LEAP 1: Thrust. Igor Sikorsky wanted more lift, for more lift, he needed more power. not 2, but 4 engines. this seems obvious today, but at the time it was something nobody ever done. Early engines were unreliable, so if 2 failed on one side, the turning force would spin the aircraft out of control. Sikorsky realized that the further the engines, the worse the turning force if 2 of them failed. Sikorsky isn't sure this will stop it from spinning out of control, so he made one final alteration. he added a huge tail fin in the rear, and adds 2 extra blades. now, if 2 engines fail, the pilot can counteract the uneven thrust, and steer it back on track.