Preface: I am a novice flyer and have only flew ~30 flights or so

Something I've wanted to try out the most was the range on this thing - so I took it to the beach. I took off a bit farther back inland as to not disrupt other beach goers. It was my first battery of the day, and it was sitting at a healthy 85% due to normal battery depletion from the smart battery (I think). No problem. I flew it straight out to sea (like I've seen in many demo videos) and on full throttle in a straight line on GPS mode. I got to 4KM far- I was impressed. At this point remote signal and video link signal were both getting a bit low(but not completely cut out), and RTH gave me a warning to start flying back. I started flying back immediately. The battery meter read over 50%[!!] battery life. I put it into sport mode and full throttled back towards shore as an extra precaution as I've seen in other's demo videos.

To make a long story short, the drone did not make it back to shore in time. By the time the video feed cut out , i was still 1.22KM away from home point. By the time the battery completely died per the RC meter, the drone was still well over 500M away from the home point. The moral of the story is, RTM low battery warning cannot be relied upon as a reference point on when you should start flying back because I was nowhere close to home by the time battery died.

EDIT: Through discussions on this thread I have been made aware that RTH estimations do not take into account head or tailwind. This causes inaccuracies in time estimations and RTH should not be relied on as the sole method of when you should start heading back.

Really sorry to hear about your loss and a great lesson for us all. It's also very important to consider the weather and in particular wind, especially in coastal areas.  Often there are onshore or offshore winds depending on the time of day. It only takes a small tailwind on the way out which then becomes a head wind on the way back to have a big effect which I don't believe the app will consider.  It's also important to consider that just because the wind is light on shore that it will be the same 4km out.  As you have highlighted leaving a healthy margin is important. I hope you get it all sorted and are back in the air soon.

I've seen a couple of 'long range tests' where the wind has played a major part in the outcome. I personally don't see the point of sending the drone 4km away just to check DJI's claims on range. As soon as I loose sight of mine I start panicking - 4km out would have me in tears Anything could happen as soon as the drone goes out of line of sight and I wouldn't be prepared to gamble 1K especially over water. Hope you get a positive outcome but as I read the DJI Care policy you need the physical drone to claim.

A1000 Posted at 2017-2-2 02:27
Really sorry to hear about your loss and a great lesson for us all. It's also very important to consider the weather and in particular wind, especially in coastal areas.  Often there are onshore or offshore winds depending on the time of day. It only takes a small tailwind on the way out which then becomes a head wind on the way back to have a big effect which I don't believe the app will consider.  It's also important to consider that just because the wind is light on shore that it will be the same 4km out.  As you have highlighted leaving a healthy margin is important. I hope you get it all sorted and are back in the air soon.

Thanks for the reply. I was always under the assumption that tail/head wind is taken into account when flying. I have read the manual forwards and back, and just went to double check whether or not this is mentioned:

The colored zones and markers on the battery level indicator bar reflect the estimated remaining flight time. They are automatically adjusted according to the aircraft's current location or status

The manual seems ambiguous at best ... The reason why I had always assumed that the drone takes the wind into effect is because it would need that information in order to maintain stability during flight, so why would it not take this information into consideration when calculating battery levels to come back?

The RTH warming is an indication. In optimal conditions, it should get home, but when you have strong head wind and flew far way it went a lot further away quicker, then it can come back. It is 100% expected.

tbh, if it would have been me I would have said: well yeah, I took the risk... Bummer, I'll go a buy a new one. I understand your frustration, but it is user error... again...

Would I have had a better chance of getting back GPS mode full throttle, or SPORT MODE full throttle?

Common sense would be turning back home when you got 60-55 % battery left. Because you can't be sure: 1st- the battery metering is 100% accurate and 2nd- you may had head wind on your way back.

Psy Posted at 2017-2-2 03:03
Would I have had a better chance of getting back GPS mode full throttle, or SPORT MODE full throttle?

I assume you flew out in normal mode ? if so the switch to sport may have made things worse - the software would have calculated RTH distance/time/energy required based on the outward flight. By using sport mode the whole calculation would have got thrown out. From what I've seen the sport mode on the Mavic sucks more battery than say on a P4. The tech spec says flight time is 21mins in normal mode which has a top speed of 22mph. Sport is quoted at 40mph so basic math says almost twice the speed equals twice the energy requirement which translates to around 12mins. Here's a link to a relevant test where he basically calculates 27mins in normal mode and 17mins in sport.

The battery percentage (and associated warnings) being at 50% isn't a guarantee that you can travel a distance roughly equal to the one you've already covered, and if you think about it a little more, you should realize that it can't be made to work that way reliably. Even if the Mavic could calculate the power it would take to return against a headwind, what if the wind speed increases? And how could it know / predict that you'd (per Chris' comment above) switch to Sport mode and drain the battery even faster than you had been? The real problem here seems to be that you made multiple incorrect assumptions, such as thinking that switching to Sport mode provided a better chance of returning to your home point.

