Phantom 4 falling from sky - prop screws loose...

[Chopstix Kid]

You can also use clear nail polish to lock the screw and provide a visual mark. I suppose you could also use a glitter polish - however you roll. One thing that does bother me looking at the picture is what appears to be metal fatigue on the bottom metal spring. That's the kind of metal fatigue that eventually breaks....

View attachment 54730

That's not fatigue... that's a relief bend so that when you remove the props, the edge of the spring does not catch on the prop. When the prop is attached, the edge of the leaf spring will be pointing slightly downward to prevent it.

 

[WetDog]

If that's a factory bend, it sure looks like they did it wrong. You can see wrinkles in the metal plating. Might be the picture but it looks pretty wonky.

 

[CrimsonPhantom]

Chopstix is correct, I have a brand new set for spares and the end is turned down and inward. Besides, fatigue is going to occur at the bend where the spring comes up from the flat part of the plate. They seem to be made from a good quality spring steel so the number of fatigue cycles is probably pretty high. Also, the deflection experienced by the spring during prop install doesn't look that much. It's just a wild guess but I would think the posts that lock the prop experiences more stress and would be subject to failure before the springs.

Bottom line, I think it would be very good practice to replace the prop mounts after so many hours of flight... The number of hours is the million dollar question.

 

[Jussaguy]

Anyone know of there is a recommended torque amount for these screws? I can see some overtightening them not wanting them to come lose. This is probably worse that then slowly coming lose over time.

Finger tight (or when it stops spinning), maybe a drop more but DO NOT over do it.

 

[AdvRider]

You can also use clear nail polish to lock the screw and provide a visual mark. I suppose you could also use a glitter polish - however you roll. One thing that does bother me looking at the picture is what appears to be metal fatigue on the bottom metal spring. That's the kind of metal fatigue that eventually breaks....

View attachment 54730

Looks like that spring would chew up the motors or jam it up outright if it broke off and fell into the stator area.

 

[Sim597]

Of course it's factory bent, nobody it saying the "bend" isn't intentional. When you "cold work" steel it tends to get brittle, stronger but more brittle. It's the artifacts in the picture that make it look like stress fatigue

 

[Kans]

That's a good catch, it LOOKs like fatigue to me also, I doubt if it fails it would be an aircraft part failure though, meaning that tiny piece may fall away without injuring another part, and the force from cold working, or tension, would still be applied when that piece comes off, still, I may order a set of these they're cheap and available.


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Thanks lads, have given a thorough check and dont see any issues at the moment on the spring load appearing on my picture, anyways have a few extras ordered just in case.

 

[realsting]

Thanks Stealthmatt

 

[WetDog]

It's the artifacts in the picture that make it look like stress fatigue

Could well be. It sure looks scary.

 

[Patrick]

remember loctite can cause plastics to crack, make sure its completely dry before putting screws back in, i found out the hard way with my p2v+, didnt make sure the loctite was completely dry and caused some cracks in the shell

 

[thunderbird]

checked yesterday and few screw was loose, just tighten it

 

[isopro]

This is something rly worth checking, i wonder if it only applies to the first batch of units, or most units...

 

[Theo450]

My P4 "threw a prop" today. My first crash... Dropped about 20 feet. It is banged up.

Had about 8 hours of total flight time. I thought I had probably not attached them correctly. I will be checking screws and will post the results.

If the screws were loose, does anyone think DJI would replace it?

 

[Theo450]

I worked on the aircraft today. The prop mount screws were all tight. I think my accident was a case of improper prop installation.

I put on some fresh props and ran a couple calibrations, and it seemed to function normally on a short test flight. The battery is ok too. There is a little body damage and one of the prop mounts has some minor nicks (I believe from impact). I am going to take it to my local shop for a thorough once over. I will have to fly the back up in the mean time.

I have some additional data after reviewing the flight log. The bird fell approximately 13 feet on to a fairly steeply pitched tin roof. Slid down about 8 feet of roof and dropped 2 feet to an asphalt roof. I believe that the pitch and material of the metal roof helped to minimize damage.

I am relieved, but still kicking myself. Updating procedures and checklists. Inspection of prop installation by a second person will be required. Will also add screw tightness inspection to maintenance routine.

 

[Harkness]

I WONDER WHAT COULD HAVE CAUSED THIS?