Which of the following is a primary function of the flip-flop valve?

The primary function of the flip-flop valve is to maintain fuel flow during negative-G maneuvers. In aviation, fuel systems need to ensure that fuel remains available to the engines even when the aircraft experiences changes in orientation, such as during steep climbs or descents. The flip-flop valve achieves this by allowing fuel to flow effectively to the engines when the aircraft is in a position that would otherwise cause fuel to slosh away from the fuel pickup points. This is crucial for maintaining engine performance and preventing fuel starvation during maneuvers that may lead to temporary disruptions in fuel supply.

Regulating engine temperature pertains to cooling systems, while controlling fuel pressure is more associated with fuel pumps and regulators. Cooling the fuel system relates to ensuring that the fuel remains at optimal temperatures, which is also not the primary role of the flip-flop valve. Thus, the function of maintaining fuel flow during negative-G situations is a critical aspect of ensuring reliable engine operation in challenging flight conditions.