I were in a trouble after 11 min of flight time, when RTH initiated, and It has started its flight away into a sea.. Then I got a battery error.. and it going to be only worse then.. Here is my comments, in regard to a flight data, and my actions, and if it will be interesting, I may let know DJI's initial flight data analisys. I'm still waiting more detailed report from them..
9:00 -10:52 I turned aircraft into a sport mode, and has started to climb it. During that stage of flight, aircraft has passed all altitudes range, you may assume it was a strong wind presented. Aircraft climbed with a rate of climb of average of 18 km/h (5m/s), which is its maximum rate of climb for sport mode, and during that stage, it maintains its ground position, without any significant drifts, and decreasing in a rate of climb. I can't assume that during that stage aircraft was fighted by any signifficant wind on any of altitudes, from 50m to 500m. During its climb, ground speed maintained within 0.40,7 km/h, and Mavic holds its ground position perfect. It probably might be some light wind up there, but it is unable to say about any significant influence, or like was a "fighting against strong wind", based on a flight data. In case of "wind fighting", in order to withstand it, aircraft must decrease its pitch into a wind, which will decrease its ability in a rate of climb, but during all climb stage, it has stable rate of climb, near to its maximum performance, and it holds its ground position.
10:52 Max flight altitude has been reached.
10:55 I have initiated a descend of an aircraft. Initial reaction of aircraft was ok. Its vertical speed has started to rise up to 9 km/h.
11:00 Return to home was initiated. (Return to home altitude has been preset to 45m) Aircraft was right over home point, and it turns into a "Landing" mode. While it was so high, over return to home altitude, which is 45m, it maintained unsufficient rate of descent, of about only 1km/h average. And its ground speed, has started to rise now! Might that be possible to concider seriously, that exactly right after RTH, Mavic comes into a strong wind, and has started to "fight" it? Ok, lets assume possible options, and scenarios. During a "wind fight", in order to hold its ground position, aircraft have to decrease its pitch into a wind, and it will influence on a its vertical speed, and exactly a descend was requested from aircraft to execute now, but it maintains its unreasonable low rate of descend, while it has started to go away from its ground position into a sea. It knows its home position, and was physically able to go there easy on any stage of flight, or just stay in place and descend, but it has refused to comply with it, and flow into a sea. You will see it later, down in that log.
11:35 Continue landing procedure. rate of descent 1,4 km/h ground speed 3,6 km/h, and it increasing.
11:40 I got battery error message.
11:45 Rate of descent 1,1 km/h ground speed 7,4 km/h, and increasing.
11:48 Conrtol sticks input: to increase descent rate. Rate of descent 5 km/h ground speed 8,8 km/h, and it increasing.
12:00 Conrtol sticks input, to maintain descent rate + conrtol stick input, to return aircraft. Rate of descent 10,4 km/h ground speed 3,2 km/h, and it increasing.
12:02 While holding conrtol sticks to maintain descend and to go back, vertical speed is on a rate of 10,4 km/h, and ground speed has increased to 9,2 km/h!
12:15 Control inputs: to maintain descend and to go return aircraft, and to yaw it, into a heading of a home point. Rate of descent: 9,7 km/h, and ground speed: 10.5 km/h in a derection away from home point, although it was a command to fly in to an opposite direction. Ground speed continue to rise, and now it is going to fly into a sea. It took place while aircraft is still on its "Landing" procedure, while its home point is in a opposite direction, it flew to.
12:28 Control inputs: to go back, and it is still flying away.
12:39 It going away on a speed of 18.3 km/h while on its RTH/landing procedure.
12:41 Landing canceled. Sport mode engaged. Control inputs: to descend and to return it.
12:46 GPS mode. control inputs: to descend and to return it.
12:55 Go home procedure has been re-initiated.
12:57 Ground speed 27,4 km/h! (what wind speed you expected mavic fighting now? 65 km/h+ 27,4=92,4 km/h??), and vertical speed has decreased again to 4,3 km/h
13:02 Ground speed 35,3 km/h! (what wind speed you expected mavic fighting now? over 100 km/h?? ..on a height of 247m, while it is calm on a ground?)
13:05 - 13:22 Control inputs to go back. Ground speed has decreased from 35,3 km/h to 2,5 km/h, and then it has started to increase again, while I hold control command.
13:25 Control inputs: to go back. ground speed: 18 km/h again, low descent rate 3,6 km/h.
13:39 Control inputs: to go back again. ground speed decreasing.
