There has been a lot of confusion, speculation and misinformation about props coming off in flight. I decided to do some actual testing to demonstrate this failure. I used my F550 hex with only one prop attached. It has the same motors, props and flight controller as the earlier Phantoms but not the same as the P3.
In my first test, I installed the prop as loosely as possible and tried to make it fly off at idle speed by grabbing the motor bell. This was not successful. Just starting up the motor tightened the prop enough to keep it on. I also tried at higher speeds up to the point that the arm was bending as the bird tried to lift off. After multiple tries, I was able to make it fly off.
Note: in these videos, the props appear to be stopped or spinning slow when at idle speed. They are in fact spinning very rapidly but at a speed that is nearly in sync with the frame rate of the camera. Anyone who has shot video of props in flight will recognize this.
I tried holding the motor bell with one hand while spinning the prop on quickly so that it seated with a “thunk” against the shoulder. I also tried placing the prop on the very top of the shaft without spinning it at all and letting the motor wind up and seat it with an audible “thunk.” In these cases, it took considerable effort to remove the prop by hand, but a wrench was not necessary. Again, it took many tries even at high speed, to make a prop fly off.
This prop was a 9443 P2 prop without the composite hub so it would not have as much friction as the P3 props. The ESC does not have active braking, but I was grabbing it and bring the motor to a complete stop as quickly as I could by hand.
Next, I disconnected one of the 3 wires from the motor to the ESC and replaced it with a jumper wire that I could disconnect while the motor was running. This would simulate an ESC failure, power loss or bad solder joint failure in flight. I started up the motor as usual and ran it up to speed, then disconnected the motor wire. The motor stopped instantly. The prop flew way up in the air and trimmed my wife’s ferns hanging above. This was absolute, consistent and repeatable at different speeds.
For me, this issue is very clear. I believe if your prop comes off in flight, it was likely caused by an electrical failure. If you still believe otherwise after watching this, please do your own test and convince yourself or post the video if you can demonstrate a different result.
I would love to see a real test with the P3.