So I just watched in horror as my Mavic Air took a dive into our lake after a short flight. I have flown the thing 80 times without many errors (other than the prompt to recalibrate the compass when it was new) and weak signal.

Today I took my usual route over our lake to shoot a tug boat (which I often do, and always within LOS) and then the MA prompted with a "In Flight, working IMU encounters attitude exception, please slowly get craft back if craft behave abnormally) - I pressed the RTH button and watched as the MA took a hard right and then a nosedive into the lake.

While I realize the risks of flying over water, I would love to know what I did wrong, and if the fault lies with me (or the MA). Perhaps I can learn from a mistake, if I was indeed at fault! If not, I am hoping that the unit can/will be replaced as I have fallen in love with the shots I get of boats and vessels on the water!

Thanks for any help you can provide! Can't wait to get back in the air!!!

Datalog of my crash

-P

UPDATE - 8/27/18
After contacting support and submitting all Flight Logs (flights 1 through 81), this was determined to be a warranty issue and is being covered by DJI. No futher detail was given, however, the follwing email was just received:

Dear Customer,

  

Thanks for your patience.

  

The unfortunate incident that occurred to your aircraft has been confirmed as a warranty case according to our data analysis.

   

We would like to offer you a replacement, Mavic Air Arctic White aircraft (without the remote controller and battery charger). Please kindly send us the following information:

  

Shipping address:

  

Contact name:

  

Phone number:

  

Should you have more questions, please feel free to let me know.

  

Thanks for your support. Have a nice day.

   

Best Regards,

   

Evelyn

  

DJI Tech Support

What a great testament to DJI and the diligent work of their support team. They've got a customer for life!

Line of Sight you say. Must have had those binoculars. Can't tell what went wrong. But that flight was EXTREMELY risky.

LordoftheFlies Posted at 2018-8-19 18:04
Line of Sight you say.  Must have had those binoculars. Can't tell what went wrong. But that flight was EXTREMELY risky.

You'd be surprised how well the LED's show up at dusk over the lake - no problem seeing it plunge to its demise.

As for risk, this craft has proven up to the task at this distance and altitude before, and always made it back. Risk also had little to do with an "IMU" error popping up for the first time in its life.

Point still remains, what when wrong?

Parkeway Posted at 2018-8-19 18:09
You'd be surprised how well the LED's show up at dusk over the lake - no problem seeing it plunge to its demise.

As for risk, this craft has proven up to the task at this distance and altitude before, and always made it back. Risk also had little to do with an "IMU" error popping up for the first time in its life.

Have you tried contacting a dive club to try and retrieve the drone.
If it is still under warranty and the drone can be retrieved you may have a good chance at getting a replacement through dji support.
If the drone cant be retrieved then unfortunately this may remain a mystery as to what actually happened.

Good luck

IS there anyway for you to upload your DAT file via Dropbox? Do you have the drone? Or is she still in the drink?

LordoftheFlies Posted at 2018-8-19 18:40
IS there anyway for you to upload your DAT file via Dropbox? Do you have the drone? Or is she still in the drink?

Also have YOU done any IMU cals?

I don’t think you should use RTH when IMU has problem. You are asking your aircraft to take control when the most important sensor to keep it stable is not working. As IMU has problem it will not be able to keep stable on air. When you give up control the aircraft may not be able control itself and fall from sky.

What you should do is watch it carefully and fly back slowly. If see anything wrong you need to take immediate control to recover it.

Taking off with out a proper sat lock - 12 at least. Also relying on RTH in a critical situation = sorry mate.  

Looking at your data I’m wondering if you realized your drone was heading for the drink quite a while before you hit RTH.  Once your drone changed to Go Home there were only 0.3 seconds before no more  data from her.

If you go and look at data starting at about 2:55 into flight you started loosing altitude.  You had been flying at about 68 ‘ then starting descending to final height of  -98’ at final transmission at 3:36 ..  your drone was going down from 2:55 to 3:36 from 68’ to -98’ or loss of altitude of 166’ in roughly 41 seconds.  Looks like you may have flown it into the water?

Were you paying attention to altitude?

I agree with you, if the drone has followed that same flight path in the past and there's been no damage pre-flight then the IMU error seems like a hardware issue?

