Early Phantoms had their motors vertically aligned but from the P3 series they were offset to prevent Vortex Ring State (VRS).
But surely you knew that?
I don't own a Phantom.
I can, however, fly a helicopter, and we usually call it
Settling with Power. And yes, I know what it is.
What I don't see is how tilting the rotors slightly would alleviate it.
There are three elements to this phenomenon, and all three must be present for it to occur:
- The rotor is generating sufficient downward thrust
- The vehicle has a significant rate of descent
- The rotor disc has insufficient horizontal motion to be in Effective Translational Lift (ETL)
I'm not seeing how the slight angling of the downwash would do anything significant to alter any of these factors.
because of what
@Meta4 stated,it also help keep the aircraft stable as it descends and allows a quicker descent as well
I've noted that the DJI software limits the rate of descent the pilot can command to a value noticeably less than what you can command for climb. That strikes me as the most effective preventative action against settling with power as it eliminates factor #2.
That said, if you wish to take extra steps to ensure you avoid it, simply maintain a good horizontal component to your speed when coming down.
And if you are descending straight down, and get into the phenomenon, the correct procedure to escape it is to reduce downward thrust (alleviate factor #1), and apply cyclic in any direction (alleviate factor #3). In a helicopter, that usually means forward (most efficient and usually safest direction), but in a quadcopter I don't think it would matter. It is simply that the quickest way to clear the vortex is to move horizontally.
The numbers for rate of descent and ETL depend on the aircraft -- I could tell you what they are for R-22 and R-44 helicopters, but I have no idea what they are for our drones. But ETL occurs essentially by definition from the minimum (or greater) horizontal speed necessary to prevent settling with power.
What I'd like to know is why angling the thrust vector slightly inwards on drones makes a difference. If anyone has information on that, I'd appreciate it.