Mid Wales, United Kingdom. June 1st 2017. The weather was warm, high cloud base, minimal wind and a bright sunny day.



I had used the P4 over a number of occasions during the day visiting 3 different construction sites undertaking commercial photos.



I did my pre-flight checks as usual and took off at my last site and undertook a number of long range aerial photos from my take off area (a large farmer’s field with long grass, but with a good hard flat area for a safe take off and land).



Following on from my successful session and in bringing my P4 back to land (at this point my flight time was approx 3 minutes) I hovered close to my landing area at approx 50m high and started to rotate in an anticlockwise direction.



Without warning.....the P4 rotated violently and started to descend rapidly. I looked up and could see it spinning out of control and heading for the ground.



Upon landing with a dull thud in the grassed field I found that the aircraft was damaged beyond repairs. (see photos)

From the initial inspection of the craft it was evident that not only was a propeller missing but also the propeller mounting plate on the front right motor (when viewed from above) was missing. The fixing screws for the mounting plate were not snapped in place, but missing totally.  



Having interrogated the flight log it stated (at the point of collapse).......'motor idling....propeller loss.


https://www.youtube.com/watch?v=QqTvnEPz-DI


Have any other P4 owner/operators had a similar issue and what was the outcome?

Do I have any claim against DJI and if so, on what grounds?

Advice please.

Sorry for your loss
If you search on youtube, there are many videos of similar accidents, when you miss one of the propellers

Seems odd that all three screws would come completely out in just a 3 minute flight, and that they would all come out leaving no damage to the threads or broken screw pieces in the threads.

Did you not notice that the mounts were loose before the flight?

How many flights/flying hours since you last checked the tightness of the screws?

Are those genuine DJI propellers?

"Do I have any claim against DJI and if so, on what grounds?"  
Might depend on how old it is?


It is very rare for P4 propellers to fly off, but there were a few cases last summer where the screws came loose.

Nigel_ Posted at 2017-6-8 11:15
Seems odd that all three screws would come completely out in just a 3 minute flight, and that they would all come out leaving no damage to the threads or broken screw pieces in the threads.

Did you not notice that the mounts were loose before the flight?

Nigel,

I have over 15 hours flying time with these props.

All mounts were tight prior to take off (I check these prior to each flight)
Like you, I cant understand how the THREE screws came off leaving no trace.
The P4 was bought last June (yes I am just inside the warranty period)

I have emailed DJI for guidance and support.

The screws not still being in the mount is bizarre.  

If you don't mind me asking....what are the make of the props on your P4?

InfinityAM Posted at 2017-6-8 11:33
Nigel,

I have over 15 hours flying time with these props.

If they were not genuine DJI props then maybe poor balance vibrated the screws out - there will be a warrantee problem if they are not genuine.

For the future, I recommend drawing a line across the screws onto the mount so that it is easy to check if they are unscrewing every time you mount the props - the lines will get broken.

If it was almost new then I would expect them to replace it, at that age I'm not so sure, some parts don't have full 12 months warrantee.  Good luck with DJI support.

If it isn't covered, it can still be repaired, doesn't look too bad, new case and new P4 gimbal/camera doesn't cost too much, I don't see any other damage.  If it is sent in to DJI repair then they will give a quote before doing anything, then you can decide if it is worth it.   New ones come with virtually free new batteries though and if you take the cost of gaining the batteries into account then a repair may not be so worth while, unless you replace the parts yourself, takes a bit of work but it is doable.

I've not seen a case of props coming unscrewed recently so can't point to other peoples experience, plus people get different experiences depending on country.  You will just have to wait and see what DJI says.  If they say no to warrantee then ask for a discount on repairs or replacement, you should be able to get 30%.

I would like to hear an explanation for this that I could believe.  It is not that I don't think it could happen, but just that there should have been enough warning, either from the sound of the blades or general instability of the AC, before the blade completely broke free.  I could be wrong. We need an engineer !

Just unscrewed 2 of my props to check and they were relatively clean underneath but I notice on yours (photo showing missing screws) there is some signs of dirt marks that look old - possibly loose for a while perhaps? Just a thought.
I would think that non original props would almost certainly void any warranty. Agree with Nigel_ initial view is that new case and gimbal would fix.
Good luck with whatever direction you go with.

JW5255 Posted at 2017-6-8 15:23
I would like to hear an explanation for this that I could believe.  It is not that I don't think it could happen, but just that there should have been enough warning, either from the sound of the blades or general instability of the AC, before the blade completely broke free.  I could be wrong. We need an engineer !

The prop sits on the axle so it cant move out of position as the mount comes loose.  I assume the screws are quite short and come fully out before the prop comes off the axle.  You might still expect a rattle but it is always held under 300g+ of tension by the lift from the prop.

We should check the aircraft over for loose screws, cracks etc regularly, as is done every flight for manned aircraft.

Nigel_ Posted at 2017-6-9 01:47
The prop sits on the axle so it cant move out of position as the mount comes loose.  I assume the screws are quite short and come fully out before the prop comes off the axle.  You might still expect a rattle but it is always held under 300g+ of tension by the lift from the prop.

We should check the aircraft over for loose screws, cracks etc regularly, as is done every flight for manned aircraft.

Three screws, one becomes loose.  Prop lift should cause a change in pitch (prop will lift higher on that side) due to uneven attachment at the axle. The pitch change should be heard, and/or seen as an unsteady hover.  Depending on the direction of the blade (CW or CCW), this distortion and uneven lift, could unscrew the remaining two. The force required to do this should also cause the prop to turn outside it's normal spin disk plane causing an irregular noise.  I have not tried it, but seems plausible.

