NP-128

Hydraulic power generation by the NP-128 pump

The main task of the NP-128 is to generate hydraulic pressure and deliver working fluid to aircraft hydraulic consumers. Pump delivery depends on shaft speed and working displacement. Since the pump is adjustable, its output is not fixed in the same way as a simple constant-displacement unit. The pump can change delivery automatically to maintain pressure in the hydraulic system. This allows the aircraft to receive high-pressure hydraulic power when demand increases and to reduce unnecessary delivery when the system is already at pressure.

Automatic regulation in the NP-128

The NP-128 is equipped with an internal automatic control unit that changes the pump displacement according to hydraulic system pressure. The regulator reacts to pressure changes and mechanically adjusts the swash plate or cradle angle, which changes plunger stroke and therefore flow rate. This design allows the pump to support stable pressure without constant external adjustment. If pressure control becomes unstable, the cause may be inside the pump regulator, but also in the hydraulic system, unloading valves, leakage, accumulator condition, suction line or working-fluid contamination.

Mechanical drive and installation of the NP-128

The NP-128 is mechanically driven through a splined shaft and mounted to an aircraft accessory gearbox, central gearbox or remote drive gearbox depending on aircraft configuration. The pump is fixed by flange connection, while rigid high-pressure hydraulic pipes are connected to suction, pressure and drain ports. Correct installation is important because poor alignment, damaged splines, incorrect sealing or restricted suction can quickly affect pump performance. Before installation, the drive shaft, flange, port threads, drain line and regulator housing should be checked carefully.

NP-128 as a main onboard hydraulic source

In aircraft hydraulic systems, the NP-128 can serve as a main source of hydraulic energy for flight-control and utility systems. It supplies pressure to hydraulic accumulators, flight control boosters, landing gear actuators, wheel braking systems, nose gear steering, flap and slat drives, airbrake mechanisms and other consumers depending on aircraft layout. In this role, pump reliability directly affects the operation of multiple aircraft systems. A pressure problem should therefore be diagnosed across the full hydraulic circuit, not only at the pump.

Working fluid and hydraulic cleanliness for NP-128

The NP-128 operates with aviation hydraulic fluid specified by the aircraft or test stand documentation. In some applications, IPM-10 type fluid or equivalent aviation hydraulic fluids may be used, depending on the system. Fluid cleanliness, viscosity and temperature are critical for a high-pressure axial plunger pump. Contaminated fluid, air in the suction line, low inlet pressure, clogged filters or incorrect fluid grade can cause noise, overheating, unstable pressure and accelerated wear of the plunger group and regulator.

Aircraft and test stand application of NP-128

The NP-128 is used in aircraft hydraulic systems and specialized ground hydraulic test stands. It is associated with military aircraft hydraulic systems, including installations in the main hydraulic system of Su-34 type aircraft depending on configuration. On aircraft, the pump is installed on gearbox-driven accessory systems and supplies high-pressure hydraulic consumers. In ground use, it may be installed on hydraulic benches for testing aviation hydraulic equipment under controlled pressure and flow conditions. Exact applicability must be confirmed by the aircraft or stand documentation.

Supply and inspection of NP-128

For procurement or replacement, the full designation NP-128 should be used. The pump may be supplied new, from storage, repaired, overhauled or tested serviceable depending on availability. Before installation, the unit should be checked for shaft condition, spline wear, flange face, housing damage, regulator condition, port threads, drainage connection, leakage traces and preservation state. For aircraft use, bench testing is strongly recommended. The pump should confirm delivery, pressure regulation, zero-delivery behavior, leakage level and stable operation with the specified working fluid.