Hi everybody!
Have a P3A, and I wounder if anybody know (or have tried) this cenario?
If i'm at a hight of for ex. 100m, and then make a fast landing by holding the left controller all way to the bottom.
Will the P3A decend quite fast, and as soon it comes close to ground, the bottom sensors takes over, and makes the landing safe.
(Or will the aircraft just make a crater?)
Anybody know or tried this?

I wouldn't hold it.  Why temp fate, lol. I always hand catch.

If you hold left stick all way to ground ... you will have a momentary 'bounce' in the air just a little bit of ground as the sensors feed data to Flight Controller.
The descent of course is the fastest CONTROLLED descent speed ... till that foot or so of ground. The landing will be 'untidy' ...

BUT and I know many will agree ... it is NOT a good idea to land all the way using LEFT stick down. Its far better to change near ground to YOU deciding and controlling the landing. You will still experience a little 'bounce' due to sensors - but at least YOU decide where and when to land.

Hi, thanks for the inquiry. We're hoping that you could get the best explanation in regards to your scenario that you've provided. We're always recommending our customers to push gently the left stick (mode2) to prevent sudden and unexpected elevation changes. Thank you for continued support. May you please always have a safe flight.

The Phantom 3 is limited in its vertical descent speed to 3m/s (~10ft/second).  This speed is deliberately limited to avoid a ring vortex state under the aircraft leading to a loss of control, preventing you flying into your own choppy, upset air beneath.  It really won't matter from how high you start, as it will quickly achieve that speed and descend no faster.  Landing and hitting the ground at that speed is survivable, but not recommended -- it is a heavy landing and you will hit quite hard.  In reality, as you get close to the ground, the down wash from the rotors will cause the air to get much denser, as the air no longer has anywhere to push down and out of the way.  This has the effect of creating a "cushion" of air that can slow and protect the aircraft to some extent in the last few centimeters before touchdown.

I'm not sure sensors play much of a part in this, as none of them are designed to tell you where the ground is.  The only ones likely to contribute anything are the VPS system if you have that turned on, they might assist in maintaining a stable and accurate altitude reading on the way down.  They don't take over and fly and land the aircraft for you though, you are still in control.  The best advice is to ease off on the stick as it is touching down, inputting less and less power the lower you get.  You can still land quickly and smoothly using this method.  It is similar to how an experienced driver brakes in a car.  You can come to a quick smooth stop by pressing the brake pedal hard , but lifting off the pressure in the last moments before stopping, eliminating that jarring shake at the end you experience when a novice is driving.  You probably do it subconsciously after developing some experience, landing is no different.

My advice for landing would be to descend to 1 or 2 feet and hover over your "landing pad", then pull the stick down gently, probably only a third of the way down and no more than 50% deflection until it touches down.  You might get a little bounce, but hold the stick down fully for a few seconds until the aircraft detects there is no movement, and the motors will disarm.

I am with Alabama regarding the "hand-catching". Be careful and you will not have any issues. Remember after grabbing your phantom, and holding your RC in the other hand, you must still hold the left stick down to kill the motors.
It is not hard and will prevent a hard landing on the ground, which could cause other problems for you. Landing the aircraft also on the ground is not hard, but I wouldn't just hold the stick down from any height and expect it to go perfect every time. Slowly bring it down to within a foot or so, then hold the left stick down. Or you can use the auto-land in your app, although I am not a big fan of that myself.