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Prop ripped off mid flight, apparently my fault + Terrible customer support ...
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3713 49 2015-8-10
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lambolambert
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United Kingdom
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When bringing the craft back into the wind to land, easily within range the signal dropped out and next thing I saw the DJI was falling flat out towards the ground and when I recovered the craft I found one of the propellers missing and the selftightining nut for the missing propeller attached to the motor and obviously the propeller was not attached.
As I use this for my academic research I striclty adhear to the protocls when setting up the craft for flight, notably the instructions of making sure that the propellers are attached securely before each flight, I am sure that it did not come off due to it being loose. This was also not due to erratic flying as it was being flown on a mapping mission where stability is a major factor.
[size=14.6666669845581px]Wind speed was recorded at around 6-7 m/s max on the ground. Have alook at the images attached for more information.
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[size=14.6666669845581px]This happened on the 19TH OF JULY!!! Since the DJI hardwear failure I immediatly sent it to my very helpful UK supplier who then passed it on to DJI in germany. After much pestering I heard back from DJI via my supplier on the 4TH of August!! Asking for over £220 ($340) to fix it as 'no fault was found'. Since then I have emailed DJI support directly quoting all of the relevant case information and not a single word back from them. This is catagorically my worst experience with a company ever.
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[size=14.6666669845581px]Please let me know your thoughts, I will be bringing this case to the relevant ombudsman if there is no progress.
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[size=14.6666669845581px]James
[size=14.6666669845581px]








Added to show no difference in nylon threading colour from opposire spinning props
2015-8-10
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bradneal24
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Strange as the P3's have self-tighening props. The threads on the post spin the direction opposite to the thread, which is supposed to pull the prop down and keep it locked into place.
2015-8-10
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lambolambert
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bradneal24 Posted at 2015-8-10 21:53
Strange as the P3's have self-tighening props. The threads on the post spin the direction opposite t ...

My thoughts exactly and only one of the motors, so the right style of prop (CW,CCW) for the right motor
2015-8-10
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bastell
lvl.4
Flight distance : 1526929 ft
Australia
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By looking at the pics you supplied it looks like the wrong prop was cross threaded onto the wrong motor as evident to the plastic left on the thread.I could be wrong but its just they way im seeing it.
2015-8-10
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Skater67
lvl.3
Flight distance : 417149 ft

Colombia
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Wow, sorry to hear about this accident.     Can you share some more info:  How many flights/hours did you have on the set of pros?  Do you hand tighten your props or use the prop wrench DJI includes with the Phantom?  Do you leave your props on or do you take them off after each day of flying?  Thanks and good luck with DJI.
2015-8-10
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chris
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Finland
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wow bad luck sorry to see this
but also maybe the prop was over tightened  and stripped the nylon thread prior to take off and it just held for so long then just lost all integrity,  thats my fear is over tightening the thread as I often strip threads on steel bolts
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lambolambert
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bastell Posted at 2015-8-10 22:01
By looking at the pics you supplied it looks like the wrong prop was cross threaded onto the wrong m ...

Good Point, I do agree but if you look at the inside of the propellers they are both the same colour, ( I have tried to link a picture I just took but I cant seam to link it in a reply, I will post in the opening ). So you are not able to tell which way a prop spins from the colouring of the nylon thread. and the pictures I took after the crash with the singular prop missing show that the other 3 were in the right location
2015-8-10
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lambolambert
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Skater67 Posted at 2015-8-10 22:06
Wow, sorry to hear about this accident.     Can you share some more info:  How many flights/hours di ...

The dji pilot app tells me that I had close to 4 hours before it failed.  after a day of flying I would take the props off with the tool and store them in the carry bag, so I would not be able to tell how many hours I would have flown with each blade unfortunately, even in the worse case scenario with a blade having been in use for 4 hours of flight (obviously in multiple flights)  it should not be at the point where it is failing.
2015-8-10
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DrACE
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United States
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Just out of curiosity, how many hours do the props/blades last?  I cannot find it on my app anywhere.
2015-8-10
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spiderbot.sb
lvl.4
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Sorry for your loss.

