Here's the question, what exactly is known icing? Obviously if you look out the window and see ice, that's known icing. A pirep would also be "Known." What if the cloud layer starts at 4000 feet and you want to fly at 6000 with the freezing level at 5000? I've heard different answers to this, and heard the FAA won an enforcement case where the pilot got caught in ice and said that the pilot should have known there was icing becuase he planned to fly above the Freezing Level in clouds.