hallmark007 Posted at 2017-2-3 07:40
Think one of the biggest problems with this thread , what exactly happened on this flight how it all went at the end, what exactly happened with RTH was it cancelled , what happened when it went into critical battery, we know RTH is automatic at this point.

Why would the OP not put up logs here if his outlying reason for posting here was to help others. I think it would help a lot more if he uploaded his logs to phantom help or even healthy drones.and posted them here.

Through the three pages of comments, no-one has asked me to upload the flight logs. I didn't even know it was possible to upload flight logs to the two websites that you pointed out. See, learning things here; but could really do without all the doubt and terrible attitude towards new pilots. I'll upload the data tonight if I have time. And I did try to share my flight logs - directly from the DJI Go 4 app. But all that did was try to share a screenshot of the flight log, which I felt were pretty useless.

Anyways, as a conclusion to this thread, DJI called me just now to give me an update. As the video feed cut out at 16% (I don't know why? Is this normal behavior to save battery life?), they cannot give a definitive analysis as to what happened afterwards. Since I could not retrieve the drone, they will not be issuing a DJI Care refresh.

They did offer me to purchase a new Mavic at a discounted rate which I accepted. In the same conversation, I relayed my thoughts on the lack of adequate warning regarding battery life in windy conditions, and confirmed with her that the RTH does in fact not take into account current wind speeds only distance traveled and GPS location. I implored them to add related warnings to both the app and the manual to avoid future confusions from other pilots. She thanked me for my suggestions and assured me that the suggestions will be passed onto the appropriate  departments.

So there you have it guys - learn from my very expensive range test. Now here's to hoping that they have Mavic so I don't have to wait as long as I did last time to get the replacement.

LarsDK Posted at 2017-2-3 00:38
Energy = mass x velocity^2  -  it is the same thing going in when you are driving your car. Going 80km/h at 5L/100km compared to going 120km/h at 10L/h, double the fuel consumption, but not double the speed. The speed is squared and that is why sports mode can not be advised for range tests.

This calculation looks great but it is wrong as it suggets that you need less and less energy the slower you fly. But the slower you fly, the longer it takes to get to your target destination and the longer you have to keep the bird in the air.

This means, while the energy for horizontal speed is increasing exponentially over speed the vertical energy consumption is linear over time. There is a sweet spot at which the energy consumption for a specific distance can be minimized. The question just is, what speed is it? Is is slower (like p-mode speed) or faster (like sports mode speed)?

Psy Posted at 2017-2-4 00:58
Through the three pages of comments, no-one has asked me to upload the flight logs. I didn't even know it was possible to upload flight logs to the two websites that you pointed out. See, learning things here; but could really do without all the doubt and terrible attitude towards new pilots. I'll upload the data tonight if I have time. And I did try to share my flight logs - directly from the DJI Go 4 app. But all that did was try to share a screenshot of the flight log, which I felt were pretty useless.

Anyways, as a conclusion to this thread, DJI called me just now to give me an update. As the video feed cut out at 16% (I don't know why? Is this normal behavior to save battery life?), they cannot give a definitive analysis as to what happened afterwards. Since I could not retrieve the drone, they will not be issuing a DJI Care refresh.

Glad your taking it well, although it seems like hostility, it's just those trying to get points across, and maybe it's a bit harsh, I know in some of my posts I was a bit harsh, so I apologise for that.

Regarding your logs there are a couple of sites you can upload them which may give you information,and this can be helpful to yourself going forward,

Links below PH can give you very detailed information you just need to go into link and follow instructions, HD not as much detail. Good luck..

http://www.phantomhelp.com/LogViewer/Upload/
http://www.healthydrones.com/

Hi guys,

This is a very important thing to know the speed you shall keep to make your drone home.
Of course finding an optimal speed for the max range does require a lot of theoretical or/and practical work. Also it is obviously depends of environment and conditions.