13:50 Only then aircraft has passed through a height of 100m, it has returned to be adequate, and react to a control inputs, and selected flight modes.
14:02 Battery error msg. Now it is 20m over "return to home altitude", and it finally has started to go back.
14:05 RTH Warning.
14:10 Low power, returning to home msg. Large Wind velocity msg. Is there wind, or no, but now on 14:15 it is quite able to return to home with a ground speed of 17,3 km/h! That desn't look like a "wind fighting". It now able to "fight a wind" with even with no descent, and with acceleration against it, but some seconds before, it was unable to perform it even while it was on descend??? come on..
14:25 It going back with a ground speed 25,2 km/h, and zero descent rate. Are you still assuming any strong wind??
14:56 Warnings: RTH. Critical low voltage. Descending excided visual avoidance system.
15:12 It descending with a normal descent rate of 10,8 km/h, and normal ground speed (""against a strong wind "")
of 30,2 km/h.
15:23 Large wind velocity msg. again
but now, it is able to "fight that wind" with a ground speed of 30,2 km/h
By the way, I was on a ground, about 50m far from it, and it was 100% calm, and no wind. Zero wind on the ground.
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Few more considerations:
For me it is significant, to lose about 30% of battery capacity, while on a critical stage of flight. And this is a huge value. Ok, I may assume, that estimation was performed before the climb was initiated, and its clear that, while climb in a progress, it will spend more battery, but then later, it have to descend, and it will spend less, then just hovering. It is about to compensate energy overdrafts, which it have spent during climb. It might be some correction taken into account, but is should not be 6:36!, or even more, if concider it within all flight time. A flight, have been finished on a time of 15:22 and ZERO battery. On a flight begining, an estimation of safe flight time was 22:14 - till a safe level of battery. And again I have a question, where has gone a 6:52? this is a significant value, which is about 30% of total capacity, and what does that battery error mean?
Aircraft has no wind sensors onboard, and it only may assume, or estimate possible wind, based on indirect factors, such as IMU and Accelerometer's data, with a context to a lift force applied to each arm, it may be assumed based on rpm. It may has failed with such estimation, or likely to say, an assumption, about an actual wind, due to a lot of factors. As an example propellers may got some ice on its leading edges, and calculations performed by algorithm, to assume an actual wind, based on: if I know rpm, I know actual lift, is going to be failed. Anyway, I had a lot of msgs and warnings, like a battery error, but on a stage, when I'm trying to return aircraft.
9:00 -10:52 I turned aircraft into a sport mode, and has started to climb it. During that stage of flight, aircraft has passed all altitudes range, you may assume it was a strong wind presented. Aircraft climbed with a rate of climb of average of 18 km/h (5m/s), which is its maximum rate of climb for sport mode, and during that stage, it maintains its ground position, without any significant drifts, and decreasing in a rate of climb. I can't assume that during that stage aircraft was fighted by any signifficant wind on any of altitudes, from 50m to 500m. During its climb, ground speed maintained within 0.40,7 km/h, and Mavic holds its ground position perfect. It probably might be some light wind up there, but it is unable to say about any significant influence, or like was a "fighting against strong wind", based on a flight data. In case of "wind fighting", in order to withstand it, aircraft must decrease its pitch into a wind, which will decrease its ability in a rate of climb, but during all climb stage, it has stable rate of climb, near to its maximum performance, and it holds its ground position.
10:52 Max flight altitude has been reached.
10:55 I have initiated a descend of an aircraft. Initial reaction of aircraft was ok. Its vertical speed has started to rise up to 9 km/h.
11:00 Return to home was initiated. (Return to home altitude has been preset to 45m) Aircraft was right over home point, and it turns into a "Landing" mode. While it was so high, over return to home altitude, which is 45m, it maintained unsufficient rate of descent, of about only 1km/h average. And its ground speed, has started to rise now! Might that be possible to concider seriously, that exactly right after RTH, Mavic comes into a strong wind, and has started to "fight" it? Ok, lets assume possible options, and scenarios. During a "wind fight", in order to hold its ground position, aircraft have to decrease its pitch into a wind, and it will influence on a its vertical speed, and exactly a descend was requested from aircraft to execute now, but it maintains its unreasonable low rate of descend, while it has started to go away from its ground position into a sea. It knows its home position, and was physically able to go there easy on any stage of flight, or just stay in place and descend, but it has refused to comply with it, and flow into a sea. You will see it later, down in that log.
11:35 Continue landing procedure. rate of descent 1,4 km/h ground speed 3,6 km/h, and it increasing.
11:40 I got battery error message.
