Are the military tilted-thrust aircraft in the film Avatar feasible?
I presume you're talking about the fictional Aerospatiale SA-2 Samson. From that page:


  Ducted fan VTOL aircraft have been flown since at least the 1960s. A notable example was the Bell X-22, a quad-ducted fan experimental aircraft built for the US military. It has no relation to the later V-22 Osprey tiltrotor. Though successful, no military aircraft since have used that technology. 


The Bell X-22 looked like this:



which has similar overall characteristics to the SA-2 depictions.