But as an option I believe we really could refer to DJI official specs:
"Mavic has a maximum flight time of 27 minutes (max flight time was tested in 0 wind and at consistent 25 kph speed)"

Thus, flying 27 minutes at 25 kph speed gives us 11.25 kilometers.
Ok, to make this number to be closer to a real life, let's take 2/3 of it: 7.5 kilometers totally.
Or 3.75 km one way.

So the conclusion is like following:
Having about 50% of battery, you could fly at 25 kph, and this should give 3.75 km.
If your distance to home point is much bigger - you're in trouble.


Another point is the wind. If it is a headwind then you should keep less than 25 kph. Just because you seeing a GPS speed but what is important for a flying - is a air speed relatively to aircraft. So if you will keep 25 kph then adding a headwind speed - it can be a much bigger air speed totally, that will lead to faster battery drain.

Sergey_B wrote Just because you seeing a GPS speed but what is important for a flying - is a air speed relatively to aircraft.

I guess you meant "....is an airspeed relative to the ground"

There comes a time when the wind speed would be too great for the drone to make progress, but switching to sport mode, although inefficient, is the only way of making progress over the ground and given sufficient battery time, would get you back home.

Sergey_B Posted at 2017-2-4 03:18
Hi guys,

This is a very important thing to know the speed you shall keep to make your drone home.

It is also worth when planning your flights, to always try to start your mission into the wind, this is a simple way of being able to gauge having enough time to complete your mission.

“Simplicity is the ultimate sophistication.”

rick39 Posted at 2017-2-4 03:38
Sergey_B wrote Just because you seeing a GPS speed but what is important for a flying - is a air speed relatively to aircraft.

I guess you meant "....is an airspeed relative to the ground"

If there is a case with such extremal headwind, and you're at a distance from your homepoint - any calculations or sport mode will not help you

I meant air speed relative to aircraft, when the headwind speed is not like 50 kph of course.

Sergey_B Posted at 2017-2-4 03:45
If there is a case with such extremal headwind, and you're at a distance from your homepoint - any calculations or sport mode will not help you

I meant air speed relative to aircraft, when the headwind speed is not like 50 kph of course.

This could be me Sergey_B, because I am a very simple man.
Maximum aircraft speed through the air for the Mavic is about 62kph. In a headwind of 50kph the drone will make 12kph over the ground (GPS). In P mode, say max speed 42kph, the aircraft would actually be moving further away from it's home point.

the thing about the reported range of these devices ..... my p4 can get "3 miles distance"
doesn't mean that I can go out to 3miles distance and make it back imho, it means, while in flight I can travel an estimated total distance, from take off to lading, of about 3 miles.
going out to 3 miles than back is a total of 6 miles traveled. and that is a strait line ... point a to b than back to a.
people assume they can go out to the max range and come back... that's not how it works.

Sorry to hear about your UAS not meeting the expectations of the RTH feature.  RTH does work very well and, accurately given average weather conditions. Head wind, tail wind, etc do have adverse affects on how your UAS fly’s, and your location.  I will tell you from experience when you are in a speed mode, and after enabling RTH then, switching speed modes you, WILL encounter RTH accuracy! I spent 10 years at M.I.T. and, we used to design UAS and fly them in every possible scenario our twisted minds could think of! Dji Engineer friend gave me a Mavic Pro as a gift and, It’s not a bad UAS, it has room for lots of improvements, however overall it is a decent UAS. My advice to you sir, is, when you take off in standard mode, STAY IN THAT MODE. RTH allocates enough time for your UAS to return to you once you hear the battery low warning.         SPORT MODE is best flown with your UAS within sight because, of how fast it fly’s!  

Psy - as some of the earlier posters have said, I'm sorry for your loss.  Rather than Monday morning quarterback your decision(s) I just want to thank you for sharing your experience - and the resultant loss of your bird.  I just received mine last weekend and am reading everything that's relevant - just trying to prevent any new pilot error that results in tragedy.

Hopefully your replacement Mavic is a quick ship and you have much more success with the new one.  Again - thank you for posting up this good information for us "New To The Experience" flyers.