The Mythical Fly-Away

The saga usually begins like this: “There I was minding my own business and starting to fly my Phantom when suddenly it took off in one direction never to return”. Does this sound familiar?

The forums have been buzzing with reports of “fly-aways” for quite some time, but is this a real phenomenon that plagues the little DJI quadcopters as a manufacturing defect… or is there something more to this? Let’s be clear on one thing, straight-off… yes, fly-aways are real. Yep, I said it, they are real.

After (quite literally) years of tearing into the issue, I think I’ve been able to finally put this one to rest. Though it is true that better documentation could help avoid the issue from happening in the first place, there is no reason to believe that “fly-aways” are in any way a sign of defect, however. Let’s talk about what is actually occurring when what we’ll now just call an “uncontrolled flight” or UF takes place.

Loss of Guidance Indicator / RFI / EMI

The Phantom Series of aircraft utilize a duo of sensors that are responsible for ascertaining location and bearing. In order to maintain flight-time, these sensors have to be small and run on minimal power. The duo consists of a GPS Receiver and Electromagnetic Compass. A small processor on-board the GPS board then provides the NAZA Flight Controller with location and heading information. Okay, nerdy stuff aside… that’s a pretty complicated dance that’s taking place in your little machine. If one component isn’t doing its job… or is encountering interference, then the dance becomes lesser a Waltz; moreso a “Carlton” or “Elaine”. Little kicks.

There are multiple forms of interference that can cause UF. The most common is going to be loss of GPS because one is flying underneath obstruction, or in a location devoid of clear-view of satellites (like Iceland, as read before). Another type of interference responsible for UF can be caused by storing, launching from, or flying near sources of electromagnetism (sidewalks, steel structures, transformer buckets) and can alter the polarity of the Electromagnetic Compass onboard the Phantom. There is also a loss of GPS situation that can occur when flying over deep water (which will be covered a bit more extensively in our next blog).

In all of these events, error codes are generated and cause UF to occur due to conflicting information being given to the Flight Controller. If your aircraft is triggered to go into failsafe mode… or even if you are flying manually and instruct the vehicle to travel in one direction – these commands have to have GPS and/or Compass bearing information in order to complete the task. Imagine that if you were hiking and you know that to go from one set of coordinates via GPS to the next one that you must travel north to get there. Now imagine your compass believes that North is actually East due to an error. Which way do you go? Uh oh… we’re throwing some error codes in your brain now, aren’t we?

Precautionary and Reactive Measures

The point is, I’ve never seen UF in an aircraft that was caused by defective equipment. In all cases, interference of some sort is to blame, and carefully monitoring GPS connectivity, always calibrating the compass, knowing and taking control in ATTI Mode (which requires NAZA Mode activation) will with every flight insure that Uncontrolled Flight never occurs.

For information about NAZA mode activation, please read my related entry by clicking here and for details on how to properly perform calibrations, I have a great video for you, click here.

Also, I certainly welcome your comments, questions and even suggestions. So please drop me a line by clicking here.

Best regards,

Eric Davis
Technology Manager

Joel J.
Joel J.