The X-47B Unmanned Aircraft
Eaton Hydraulics Group Australasia is a key supplier to Northrop Grumman, the US Navy’s prime contractor for the Unmanned Combat Air System Carrier Demonstration (UCAS-D) program.
Northrop Grumman and the US Navy successfully conducted the first flight of the X-47B, the first carrier-capable unmanned aircraft developed for the Navy’s UCAS-D program.
As a key system supplier to Northrop Grumman, Eaton contributed the X-47B fuel system, engine-driven hydraulic pumps, reservoir, selector valves, hoses, Rynglok tube-fitting technology, swivels, flanges, couplings and straps.
During the initial aircraft development stages, Eaton worked closely with Northrop Grumman on the X-47B test rig or ‘iron bird’ located at Northrop Grumman’s Unmanned Systems Center in San Diego, California to validate test results and provide solutions to improve hydraulic system performance.
Eaton helped Northrop Grumman identify and resolve performance issues in the early stages of the project, which led to the project advancing from testing to production and to the first flight.
One of the challenges concerned the engine-driven hydraulic pumps supplied by Eaton for the X-47B. The Model PV3-115-45A pump had been qualified for 4,000 psi operation on the Lockheed-Martin F-22 fighter jet with an 8,000-hour design life.
Results from the X-47B test rig revealed high-pressure pulsations in an outlet line that were found to originate from an engine-driven pump. Pulsations are capable of producing adverse interactions within the hydraulic system that can cause problems with downstream components.
Eaton engineers entered X-47B test rig data into the Hydraulic System Frequency Resonance program, which Eaton had developed to simulate the response of a hydraulic system to pressure pulsations originating from typical in-line hydraulic pumps.
Anil Bhansali, lead engineer in Eaton’s hydraulic systems division explained that the high-fidelity check ensured the pump was correctly installed to support optimal hydraulic system performance. When problems are detected, the program provides the data needed to pinpoint the source and develop a solution.
Pressure pulsations can be controlled using commercially available devices that can be installed in the outlet circuit. An attenuator for instance, can modify overall system compliance with the addition of volume. An attenuator also has the capability to absorb peaks of flow pulsations and return flow to the main line during valleys or low points in outlet pressure.
Using hydraulic resonance analysis, Eaton helped Northrop Grumman size and place an attenuator to reduce pressure pulsations on the X-47B iron bird test rig. It was a critical step in the validation process that supported Northrop Grumman’s milestone schedule for the X-47B, including the aircraft’s first flight.
