Hi, the manual linked in the main site (flying -> official manual) is plain broken.
The PDF reachable (slowly) from the wiki page is complete though. Will this be fixed? It's not a really great welcome. Personally, I had to use the 4 y.o. version of the manual to learn, which actually is not officially reachable. Not cool.
EDIT: for reference on the issue: https://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg40156.html
let me know if I should file it on the googlecode bugtracker