Sudden penetration of fog can create the illusion of:

The sudden penetration of fog can create the illusion of pitching up due to the distorted visual references that fog presents to the pilot. When flying through thick fog, the lack of discernible ground features and horizon makes it difficult for the pilot to maintain an accurate perception of the aircraft's orientation.

In this situation, the pilot might misinterpret the aircraft's actual flight path. The absence of visual cues can lead pilots to feel as though they are climbing or pitching up when, in fact, they may be in a different attitude entirely. This illusion can result from the body’s reliance on visual stimuli to maintain spatial orientation, which is compromised in foggy conditions.

Being aware of these illusions, including the potential perception of pitching up, is vital for pilots to maintain control of the aircraft and prevent unintended maneuvers. Understanding these visual illusions can help enhance situational awareness and improve safety in low-visibility conditions.