Details

1. Functional Overview
The Advanced Test & Calibration Bench for Integrated Fuel Pump and Controller in Aircraft Engines is a complex, multi-domain test facility designed to replicate the hydraulic, pneumatic, and electrical conditions experienced by the fuel pump and controller in an operational aircraft environment.
The integrated fuel pump and controller is a critical engine accessory, responsible for delivering fuel at precisely regulated pressures and flow rates while simultaneously adjusting compressor inlet guide vane (IGV) positions in response to engine speed, inlet air temperature, compressor discharge pressure, and throttle commands.
The bench enables preliminary regulation of these units before installation, allowing engineers to calibrate, verify, and document performance under controlled laboratory conditions. This ensures that each unit conforms to operational tolerances and is free from faults that could lead to in-service failures. In addition to live operational simulation, the bench incorporates a preservation system that circulates heated protective oil through the unit after testing, extending component life and preventing corrosion during storage or transportation.

2. System Layout and Zoning
The facility is divided into three physically separated zones to ensure operator safety, efficient workflow, and reduced interference between systems. The Control/Command Room houses the main operator panel, PLC/HMI interface, and all instrumentation readouts, keeping the operator isolated from noise, vibration, and potential hazards in the test area. The Test Cell contains the hydraulic, pneumatic, and preservation subsystems, arranged for maximum accessibility during setup and maintenance. The Motor Isolation Room contains the drive motor and gearbox assembly in an acoustically dampened enclosure, preventing high-frequency vibration and noise from coupling into the fuel system or the test environment.

The zoning also supports a “safety-first” workflow, ensuring that any flammable or pressurised media remain within controlled areas, while electrical and control systems are housed in flameproof enclosures and kept at a safe distance from ATF handling equipment.

3. Hydraulic (Fuel) Circuit
The hydraulic system forms the backbone of the test bench, responsible for storing, filtering, conditioning, and delivering Aviation Turbine Fuel (ATF) to the integrated fuel pump and controller at precisely regulated pressures and temperatures. The system features a 100-litre stainless steel (SS-300 series) service tank with a 3 mm wall thickness to withstand both pressure surges and mechanical handling. The tank is fitted with a low-level sensor linked to an interlock, which automatically shuts down the pumps to prevent cavitation damage. A removable lid provides access for internal cleaning and inspection, ensuring long-term fuel cleanliness.

Fuel delivery is achieved through two separate gear pumps. The high-pressure gear pump is rated at 50 LPM at 50 kgf/cm2, driven by a flameproof electric motor with foot-cum-flange mounting for secure alignment. This pump supplies the primary test lines, which are regulated by high-precision constant pressure valves set to 22 ± 0.2 kgf/cm2 and 11 ± 0.2 kgf/cm2. The second gear pump operates at 50 LPM at 10 kgf/cm2 and serves the circulation and filtration loop, allowing the fuel to be cleaned and conditioned independently of the main delivery system.

Multi-stage filtration ensures removal of particulate contamination down to 3 microns absolute. The filtration stages consist of a 16 μm pre-filter, a 6 μm intermediate filter, and a final 3 μm filter, each with a beta ratio greater than 1000 to guarantee high retention efficiency. Each filter housing is equipped with a differential pressure gauge to indicate clogging and is protected by a bypass valve calibrated to 3.5 bar, ensuring uninterrupted flow in the event of blockage.

Before entering the test unit, the fuel passes through an air separator, which removes entrained gas bubbles that could affect pressure regulation or cause cavitation damage to the unit. A dome-regulated drain valve maintains a constant back pressure of 2 ± 0.2 kgf/cm2 in the return line, accurately simulating the resistance of an engine fuel drain system. Fuel temperature is controlled by a plate-type heat exchanger capable of handling 50 LPM of ATF on the hot side, with chilled water at 6 kgf/cm2 on the cold side, ensuring a stable working fluid temperature within the 15–40 °C operational range.

4. Pneumatic Simulation Network
The pneumatic system provides both low-pressure and high-pressure air services to simulate engine bleed air functions and to dry the unit after fuel testing.

The low-pressure circuit is designed for post-test drying. Compressed air enters through a moisture separator and is drained periodically via a manual valve to remove condensed water. The air then passes through a fine particulate filter before being routed to the unit through a flexible hose, ensuring that all residual fuel is removed from internal passages.

The high-pressure circuit simulates bleed air supplied to temperature-sensing elements such as the TDK-Tp sensor within the unit. A high-precision regulator controls air pressure, followed by a fine filter to prevent particulate contamination. Downstream, a throttle valve allows the operator to vent air to the atmosphere in a controlled manner, simulating transient bleed events. Pressure is monitored both via an analog gauge for immediate operator reference and a high-accuracy transducer linked to the control panel for data logging.

