Gray Volk Posted at 1-20 16:39
Well, how do we make nice low to the ground (or water) videos?  Will it be ok to do fast strait low pass from upper position, then go up again before stopping? In the cases I saw here altitude drops happened while maneuvering, stopping after full speed.

custom FPV

JeremyFr79 Posted at 1-20 13:38
Not sure I understand you saying it doesn't show end of flight?  When I look at it in FRAP there's a disconnect at the end of the log which is when it hit the water.  Am I missing something?

Hi Jeremy,

Last part of this flight, the actually crash in the water is not in the file. Got disconnected.

But flying at 0.9 meters above water in Sport mode, my guess is that your MM lost height beacuse of the rapid pitch changes you made.From 100% aft stick to 100% Up stick (not as you said "let go of the sicks"), picth angles from 27 degrees UP to 28 DOWN, it is not strange for a drone to loose some height during this manoeuvre.
But flying at 0.9 meters (VPS measure value) no free air anough to drop little and go up again. (normal behaviour).
It did drop but could not recover....

So IMO too much rapid input at low altitude causes this loss.

BTW if the connection was still there at the impact you would have seen high pitch and roll values, so i think that the actual moment of hitting thw water is not in the file.(as it was disconnected, guess due to combination of distance, too low, reflecting signals).

cheers
JJB

JJB* Posted at 1-20 23:29
Hi Jeremy,

Last part of this flight, the actually crash in the water is not in the file. Got disconnected.

Up stick was only applied once it hit the water, so the crash was recorded but it disconnected once it hit the water, the drone was only about 200 feet or so from my position, but I was higher that it was by nearly 15 feet and imagine once the legs were in the water that was the end for the WiFi signal coming off the drone.

Labroides Posted at 1-19 01:09
I think it is GPS related, probably recalculating  alitude if new satellites found? IDK.
It had nothing at all to do with GPS.
GPS is only responsible for horizontal position data and has no impact on altitude.

Actually GPS signal is used for altitude calculation.

Steven So Posted at 1-22 23:05
Actually GPS signal is used for altitude calculation.

GPS signals in DJI drones are used only for position, not for height.
Barometric sensor data is used for keep the drone steady at flown height (with no RC up/dn input)

cheers
JJB

JeremyFr79 Posted at 1-22 20:27
Up stick was only applied once it hit the water, so the crash was recorded but it disconnected once it hit the water, the drone was only about 200 feet or so from my position, but I was higher that it was by nearly 15 feet and imagine once the legs were in the water that was the end for the WiFi signal coming off the drone.

Hi Jeremy,

Oke, but the conclusion remains the same.

cheers
JJB

A Mini user in another forum had a similar experience where his quad just dropped. He uploaded his log to Phantomhelp but it did not display any discernible issues. Another member then took the data and loaded it into Airdata and that showed multiple “Not Enough Force/ESC Error” warning messages. I believe this issue has been discussed in other threads on this forum.

Regards

Nidge

AntDX316 Posted at 1-20 19:14
custom FPV
https://www.youtube.com/watch?v=lv8nPggFgBU

Nice flight! Stupid question, was that Mini?

PS: my guess I know the answer.

Gray Volk Posted at 1-24 21:31
Nice flight! Stupid question, was that Mini?

PS: my guess I know the answer.

It's a custom quadcopter build to hold a GoPro with a very skilled pilot.

Nidge Posted at 1-23 01:30
A Mini user in another forum had a similar experience where his quad just dropped. He uploaded his log to Phantomhelp but it did not display any discernible issues. Another member then took the data and loaded it into Airdata and that showed multiple “Not Enough Force/ESC Error” warning messages. I believe this issue has been discussed in other threads on this forum.

Regards

I think the problem is in physics.

1) When drone moves fast, in sport mode, then stops there is a strong wind against the propellers. I mean relative to the drone air flow. MM is designed close to the limits, with relatively big propellers and weak motors. Motors can't fight, RPM drops. so drops the upward force props generate -> drone falls down. If there is enough altitude it recovers after a few meters. I've seen this in my other drones. Low battery and aggressive flight make it more likely to happen.

2) Also, hovering requires more power then slow flight. MM is powerful enough to hover on low battery, but I had other underpowered drones simply falling from the sky after a stop in midflight. Thus I usually spiral them down on landing.

