Always Check Your Props Before Take Off!

[Kdavis2269]

I think it's a design flaw in the way the props are secured to the motors. I noticed small indents on the trailing edge of two of my props where the back of the blade hits the hub of the opposite blade. When the motors start the blades are thrusted backwards into the opposing blades hub before centrifugal force straightens them out. Once an indent is made on the back of the blade stress fracturing will eventually start to form and cause the blade to break off near the hub

Just my observation and opinion.

Zoom in on the attached picture and you can clearly see a fracture propagating from the indent cause by the opposing hub. I'm sure the same thing is happening in the hub as well. We just can't see it until it's to late...

 

[TJBC75]

Well, that explanation certainly fits the circumstances that I experienced. There was no warning in previous flights that this would happen - no wobble, no unusual sound, nothing. I've never had a crash before this happened in over a 100 flights. It just occurred when the motor spun up for takeoff. Like I said before, glad it happened where and when it did rather than out over the water when I was getting video of the beach and town. I guess if you want a quiet drone, this may be the tradeoff.

 

[Thanev]

I have seen the same and replaced 6 props(single pieces)without having had a single crash or improper storage.I now check EVERY prop before EVERY flight.

 

[RemE]

Hi all,

I initially started this thread. I too was worried that I lost a screw when the prop broke off. But no, the screw was still there and tightly in place as I had to use a bit of force with the L shaped screwdriver when taking it off to replace the prop. When I replaced the other prop that I suspected had a slight crack in it, that screw was also tightly in place. These were the original props that came on the Anafi. After this incident, I would like to carry some spare screws, is Parrot now selling them? Someone mentioned temperature changes affecting the prop;. that could be possible as I live in the Chicago area and have been flying in 25 degree F temps recently while in Mexico, it was more like 85 degree F. Although I recovered the Anafi and it appears to be fine, the experience was disconcerting and took me by surprise.

Just to be clear, the screw was still there, was the plastic prop hub still there as well? Or did it break off? I always felt that the prop blades were so paper thin, with very little reinforcement at the hub. I figured a blade might snap off, leaving the hub.

Is that what happened to you?

 

[pmh1nic]

You're probably very luck it broke when it did. I'm guessing the higher you would have gone the more likely in might have ended up in the ocean.

Maybe a good way to do an inspection of the props is using a flashlight. Shining a light on each prop may reveal a micro crack that wouldn't normally be visible.

It would be interesting to know if Parrot has a recommended number of flight hours for replacing the props. That said conditions that might introduce nicks or scratches (landing and taking off from sand or dirt) may be more of a factor versus flight hours only.

 

[IronSky1]

You can also use a small piece of tread lock or wax instead of the chemical liquid it just tightens space up. I do not use any however, may be a good idea.

 

[TJBC75]

Hi RemE,

There was nothing left on the screw, no hub, no prop. In fact, I tried to look for the damaged prop/hub after I got the Anafi down, but could not find it or any piece of it. I suspect that the hub cracked off taking the prop with it.

 

[Wezsh0T]

I think there might be an inherent design weakness to the props. Look at the way the props are molded. There's a diagonal seam on the hub. That looks like a point of failure to me.

 

[Landbo]

I think there might be an inherent design weakness to the props. Look at the way the props are molded. There's a diagonal seam on the hub. That looks like a point of failure to me.

No, it's quite normal what you see there and doesn't weaken the props. It is the division between the two halves of the mold. If there is a molding defect in the plastic, you can see that it changes color or has holes and cracks

Regards, Leif.

 

[Moonfly]

Prima di iniziare un volo, apro le eliche. Anche voi le aprite?

 

[Jagerbomb52]

Prima di iniziare un volo, apro le eliche. Anche voi le aprite?

Moonfly, English please

Before starting a flight, I open the propellers. Do you also open them?

 

[Jagerbomb52]

I have had props with the chip from the other hub and also had them with hairline cracks. I try and have the props set up so if they whip around they will not smash into the opposing hub.

Not sure what these where caused by, maybe bugs

 

[Moonfly]

Agustine really wasn't my intention. I used the google translator. I wrote in English. I don't understand what happened..

 

[Jagerbomb52]

Here is another prop I changed. Under bright light you can see it has been damaged from the other side hub. Not yet chipped out but close. These props are not strong enough and way to light weight for a safe UAV.

 

[RemE]

I am in the camp of NOT opening these props before flight. This is because they are so free in their pivots that at startup the hub will quickly twist and pivot the props until they smack each other. Then as the whole assembly spins up fully, the props will open. The least stress would be to rotate all props to the end of their travel before startup, then they won't smack at power up and will open up as the motors spin up.

I do open DJI props because they are stiffer and don't smack at power up.

 

[Moonfly]

[QUOTE = "RemE, post: 13833, membro: 893"]
Sono nel campo di NON aprire questi oggetti di scena prima del volo. Questo perché sono così liberi nei loro perni che all'avvio il mozzo ruoterà rapidamente e ruoterà i puntelli finché non si schiacciano a vicenda. Poi, mentre l'intero gruppo gira completamente, i puntelli si apriranno. Il minimo sforzo sarebbe quello di ruotare tutti gli oggetti di scena fino alla fine del loro viaggio prima dell'avvio, quindi non schiacceranno all'accensione e si apriranno quando i motori si accenderanno.

Io apro i puntelli DJI perché sono più rigidi e non danno energia all'avvio.
[/ CITAZIONE]
This consideration is interesting. I have an idea to make a slow motion video of the propeller movement when i start Anafi...

 

[AaronB]

Here is another prop I changed. Under bright light you can see it has been damaged from the other side hub. Not yet chipped out but close. These props are not strong enough and way to light weight for a safe UAV.

That hub looks a bit suspect also:

 

[Jagerbomb52]

Took a closer look today at that prop and yes indeed the hub is cracked. I had to shove a small nail in there to open it up to see it better but yes it is split. It took a fair amount of force to open it up. Going to need microscopes to go over your props. ?

 

[BGabor]

I am just check the props. One prop on every rotor is cracked at the same place on the edge. when I rotate the rotor by hand to the direction which is shown by the white triangles on the top, the prop touch the other hub and there is the crack. I have to change all of them now or it is normal until when? Very small cracks. I always opened the props before the fly. Maybe it is help in the future when I close the prop to the other hub depends the rotating direction? Maybe the starting force make the crack when it hit the other hub at the beginning? Or is it always hit the other hub when change the rotating speed? In this case every month have to buy new props?

 

[BGabor]

I am just removed the first screw. As i started to rotate I felt a little bit more fixing and now I see, there is a blue liquid. I think it is Loctite. I will use the Loctite when I'll put it back. Very small screw and rotating very fast. I am afraid on those props where the rotating direction is the opposite than the screw closing direction so, maybe it can open it without Loctite. (I have a Ducati, there I have to use the Loctite on every screw or else the vibration open it a little bit later).