Drone did not descend and stopped recording

[BudWalker]

Hi BudWalker,

Found an better example where a (my) Mini4Pro does not descend with RC down input.
In the log from 9m19s , not descending with RC down input.


cheers
JJB

Any chance you could provide the .txt for these two flights?

 

[Droning on and on...]

Hi,

Low heights starts above the IR range, max descend is slowed down from approx 40 meter baro height.

By "baro height" are you referring to the height above takeoff, displayed in the lower left of DJI Fly, derived from the barometer in the drone?

If so, this height is irrelevant to flight behavior in every DJI drone I have owned over the last decade (other than the configurable ceiling in settings, RTH).

I fly an Avata and a Mini 4 Pro (and others) at cliffs on the ocean in Santa Cruz weekly, usually in an altitude envelope -70 to +200 feet with no odd behavior on the altitude response to the throttle stick. I was just there (Seacliff State Beach) yesterday.

I launch from a parking lot at the top of the cliffs. Watch this, no weird behavior by the DJI FPV:

 

[JJB44]

By "baro height" are you referring to the height above takeoff, displayed in the lower left of DJI Fly, derived from the barometer in the drone?

If so, this height is irrelevant to flight behavior in every DJI drone I have owned over the last decade (other than the configurable ceiling in settings, RTH).

I fly an Avata and a Mini 4 Pro (and others) at cliffs on the ocean in Santa Cruz weekly, usually in an altitude envelope -70 to +200 feet with no odd behavior on the altitude response to the throttle stick. I was just there (Seacliff State Beach) yesterday.

I launch from a parking lot at the top of the cliffs. Watch this, no weird behavior by the DJI FPV:

Yes, baro height reference to takeoff position. IMO It is not irrelevant to DJI drones for its fly behaviour.
Hover at 120 meter and push craft down, keep down stick to 100% all time.
Notice that, still above IR range, the descend speed will slow down from 5 m/s (mini4pro) to a lower value getting closer to the ground.

Good working drones indeed, no weird down behaviour on RC stick down. Drones with less good function of vision and/or IR height sensing...yes, weird behaviour.

If you see frequently in flight the IR height indicated, see picture, than expext issues.

cheers
JJB

 

[slup]

...Flying at 20 meters baro height...RC down stick and not descending!

DJI has changed how it handles RC down input when flying low with speed. It is now not possible to lower craft flying fast at low heights. This to prevent to enter an unwanted autolanding (0.5 IR height + stick down).

Low heights starts above the IR range, max descend is slowed down from approx 40 meter baro height...

Yes, baro height reference to takeoff position. IMO It is not irrelevant to DJI drones for its fly behaviour.
Hover at 120 meter and push craft down, keep down stick to 100% all time.
Notice that, still above IR range, the descend speed will slow down from 5 m/s (mini4pro) to a lower value getting closer to the ground.

If you see frequently in flight the IR height indicated, see picture, than expext issues.

I really can't say for sure, as you haven't shared any .txt logs yet... but it seems like you mix very different height situations & data from either the VPS or the barometric sensor, where it's normal that different vertical speed behaviours can be expected.

Your said observation that the vertical speed can be lowered even above the VPS sensor distance, & it's there coming from a relative barometric height above HP of approx 40m sounds very odd as that would mean that all descents (from +40m) down into negative heights would be done with a limited vertical speed... haven't seen that occur in any log yet.

Then it is a known fact that the vertical speed can be limited when approaching ground when the drone is within the VPS sensors precision measuring distance (from a VPS reading of 12m for a Mini 4 Pro).



Then we have your last sentence in the last quote above... "if IR readings occur, then expect issues..."

If you see VPS height readings in the app, those will be recorded in the log... in both the OP's incident flight or in @BudWalker test flight, no VPS readings where recorded when the vertical speed was either limited or totally stopped.

 

[Droning on and on...]

Yes, baro height reference to takeoff position. IMO It is not irrelevant to DJI drones for its fly behaviour.
Hover at 120 meter and push craft down, keep down stick to 100% all time.
Notice that, still above IR range, the descend speed will slow down from 5 m/s (mini4pro) to a lower value getting closer to the ground.

Yes, if the ground is there below it. This happens because the ground is in range of the IR ranging sensors, which are rather accurate. When within this range, the detected distance from the IR sensor will be displayed in red, smaller font size, in the lower left in addition to the height value from the barometric sensor.