I've read that the P3 uses 'dynamic braking' which means that the motor can turn slower than the prop would normally turn due to airflow.  This means the resulting spin could actually be in the opposite direction thus loosening the prop.  I heard that this is why the prop hubs are plastic instead of metal, i.e because they give a little without loosening entirely.  This also implies that the props need replacing on a fairly regular basis.

HTH
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2015-8-10
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lambolambert
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spiderbot.sb Posted at 2015-8-10 22:29
Sorry for your loss.

I've read that the P3 uses 'dynamic braking' which means that the motor can tu ...

If that case, then it is a know potential hazard and they should warn users and provide assistance when it occurs. Which is certainly not the case here and they should fix it under warranty
2015-8-10
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Skater67
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Colombia
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Thanks for the reply.  With just 4 hours on the props it would not be a factor in the accident unless they were somehow damaged before flight.  I'm concerned that DJI includes a prop wrench in the DJI3 package and then advise pilots to hand tighten the props.  Using a wrench to tighten the props or remove them is suspect for possible damage and converting a DJI3 into a Tri-Copter.
2015-8-10
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chris
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Finland
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it's just that there is a tell tale piece of plastic swarf left witch looks similar  to the reesult of a stripped thread not loosening by motor braking
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chris
lvl.2

Finland
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or could it have been bird strike ???
2015-8-10
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lambolambert
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chris@chris-hil Posted at 2015-8-10 22:48
or could it have been bird strike ???

Not bird strike, It was close enough to see the prop detach
2015-8-10
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sploodge
Second Officer
Flight distance : 809350 ft
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I cannot even think how a properly attached composite prop would manage to come off like this all by itself. I would imaging DJI though the same..

Also by the photos, very little damage to the Phantom that fell flat out towards the ground ( unless the images hide the damage )..

As for the prop wrench, I use it all the time to loosen the props when removing them.. I find no issue with it at all ( no need to tighten them with it though ).
2015-8-10
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chris
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mmm just another incident to take heed of and jangle the nerves during pre  flight and while flying,
2015-8-10
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lambolambert
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sploodge Posted at 2015-8-10 22:54
I cannot even think how a properly attached composite prop would manage to come off like this all by ...

Unfortunately not , there was significant damage to the gimbal arms and the lens was shattered as well as bent landing gear
2015-8-10
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Skater67
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Good to hear your thoughts  Sploodge.  Maybe time will tell regarding the use of the prop wrench, especially, if other prop failures happen.  I'm sure the props could be damaged by over tightening or one could strip them off completely by using too much force.  Not sure we will ever be able to figure out what happened in this accident without DJI's assistance.
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lambolambert
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Skater67 Posted at 2015-8-10 23:03
Good to hear your thoughts  Sploodge.  Maybe time will tell regarding the use of the prop wrench, es ...

dji's assistance will be key which brings me to the secondary point, the complete lack of communication from them. If prop usage is a problem then that should be stated from now on by them, but it should not void my and others the right for a repair
2015-8-10
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soerheim.emil
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To me it looks like the prop have been ripped off the threads. I do never take off my props after flight because this will weaken the threads for every time you take them on and off.

Maybe there is a weakness in the plastic that made It fly off.
2015-8-10
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Seb
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spiderbot.sb Posted at 2015-8-10 22:29
Sorry for your loss.

I've read that the P3 uses 'dynamic braking' which means that the motor can tu ...

This would be true for propellers rotating in vacuum. But in air there is always drag significantly stronger than inertia force. So active braking is not an issue, because rotating motor is always pushing the prop against the air, creating significant drag that self-tighteens it.
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bradneal24
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bastell Posted at 2015-8-10 22:01
By looking at the pics you supplied it looks like the wrong prop was cross threaded onto the wrong m ...

Even if you could manage to cross thread with the wrong prop, I don't think the P3 will fly if prop configuration is mismatched.
2015-8-10
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jimcloud74
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bastell Posted at 2015-8-10 22:01
By looking at the pics you supplied it looks like the wrong prop was cross threaded onto the wrong m ...