"I was always under the assumption that tail/head wind is taken into account when flying."

It isn't, and I'll be very surprised if DJI covers this under warranty since this was clearly pilot error. However, you implied that you have the Care Refresh so you may not be completely out of luck, in which case you should consider it a relatively inexpensive lesson learned.

Agree that you probably would've had a better chance doing it in GPS mode (based on what I've read in forums and watched on youtube).
Don't think winds are accounted for. Lesson for all of us, if it's ambiguous in the manual (which a lot of things are) then assume the less beneficial outcome.

Psy Posted at 2017-2-2 02:40
Thanks for the reply. I was always under the assumption that tail/head wind is taken into account when flying. I have read the manual forwards and back, and just went to double check whether or not this is mentioned:

The colored zones and markers on the battery level indicator bar reflect the estimated remaining flight time. They are automatically adjusted according to the aircraft's current location or status

I have assumed, rightly or wrongly, that it looks at a situation based on the battery %, usage, distance, but not external conditions such as wind as this can change so would add a level of complexity that makes it almost impossible to plan.  

I have always thought like a pilot of a manned aircraft and assumed that you need to have multiple and layered reserves to cope with contingencies and emergencies.  The indications and warnings are guidance  only.  I guess as a pilot of a manned aircraft you have a more direct incentive to get it all right and therefore is a good mindset

I agree the manual is ambiguous in this area as it is in many.  Maybe worth seeking clarity from DJI?

Thanks for all the opinions and feedback. I welcome the discussions so that we can all collectively learn from my experience. Like others have pointed out, I think it would be good for DJI to weigh in on two questions so far:

1) Does the RTH estimation battery life take wind speed (and to a lesser extent height) into consideration when making calculations ?

2) Does the speed advantage of being in sports mode outweigh the battery drain in this situation?

Why do people do range tests over water?

Psy Posted at 2017-2-2 04:31
Thanks for all the opinions and feedback. I welcome the discussions so that we can all collectively learn from my experience. Like others have pointed out, I think it would be good for DJI to weigh in on two questions so far:

1) Does the RTH estimation battery life take wind speed (and to a lesser extent height) into consideration when making calculations ?

1. No. See 2.

2. I am not sure, see my video (another rangetest). I switched between the both modes a couple of times.

Psy Posted at 2017-2-2 04:31
Thanks for all the opinions and feedback. I welcome the discussions so that we can all collectively learn from my experience. Like others have pointed out, I think it would be good for DJI to weigh in on two questions so far:

1) Does the RTH estimation battery life take wind speed (and to a lesser extent height) into consideration when making calculations ?

1 - No
2 - Theoretically you are travelling faster coming back than going out so you cover more distance in less time. The unknown is the wind speed - tailwind out, headwind back would screw the calculations.

SLiWooDy Posted at 2017-2-2 04:30
Why do people do range tests over water?

Why do range tests at all ?

Question #1 can be very easily answered with a little experimentation. Question #2 is a little harder to determine by experimentation, but if you watch the range test videos on YouTube where they got impressive results, you'll find that most, if not all, of them used Sport mode to do it. What does that tell you?

My brother had a defective Phantom 3 that had unusually short range. Video/RC would cut out at around 700M regardless of what condition it was in. He sent it back to DJI and they fixed it for him. That's why I wanted to do the range test to test if mine had the same manufacturer defect.

It's vox populi that the remaining flight time and the "bingo fuel"  (a.k.a. rth or you've got a problem) is just an estimation (and the user manual says so as well)

The problems main problem that you can encounter when being far away is that the winds can be completely different, so you have no way to understand how hard the little bird will have to fight against the wind.  If you push the dron away from you with tail wind, and come back with front wind your range coming back will be dramatically reduced.

I'm sorry for your lost drone.

I like to test range with my Mavic but I do it incrementally. Before reaching 3 miles, I tried 1 mile, 1.5 miles, 2 miles etc.

Don't know how the OP could've thought wind was taken into account in battery calculations, wind direction can be constantly changing.

Also, correct me if I'm wrong but with Care Refresh don't you need to be in possession of your Mavic to use that?

Chriscycling Posted at 2017-2-2 04:47
Why do range tests at all ?

I agree...it's one thing if you're flying a long distance mission in order to capture some video or stills, but just to fire out a long distance to see how far the device will go is IMO illogical.  I have flown my P4 and Mavic out about 2 miles over open fields searching for my Mother's escaped horses, but I've never "dubbed" it a "range test". Then again its up the individual owner what they choose to do with their toys

When you set out flying, it is your responsibility to plan your flight, where your flying , how much battery you need to fly your mission, assess the risks , and fly with your safety and others in mind , simply if you were going to try fly the Mavic to its limit, you should have thought about what happens if something goes wrong, can I find a safe place to land for one.

