P4P: In-Flight Power Failure

Fly Dawg

Premium Pilot
Joined
Apr 29, 2016
Messages
4,078
Reaction score
1,762
Location
Watkinsville, Georgia
All I can say is this flight was doomed from the start, even without looking at the full data file. You never should have taken off in the first place.
 
Joined
Jul 9, 2018
Messages
8
Reaction score
3
Age
23
Thanks for the input. The surface we were launching from is responsible for the errors that you are seeing. After bringing the sUA away from the magnetic surface, the errors went away - as expected. The last minute of the data is what I am curious about. If you can provide any insight on that, please let me know. Otherwise, thanks for the comment. Taking off in that location was a risk that I accepted (being on a construction site) and I paid for it - either because of the location, batteries, humidity, RF interference, other pilot error, or something else.
 
  • Like
Reactions: BigAl07 and tompugh

Fly Dawg

Premium Pilot
Joined
Apr 29, 2016
Messages
4,078
Reaction score
1,762
Location
Watkinsville, Georgia
Unfortunately, this appears to be another P4 battery dislodge. I cant be certain but the indications are there. If you were not aware there have been more than a few reports of these verified by those of us who look at data files. This is a known issue with the P4's and is supposedly corrected in the V2 series. Judging by the graph below the severe throttle up and back elevator could be the culprit for dislodging the battery at 62ft. As I said, there have been more than a few of these before. This is approximately the last minute of the flight.

MANEIVERS.png
 
Joined
Jul 9, 2018
Messages
8
Reaction score
3
Age
23
See, that's the thing - I am very well aware of that issue and make sure the batteries are fully seated prior to take-off (hard press in, check tabs). I had thought of this as a possibility (did not have a graph to reference) and even listed it as the first possibility in the write-up. ...but I also did not keep this as the top theory because the P4P was in the air for approximately 4 more seconds after the last maneuver (throttle up, pitch back, which you referenced) before it cut power - based on DJI GO 4 Flight Records log. Since it was in P-Mode, the P4P did do its "forward pitch" thing to stop once I let go of the controls...not sure if that jolt could cause the battery to become unseated...but the jolt didn't take 4 seconds to happen and the P4P was hovering during those seconds but also did a weird "hook" - see attached image. It sure doesn't look like it was self stabilizing during those moments and there was 0 pilot input during that time. I couldn't see it do that because I was looking at the screen and it was too small of a difference for the VO to pick up but that's what the DJI Flight Record and AirData charts are showing.

Now that you've shown me the graph, I can see also see how the data could align with the other battery dislodge cases. How possible is it for the battery to dislodge without actually moving out from the latch? I know that if you flip the P4 series over and press down, you can get the bottom tab to show but not lose power. Thanks for pulling that graph for me.
 

Attachments

Fly Dawg

Premium Pilot
Joined
Apr 29, 2016
Messages
4,078
Reaction score
1,762
Location
Watkinsville, Georgia
How possible is it for the battery to dislodge without actually moving out from the latch?
That I can't answer. From my prospective, I only go by what the data relates, and others who have input with similar issues. I believe the V2 series now has a sensor to ensure battery seating ( That is why I said "supposedly corrected" ) I am not sure that would fix the issue. P3's have had basically zero issues with this, and I am not certain on the design change for the P4's but obviously that portion is not as well thought out by DJI.
 
Joined
Jul 9, 2018
Messages
8
Reaction score
3
Age
23
Yeah, I heard about that too. Not sure that battery seating feature would have helped in this particular case.
 
Joined
Jun 11, 2016
Messages
3,506
Reaction score
1,980
Location
Northwest USA
Keep hearing of this horrible thing happening. Velcro the battery in with a strap over it?
 
  • Like
Reactions: Droner66
Joined
Apr 16, 2018
Messages
313
Reaction score
106
Age
60
Or tape applied to top and bottom seams. Electrical tape is what I use. It has just enough tack and will easily pull off.

But the Velcro strap is a good idea.

I Need to work on that.

Paul C
 
  • Like
Reactions: GrammatonxXXxCleric
Joined
Jul 9, 2018
Messages
8
Reaction score
3
Age
23
There's always the Phantom Rain Wetsuit: Home

If battery dislodge is the actual root cause, would anyone be able to explain how the abnormal flight path of the P4P 4 seconds prior to the in-flight power failure links with the dislodge theory? There was no controller input when that occurred. Trying to make sure that all the facts align with the theory before closing the case.
 
  • Like
Reactions: PhantomWetSuits
Joined
May 11, 2018
Messages
43
Reaction score
31
Age
62
I recently bought a P4P and had read about this alleged battery dislodge stuff before flying it for the first time. So I examined the aircraft in my home office for awhile trying to see how I could insert the battery without fully seating it. I did notice that when you push it in, there seems to be two separate and noticeable clicks, one for the top tab and one for the bottom tab when they engage. Anyways, I listen for that when I install my batteries, then carefully look at the top and bottom seams and tabs afterwords. Personally, I don't believe this is the cause of this incident and most others.
 
