How does the Feather Fall spell work on a flying character falling unconscious? What if it's the caster?

Question

Playing a flying race (the only one in the group) and still low level (10hp/13AC), we seem to be encountering many creatures with longbows. I was thinking about somehow getting the feather fall spell (multi-classing/magic item/other party member to take it) but wanted to know/confirm how it worked in specific situations.

1. Flying at 600 ft., get hit with arrows, as a reaction cast feather fall, then take enough damage to fall unconscious.

   Can I cast feather fall after I know the damage of the hits, or must I cast it once I know I've been hit? I assume that since the spell does not require concentration, it will last the duration (1 minute) and I can land after 10 rounds (descending 60 ft. per round) without taking any additional fall damage (albeit prone).

2. Flying at 60 ft. (feather fall spell range) over a friendly caster, get hit with arrows with enough damage to fall unconscious, friendly caster uses his reaction to cast feather fall on me.

   Will I reach the ground next turn prone but without additional fall damage?

3. Flying at 120 ft. (out of a friendly caster's 60-foot feather fall range), get hit with something and fall unconscious.

   When do I actually start to fall and how fast? On the turn I was hit by the enemy, or the start of my turn? What I'm wondering here is how much time there is (if any) for the cleric to cast a ranged healing spell before I hit the ground, or whether someone on the ground can cast feather fall on me once I fall within 60 ft. above them.

If possible in the answers please include citations.

Answer 1

So, first up, let's define exactly what triggers Feather Fall:

1 reaction, which you take when you or a creature within 60 feet of you falls

Situation 1: You can't cast Feather Fall as a reaction to being hit - it's a reaction to falling. If damage caused you to go unconscious, causing you to fall, then you can't use Feather Fall. That's because when you're unconscious, then you're incapacitated, which means you can't use reactions.

Situation 2: Yep, that's exactly how it works. If you land before the spell ends, you take no damage, and you can land on your feet. Taking no damage doesn't depend on landing on your feet, and while the spell gives you the option to land on your feet, while ever you're unconscious, you're prone.

Situation 3: Again, to establish a baseline, the rules on falling:

If a flying creature is knocked prone, has its speed reduced to 0, or is otherwise deprived of the ability to move, the creature falls, unless it has the ability to hover or it is being held aloft by magic, such as by the fly spell.

There's no suggestion of a delay there, so you start falling as soon as you're knocked unconscious. However, we really have no idea how long a fall lasts. You'll have to talk to your DM about that.

Finally, there's the question of whether someone can cast Feather Fall on you when you fall into their range. The reaction for Feather Fall can only be taken when a creature within 60 feet falls, but whether "falls" means "begins falling" or "is falling" isn't particularly clear. I think most people would allow casting Feather Fall on someone falling within 60 feet even if you weren't within 60 feet of them when they started falling, but you'll need to check that one with your DM too.

All that aside, you might be interested to know about the Ring of Feather Fall - it's a magic item that is pretty much designed for this sort of situation. If you can get your hands on one, you never need to worry about falling again.