Ok I'd better give some background. When designing a fuel pump for military helicopter applications, you have to take into account that there is no boost pump at the fuel tank, as this would leave a pressurised line running up the side of the cockpit which could be a big fire hazard if subjected to battle damage. To combat this, the line needs to be under suction so fuel will not spray out. This is done by having the displacement side of the pump self prime, that is, pumping the air through and drawing the fuel into the pump from the fuel tank at the bottom of the helicopter. The pumps ability to do this is called its dry lift performance.