the airplane's 'hydraulic' system
(..) JACKSON: That looks good. It's a bit more of a Bilbo-ish kind of eagle flight... - ...than a Harley-Davidson sort of ride. - Okay. Sure. It was great fun because it was on hydraulics. And Bifur, of course, being a little abnormal... ...decides to stand up on his eagle. NESBITT: Bifur! KIRCHER: (..)2012 The Hobbit: An Unexpected Journey