Known as a 'FlyAway', erratic autonomous flight has been reported in drones using a Naza flight controller from DJI, most notably the DJI Phantom. During a FlyAway pilots see the drone FlyAway, ignoring their control input. In a few cases, normal control has been regained. With symptoms inconsistent between reported instances, the cause is difficult to pinpoint. Manufacturer DJI has been reluctant to acknowledge the problem.

User Reports ¶ 

A survey of FlyAways was started by PhantomPilots.com user 'Spork'. Phantom and Naza users are encouraged to fill out the survey regardless of if they have experienced a FlyAway or not. The survey is available here and survey results are available here.

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With 39% of survey responses confirming at least one FlyAway with their Naza flight controller, an official response from DJI seems reasonable to expect. The only good news received from the survey comes from Naza-H owners with no reported FlyAways.

DJI's Response ¶ 

Eric Reagan, a journalist for PhotographyBay.com, posted his FlyAway inquiry from a DJI Q&A session during CES 2014. The recorded response is posted here on YouTube.

Unfortunately for Phantom owners, DJI's response to the FlyAway problem was to blame users for not properly following the instructions.

Analysis of a FlyAway ¶ 

Seeing an expensive piece of equipment disregard your commands and take off in a random direction is frustration at an unparalleled level. Because so many of these FlyAways drones are lost never to be seen again, video footage from any FlyAway can be incredibly valuable in diagnosing the problem. Additional On-Screen-Display video overlay information coming from the flight controller, like what the DJI iOSD offers, can be valuable in conveying internal information about the flight controller at the time of the FlyAway.

After reviewing several videos of FlyAways posted on YouTube there seem to be two different types of FlyAways.

Toilet Bowl ¶ 

The first is where the drone enters an erratic flight pattern similar to the way in which water drains down a toilet, see here and here. This could be caused by incorrect IMU information causing the drone to become unstable and unable to self level.

Return-to-Home ¶ 

The second is when the flight controller receives faulty GPS information either on takeoff when the home location is recorded or in-flight causing the drone to think it is too far from its original takeoff point. In either situation the drone flies in a straight line towards its destination, see here and here.

Our Best Guess ¶ 

With inconclusive evidence as to the cause of FlyAways we can only make a best guess as to what causes this erratic behavior with some Naza flight controllers.

  1. GPS Glitches - if the flight controller is not programmed to throw out garbage GPS information (an updated location is suddenly more than a mile away), the drone may think it needs to 'return home' causing it to fly away from the user. This doesn't take into account user override input like switching the flight controller out of GPS mode.
  2. Component Failure - drones are complex systems and electronic manufacturing is difficult; solder joints may crack leading to bad connectivity and components may fail without warning. Check out the 'Bathtub Curve' entry on Wikipedia regarding manufacturing failures.
  3. Unexpected Failsafe Activation - failsafe settings can be changed through DJI's software. Loss of signal and low battery are the two most common failsafe settings. However, neither is likely to cause a FlyAway unless concurrent with a GPS glitch causing the drone to think it is far away from home.
  4. Electromagnetic Interference (EMI) - components like the speed controllers and motors can create significant EMI which may interfere with the compass (magnetometer) and possibly the GPS radio. For this reason the magnetometer is positioned on the landing gear, as far from these EMI creating components as possible.

2 Comments

It's common to improve GPS performance on Phantoms by putting additional shielding over the GPS antenna, rerouting the GPS cable so that it goes behind the shielding instead of in front of it, and putting extra shielding around the cable itself. Some also replace the ceramic antenna with a better one. This is especially true of the Phantom 2 which has an internal wifi transmitter mounted just under the GPS antenna. There are plenty of videos on Youtube about doing this.

Marcus Bointon - Reply

Hi, I have had two p2 both bought used. It was obvious that one was well used and I didn't check it properly. So I pulled it down and found the compass lead loose. In fact it had broken away from the board. On further investigation I believe that the landing sensors are part of the compass so landing became crashing. On the second one I opened it up and made sure all the fittings were together properly before I flew it. After several failures with DJI I have come to the conclusion that their only interest is making money and not interested in customer service unless it gets them more money. The drone industry has just become a huge money hungry greedy industry. Buy a drone and it will not be supported within two years. Following in Apples footsteps.

Dave - Reply

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