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Mavic air was crashed. It flew into the glass by himself.
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2322 51 2018-4-14
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Nesquikm
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Hello!

Mavic was just hanging by the open window, recording my wife. At some point, it flew forward (APAS enabled, and I did not touch the controls), hit the glass and fell down from the height of the 14 floors. The hit was so strong that it damage the microSD card

Be careful. Its vision is not perfect.

Video  Logs
2018-4-14
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Suren
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Sorry your crashed your Air. Looks like you started out on very low number of stats but one of the experts should be by shortly and will be able to advise you properly. That being said you should not have being flying so close to a building, the side drafts up there will move your drone quite easily.
2018-4-14
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Kevjones1959
Second Officer
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South Africa
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You are going to get asked, did you set the homepoint. Did you set up RTH correctly. Then you are going to be asked to send the other log files.  There have been quite a number of incidents and most of them boil down to not performing the pre flight checks properly. You cant just switch this thing on and take off.
2018-4-14
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Nesquikm
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RTH height was set to 80 meters. Logfile
2018-4-14
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Suren
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Nesquikm Posted at 2018-4-14 07:15
RTH height was set to 80 meters. Logfile

What he meant was is that your drone due to the low number of sats it picked up failed to record a home point before you took off. That is one of the most important rules before take off.
2018-4-14
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R&L Aerial photography
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14 floors equals approximately 140 feet, hovering outside a window filming your wife? Sounds like a perfect recipe for disaster. If you invest in another mavic I suggest you fly in the middle of an open field with very few trees and no people.
2018-4-14
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Nesquikm
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Suren Posted at 2018-4-14 07:28
What he meant was is that your drone due to the low number of sats it picked up failed to record a home point before you took off. That is one of the most important rules before take off.

Ok. It was my bad. It's just very strange that it can suddenly rush into the window (when APAS is enabled).
2018-4-14
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Aguilaair
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Nesquikm Posted at 2018-4-14 07:39
Ok. It was my bad. It's just very strange that it can suddenly rush into the window (when APAS is enabled).

Windows are not necessarily picked up by APAS as they are transparent.

As the MA uses cameras instead of radars/3d sensing transparent objects may not be detected!
2018-4-14
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Dorset_Horn
First Officer
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United Kingdom
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Possible electrical interference from A/C unit or TV antennae?
2018-4-14
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marcel_911
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R&L Aerial photography Posted at 2018-4-14 07:33
14 floors equals approximately 140 feet, hovering outside a window filming your wife? Sounds like a perfect recipe for disaster. If you invest in another mavic I suggest you fly in the middle of an open field with very few trees and no people.

Because we all spent nearly £1000 to record empty fields?

You record what you want to record.
2018-4-14
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Kevjones1959
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marcel_911 Posted at 2018-4-14 08:43
Because we all spent nearly £1000 to record empty fields?

You record what you want to record.

For what we paid I expected to get an empty field with it.
2018-4-14
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Kevjones1959
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Nesquikm Posted at 2018-4-14 07:39
Ok. It was my bad. It's just very strange that it can suddenly rush into the window (when APAS is enabled).

So a good practice is to launch once the RTH point is confirmed. Once the compass is confirmed from the map view to be correct, namely not 180 degrees out (read the threads regarding this). Then take off, make sure it is hovering and everything is cool then go fly.

Someone on this site is going to go through the logs and tell you what happened and probably why it happened. If APAS was actually engaged it is possible it should of detected the window frame or ledge or wall, mine wont fly near a doorway or window without warning on the screen.  You might find that APAS had disconnected (logs will show this). It will also show the exact joystick inputs at the moments prior to impact and the mode. Sorry your aircraft took a hit man, hope you get back in the air soon.
2018-4-14
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Suren
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marcel_911 Posted at 2018-4-14 08:43
Because we all spent nearly £1000 to record empty fields?

You record what you want to record.

Being safe and ensuring your drone does not crash or fly away should be your top priority. It is an expensive lesson learnt by the OP and sure that he will not try something like this again. True you paid for the drone but not being careful will be what you will have to pay for in the end.
2018-4-14
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JJBspark
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HI Nesquikm,

At the end of your flight your drone had a motor obstucted, see the high variations in pitch! Guess that made your drone out of control.
As you can see your distance went to zero during flight, imo because of the bad GPS signal and GPS usage.

