Hydraulic Servicing Trolley (HST 120U), dual-aircraft power in a 2.3m frame.

Why the HST 120U matters

The Hydraulic Servicing Trolley (HST 120U) is suitable for a wide range of fighter aircraft, military transport aircraft, and helicopters used in the Indian Air Force. It is specially designed and developed for the ground servicing of two independent aircraft hydraulic systems, and is used for actuation of the aircraft hydraulic system through supplied pressurized hydraulic oil from the trolley to the aircraft — comprising a pressurized reservoir, with filtered and de-aerated fluid at the flow and pressure characteristics required for testing. The trolley consists of four sub-systems: the mechanical structure and its steering system, the prime mover and its accessories, a twin hydraulic system, and a vacuum system for de-hydration and de-gassing.

1. Twin hydraulic system

The HST 120U continuously supplies filtered, high-pressure hydraulic oil to two independent aircraft systems through two sets of delivery and return lines (System-I and System-II). Flow rate is 100 litres per minute (LPM) in each system, at an operating pressure of 300 bar, with supply pressure exceeding 3,500 psi and a high-pressure outlet on a 3/8″ BSP hose connection. The system is compatible with mineral-base hydraulic oil OM-15, DTD-585, and Superclean MIL-H-5606. Delivery pressure and flow can be steplessly controlled from the panel, and the trolley can regulate the hydraulic fluid level in each aircraft system — decreasing or increasing the level of the aircraft reservoir by a quantitative volume of oil.

2. Vacuum system (de-hydration & de-gassing)

An engine-driven vacuum system provides de-gassing of the hydraulic circuit, removing trapped air and moisture from the fluid to maintain system cleanliness and reliability across both aircraft systems being serviced.

3. Fluid temperature control

The HST 120U includes a hydraulic fluid high-temperature phenomenon control device and is rated to operate across a temperature range of −5°C to 50°C, protecting oil quality and system components in variable field conditions.

4. Mechanical structure, prime mover & mobility

The trolley runs on four wheels (two front, two rear) with leaf-spring suspension front and rear and an Ackerman steering mechanism, towable at up to 10 km/h. Its 140-litre fuel tank supports the onboard prime mover through extended servicing operations, and the complete unit has a rear axle weight (RAW) of 1100 kg in an overall footprint of 2300 mm (L) × 1100 mm (W) × 1200 mm (H) — the most compact trolley in the Neometrix HST range.

5. Instrumentation & isolation

The panel instruments delivery pressure, boost pressure, return pressure, delivery flow, and temperature for both aircraft systems in real time. The trolley tank can be completely isolated while the aircraft tank is used in the circuit, and including both tanks in the circuit together is also possible — giving maintenance crews flexibility during flushing, charging, and topping operations.

Applications of the HST 120U

The Hydraulic Servicing Trolley (HST 120U) is an essential ground support tool for defence and aviation sectors. It is widely used for:

• Military aircraft maintenance & testing: Ground servicing of two independent aircraft hydraulic systems, actuating and testing hydraulic systems in fighter jets, transport aircraft, and helicopters.
• Fighter jets & military transport aircraft: Compatible with a wide range of military aircraft, including Sukhoi Su-30MKI, MiG-29, MiG-21, Mirage 2000, and HAL Tejas.
• Defence & air force bases: Compact, towable design suited to space-constrained hangars and dispersed forward-operating bases where a smaller ground footprint matters.
• Fluid quality management: Continuous filtration, vacuum de-gassing, and high-temperature phenomenon control keep supply oil clean across extended servicing operations.

Why choose the HST 120U?

• Dual aircraft servicing — supports two aircraft simultaneously at full 300 bar / 100 LPM per system.
• Most compact HST trolley — smallest footprint and lightest rear axle weight in the Neometrix HST range.
• Advanced filtration & de-gassing — ensures clean and moisture-free hydraulic fluid.
• Precise flow & pressure control — steplessly adjustable settings from the panel for aircraft-specific requirements.
• Field-deployable & mobile — Ackerman-steered, leaf-spring suspended chassis towable at up to 10 km/h.

Delivery and support

Neometrix backs the HST 120U 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 120U) packs the same dual-aircraft, 300 bar hydraulic servicing capability as the larger Neometrix HST trolleys into the smallest footprint in the range. Its filtration, de-gassing, and thermal control systems, combined with a towable, compact chassis, make it an efficient ground-support choice wherever apron space or hangar footprint is at a premium.