Hey guys,
So I ran into a very strange issue in one of my flights. I was bringing the drone back from a hyperlapse and I noticed it was descending very slowly. As I got the drone above me and wanted to bring it straight down, it just refused to come down. I was holding the left stick all the way down and nothing. The weather was perfectly clear, cloudy (no direct sunlight to trigger any sensors), no fog, nothing, perfect conditions. The drone was 15-20m above my head and was just refusing to come down. Every couple seconds the message saying "area unsuitable for landing" would popup and then immediately disappear on its own. I eventually managed to bring it back by flying forward and backwards while keeping the left stick down, this allowed it to descend, but still way slower than it normally would.
After looking at the log (screenshot attached), it seems like the "sonar altitude" (I assume the bottom sensors?) was seeing some obstacle, altough there was nothing there. The most concerning part is that, even though it was seeing itself at ~1m altitude, it was not initiating landing, despite me holding down the left stick for seconds on end. Coupling that with the fact that I was getting very low on battery (I was doing a hyperlapse and I was trying to get it as long as possible so I only started bringing it back at 13-14% since the drone was very close to me, 150m distance and 70m altitude), it was quite a stressful situation, I was really concerned it was eventually just gonna drop out of the sky as it runs out of battery. Or at the very least, drag the battery all the way to 0% and potentially damage it.

Anyone know what could have triggered that? Anything better I could have done except flying forwards and backwards? It seems to me like DJI really needs to add an option in the Fly app to disable those sensors.

I swapped batteries and sent it back up immediately to investigate the issue and all was normal. I messed around for an entire battery without being able to replicate the issue, in the same exact spot.

Very strange behavior.  I have never experienced that type of issue.  Since you tried to replicate the issue and couldn't makes it even stranger.  

What version of FLY App?  What controller?  and what version of Firmware in Drone/Controller?

Fly_Hazr_Air Posted at 4-13 05:19
What version of FLY App?  What controller?  and what version of Firmware in Drone/Controller?

standard controller, latest everything else, iOS. Seems strictly a downward sensor error to me and the firmware failing to handle it. I really don't understand why in GO4 they had the option to disable the sensors and in Fly they don't. If not anything else, the drone should *always* descend when the stick is held down for seconds on end, regardless of what the sensors are saying.

it seems like the "sonar altitude" (I assume the bottom sensors?) was seeing some obstacle, although there was nothing there.
It's an issue I've seen in flight incidents a number of times.
There are a couple of possibilities.
Is there any accessory blocking the downward view of the sensors?
Were you flying over snow with bright sun reflecting off it?
If not, try cleaning the sensors and recalibrating them and do a test flight and check the data to see if it's fixed.

Hi Ice,

If you like post your flightlog on here.

With the bottom sensor 'seeing' 0.5-0.6 meter (even flying baro height "high"), it should go into a autolanding wich is indeed very slow.
Your screenshot going down from 19.3 to 18.2 meter....so it did descend.Check up of your screenshot data where the VPS height is 0.5 and not in autolanding with 100% down stick.  ;-)

JJB

Did you try flipping to sports mode to see if that would change its behavior?

I would try turning off obstacle avoidance and see if that "fixes" the problem  At the least it will diagnose what is causing it if it lands without a problem.  Honestly I have had some irregular behavior like this before but usually when the aircraft is over the pool and there are lots of obstacles around.   Does it do this in other areas?  Perhaps try going to a nearby park and see if the problem no longer is there.  Again this points to an issue with the landing site if it lands just fine elsewhere.

Dirt or condensation on the sensors or labroids third party accessories.

David.Battle Posted at 4-13 06:44
I would try turning off obstacle avoidance and see if that "fixes" the problem  At the least it will diagnose what is causing it if it lands without a problem.  Honestly I have had some irregular behavior like this before but usually when the aircraft is over the pool and there are lots of obstacles around.   Does it do this in other areas?  Perhaps try going to a nearby park and see if the problem no longer is there.  Again this points to an issue with the landing site if it lands just fine elsewhere.

Hi David,

Disable OA on a MA2 does not disable the bottom sensor, wish it was possible in the fly-app to disable this sensor as well.

cheers
JJB

Labroides Posted at 4-13 06:06
it seems like the "sonar altitude" (I assume the bottom sensors?) was seeing some obstacle, although there was nothing there.
It's an issue I've seen in flight incidents a number of times.
There are a couple of possibilities.

