RTH Tragedy

Afremont · Nov 26, 2017

Hello, first post and new to drones. I'm sure this is all my in doing, but I do have a question. I used to fly RC planes a lot, but it's been a while.

Yesterday, I was showing my new Mavic Pro to friend. I flew it around the front yard at less than 20' and all was fine until I was going to show him how it could fly itself back to home. I pushed the button and the drone immediately rocketed straight up into a tree canopy and then proceeded to do it a couple more times before dropping to the concrete driveway (naturally). I broke the camera gimbal mount (actually the anti-vibration plate) and ripped the flat circuit cable in half. Video still works, but of course I get motor overload messages about the gimbal. I watched a bunch of repair videos and I think I can fix this myself for about $40. At least I don't seem to need a full $300 camera setup or even the metallic thread video cable. I've worked on mechanical wristwatches before, so I think I can delicately handle this surgery.

My question is about overhead obstacle avoidance. Does it have any ability to do that?

BTW, I won't be flying in the yard anymore until I know every aspect of the software features. Before the crash, I also got messages about heavy interference and experienced blocky video to my phone even at very close range. Is that likely from the phone's WiFi being turned on during flying?

Thanks for reading.

sar104 · Nov 26, 2017

Afremont said:
Hello, first post and new to drones. I'm sure this is all my in doing, but I do have a question. I used to fly RC planes a lot, but it's been a while.

Yesterday, I was showing my new Mavic Pro to friend. I flew it around the front yard at less than 20' and all was fine until I was going to show him how it could fly itself back to home. I pushed the button and the drone immediately rocketed straight up into a tree canopy and then proceeded to do it a couple more times before dropping to the concrete driveway (naturally). I broke the camera gimbal mount (actually the anti-vibration plate) and ripped the flat circuit cable in half. Video still works, but of course I get motor overload messages about the gimbal. I watched a bunch of repair videos and I think I can fix this myself for about $40. At least I don't seem to need a full $300 camera setup or even the metallic thread video cable. I've worked on mechanical wristwatches before, so I think I can delicately handle this surgery.

My question is about overhead obstacle avoidance. Does it have any ability to do that?

BTW, I won't be flying in the yard anymore until I know every aspect of the software features. Before the crash, I also got messages about heavy interference and experienced blocky video to my phone even at very close range. Is that likely from the phone's WiFi being turned on during flying?

Thanks for reading.

The Mavic has no upward-looking sensors.

Mike4884 · Nov 26, 2017

Yes you have to be careful if you are very close to home I think it's less than 30 it should just land but if you are a little bit away from the home point it will rise up to your predetermined height that you set for return to home settings and return home... So in this case and every single time you fly you should always watch out for overhead stuff like trees, or wires

Alvinito · Nov 26, 2017

No vertical or sideways avoidance...only forward....but....your issue came from incorrect setting for RTH altitude. Default is 30m (100 ft) which can be changed in the app. Whenever you push RTH the first thing it does is ascend to whatever height is registered.

Afremont said:
Hello, first post and new to drones. I'm sure this is all my in doing, but I do have a question. I used to fly RC planes a lot, but it's been a while.

Yesterday, I was showing my new Mavic Pro to friend. I flew it around the front yard at less than 20' and all was fine until I was going to show him how it could fly itself back to home. I pushed the button and the drone immediately rocketed straight up into a tree canopy and then proceeded to do it a couple more times before dropping to the concrete driveway (naturally). I broke the camera gimbal mount (actually the anti-vibration plate) and ripped the flat circuit cable in half. Video still works, but of course I get motor overload messages about the gimbal. I watched a bunch of repair videos and I think I can fix this myself for about $40. At least I don't seem to need a full $300 camera setup or even the metallic thread video cable. I've worked on mechanical wristwatches before, so I think I can delicately handle this surgery.

My question is about overhead obstacle avoidance. Does it have any ability to do that?

BTW, I won't be flying in the yard anymore until I know every aspect of the software features. Before the crash, I also got messages about heavy interference and experienced blocky video to my phone even at very close range. Is that likely from the phone's WiFi being turned on during flying?

Thanks for reading.

Qoncussion · Nov 26, 2017

If you know that you are under a canopy of trees, or anything, set your RTH to hover. You should never fire it off under a canopy when it's set to return home, as it will rise to the altitude you set in the app before coming home.

Anthony · Nov 26, 2017

Really sorry to hear about your crash.

As people have already said the Mavic design does not have upward sensors. .

I can only advise you in the strongest way possible to download and spend some time reading the full Mavic user guide it would have helped prevent this crash as you would have known that the RTH function will cause your mavic to climb to the preset RTH hight before it fly's home.

My first advice when you know you are going to be flying under anything is before you take off change the RTH preferences to Hover when RTH is triggered.

