Propeller apparently broke off mid flight...

[Harleydude]

Hey doods;

Flying a mapping job today, my P4P suddenly went into a spin and fell to the ground. She was about 1/2 mile away and about 200' AGL, so I didn't see the actual event (it's a miracle we found her), but my telemetry and camera showed the bird spinning to the ground for no apparent reason. I suspected a bad motor, ESC, or prop. Forensics indicate a prop must have broken. The motor spins fine. The propeller lock is intact. The only explanation is that a prop broke mid-flight.

Has anyone here experienced a broken prop mid flight for no apparent reason? This was the original factory prop that came with the bird. I had < 30 flights on the P4P and the props.

Here's some forensic data...

GPS health = 5 out of 5.

Right-rear motor and prop lock undamaged:

Prop mounts normally and locks positively:

I can't wait to see what DJI says about this...<sigh>....

D

 

[msinger]

Forensics indicate a prop must have broken. The motor spins fine. The propeller lock is intact. The only explanation is that a prop broke mid-flight.

It looks like you lost the prop mid-flight. Where was that prop when you retrieved your Phantom?

 

[Harleydude]

It looks like you lost the prop mid-flight. Where was that prop when you retrieved your Phantom?

Never found it. The two left props were still on the bird and intact. The prop for the right-FRONT motor was found, but broken in two (which is understandable since the right-front motor is destroyed in the crash). The only prop NOT found was from the right-rear motor. This is conducive of prop failure @ altitude. The prop either takes off in a completely different direction as the bird, and/or it's so lightweight that the wind takes it far from the crash sige.

As you can see in the photos, the right rear motor is pristine. I attached a propeller and the locking mechanism is in perfect condition. Yet that's the motor that revved up to double its nominal flight RPM. The only possible conclusion is that the prop (not the motor nor the locking mechanism) busted in mid-flight.

 

[sar104]

Never found it. The two left props were still on the bird and intact. The prop for the right-FRONT motor was found, but broken in two (which is understandable since the right-front motor is destroyed in the crash). The only prop NOT found was from the right-rear motor. This is conducive of prop failure @ altitude. The prop either takes off in a completely different direction as the bird, and/or it's so lightweight that the wind takes it far from the crash sige.

As you can see in the photos, the right rear motor is pristine. I attached a propeller and the locking mechanism is in perfect condition. Yet that's the motor that revved up to double its nominal flight RPM. The only possible conclusion is that the prop (not the motor nor the locking mechanism) busted in mid-flight.

That's not the only possible conclusion, and more likely it simply wasn't properly locked in the first place. Otherwise it would require both the locking tabs in the hub to fail.

 

[Harleydude]

That's not the only possible conclusion, and more likely it simply wasn't properly locked in the first place. Otherwise it would require both the locking tabs in the hub to fail.

As much as I hate holding hands through forensic evidence....SIX MINUTES the bird flew well over a mile (check the provided chart). Have you ever misinstalled a prop on a P4P locking system? Try it sometime. It doesn't take 6 minutes and 1.5 file miles @ 25+mph to "fall off." It's either locked, or it isn't. There is no in between.

There's always one in every bunch....

 

[sar104]

As much as I hate holding hands through forensic evidence....SIX MINUTES the bird flew well over a mile (check the provided chart). Have you ever misinstalled a prop on a P4P locking system? Try it sometime. It doesn't take 6 minutes and 1.5 file miles @ 25+mph to "fall off." It's either locked, or it isn't. There is no in between.

There's always one in every bunch....

I've no idea why you would ask for advice and then respond like that. There have been a number cases where the bayonet system detached after some time in the air - typically due to a sudden motor deceleration. It's also possible that grit or other foreign objects could prevent the hub from locking. Anyway - I'll leave you to your own "forensic" work since you are obviously so expert at it.

 

[msinger]

The only possible conclusion is that the prop (not the motor nor the locking mechanism) busted in mid-flight.

One thing is sure -- the prop detached mid flight. Proving the prop was damaged after your Phantom took off is going to be hard to prove.

 

[Harleydude]

I've no idea why you would ask for advice and then respond like that. There have been a number cases where the bayonet system detached after some time in the air - typically due to a sudden motor deceleration. It's also possible that grit or other foreign objects could prevent the hub from locking. Anyway - I'll leave you to your own "forensic" work since you are obviously so expert at it.

Okay....forgive my impatience. I apologize. But, again, I have to point out the VERY clear cut forensic evidence which does NOT show the motor spinning down, but spinning up. And while I concede that it's possible to install a prop without locking it, I will never concede that it took 6 minutes and 1.5 miles to spin off. I would challenge you to "half install" a P4P prop in such a way that it doesn't either fail immediately (PRIOR to take off), or self lock on spin up. The props are designed in such a way that the rotation of the motor and drag of the props pushes them toward the locking position. OR...you could misinstall the prop completely, in which case the prop would just spin OFF at spin up. This is the reason of the double "rev" of the motors when you first start the bird. This double rev would either spin off the prop completely, or lock it into place.

