Drone Going into Landing Mode

[bigswifty]

Hey guys, I was flying my MA2Z at the edge of a hill the other day and was trying to fly “down” the hill, which meant flying several metres below my “Home” altitude. Every time I tried to descend, the drone would go into Landing Mode and start to descend. No biggie, easily and safely cancelled, but was frustrating. I presume there is a setting which disables this but I can’t seem to find it.

Any clues would be great!

 

[boblui]

What was the height of the craft above the ground when autolanding started ? Can you post the flight log file in the phone or upload it to PhantomHelp / AirData ?

 

[Meta4]

Any clues would be great!

Your flight data will probably point to the issue.
Without seeing it, I'd guess it has something to do with descending while the VPS is detecting the ground close below?
If that's the issue, switching off the VPS sensors would fix things for you.

 

[bigswifty]

Log Files Attached, grateful for any help.

 

[boblui]

..... Every time I tried to descend, the drone would go into Landing Mode .....

The flight logs indicate that the unexpected autolanding has happened 9 times and in all occurrences, the craft was just 0.5 meter above the ground / vegetation beneath it and the throttle stick was held fully down for more than a second. It's normal behavior.

 

[bigswifty]

The flight logs indicate that the unexpected autolanding has happened 9 times and in all occurrences, the craft was just 0.5 meter above the ground / vegetation beneath it and the throttle stick was held fully down for more than a second. It's normal behavior.

Agreed about the down stick. I was trying to get the drone to descend.

Basically I was flying the drone down a steeply falling slope. The drone was least 5 metres above the terrain where it was hovering. But each time the drone got to within 0.5 metres of the altitude of the take-off point it went into landing mode. So I'm still very confused about this.

Looking at one entry in the log.......

12m 47.9s

Confirm Landing

15

-0.4m

0.6m

0km/h

116.9m

the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct, the drone was slightly below the altitude of the take off point. But it was definitely higher above the current terrain than 0.6m. So I'm confused by this.

Thanks for taking the time to look, appreciate it.

 

[Otisangb]

Agreed about the down stick. I was trying to get the drone to descend.

Basically I was flying the drone down a steeply falling slope. The drone was least 5 metres above the terrain where it was hovering. But each time the drone got to within 0.5 metres of the altitude of the take-off point it went into landing mode. So I'm still very confused about this.

Looking at one entry in the log.......

12m 47.9s

Confirm Landing

15

-0.4m

0.6m

0km/h

116.9m

the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct, the drone was slightly below the altitude of the take off point. But it was definitely higher above the current terrain than 0.6m. So I'm confused by this.

Thanks for taking the time to look, appreciate it.

Hi Bigs,
what kind surface was the ground, vegetation? The bottom sensor can be fooled. I was flying over my garden and the bottom sensor (inferred) gave inaccurate height readings. Same thing over water. If you had landing protection on and were trying to descend (down throttle) the ac would go into landing mode. If you can see your drone in relation to the ground and know that you have enough height turn off the landing protection and you will be able to lower without going into landing mode. I'm still new at this so will await others response.

 

[Meta4]

Basically I was flying the drone down a steeply falling slope. The drone was least 5 metres above the terrain where it was hovering. But each time the drone got to within 0.5 metres of the altitude of the take-off point it went into landing mode. So I'm still very confused about this.

Looking at one entry in the log.......

12m 47.9s

Confirm Landing

15

-0.4m

0.6m

0km/h

116.9m

the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct, the drone was slightly below the altitude of the take off point. But it was definitely higher above the current terrain than 0.6m. So I'm confused by this.

One thing that's confusing you is comparing the barometric altitude with the VPS altitude.
The baro altitude is approximately the height of the drone above or below the launch point, not the terrain below the drone.
It's approximate because it's common to see a small drift in the barometric sensor over the time of a flight.
The VPS height is an accurate measure of how high the drone is above whatever is below it.

For the numbers you were comparing above, the drone was 115 metres from the home point and the ground level there was about 15 metres lower.
I note that you've updated the home point a few times through the flight (and wonder why?).
Updating the home point does not reset the zero height that was recorded at power up.

The height of the drone relative to the launch point has no effect on the forced landings you encountered.
It makes no difference if you were 100 metres above or below the launch point.
What matters is the VPS sensors were detecting that the drone had something very close below the drone(it makes no difference whether it's land or treetops).
And when the VPS sensors detect that and you continue to hold the left stick full down, that puts the drone in Forced Landing Mode.

Here is the relevant flight data for one of these events.
The green highlights show you holding the left stick full down.

 

[Otisangb]

But it was definitely higher above the current terrain than 0.6m

Do you have an estimate by how much higher?

