I merged your thread with Izaw's thread on Falco's Dair cancel. First thing of note: please try to search for whatever your topic is with the search bar and try asking here in the general discussion and Q&A thread:
http://smashboards.com/threads/falco-king-of-the-birds-game-play-discussion.367184/, instead of making a thread specifically to ask for something. If there is completely no information about something, so a new, but perhaps undocumented discovery, then sure, make a thread, but for questions, please try and search for a topic related to it and if there isn't one, then ask in the general discussion and Q&A thread.
Second thing of note: Falco's Dair has 23 landing frames not 11. The closest Falco's Dair had to 11 landing frames was in Brawl where it was 12 and in Melee where L-canceled Dair had 9. I can't explain the timing, but a more in-depth study on it is here on Smashboards:
http://smashboards.com/threads/frame-syncing.434603/, to help you understand how it works. The researchers decided to call it frame syncing instead of frame canceling since you're not canceling anything... The Smash community has a weird fixation on calling a lot of stuff cancels when they're not like jab cancels... You're not actually canceling anything; you're just not going into the next part of a jab. If there was a cancel, the recovery would not exist and you would be able to immediately move into another move like in Brawl where Falco could cancel dash attack into Up Smash or in Smash 4 where Ryu could cancel jab, light Utilt, and light Dtilt into any of his Specials. Anyway, I digress. I'd like to summarize it, but I feel lazy.