Joined
Oct 30, 2015
Messages
26
Reaction score
7
Age
67
It is with no surprise that I hear batteries coming out of p4’s, from day one I was horrified that wiggling in particular one of my batteries caused it to unclip both top and bottom latches. I notice in all p4 crashes and tumbles that batteries are thrown out! I have 3 batteries, 2 of my batteries clip in quite well but they don’t fit properly like my P3 which grips them vice like. I use a little electric tape either side with a folded over end (a tag)enabling me to grip it without having to pick it at the edge to tremor it. There is clearly a design fault.
 
Joined
Apr 10, 2016
Messages
511
Reaction score
167
Location
Sarnia ON Canada
There's always the Phantom Rain Wetsuit: Home

If battery dislodge is the actual root cause, would anyone be able to explain how the abnormal flight path of the P4P 4 seconds prior to the in-flight power failure links with the dislodge theory? There was no controller input when that occurred. Trying to make sure that all the facts align with the theory before closing the case.
Sure... the abrupt maneuver dislocated the latch pressure between body and battery... now the bottom tab of the battery latch is compressed to a point it is able to move backwards in the slot....a few seconds of static vibration (hovering) .... and off it pops.

May start adding Velcro myself after hundreds of battery snapping ...... in and out.
 
Joined
Feb 3, 2018
Messages
323
Reaction score
192
Age
51
Location
TORONTO, Ontario, CANADA
I just use some medical tape you can get at the drugstore. It is reusable, holds well to the plastic but doesn't leave a residue, and two small strips on the diagonal add a layer of protection. That, combined with avoiding abrupt maneuvers gives me a little peace of mind when flying.
 
Joined
Jun 11, 2016
Messages
3,506
Reaction score
1,980
Location
Northwest USA
Sounds like people got smart quick and saw the writing on the wall...
 
  • Like
Reactions: Robert Kelly

sar104

Aut disce aut discede
Premium Pilot
Joined
Mar 22, 2014
Messages
4,941
Reaction score
2,421
Location
Los Alamos, NM.
There's always the Phantom Rain Wetsuit: Home

If battery dislodge is the actual root cause, would anyone be able to explain how the abnormal flight path of the P4P 4 seconds prior to the in-flight power failure links with the dislodge theory? There was no controller input when that occurred. Trying to make sure that all the facts align with the theory before closing the case.
There was no abnormal flight before the disconnect according to any of the logged parameters. The "hook" that you mentioned previously was less than a 2 ft position correction after stopping - perfectly normal.

2018-06-30_[06-05-06]_02.png



2018-06-30_[06-05-06]_01.png
 
  • Like
Reactions: Blade4
Joined
Apr 10, 2016
Messages
511
Reaction score
167
Location
Sarnia ON Canada
If you have an inserted part that is binding and will not slide out. Just tap the part lightly to set up a vibration and gravity will do the rest. It's not any mystery that at battery can separate while in a hover if it has been partially dislocated by an abrupt maneuver. The lower battery latch, either not fully inserted . . or partially dislodged by a jerking motion . . .would be prone to vibration creep. . . and ultimate separation. The above flight analysis is pretty clear it's a likely scenario.
 
Joined
Jul 9, 2018
Messages
8
Reaction score
3
Age
23
There was no abnormal flight before the disconnect according to any of the logged parameters. The "hook" that you mentioned previously was less than a 2 ft position correction after stopping - perfectly normal.

View attachment 101124


View attachment 101126
Thanks for pulling the data and analyzing it. What software are you using to get the display?

Based on the analysis, are we able to come to the conclusion that this was a battery dislodge and was caused by pilot error? Or is it possible that the battery could have dislodged by itself and pilot error cannot be definitely proven?


@Timinator, sounds great idea - I've noticed that electrical tape in close to 100°F weather usually ends up leaving lots of residue. May very well implement that method.
 

sar104

Aut disce aut discede
Premium Pilot
Joined
Mar 22, 2014
Messages
4,941
Reaction score
2,421
Location
Los Alamos, NM.
Thanks for pulling the data and analyzing it. What software are you using to get the display?

Based on the analysis, are we able to come to the conclusion that this was a battery dislodge and was caused by pilot error? Or is it possible that the battery could have dislodged by itself and pilot error cannot be definitely proven?


@Timinator, sounds great idea - I've noticed that electrical tape in close to 100°F weather usually ends up leaving lots of residue. May very well implement that method.
Without the aircraft DAT file and an examination of the aircraft, it's really not possible to reach a definitive conclusion on whether this was a battery disconnect. Historically, that's the most common cause, especially with the P4P, but solder joint failures on the main board have also been seen, at least with earlier models.

If it was a battery disconnect then it's also not completely clear whether that is failure to secure the battery latches properly or if there is a design flaw with the P4P. DJI added a latch sensor to the v2. It does seem to be a somewhat common problem though. I recovered a P4P last week from dense forest that apparently suffered the same fate. Interestingly, while the aircraft DAT file clearly showed the voltage collapse when the power was lost, it appeared that the relatively soft impact (a large bush) reconnected the battery, because it rebooted and reconnected to the RC, although the operator was unable to figure out its location. When I found it the battery was in the aircraft but the bottom latch was not secured.

The data analysis and graphing was done in Igor Pro.
 

New Threads

Forum statistics

Threads
134,052
Messages
1,387,566
Members
97,758
Latest member
ExallRoofingLtd