You must been wactching the drone all the time, i you had x-checked at your mobile device you could have seen that there was something wrong.

Addition, file shows n#1 and n#2 status "block" for the last 3 records, just after Obstructed warning.I don`t know how DJI numbers the motors, left front 1 and then clockwise?

Cheers
JJB
zAnalyse1.png
zAnalyse2.png
2018-4-14
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Suren
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JJBspark Posted at 2018-4-14 10:37
HI Nesquikm,

At the end of your flight your drone had a motor obstucted, see the high variations in pitch! Guess that made your drone out of control.

Hey JB knew you would come by with another amazing analysis  
2018-4-14
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Nesquikm
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I thought that the motor was obstructed as a result of the impact by glass.
2018-4-14
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hallmark007
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Looking at your log it looks like motor obstruction happened on impact and not before, you can clearly see your aircraft loosing altitude when you received motor obstructed warning, so motor obstruction had nothing to do with your crash. You were in a pretty bad envoirment for flying and while your satellites count says 12 this means very little, it would be my observation that gps was weak and this caused aircraft to move, Obstacle avoidance or apas will not work on transparent surfaces and you can clearly see that your aircraft hit the window at an angle not head on and there is no OA on the corners or side of MavAir.
2018-4-14
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Nesquikm
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I don't blame anyone, including DJI, Mavic and Flying Spaghetti Monster I am programmer with some electronic engineering skills, and I fully understand how complicated and cool realisation of computer vision in the Mavic. I am started the thread only for warn mavic pilots about (possible) problem with translucent objects.
2018-4-14
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ghostrdr
First Officer
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Window peeper?
2018-4-14
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Nesquikm
lvl.4
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George Carlin?
2018-4-14
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SparksBird
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DJI obviously built in the "Peeping Tom avoidance" function
2018-4-14
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hallmark007
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Nesquikm Posted at 2018-4-14 11:17
I don't blame anyone, including DJI, Mavic and Flying Spaghetti Monster  I am programmer with some electronic engineering skills, and I fully understand how complicated and cool realisation of computer vision in the Mavic. I am started the thread only for warn mavic pilots about (possible) problem with translucent objects.


I didn’t think you were blaming anyone for your crash, I’m also not proportioning blame to anyone, I was just clearing up the fact that motor obstruction had nothing to do with your crash.

Understanding how gps and satellites work is most likely the cause of this crash not transparent surfaces, but it is a good warning for others.

I think you should pursue your warranty claim with dji as I have seen similar being offered warranty so hopefully luck will shine on you.
2018-4-14
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Nesquikm
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How to determine the warranty whether this is the case? Is it worth it to waste time arguing with a local store (there is no official DJI stores in Russia)?
2018-4-14
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HedgeTrimmer
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Kevjones1959 Posted at 2018-4-14 07:10
You are going to get asked, did you set the homepoint. Did you set up RTH correctly. Then you are going to be asked to send the other log files.  There have been quite a number of incidents and most of them boil down to not performing the pre flight checks properly. You cant just switch this thing on and take off.


You are going to get asked, did you set the homepoint. Did you set up RTH correctly.

I agree it is important to set home and altitude for return to home.  But in thise case, failing to do either should not have caused Mavic Air to suddenly fly into window.


2018-4-14
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hallmark007
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Nesquikm Posted at 2018-4-14 11:44
How to determine the warranty whether this is the case? Is it worth it to waste time arguing with a local store (there is no official DJI stores in Russia)?

You can arrange to send your drone direct to dji repair facility, you will first have to contact support to start a case, they have an automated procedure for returning your drone and for evaluation of your internal flight data, you can also download this dat file in dji assistant and you can send to dji but you will need to download to Dropbox as it is a very large file, once you have it downloaded you can contact a moderator and they will organize dji engineers to take a look at this file for you.
2018-4-14
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Wachtberger
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HedgeTrimmer Posted at 2018-4-14 11:45
You are going to get asked, did you set the homepoint. Did you set up RTH correctly.

I agree it is important to set home and altitude for return to home.  But in thise case, failing to do either should not have caused Mavic Air to suddenly fly into window.