You where trying to fly an 8k round trip, what is the speed of the wind if let's say it 10mph and you have to come back up wind in normal mode, then the fastest speed I will have coming home is about 12mph how long will it take to do the trip, these are simple things to work out, and they are very much your responsibility.

Another thing flying 4K you absolutely don't have VLOS which is a requirement flying SUA , you choose to ignore this.
But you can put many at risk, i.e. Small aircraft, helicopters, hand gliders, if you read the manual as you said cover to cover, you would have come across this.

If you are not sure what exactly what's going to happen with your aircraft on such a long trip then you shouldn't take the risk,

I know this is probably an expensive lesson for you to learn, and I'm sorry you lost your AC , but I'm afraid this is an open and shut case of pilot error.

Thank you for posting others may learn from your mistakes.

Good luck..

That's why I wanted to do the range test to test

Fair enough, but surely you can admit that doing one in a location where you might lose the drone -- especially when you were (by your own description) a "novice flyer" -- wasn't a great idea. Let's face it: you made several incorrect assumptions that additional experience and / or research would have helped you avoid, and now you're here hoping to get ammunition to get DJI to give you a (free) warranty replacement instead of paying the Care Refresh fee (or worse yet, full price for a new drone).
I'm sorry you lost your drone, but I don't think you're going to win this one.

I'd guess the software algorithm for calculating RTH is something like - distance travelled & power used V distance back to home point and power remaining. All of these could be massively affected by wind and other atmospheric conditions. I'd always factor in around 10-15% margin for error in case of the above.

Thanks for the heads up. Also being a beginner myself I could see the urge to want to test the claims and not having the experience to know what to do in certain situations so experiences like this while it does suck being out of a drone, sharing for sure would help others.

DJI has the flight information to make an assessment, I'll see what they decide to do. I shared so that others can learn from my experience, as I've learned from others here

starting off with 85% was not a good idea. and rth i have tried both sport and normal, normal takes its time but always makes it back. just have to be careful with wind,and or direction of wind. coming home with the wind is a lot easier.

Just to clarify the situation:

1) Did you have Care Refresh?

2) Did you physically recover the drone?

If the answer to both of these is "yes" then you probably can get a replacement covered by Care Refresh; otherwise you're probably out of luck.

By the way, Psy, do you have a video in cache to show the last moment of your Mavic? It got to be epic.

Wandering Cloud Posted at 2017-2-2 05:34
By the way, Psy, do you have a video in cache to show the last moment of your Mavic? It got to be epic.

Nice - full of sympathy

Chriscycling Posted at 2017-2-2 05:41
Nice - full of sympathy

Hey, if his motive really is to educate the masses then what better way than to post it on YouTube?

Wandering Cloud Posted at 2017-2-2 05:34
By the way, Psy, do you have a video in cache to show the last moment of your Mavic? It got to be epic.

Under the flight log the preview screens are blacked out, it doesn't seem like I can access the video - I do have cache set to 2GB but do not see video available to click

Psy Posted at 2017-2-2 05:46
Under the flight log the preview screens are blacked out, it doesn't seem like I can access the video - I do have cache set to 2GB but do not see video available to click

You should be able to post your flight logs here,

Wow, that is completely crazy. I couldn't even start to think about losing my drone. The $1K ticket alone is enough for me to keep it super close. I have not let mine out of line of sight yet. But I have only flown mine a couple of times since I got it. I am too busy with work and kids and the like. I can't wait until i am able to get out and fly it. Good luck on getting this situation fixed.

x1War Monger1x Posted at 2017-2-2 05:52
Wow, that is completely crazy. I couldn't even start to think about losing my drone. The $1K ticket alone is enough for me to keep it super close. I have not let mine out of line of sight yet. But I have only flown mine a couple of times since I got it. I am too busy with work and kids and the like. I can't wait until i am able to get out and fly it. Good luck on getting this situation fixed.

Yeah, and I see now why he's here grasping at straws: it appears that he didn't physically recover the drone, so (as Chris and Watty2000 pointed out) it won't be covered under Care Refresh.

Psy Posted at 2017-2-2 05:46
Under the flight log the preview screens are blacked out, it doesn't seem like I can access the video - I do have cache set to 2GB but do not see video available to click

I don't believe you can view video cache files that way. On Android you can find them within the DJI folder using your file manager. If you're on IOS you need to use iTunes, I believe.

If it possible that your mavic was fighting with the wind?

Psy Posted at 2017-2-2 05:46
Under the flight log the preview screens are blacked out, it doesn't seem like I can access the video - I do have cache set to 2GB but do not see video available to click

Android should have video cache in one of the gallery folder. Not sure about IPhone. 對了，我也是台灣來的。

Chriscycling Posted at 2017-2-2 05:41
Nice - full of sympathy

Well， you know me.

UtopianCrew Posted at 2017-2-2 06:10
If it possible that your mavic was fighting with the wind?

Yes it was indeed fighting with the wind