Not all aircraft have the full suite of instruments necessary to fly in instrument flight rules. When these aircraft go into the goo, the pilot doesn't have an

Not all aircraft have the full suite of instruments necessary to fly in instrument flight rules. When these aircraft go into the goo, the pilot doesn't have anything other than his/her senses to guide them. But senses are unreliable. What feels like "standing still" is actually just a 1G acceleration in any inertial frame of reference. Which means you could end up in the proverbial "graveyard spiral." And if the cloud ceiling underneath you is low enough, by the time you realize this, you may not have enough time or maneuverability to recover. Also, in some areas of the country, clouds have been known to conceal large mountains and cliff faces, which are uniformly fatal to airplanes.