Looks like nylon threads to me left on the motor threads. Remember that there should be no resistance when putting these on. I spin mine on with momentum and then put a "snug" twist on them. The braking won't spin these off. I just isn't going to happen. It's nylon on metal. Not metal on metal like the old P2 setup without active braking. Sorry for your loss.
2015-8-10
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Daninho
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jimcloud74@yaho Posted at 2015-8-11 00:06
Looks like nylon threads to me left on the motor threads. Remember that there should be no resista ...

The nylon threads give much more resistance than teh old metal ones. The old ones were smooth and you could flick them on for example, the new ones will stop at one point when you flick them. The strange thing is all my plastic threaded props get smoother over time and this is kind of scary because it would mean the threads wear down
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lambolambert
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Daninho Posted at 2015-8-11 00:18
The nylon threads give much more resistance than teh old metal ones. The old ones were smooth and  ...

Thank you for all your replies, so to summarise the general consensus is that it IS a prop failure and should hence be covered by the warranty?
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Willie Wonka
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lambolambert Posted at 2015-8-11 00:39
Thank you for all your replies, so to summarise the general consensus is that it IS a prop failure ...

I do not think it is prop failure, i see shiny threads on the prop mount which only says one thing, the prop was put on with force as in missing the groove, which could happen if the prop was put on rushed, and then spun took quick as i was able to do that on one prop and caught myself and threw it in the garbage after feeling it went wrong.

My way of putting them on without going in wrong is to put it on and spin it like I'm loosening it then it sits in the groove, then i start tightening without force then when its snug give it a quarter turn finger force.

Can you show us pics of the inside of the propeller hub and the propeller itself.

Last but not least i am very sorry for your loss.
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gregg1r
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First off, if you were able to screw a black tipped prop on one of the silver colored shafts, you'd flip the quad on start up. The foil direction is opposite so it would be pushing down when it was supposed to be pulling up.

You mentioned that you had 4 hours on the Phantom. How many flights would that be? With the props using a plastic center(composite) the threads do wear out. If you were using one of the metal hubbed props, they will liberate themselves with motor braking unless you really snug them down. Have you inspected the remaining props for damage? Also are you mixing and matching all eight supplied props or are .

I'm afraid that DJI is going to deny your claim as there is no proof that DJI was responsible for the crash.

I've seen folks reuse the prop nut retainers on boat propellers. When they shear off the remaining tab that's been folded a few times, you lose a $400-500 prop.
2015-8-10
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Cessna172
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United States
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How much would the cost of the following items be if your orderd them....

Gimbal arms
Lens
Landing gear
Propeller

Is it sometimes better to do the repairs yourself (if cpable)?

I tend to agree with Willie Wonka
Looking at the second photo, there "appears" to be damage to the threads which would have occurred before the crash since the prop came off before the crash.
It looks to me like user error in this case....The remaining plastic thread indicates the prop was damaged before takeoff and failed in flight from the forces of lift applied to the already damaged prop hub threads. ...but I too could be 100% incorrect so forgive my assessment if so.....but the OP asked.
You are probably over tightening the prop nuts.

BTW...I would probably replace that motor as well.

2015-8-10
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Skater67
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Colombia
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It certainly was a prop failure but there are no conclusive facts to determine why the prop failed.  

I would suggest DJI discard the prop wrench and give greater detail to their recommendation to hand tighten the props.  DJI states:  Self-tightening design keeps the propellers securely to each motor.  DJI Manual States:  Place all propellers onto the correct motors and tighten by hand to lock them in position.

