1. One of the functions of a hydraulic accumulator is..to asborb power surges from the pump, also in some systems to provide emergency actuation in the event of pressure loss eg. brakes
Both answers are correct but the primary purpose of the accumulator is to “try to maintain system pressure” when the pilot places a load on the system during flight control movement. An accumulator is used primarily in a system that does not have a compensated pump. This type of pump is normally referred to as a variable delivery constant pressure pump. This is a misnomer because even a variable delivery constant pressure pump can’t maintain full pressure in the system when the servos require a high flow rate. As the demand is placed on the system the pump will only maintain the pressure at a level to accomplish the work of the servos.
In other words if your system pressure is rated at 3000 PSIG and it only takes 2000 PSIG to overcome the feedback control loads then the pump will only put out 2000 PSIG that is until the servo movement stops and then the pressure will rise to 3000 PSIG. The accumulator on the other hand tries to keep the pressure at a level sufficient to overcome the loads on the system until the pump catches up and repressurizes the accumulator. Some helicopter servos have a built-in accumulator to allow some control movement in the event of pressure loss.
