How much fuel reserve is required on board a commercial helicopter operating under NIGHT VFR conditions?

The correct choice regarding fuel reserve requirements for a commercial helicopter operating under NIGHT VFR conditions is that there must be sufficient fuel for 30 minutes at normal cruise. This mandate is based on regulatory standards that ensure operational safety during night flying, where the risks associated with unexpected circumstances, such as changes in weather or navigational challenges, can be heightened.

When operating at night, visibility is reduced, and pilots may have limited options for safe landing areas. The 30-minute reserve serves as a buffer that allows for unanticipated diversions or delays, significantly enhancing safety. The helicopter must be capable of maintaining flight for this duration beyond its intended flight time to ensure that pilots have the necessary fuel to respond to emergencies effectively.

In contrast, the other options suggest fuel reserves that do not align with regulatory requirements for night operations, as they may not provide adequate safety margins in moments of necessity or unforeseen situations. Therefore, 30 minutes at normal cruise is the correct and safest requirement for fuel reserves during NIGHT VFR operations.