Andrew Johnson scored a hat-trick as Fulham demolished London rivals Queens Park Rangers for their first Premier League win of the season.The striker pounced after Paddy Kenny spilled a shot from Mousa Dembele after 78 seconds, won a penalty converted by Danny Murphy and struck from six yards.After the break he collected a Murphy free-kick before slotting home.Clint Dempsey scored after a flick from Bobby Zamora, who added the sixth with a crisp shot into the bottom corner.Fulham fans will hope the emphatic win, so soon after Johnson's Europa League brace against Odense, will kick-start a campaign which had previously failed to ingite, with four draws and two losses in their opening six Premier League fixtures.The first Premier League hat-trick by a Fulham player was taken in fine style, but it also exposed a slack defensive display which left QPR manager Neil Warnock fuming on the sidelines.