Mavic Destroyed - How can I get my log analyzed?

[BudWalker]

I think I see why it turned to "Go Home" LOL. It was the home point from the beach.

I still don't understand why it moved laterally while disconnected, though, and especially not why it applied a reversal of the pitch instruction. So, chalk one up to not paying attention on the starting point. OK, that's fine and it makes sense.

What about this issue of it still behaving like it was in Course Lock, though, in terms of the reverse pitch moving the copter back towards the origin point, and not actually in reverse? Shouldn't RTH automatically kill whatever active mode the copter was in at the time RTH is initiated? Also, why mash into the cliff? What happened to its obstacle avoidance? That's a fairly large obstacle.

I looked at this flight some. Course Lock was initiated at 418 secs. At about 518 secs the RC connection was lost and the AC switched to GoHome. The AC turned towards the HomePoint, ascended to 35 meters, and started towards the Home Point. Not sure why you think it was flying sideways, it was pointed directly at the HomePoint. Here it as 521 secs after the turn towards the HomePoint was complete.

Here the taupe background is the Course Lock and the teal is the GoHome.

At 537 secs RC connection was re-established but the AC continued in GoHome mode. At 551 full negative rudder and then full negative aileron were applied. Following that at 554 full negative elevator was applied for about 5 secs. This had the effect of slowing the AC from 10 m/s to 0.5 m/s. After the negative elevator was released the AC then started to resume it's GoHome speed.


Initial impact came at 559.29 followed by several subsequent impacts, rolling and a gradual lose of altitude. It hit and then rolled and bounced down a hill.

 

[cardplayer71]

I have noticed that no one is eager to help people with these problems because when answers are given and the operators don't like the answer they start going after the messenger.

I spent a few minutes looking at the DAT file and I can tell you that from what I see the Mavic did nothing wrong. You took off with an RTH altitude set to 35M which is very low for what you were doing. The Mavic went around the cliff, it lost signal, it initiated an RTH heading exactly back to were it took off from. It went up to 35M and then I assume obstacle avoidance was off because it slammed into the side of the cliff. I could spend more time looking at it but most of the time people do not want to hear that it is pilot error.

Hi. Thank you for posting. I didn't go after any messengers; I simply asked that we wait for the log data before making subjective comments. I can see what happened here, in terms of the mistakes I made. The primary one was not paying attention to the fact that I started Course Lock mode while 800 feet out to sea. Thus, it needed to change its vector relative to the turnaround point, when it initiated RTH. This makes sense. So, we can see at the Phantom Log Viewer that the entire series of events makes sense up until it approached the cliff face.

What doesn't make sense to me is why, with 100% reverse pitch, it flew into the cliff. So, we know that I messed up in my flight planning, but now I am curious as to why the Mavic didn't obey the reverse pitch command of 100%, and fly backward relative to its head. It seems that it was still processing the commands in an "Course Lock" mode, unless there is something about the RTH behavior that I don't yet understand, which is entirely possible!

Do you know if, when it is in RTH mode, that reverse pitch would be interpreted any other way, or if the Mavic will do something other than the intended action of the operator?

Again, nobody is "going after the messenger". I think if you read this thread, I have been very thankful for people's help. What I object do is preliminary assessements without any examination of the data. All I asked for was the same respect you also desire.

 

[cardplayer71]

I looked at this flight some. Course Lock was initiated at 418 secs. At about 518 secs the RC connection was lost and the AC switched to GoHome. The AC turned towards the HomePoint, ascended to 35 meters, and started towards the Home Point. Not sure why you think it was flying sideways, it was pointed directly at the HomePoint. Here it as 521 secs after the turn towards the HomePoint was complete.
View attachment 7300
Here the taupe background is the Course Lock and the teal is the GoHome.