If MA is within your LOS you should see it’s decenting and pull it up by RC. Don’t understand why you use RTH.

I guess the question is, what is the actual height above sea level your take-off point is?


It looks like you were applying 100% down throttle until you got to about 9 feet below where you took off from, then without any further throttle input (ignore other values like yaw etc because it appears your may have a different stick setting? so originally your throttle was showing as yaw in the program) your bird just started reporting even lower altitudes and I think this may have been where it crashed into the water. Roll and pitch values were thrown over the place at this time and that was probably due to hitting the water as well. Hitting RTH would have done nothing to save it. That's my observation anyway.

From where you took off from, how many feet is it above river?  Getting different numbers varying from 10-feet to 90-feet.

HedgeTrimmer Posted at 2018-8-19 23:16
From where you took off from, how many feet is it above river?  Getting different numbers varying from 10-feet to 90-feet.

HI,

Takeoff point 33 meters above water level (iaw Google Earth)
So pretty sure it crashed into the water.

Why? several warnings of not having enough power, so imo craft could not hold its height at the end of this flight. Flying that low (not VLOS) means there is no time for any recovery action.
RTH will stop the fwd flight and sets the heading to the homepoint before raising height. This uses power wich wasn`t there enough.
See the amps in my chart ; blue line is PITCH (guess other stick setting than mode2), amp level not as high as before while applying 100% fwd.

Strange roll headings at the end; from right 47 degrees to left 45 degrees.
It was so close to the water level (if the baro height is 100% accurate it was 4 meters above lake level or was this less??)
I think it was so close to the water that it loss some height stopping the fwd movement that is just hit the water.

Guess DJI can tell why there wasn`t enough power at the end of the flight.

cheers
JJB

I’m sorry, but over 7000 ft away and you can see the LEDS?  

Going to have to go with the others and call BS on the line of sight statement. Log shows your drone was over 7,000 feet away when this happened. Being able to see an LED is not the same as being able to see your drone in its entirety and know what it's doing.

Looks like you hit the RTH right as it crashed into the water. Before that, it dropped almost 100 feet in 4 seconds and was doing 50 MPH when it hit the water. I know it's over open water, but the log looks more like a drone that hit something and is falling out of the sky than anything else.

DJI will tell you that you have to have a corpse to return to them to get a new drone.

Thats a weird log.

Altitude very low the whole flight but VPS "N/A" so i assume sport mode.
The speed is picking up and up near the end (54mph !?)

And yeah 7000ft is way way beyond VLOS.  No way anyone could have seen it actually crash.

It seems to EXIT sport mode after 3 mins and then under P-GPS mode gets up to 50+ mph.  Wind conditions at the time?

It behaves like it is in ATTI mode at the end. not P-GPS mode

As others have stated...something seems "quirky" with the altitude.  According to the log you weren't flying over 70 feet the entire flight.

Appreciate the feedback guys! This was definitely a learning experience - one that I can chalk up to a hardware failure and my inability to get out of the jam with manual control.  

My usual route starts at 90ft plus above lake level. I then descend into the heading of most tugs and intersect (actual altitude is rarely even below 40-50ft above lake level, . In this case I descended manually until I got the warning, at which point I let go of the sticks hoping it would level. Instead it jerked right and made a beeline for the drink. I do most shots at dawn and dusk, and in this case had a direct view of it out to the tug. From takeoff to to target, I have a wide open view of the lake, the glideslope is gradual, although pronounced.

As for the IMU calibration, I have done several over the course of 5 months, but not that day, as it gave every indication it was RTF.

It won't be recovered (I'm a diver and even I won't make a 110ft dive into the blackness of our lake) but will just chalk this one up to not trusting the hardware farther than I can throw it. I look forward to more flights with the knowledge that I use in my racing life: "If you think it can go wrong, plan on it going wrong", and "never risk anything you aren't willing to lose TODAY!"

Thanks for the input guys! What a great group!

-P

Not sure its a hardware issue.  Those altitudes are very very low.  A tiny bit of deviation, wind gust and so on and the thing would clip.

You were way way outside any possible visual line of sight to see exactly what happened.

