Hydraulic 

Systems

Four Star's hydraulic pump repair services cover piston, gear, and vane pumps, both engine-driven or electric, ensuring proper pressure generation, flow delivery, and relief valve function through calibrated test-stand verification.

Four Star supports landing gear hydraulics with repair and testing of uplocks, downlocks, sequence valves, and brake system components. Each is inspected for contamination, thermal wear, and structural integrity to ensure reliability in every cycle and safe operation on landing.

Our strut repair and overhaul capabilities include complete disassembly and inspection, cylinder honing or chrome restoration, seal and bearing replacement, and pressure and functional testing under simulated aircraft loads. We service oleo struts with precision, ensuring proper extension, compression, and gas charge for dependable performance.

Strut issues such as gas leakage, hydraulic fluid loss, or worn components can impact aircraft handling and height control. Our diagnostics identify root causes and implement repairs that restore reliability and compliance with OEM standards.

All hydraulic components undergo leak, efficiency, and functional testing before release to service, with full traceability and recorded test data included in permanent documentation.

As an FAA-certified hydraulic repair station, Four Star operates under approved OEM and FAA repair procedures that guarantee compliance, safety, and consistency. Every repair includes airworthiness certification, test results, and parts traceability to satisfy all regulatory and logbook requirements.

Four Star verifies internal cleanliness through inspection and particle analysis of test fluids. We will confirm compliance with manufacturer and industry specifications. Our team also manages fluid compatibility across petroleum-based MIL-H-5606, synthetic Skydrol, and phosphate ester systems — segregating work by fluid type to prevent cross-contamination and ensure proper seal, solvent, and lubricant selection for each aircraft application.

Hydraulic issues often stem from larger challenges such as contaminated fluid, thermal degradation, or electrical faults in motor-driven pumps. Our technicians analyze system interactions across hydraulic, pneumatic, electromechanical, and power generation systems to identify patterns, prevent repeat failures, and improve overall reliability.

With experience across systems operating from 1,500 to 5,000 PSI, we bring the technical depth and system-level insight needed to maintain performance and consistency across all aircraft platforms.