11:45 Rate of descent 1,1 km/h ground speed 7,4 km/h, and increasing.
11:48 Conrtol sticks input: to increase descent rate. Rate of descent 5 km/h ground speed 8,8 km/h, and it increasing.
12:00 Conrtol sticks input, to maintain descent rate + conrtol stick input, to return aircraft. Rate of descent 10,4 km/h ground speed 3,2 km/h, and it increasing.
12:02 While holding conrtol sticks to maintain descend and to go back, vertical speed is on a rate of 10,4 km/h, and ground speed has increased to 9,2 km/h!
12:15 Control inputs: to maintain descend and to go return aircraft, and to yaw it, into a heading of a home point. Rate of descent: 9,7 km/h, and ground speed: 10.5 km/h in a derection away from home point, although it was a command to fly in to an opposite direction. Ground speed continue to rise, and now it is going to fly into a sea. It took place while aircraft is still on its "Landing" procedure, while its home point is in a opposite direction, it flew to.
12:28 Control inputs: to go back, and it is still flying away.
12:39 It going away on a speed of 18.3 km/h while on its RTH/landing procedure.
12:41 Landing canceled. Sport mode engaged. Control inputs: to descend and to return it.
12:46 GPS mode. control inputs: to descend and to return it.
12:55 Go home procedure has been re-initiated.
12:57 Ground speed 27,4 km/h! (what wind speed you expected mavic fighting now? 65 km/h+ 27,4=92,4 km/h??), and vertical speed has decreased again to 4,3 km/h
13:02 Ground speed 35,3 km/h! (what wind speed you expected mavic fighting now? over 100 km/h?? ..on a height of 247m, while it is calm on a ground?)
13:05 - 13:22 Control inputs to go back. Ground speed has decreased from 35,3 km/h to 2,5 km/h, and then it has started to increase again, while I hold control command.
13:25 Control inputs: to go back. ground speed: 18 km/h again, low descent rate 3,6 km/h.
13:39 Control inputs: to go back again. ground speed decreasing.
13:50 Only then aircraft has passed through a height of 100m, it has returned to be adequate, and react to a control inputs, and selected flight modes.
14:02 Battery error msg. Now it is 20m over "return to home altitude", and it finally has started to go back.
14:05 RTH Warning.
14:10 Low power, returning to home msg. Large Wind velocity msg. Is there wind, or no, but now on 14:15 it is quite able to return to home with a ground speed of 17,3 km/h! That desn't look like a "wind fighting". It now able to "fight a wind" with even with no descent, and with acceleration against it, but some seconds before, it was unable to perform it even while it was on descend??? come on..
14:25 It going back with a ground speed 25,2 km/h, and zero descent rate. Are you still assuming any strong wind??
14:56 Warnings: RTH. Critical low voltage. Descending excided visual avoidance system.
15:12 It descending with a normal descent rate of 10,8 km/h, and normal ground speed (""against a strong wind "")
of 30,2 km/h.15:23 Large wind velocity msg. again
but now, it is able to "fight that wind" with a ground speed of 30,2 km/h
By the way, I was on a ground, about 50m far from it, and it was 100% calm, and no wind. Zero wind on the ground.------------------------------------------------------------------------------------------------------------------------------------
Few more considerations:
For me it is significant, to lose about 30% of battery capacity, while on a critical stage of flight. And this is a huge value. Ok, I may assume, that estimation was performed before the climb was initiated, and its clear that, while climb in a progress, it will spend more battery, but then later, it have to descend, and it will spend less, then just hovering. It is about to compensate energy overdrafts, which it have spent during climb. It might be some correction taken into account, but is should not be 6:36!, or even more, if concider it within all flight time. A flight, have been finished on a time of 15:22 and ZERO battery. On a flight begining, an estimation of safe flight time was 22:14 - till a safe level of battery. And again I have a question, where has gone a 6:52? this is a significant value, which is about 30% of total capacity, and what does that battery error mean?
Aircraft has no wind sensors onboard, and it only may assume, or estimate possible wind, based on indirect factors, such as IMU and Accelerometer's data, with a context to a lift force applied to each arm, it may be assumed based on rpm. It may has failed with such estimation, or likely to say, an assumption, about an actual wind, due to a lot of factors. As an example propellers may got some ice on its leading edges, and calculations performed by algorithm, to assume an actual wind, based on: if I know rpm, I know actual lift, is going to be failed. Anyway, I had a lot of msgs and warnings, like a battery error, but on a stage, when I'm trying to return aircraft.