You will find the guide here

Mavic Pro– Specs, FAQ, Tutorials and Downloads

Afremont · Nov 26, 2017

Wow, a lot of good replies already. I thank you all. I made the mistake of assuming that this would be easier than flying a plane but, of course, computers are involved now.

After the crash, I read where it should simply land if within a certain distance. I'm pretty sure that I was within that distance, but with altitude in the mix, I may have been just outside that range.

Looking at the Go 4 logs, it says my max altitude had been 96' feet. I'm absolutely positive that it has never been anywhere near that high. It also says I've traveled almost 1500'. And I'm quite skeptical of that too since it has only been back and forth across the yard a few times. Has it been test flown by the factory?

I really love this thing and it was sickening to see it hit the concrete, but Murphy's Law and all....

Are there any other internals that are likely be to have been damaged? There are are no cracks in the shell and nothing else fell off due to the impact. The compass seems to work okay, but when I test flew it after the crash (hovering 3' above the ground) it wasn't sitting perfectly still in the air. It went up and down a little and back and forth several inches. I chalk that up to having no camera view of the horizon, but is that a fair assumption? I'm wondering if I may have damaged a gyro chip. Thanks again for your help.

pixl · Nov 26, 2017

Sorry for the loss. But good that you've come here to chat about it -- there are some very experienced pilots here (including some commercial and GA pilots) that are here to help. Like @Anthony says... spend time with the manuals, also check out some of the helpful links on mavichelp.com

It's worth knowing that misunderstanding RTH is one of the biggest reasons for Mavic crashes. It's a great feature, but you need to really understand how it works. Obstacle avoidance (which wasn't at play in your case) also sounds great, but relying on it is another big reason for crashes. I prefer to fly without it, and just depend on my own skills.

As far as your stable hover goes, the camera has nothing to do with it. At 3' high, the downward sensors are in play, and they might be damaged -- or have a little dirt in them blocking their vision.

Roamer105 · Nov 26, 2017

Here is a thought: Since the Mavic can be set for obstacle avoidance on RTH (which I have always turned on even if I have it turned off for regular flying), it should be possible to just set like 20' altitude or something like that and let the Mavic figure out if it has to go higher. Of course, this could still be problematic if the home direction would point it at the trunk of the tree it is flying under....

Afremont · Nov 26, 2017

pixl said:
As far as your stable hover goes, the camera has nothing to do with it. At 3' high, the downward sensors are in play, and they might be damaged -- or have a little dirt in them blocking their vision.

Thanks, I was afraid that might be the case. After I fix the gimbal, if it still doesn't hover correctly, I'll probably send it off to Mavic.

I definitely will be reading the documentation. I'm trying to keep my questions here to just those that wouldn't be in the manual, such as what the crash might have damaged.

Is there any way for me to check out those sensors/cameras?

pixl · Nov 26, 2017

Roamer105 said:
Here is a thought: Since the Mavic can be set for obstacle avoidance on RTH (which I have always turned on even if I have it turned off for regular flying), it should be possible to just set like 20' altitude or something like that and let the Mavic figure out if it has to go higher. Of course, this could still be problematic if the home direction would point it at the trunk of the tree it is flying under....

Depending on OA in a scenario like that would be a mistake. When the Mavic senses an obstacle on RTH, it doesn't try to go around the obstacle, rather it tries to go up and over the obstacle. With no upward OA, the tree scenario would be fatal.

Callum · Nov 26, 2017

Sorry to hear about your crash, it's a bit of a rookie mistake, your not the first and certainly won't be the last.

Hopefully you can get it fixed up and back in the air.

Take some time to read the forums and it will give you an idea of the common mistakes that you wouldn't find in a manual.

AnchorageAk · Nov 26, 2017

These drones from DJI where promoted as RTF(Ready To Fly). A lot of people took them seriously. I see in the newer ones they try a little more to have you at least read the manual. Most of what I know came from these forums. When people like you come fore and say I screwed up, it helps us all. We learn from it, or what we know is reinforced by it. I really hate it when people get hammered for it, or ask a question and are told to read the dam manual. This is a learning forum. Which is better then learning the hard way.

sar104 · Nov 26, 2017

AnchorageAk said:
These drones from DJI where promoted as RTF(Ready To Fly). A lot of people took them seriously. I see in the newer ones they try a little more to have you at least read the manual. Most of what I know came from these forums. When people like you come fore and say I screwed up, it helps us all. We learn from it, or what we know is reinforced by it. I really hate it when people get hammered for it, or ask a question and are told to read the dam manual. This is a learning forum. Which is better then learning the hard way.