How are you getting 50+ mph on the drone, especially in P-GPS mode?  Its a very odd last few seconds flight log, as someone says, it looks more like ATTI mode than P-GPS.  Did you actually switch from sport to P-GPS?  Also were bottom sensors manually disabled?

It's really dangerous to fly low over water far away. Flying fast and low over water even worst. You won't be able judge the above water by fpv view. When the lower sensor warning sound it's only a fleet above the water. You have no time to do anything when thing going wrong. No way you can saftly control a LED light 7000 fleets away close to water.

If you fly close above water, sensors can be irritated due to the reflections making the drone want to go down to land. If you want to fly close above water
you have to deactivate the sensors.

JJBspark Posted at 2018-8-20 00:08
HI,

Takeoff point 33 meters above water level (iaw Google Earth)

Thanks JJBspark.  

I was trying to come up with measurements in altitude of takeoff and river (aka takeoff height above water) other than from FlightLog file information.
Reason was to either confirm FlightLog's information or not.  The FlightLog as others have pointed to had some unusual numbers.

When I tried to use GPS coordinates to get altitudes from several different sources, the takeoff point was anything fro 10-feet to 90-feet above river.

Tviscomi Posted at 2018-8-20 04:51
As others have stated...something seems "quirky" with the altitude.  According to the log you weren't flying over 70 feet the entire flight.

It's not just the altitude - toward the end, the log shows in P mode but the aircraft is going 54mph.  Even with a tailwind, I've never gotten more than 44mph out of my MA.

I used google earth to do a rough estimation of your take off height to the level of the river.  If you use Google Earth and scroll over the location you started it will show you the height at that location (bottom right hand corner along with lat/Lon). I did not know your exact take off Point but am  pretty close from the photos in above post.  According to GE you took off at an altitude of roughly 625 feet.   The river is 100 feet below that level at about 525 feet.  From that point you went up an additional 90 feet.

When you hit the drink you were at an altitude of  -90 feet which is about 100 feet below your reference take off height.  No instrument error.  The MA gave you good data until it went fishing.

Not sure what happened but I call pilot error in judgment.  I, for the life of me do not see how you can see those lights at 1.5 Miles. According to your data when viewed on GE there are an awful lot of trees around your takeoff point too.  But maybe you were on top of your house, I don’t know.

Pilot error in judgement..
Flying at night
Flying 1.5 miles away to get a pic of a tug
Not paying attention to the altitude dropping
  Not paying attention to battery required to get home
Looks like you had a good tail wind by looking at speed, so probably would not get home anyway if you turned around when it told you to
  
Did you by any chance record the screen of your viewing device?  I would recommend that in the future as it is just another set of good data to see what you were being told during the flight.

I would suggest next time, wait for the tug to pass behind you house...

Paul_IA Posted at 2018-8-20 03:55
Going to have to go with the others and call BS on the line of sight statement. Log shows your drone was over 7,000 feet away when this happened. Being able to see an LED is not the same as being able to see your drone in its entirety and know what it's doing.

Looks like you hit the RTH right as it crashed into the water. Before that, it dropped almost 100 feet in 4 seconds and was doing 50 MPH when it hit the water. I know it's over open water, but the log looks more like a drone that hit something and is falling out of the sky than anything else.

I concur, max LOS distance for my machine is 1500 feet, on a good day. At night, maybe 1700, but not much further, as the leds begin to blend. That being said, I have made it a point not to fly in twilight as I get weird signal interference with the aircraft and nearby radio tower.

Well this is Interesting...

Operating drones over water has pros and cons when compared to over land:

Pros:

Largely unobstructed areas (less collisions likely)
More likely laminar wind (not so gusty)
Clear Line of sight to pilot
Mostly less permission/privacy issues (owner(s) of the surface you’re overflying

Cons:

Radio link problems when flying low (water tends to absorb 2.4/5.8GHz waves quite well)
Harder to deploy/retrieve (if take off/landing is not at the shore)
If there is a malfunction and goes in the water very hard or impossible to retrieve


IMU Errors would have caused your Altituide issues.   When my drone has problems displaying height a Quick IMU Calibration fixes it.  

Lake doesn't absorb signal in this case, but does exactly opposite / reflect it.

