Part 6 - One true instrument

by Ihab Awad, Founder of Airball.aero

If you missed it: Part 5 - Dynamic pressure.

One of the advantages of having cheap hobby electronics, computers, and 3D printed parts, is that we can do almost anything. Want our airspeed spoken to us by a cartoon character? Done. Want coupons from nearby airport restaurants on the PFD. You've got it. But ... what is it a good idea to do?

Instruments should support our flying ability, not replace it. And so my goal is not to tell the pilot what to do, but rather to visualize to them the full picture of their data so they can decide what to do. To me, being truly in touch with the physics of your airplane is far more useful -- and safe -- than being jolted awake by a "stall warning" at some unexpected time.

The Airball project is Open Source. Anyone can take our work and re-use, or extend, or remix it however they want. But for our own work, we have a very specific esthetic, and that is: sensing the wind. By which we mean, if some piece of information can be gleaned from the onrushing wind, it might be useful. If not, it might not belong on Airball.

We can sense the barometric pressure and outside air temperature (OAT) for an extra $6 in microchips. What does that give us? Well, obviously an altimeter. And true air speed (TAS). So we put that into our instrument:

• Notice how we re-interpret our V speeds:

  • VFE, VNO and VNE are limits on dynamic pressure and become qFE, qNO, and qNE. They are tick marks around the size of the ball.

  • VY, VX, VREF and VS1 are limits on angle of attack and become αY, αX, αREF and αS1. What about VS0? It depends on how flaps affect your airplane's stall angle of attack. We're still thinking about this one.

• The ball has an IAS readout in knots to act as a bridge to how we fly right now, and the TAS is a magenta ring around the ball. The magenta ring is invisible at sea level, and fades in as your density altitude increases, giving you an instant feel for your density altitude.

• The gray "halo" is a history of where the ball has been in the last second, which gives you feedback on how "bad" your turbulence is compared to your current angle of attack and stall margin.

• And finally, we added an altimeter with our own compact climb rate display that we invented, and it can be set to the current barometric reading!

This information is all you need for simple day VFR. One glance and you can look back out the window where you are supposed to be looking! And this information is all derived from the airflow. No GPS, no other fancy things. Just "tasting" the airflow with sensors.

Isn't it nice that we can derive all the information you need for day VFR from the airflow? It sort of "feels" right, doesn't it? We believe that, if Wolfgang Langeweische had the technology of the 21st century, this is what he would have designed! In fact, for light-sport aircraft and ultralights, this may indeed be the one true instrument! And for beginning students, we believe this is the best thing to start with.

Next time: Part 7 - Where we go from here.