When is the 5th light required for the Inverted Y marking?

For the Inverted Y marking, the requirement for a fifth light is emphasized primarily for all cargo aircraft. The Inverted Y marking is used to indicate suitable landing zones for helicopters, and the addition of the fifth light enhances visibility and identification, which is crucial for safety during operations, especially when larger cargo aircraft are involved.

Cargo aircraft typically require more precise landing guidance due to their size and operational needs. The fifth light serves as a critical visual cue that delineates the landing area more clearly, thereby reducing ambiguity during approach and landing. This increased visibility is particularly important in conditions where enhanced discernment of the LZ may be needed, such as dusk or challenging weather conditions.

While the other scenarios may seem relevant, they do not have the same broad applicability across all cargo aircraft operations as the requirement for the fifth light does.