Error to BodyAngularVelocity, "angularvelocity cannot be assigned to"?

the following is a segment from a LocalScript in the Player.

local seat = Workspace:FindFirstChild(game.Players.LocalPlayer.Name.."StarShip").Seat
local Rotate = seat.BodyAngularVelocity
Rotate.angularvelocity = Rotate.angularvelocity  + Vector3.new(0,0,1)

when run, the Output prints the Error "angularvelocity cannot be assigned to". I have checked the ROBLOX wiki for an answer, but have not found one. So what have I done wrong here? is this a problem with my script or ROBLOX? All answers appreicated, thank you very much. ~Xduel