Friday, June 19, 2020

DJI Spark "Hopping" (erratic behavior)

My DJI drone has had this issue with my DJI Spark where, when I try to take off, it will  sort of hover, but then "hop" up and down.  It heads toward the ground and then seems to recover.  When it is heading toward the ground, the obstacle avoidance alert is going off.


Searching the internet, I found forums littered with a gazillion about "Fly Away" issues. I do NOT consider this is a FLYAWAY issue.  It seems like there are so many issues that are blanket described as "Fly Away", and while I suppose it is possible you could lose your drone as a result of this, it is most likely just going to hit the ground straight below, worst case.  I can technically fly it around, but it is fighting me the whole time.  The obstacle avoidance alert is intermittently on and off. The drone will ascend okay, but it descends VERY slowly (which is kind of scary if you get any sort of real altitude).  Also, at random it will just start heading vertically downward even though I didn't command it to.  Again the obstacle avoidance sensor beeping when the problem is occurring. Sadly I was not able to get this anomaly on video for a better description.

This issue cropped up seemingly out of nowhere. One day it flew fine, I put it away, next season I took it out, and it flew like crap.  I could occasionally get a problem-free flight out of it, but I never had any real confidence in it.  So for the last 2 years, I have been basically not flying my DJI Spark drone, due to this weird behavior.

After months of pondering (and letting my warranty lapse), I contacted DJI.  I described the issue and they recommended I send it in  to DJI for paid repair.  On the repair estimate, it said that the drone had crashed:
"After carrying out the damage assessment, we found that the unit has physical impact damage, unfortunately the damage that is not caused by product malfunction is Non- warranty repair; We'll either repair it or replace it with a product that's new or equivalent to new in both performance and reliability after payment has been received. For more information, please visit (http://www.dji.com/service/policy) - DJI North America"
The bit about impact damage was BS. I am the only one who has ever flown this thing, and I baby it.  The most I have ever done is buzzed a wall.  It has never impacted anything.  My guess is this is what they write on anything that gets shipped to them that doesn't fall under "warranty repair".  But I had no other viable options so I told them just to go ahead.

Weeks and $150 + shipping later, I got my drone back with a slip saying they replaced the vision system.  And lo, it did fly correctly... For a few (gentle!) test flights.  Then one day I took it out to fly and it started doing the hopping thing again.  I tore my hair out, ready to scrap this noisy money pit.  One last time I refocused my Google search terms to include "hopping", and that's when I hit the jackpot.  I found a handful of postings on DJI's forum of people who seemed to have the exact same problem. While there were a ton of the usual unhelpful responses (i.e. "Get rid of it! Sell it to me!"), I saw a couple of postings saying that the issue was solved by replacing the props. At first I just wrote this off.  Why would props make any sort of difference as to how the craft would fly (other than, maybe, FLY or NOT FLY)?  Okay maybe "FLY but be LOUD"...  But this post got my attention.  after a while, I realized I had the following options:
  1. Throw away drone?
  2. Buy a full set of genuine DJI props, and then throw away drone after proving it makes no difference.
So I did the latter.

And it worked.

WTF?!?!?

So naturally I now have some new questions.  How the hell is this behavior really caused?  One idea I had is that excess prop vibration somehow causes the obstacle avoidance sensor to falsely trip. 

Then there is the issue of the earlier "repair".  This was obviously the problem all along. It seems that DJI was more than happy to take my money to "fix" the craft, when the only issue was the props.  Think about it, there must be thousands of people who have experienced this problem, and I'm sure DJI customer service has enough data to recognize this as being a prop issue right off.  But either they didn't, or they chose not to tell me.  I would give them the benefit of the doubt, but then they did tell me they found "crash damage".

Anyway, lesson learned.  If your unit is out of warranty, think twice before sending it in to DJI for repair.  The only guarantee appears to be that you will pay them a hefty repair fee.