Please help wacky landing (logs)

[JackH]

All my previous flights were daytime (about 20 flights) and everything went fine so I tried my 1st night flight yesterday. The day before this, I did do a IMU calibration and then at the flight site I also did a compass calibration. Everything went normal.

So after a normal through preflight, I took off and the flight went perfectly normal. The problems started when I go to land. I always do manual landing so I can set her down very gently. But this time when I got down to about 2 feet , the P4 started bouncing up and down and it just didn't want to land. I pushed it up to 6 feet and hovered (it was steady), while I thought about what to do. I switched the RC to F mode and tried again with the same result. So now I figured it was the VPS going crazy, so I go back to P and went through with the landing. With it bouncing, I did my best to set it down at which it ended up on it's side. Left stick down would not cut power after it was on the ground, so I get warnings of motor rotation blocked (something like that) which is because the P4 was on it's side and 2 props were jammed, the other 2 spinning. I finally did a CSC and shut it down.

No damage to anything as I landed on grass. Now this log is the second flight which I did right after. It is short because I just took it off and quickly landed just to test again. And the P4 acted the same way. Upon landing it also fell on its side.

Please give me your thoughts why this all happened. This is my first crash (sort of) and I really need to figure this out. My guess is the VPS system took a dump for some reason, although I also see negative altitude numbers all of a sudden. Why is that??

 

[r62ewa]

There have been recent posts regarding this 'bouncing' while landing behaviour and I recall one individual did VPS calibrations through the Assistant 2 software and they fixed his issue.

Also, if you are comfortable, if the Phantom hovers steady at 6 feet you can always do a hand catch to avoid the dangerous landing in those types of situations.

 

[WWK888]

I agree, hand catch and eliminate the problem until you figure out what is causing it. I hand catch all the time, it is easier and you avoid potential tip overs and getting dust and debris in your motors.


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[JackH]

good idea about hand catch, i will do it next time.

I will calibrate VPS as well. Never tried it, but I will go through it.

Thank you for the ideas.

 

[GMack]

I wonder since DJI Assistant 2 uses black and white checkerboards as the adjustment target for the front and bottom cameras, if a landing pad that also uses that checkerboard pattern might make for a better landing? I know they mention some bad landing surfaces that might confuse the sensor (tall grass, wet areas, etc.) so maybe a checkerboard helipad would be a better bet for a smoother landing.

 

[JackH]

I will say this is also the first time I landed on grass. Usually I land on dirt or pavement.

 

[JackH]

FYI, I just did another test fly on grass (daytime). This time everything was completely normal. Landing with no bounce. Used the same location, the only change was that I did the VPS calibration. All is back to normal.

Next time I will test at night to be sure it had nothing to do with night time.

 

[r62ewa]

Good to hear.

 

[GMack]

FYI, I just did another test fly on grass (daytime). This time everything was completely normal. Landing with no bounce. Used the same location, the only change was that I did the VPS calibration. All is back to normal.

Next time I will test at night to be sure it had nothing to do with night time.

Cool!

Fwiw, my second bum P4 that went back to Best Buy would not calibrate with the lower camera/sensor with DJI Assistant 2. Don't know why, but something like that might explain bad and wavering landings. Third calibrated like a charm.

I read something yesterday that said 64% of drone crashes were due to fault tech. Here: Tech Issues, Not Idiot Pilots, Cause Most Drone Crashes This VPS might be one of the "tech issues and not pilot error.

Mack

 

[apollopark]

I had this same problem after my update and calibrations.. but when I went to take of the thing was bouncing up and down 2 ft off the ground. It was the craziest thing, I swear the last update screwed so many things up on my bird. Signal is now at poor all the time where normally always had good signals.

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