Help!... Mavic Air dropped out of sky into lake!

jmillingworth · Aug 16, 2018

Hi everyone, new to this forum but have seen some really knowledgable guys so was hoping for some assistance.

I was taking my new (24 hours old) magic air for a spin, went over a lake to take a photo and with over 30% power left in the battery it just dropped out of the sky... no warning. Can anyone help with why this might have happened and where I stand with DJI about a replacement?

InvisibleName · Aug 16, 2018

Post your log, wait for the analysis, hope that it shows some sort of system failure, expect to hear “pilot error”, hope that DJI will offer you 30% off a replacement....

microlinux · Aug 16, 2018

Upload your flight log to DJI Flight Log Viewer - Phantom Help (follow directions on the page) and post a link here. There are some very talented people on the forum who may be able to analyze.

jmillingworth · Aug 16, 2018

Thanks guys, will follow advice and post log.... then stick link in here

charliesRig · Aug 16, 2018

I'm going to say your were flying below 30ft over the surface of the water .
With you downward sensor ON

wytnyt · Aug 16, 2018

30% battery and over a lake is not good either.

Customcruiser · Aug 17, 2018

I fly my MA 90% of the time over the dirty lake and in the Bahamas even close enough to see the prop wash on the water. Never turned off any sensor and no issues

JoBri · Aug 17, 2018

30% is equivalent to a 100% chance of dropping the drone on the lake so next time apply some smart moves okay

jmillingworth · Aug 17, 2018

Link to the Flight Data is here... https://phantomhelp.com/LogViewer/ETQXAMYJ94JN9BI9U171/ seems to do something funny around the 13min mark as the imu height is negative then starts to increase quite quickly before decreasing slight until the drone hits the water. There was very little physical vertical movement in the run up the crash so it doesn't seem to fully line up with what happened. Any advice from some experienced people would be greatly appreciated... thanks in advance

Lake_Flyer · Aug 17, 2018

30% should normally be enough to make it back (if the battery was fully loaded before take off, and without too much head wind). My threshold for Low Battery RTH is 30% when I fly over water. But I never wait until it goes into RTH. I always increase the safety margins over water.

Having your drone only 24 hours with what? 20-40 minutes of total flying experience? is not going to help either. [edit] ...over water I mean.

Lake_Flyer · Aug 17, 2018

At least you took off with a full battery according to the log.
Let's hope one of our great forensic geniuses here can find the answer.

jmillingworth · Aug 17, 2018

Lake_Flyer said:
30% should normally be enough to make it back (if the battery was fully loaded before take off, and without too much head wind). My threshold for Low Battery RTH is 30% when I fly over water. But I never wait until it goes into RTH. I always increase the safety margins over water.

Having your drone only 24 hours with what? 20-40 minutes of total flying experience? is not going to help either. [edit] ...over water I mean.

I have many hours flying experience with a DJI Phantom 2 & Phantom 3 so I'm not a novice from controlling a drone point of view... I just bought myself a new Mavic Air. I have not experienced any power drop issues like this in the last 4 years of flying so was not expecting a brand new drone to drop out of the sky.. with almost perfect conditions - not much breeze, approx 45 - 50 meters away from me... drone was slightly below my eye line (I was stud on the bank) and a brand new battery with over 30% power. Funny thing is I was about to fly it back to the home point to change the battery!

Koelkop · Aug 17, 2018

What is up with people saying you should not fly with 30% battery left.....the drone was so to say on top off him!! Is there any chance off trying to find the drone? Looks like the battery fell out

Lake_Flyer · Aug 17, 2018

jmillingworth said:
I have many hours flying experience with a DJI Phantom 2 & Phantom 3 so I'm not a novice from controlling a drone point of view... I just bought myself a new Mavic Air.

OK, so it's not a lack of experience as a pilot. Check!
What I said before, 30% should be enough to bring it back.

sar104 · Aug 17, 2018

With regard to your statement "dropped out of the sky" - the aircraft was less than 2 m above the water when this happened, according to the log - correct? And unfortunately the log is incomplete - it does not record the drop. Looking at the last 15 s or so of the flight:

You were throwing it around pretty hard in sport mode, not very high above the surface which is always a bit dangerous, but it doesn't appear to have hit the water in flight. The log ends after an abrupt change from full forward elevator to centered elevator, leading to a sudden change in pitch from -37° to +40° as the aircraft attempts to slow to a stop. The most likely explanation is that the maneuver caused the battery to dislodge and disconnect.

I don't see any other precursor issues with the flight that would suggest any other failure, although in the absence of data it's not possible to say definitively what happened. In these cases, without the aircraft to examine, DJI generally seem to offer 30% discount on a new aircraft, although their response has ranged from free replacement to no discount.

FlyGuy8675309 · Aug 17, 2018

It was close enough for you to see if a bird got it so my guess is battery or prop failure is my guess.

sar104 · Aug 17, 2018

FlyGuy8675309 said:
It was close enough for you to see if a bird got it so my guess is battery or prop failure is my guess.

It was definitely neither prop failure nor a bird strike. Both of those would have been recorded in the log.

jmillingworth · Aug 17, 2018

So... a little update.... I managed to get a local Scuba diving club to come and have a dive! They found the drone (I honestly couldn't believe it!). It was in perfect condition (except wet of course), battery fully inserted and as normal... propellers intact, nothing visibly wrong with it at all... some photos attached.

When the drone dropped and hit the water - the propellers were still powered... and I tried to pull up hoping it may come out of the water. The propellers reacted to this (there was a notable increase in water surface disruption) before it finally sank out of sight. Also defo not a bird strike.

It was strange and there were two other guys with me watching... we were all in totally disbelief!

sar104 · Aug 17, 2018

jmillingworth said:
So... a little update.... I managed to get a local Scuba diving club to come and have a dive! They found the drone (I honestly couldn't believe it!). It was in perfect condition (except wet of course), battery fully inserted and as normal... propellers intact, nothing visibly wrong with it at all... some photos attached.

When the drone dropped and hit the water - the propellers were still powered... and I tried to pull up hoping it may come out of the water. The propellers reacted to this (there was a notable increase in water surface disruption) before it finally sank out of sight. Also defo not a bird strike.

It was strange and there were two other guys with me watching... we were all in totally disbelief!

Ah - so it was in the water at the end of the log. In that case, if you look at the graph above, I suspect it splashed down at around 771 s - due to the down throttle that you applied at 770 s. The accounts for the unusually steady pitch values at that time. In that case there obviously was no power disconnect and the log ends because it sank. Does that seem consistent with what you saw?