How is the fuel system primarily classified in the MQ-9?

The fuel system in the MQ-9 is primarily classified as a closed system. In a closed fuel system, the fuel is contained within a network of lines and tanks that prevent outside contaminants from entering and minimize the risk of fuel loss or vaporization. This design is essential for maintaining the efficiency and reliability of the aircraft during its operations.

The closed system enables more precise control over fuel delivery to the engines, maintaining pressure and temperature within desired ranges, and optimizing performance. It also supports the aircraft's ability to operate in various environments without exposure to external factors that could affect fuel integrity.

In contrast, an open system would allow fuel to be exposed to the atmosphere, increasing the risk of contamination and loss. A hybrid system suggests a combination of both open and closed characteristics, which is not applicable in the context of the MQ-9's fuel management. A variable system implies adaptability or changeability in operation, but that does not accurately describe the MQ-9's fuel system's design and function. Therefore, describing the MQ-9’s fuel system as a closed system highlights its effectiveness and operational advantages.