Monday, 31 March 2014

Dji Naza flyaway air crash investigation

I love my Quadcopter but some weeks ago I started to loose control of the drone multicopter for unexplainable reasons.

Dji has gotten a lot of complaints in the last 6 months from what is often called fly-aways or more humorously called the “Fly to China” feature, (“Fly to home” is a highly regarded safety feature of the Naza M flight controller).

Many of these fly aways are simply pilot errors. There are a lot of pilots out there that should not be flying UAV's in populated areas. Still, reports by experts are plentiful so the problem is real, and serious. A serious accident is bound to happen from a flyaway if the problem is not solved soon.
Many quadcopter forums (such as rcgroupsdjiguys, ausrc, phantompilots, multirotorsforum, fpvlab) have discussed the issue and there are plenty of YouTube videos documenting live flyaways. Even so, Dji seem to be unable to address the issue. They have posted a video with some tips and released a firmware upgrade but the problem remains.

If you have experienced a flyaway please join this survey:
https://docs.google.com/forms/d/1rRrJAOqJ9r2ed9WBlmyXAqJXQKwIQD4kM2wAOKpBTHc

Suggested solutions to the problem can be found all over the place. Here are some solutions found elsewhere (Not my recommendations, just added to show the variety of solution proposals from others):
  • Don’t buy Dji products.
  • Don’t put it in GPS mode.
  • Put tape around the edge of the GPS.
  • Don’t fly when the sun is low in the horizon.
  • Don't fly too close to power lines and cell towers.
  • Reduce vibrations on the bird.
  • Adjust flight mode switch/FS setup (flight mode can jump back and forth due to the control PWM signal being right on the edge).
  • Make sure IOC mode is set up properly and not mistakenly activated/deactivated.
  • Check for loose double side tape on FC or GPS.
  • Replace the GPS/Mag if damaged in crash.
  • Remove FPV Vtx, it may interface with GPS signals.
  • Keep the compass/gps puck and cable away from power leads and battery.
  • Simple shielding on all NAZA inputs to protect data integrity.
  • Remove corrosion and oxidisation of pins and push-connectors.
  • Place Naza FC as close as possible to the center of gravity.
  • Power cycle after compass calibration.
  • Avoid large stick inputs.
  • Recalibrate the compass yet again.
  • Don’t fly when solar activity is high.
  • Make sure the ESCs travel midpoint is at 1520us. Do not use 700us travel midpoint ESC.

As you can see there are several suggestions for how to prevent flyaways, but no one seem to know exactly why it is happening in the first place. It might just be a combination of many things but I would still like to pinpoint the cause of this issue as I have experienced it myself and it is getting both dangerous and expensive.

I am also open for suggestions for how to improve the questionnaire.

My first flyaway (450 quadcopter with gimbal gone haywire) can be seen at the end of this video.



How to gain control if you experience a fly away.

If you have started to experience flyaways you may try to debug the issue by buying the Dji iOSD module to log data.
Another approach is to try systematically changing one thing at a time (environmental condition, copter config, copter parts etc) and see if the fly-aways stop. During this testing create an anchor; a 2 meter long line attached to the ground and tied to the bottom center of your copter.

You may also want to put your name and phone number on your multicopter in case of a flyaway or just not finding it after a crash.