Fell out of the Air

[Bella]

Hi All. My Phantom 3 Std just fell out of the air at 30 meters. Fair bit of damage but obviously curious to know WHY ??

Two thoughts

1. Found the unit with one prop missing some 10 meters away ..maybe prop came off while flying ??

2. Was flying point of interest via P mode then decided to RTH and switched it to F mode ...maybe lost signal ??

Any suggestions would be appreciated.

 

[LuvMyTJ]

Lack of signal should make it hover or RTH depending on setting. They have been know to toss a prop and drop like that.
I always snug mine with the included tool. The newer DJI braking system makes it more prone to happen.

 

[msinger]

Post your flight log here so we can take a look. You can find instructions here if you need help retrieving your flight logs.

 

[phantom1972]

Hi All. My Phantom 3 Std just fell out of the air at 30 meters. Fair bit of damage but obviously curious to know WHY ??

Two thoughts

1. Found the unit with one prop missing some 10 meters away ..maybe prop came off while flying ??

2. Was flying point of interest via P mode then decided to RTH and switched it to F mode ...maybe lost signal ??

Any suggestions would be appreciated.

Questions like these get everybody's attention FAST. Note that from just observing a Phantom, that if a propeller comes off, or a motor stops, the craft will become inherently unbalanced, and "fall out of the air". I was thinking that if each motor had the capability of going forward OR reverse, with reverse only being used to balance out a missing motor thrust, I bet it could be stabilized. Moot point now. I'm 99+% sure you threw a prop (The reason is key), and anything else you were doing was probably just a coincidence.

It's interesting to note that in virtually every form of aircraft I can think of -- except quads -- more motors add redundancy and safety! Multi-engine airplanes being the obvious examples. With quads, it seems like having 4 motors give you 4X the chance of falling out of the sky, due to an engine failure. LOL Right?

 

[LuvMyTJ]

Questions like these get everybody's attention FAST. Note that from just observing a Phantom, that if a propeller comes off, or a motor stops, the craft will become inherently unbalanced, and "fall out of the air". I was thinking that if each motor had the capability of going forward OR reverse, with reverse only being used to balance out a missing motor thrust, I bet it could be stabilized. Moot point now. I'm 99+% sure you threw a prop (The reason is key), and anything else you were doing was probably just a coincidence.

It's interesting to note that in virtually every form of aircraft I can think of -- except quads -- more motors add redundancy and safety! Multi-engine airplanes being the obvious examples. With quads, it seems like having 4 motors give you 4X the chance of falling out of the sky, due to an engine failure. LOL Right?

You forgot about helicopters & tricopters. Theres always the hexacopter if this troubles you.
But yeah, something held up by it's four corners will fall if you remove one of the corner supports.

 

[bobmyers]

Questions like these get everybody's attention FAST. Note that from just observing a Phantom, that if a propeller comes off, or a motor stops, the craft will become inherently unbalanced, and "fall out of the air". I was thinking that if each motor had the capability of going forward OR reverse, with reverse only being used to balance out a missing motor thrust, I bet it could be stabilized. Moot point now. I'm 99+% sure you threw a prop (The reason is key), and anything else you were doing was probably just a coincidence.

It's interesting to note that in virtually every form of aircraft I can think of -- except quads -- more motors add redundancy and safety! Multi-engine airplanes being the obvious examples. With quads, it seems like having 4 motors give you 4X the chance of falling out of the sky, due to an engine failure. LOL Right?

They need to engineer a motor for the center that would support the weight if one went out j/k

 

[Bella]

Sounds like I "threw a prop" since it was not damaged and meters away from crash site ... But how did this happen ?? Did I not tighten enough or some other reason ?

 

[bobmyers]

Sounds like I "threw a prop" since it was not damaged and meters away from crash site ... But how did this happen ?? Did I not tighten enough or some other reason ?

Can you define meters-- 10 or 50 or 100??

 

[Bella]

25 metres

 

[bobmyers]

25 metres

That's pretty close 75 ft-- may not have thrown it off-- I would think a prop coming off at 30 meters in height would float or gyro away further than 75 ft. ?? but maybe not.???

 

[Bella]

Does anyone know why and how a prop could come off ??

 

[bbfpv]

Does anyone know why and how a prop could come off ??

If the motor seized.

 

[syotr]

Does anyone know why and how a prop could come off ??

Loss of one phase to the motor will make it seize up. Inertia makes the prop spin off. Phantom will fall out of the sky even if the prop stayed on. Prop coming off is likely an effect rather than the cause.
Some say that active braking on the P3 will make a loose prop come off, but no one has demonstrated this actually happening.
Loss of phase can happen when there is some glitch with the ESC, bad solder joint, MOSFET failure, wire break, or any bit of conductive material shorting out the ESC.

 

[Lonewolf]

Lack of signal should make it hover or RTH depending on setting. They have been know to toss a prop and drop like that.
I always snug mine with the included tool. The newer DJI braking system makes it more prone to happen.

According to DJI they suggest "Finger Tight Only" I would think even slightly overnighting especially the newer composite hub props can cause the hub to crack using the provided tool. Unlike the aluminum hub props.

However, I CAN see how the aluminum hub props COULD spin off with the newer aggressiveness of the braking system. Perhaps why the composite props are recommended because they "Grab" the hub better than the aluminum hub props.

 

[syotr]

Props would have to be really loose for braking to make them spin off. Normally, just starting the motors makes a loose prop snug up tight. You can see in this video, that it is possible to grab the motor bell and make a loose prop come off. It took several tries with very loose props. At the end of the video you can see what happens when one of the three motor wires is disconnected. The motor locks up instantly and throws off the prop which was pretty snug to start with.