I went out flying today, and mid flight had a really strange experience that could have turned bad. 

I was in the last 10% of my battery, getting ready to bring it in and change packs when (at around 300ft altitude) I heard two distinct "pop" sounds in rapid succession, the quad started wobbling all over the place, and my video reception almost completely cut out. I was pretty much right overhead with perfect RSSI before it happened, and it was all I could do to bring it down to a safer altitude slowly, and try to recover it, but ultimately it got far enough away that I lost all reception (reception became EXTREMELY weak right away after the "pop" sounds), and I hit the failsafe close to the ground. 

At first I was kind of worried that I'd lost the drone, as a big rain storm was moving in and was likely to hit within an hour, and I was unable to use the RapidFire's "find drone" feature because it was picking up no signal whatsoever (in spite of it having gone down within range that it shouldn't have been a problem). Luckily, I was recording the goggle feed when I went down, so I was able to replay it and find approximately where it crashed, and then get close enough to hear the beeper function sounding. 

When I found the drone there were only two obvious issues: 1) the antenna cable had pulled out, and 2) one of the blades on one of the props had a clean break and was gone. The broken piece of the blade was not at the crash site where I found the drone. 

The best thing that I can figure is that, right before the crash I was climbing at close to full throttle, and *maybe* the centrifugal force caused one of the blades to explode, and maybe that severed blade hit the antenna cable and caused it to detach? That would thus explain why my controls went to garbage and why I lost almost all my signal so suddenly. 

The blades were only used for about a half hour of flying before today and they hadn't been in any crashes. 

They were Luminier 3'' blades, if that makes a difference at all. 

I'm just wondering if, moving forward, I have to be worried about this happening again, or if I can fly with confidence that this was a pretty freak accident. 

Thanks for your feedback!

That shouldn't happen. The only thing I can think of is a manufacturing defect with the props. The Lumenier props are made of polycarbonate so they should be a bit flexible and resistant to breaking which means they should be reasonably durable. Unless there was something wrong with them they certainly shouldn't just explode in mid flight.

Check the other ones you have for any hairline cracks or obvious manufacturing defects in case there is a batch of them that all have issues.

It may be worth contacting GetFPV to report the problem and ask if they have had any other reports from other users of the same.

I was pretty surprised too, because I had actually been flying with the same type of blade for the first week and had a few minor crashes, but nothing that broke the blades. They had some dings and scratches though, so I decided to change them out with a new set, and those are the ones that I was flying when the thing happened today. I switched the blades and flew it again after the crash with zero problems whatsoever.

I also watched the video again since I posted the question, and it's really hard to tell. Everything is just going fine, and then *boom* reception cuts and flight is extremely erratic.

I may reach out to GetFPV and ask them about it as you suggested. I'm just really happy that it didn't cost me a drone!

(26-Aug-2020, 11:45 PM)TheLostAlaskan Wrote: I may reach out to GetFPV and ask them about it as you suggested. I'm just really happy that it didn't cost me a drone!

Even if you get nothing out of it, logging a report with them will at least make them aware that they may have produced a bad batch of props that are out in the wild in case anyone contacts them with the same problem.

Maybe you already know this, but be aware that when you use the model finder function on your goggle module you should remove one of the antennas and only use a directional patch.

(26-Aug-2020, 11:54 PM)SnowLeopardFPV Wrote: Even if you get nothing out of it, logging a report with them will at least make them aware that they may have produced a bad batch of props that are out in the wild in case anyone contacts them with the same problem.

Maybe you already know this, but be aware that when you use the model finder function on your goggle module you should remove one of the antennas and only us a directional patch.

Will contact them as soon as this reply is posted. 

And actually I did not know to remove the omnidirectional antenna. It makes sense that you'd only want to follow the signal of the directional patch, but I hadn't thought of removing the other one. 

I wonder if it would have helped, as I have a reading in the goggles when I'm using the "Find Model" feature where it shows the signal that each individual antenna is picking up, but in this case, I wasn't getting any signal at all up until I had visual contact with the drone itself. I suspected that it had to do with the VTX antenna becoming disconnected. 

As always, your insight is seriously appreciated! I actually connected to another model quad yesterday, and with the stuff you gave me to troubleshoot my first one, I was able to get it all figured out no problem. It may be a slow process, but I'm learning 

I would definitely contact them. I have been flying the Lumenier 3x4x3's for a few years and have never had an issue. I have had other props split at the hubs, but never any of the Lumeniers.

How tight were the prop nuts?

(27-Aug-2020, 02:15 AM)kaitylynn Wrote: I would definitely contact them.  I have been flying the Lumenier 3x4x3's for a few years and have never had an issue.  I have had other props split at the hubs, but never any of the Lumeniers.

How tight were the prop nuts?

Did indeed contact them. I also expressed gratitude for their help in getting me into the hobby so as to make sure it wasn't coming off as a complaint. Was just trying to make them aware, if indeed that's what happened--which I really can't know for sure. I've watched the footage back, but it's really, really hard to tell. All I can see is that the quad makes a hard and sudden dip (which was not from my radio input) and I vividly remember hearing two soft "pop" sounds. My girlfriend was standing beside me and she confirmed hearing the same thing. So it dips suddenly, and the video goes to crap immediately. Then, at the crash sight I found no sign of the broken blade piece. And like I said in my first post, I killed the motors before it crashed (from about 3-5 feet altitude). 

So I don't know. Maybe it was something else, but the fact that she flew so well on the next battery pack makes me suspicious.

I have had props explode a couple of times. It happens ....

just buy another brand

It would be interesting to know who makes the blades for Luminier.  Most of what Luminier sells is re-branded products, making very little themselves.  A few blade manufacturers are having issues with making reliable blades, but most of those are 7 inch blades.  I haven't read of a big problem with 3 inch blades.  Absent that, over tightening the blade nuts can lead to failure.  And if you have a blade from a manufacturer that has reliability issues and it is exposed to crashes, it certainly won't make them more reliable.   

I agree with JASC, change to a different brand and move on. 

How was your antenna attached? Sound like maybe is rolled into the propeller?

(27-Aug-2020, 01:17 PM)kaitylynn Wrote: How was your antenna attached?  Sound like maybe is rolled into the propeller?

When I first read your comment, that actually sounded like it might could have been what happened. But I just pulled out the quad and looked at it, and I don't see any way that the propeller could have struck the antenna or antenna cable. The antenna is mounted in a 3d printed housing.

I just picked up an 85X - set it all up with blades off - installed them and found cracks because I tightened them too much (and used lock tite) - basically crushing the hubs - installed the included replacement set and just set the screws flush

(30-Aug-2020, 12:16 AM)julian46 Wrote: I just picked up an 85X - set it all up with blades off - installed them and found cracks because I tightened them too much (and used lock tite) - basically crushing the hubs - installed the included replacement set and just set the screws flush

I forget the name for it, but mine are the type that do not have nuts. Forgive my forgetting, but it's something like PIP--where bearings hold the blades in place. But a few people have mentioned that if you tighten the nuts too much it can crack the blade. 

I've just finished a build of the Tyro 119, which has nuts that hold down the blades, so I'll be cautious to not tighten them too much.

if the prop "cracks" while tightening something is wrong with the material. if you truly destroy props by tightening, you should get an x-class xD
the only problem about tightening is you should be able to loosen the nut again, but there isnt much force needed with a good locknut, there isnt any loctite needed for a t-mount prop. tighten the screw or nut again after the first flight... works best for me

Thread lock and plastic don't mix, so getting it anywhere near plastic propellers is a very bad idea as it causes plastics to crack.