At 537 secs RC connection was re-established but the AC continued in GoHome mode. At 551 full negative rudder and then full negative aileron were applied. Following that at 554 full negative elevator was applied for about 5 secs. This had the effect of slowing the AC from 10 m/s to 0.5 m/s. After the negative elevator was released the AC then started to resume it's GoHome speed.
View attachment 7302

Initial impact came at 559.29 followed by several subsequent impacts, rolling and a gradual lose of altitude. It hit and then rolled and bounced down a hill.
View attachment 7303

View attachment 7304

Thank you for this insight! I figured out why I had the impression that it "appeared" to have moved sideways. During the time it was disconnected, there was no telemetry going to my handset. Thus, the part of the flight that represents the termination of the Course Lock trajectory, and the initial phase of the RTH flight, was not included due to the 28 seconds of disconnection. However, the DJI GO app renders this as a connected yellow line, so it "seemed" to have moved sideways. This new analysis of yours puts the correct visualization to the data, and it makes sense. I would prefer if they just left it as a gap and not tried to "connect the dots" here with erroneous flight path.

Thank you!

Here is what I was looking at prior to having access to these logs and your expert help:

Mavic Flight Log

• cardplayer71
• Feb 27, 2017

This created for me a false impression that it had moved sideways.

So, based on your analysis, would the reverse pitch have worked? What should I do in the future if a similar situation arises?

 

[BudWalker]

...

So, based on your analysis, would the reverse pitch have worked? What should I do in the future if a similar situation arises?

Maybe you missed this part in my post.
Following that at 554 full negative elevator was applied for about 5 secs. This had the effect of slowing the AC from 10 m/s to 0.5 m/s. After the negative elevator was released the AC then started to resume it's GoHome speed.
So it was working, you just gave up to soon. The negative elevator doesn't cancel GoHome, it just temporarily overrides it. Tricky flying for sure. Since you didn't initiate RTH I'm not sure what would happen if you pressed the RTH button. The issue is that the GoHome was initiated by the AC not the pilot. I don't have first hand experience but I think switching to Sport mode might cancel the GoHome that was in effect.

 

[cardplayer71]

Maybe you missed this part in my post.
Following that at 554 full negative elevator was applied for about 5 secs. This had the effect of slowing the AC from 10 m/s to 0.5 m/s. After the negative elevator was released the AC then started to resume it's GoHome speed.
So it was working, you just gave up to soon. The negative elevator doesn't cancel GoHome, it just temporarily overrides it. Tricky flying for sure. Since you didn't initiate RTH I'm not sure what would happen if you pressed the RTH button. The issue is that the GoHome was initiated by the AC not the pilot. I don't have first hand experience but I think switching to Sport mode might cancel the GoHome that was in effect.

Thank you very much! It definitely looks like I gave up too soon. Oh, well! Every outcome is a lesson for the next time. This one happened to cost $800.

I really appreciate your insightful analysis of the log data. I will conduct some experiments with my next Mavic on how this RTH reacts to control inputs, in a controlled environment, such as a huge field, to see what happens. I'm thinking I can mimic the disconnection by simply placing the RC into a Faraday cage to cause the AC to self-initate the RTH. Then, we will be in the same situation, and I can try the same things.

Many thanks!!!

 

[cardplayer71]

Perhaps the most amusing part of this story is that I found a drone store in Iceland the very next day, purchased a Phantom 3 Pro (that's what they had in stock other than P4P), and then the weather immediately turned to rubbish for the rest of the trip! If it was not extreme wind, it was sub-zero (C) temps, or horizontal rain, or any other number of factors, so the replacement copter got no use other than a test flight.

That mistake proved quite costly in the end. At least now I also own a P3P, which seems to be nice, especially with the PolarPro CinemaSeries filters I also bought.

 

[james_mav]

Perhaps the most amusing part of this story is that I found a drone store in Iceland the very next day, purchased a Phantom 3 Pro (that's what they had in stock other than P4P), and then the weather immediately turned to rubbish for the rest of the trip! If it was not extreme wind, it was sub-zero (C) temps, or horizontal rain, or any other number of factors, so the replacement copter got no use other than a test flight.

That mistake proved quite costly in the end. At least now I also own a P3P, which seems to be nice, especially with the PolarPro CinemaSeries filters I also bought.