No matter what else anyone learns from this forum, the advice to read the manual is pretty much the most important lesson, and it clearly needs to be said, repeatedly. The aircraft is absolutely ready to fly, right out of the box. Many of the aspiring pilots, however, are definitely not.

AnchorageAk · Nov 26, 2017

So is answering their question. That is the point I was trying to make. Or , are you one of those that just says,"Reading the manual".

OzoneVibe · Nov 26, 2017

AnchorageAk said:
These drones from DJI where promoted as RTF(Ready To Fly). A lot of people took them seriously. I see in the newer ones they try a little more to have you at least read the manual. Most of what I know came from these forums. When people like you come fore and say I screwed up, it helps us all. We learn from it, or what we know is reinforced by it. I really hate it when people get hammered for it, or ask a question and are told to read the dam manual. This is a learning forum. Which is better then learning the hard way.

In the model aircraft world, RTF means you don't have to construct/build anything, that it's not a construction kit, that it's fully built and all you need to is charge batteries and it will, in the right hands, fly.
The DJI drones all meet this criteria.
RTF doesn't mean that it's capable of saving the operator from making mistakes.

Qoncussion · Nov 26, 2017

AnchorageAk said:
These drones from DJI where promoted as RTF(Ready To Fly). A lot of people took them seriously. I see in the newer ones they try a little more to have you at least read the manual. Most of what I know came from these forums. When people like you come fore and say I screwed up, it helps us all. We learn from it, or what we know is reinforced by it. I really hate it when people get hammered for it, or ask a question and are told to read the dam manual. This is a learning forum. Which is better ~~then~~ than learning the hard way.

I completely agree with you, and have been watching this thread for "that" conversation to fire up ~ except ~ the OP should have read the **** manual.

f3honda4me · Nov 26, 2017

Roamer105 said:
Here is a thought: Since the Mavic can be set for obstacle avoidance on RTH (which I have always turned on even if I have it turned off for regular flying), it should be possible to just set like 20' altitude or something like that and let the Mavic figure out if it has to go higher. Of course, this could still be problematic if the home direction would point it at the trunk of the tree it is flying under....

I would never do this. The systems aren't fool proof. OA is for emergencies, not something you should rely upon as part of every day flight.

Afremont · Nov 26, 2017

I know I should have studied harder. I watched all the DJI promotional videos, but I should have put a lot more effort into going through the menus and understanding what all the options are about. That said, I put my gimbal lock on to keep the video cable from being tugged at and took the drone to a much safer location to play/learn. It's hovering fairly decently, but there was a little bit of a breeze. I have trouble with the phone app disconnecting and poor video etc. I turned off wifi and Bluetooth on the phone, but that didn't much, if any at all.

It might be the USB connector on my Moto g4, I can tell when charging the phone that moving the cable will cause a disconnect and reconnect. That may be the root of most of my trouble. That's probably more than the Go 4 app can tolerate. When I separate the phone from the controller, everything seems to work fairly smoothly. No disconnects from the drone.

I do notice that the reported height, not clearance, will drop as I run back and forth over a 50-75' distance. I'm thinking that is from GPS bouncing around as it does, especially with altitude. I'm guessing without the phone providing a second opinion it errors on the side of caution.

BTW, I was having these phone app disconnects and poor video before the crash. Again, I'm thinking the USB connection to the phone is just flakey enough to cause a lot of data communication errors between the phone and the controller. I have a pretty extensive background with embedded software and hardware such as mems sensors like gyros and accelerometers. I'm hoping that if the aircraft is getting crazy data from the obstacle cams and ultrasonic sensors that it will show up on the phone messages. Right now, it only complains about gimbal issues and interference when I'm near my home. The interference messages seemed to go away when I got away from the plethora of wifi points, but the video to the phone still had issues.

Thanks again for reading my plight.

MAvic_South_Oz · Nov 26, 2017

Every flight might have different scenario for RTH, at least it should be part of your pre flight checklist.
Always plan your launch spot and RTH based on clear surrounds, and minimum height of 'things' around your flight area.

AVOID RTH from low battery if at all possible, also avoid when you manually activate RTH if you can't see your bird . . . or at least a quick scan around for nearby tree trunks / branches may help, but remember to look for HT power poles too as wires are hard to see.

It was mentioned about set RTH to hover above.
Not even sure if RTH has this option ? Never tried and not sure the 2 are connected realistically.
Thought it was only for loss wireless signal, and yes in heavy treed areas, hover on signal loss is another thing to set before such flights.

All the RTH traits (distances etc) are in the manual, it's worth reading numerous times to soak it up, concentrate on the vital features like RTH and flying traits, then look through and try the flight modes singularly until you know their behaviour, camera and video stuff should be last to learn after you know to fly it almost second nature, and know what your Mavic will do, when it will do it, in all sorts of scenarios.