3) Turning left/right results in 2 props slowing down, and the other two may not be able to hold it.

4) A combination, sharp turn around at high speed.

Labroides Posted at 1-19 01:09
I think it is GPS related, probably recalculating  alitude if new satellites found? IDK.
It had nothing at all to do with GPS.
GPS is only responsible for horizontal position data and has no impact on altitude.

GPS can be used for altitude when enough satellites are locked; do we know if DJI uses GPS as well as the barometer for altitude adjustment?  Sensors have little bearing above 10 metres and cease completely above 30 metres / 100 ft, so I'm just wondering if DJI do make use of GPS for altitude at all.  Appreciate this was very low level.... Just a genuine question.  

Ian

Ian in London Posted at 1-24 23:42
GPS can be used for altitude when enough satellites are locked; do we know if DJI uses GPS as well as the barometer for altitude adjustment?  Sensors have little bearing above 10 metres and cease completely above 30 metres / 100 ft, so I'm just wondering if DJI do make use of GPS for altitude at all.  Appreciate this was very low level.... Just a genuine question.  

Ian

Hi Ian,

In ATTI mode height is controlled by the barometric sensor, afaik also used for all the non-ATTI modes.
At takeoff baro metric press is measured and the indication is set to zero.

So i do not think that DJI uses GPS data for altitude height keeping, also because the height accurancy of few satellites is far more than the height hold performance of DJI drones.

cheers
JJB

Ian in London Posted at 1-24 23:42
GPS can be used for altitude when enough satellites are locked; do we know if DJI uses GPS as well as the barometer for altitude adjustment?  Sensors have little bearing above 10 metres and cease completely above 30 metres / 100 ft, so I'm just wondering if DJI do make use of GPS for altitude at all.  Appreciate this was very low level.... Just a genuine question.  

Ian

GPS can be used for altitude when enough satellites are locked; do we know if DJI uses GPS as well as the barometer for altitude adjustment?  
Do we know?
Yes, we do.
DJI do not use GPS for flight altitude.
They use the barometric sensors.

I'm just wondering if DJI do make use of GPS for altitude at all.  
No they don't

Just a genuine question.
I already gave a genuine answer back in post #10.

Gray Volk Posted at 1-24 21:52
I think the problem is in physics.

1) When drone moves fast, in sport mode, then stops there is a strong wind against the propellers. I mean relative to the drone air flow. MM is designed close to the limits, with relatively big propellers and weak motors. Motors can't fight, RPM drops. so drops the upward force props generate -> drone falls down. If there is enough altitude it recovers after a few meters. I've seen this in my other drones. Low battery and aggressive flight make it more likely to happen.

Very true.

Another factor that is overlooked by many with regards to power requirement.

Power = Voltage x Current.

As the battery’s terminal voltage drops the instantaneous current demands increase so as to maintain the power requirements. Depending on the C rating of the battery these demands for Current will exceed the battery’s ability to supply at a discrete Voltage level.

I’m not familiar with the Mini’s propulsion system and if it employs active braking. Active braking imposes greater demands especially if used to quickly decelerate the motors. It’s one of the reasons DJI started to use Sine Wave output waveforms instead of harmonic rich Square Waves in their other models such as the later model Phantoms, Inspires, Mavic Pro’s, etc. I use the same propulsion technology on my midsized Hex’s and Quads (DJI E310) to improve efficiency and agility.

Regards

Nidge.

JJB* Posted at 1-25 01:36
Hi Ian,

In ATTI mode height is controlled by the barometric sensor, afaik also used for all the non-ATTI modes.

Thanks for the reply and info JJB...

GaryDoug Posted at 1-18 21:48
Might not be a $400 loss. I see some Minis on sale for about $300 by themselves with no remote.

What are some good places to go to find used drones? Thanks.

Wiz33 Posted at 1-18 22:59
Never fly lower than 10' when above water as the water reflection will confuse the Optical sensors at times.

As a 'brand new' MM owner yet to hit the skies (awaiting arrival of new mobile phone) this is a great tip for beginners.  Thanks for sharing this information.

Wiz33 Posted at 1-18 22:59
Never fly lower than 10' when above water as the water reflection will confuse the Optical sensors at times.

A great tip for first time fliers like me, thanks for sharing this information.

fans6919a585 Posted at 1-26 09:33
What are some good places to go to find used drones? Thanks.

eBay........