My biggest question is why didn't the vision sensors stop it from running into the cliffs?

 

[cardplayer71]

My biggest question is why didn't the vision sensors stop it from running into the cliffs?

I did have downward VPS disabled due to flying low over the ocean at some points during that afternoon. However, I cannot confirm the setting for forward VPS, which I nearly always have ON. Can this be extracted from these logs?

 

[Robbyg]

Hi. Thank you for posting. I didn't go after any messengers; I simply asked that we wait for the log data before making subjective comments. I can see what happened here, in terms of the mistakes I made. The primary one was not paying attention to the fact that I started Course Lock mode while 800 feet out to sea. Thus, it needed to change its vector relative to the turnaround point, when it initiated RTH. This makes sense. So, we can see at the Phantom Log Viewer that the entire series of events makes sense up until it approached the cliff face.

What doesn't make sense to me is why, with 100% reverse pitch, it flew into the cliff. So, we know that I messed up in my flight planning, but now I am curious as to why the Mavic didn't obey the reverse pitch command of 100%, and fly backward relative to its head. It seems that it was still processing the commands in an "Course Lock" mode, unless there is something about the RTH behavior that I don't yet understand, which is entirely possible!

Do you know if, when it is in RTH mode, that reverse pitch would be interpreted any other way, or if the Mavic will do something other than the intended action of the operator?

Again, nobody is "going after the messenger". I think if you read this thread, I have been very thankful for people's help. What I object do is preliminary assessements without any examination of the data. All I asked for was the same respect you also desire.

Sorry about that, I took out my frustration with a previous crash thread on you. You had not even said anything yet and I prejudged the outcome. My Bad..

Rob

 

[Strafe1]

Your experience was educational for me. I hope you feel OK about how it all happened. This was an interesting read!

 

[cardplayer71]

Sorry about that, I took out my frustration with a previous crash thread on you. You had not even said anything yet and I prejudged the outcome. My Bad..

Rob

Rob,

Thank you and no worries! I see what you mean now. I suppose it's human nature for people to try and blame DJI or the machine, when they just blew $800 on a user error. I'd rather find out what happened, so as not to repeat the same silly (expensive) mistake. In this case, I was misled a bit by the display from the handset data, but this log cleared it right up in short order!

Regards,
cardplayer71

 

[cardplayer71]

Your experience was educational for me. I hope you feel OK about how it all happened. This was an interesting read!

I am glad if this can help someone avoid a similar experience. The moral for me is to plan the entire flight, not just the segment I am currently on. This includes the RTH ramifications with such things as mountains! Standing on the shore, looking at a video feed, I must have gotten a sense that it would just return on its path. Why? I don't know. I'll chalk this one up to experience and try and improve. Realities of geometry and physics really hurt. I'm just glad I retrieved it based on DJI's excellent software, and was able to salvage the photos and video from the trip. I really didn't care about the device that much.

 

[Cyberpower678]

Maybe you missed this part in my post.
Following that at 554 full negative elevator was applied for about 5 secs. This had the effect of slowing the AC from 10 m/s to 0.5 m/s. After the negative elevator was released the AC then started to resume it's GoHome speed.
So it was working, you just gave up to soon. The negative elevator doesn't cancel GoHome, it just temporarily overrides it. Tricky flying for sure. Since you didn't initiate RTH I'm not sure what would happen if you pressed the RTH button. The issue is that the GoHome was initiated by the AC not the pilot. I don't have first hand experience but I think switching to Sport mode might cancel the GoHome that was in effect.

The Failsafe RTH is an RTH no less. Pushing the RTH button would have returned control to the pilot. Pushing the pause button would have the same effect. Unfortunately, based on the logs, and the very detailed analysis of other posts here, I have to say this was pilot error on 2 cases. The first case is that Failsafe RTH disables OA and heads home at the pre-programmed altitude. This documented in the DJI Tutorials Video, that explains common crashes. The second was that RTH needs to be disabled, not override when you see it heading in to a cliff. Push and hold the RTH button on the controller to shut it off. You could do what you're doing at the same time to slow the drone to give you the time to disable RTH. But the drone was on GoHome mode the entire way until the crash.