That bit in JJB's analysis where it says "NotEnoughPower". LOL. Most likely as it was under water! This smacks way more of user error than anything else. Also, where can I get some cyborg eyes like yours than can see a tiny object 7000ft away!

You are really adventurous ,how could you fly this distance !

were there any birds like gulls?

Paul_IA Posted at 2018-8-20 03:55
Going to have to go with the others and call BS on the line of sight statement. Log shows your drone was over 7,000 feet away when this happened. Being able to see an LED is not the same as being able to see your drone in its entirety and know what it's doing.

Looks like you hit the RTH right as it crashed into the water. Before that, it dropped almost 100 feet in 4 seconds and was doing 50 MPH when it hit the water. I know it's over open water, but the log looks more like a drone that hit something and is falling out of the sky than anything else.

I totally agree with you , the drone might hit something at that point and went down water

Hey P, Did you do any mods on this aircraft 7000ft is a heck of some distance also i see you were clocking near 54Mph that's some serious pep there.

dwainwayne28 Posted at 2018-8-21 05:08
Hey P, Did you do any mods on this aircraft 7000ft is a heck of some distance also i see you were clocking near 54Mph that's some serious pep there.

Hey dwain - no, no mods whatsoever. The ONLY thing I can imagine is that the speed you see was recorded while it was in free fall or perhaps inverted pulling down to the water from 60 feet or so.

They are replacing the MA due to a "Warranty issue" according to the datalog, but I inquired for further details on the what/when/why of the crash and they haven't gotten back yet.

I knew it was something fishy (pardon the pun) because I've made the same flight 80+ times (usually 17mph, 30mph in Sport) and have had no trouble whatsoever other than sketchy signal. This was a complete freakout on the part of the MA with no control whatsoever. Maybe a motor locked up or IMU just went haywire. I seriously considered that it had been hit with one of those anti-drone guns from the barge, thinking maybe the cargo was super secret (NASA comes by all the time) but who knows.

Anyway, I'll probably make the leap to a Mavic 2 Pro soon - DJI obviously stands behind its product!

You have a response indicating this is a warranty issue, but I have to wonder if using return to home at the first sign of a sensor error is the best choice. I use return to home occasionally to make sure I know how it is going to behave, but it’s not my go-to option at the first sign of unexpected behavior.

Tom_A Posted at 2018-8-28 06:38
You have a response indicating this is a warranty issue, but I have to wonder if using return to home at the first sign of a sensor error is the best choice. I use return to home occasionally to make sure I know how it is going to behave, but it’s not my go-to option at the first sign of unexpected behavior.

Appreciate the feedback, and no, it generally isn't my go-to - in this case I had less than a seconds notice that something was wrong, and in that moment, when it didn't respond to stick input and inverted, I held the RTH button hoping it's internal control would take over. Unfortunately no.

But again, thanks for the feedback!

Parkeway Posted at 2018-8-19 18:09
You'd be surprised how well the LED's show up at dusk over the lake - no problem seeing it plunge to its demise.

As for risk, this craft has proven up to the task at this distance and altitude before, and always made it back. Risk also had little to do with an "IMU" error popping up for the first time in its life.

I am glad it was covered by warranty. yeah i am able to see my drones for atleast a mile over a lake. I think you were flying responsibly, i mean how else are you supposed to capture a tug boat?

MavicFit91 Posted at 2018-8-28 06:52
I am glad it was covered by warranty. yeah i am able to see my drones for atleast a mile over a lake. I think you were flying responsibly, i mean how else are you supposed to capture a tug boat?

Looking forward to the M2P and the zoom function. I normally pick the big boys up around 2000ft and orbit for another half mile - they make for great subjects in a warm evening sky. The zoom should let me draw in to hull id distance without the need to travel out there.

The fact that we're even talking about this technology stills boggles my mind. Wonder what the guys who worked on the Saturn V next door in Huntsville would've thought about an orbiting, hovering, semi-autonomous aircraft with a real-time 4k camera and <1in home point landing accuracy.  Can't imagine what the next 25 years will look like!

Up 2000ft? Is this a typo? DJI Go should not allow you fly up over 1500ft.