1. flow in tubing :the distance between the unit to be operated and the source of the hydraulic power the line throughout the aircraft
Resistance is created by the shearing action between the wall of the tube and the fluid. Resistance, There loss of energy. This resistance and how much power will remain to operated mechanisms the system
With no motion of the fluid, there is no resistance but as velocity increase for any given size of tubing and given velocity , the pressure is reduce the resistance depends on the velocity of the fluid