Hydraulic ground support for two aircraft at once.

Why the HST 300U matters

The Universal Hydraulic Servicing Trolley (HST 300U) is an advanced ground support system designed for servicing the hydraulic systems of military aircraft, fighter jets, transport planes, and helicopters. This hydraulic trolley provides a continuous, filtered, high-pressure hydraulic oil supply, ensuring the safe and efficient operation of aircraft hydraulic components during maintenance and testing. Engineered for versatility and reliability, the HST 300U is capable of servicing two independent aircraft systems simultaneously. It features a pressurized reservoir, precise pressure and flow control, vacuum-based de-aeration, and a fully integrated compressed air system, making it an essential tool for aircraft maintenance, repair, and overhaul (MRO) operations.

1. Main hydraulic system

The HST 300U delivers a continuous, high-pressure hydraulic oil supply to two independent aircraft systems. The flow rate is 100 litres per minute (LPM) per system, and the operating pressure is 300 bar. The system is compatible with OM-15, DTD-585, and MIL-H-5606 mineral-based hydraulic oils. The trolley is equipped with a precise flow and pressure control system, adjustable via a panel-mounted relief valve and an aircraft-specific selector switch. It also includes a vacuum pump system that removes trapped air and moisture from the hydraulic circuit, ensuring fluid purity and system longevity.

2. Static pressure (hand pump) system

The hand pump system enables manual filling of aircraft hydraulic reservoirs, generating up to 350 bar pressure per stroke. This ensures safe and controlled fluid transfer.

3. Engine-driven vacuum system

The vacuum system plays a crucial role in de-aerating the hydraulic circuit and maintaining fluid cleanliness. It operates at a vacuum level of 200 mBar (absolute), ensuring that moisture and air bubbles are effectively removed from the hydraulic system. A solenoid valve mechanism allows for automatic activation and venting.

4. Engine-driven compressed air system

The HST 300U includes an integrated compressed air system, capable of delivering air at a maximum pressure of 7 bar. The buffer chamber design ensures controlled air supply, making it suitable for pressurizing aircraft hydraulic reservoirs.

5. Hydraulic reservoir & filtration

The hydraulic system is equipped with a twin-chamber stainless steel (SS304L) reservoir, with a total capacity of 140 litres (70L + 70L). It features a 3-micron (μ) high-pressure filtration system, ensuring clean, contaminant-free hydraulic fluid. Additionally, the system allows for independent oil sampling, providing real-time monitoring of fluid conditions.

6. Power & mobility

The HST 300U is powered by a Greaves TBD3V6 diesel engine, ensuring reliable and continuous operation. It uses two 12V, 120Ah lead-acid batteries, providing sufficient power for all electrical components. For mobility, the trolley features an Ackerman steering mechanism, allowing smooth maneuvering. It is equipped with four wheels (two front and two rear), supported by a leaf spring suspension system for stability on rough terrain. The maximum towing speed is 10 km/h, making it easy to move within maintenance facilities.

7. Hose & connection system

The hydraulic servicing trolley is equipped with a comprehensive set of hoses:

• Two pressure hoses (1-1/4″) — 20 metres each
• Two return hoses (1-1/4″) — 20 metres each
• One additional pressure hose (1/4″) — 20 metres

A turbine-type digital flow meter provides real-time monitoring of hydraulic flow rates.

Applications of the HST 300U

The Universal Hydraulic Servicing Trolley (HST 300U) is an essential ground support tool for military, defense, and aviation sectors. It is widely used for:

• Military aircraft maintenance & testing: Actuating and testing hydraulic systems in fighter jets, transport aircraft, and helicopters; performing landing gear, brake system, and flap control tests; hydraulic fluid flushing and contamination removal.
• Fighter jets & military transport aircraft: Compatible with a wide range of military aircraft, including Sukhoi Su-30MKI, Mirage 2000, HAL Tejas, C-130J Super Hercules, Boeing C-17 Globemaster III, and Mi-17 helicopters.
• Aerospace manufacturing & MRO operations: Used for hydraulic system testing during aircraft assembly and maintenance; ensures fluid cleanliness and pressure accuracy in MRO facilities.
• Defense & air force bases: Field-deployable unit for emergency hydraulic servicing; used at remote air bases, aircraft carriers, and forward-operating bases.
• Commercial & civil aviation: Can be adapted for commercial aircraft hydraulic servicing; ideal for flight-readiness checks and pre-flight testing.

Why choose the HST 300U?

• Dual aircraft servicing — supports two aircraft simultaneously.
• Advanced filtration & de-aeration — ensures clean and moisture-free hydraulic fluid.
• Heavy-duty, reliable design — built for military-grade durability.
• Precise flow & pressure control — manually adjustable settings for aircraft-specific requirements.
• Field-deployable & mobile — easily towed and maneuvered across terrains.

Delivery and support

Neometrix backs the HST 300U as manufacturer and supplier with installation, commissioning, operator training, preventive maintenance, spares, and on-site service support — for customers across India and export markets in defence and aerospace.

Conclusion

The Hydraulic Servicing Trolley (HST 300U) sets a benchmark in ground hydraulic maintenance equipment. Its dual-aircraft capability, advanced filtration and de-aeration, heavy-duty construction, and field-deployable mobility make it an indispensable tool for defence, aerospace, and MRO operations that need dependable hydraulic ground support wherever the aircraft is parked.