Safe and Effective Fuel Tank Maintenance

An aircraft fuel system consists of a complex network of components that work together to store and deliver an appropriate amount of fuel to the engine(s). With constant exposure to aircraft fuel, these systems are particularly prone to corrosion and degradation, making strict preventative maintenance protocols necessary. In this article, we will discuss the various nuances associated with fuel tank maintenance.

Fuel tanks may be broadly categorized as external or internal based on their location about the fuselage. The internal tanks may be further divided into the integral, removable, bladder, or tip tanks. Integral tanks are built into the structure of the aircraft, most commonly the wings and empennage, and cannot be removed or accessed without an inspection panel. Meanwhile, the rigid removable tanks are designed to fit inside a specialized compartment that allows for their quick removal if necessary. Bladder tanks consist of one or more stretchable rubber bags secured to particular aircraft regions. Since these bags are held in place only by means of snap fasteners and cords, they can be easily removed for replacement and inspection. External tanks are much easier to access and perform maintenance on, but they also contribute to a decreased aerodynamic profile.

Before attempting to inspect or replace a fuel tank, several precautionary safety measures should be taken. Of particular concern to maintenance personnel is adequate ventilation, as lack of airflow can instigate a fire which can result in an explosion if further inhibited. Ventilation also decreases the concentration of carcinogenic and toxic vapors, helping mitigate exposure. Although this is often difficult to achieve due to fuel tank architecture, many shops prefer to employ a fan or other positive air pressure device to assist in movement. Another health hazard that may occur during fuel tank inspection is hypoxia, in which the maintenance member receives suboptimal levels of oxygen due to the displacement and exposure of gas as fuel vapor or fire-retardant nitrogen.

In addition to ventilatory support, care should be taken to ensure all other safety standards are met before proceeding with the inspection. Namely, the tank should be completely emptied of fuel using manufacturer-recommended protocols. After this has been completed, the rest of the fuel delivery system should then be turned off to prevent any accidents. Finally, the aircraft should be electrically grounded and adequate fire protection measures should be placed nearby.

Once inside the fuel tank, personnel should inspect the entire system for signs of wear, damage, and leaks. It is also necessary to ensure all securement devices are tight and not nearing corrosion. Since drain plugs and valves should be readily visible from inside the tank, they too should be inspected for sediment or other debris. Moreover, any movable parts that can be easily manipulated should be checked to ensure proper fluid motion. If the fuel tank includes an inhibitor cartridge, then it should also be replaced if nearing empty.

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