I believe it's a combination of circumstancial factors, mainly weak GPS link and flying between high rise buildings where sudden air turbulences are frequent. Plus obstacle avoidance sensors confused by glass surface. All together a very risky flying environment.
Nevertheless I am also very sorry for this crash and hope the AC can be repaired.
2018-4-14
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Nesquikm
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hallmark007 Posted at 2018-4-14 11:56
You can arrange to send your drone direct to dji repair facility, you will first have to contact support to start a case, they have an automated procedure for returning your drone and for evaluation of your internal flight data, you can also download this dat file in dji assistant and you can send to dji but you will need to download to Dropbox as it is a very large file, once you have it downloaded you can contact a moderator and they will organize dji engineers to take a look at this file for you.

Thank you for your reply!
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Nesquikm
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DJI assistant does not detect the Mavic Just blinks yellow fast.
2018-4-14
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HedgeTrimmer
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JJBspark Posted at 2018-4-14 10:37
HI Nesquikm,

At the end of your flight your drone had a motor obstucted, see the high variations in pitch! Guess that made your drone out of control.

As you can see your distance went to zero during flight, imo because of the bad GPS signal and GPS usage.

Maybe I don't understand how to read the posted chart, but number of satellites shown in first part was between 10 and 12.  More than enough for GPS fix.
GPS only requires 4-satellites to determine 3D position (longitude, lattitude, and altitude) on earth.  Extra satellites help to improve accuracy through averaging.

With 3-satellites and altimeter (air pressure sensor), a drone should be able to figure out it's 3D position on earth.  
A few assumptions help with this.  Drone won't be located below earth surface, with lowest surface point being Dead Sea depression at -413 M below seal level.  Drone won't be located in outerspace, highest practial level being drone's Ceiling Cap (maximum flight altitude).

Little futher processing can compensate for brief loss of one satellite, leaving only three satellites.  Last known position can be used to pick between two possible positions given by only 3-satellites.

GPS is really about over-lapping of Spheres, and intersection points of Spheres.


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HedgeTrimmer
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Wachtberger Posted at 2018-4-14 11:58
I believe it's a combination of circumstancial factors, mainly weak GPS link and flying between high rise buildings where sudden air turbulences are frequent. Plus obstacle avoidance sensors confused by glass surface. All together a very risky flying environment.
Nevertheless I am also very sorry for this crash and hope the AC can be repaired.

I think you nailed it.  Sudden wind changes caused by air currents around high rise building, and Mavic Air not detecting Window.  
Not detecting window might have even been irrelevant.  The wind change could have been far to strong for Mavic Air to compensate for.  
2018-4-14
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hallmark007
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HedgeTrimmer Posted at 2018-4-14 12:21
As you can see your distance went to zero during flight, imo because of the bad GPS signal and GPS usage.

Maybe I don't understand how to read the posted chart, but number of satellites shown in first part was between 10 and 12.  More than enough for GPS fix.

A drone needs minimum 6 satellites for stable flight, so yes strictly if you go by the number of satellites shown aircraft at 12 would show a minimum number to be 7, you must remember that dji drones read both glonass and gps you need a minimum number 6 sats of one type.
If you are flying in between high rise buildings you maybe showing 12 but if these satellites are to close together and not providing good gps it will be noted on your bar graph this is where you should be reading you proper gps signal, those number of satellites are not a true reflection of the strength of your signal, you really need at least 4 lights lit on your bar graph for good stability.
To many people fooled by the numbers and not checking the bar graph.
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R&L Aerial photography
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I don’t think we are getting an accurate account of the story, I believe the part about a newbie pilot flying 14 stories up the side of a building, I believe that he was peeping in someone’s window, the part in question is, was it his wife?
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hallmark007
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HedgeTrimmer Posted at 2018-4-14 12:26
I think you nailed it.  Sudden wind changes caused by air currents around high rise building, and Mavic Air not detecting Window.  
Not detecting window might have even been irrelevant.  The wind change could have been far to strong for Mavic Air to compensate for.

Look at the lady when she opens the window 14 stories high, do you see any wind blowing her net curtains ?
2018-4-14
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cspain
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Would it be using GPS or GLONASS in Russia? Not sure if  it makes a difference to what happened though.
2018-4-14
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HedgeTrimmer
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hallmark007 Posted at 2018-4-14 14:33
Look at the lady when she opens the window 14 stories high, do you see any wind blowing her net curtains ?