Yes, there was snow on the ground but the weather was very cloudy and right before sunset, hardly a strong light environment.
No accessories (except Master AirScrew props), drone is stock. Sensors looked perfectly clean, I inspected them after eventually landing it. I'll try a recalibration (I assume that's done with the Assistant app, I've never done it before)

JJB* Posted at 4-13 06:33
Hi Ice,

If you like post your flightlog on here.

That's true, it was coming down, 1m in 10s. If I were at 120m, I'd be in serious trouble I'll upload the flight log.

KlooGee Posted at 4-13 06:43
Did you try flipping to sports mode to see if that would change its behavior?

Yup, no change

David.Battle Posted at 4-13 06:44
I would try turning off obstacle avoidance and see if that "fixes" the problem  At the least it will diagnose what is causing it if it lands without a problem.  Honestly I have had some irregular behavior like this before but usually when the aircraft is over the pool and there are lots of obstacles around.   Does it do this in other areas?  Perhaps try going to a nearby park and see if the problem no longer is there.  Again this points to an issue with the landing site if it lands just fine elsewhere.

Tried both turning sensors off and switching to S, no effect.

hallmark007 Posted at 4-13 07:21
Dirt or condensation on the sensors or labroids third party accessories.

No dirt or condensation visible, at least not from the outside.

Ice_2k Posted at 4-13 07:39
That's true, it was coming down, 1m in 10s. If I were at 120m, I'd be in serious trouble  I'll upload the flight log.

yep, saw once data from a SA guy, flying really high and just enough juice to land safely!

If in autolanding enter 100% UP stick quicky (stops the autolanding) and 100% down again, if the bottom sensor that time does not see 0.5 meter than it will go down normally.
In your screen shot i see 0.7 and 0.8 meter, so this does the trick.

cheers
JJB

JJB* Posted at 4-13 07:46
yep, saw once data from a SA guy, flying really high and just enough juice to land safely!
If in autolanding enter 100% UP stick quicky (stops the autolanding) and 100% down again, if the bottom sensor that time does not see 0.5 meter than it will go down normally.
In your screen shot i see 0.7 and 0.8 meter, so this does the trick.

https://app.airdata.com/share/Rxbgvd

Ice_2k Posted at 4-13 07:51
https://app.airdata.com/share/Rxbgvd

Interesting....

Your Autolanding was because of critical low battery, not by 0.5 meter VPS height and 100% down stick. (this will command a ForceLanding ; my mistake)

This autolanding was really slow, guess beacuse VPS height was measuring false height of 1.2 meter.
The autolanding protection uses VPS height as well, it will slow down the last part of a normal landing.
(try Sport mode 30 meters height and 100% down all the way!   drone will slow down in reach op bottom snesor and wil stop at 0.5 meter with still 100% stick down)

You cancelled the autolanding but now 0,6 meter VPS height into a forcelanding!
(autolanding = black, forcelanding = fuchsia)
I am afraid that in autolanding with false VPS height readings, landing speed is slow. Nothing you can do about that! **
** well, land before critical batt value  ;-)

cheers
JJB

so you're saying that if it weren't for the critical battery warning, this wouldn't have happened?

the message saying "area unsuitable for landing" would popup

I had a few (2-3?) similar incidents this winter in low temperatures and high humidity conditions. I don't think I had critical low battery as I try to land with at least 15% in lower temperatures, but MA2 refused to land with area unsuitable for landing message, despite howering over landing pad or dry concrete. In my case I was able to land a few feets next to the "unsuitable" place or palm land and I haven't noticed speed change during aproach to landing area (manual aproach for landing in P or T mode)...

Ice_2k Posted at 4-13 08:18
so you're saying that if it weren't for the critical battery warning, this wouldn't have happened?

hi,

Yes, for the part of the autolanding ofcourse.

If you lowered your drone with 100% stick down AND the VPS height that time was measuring false height of 0.5 it went unwanted into a forcelanding mode flying at 18 meters.
If you had your stick down, let say 70%, and VPS height false reading <> 0.5 meter, it had decend normally with that stick setting.

A forcelanding like this at baro height 'high' is cancelled with 100% up stick momentarily, after that normal descend is possible as long as the combi 100% stick down AND 0.5 VPS height is not met.

cheers
JJB

JJB* Posted at 4-13 10:36
hi,

Yes, for the part of the autolanding ofcourse.

Aha, I see. So low VPS reading + 100% stick down is interpreted as “land”. If I canceled landing and then use just say 70% stick down, it might have descended, despite VPS reporting low altitude?

Ice_2k Posted at 4-13 10:42
Aha, I see. So low VPS reading + 100% stick down is interpreted as “land”. If I canceled landing and then use just say 70% stick down, it might have descended, despite VPS reporting low altitude?

yes!

