It happened again - prop failure #2...

[Harleydude]

Hello HarleyDude, Yes I had the same exact failure, I saw the one blade fly off at about 30 ft. I have been checking props ever since. I flex them and look for cracks. And yes it was a genuine DJI prop.

This is very good information. The thing I noticed about the aftermarket props was there was some rotational "slop" at the hub. Not much, but they were night tight like the OEM props. I believe this "looseness" may have exacerbated the "breaking hub" condition. By my guestimate, I was getting a mere 2 hours of flight per prop set before one failed.

Questions:

Do you know about how many hours you have on your props?
Did you have any play at the hub?
Did you have any impact damage to your props from prop strike or anything like that?
Can you post a couple photos of the hub and the embossed markings on the blades?

Thank you!!

I believe I, too, will do this flex test from now on.

Thanx!

D

 

[PhantomWetSuits]

I hear what you're saying. The kind of inspection you're talking about is done well at home under good lighting (which I do before every job), but when I'm out in the field trying to beat the wind on the top of a hill, I honestly can't take time to conduct comprehensive inspections of every rotor after/before every flight.

My solution, for now, is going to be to use the Obsidian props. There's a clear difference in fit and form. Where the P4P rotors have "slop" with the motor hub, the Obsidian props fit very tightly. Methinks the perpetual change in motor RPM may be causing the "sloppy" props to "bang" to and fro on the motor hub. This may be causing plastic fatigue in the prop's hub (which is where I'm seeing failure). Conversely, the tight-fitting Obsidian props wouldn't have that issue because there's no "slop." So I'm going to give that a shot. I guess we'll see if that works.

FYI: The Props covers that come with the Phantom Rain Wet Suits really lock in those props and the new Silent props as well. One of the problems we had were props falling off when hitting some leaves , that doesn't happen anymore.

The Covers are made of Neoprene and offer a little bit of give as you push down on the Props to lock them in and the Neoprene helps protect the Inside of the Props from wear and tear. These are the new Silent Props and they offer a really good strong fit as you can see the indent of the Neoprene Covers. Absolutely no slop

 

[Harleydude]

FYI: The Props covers that come with the Phantom Rain Wet Suits really lock in those props and the new Silent props as well. One of the problems we had were props falling off when hitting some leaves , that doesn't happen anymore.

The Covers are made of Neoprene and offer a little bit of give as you push down on the Props to lock them in and the Neoprene helps protect the Inside of the Props from wear and tear. These are the new Silent Props and they offer a really good strong fit as you can see the indent of the Neoprene Covers. Absolutely no slop

View attachment 101790

While I think the neoprene covers might be okay in cooler weather, I'm concerned that they are impeding motor cooling. We often fly missions in 90°+ heat (never over 100). I monitor motor temperature closely, which has been surprisingly cool to the touch.

Any thoughts on that?

D

 

[PhantomWetSuits]

While I think the neoprene covers might be okay in cooler weather, I'm concerned that they are impeding motor cooling. We often fly missions in 90°+ heat (never over 100). I monitor motor temperature closely, which has been surprisingly cool to the touch.

Any thoughts on that?

D

Originally that was one of are concerns also , but the DJI team that we worked with explained to us that the motors would not be prone to overheating even with the top holes covered as they are meant to handle extreme temps as high as 300 degrees . Being that they are made of Aluminum they are designed to negotiate high temps.

With that said we flew in 120 heat in Tennessee for the Total eclipse and the hottest the motors ran after an hour were 128 degree f.
and the battery was 120.

Last week we flew in the 100 degree sun and this is the temps for 24 minute flight for the motors was 118 f
and here is the battery

Just to put some Perspective on it. So the Motors heating are simply not an issue do to the fact that they are made of Aluminum, with
High heat tolerance 300 degrees if not more.

 

[Harleydude]

Originally that was one of are concerns also , but the DJI team that we worked with explained to us that the motors would not be prone to overheating even with the top holes covered as they are meant to handle extreme temps as high as 300 degrees . Being that they are made of Aluminum they are designed to negotiate high temps.

With that said we flew in 120 heat in Tennessee for the Total eclipse and the hottest the motors ran after an hour were 128 degree f.
and the battery was 120.

Last week we flew in the 100 degree sun and this is the temps for 24 minute flight for the motors was 118 f
and here is the battery

Just to put some Perspective on it. So the Motors heating are simply not an issue do to the fact that they are made of Aluminum, with
High heat tolerance 300 degrees if not more.

View attachment 101794
View attachment 101795

Thanx for that information. That's very helpful.

D

 

[bhartwell]

I’ve not noticed any wiggle room on my stock P4 props. They fit snug and do not move. I wonder if this might be a contributor to your problem. If the prop is getting unexpected vibration, it might be weakening the plastic, causing it to crack and ultimately fail.

 

[Safety71]

Honestly, I think this is a QAQC issue....or perhaps a design flaw. If you think about it, mapping is pretty hard on a bird. It flies all day, back-to-back mission at an average speed of 25 mph, with RTH set to 33 mph. We have 6 batteries and 2 chargers that charge 3 batteries simultaneously. So with all that, we can pretty-much keep the bird in the air all day. So, though I don't have a lot of flight hours on the birds, they are fairly hard hours. With more speed comes more dynamic load on the rotors, especially on days when wind gusts hit 20-25 mph. I simply think the props are made cheaply and are therefore failing under these demanding loads. Because me and my partner are at the bleeding edge of mapping technology and working a LOT, I just think we're seeing failure where most pedestrian pilots are not.
After reading your posts and reviewing your descriptions of work being performed I have concluded that you are doing work with the wrong drone. You should be well above the P4P and using a more commercial type drone, built for the work to be performed.

I know, right?!




I will definitely keep you guys in the loop.

Hey doods;

So it seems it happened again...same problem, same conditions...

Deja vu for me....on a mapping mission this afternoon, I had a prop break mid flight. However, this time I have the prop. It seems this time, instead of the prop hub breaking, only one of the two rotors broke off the hub. So technically, I didn't lose a propeller. I only lost HALF a propeller.

Other than using my Phantom 4 an order of magnitude more than most guys, I'm doing nothing wrong.

So, once again I'm going to ask if any of you guys have seen prop failure. That's really the only information I can use at this point. Or if there are any plastics experts out there, perhaps they can look at the photos of the broken prop and share your thoughts.

Worth noting; the remaining 3 props remained essentially intact. One prop ejected upon impact. I know this to be true because the prop was a mere 8 feet from the drone (as opposed to 200' away had it ejected @ 300').

I've submitting an RMA to DJI. I purchased the Care Refresh for the replacement drone, which lasts a year from the purchase date mere weeks ago. The *warranty* ends May 10th. HA! So one way or the other, this will be replaced. Hopefully, sooner than later.

View attachment 98402 View attachment 98403

It's hard to believe this hasn't happened a second time...especially after DJI assured me it wouldn't.

Another thing worth noting, is that I notice the P4P props have the slightest amount of wiggle room on the hub. I can kind of rotate the prop 1° on the hub. They do the same on the Obsidian hub.

The Obsidian props, however, have zero tolerance. They are very tight on the hub. I think I'm going to purchase Obsidian props from now on.

D

 

[Harleydude]

I’ve not noticed any wiggle room on my stock P4 props. They fit snug and do not move. I wonder if this might be a contributor to your problem.

I believe it was. The aftermarket props had just a little wiggle in the hub...not much. But apparently enough to cause plastic fatigue, is my guess.

If the prop is getting unexpected vibration, it might be weakening the plastic, causing it to crack and ultimately fail.

Yep...my guess exactly.