The US EPA (Environmental Protection Agency) defines Refuelers as bulk storage containers installed onboard a vehicle (truck) solely to store and transport fuel into or from an aircraft. In addition to refueler trucks, mobile automobiles, locomotives, or ground service equipment can also act as refuelers when equipped with an oil storage container and a towing mechanism for mobility.
Often aviation fuel arrives at the airport through the pipeline and is then pumped into aircraft using a refueler truck. Few airports have integrated pumping systems where aircraft taxi for fueling. Depending on the aircraft type, aviation fuel is transferred using either overwing or underwing fueling. Overwing fueling is used on smaller planes, and the fueling operation is performed with a conventional pump. Underwing fueling or single point or pressure refueling is performed for large aircraft, and the procedure is not dependent on gravity. As the name Pressure refueling suggests, it is often carried with centrifugal pumps mounted on refueler trucks, which are connected to the aircraft using high pressure (40-45 PSI) hoses.
Refueler Trucks – Types and Selection Criteria:
Jet and Aviation gas refueler trucks are chosen depending on the application and capacity. Although modern trucks are equipped with distinct features such as lift decks, backup cameras, and electronic printers, broadly refueler trucks are classified based on their:
- Tank/storage capacity and aircraft fuel requirements: Refuellers up to 7,000 gallons or 10,000 gallons can be selected for larger aircraft applications. Operators can choose between 1,000 gallons, 1,500 gallons, 3,000 gallons, or 5,000-gallon storage capacities for small and medium-sized aircraft.
- Bottom load – Pumping/Discharge flow rates: All refueler trucks are equipped with either centrifugal pump (often) or positive displacement pump (rare configuration), with adjustable bottom load discharge control valves. Typically trucks are fitted with a transfer rate of 300 GPM
- Fueling module configurations: Trucks can be configured as Mid-reel or Rear fueling to match application preferences and needs. Mid-reel provides better visibility and control to the operator during a refueling operation, while the truck’s turning radius is reduced due to rear axle weight transfer. A better turning radius can be achieved with the rear fueling configuration, but additional cameras should be set up for operators’ view from within the truck cabin.
Refueler Trucks – Operation Procedure:
The following is the standard procedure laid out by the Dukes Titan Aviation and the AV Fuel system, which are accepted as an international standard for aircraft refueling operations:
Note 1: Underwing refueling operation using refueler trucks is discussed in the following section. The overwing process is relatively more straightforward and carried out by gravity flow or pumping.
Stage 1: Fuel Transfer between Fuel Storage systems and Refueler Truck
- Move the interlock gate open and attach the trucks’ hose
- Note the difference between jet-fuel and avgas couplers, open the shutoff valve behind the bottom-loading adapter, and position the loading nozzle handle to “open” to allow fuel to flow into the refueler truck piping.
- Engage the deadman and start filling the refueler truck. The bottom loading gauge will indicate pressure when fuel is flowing into the truck.
- Check that the high-level shutoff is operating correctly by closing the pre-check valve. This will stop fuel flow into the tank.
- Once the fuel transfer is complete, close the pre-check valve and shutoff valve behind the bottom-loading adapter.
- Disconnect the loading hose and close the interlock gate. Disconnect and rewind the bonding cables.
- Remove the chocks, apply the service brakes, and release the parking brake
Stage 2: Underwing Fuel transfer between Refueler Truck and Aircraft
- Position the refueling truck and chock the wheels. Place the ladder under the area where the aircraft fuel tank opening is located if required.
- Record the register totalizer and Zero the meter’s register.
- Open the reel inlet to the underwing hose and unwind enough to reach the aircraft fueling adapter. Remove dust covers and connect the nozzle to the aircraft fueling adapter and open the nozzle. Remove the deadman handle from its receptacle and pull it out.
- Squeeze and hold the deadman handle to start the flow of fuel. Differential pressure readings can be checked to ensure fueling and to make sure the filter system is working.
- Once the fueling operation is complete, release the deadman to stop the fuel flow and rewind the hose and stow the deadman handle in its receptacle.
- Close the product belly valve and nozzle. Disconnect the nozzle from the aircraft fueling adapter and replace any dustcovers removed from the aircraft or nozzle.
