title_body: Why do most drones have upward facing motors?
upvoted_answer: One practical advantage is increased ground clearance, reducing the likelihood of a prop strike on landing or take-off.
  
  Aerodynamically, a pusher1 design can be less efficient because the propeller is spinning through the wake of the fuselage - this results in 'lumpy' air, causing vibrations. I don't have exact figures, but I've heard anecdotally that this can be a 10 to 15% drop for fixed-wing designs and the exact fuselage configuration will make a difference!
  
  1: Pushers are often defined as '[motor/engine] shaft under compression'; which seems to apply to the 'upside down' motor configuration.