MA2 dropping after hand launch like a stone

[boblui]

The posted .TXT files do not tell anything. The .DAT file will be needed. You may follow this thread to get the files : Mavic Flight Log Retrieval and Analysis Guide

 

[Oakley75]

I'd post it, these guys can really help with those logs!

 

[Nonprophet]

The OP stated that he flew his MA2 numerous times with the same props without issue, and didn't change or modify them before these two fateful flights, so, it would seem that how the props were installed is not the issue.

 

[MTM]

Can confirm again that it was definitely not a mistaking of propellers positioning. They were exactly where they should be for many flights before. It seemed like the motors were throttling down after the first little push in the air..

I attached the .Dat files which are related to the two flight attempts. Maybe someone can figure out more?

 

[Mel 08]

I don't see how that's even physically possible.

They can be put on the wrong way

 

[Airmaxx23]

They can be put on the wrong way

I'm saying I don't know how it's physically possible for a quad to take off with the wrong prop on it.

If it tipped in the same direction both times it's probably the ESC.

 

[Mel 08]

I'm saying I don't know how it's physically possible for a quad to take off with the wrong prop on it.

If it tipped in the same direction both times it's probably the ESC.

I didn't say it would take off
I said you can put them on the wrong way round

 

[Airmaxx23]

I didn't say it would take off
I said you can put them on the wrong way round

I know but you quoted me responding that the pros can go on the wrong way. My post wasn't regarding props being able to go on the wrong way, I was just saying I don't see how a quad can take off with the wrong prop on. I've edited my original reply to make it more clear for people.

 

[TheRock]

How high up were you? Thin mountain air?

 

[MTM]

How high up were you? Thin mountain air?

Nothing special. Around 1600 meters above sea level.

 

[Starz]

How high up were you? Thin mountain air?

Thin air would not be the issue.

 

[hiflyer201]

Ok so was just thinking in the shower what "my friend" did

I think I know that friend...I've learned quite a bit from him too

 

[boblui]

I have gone through the two .DAT files and my findings are :

case 1 : For unknown reasons, the flight controller did not command the motors to increase the thrust although all sensors indicated that the craft was losing altitude.

case 2 : Some kind of internal problems occurred causing the flight controller to shut down the motors while the craft was still in the air


Case 1 details

The craft hit the ground at the belly 5.05 sec after the motors were started. The shock was about 6.5g so it was quite hard.


All sensors including the IMU, barometer and GPS indicated that the craft was losing altitude prior to the impact :


However, the motors did not increase their speeds to maintain the altitude :


Because the flight controller did not tell them to do so. However, the flight controller did try to correct the craft's attitude ( rolled to one side ) after the impact :


Nothing unusal was seen in the event log. All were just completion of takeoff, home point update, etc.




Case 2 details

Impact occurred at 4.47 sec. The craft hit the ground at the nose before coming to rest upside down as reported by the OP. As the craft dropped from a lower height and the props have probably cushioned the impact, the shock was lower ( 2.6 g )


The motors were turned off by the flight controller just before the impact :



The event log shows that the flight controller was not happy with the takeoff. It is noticed that the craft was not level but tilted by about 19 degrees prior to takeoff. Not sure if it has anything to do with the event.

 

[MTM]

Impressive Analysis Boblui! Thank you a lot for your time and effort!
What do you think was the cause for all that? Pilot error - which I would doubt from my side as the pilot (especially in Case 2 since I was starting from the ground) or did the transmission between remote and Drone not work properly? Was it interfered? I am still full of question marks..

 

[boblui]

What do you think was the cause for all that?

In both cases, the flight controller behaved abnormally so my best guess is that some software glitches have caused the crash. I still find it quite hard to believe because it happened two times consecutively. Anyway, there is a high chance that DJI will replace or repair it for free as it was definitely not pilot error.

 

[Juggler]

I think I know that friend...I've learned quite a bit from him too

trouble is he keeps teaching me...bugger

 

[Repaid1]

I have seen reports of this over a few years on other DJI. Nothing implied to the OP, but the cause was a bit of operator error on hand launch. People were pulling their hand away right at prop throttle up, instead of a quick blip hard on throttle and going up and establishing a hover. As such the aircraft didn't know it was airborne and didn't throttle to hold height. Doesn't sound like the case here, but that is the closest I saw the behavior in past.

In Practice I always "Boost" up 2 foot from hand launch to ensure aircraft is free/clear of my head, I have seen people "milk" it up on throttle, which doesn't seem like the best practice IMHO.

 

[Tufargon]

I have seen reports of this over a few years on other DJI. Nothing implied to the OP, but the cause was a bit of operator error on hand launch. People were pulling their hand away right at prop throttle up, instead of a quick blip hard on throttle and going up and establishing a hover. As such the aircraft didn't know it was airborne and didn't throttle to hold height. Doesn't sound like the case here, but that is the closest I saw the behavior in past.

In Practice I always "Boost" up 2 foot from hand launch to ensure aircraft is free/clear of my head, I have seen people "milk" it up on throttle, which doesn't seem like the best practice IMHO.

Thank you. Something I will definately keep in mind. It makes total sense.

 

[Juggler]

I have seen reports of this over a few years on other DJI. Nothing implied to the OP, but the cause was a bit of operator error on hand launch. People were pulling their hand away right at prop throttle up, instead of a quick blip hard on throttle and going up and establishing a hover. As such the aircraft didn't know it was airborne and didn't throttle to hold height. Doesn't sound like the case here, but that is the closest I saw the behavior in past.

In Practice I always "Boost" up 2 foot from hand launch to ensure aircraft is free/clear of my head, I have seen people "milk" it up on throttle, which doesn't seem like the best practice IMHO.

Yep agree mentioned that in post 19..

 

[Repaid1]

Yep agree mentioned that in post 19..

As I read yours, you were still talking about props on wrong (Flags)? Mine is more not giving the drone time to know it is actually flying. One can see the affect if you rev motors on a ground take off, drone doesn't automatically engage flight mode. I believe the barometer must sense a bit of change, but how much change I have no idea. That's why I purposefully send that sucker skyward