What type of refueling is allowed if the pilot valves are inoperative?

Gravity refueling is the correct type of refueling allowed when pilot valves are inoperative. In this scenario, gravity refueling takes advantage of the force of gravity to transfer fuel into the aircraft's tanks. This method does not rely on any powered systems or valves that would typically control the fuel flow, making it a viable option when the pilot valves are inoperative.

Pressure refueling, on the other hand, would require functioning pilot valves to ensure that fuel is pumped into the tanks at a pressurized rate. If these valves are inoperative, using pressure refueling could lead to improper fueling or even potential safety hazards. Gravity refueling, being a more straightforward process that does not depend on system integrity, provides a reliable alternative under these circumstances. Therefore, gravity refueling remains a safe and approved method of operation when faced with malfunctioning equipment related to fuel management systems.