My name is Alec Myers and I’m an instrument-rated pilot who enjoys flying a single-engined Cessna around southern Ontario.
This blog is the project documentation for something I’ve been working on for the last few weeks, a solid-state open source Attitude/Heading Reference System (AHRS). That’s a small package of electronics that senses its orientation in space and sends the information to something like an iPad or iPhone which provides a display that you can use in an airplane cockpit.
If you have something like an iPhone you may have seen the cockpit-type display apps you can download. They give you an artificial horizon, and some kind of compass display and look pretty cute. Unfortunately the hardware that’s included with the average smart phone isn’t designed for this purpose and they don’t function very well. The horizon line isn’t very stable, it’s very susceptible to vibration and the compass can point pretty much anywhere.
To get accurate information to display needs something more specialized, and that’s what this AHRS project is about.
The idea isn’t new or original and in fact there’s a company called Levil Technology who make and sell exactly this kind of device, under the name G Mini. And that itself is a development of the bigger and more expensive hardware that sits in the avionics bays of all modern airliners and a lot of smaller aircraft too. But the kind of technology you need to do something useful in this field has become now quite cheap and is readily available to individuals.
Seeing the Levil webpage and reading the reviews of their very cool device inspired me to see if I could replicate – and maybe improve on – their product.
I have a technical background, including a degree in Mathematics, and in the 1990’s I spent a happy couple of years designing various electronic gadgets on a professional basis. That was all good experience for this project; now I’m writing up the details of what I’ve learned and discovered so anyone who’s interested can repeat what I’ve done, and maybe make their own adaptations and improvements. I certainly hope that will happen.
I want to add one final point: although the goal is to build something that you could use to pilot an aircraft, I’m certainly not suggesting that that is what you should do. Certified avionics for instrument flight are subjected to rigorous testing procedures and have fail-safe requirements way beyond this project. Even the G Mini is not certified for instrument flight, and that comes from a company with real resources to invest in testing and development. I certainly don’t have that at my disposal – my environmental testing facility is a domestic fridge-freezer and a hair dryer, and my kinematic test-bed doubles as the lettuce-spinner from the kitchen. I have a production run of one (maybe two) devices and no way to certify or vouch for anything involved. So if you do build anything based on what you read here – don’t imagine for one second that you should use it for any purpose in or around a real aircraft. You have been warned.