DJI Mavic, Air and Mini Drones
Friendly, Helpful & Knowledgeable Community
Join Us Now

Crash! Who's Fault

tpop24

Well-Known Member
Joined
Jan 1, 2017
Messages
125
Reactions
43
Age
54
I have had my Mavic for a few weeks and think its a great drone. I have been using Litchi almost exclusively and have been been working with the waypoints. After several small test runs with no issues I sent it on a 9000ft mission that would take it out of range and back. I have a lot of trees along the route that Max out at 75ft. I set my mission altitude to 95ft and thought that would be OK. There is a ten ft. elevation change along the route which honestly I didn't think of when planning the mission but my Mavic hit a 70ft tree and crashed terribly. I have noticed large discrepancies in elevation with the Mavic.
Is it my fault or a warranty issue?

Sent from my SM-G920V using MavicPilots mobile app
 
  • Like
Reactions: recon1172
Not much margin for error, if you set your mission alt to 95' and you have a 10' elivation change, that's 85' actual, so assuming the tree is 70' you have a 15' error available to you. Assuming a 10% error in the barometer, you have 5' either way. How sure are you of the tree height? The error in the barometer is based not on the Mavic but any change in the air pressure which can be dramatic in the case of approaching front. So down to you I'm afraid!

Was your OA not enabled? It saved my Mavic at the weekend by detecting a tree which was higher than expected.
 
I have had my Mavic for a few weeks and think its a great drone. I have been using Litchi almost exclusively and have been been working with the waypoints. After several small test runs with no issues I sent it on a 9000ft mission that would take it out of range and back. I have a lot of trees along the route that Max out at 75ft. I set my mission altitude to 95ft and thought that would be OK. There is a ten ft. elevation change along the route which honestly I didn't think of when planning the mission but my Mavic hit a 70ft tree and crashed terribly. I have noticed large discrepancies in elevation with the Mavic.
Is it my fault or a warranty issue?

Sent from my SM-G920V using MavicPilots mobile app


I'm not really going to point the finger to firmly, but nothing is exact so I would have left yourself some more leadway. Like you already know the height is always going to be weird since its based on where you took off from and a 9000ft mission will likely have different ground levels along that path. Sometimes the ground looks flat but isn't such. You say there was a 10ft elevation change but didn't say if it was up or down, but I think your going to find you put to much faith into a baro sensor or you miscalculated the ground elevation change. Or maybe a bit of both.
 
  • Like
Reactions: grizzard
I am pretty sure of the height. I can still fly the Mavic and can clear all aspects of the tree at 75' I could have probably dropped down to 70' but didn't want to push it.

Sent from my SM-G920V using MavicPilots mobile app
 
The Mavic started to change direction prior to the next waypoint which negated OA. I wanted it to stay straight till it reaches a waypiont then adjust heading. It started changing direction way too soon.

Sent from my SM-G920V using MavicPilots mobile app
 
I am pretty sure of the height. I can still fly the Mavic and can clear all aspects of the tree at 75' I could have probably dropped down to 70' but didn't want to push it.

Sent from my SM-G920V using MavicPilots mobile app

But when you fly again where is your take off point? If its not in the same location (say your now next to the tree) then your data is going to be different. height on your screen is not the height from the tree floor to the top of the tree but yet the height from where you took off to where you are. And it is not going to be the same every time due to margin of error.
 
So there are a couple things to keep in mind:
1) When using Litchi, never let it get out of controller range. Because if it does - you lose control and are totally relying on the automation system of the aircraft.
2) When planning Litchi missions, always check elevation changes along the route (mission hub is great for this). I always try to be at least 50-100 feet above the highest obstacle. When I scout the area I'll fly my drone and check for the highest objects and work off that.
3) Based on number 2, set your RTH alt to be about 50 feet above that. That way if it does lose connection, it will rise up to a safe level and fly home.

As far as DJI care is concerned, I'm not sure if they care how the crash occurred, but not sure. I would put a claim in and see what happens. I'm assuming you recovered the drone right?
 
It was an increase in elevation which I did forget to account for but I think it should have cleared a 75' tree.

Sent from my SM-G920V using MavicPilots mobile app
 
I took off next to the tree. The take off point is 8' above where I originally took off. If altitude was accurate on the Mavic, I don't think it would have crashes. I'll take that into consideration in future missions and increase my altitude.

