Propeller Flew off when Flying

[soulphantomflyer]

It looks like @With The Birds answered your same question yesterday in this thread.
Propeller Flew off when Flying

His answer only applied in that the 2 back motor reduce rpm by a fiction causing the angle of quad to tile forward thru braking

Just think for a second people. If the slow down of the 2 back motor is so severe that the prop will back out of the tread. The quad would have somersault long before anything else would happen.


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[matti]

I have only once very carefully attached the props when my P3P was new. This is why I'd like to get a bag that allows me to put the P3P in with props, so I don't have every time to make sure they are correctly attached.

Once the props are correctly attached, they are, until they are somehow physically damaged in a crash or after many flights (or say, after two years or so), right??

 

[Oso]

The reason for a prop to fly off :
1. Not snug fit, not sitting properly
2. Internal damage to threads
3. Excessive suddenly braking

One doesn't need a tool to tighten them, let it freely rotate to tighten and give extra quarter turn with one finger holding the rotor with hand is more than enough.

Isn't it amazing how many threads we can have on the same topics?

In my humble opinion only, when a prop is lost the root cause is #1 above a large majority of the time. #3 is not a root cause but a result of #1.

I have always thought that some pilots, especially new pilots, are misled by the term "self tightening." I think that many spin down their props until they stop and then fly, but don't realize that some props don't always freely spin down all the way. Some props stop after a couple of threads and need a little help to spin down the rest of the way. If that doesn't happen, the prop is not secure and is at more of a risk to unscrewing during hard braking, etc.

My experience and opinion align with something that has been noted literally countless times in countless prop threads - if you spin the props all the way down, hold the motor and then tighten the prop a bit more, the props will not come off in normal use. Of course this assumes that your preflight check has verified no damage to any props before installing and also that you don't collide with anything in flight.

 

[soulphantomflyer]

Isn't it amazing how many threads we can have on the same topics?

In my humble opinion only, when a prop is lost the root cause is #1 above a large majority of the time. #3 is not a root cause but a result of #1.

I have always thought that some pilots, especially new pilots, are misled by the term "self tightening." I think that many spin down their props until they stop and then fly, but don't realize that some props don't always freely spin down all the way. Some props stop after a couple of threads and need a little help to spin down the rest of the way. If that doesn't happen, the prop is not secure and is at more of a risk to unscrewing during hard braking, etc.

My experience and opinion align with something that has been noted literally countless times in countless prop threads - if you spin the props all the way down, hold the motor and then tighten the prop a bit more, the props will not come off in normal use. Of course this assumes that your preflight check has verified no damage to any props before installing and also that you don't collide with anything in flight.

I agree with you on this 100%


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[alokbhargava]

Isn't it amazing how many threads we can have on the same topics?

In my humble opinion only, when a prop is lost the root cause is #1 above a large majority of the time. #3 is not a root cause but a result of #1.

I have always thought that some pilots, especially new pilots, are misled by the term "self tightening." I think that many spin down their props until they stop and then fly, but don't realize that some props don't always freely spin down all the way. Some props stop after a couple of threads and need a little help to spin down the rest of the way. If that doesn't happen, the prop is not secure and is at more of a risk to unscrewing during hard braking, etc.

My experience and opinion align with something that has been noted literally countless times in countless prop threads - if you spin the props all the way down, hold the motor and then tighten the prop a bit more, the props will not come off in normal use. Of course this assumes that your preflight check has verified no damage to any props before installing and also that you don't collide with anything in flight.

Agreed.

There are many threads which keep repeating. Thats one of the the ways this forum is GROWING

 

[Gary M]

Ever since I first read about props coming off in flight, I started flying a lot more gently. Especially at the end of a fast run to gain distance. I now progressively reduce the throttle from full gas to zero over the space of a good few seconds. Braking can be extreme. I'd rather not risk a flying prop!

Of course when you are cruising at a good clip and then suddenly stop, you can see that the bird decelerates aggressively. But one day I was filming and the bird was RTH after a litchi flight. When it got closer to me, I switched over and took back control and the bird stopped VERY fast. When I saw what that looked like on the video I took I was stunned. The camera/gimbal violently jerked around and my screen turned blue for a brief second. Is this even good for your gimbal? Since then I have been doing what you described. No more letting go of the stick and just letting it stop. When cruising at high speed it may take me 5-10 seconds to decelerate, but oh well. Looks like the potential prop issue is another reason to continue braking this way.

 

[With The Birds]

Please tell me I am wrong. Because I don't get it

Unlike a real plane, there is no brake or reversal thrust on a quad
When people say braking or as in full throttle forward then to stop forward momentum(braking). All a quad do is reverse the tilt of the quad, in fact the faster a motor spin. Faster the forward momentum will stop when a reverse quad tilt applied.

Am I wrong in this?


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His answer only applied in that the 2 back motor reduce rpm by a fiction causing the angle of quad to tile forward thru braking

Just think for a second people. If the slow down of the 2 back motor is so severe that the prop will back out of the tread. The quad would have somersault long before anything else would happen.


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The part you may be missing is that the motors on the phantom 3 can and do decelerate much faster than those on earlier models. When DJi talks about braking they are refferimg to the motor RPM rapidly transitioning to a lower commanded RPM as determined by the flight controller. The new ESC produce a true sine wave drive. Motor RPM is precisely locked to line frequency. The ability of the motor to rapidly reduce RPM must mean the propellor, due to its stored energy, will be trying to travel faster than the motor during the decelleration and could come undone if not installed correctly.