I have not read in the DJI3 User Manual where they recommend using the Prop Wrench to tighten or loosen props.  I'm not sure why DJI includes one in the package unless they believe someone will hand tighten the props with such force that they won't come off without using a wrench.  I'm sure exerting enough force on the prop when using the wrench can damage the prop threads and cause a failure.   
2015-8-10
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Skater67
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I lJust looked at my prop threads with a magnifying glass and flashlight.  The Black props have black residue inside the threads that probably came from the black paint of the engine shaft.  The silver props have no residue and are extremely clean.  Not sure if this means anything other then a normal occurrence of  paint residue from the engine shaft.  Probably not a causal factor to your accident but your picture of the engine shaft looks like a Black prop failed.   Good luck with your repairs and let us know what happens.
2015-8-10
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liningiv
lvl.4
Flight distance : 329409 ft
United Kingdom
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We are told to tighten the props before flight and check they are still tight before the next.
But no torque values given.
To one guy tight is loose, and to another loose is tight.  Too subjective.
My opinion is that the prop was too tight and partially stripped the thread, and at sometime during the flight, the thread stripped.
I understand that on the Inspire there is a prop retainer that stops the prop from coming off even it fails.
2015-8-10
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Superfantastic
Second Officer
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United Kingdom
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should we be changing the props after so many flights ?  say 100 ?  i guess they will strip overtime i guess as they are just plastic.
2015-8-10
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jimcloud74
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Guys, we have to utilize a small amount of common sense. Blaming DJI on this seems a little on the absurd side. The wrench is to stop the motor from spinning while you apply ever so slightly some force on the blade. No there is not a torque recommendation because I am guessing that DJI doesn't want the responsibility of telling you a number and that causing the failure. They keep plausible deniability as of now. Just do it. Don't over do it. The blade will stay on. The braking is a non-issue as someone else stated as there is ALWAYS air resistance on a spinning prop. This issue is most likely from over torquing the prop which caused a failure. Will DJI assume responsibility? Who knows. You would be hard pressed to prove that it wasn't installation error in this instance. All of my props I have installed have been able to "spin on" from the very start. The carbon reinforced blades I purchased had one that must have had a bur on the inside as it wouldn't spin on but freely threaded on during the first installation. Now it does spin on. I, personally wish they had kept the aluminum hubbed ones as there was never any guessing on threading but I guess there is some minuscule chance that they could spin off.
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soerheim.emil
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Norway
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Like i said.. don't remove the props after flight. Your going to wear out the threads
2015-8-10
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bastell
lvl.4
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Australia
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bradneal24 Posted at 2015-8-10 23:35
Even if you could manage to cross thread with the wrong prop, I don't think the P3 will fly if pro ...

In my experience with RC aircraft, the wrong prop rotating the opposite direction will still create lift albeit at a loss in thrust.For these props not to create thrust they would need to be mounted upside down which is impossible with these props.
2015-8-10
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Quadifier
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bastell Posted at 2015-8-11 06:29
In my experience with RC aircraft, the wrong prop rotating the opposite direction will still creat ...

Actually....if you look at the props...they are pitched in opposite ways.  One turning clockwise to thrust downward...and the other turning counterclockwise to thrust downward.  So...if you happen to force the wrong prop on a motor....it will indeed thrust upward instead of downward.

Works the same way as mounting the blade of a fan on backwards.  It will blow in the opposite direction.

Edited to add:
Or...it works the same way as a boat prop.  When you put a boat in reverse...it turns the prop backwards....which pulls the boat backwards.  Same idea.
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bastell
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Quadifier Posted at 2015-8-11 07:12
Actually....if you look at the props...they are pitched in opposite ways.  One turning clockwise to ...

With these props the pitch is not aggressive like a boat prop the esc's would compensate for the loss and the aircraft would still fly.
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Mark97564
lvl.4
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United States
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I've got about 50+ hrs on my E300 motors and 9450 props And no issues at all..  everything is running great
2015-8-11
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robotertest
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Germany
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Mark97564 Posted at 2015-8-11 16:38
I've got about 50+ hrs on my E300 motors and 9450 props And no issues at all..  everything is runnin ...

Me too, but there always will be users doing wrong , attaching rotors. Regardless of brand.The only system, which is nearly foolproof, came with the E800....but even with this system, unexperienced users managed to brake the lower mounting parts.
2015-8-11
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