Which statement is false concerning "shallow fog" during an approach?

The statement that is false concerning "shallow fog" during an approach is that instrument flight references should be kept in your crosscheck until landing. In conditions of shallow fog, pilots typically reduce visibility, making it crucial to maintain attention on instrument flight references until the visual references for landing, such as the runway environment, are clearly visible.

To safely transition from instrument references to visual references, the pilot must ensure the runway environment is established and in sight. Before committing to visual references, relying solely on instrument aids is essential for maintaining control of the aircraft in reduced visibility conditions.

The other statements highlight important aspects of flying in shallow fog. The requirement that the runway environment must be in sight before dropping instrument references emphasizes the need for visual confirmation before transitioning to visual flight rules (VFR). Additionally, fog can indeed obscure the runway, which is a critical factor in assessing visibility conditions during an approach. Recognizing that shallow fog can reduce visibility yet still pose a challenge while approaching helps pilots prepare for potential visual obstructions.