I have sine wave drives feeding spindle motors on CNC routers. I have had collet nuts loosen due to the same principal.

 

[Ghost Rider]

Quadcopter flight is just the various speed of the four motors. The props spin off under "heavy braking" because two of the motors slow way down drastically and if your prop breaks free, it keeps spinning as the shaft essentially stops. Bye bye prop.

I now am more aware of my props. Since my incident.

 

[pe9999]

I started tightening mine a little more after finger-tight. Heard stories lately of props slinging off.

don't over-tighten the phantom and 3dr self tighten prop, both quads will tighten themselve when they were armed. overtighten them may crack the hub and cause prop flyoff.

 

[outlaw95]

I've also been the victim of a prop flying off. I threw my p2v+ together in a hurry to try and catch a sunset.

 

[Ghost Rider]

don't over-tighten the phantom and 3dr self tighten prop, both quads will tighten themselve when they were armed. overtighten them may crack the hub and cause prop flyoff.

That's what I thought too. $650 later, I'm no longer a believer.

 

[snerd]

That's what I thought too. $650 later, I'm no longer a believer.

Yep! Tighten a tad more............... you can feel when it's good and tight and before doing damage. At least I can.

 

[soulphantomflyer]

Quadcopter flight is just the various speed of the four motors. The props spin off under "heavy braking" because two of the motors slow way down drastically and if your prop breaks free, it keeps spinning as the shaft essentially stops. Bye bye prop.

I now am more aware of my props. Since my incident.

I think you are wrong on this

Yes quad flight is various of 4 motor which tilt the quad in order to go any direction you want

but

Basically air is static, prop is basically passive except for brief micro second on motor deceleration, on self tightening prop quad, the motor will alway go one direction" just faster-slower," the prop depend on pitch will always cause air drag vs motor rpm!
If you really think about it, it doesn't matter if the motor is rotating at 10 rpm or 10000 rpm. It will continue to try and lock up that prop. The only difference is how much force it is using to tightening that prop



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[4wd]

Yep! Tighten a tad more............... you can feel when it's good and tight and before doing damage. At least I can.

You would think so, but not everyone has even basic mechanical judgement.
I came across this from someone's DIY oil change...

 

[Ghost Rider]

I think you are wrong on this

Yes quad flight is various of 4 motor which tilt the quad in order to go any direction you want

but

Basically air is static, prop is basically passive except for brief micro second on motor deceleration, on self tightening prop quad, the motor will alway go one direction" just faster-slower," the prop depend on pitch will always cause air drag vs motor rpm!
If you really think about it, it doesn't matter if the motor is rotating at 10 rpm or 10000 rpm. It will continue to try and lock up that prop. The only difference is how much force it is using to tightening that prop



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Yeah I get what you're saying. Motor slows down the prop should just tighten more. Then I have no clue how my prop came off.

 

[jonebk12]

Yeah I get what you're saying. Motor slows down the prop should just tighten more. Then I have no clue how my prop came off.

No the prop tightens as the motor speeds up - that's how the threads are oriented. When the motors rapidly slow down, the props want to keep spinning fast (angular momentum). If they aren't installed tight enough, presumably they could spin off under braking. The props only tighten in one direction.

 

[Ghost Rider]

No the prop tightens as the motor speeds up - that's how the threads are oriented. When the motors rapidly slow down, the props want to keep spinning fast (angular momentum). If they aren't installed tight enough, presumably they could spin off under braking. The props only tighten in one direction.

That's what I said the first time until I was "wrong". So I just stopped trying to figure it out.

When I studied the characteristics of these motors, I determined the same thing. But someone told me I was wrong and I don't feel like going back and figuring it all out again. I'm pretty sure I understand the mechanics of the systems on these things.

 

[With The Birds]

I think you are wrong on this

Yes quad flight is various of 4 motor which tilt the quad in order to go any direction you want

but

Basically air is static, prop is basically passive except for brief micro second on motor deceleration, on self tightening prop quad, the motor will alway go one direction" just faster-slower," the prop depend on pitch will always cause air drag vs motor rpm!
If you really think about it, it doesn't matter if the motor is rotating at 10 rpm or 10000 rpm. It will continue to try and lock up that prop. The only difference is how much force it is using to tightening that prop



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Lets say the motor is running at 10k rpm, agreed the prop is producing thrust so there is some load applied opposing the handing of the thread in the hub. If anything it will tighten.

Now lets say the flight controller isssues a command to the ESC to reduce to 5K RPM. The commanded decelleration only has to exceed the natural temdancy of the prop to act against the applied load momentarily for a situatiom to be encountered where the prop will try and spin off. Think about 5K to 0 rpm rather than 10K to 5K and you will appreciate what is going on here.

Dji abandoned metal hubs with the new motor ESC configuration in an attempt to avoid this.

 

[Suntana]

The reason for a prop to fly off :
1. Not snug fit, not sitting properly
2. Internal damage to threads
3. Excessive suddenly braking

One doesn't need a tool to tighten them, let it freely rotate to tighten and give extra quarter turn with one finger holding the rotor with hand is more than enough.

Or 4. purchase of cheap after market props


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[Quadcopterpilot]

When I first started flying I only spun the props on until they stopped, never had an issue over 20hrs of flying.
After reading about prop issues on this forum I started spinning them on until they stop and then hand tightening 1/4 turn, still have had no issues after 200hrs of flying. Just stating my experience.