 The Bü 181 evolved very little during the war, the differences between the B type and the C types were minimal, the most important being the increased autonomy of the C types.The main difference between the B-1 & C-1 and the B-2 and C-2 sub-types was the presence of pitot heating and position & cabin lights while the B-2 and C-2 types lacked any electrical system.Bu 181V Prototype.