Personally, I think something is wrong with the story as described.  I cannot believe, even for one second, that the mount was checked prior to a 3 minute flight, was deemed tight, but three minutes later all three mount screws unscrewed and released.  I also agree that the marks on top of the motor indicate that the mount had been loose for a while and had been allowed to scuff the top of the motor.

I dunno.  I'm sorry that you had a crash, that totally sux.  But something is akimbo in your story.  It just doesn't add up.  Maybe you checked the PROPS to make sure they were locked (Not the actual motor mount) and just didn't notice that although the prop was connected to the mount, that the mount seemed loose?  (unless the mount was really loose, it would be easy to miss the underlying problem when doing a prop-check.)

Even that is a mystery though, because the screws on the mount would have already needed to be in a dire state to go catastrophic in 3 minutes...  like maybe two of the screws were already gone and the third was super loose....  

Wondering if you shot video at any time during those three minutes?  IF so, do you happen to notice a vibration in the footage?

InfinityAM Posted at 2017-6-8 11:33
Nigel,

I have over 15 hours flying time with these props.

So what your saying you,ve flown 15 hours with those props but there NOT genuine DJI props but badly made weak aftermarket props if so that tells  to pilots ONLY buy genuine props...........if thats the case thanks for showing us so we dont make the mistake you have

Jcostello Posted at 2017-6-9 11:21
So what your saying you,ve flown 15 hours with those props but there NOT genuine DJI props but badly made weak aftermarket props  if so that tells  to pilots ONLY buy genuine props...........if thats the case thanks for showing us so we dont make the mistake you have

This post is a classic case of NOT reading the thread through, and making stupid, incorrect assumptions. Nowhere does the OP say they were not genuine DJI props, and who says they were badly made?

After reading with alarm your story of woe I have completed a somewhat closer inspection than usual of my own P4, which in mechanical terms has performed flawlessly (App glitches not withstanding) for scores of flights since I bought it in April this year.
I find that the propeller mounts on the two motors with black dots have some slight play in them, whereas the other two without dots are still firmly attached.
Some adjustment/tightening with a small Allen key seems to be required. I've grounded myself until I can sort this out.
Your post may well have saved me from a similar fate and much grief. For that, I thank you for sharing your unfortunate experience.
It's not apparent from your photos posted here, since the prop mount presumably disappeared with the propeller, but was yours one of the black-dot ones, or not?

Blériot53 Posted at 2017-6-10 00:02
After reading with alarm your story of woe I have completed a somewhat closer inspection than usual of my own P4, which in mechanical terms has performed flawlessly (App glitches not withstanding) for scores of flights since I bought it in April this year.
I find that the propeller mounts on the two motors with black dots have some slight play in them, whereas the other two without dots are still firmly attached.
Some adjustment/tightening with a small Allen key seems to be required. I've grounded myself until I can sort this out.

The two black ones are still there in the second photo, it is the front right that is missing.

When you tighten the screws, remember that the mounts are plastic, they should not be tightened any further than the good ones have been otherwise you may damage the plastic.  When you have finished, use a permanent marker to draw a line across the mount and screw so that you can easily check if they are not unscrewing again in flight - this means that you do not need to tighten them a little extra just in case!

Ah yes! I see that now on second inspection of the photos.  I had speculated that perhaps the direction of rotation of the propellers might have been a factor in the loosening of the screws.
But that seems to be discounted as it's the one without the black dots which has come undone in the case described here.
Thanks for the tips on adjustments. Do you happen to know the size of Allen Key required?  I have a set, but none is small enough, I shall have to acquire some smaller ones, but hardware stores are
rarer than hens' teeth in rural France   Might be a job for Amazon or Ebay.

Blériot53 Posted at 2017-6-10 02:39
Ah yes! I see that now on second inspection of the photos.  I had speculated that perhaps the direction of rotation of the propellers might have been a factor in the loosening of the screws.
But that seems to be discounted as it's the one without the black dots which has come undone in the case described here.
Thanks for the tips on adjustments. Do you happen to know the size of Allen Key required?  I have a set, but none is small enough, I shall have to acquire some smaller ones, but hardware stores are

1.5mm across the flats, a common size for cameras.

Sometimes a small flat blade screwdriver will also work perfectly well if the blade is the right width, you only need enough torque for holding plastic so no need to be concerned about damaging the screw with a bad fitting driver.

Nigel_ Posted at 2017-6-10 04:20
1.5mm across the flats, a common size for cameras.

Sometimes a small flat blade screwdriver will also work perfectly well if the blade is the right width, you only need enough torque for holding plastic so no need to be concerned about damaging the screw with a bad fitting driver.

What you gonna do with the carcass?

Nigel_ Posted at 2017-6-10 01:11
The two black ones are still there in the second photo, it is the front right that is missing.

When you tighten the screws, remember that the mounts are plastic, they should not be tightened any further than the good ones have been otherwise you may damage the plastic.  When you have finished, use a permanent marker to draw a line across the mount and screw so that you can easily check if they are not unscrewing again in flight - this means that you do not need to tighten them a little extra just in case!

I'm pretty sure the screws are shoulder screws which tighten down against the shoulder of the screw and the motor assembly. The shoulder is made to be as close to the same length as the plastic, so that there is no force placed on the plastic. The screws are tight and the plastic motor mounts are floating, but held in place. The screws should be snugged up enough so as not to come loose in flight.

Nice shots! Sorry for your loss  I hope it doesn't happen to mine coz I would CRY!