Radial Piston Pump for Use with HYJET® and SKYDROL®

The Moog Radial Piston Pump (RKP pump) has been widely accepted for decades throughout the world in various marketplaces. Due to its design principle, users of the radial piston pump have benefited from advantages such as long life and lower noise.

Enhanced RKP 

When Moog started redesigning the RKP pumps in 2002, the primary objective was to respond to industry demands such as: improving reliability, lowering the noise emission, and offering maximum flexibility to users in providing adaptability for configurations of the application. By taking advantage of state-of-the-art technology, a new control option has been created featuring digital electronics and a fieldbus interface, supported by an advanced control algorithm and Moog configuration software.

Various measures such as a new stroke ring design, enlarged suction port, and increased number of pistons have been implemented in the second generation of RKP to meet the objectives. Since the introduction of the re-designed RKP-II in 2005, the pump has proven in the field that significant improvements can be achieved while continuing to offer the same high performance.

Customised for Use with Phosphate Ester Hydraulic Fluids in the Aviation Industry

This was not the end of the product development activities. Far from it. Moog has utilized the versatility of the RKP design principle to its utmost. After internal analysis and testing of critical parts, Moog decided to extend its RKP-II line capabilities by offering an ATEX-certified version. The new enhanced version can be used in applications dealing with different types of fire-resistant aircraft hydraulic fluids such as Skydrol® to type V, LD4, 500B4, and HyJet®. These applied fluids have proven their ability to reduce aircraft fire hazards in the air and on the ground and offer lower viscosity compared to mineral oil based fluids. This characteristic allows a wide temperature range of operation, in particular at low temperature ranges.

Typical applications for this type of pumps are:

  • Aircraft testing and repair facilities
  • Airframe construction
  • Aircraft hydraulic component manufacturing facilities

Displacements ranging from 19 to 80 ccm are available. All pumps feature a flow limiter, which allows mechanical adjustment of the maximum displacement. They can perform at a continuous pressure up to 350 bar (5,000 psi), and offer 2 different control options: pressure compensator (type F) and load sensing (type J). They are also designed for open circuits. To improve the design flexibility of Moog’s RKP-II, the pumps are fitted with standard SAE-A and SAE-B flange arrangements, providing compatibility with third party pumps when operating in tandem.

A 12 month warranty is available. Furthermore our customers benefit from market-leading delivery times and worldwide technical support.

Displacement cm3/rev 19 32 80
Theoretical flow rate at 1,500 rpm 28.5 l/min
(7.5 US gal/min)
48.0 l/min
(12.6 US gal/min)
120.0 l/min
(31.5 US gal/min)
Theoretical flow rate at 1,800 rpm 34.2 l/min
(9.0 US gal/min)
57.6 l/min
(15.2 US gal/min)
144.0 l/min
(38.0 US gal/min)
Maximum speed 1,800 rpm
Type of mounting Spline according to DIN 5480, 4 holes ISO flange according to DIN/ISO 3019/2 (metric, type B7)
Mounting position Any
Type of drive Direct Drive with coupling
Continuous pressure 350 bar (5,000 psi)
Maximum pressure to DIN 24312 385 bar (5,500 psi)
Pressure peak 420 bar (6,000 psi)
Hydraulic fluids Skydrol® fluids up to Type V (Skydrol LD4, Skydrol 500B4, Skydrol 5)

HyJet IV-Aplus® and Exxon HyJet V®
Hydraulic fluid temperature range -15°C to +50°C (5°F to 122°F)
Ambient temperature range -15°C to +50°C (5°F to 122°F)
Viscosity Allowable operational range 8 to 100 mm²/s (cSt).
Recommended 16 to 46 mm²/s (cSt).
Maximum viscosity 500 mm²/s during start-up with electric motor at 1,800 rpm
Filtering NAS 1638, class 9, ISO/DIN4406, class 20/18/15
Line connections High pressure series 350 bar (5,000 psi) according to ISO6162
Pressure port SAE 3/4" 6,000 psi SAE 1" 6,000 psi SAE 1 1/4" 6,000 psi
Suction port SAE 3/4" 6,000 psi SAE 1 1/2" 3,000 psi SAE 2" 3,000 psi
This technical data is based on current available information and is subject to change at any time by Moog. Specifications for
specific systems or applications may vary.

Table 1 above shows a selection of technical data of the enhanced version of RKP.

Note: Skydrol® is a registered trademark of Solutia Inc.  HyJet® is a registered trademark of Exxon.



Robert Luong, holder of Bachelor's and Master's degrees in electrical engineering, as well as a MBA, Robert is a Product Marketing