The reason for my response/impatience is I'm getting a sense that you aren't really examining all the evidence I pain-stakingly provided.

 

[Harleydude]

One thing is sure -- the prop detached mid flight. Proving the prop was damaged after your Phantom took off is going to be hard to prove.

Touché. I think the one thing I have on my side is that the recovered bird shows no other signs of damage or wear on the failing right-rear motor. Luckily for me, that motor was undamaged in the crash. It would be tough to form any other conclusion other than prop failure 6 minutes into flight. Fortunately for you and I, the DJI locking system is designed to either fail at take off, or self lock. There is no in between. It's either locked, or not. Period. I think this weighs heavily in my favor.

 

[sar104]

Okay....forgive my impatience. I apologize. But, again, I have to point out the VERY clear cut forensic evidence which does NOT show the motor spinning down, but spinning up. And while I concede that it's possible to install a prop without locking it, I will never concede that it took 6 minutes and 1.5 miles to spin off. I would challenge you to "half install" a P4P prop in such a way that it doesn't either fail immediate PRIOR to take off, or self lock on spin up. The props are designed in such a way that the rotation of the motor and drag of the props pushes them toward the locking position. OR...you could misinstall the prop completely, in which case the prop would just spin OFF at spin up. This is the reason of the double "rev" of the motors when you first start the bird. This double rev would either spin off the prop completely, or lock it into place.

The reason for my response is I'm getting a sense that you aren't really examining all the evidence I pain-stakingly provided.

No - I looked at your evidence and it is basically identical to other cases with similar outcomes. The motor spin-up always occurs when this happens as the load on the motor decreases (no prop) and the FC attempts to correct for the lack of lift (you will find that motor PPM also went to 100%). I have several sets of data showing exactly that behavior.

And while I understand your skepticism that the mechanism can hold on for any length of time while not properly attached, the simple fact is that it has happened, with the prop actually recovered in a few cases and found to be intact, if I recall correctly. As a a result, I always attempt to counter-rotate the prop after installing, just to make sure that the locking lugs have engaged in the hub. Maybe a couple of times I've found that they haven't, but never attempted to launch like that of course.

So, my point is that based on previous experience examining the logs of these events, the most likely explanation is simple prop loss due to incomplete lock. Complete hub failure would likely look very similar in terms of telemetry and motor behavior, but I've never seen any reports of such failure.

 

[Harleydude]

No - I looked at your evidence and it is basically identical to other cases with similar outcomes. The motor spin-up always occurs when this happens as the load on the motor decreases (no prop) and the FC attempts to correct for the lack of lift (you will find that motor PPM also went to 100%). I have several sets of data showing exactly that behavior.

I concur...absolutely.

And while I understand your skepticism that the mechanism can hold on for any length of time while not properly attached, the simple fact is that it has happened, with the prop actually recovered in a few cases and found to be intact, if I recall correctly.

With all due respect, I would have to see evidence of this. Second-hand anecdotes (a friend of a friend had this happen) is very unconvincing. Can you at least provide the person this happened to so I could speak with them??? Dollars to doughnuts, I could make a video to refute this completely. It would be very easy to half-install a prop, which would then either self lock, or spin off completely. I may have to make this video just to put the "propeller remained half installed for 6 minutes" theory to rest.

As a a result, I always attempt to counter-rotate the prop after installing just to make sure that the locking lugs have engaged in the hub.

My friend, I have been doing this a long time. I ALWAYS check prop tightness every flight. It's a habit. Years of flying many birds many times, and I've only had two catastrophic events - both due to prop spin off.

Maybe a couple of times I've found that they haven't, but never attempted to launch like that of course.

Of course.

So, my point is that based on previous experience examining the logs of these events, the most likely explanation is simple prop loss due to incomplete lock.

I agree with your "prop loss" assessment. Your "incomplete lock" theory is completely implausible. I would challenge you to half lock a prop that didn't either self lock before take off, or spin off completely. I'll do research into this. But the P4P system is like gen 10 of many different locking systems. It's designed to be sold to the masses at Best Buy. Read; idiot-proof. Even the double spinning of the motors is designed to either lock or spin off a misinstalled prop.

Complete hub failure would likely look very similar in terms of telemetry and motor behavior, but I've never seen any reports of such failure.

Neither have I. Hence this thread and my question, "Has anyone here experienced a broken prop mid flight for no apparent reason?" I was very specific on purpose. I honestly wanted to avoid erroneous theories and "friend of a friend" anecdotes. But I appreciate your contribution.

