DJI Drone Help Forum

Spark forced landing


#1

On a few occasions recently my Spark has unexpectedly crash landed. Looking at the flight logs, they show ‘forced landing’. Is there any explanation for this?


#2

Upload your log to the link below and place a link back here to that, and we may be able to answer your question. If you have already uploaded, just link that back here.

Phantom Help Log Viewer


#3

http://www.phantomhelp.com/LogViewer/O2HYLWPJJEAOKL9A5BY2/


#4

Not being that familiar with the Sparks operation at low altitudes, I will copy this to @msinger and see if he can give you a better explanation. It does have to do with the downward sensors I believe. Whether this is normal for the Spark to autoland when under 9 meters for xxxx priod of time I can’t say for certain. Below is a refernce from your data.


#5

Thanks for looking. This has happened on a number of occasions recently.


#6

How do “forced landing” and “auto landing differ”? Never saw forced landing posted in the many logs posted on forums.


#7

They are similar, but occur for different reasons. Auto landing, generally speaking you can cancel, depending on the circumstances. Forced landing you cannot cancel. As I said, the scenarios will differ but they are similar.


#8

The Spark switched to Forced Landing mode because you had the throttle in the full down position while the downward sensors were detecting the ground was near (even though it wasn’t). That combination normally only happens near the ground.

Do you have any accessories installed on your Spark? Perhaps something that could hang below the bottom of the Spark?


#9

Don’t suppose that being less than 50ft from the Home Point would have anything to do with the autoland do you? The throttle theory doesn’t make any sense to me, although it does seem to be sensor related. If the Spark had Precision Landing enabled, maybe that distance , plus the altitude and VPS could be related to the autoland. ??


#10

Well, that’s how the Forced Landing feature works. When the drone is close enough to the ground and the pilot is attempting to descend to the ground, the drone takes over (auto initiates Forced Landing) and lands itself.

How does the drone know it’s near the ground? It uses the reading from the downward sensors. Normally it’s correct, but it can trigger a false positive if something like extended landing gear is installed below the drone.


#11

Many thanks for these helpful responses. Yes, I did have extended landing gear attached to the Spark, so will fly without it and check that the problem doesn’t reoccur.


#12

This part is pretty obvious. It was the throttle portion that did not make any sense. If that is the the way it works, then that is the way it works. Still doesn’t make any practical sense though. More of an annoyance than anything else. If you were attempting to fly a low level flight and needed to reduce altitude somewhat. Why on earth would it force an autoland? I suppose in that scenario you would need to turn off the VPS. Personally, I never use it anyway. If it can be turned off on the Spark, that would remedy the OP’s issue.


#13

The Landing Protection feature prevents the aircraft from slamming into the ground when the pilot is landing. When the throttle is in the full down position (the pilot is trying to land) and the downward sensors detect the ground is near, the aircraft automatically takes over and finishes descending until the aircraft is on the ground.

Unfortunately, it cannot be disabled when flying a Spark.

Forced Landing mode is not initiated until the downward sensors detect the ground is within about 1.5 feet away. So, this scenario would likely never happen.


#14

Take these numbers with a grain of salt. You really have to give a bit of tolerance to the actual altitudes. But this is a small change to the above graph. You can see the altitude at the first full down throttle and the VPS was active within the window. The second one was not. The third one was and initiated the force landing. The first down throttle was at ~ 3.1 ft, and no force landing was initiated. On the third down throttle at ~2.7 ft, Force landing initiated. Roughly 3 ft appears to be the activation point of the VPS in this instance. Well above the 1.5 ft.
In theory if the extended gear were a contributing factor, you would see more variation in the active points. Those are my thoughts on the subject anyway. Not a big deal really, because the end result is basically the same.


#15

I’m not seeing this data in the flight log.

At 2m 32s, the throttle was moved to the full down position while the VPS altitude was within range. That didn’t trigger Forced Landing since the throttle wasn’t held down long enough.

Data1


At 2m 35.8s, the throttle was held down long enough for Forced Landing to be triggered.

Data2


#16

I found a calculation error for the altitude. Off by a factor of 100. ( My fault, misplaced decimal point ). The corrected chart is below. I am curious as to the time factor of keeping the throttle at full down. The VPS was way off, but that still shouldn’t cause a force landing. In this case, it was active and the throttle was only held down for 700 ms. I suppose one could round that off to 1 second for informational purposes, but in actuality it is a bit shorter in duration. I guess that is one to put back in your memory bank for future use if needed.