When the IR sensor is active, the baro sensor is completely ignored.

Similarly, when the drone is not sensing anything below it with the IR sensor, it is allowed to descend below takeoff height without any impact on flight dynamics, behavior, or control. As I said, I fly like this all the time.

Something's definitely wrong with your M4P, but it's not what you seem to think it is.

If you see frequently in flight the IR height indicated, see picture, than expext issues.

If you see the IR sensed AGL, then you're close to the ground (or some surface) and the slowing descent is normal behavior.

If you see the IR AGL displayed and you're more than 50ft above the ground below, your IR sensor is probably defective. The drone certainly is.

None of this operation requires, or pays any attention to the barometric sensor. Insofar as controlling descent to a surface, it is way too inaccurate.

 

[JJB44]

I really can't say for sure, as you haven't shared any .txt logs yet... but it seems like you mix very different height situations & data from either the VPS or the barometric sensor, where it's normal that different vertical speed behaviours can be expected.

Your said observation that the vertical speed can be lowered even above the VPS sensor distance, & it's there coming from a relative barometric height above HP of approx 40m sounds very odd as that would mean that all descents (from +40m) down into negative heights would be done with a limited vertical speed... haven't seen that occur in any log yet.

Then it is a known fact that the vertical speed can be limited when approaching ground when the drone is within the VPS sensors precision measuring distance (from a VPS reading of 12m for a Mini 4 Pro).

View attachment 173890

Then we have your last sentence in the last quote above... "if IR readings occur, then expect issues..."

If you see VPS height readings in the app, those will be recorded in the log... in both the OP's incident flight or in @BudWalker test flight, no VPS readings where recorded when the vertical speed was either limited or totally stopped.

Does the Vision or the IR sensor measures the height below the craft?
Mini4pro IR sensor measurement range: 0.1-8 m.
I think it is the IR sensor, so if that is correct how is it possible that the descend speed is reduced flying higher than 8 meter? (fly craft down from 120 meter down with 5m/s rate of descend, and down speed is reduced well above this 8 meter. I will test flight tomorrow for this, getting curious now ;-)

cheers
JJB

 

[Droning on and on...]

Does the Vision or the IR sensor measures the height below the craft?
Mini4pro IR sensor measurement range: 0.1-8 m.
I think it is the IR sensor, so if that is correct how is it possible that the descend speed is reduced flying higher than 8 meter?

Why are you ignoring the fact that only you are having this problem? The answer to your question lies there.

(fly craft down from 120 meter down with 5m/s rate of descend, and down speed is reduced well above this 8 meter. I will test flight tomorrow for this, getting curious now ;-)

Not with my M4P.

 

[BudWalker]

I've discovered that the .txt log files don't report when Cine mode is in effect. I recall that @Droning on and on... suggested this might be the case. I suspect that the arrested descent issues seen in the @GiannisS flights occurred while the Mini 4 Pro was in Cine mode. Also, the descent anomalies seen in the post #34 test flight are likely due to being in Cine mode.

I was pretty sure that the test flight in post #34 included some Cine mode flight but none was seen in the .txt log file. So I did a test flight that has about 3 minutes Cine mode. The .txt can be obtained here
DJIFlightRecord_2024-03-29_[10-31-06].txt

Cine mode occurs in the interval [38, 218] secs. Full negative throttle is in the intervals 1) surrounding 120 secs and 2) surrounding 210 secs. The pink background indicates P-GPS(Bypass) mode. I guess that includes Cine mode. There is no direct indication of Cine mode - I wrote down the times during the flight.

Cine mode has max descent and horizontal speeds of 6 m/s and 12 m/s respectively. In this flight there appears to be no guarantee that these speeds will be achieved even with full negative throttle and/or full fwd elevator.

I kinda suspect that, while in Cine mode, factors such as wind speed, wind direction and perhaps turbulence will determine if and how much to reduce max descent and horizontal speeds.

 

[slup]

I've discovered that the .txt log files don't report when Cine mode is in effect.

I kinda suspect that, while in Cine mode, factors such as wind speed, wind direction and perhaps turbulence will determine if and how much to reduce max descent and horizontal speeds.

Good, that certainly explains the 3m/s limitation that's seen in both the OP's flight & in your test flight.

This reverts us back to the idea of a wind issue again...

