unable to land!

[John Hennessy]

I had my first encounter with power lines today. Fortunately my M4P wasn't totally disabled. I wasn't absolutely sure that I had clipped the lines, and my little bird kept on flying. I flew probably another 4km after that and then returned home. When I tried to land it came down to within 6 inches of the ground (the same area of bitumen that I took off from) and refused to land! It would only hover , maybe as close as 1 inch from the ground, whilst holding the stick down all the time. After about 6 attempts of rising and landing (I thought that I would have to just completely drain the battery!) it finally decided to land! On inspection I found that 2 of the props were damaged to the point that there was about half an inch missing from them! I was soooo glad that it actually made it home! After doing my first prop replacement, I tested take off, landing, several manoeuvres and everything was fine. I am still unsure of why it wouldn't land with the damaged props. Does anyone have any thoughts?

 

[old man mavic]

@John Hennessy Hi John i would say that because the props were damaged ,then the IMU was getting different readings from the ESC's on the motors with the damaged props, and this made the drone unstable ,to the point where it could have flipped over on landing, it was the landing protection programmingthat was conflicted

 

[Droning on and on...]

To expand on what @old man mavic said, the arms with the missing prop portions would have to spin at significantly higher RPM than the other motors to produce the same lift. This is detectable by the Flight Controller, which can sense RPM and controls it constantly to maintain attitude and execute flight commands.

As OMM said, it was probably outside some configured range that has been programmed to be safe for landing.

What's remarkable is the drone still flew, under control. A testament to DJI engineering.

 

[John Hennessy]

@John Hennessy Hi John i would say that because the props were damaged ,then the IMU was getting different readings from the ESC's on the motors with the damaged props, and this made the drone unstable ,to the point where it could have flipped over on landing, it was the landing protection programmingthat was conflicted

Thanks OMM, I knew that someone here with far greater knowledge than I would have an explanation. I've only been flying for about 8 months, but Yesterday I learned a valuable lesson in regard to power lines!

 

[John Hennessy]

To expand on what @old man mavic said, the arms with the missing prop portions would have to spin at significantly higher RPM than the other motors to produce the same lift. This is detectable by the Flight Controller, which can sense RPM and controls it constantly to maintain attitude and execute flight commands.

As OMM said, it was probably outside some configured range that has been programmed to be safe for landing.

What's remarkable is the drone still flew, under control. A testament to DJI engineering.

Thanks for that, and yes, the amount of technology built into these little things never ceases to amaze me. Immediately after what I assumed was contact with the lines, I paused and hovered, at which time the drone appeared to slowly lose height. After several "stick up" attempts the drone started to act normally. After this I continued to fly about 3km before returning home. When I saw the damaged props I was truly amazed that my little mate got home at all!

 

[Dbez1]

It’s a well known fact that power lines and small branches have an uncanny ability to reach out and grab an unsuspecting drone. I’m glad yours is okay.