 

[sar104]

With all due respect, I would have to see evidence of this. Second-hand anecdotes (a friend of a friend had this happen) is very unconvincing. Can you at least provide the person this happened to so I could speak with them??? Dollars to doughnuts, I could make a video to refute this completely. It would be very easy to half-install a prop, which would then self lock, or misinstall a prop completely, which would then spin off. I may have to make this video just to put the "motor remained half installed" theory to rest.

I'm not offering anecdotes - I'm referring to the results of log analysis (mine and other's) of accident reports on this forum. I'm going to let you search for those if you are interested, which I get the impression you probably are not. It's not my responsibility or interest to convince you one way or the other. Good luck with your efforts with DJI - they have been fairly generous in a number of prop loss cases.

Be careful if you do try to make a video and remember that it's hard to prove a negative.

 

[Harleydude]

I'm not offering anecdotes - I'm referring to the results of log analysis (mine and other's) of accident reports on this forum.

So this happened to you? You misinstalled a propeller that flew off a mile later?

I'm going to let you search for those if you are interested, which I get the impression you probably are not.

You mean research, as in, joining a P4P-specific forum? And then asking the body a specific question, like...oh....I don't know, "Has anyone here experienced a broken prop mid flight for no apparent reason?"

Okay...I'll give that a shot, and see how it works out for me.

It's not my responsibility or interest to convince you one way or the other.

Hint: I'm doing the research now. This forum IS the research.

Good luck with your efforts with DJI - they have been fairly generous in a number of prop loss cases.

Yes, I posted a video in my response that shows a prop loss, and is notated to have been warranted by DJI.

Be careful if you do try to make a video and remember that it's hard to prove a negative.

My friend....proving that a half-tighted prop will either fly off or self tighten as soon as the motors spin up will be a piece of cake.

Oh, for the love of all that is holy....I just made the **** thing....

If THIS doesn't do it, then I have no idea what will.

 

[sar104]

So this happened to you? You misinstalled a propeller that flew off a mile later?





You mean research, as in, joining a P4P-specific forum? And then asking the body a specific question, like...oh....I don't know, "Has anyone here experienced a broken prop mid flight for no apparent reason?"

Okay...I'll give that a shot, and see how it works out for me.






Hint: I'm doing the research now. This forum IS the research.





Yes, I posted a video in my response that shows a prop loss, and is notated to have been warranted by DJI.






My friend....proving that a half-tighted prop will either fly off or self tighten as soon as the motors spin up will be a piece of cake.

Oh, for the love of all that is holy....I just made the **** thing....

If THIS doesn't do it, then I have no idea what will.

I've revised my opinion back to my original one. You really have a seriously bad attitude problem. If you really imagine that your half-baked efforts to replicate all possible outcomes of an improperly installed prop are definitive then it's completely pointless trying to reason with you.

 

[dirkclod]

Guys agree to disagree and move on .

 

[Sixgun89]

Is it possible there was a mid flight strike of some kind?

 

[Harleydude]

Is it possible there was a mid flight strike of some kind?

No.

 

[Bakersfield Quad]

Perhaps the spring locks are weak or have a disengagement problem? Otherwise, no idea, if a strike is out. I do agree, if it is on, then is should stay on, but there are possibilities that inside the prop hub, something is broken there, but of course without it, no proof. Good luck.

 

[Harleydude]

Perhaps the spring locks are weak or have a disengagement problem?

I just tested spring tension on the failed motor. It is equal to the other 3 motors, and relatively stiff.

Otherwise, no idea, if a strike is out. I do agree, if it is on, then is should stay on, but there are possibilities that inside the prop hub, something is broken there...

My theory, exactly. I did some Internet research, and I have found 2 other people that this happened to. Like me, the only explanation can be prop failure. Either the prop simply broke in half, or, as you suggested, the prop hub failed. The latter seems more likely to me.

, but of course without it, no proof. Good luck.

I think I have a pretty good case. The log files are pretty clear. I also tried to see if "half installed" prop would stay on the motor past motor spin up. They don't. I made a video:

Another guy made the same video. His audio is horrible, but you get the point.

I'll contact DJI Monday. They covered my old Phantom 1 when the prop spun off, citing a design flaw.

D

 

[PhantomWetSuits]

So this happened to you? You misinstalled a propeller that flew off a mile later?





You mean research, as in, joining a P4P-specific forum? And then asking the body a specific question, like...oh....I don't know, "Has anyone here experienced a broken prop mid flight for no apparent reason?"

Okay...I'll give that a shot, and see how it works out for me.






Hint: I'm doing the research now. This forum IS the research.





Yes, I posted a video in my response that shows a prop loss, and is notated to have been warranted by DJI.






My friend....proving that a half-tighted prop will either fly off or self tighten as soon as the motors spin up will be a piece of cake.

Oh, for the love of all that is holy....I just made the **** thing....

No.

Sorry I had to post on the second page,