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I'm a relatively new, certificate holding, remote pilot and I just experienced my first crash. I'm hoping those with more experience can give insight as to possible causes so I can learn from this mistake and move on. The DJI Phantom 4 fell from and altitude of 300 feet AGL and appears to be a total loss. Fortunately we did purchase insurance so things could be worse!

Weather conditions were  generally favorable with very light wind (<5mph), great visibility (10 mi.), moderate temperature (85 degrees F), and moderate humidity (66%). I was descending from 395 to 311 feet AGL and rolling simultaneously to keep my subject in the camera frame. Immediately prior to entering an uncontrolled barrel roll and free fall, the drone was moving horizontally at 27 mph and vertically at 11 mph. This is a maneuver I had done multiple times. No setpoints were adjusted that would have permitted me to operate the drone in any manner outside of its default functionality. No warnings or alarms were present. The compass was operating normally and did not need calibrating (per the app). The drone had 6 hours of flight time on it and was still in "new" condition prior to the crash.

The only thing I can come up with is that the 100% descend and 100% pitch, coupled with the moderately humid air caused the drone to lose lift. I suspect operator error on my part, but feel like I was operating the drone as its designed to do and had no indication that I was performing an unsafe maneuver. Can anyone confirm, and maybe provide some pointers on pitching/rolling/yawing/descending simultaneously? Do I just need to slow down?

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@Cap'n Chip I had something like that happen to me a few months ago (I have been flying commercial for three years). I was on a large construction site and my Phantom 4 Pro plopped out the sky as well. I thought it had hit one of the tall cranes. But upon looking at the data it was nowhere near the crane. A worker recovered it and luckily no one was hurt.

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Hi @Cap'n Chip

Sorry to hear about your drone, and welcome to the UAV Coach Community Forum! When I had my first Phantom 4 Pro I was flying the drone and it was about 1200 feet away from me and about 320 feet AGL. As I started to ascend a little bit my screen showed that the aircraft had disconnected. It looked just like as if I had turned the drone off and you see a black and white image of what the drone last saw. 

I watched it plummet towards the ground and went to go retrieve the drone which was luckily over a field and there was no one near the drone. The drone was smashed to pieces and I sent it into DJI to have them pull the flight logs. After the drone had crashed, it would not allow me to pull the flight logs. I was determined that is was a hardware failure and sure enough DJI said it was a power hardware failure. I have read similar stories of this happening to other Phantom 4 pilots. I have a new Phantom 4 Pro now and have never has an issue. 

Best, 

Chase 

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There are a LOT of variables and without seeing the flight logs, even then, troubleshooting can be difficult and subjective. 

On 7/8/2020 at 10:46 AM, Cap'n Chip said:

The only thing I can come up with is that the 100% descend and 100% pitch, coupled with the moderately humid air caused the drone to lose lift.

On 7/8/2020 at 10:46 AM, Cap'n Chip said:

the drone was moving horizontally at 27 mph and vertically at 11 mph. This is a maneuver I had done multiple times.

 

These comments are a bit at odds with one another.  It doesn’t sound like you just chopped the throttle “100%”.  There’s a condition where if your descending straight down quickly the props lose lift and cavitate.  Once that happens the props are stalled and the Controller freaks trying to regain control.  Higher density altitude means you have to slow your descent. 
 

Like any aircraft that has stalled you have to increase the airflow over the wing. Multirotors are rotory wings, so to recover from this you need to roll the drone on it’s axis almost 90’ the trouble is the controller won’t let you do this. DJI controllers are very susceptible to this, they even have a term for this “toilet bowling.”   
 

All multirotors suffer from this, however a couple of reasons that this afflicts DJI worse than others is that they control the throttle curve so that it always hovers at 50% even when the DA is high and it is actually hovering at a higher throttle but you’re not aware of it.  One possible fix for this is to switch out of ATTI mode while it’s falling, this enable you to roll to break the stall.  Most of the time the operator increases the throttle thinking it will increase lift, that only worsens the stall.  You can try lowering the throttle to zero and quickly back up several times and to see if there’s a range where it starts to produce lift again.  If you remain in ATTI the FC is working against you for this to work.  
 

unless it was really hot and humid you should have had enough horizontal airflow that it should not have stalled. I’m sure there’s a formula for lateral speed*DA/2x-vertical speed=stall..

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On 7/8/2020 at 1:46 PM, Cap'n Chip said:

I'm a relatively new, certificate holding, remote pilot and I just experienced my first crash. I'm hoping those with more experience can give insight as to possible causes so I can learn from this mistake and move on. The DJI Phantom 4 fell from and altitude of 300 feet AGL and appears to be a total loss. Fortunately we did purchase insurance so things could be worse!

Weather conditions were  generally favorable with very light wind (<5mph), great visibility (10 mi.), moderate temperature (85 degrees F), and moderate humidity (66%). I was descending from 395 to 311 feet AGL and rolling simultaneously to keep my subject in the camera frame. Immediately prior to entering an uncontrolled barrel roll and free fall, the drone was moving horizontally at 27 mph and vertically at 11 mph. This is a maneuver I had done multiple times. No setpoints were adjusted that would have permitted me to operate the drone in any manner outside of its default functionality. No warnings or alarms were present. The compass was operating normally and did not need calibrating (per the app). The drone had 6 hours of flight time on it and was still in "new" condition prior to the crash.

The only thing I can come up with is that the 100% descend and 100% pitch, coupled with the moderately humid air caused the drone to lose lift. I suspect operator error on my part, but feel like I was operating the drone as its designed to do and had no indication that I was performing an unsafe maneuver. Can anyone confirm, and maybe provide some pointers on pitching/rolling/yawing/descending simultaneously? Do I just need to slow down?

@Av8Chuck  brings up some great points about descending too quickly. It is important to descend slowly especially when the humidity is high because it creates what is known as a high density altitude. At higher altitudes the air is much thinner because the lack of pressure, therefore causing the air molecules to spread out further making it harder to create lift because there is less air molecules to "grab onto." Hot humid weather can create this same environment even when you are only a few hundred feet in the air. 

If you descend too quickly the drone will fly back through the turbulent air that is below the drone. This is known as Prop Wash, and it can quickly bring your drone down before you even have a chance to think about what happened. When you start to land, if you are descending too quickly the drone with start to wobble and you will hear the motors whining because they are trying to correct for this and return the drone back to a stable decent.  

According to your post you were also flying horizontally and descending at the same time. This is where wing-tip vortices come into play, just like a manned aircraft, the airflow that flows over the airfoil becomes turbulent behind the airfoil and flows back behind the aircraft. Think of a rotor prop on a drone as a spinning airfoil. As that prop cuts through the air, there are wing-tip vortices being created from the disturbance of the prop cutting through the air. So, if you had wing-tip vortices and prop wash from descending at the same time, these two aerodynamic forces could have easily brought the drown down as the air disturbance would have cause the props to stall, therefore no longer generating any lift. 

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