Sent from my SM-G920V using MavicPilots mobile app
 
Weather is always in a constant state of change, which means the barometric pressure is always changing too. When the barometric pressure changes in the Mavic sensors, then the real altitude is unknown until an adjustment correction is made .. like in an airplane. I'm not sure if DJi Go has the ability to reset the altimeter at the destination based on weather prediction, but a pilot can do that by twising a knob, so the Mavic may have registered the incorrect altitude. I am making some assumptions here ... but it seems prudent to expand your safety margin a little. Bummer on the crash and depressing I know. I'm sure I will have my own story to tell when I make my first flight.
 
Pardon me, how do you know the trees are 75'? I do a lot of Litchi missions, and always start way too high, then evaluate the footage to see how much clearance there is before I even think of skimming the tops of trees. I have a longish mission that I'm repeating over the course of a year so I can do a time lapse through the seasons, and the mission is accurate to within a couple of metres every time (and that's on a P3P, the Mavic should be even more accurate). I would say if you got good satellite lock (12+) before taking off, then the tree may be taller than you imagined. Once your Mavic is repaired, I'd suggest you set a home point next to it and ascend until the top of the tree is level with the horizon, then you'll know the height of the tree...
 
  • Like
Reactions: Egika and Logger
I did do a test flight over the tree post crash. The camera is demolished and the landing gear is bent, front sensors are broken but she still flys as stable as ever.

Sent from my SM-G920V using MavicPilots mobile app
 
When I was able to recover the video I could tell the Mavic was much lower than 95' since it was on a mission and out of range I could not adjust altitude.

Sent from my SM-G920V using MavicPilots mobile app
 
I don't want to point any fingers, but it's certainly on you.

As others have mentioned above, you left too little of a wiggle room to account for any variations in altitude.

Send it in for repair, and take it as a lesson learned.
 
Sorry, your fault. If you take into account what others have said about margin of error, barometric pressure variance and tolerance, you cut it too close.

When I do a Litchi "mission" I'll survey the area, fly the route manually and make note of things like highest point on the route, highest object on the route, nearest tall obstacles above what I'm going to set my flight height to. Once I create my route, I'll initially set my flight altitude much higher than the tallest object. For example if I pass over trees that are 75' tall, I'll initially set the flight height to 125' and send it on its way and monitor how it does. If it appear it is correct and I have lots of room, I'll then drop the altitude down. In my example I probably won't go below 100'...
 
  • Like
Reactions: grizzard
I took off next to the tree. The take off point is 8' above where I originally took off. If altitude was accurate on the Mavic, I don't think it would have crashes. I'll take that into consideration in future missions and increase my altitude.

Sent from my SM-G920V using MavicPilots mobile app

I would recommend planning your Litchi mission on Google Earth on a desktop and then import it to Litchi and make small adjustments. By doing this you can clearly see on a Desktop elevation changes.
 
Sorry, your fault. If you take into account what others have said about margin of error, barometric pressure variance and tolerance, you cut it too close.

When I do a Litchi "mission" I'll survey the area, fly the route manually and make note of things like highest point on the route, highest object on the route, nearest tall obstacles above what I'm going to set my flight height to. Once I create my route, I'll initially set my flight altitude much higher than the tallest object. For example if I pass over trees that are 75' tall, I'll initially set the flight height to 125' and send it on its way and monitor how it does. If it appear it is correct and I have lots of room, I'll then drop the altitude down. In my example I probably won't go below 100'...
Barometric pressure variance, meaning changes in atmospheric pressure, has no effect on a single drone flight of 20 minutes within 2 miles. There may be some minor error in the instrumentation used to read the pressure but this is usually consistent. Unless you are flying through a squall line (in which case air pressure is the least of your problems) it's not going to change enough in 20 minutes to make a difference in altitude.
 
  • Like
Reactions: MavicMo
Agreed, my point was not clearly stated or more correctly I didn't state it and didn't write it, but was thinking it. lol.

My point being if one creates a mission and flys it on a sunny and warm day, then flys the same mission on a cold, overcast day with the chance of snow, barometric pressure is going to be different and "may" have an impact on how the drone flies which may not be the exact same as when they first flew the mission. This is not to say the variance would be dramatically different, but it is a variable that should be considered...


Barometric pressure variance, meaning changes in atmospheric pressure, has no effect on a single drone flight of 20 minutes within 2 miles. There may be some minor error in the instrumentation used to read the pressure but this is usually consistent. Unless you are flying through a squall line (in which case air pressure is the least of your problems) it's not going to change enough in 20 minutes to make a difference in altitude.
 
Last edited:
Lycus Tech Mavic Air 3 Case

DJI Drone Deals

New Threads

Forum statistics

Threads
130,599
Messages
1,554,245
Members
159,603
Latest member
refrigasketscanada