5. Electrical Drive and Control System
The mechanical drive system consists of a high-speed electric motor coupled to a gearbox with a 1:4.32 gear ratio, enabling the unit to be driven at speeds up to 6200 RPM while maintaining high torque at low speeds. Speed control is achieved using a closed-loop vector-controlled Variable Frequency Drive (VFD) with encoder feedback, providing speed resolution to within ±1 RPM. The motor and gearbox are mounted on vibration isolators within the Motor Isolation Room, reducing transmission of mechanical noise to the test cell.

The control panel in the Command Room is equipped with multiple Digital Read-Outs (DROs) displaying real-time data including supply and drain pressures, pneumatic pressures, ATF and preservation oil temperatures, electrical consumption (current and voltage), and both motor and gearbox output shaft speeds. Operators control the test sequence using rotary knobs for speed and setpoint adjustments, an Auto/Manual selector switch, and dedicated push-buttons for starting and stopping pumps, actuating valves, and initiating preservation cycles.

The system includes a pulse duty cycle generator for actuating electro-mechanical valves on the unit under test. This generator outputs 27 VDC at 40 Hz with a default 50% duty cycle, adjustable via the front panel to simulate various ECU control signals. Safety is ensured through flameproof enclosures for all electrical devices, an emergency stop circuit, overpressure relief valves in both hydraulic and pneumatic lines, and a low-level fuel cut-off interlock.

6. Preservation and Conditioning Circuit
After functional testing is complete, the Preservation and Conditioning Circuit circulates heated protective oil through the internal fuel passages of the unit to prevent corrosion, oxidation, and residue build-up. The system includes a 100-litre stainless steel preservation oil tank with a low-level sensor, a dedicated flameproof gear pump, and multi-stage filtration identical to the main fuel system.

The oil is heated to 70 °C ± 2 °C to ensure optimal coating and penetration into fine clearances. The bypass valve prevents overpressure in the event of downstream blockage, while a relief valve ensures operator safety by diverting excess oil back to the tank. This circuit can operate in either static soak mode, where the oil remains in the unit for a set period, or dynamic circulation mode, where continuous flow is maintained for extended preservation.

7. Engineering Design Considerations
The bench is constructed using seamless stainless steel piping (SS-300 series) with high-integrity fittings from approved aerospace-grade suppliers such as Swagelok or Parker, employing 37° or 74° flare seals. No PTFE tape is used on threaded joints to prevent particle shedding into the fluid systems. Pressure-sensing ports are located no more than 150 mm from the connection to the unit under test, minimising signal lag and ensuring accurate readings.

All major components, including pumps, filters, and regulators, are mounted on rigid, vibration-dampened frames to maintain alignment and reduce fatigue on pipework. The layout is designed for ease of maintenance, with filter housings, pressure valves, and key instrumentation accessible from the front of the rig without the need to dismantle major assemblies.

8. Technical Specifications Table

    

        
Parameter
        
Specification
    
    

        
Working Fuel
        
Aviation Turbine Fuel (ATF)
    
    

        
Preservation Fluid
        
Mineral-based preservation oil
    
    

        
Fuel Tank Capacity
        
100 L (SS-300 series, 3 mm wall)
    
    

        
Preservation Oil Tank Capacity
        
100 L (SS-300 series, 3 mm wall)
    
    

        
High-Pressure Supply
        
22 ± 0.2 kgf/cm²
    
    

        
Low-Pressure Supply
        
11 ± 0.2 kgf/cm²
    
    

        
Drain Back Pressure
        
2 ± 0.2 kgf/cm²
    
    

        
Max Flow Rate
        
50 LPM
    
    

        
Filtration Stages
        
16 μm → 6 μm → 3 μm, β > 1000
    
    

        
Filter Bypass Pressure
        
3.5 bar
    
    

        
Heat Exchanger
        
Plate type, 50 LPM, chilled water 6 kgf/cm²
    
    

        
Air Simulation Pressure
        
Regulated, high and low circuits
    
    

        
Drive System
        
Electric motor with 1:4.32 gearbox
    
    

        
Motor Speed Range
        
500–6200 RPM
    
    

        
Speed Accuracy
        
± 1 RPM (encoder feedback)
    
    

        
Electrical Supply
        
415 VAC ± 10%, 50 Hz, 3-phase
    
    

        
Control Interface
        
PLC/HMI with manual override
    
    

        
Pulse Duty Generator Output
        
27 VDC, 40 Hz, adjustable duty
    
    

        
Oil Preservation Temperature
        
70 °C ± 2 °C
    
    

        
Safety Features
        
Flameproof design, E-stop, overpressure relief, low-level shutdown
    
    

        
Piping
        
Seamless SS-300, aerospace-grade fittings
    
    

        
Maintenance Access
        
Front-access filters, valves, instrumentation