Unfortunately DJI will not cover this under warranty, and you will need to use you Refresh.

To add on: Switching to Sport mode, overrides RTH and all IFM functions. If you need to quickly disable, flick the switch and back. The drone will stop.

 

[Robbyg]

Rob,

Thank you and no worries! I see what you mean now. I suppose it's human nature for people to try and blame DJI or the machine, when they just blew $800 on a user error. I'd rather find out what happened, so as not to repeat the same silly (expensive) mistake. In this case, I was misled a bit by the display from the handset data, but this log cleared it right up in short order!

Regards,
cardplayer71

Thanks Cardplayer.

And BTW when judging the RTH clearance altitude don't be too conservative. A couple of times while I was flying I stopped as i crossed a small mountain and looked at the altitude and realized my RTH was a bit too close for comfort so I paused and bumped it up a bit. Its amazing that Drone flying teaches us a new skill. I can now judge the height of distant objects a lot better.

Rob

 

[Robbyg]

The first case is that Failsafe RTH disables OA and heads home at the pre-programmed altitude.

Cyberpower this is embarrassing to admit but I did not know that Failsafe RTH disables OA
Thanks for informing me of that.

Rob

 

[Cyberpower678]

Cyberpower this is embarrassing to admit but I did not know that Failsafe RTH disables OA
Thanks for informing me of that.

Rob

Also embarrassing to admit, but I misread the manual. OA is disabled if the FVS is disabled. When I tested the Failsafe RTH and say the OA system disabled when I reconnected, I assumed incorrectly. But the manual clearly says that the appropriate RTH altitude must be set before each flight in the event of a failure.

 

[Cyberpower678]

Attach snippet.

 

[Mavicsailor]

No doubt, we are all constantly learning from this forum. Even though I've read the manual multiple times in an attempt to make this information second nature when the s..t hits the fan, I didn't recall anything having to do with OA and RTH either. Reading through it again.... the Low Battery Failsafe RTH is even more confusing.

The manual clearly addresses OA as it concerns RC loss of signal Failsafe RTH and Smart RTH, but is fuzzy on how OA behaves with the Low Battery RTH.

 

[znuttyone]

My biggest question is why didn't the vision sensors stop it from running into the cliffs?

Did you have 'RTH Obstacle Checking' set under advanced settings of the visual navigation setting .. if not , RTH would have simply risen to the rth altitude and flown directly into the cliffs , which seems to be what occurred. So I suspect this setting was off.




Sent from my iPad using MavicPilots

 

[AnzacJack]

Hi. Thank you for posting. I didn't go after any messengers; I simply asked that we wait for the log data before making subjective comments. I can see what happened here, in terms of the mistakes I made. The primary one was not paying attention to the fact that I started Course Lock mode while 800 feet out to sea. Thus, it needed to change its vector relative to the turnaround point, when it initiated RTH. This makes sense. So, we can see at the Phantom Log Viewer that the entire series of events makes sense up until it approached the cliff face.

What doesn't make sense to me is why, with 100% reverse pitch, it flew into the cliff. So, we know that I messed up in my flight planning, but now I am curious as to why the Mavic didn't obey the reverse pitch command of 100%, and fly backward relative to its head. It seems that it was still processing the commands in an "Course Lock" mode, unless there is something about the RTH behavior that I don't yet understand, which is entirely possible!

Do you know if, when it is in RTH mode, that reverse pitch would be interpreted any other way, or if the Mavic will do something other than the intended action of the operator?

Again, nobody is "going after the messenger". I think if you read this thread, I have been very thankful for people's help. What I object do is preliminary assessements without any examination of the data. All I asked for was the same respect you also desire.

It seems you made the post but wanted no input until you provided more information?
Maybe you should have waited until you had all of the required info if you didn't want any preliminary assessments