Others have lost their drone due to this....if you fly forward and low (some do over water...) and you want to fly even lower that 0.5 meter above water....first little down stick does not do anything, so more stick...up to full stick  OMG  into forcelandig    UP DOWN stick mid position, drone will continue to land!!

splash....

I asked many times to change this in DJI software, DJI don`t listen!  Nobody wants to land their craft flying 9 m/s forward...

Try this  :  hover close to you at 0.5 meter height, apply stick down....notice that it will not go down immediately, after short moment it will    a forcelanding controlled by the VPS height sensor to land slowly.

cheers
JJB

Thanks buddy!

Ice_2k Posted at 4-13 07:40
Tried both turning sensors off and switching to S, no effect.

Tried both turning sensors off and switching to S, no effect.
That's because it was the downward facing sensors that caused the problem with the false sonar height, not the obstacle avoidance sensors which face forwards.

Hello there Ice_2k. I am sorry for the trouble this has caused and thank you for reaching out. In addition to this post the Downward Vision System works best when the said DJI drone is at an altitude of 0.5 to 30 m. If the altitude of the said DJI Drone is above 30 m, the Vision Sensor may be affected, so extra caution is required. Thank you.

Labroides Posted at 4-13 16:14
Tried both turning sensors off and switching to S, no effect.
That's because it was the downward facing sensors that caused the problem with the false sonar height, not the obstacle avoidance sensors which face forwards.

Yeah, I know, but when you semi-panic and don’t know what else to do, you try everything

DJI Stephen Posted at 4-13 19:28
Hello there Ice_2k. I am sorry for the trouble this has caused and thank you for reaching out. In addition to this post the Downward Vision System works best when the said DJI drone is at an altitude of 0.5 to 30 m. If the altitude of the said DJI Drone is above 30 m, the Vision Sensor may be affected, so extra caution is required. Thank you.

[view_image]

Hi Stephen. As i said (and it’s visible from the logs I posted) the drone was about 18-19m high but the downward sensors for some reason were reporting less than 1m.

JJB* Posted at 4-13 07:27
Hi David,

Disable OA on a MA2 does not disable the bottom sensor, wish it was possible in the fly-app to disable this sensor as well.

Good to know.

Ice_2k Posted at 4-13 07:38
Yes, there was snow on the ground but the weather was very cloudy and right before sunset, hardly a strong light environment.
No accessories (except Master AirScrew props), drone is stock. Sensors looked perfectly clean, I inspected them after eventually landing it. I'll try a recalibration (I assume that's done with the Assistant app, I've never done it before)

No accessories (except Master AirScrew props), drone is stock.

What is your experience with MA props? I have a set but wasn't able to test them in flight...

virtual Posted at 4-26 00:01
No accessories (except Master AirScrew props), drone is stock.

What is your experience with MA props? I have a set but wasn't able to test them in flight...

Not great. First, it took 1.5 months to actually ship the props and then another month on route. They sent a set that was just awful. Badly finished, unbalanced, basically all the issues that later also surfaced online. After many emails I finally got them to reply and to send replacements. I pointed out that I paid 24% tax on these and they should mark the replacements as being replacements, not as a separate product. They of course ignored me so I paid 24% again. The next ones were much better and pretty much did what they were supposed to do (look pretty and be less noisy).
Now I switched to the Air 2S and they don't work for it so I'm back to stock props.

Hi Ice_2k,
I've had this exact behavior with my Mavic 2 Zoom (and I still have it randomly from times to times) as explained in this topic, yet it's still a mistery and unresolved : https://forum.dji.com/forum.php?mod=viewthread&tid=217600
I haven't reached out to DJI Support, mainly because I don't want to pay an extra for a problem I can just go through by disabling the VPS, but I'll let you know if I find anything somehow

Ice_2k Posted at 4-26 02:03
Not great. First, it took 1.5 months to actually ship the props and then another month on route. They sent a set that was just awful. Badly finished, unbalanced, basically all the issues that later also surfaced online. After many emails I finally got them to reply and to send replacements. I pointed out that I paid 24% tax on these and they should mark the replacements as being replacements, not as a separate product. They of course ignored me so I paid 24% again. The next ones were much better and pretty much did what they were supposed to do (look pretty and be less noisy).
Now I switched to the Air 2S and they don't work for it so I'm back to stock props.

Similar experience here - very long proccesing time (despite "in stock" status on website) and long shipping time but my set of props looks OK. Ordered black props (less than 22Euro) so I wasn't charged for VAT but I have to install them to find if they make less noise. I was considering red ones to improve visibility but these were out of stock...