Fan blades are combined into groups of six for thrust fans, or twelve for the lift fan. The thrust blades are long and narrow to throw back the air with as little drag as possible, whereas the lift fan blades are wider to build pressure and stop air escaping as the fan rotates. The fan blades can be replaced easily, even in the field so even if a branch were to get though the fan guard and break some of the blades we always carry spares. They can be adjusted to work best at different temperatures and altitudes by rotating them in sockets in the hub to different angles. And they can even be put in different configurations of two, three, four, six, eight or twelve blades if necessary.