- Secure any service panels on the aircraft used to access the single-point receptacle.
- Disconnect and rewind the static cables and record the registered gallons
Preventative Maintenance Program for Refueler Trucks:
The US Department of the Air Force has laid out the following preventive maintenance program followed on Refueler Trucks for safe operation:
- PM guidelines for Refueler Truck Air System:
- Air tank: Air tank should be drained daily by pulling the drain release cable.
- Alcohol evaporator: Evaporators should be changed every month (winter) and bi-monthly (other seasons)
- Filter and water trap: This filter section holds the water and has to be drained monthly using the drain valve
- Lubricating oil: The level of lubricant should be checked bi-monthly and refilled if quantity is not as per acceptable standard
- PM guidelines for Truck Fueling system:
- Oil filter: Filter should be replaced yearly, or when differentia pressure reading exceeds 15 PSI
- Fueling components and accessories: Piping bolts, hose flanges, and bolts should be inspected daily for leaks and necessary steps for arresting leaks
- PM guidelines for Drain system:
- The inlet and outlet filter drain systems should be tested for higher differential pressures
- Nozzle screening should be conducted weekly to avoid damage or nozzle clogs
- PM of Refueling Pumps
- Pump fluid or oil should be changed for the first 100 running hours or within four weeks of the first operation. After the first oil change, top-up or change oil at every 500 running hours.
- Care should be taken while selecting the suitable Fluid grade, as per OEM guidelines.
- PM guidelines for Hydraulic System
- Hydraulic fluid levels should be checked every day during the summer months and every alternate day during the other months. Similar to Pump fluid, hydraulic oil should be changed at first 100 running hours, post which at every 250 hours.
- Reeling – The discharge velocity control module can be greased as required
- PM of Electrical systems and equipment
- Control and PLC box: Check for corrosion, sparking, or loose ends
- Batteries: If batteries need to charge, a low Amp charger can be connected to the battery and follow the standard OEM procedure
- Harness: The cable system should be intact and adequately insulated
- Fuel system icing inhibitor (FSII) Inspection and PM:
- FSII, commonly noted with brand names Prist, FIZZY, or Dice, are required in aircraft that do not have heaters in their main fuel filter systems and are susceptible to reduced fuel flow if ice crystals form, resulting in reduced fuel flow could possibly starve the engine of fuel.
- Calibration of FSII: Inspect the condition monthly, and if required, perform calibration
- Inspection of Prime pump and bypass lines for leakages
- Meters Calibration and PM:
- Aviation refueling tanks are equipped with meters (mechanical, electronic, or digital) to calculate the amount of fuel flowing through a house and produce a numerical account. The accuracy and sensitivity of these meters are critical to determining the fuel transfer and the cost accounted for refueling operation.
- Seals should be inspected monthly and Meters Calibration at annual intervals.
Note 2: Rebel Aviation Services have drafted a checklist for Quarterly, Monthly, and Weekly Preventative Maintenance of Refueler trucks.
Why are Refueler Truck Calibration and Preventative Maintenance essential?
Aircraft operators should assimilate that Refueling is a critical operation and has to be performed strictly in accordance with standard protocols, complying with Aviation norms, International standards, and OEM Guidelines. Due to high-pressure underwing fuel transfer operation (40~45 PSI), there is a potential risk of damaging the Transfer system (Pumps, Seals, Hoses, Nozzles, Valves, and Filters) and the Electronics associated with the transfer system (PLCs, Flowmeters, Differential pressure gauges, Displays, and Harness). Therefore, due to the complexity and criticality of the operation, it is essential to deliver clean, carefully regulated fuel while performing fueling operations. An accidental or unregulated flow could potentially damage sensitive and expensive aircraft electronic and avionics systems.
e2b calibration offers industry-leading consultancy and certified PM services for your aircraft Refueler Trucks. At e2b Calibration, we maintain and troubleshoot your deicing trucks so that you can concentrate on maintaining your aircraft. Our labs are ISO/IEC accredited and operated by a team of qualified experts providing training and consultancy services on Refueler truck maintenance and inspection. Our verifiable services are unmatched in the industry. Contact e2b calibration for all your equipment calibration needs.
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