I will have to wait till I get back home, where I don't have to pay per MB used.
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HedgeTrimmer
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hallmark007 Posted at 2018-4-14 12:34
A drone needs minimum 6 satellites for stable flight, so yes strictly if you go by the number of satellites shown aircraft at 12 would show a minimum number to be 7, you must remember that dji drones read both glonass and gps you need a minimum number 6 sats of one type.
If you are flying in between high rise buildings you maybe showing 12 but if these satellites are to close together and not providing good gps it will be noted on your bar graph this is where you should be reading you proper gps signal, those number of satellites are not a true reflection of the strength of your signal, you really need at least 4 lights lit on your bar graph for good stability.
To many people fooled by the numbers and not checking the bar graph.

you must remember that dji drones read both glonass and gps you need a minimum number 6 sats of one type  

Is that a DJI drone restriction in their implementation, requirement of 6 satellites of same type to establish 3D fix?

According to electrical engineers discussing Satellite Positioning systems.  A system needs minimum of two of a type (GLONASS, GPS, Galileo, Beidou).
For a single GPS case you need 4 Satellites for the components [X,Y,Z,  dt (the estimated receiver clock error)]. For each new systems you have  to add one bias term, describing the difference between the transmitted  time scales (since every system has it's own specific time scale) for  each system relative to one time scale


Leaving it to where you would only need 5 satellites if there were only two types.  Three GPS + Two GLONASS or Two GPS + Three GLONASS.  Rather than normal required 4 Sats of same type to get a 3D Lock (X, Y, Z, dt).
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hallmark007
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HedgeTrimmer Posted at 2018-4-14 16:03
you must remember that dji drones read both glonass and gps you need a minimum number 6 sats of one type  

Is that a DJI drone restriction in their implementation, requirement of 6 satellites of same type to establish 3D fix?

You first need to know that on all dji aircraft , from take off if you only have 3/4 satellites then there is a limiter that will only allow you to climb to 16 ft, so hence why you need minimum 6 sats to fly these drones, you can check this in your manual.
Unfortunately in the OP’s case was different IMO he got weak gps signal caused by the environment he was flying in.
2018-4-15
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HedgeTrimmer
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hallmark007 Posted at 2018-4-15 02:33
You first need to know that on all dji aircraft , from take off if you only have 3/4 satellites then there is a limiter that will only allow you to climb to 16 ft, so hence why you need minimum 6 sats to fly these drones, you can check this in your manual.
Unfortunately in the OP’s case was different IMO he got weak gps signal caused by the environment he was flying in.

A difference between Mavic Pro P and Mavic Air?   Weak signal vs. 6 Satellites or less.
I could not find anything about minimum number of Satellites in Mavic Pro P user manual.
All my Mavic Pro P user manual states is following:
Height is restricted to 16 feet (5 meters) when the GPS signal is weak and Downward Vision System is activated.
Height is restricted to 98 feet (30 meters) when the GPS signal is weak and Downward Vision System is inactivated.

I agree what is important is signal strength of GPS.  You could have a  system using 12-satellites to accurate determinate position, but all 12  signals could be weak due to cover overhead, radio interference, and  government intentional scrambling.

Of interest is what goes into DJI's displayed value of GPS signal strength, is it:
a) weakest of all satellites being used by GPS system - not necessarily all satellites being received
b) average of all satellites being used by GPS system
c) combination, average of three weakest satellites being used by GPS system
d) ???

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hallmark007
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HedgeTrimmer Posted at 2018-4-15 08:57
A difference between Mavic Pro P and Mavic Air?   Weak signal vs. 6 Satellites or less.
I could not find anything about minimum number of Satellites in Mavic Pro P user manual.
All my Mavic Pro P user manual states is following:

In your telemetry you will see number of satellites , in the bar graph underneath you will see the strength of signal, you may at times see numbers 12 satellites but graph only showing 2 bars lit, this would certainly mean weak gps signal , so the best indicator of whether you have strong signal to fly is use your graph first before relying on your numbers.
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Buzzyone
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Front right is motor one then anti-clockwise. Right rear is four.
2018-4-15
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