NP92A

Hydraulic pressure generation by the NP92A pump

The main function of the NP92A is to create hydraulic flow and pressure for helicopter control and service systems. The pump supplies aviation hydraulic fluid to the main, backup or auxiliary hydraulic circuits depending on helicopter type and system layout. It is not a simple transfer pump; it is a pressure-generating unit for onboard hydraulic consumers. Stable pump output is important for flight control assistance, actuator response and normal hydraulic system operation.

Automatic delivery regulation of the NP92A

The NP92A has a built-in delivery regulator. Pump delivery is adjusted automatically by changing plunger stroke through a movable sleeve mechanism. This allows the pump to maintain pressure within the required range instead of constantly delivering maximum flow. When system demand increases, the pump provides the necessary flow; when pressure reaches the regulated level, delivery is reduced. This helps reduce hydraulic heating, unnecessary load and pressure instability in the system.

Valve-slot distribution in the NP92A

The NP92A belongs to axial piston / plunger pumps with valve-slot distribution. This design is used in aviation hydraulic systems where a compact unit must provide stable pressure and reliable delivery. The pump works with AMG-10 aviation hydraulic oil and requires clean fluid, correct inlet conditions and proper hydraulic tank pressurization. Contamination, air in the suction line, poor tank pressure or blocked filters can lead to cavitation, noise, heating and accelerated wear of the plunger group.

Installation of NP92A on helicopter main gearboxes

The NP92A is installed on the drive gearbox of the helicopter main reducer, such as VR-24 or VR-252 type installations depending on helicopter model. This installation allows the pump to receive mechanical drive from the rotor transmission system rather than only from a separate engine accessory gearbox. As long as the rotor and main gearbox continue rotating, the pump can continue supplying hydraulic pressure according to system design. During installation, the drive interface, flange, shaft, sealing surfaces and hydraulic connections must be checked carefully.

NP92A-4 and NP92A-5 modifications

The most common NP92A modifications include NP92A-4 and NP92A-5. The NP92A-4 version is associated with Mi-family helicopters, including Mi-24 applications where pumps may be used in main, backup and auxiliary hydraulic systems. The NP92A-5 version is associated with Ka-family helicopters such as Ka-27, Ka-28, Ka-29 and Ka-32, including installations on the VR-252 main gearbox. These versions should not be treated as automatically interchangeable without checking the helicopter documentation, mounting arrangement and hydraulic system requirements.

Helicopter application of NP92A

The NP92A is used on domestic helicopter platforms, including Mi-24, Ka-27, Ka-28, Ka-29, Ka-32 and Mi-26 depending on configuration. On Mi-24 helicopters, three NP92A-4 pumps may be used in separate hydraulic circuits. On Ka-27 / Ka-32 family helicopters, NP92A-5 pumps are used in main and backup hydraulic systems. The actual pump version must be confirmed by the helicopter parts catalog, main gearbox documentation and hydraulic system layout before procurement or replacement.

Supply and inspection of NP92A

For procurement, the full modification should be specified: NP92A-4, NP92A-5 or another version if required. Before installation, the pump should be checked for housing condition, drive shaft and spline wear, flange surfaces, port threads, regulator condition, leakage traces, corrosion, storage condition and internal cleanliness. For aviation use, bench testing is recommended to confirm delivery, pressure regulation, leakage level and stable operation with AMG-10 hydraulic fluid. Passport, storage, repair or test documentation should be requested whenever available.