again using hobby electronics and 3D printing. We have several prototypes; a few fly regularly in N291DR, and one has a sunlight readable screen, brighter than the G1000 in my friend's DA40:

These displays connect wirelessly to our probes and use any USB power source available. We think every airplane should have one of these, and every student should train with one!

But there's more to this display than immediately meets the eye. We will talk more about that next time.

Next time: Part 5 -Dynamic pressure.