Meta gave a great display of the data and reasoning. The issue I see is that bugs physically saw that the aircraft was higher than the represented vps data. Bad calibration on the VPS, reflections, lighting, etc? I definitely need to do some experimenting when the wind calms down here.

 

[Meta4]

Do you have an estimate by how much higher?
The issue I see is that bugs physically saw that the aircraft was higher than the represented vps data.

He said the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct .
I don't see how he could tell a difference of 0.2 metres (8 inches) from 300 feet away and suspect a misunderstanding of the ways altitude is measured was the problem.

 

[boblui]

Agreed about the down stick. I was trying to get the drone to descend.

Basically I was flying the drone down a steeply falling slope. The drone was least 5 metres above the terrain where it was hovering. But each time the drone got to within 0.5 metres of the altitude of the take-off point it went into landing mode. So I'm still very confused about this.

Looking at one entry in the log.......

12m 47.9s

Confirm Landing

15

-0.4m

0.6m

0km/h

116.9m

the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct, the drone was slightly below the altitude of the take off point. But it was definitely higher above the current terrain than 0.6m. So I'm confused by this.

OK, I checked the 3D flight path again in Google Earth and found that the craft was indeed well above the ground when these four consecutive forced landing happened ( the 4 purple bars ) :



Google Earth :



It is noticed that the IR height sensor readings were very noisy during this period. Either something in the air ( usually fog ) is confusing the sensor or the sensor has got some problems.

 

[Otisangb]

OK, I checked the 3D flight path again in Google Earth and found that the craft was indeed well above the ground when these four consecutive forced landing happened ( the 4 purple bars ) :

View attachment 114765

Google Earth :
View attachment 114766

It is noticed that the IR height sensor readings were very noisy during this period. Either something in the air ( usually fog ) is confusing the sensor or the sensor has got some problems.

Thanks bobui,
That's what I was getting at. I was assuming the sonar sensor being refered to previously was the ir sensor. I am not positive but I believe the barometric sensor is not used in landings.

 

[boblui]

Thanks bobui,
That's what I was getting at. I was assuming the sonar sensor being refered to previously was the ir sensor. I am not positive but I believe the barometric sensor is not used in landings.

I am not sure whether the barometer is used during but certainly the IR sensor is the primary means for height detection during forced landing.

 

[boblui]

In this occurrence of forced landing. The craft was not moving ( VelH = 0, the green line ) and the barometer readings indicated that the craft was maintaining it's altitude but all of a sudden, the IR sensor reading changed from out-of-range ( > 11m ) to 0.5m in no time. The reading also became rather noisy. Seems to be a signature of the problem. I think there is something wrong with the IR sensor.

 

[Otisangb]

In this occurrence of forced landing. The craft was not moving ( VelH = 0, the green line ) and the barometer readings indicated that the craft was maintaining it's altitude but all of a sudden, the IR sensor reading changed from out-of-range ( > 11m ) to 0.5m in no time. The readings also became rather noisy. I think there is something wrong with the IR sensor.

View attachment 114768

Awesome chart. You made it very understandable.

 

[bigswifty]

Thank you! I was not imagining things Clearly I need to do some test flights. Appreciate your time and analysis.

In this occurrence of forced landing. The craft was not moving ( VelH = 0, the green line ) and the barometer readings indicated that the craft was maintaining it's altitude but all of a sudden, the IR sensor reading changed from out-of-range ( > 11m ) to 0.5m in no time. The readings also became rather noisy. I think there is something wrong with the IR sensor.

View attachment 114768

 

[bigswifty]

He said the Sonar Alt of 0.6m is way wrong. The Baro of -0.4m is correct .
I don't see how he could tell a difference of 0.2 metres (8 inches) from 300 feet away and suspect a misunderstanding of the ways altitude is measured was the problem.

Home point was 300 feet away. *I* was right next to the drone. We were walking along with it And I was resetting home to appropriate places as we moved about on the terrain.

 

[Meta4]

Home point was 300 feet away. *I* was right next to the drone. We were walking along with it And I was resetting home to appropriate places as we moved about on the terrain.

Here's what that flight data looks like: DJI Flight Log Viewer - PhantomHelp.com

If you look at the times you reset the home point, (0:04.7, 6:10.7 & 12:58.7), you see that, the horizontal position of the recorded home point changes.
But the zero height still refers back to the spot where the drone was launched.

Whether there's a problem with the VPS sensors or not, simply disabling the VPS sensors would eliminate the issue you are asking about.

 

[bigswifty]

Whether there's a problem with the VPS sensors or not, simply disabling the VPS sensors would eliminate the issue you are asking about.

Appreciate it, thanks for that. Cheers.