And as Cine is equal to Normal with only a decreased max descent speed (according to the specs). The max horizontal speed is unchanged which means that the max tilt angles should be the same also. This leave us with only a difference of 2m/s in vertical speed... that in the OP's flight placed his drone, due to wind effects, in a consistent situation that perfectly cancelled out those max 3m/s descent, making the drone end up with 0m/s. Wonder if a descent speed of 2m/s had been achieved if the drone had been in Normal mode instead?

I think that the reason is a mix... both from the wind & certain strategies in the firmware. Those consistent 0m/s in the OP's flight, is far too perfect just coming from the wind.

 

[slup]

Hmm... this is from the second flight the OP shared... isn't Cine = Tripod in the log?

 

[BudWalker]

Hmm... this is from the second flight the OP shared... isn't Cine = Tripod in the log?

View attachment 173924

There is no P-GPS(Bypass) or P-GPS(Brake) mode in this log. However, there is P-GPS. I think that means Obstacle Avoidance is turned off. Going to be raining here for next 2 or 3 days. I'll do a test flight when it clears.

 

[BudWalker]

Just heard from @msinger about this. RC:mode should be used - we've been using OSD:flyCState. RC:mode will have the values C, N or S.

One (temporary) caveat. If OA is turned off then RC:mode will have the raw value. E.g. RC:mode = "2" instead of "C". For now use the mapping "2"=>C, "0"=>N, "1" =>S

 

[slup]

...RC:mode will have the raw value. E.g. RC:mode = "2" instead of "C". For now use the mapping "2"=>C, "0"=>N, "1" =>S

So in the first log from the OP... this means he was flying in Sport, & the decent either was totally prevented or limited to 3m/s (6,7mph) where the max is 5m/s?

All looks way too consistent & "controlled" to be only coming from wind effects even though they probably contributed or set this off...

 

[Droning on and on...]

And, as I've pointed out, I descend down through 0ft indicated into negative territory below my launch point almost every time I fly, launching from a plateau with a sheer cliff 70ft above the ocean.

If the M4P was behaving this way, I would certainly notice. When I get a chance, I'll go to Seacliff and do some deliberate tests and post the logs here. I'm contending with the same weather system here in Santa Cruz that @BudWalker is in Arroyo Grande, so it may be a day or two before I can execute.

 

[BudWalker]

And, as I've pointed out, I descend down through 0ft indicated into negative territory below my launch point almost every time I fly, launching from a plateau with a sheer cliff 70ft above the ocean.

If the M4P was behaving this way, I would certainly notice. When I get a chance, I'll go to Seacliff and do some deliberate tests and post the logs here. I'm contending with the same weather system here in Santa Cruz that @BudWalker is in Arroyo Grande, so it may be a day or two before I can execute.

I don't think there is an issue about absolute height. At least AFAIK . Instead all the back and forth has been about descent rate - why it's less than it should be, why it's arrested, etc.

 

[BudWalker]

So in the first log from the OP... this means he was flying in Sport, & the decent either was totally prevented or limited to 3m/s (6,7mph) where the max is 5m/s?

All looks way too consistent & "controlled" to be only coming from wind effects even though they probably contributed or set this off...

View attachment 173941

Yeah, seems that after all the go around about mode we're right back were started from. My head is starting to hurt some. Any suggestions for another test?

 

[slup]

...My head is starting to hurt some. Any suggestions for another test?

... a bit clueless also I'm afraid.

Still suspect the firmware+wind... the question is "what" & how much of "it", that sets it off, but can't figure out a meaningful way to test it.

Brought my old Air1 (I know... another craft & another app...) out yesterday as it was winds up around 10-12m/s & tried, didn't expect it to fail in any way... & it didn't. Instead polished my previous horizontal speed record... managed to take it just over 20m/s while it descended according to spec. from 120m height down to 20m.

 

[Droning on and on...]

I don't think there is an issue about absolute height. At least AFAIK . Instead all the back and forth has been about descent rate - why it's less than it should be, why it's arrested, etc.

That's what I'm talking about. Descent rate. It doesn't slow passing through 0ft above takeoff when the ground below is 70ft further down.

Unless I've misunderstood the @JJB44, he's saying starting at 20ft indicated above takeoff, descent slows even if the AGL of the bird is much greater than 20ft.

If that's not correct, someone clear up what the anomaly is we're discussing.