Water trucks or carts are self-contained mobile vehicles designed for servicing portable drinking water facilities to commercial, corporate, and business aircraft. These carts deliver water by designated filling hoses connected directly or indirectly to the airport water system. The pumping system is often DC (Direct Current) based 12 Volt Motor – Pump system, with the necessary hose and fitting arrangements to service any aircraft type. The carts are flexible and can be towed by hand or by a towing vehicle from the parking facility to the aircraft.
Aircraft Water Carts – Operation Principle and Types:
Water carts can be classified based on the build quality, storage capacity, power source, and towing mechanism. The following section details all the types of portable water carts available:
- Classification based on build quality: Water storage tanks are either built of Stainless steel or High-density polyethylene tank with UV inhibitor. Depending on the source water quality, climatic conditions, operators can select steel built or plastic built water carts. To provide optimal temperature and restrict BOD (Biological oxygen demand) to safe limits, heaters are also built with certain water carts.
- Classification based on storage capacity: Water carts have various storage capacities, starting from 30 gallons to 100 gallons. Selection can be based on the aircraft size and the frequency of service.
- Classification based on power source: Water carts are often electric battery (12 DCV) driven; however, based on the pressure and flow rate requirements, the pumping capacity of the cart varies.
- Classification based on towing mechanisms: Like lavatory and other ground staff equipment, portable water carts are also provided with a manual or vehicle towing facility. In general, smaller-capacity carts are manually towed, and larger carts are towed with ground support vehicles at moderated speeds.
Operational Guidelines & Preventative Maintenance of Water carts:
FAA Considers water carts as necessary ground support equipment, and proper maintenance and inspection are vital. OEMs make the following recommendations for operating the water carts:
- Water Source: Portable water to the water cart should be sourced from an FDA-approved (appropriate regulatory body) storage facility. This eliminates built-up of organic content within the storage tank and ensures clean water supply to the aircraft.
- Plumping and Hose: At all times, the supply hose provided by the OEM should be capped (when not attached to the cart), to avoid seepage of surrounding dust or hazardous substance into the storage tank.
- Plumping and Hose: The Dome vent should be secured and not plugged or obstructed. A plugged vent can potentially damage the water cart.
- Tank maintenance: The storage tanks should be cleaned with OEM-recommended cleaning kits on a frequent basis. SS (stainless steel) tanks often get rusted, and the HDPE (high-density polyethylene tanks) accumulate organic built up.
- Pump and Electric motor: Pressure built should be within specified limits. Damaged pressure gauges and flow meters should be immediately replaced.
- Running gear: Wheels and tires should be inspected daily. Unusual tire wear, cuts, leakages, and damaged fasteners need to be replaced or repaired at once. Bearings should be inspected every six (6) months.
- Towing mechanism: Towing bars should be visibly inspected for cracks. Necessary greasing and lubrication for the couplings should be applied.
- Electrical connections: While filling the cart’s tank, it is recommended to avoid spillage. This can lead to water percolation into electrical systems and damage. Therefore, ensure that the spill vent is open while filling water.
- Battery and Charging system: Often non-trickle, 12 V DC batteries are used to supply necessary electric voltage for the pumps. Care should be taken to avoid excess voltage supply or frequently overcharging the batteries, which can potentially reduce its service life.
Common repairs of Water carts:
In general, OEM (Original equipment manufacturer) guidelines should be followed for the removal and replacement of a part or assembly. Manual repairs and plumbing adjustments can be restricted to common shop practices. To modify or route the plumbing lines, it is prescribed to consult OEM for approval before the design change. Change or replacement of pumps should also be performed as defined by the OEM. Design specifications of the stock pump should match the parameters of the replacement pump. This avoids excess load on the battery and maintains its service life.
Why are Water Cart Service and Preventative Maintenance essential?
Water cart operation should follow certain maintenance guidelines (described in the earlier sections) to supply steady, clean water to the aircraft. Following are certain critical components on a water cart:
- Pump: Due to frequent operation, the delivery pump can be physically damaged. The required pump delivery pressure should be inspected at frequent intervals to ensure design flow rates are maintained.
- Fluid level gauges: Level gauges indicate the quantity of water present at any instance. Due to operational errors, float or level gauge can provide erroneous readings, and hence annual calibration shall avoid spillage.
- Electrical systems: Due to repeated usage or operational errors, cables can get damaged. To avoid short circuits which can damage internal components, frequency inspection of cables is essential.
Therefore, aircraft operators should assimilate that water carts are critical equipment and failing to maintain proper hygiene and preventive maintenance standards will potentially harm the passengers or the aircraft components. It is essential to deliver clean, carefully regulated portable drinking water every time a water cart is connected to the aircraft.
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