Understanding and Preventing Microbial Contamination in Jet Fuel

    The aviation industry has stringent safety protocols. Even so, it’s not immune to a subtle yet menacing foe—microbes. Microbial growth poses a great threat to aviation systems. It can lead to fuel filter clogging, microbiologically influenced corrosion (MIC), fuel deterioration, and more. Left untreated, these microbes can cause grounded aircraft, system failures, operational disruptions, and in extreme cases, complete engine failure.

    So, why does microbial contamination in jet fuels happen and how it can be prevented?

    Microbial Contamination 

    Microbial contamination in fuel is when bacteria, fungi, yeast, protozoa, and even viruses proliferate in fuel storage and distribution systems. Spurred by optimal conditions ( temperature range of 10-40 degrees C and the presence of water), microbes create biofilms and generate byproducts that compromise the fuel’s integrity. Jet fuel is hygroscopic, meaning it absorbs water from the surrounding air.

    Water also stems from dissolved water in uplifted fuel and condensation due to vented air during normal aircraft operations. This creates an optimal breeding ground for microbes to root in aircraft aviation fuel tanks. And, the microbes feed on the fuel hydrocarbons.

    This phenomenon is particularly exacerbated in regions with hot and humid weather conditions. So, it’s critical for the aviation industry to address this hidden menace as soon as signs are noticed.

    Aftermaths of Microbial Contamination

    Fuel Filter Issues

    Microbial growth in the fuel tank often also creates sludge/sludge-like substances at the tank bottom that can clog the filters. That prompts the filter bypass warning to light up in the cockpit, specifically at take-off. Filter clogging prevents fuel from flowing with full force through the aircraft’s system. Under full power at take-off, it can lead to severe and cascading repercussions—fuel pump failure, reduced engine efficiency, engine failure, etc.

    Besides highly expensive operational setbacks, these mechanical failures can pose significant safety risks if not addressed immediately upon detection. The clogged filters must be checked and unclogged to get the aircraft back to optimal operations. However, the aircraft fuel system may require checking and rectification for more accurate validation and correction. 

    Microbially Influenced Corrosion (MIC)

    Anything from water to environmental factors and changing temperatures can cause corrosion. However, microbial growth poses a significant yet underreported corrosion risk in the aircraft system. If left untreated, the acid produced in the MIC process can cause severe damage to the aircraft structure. For example, it can corrode the structure’s outer surface, pitting on the wing structure, and hi-locks, etc. Fuel in an aircraft is stored in parts such as wings. Any compromise to the integrity of these can lead to catastrophic damage to the overall structural stability of the aircraft.

    Issues With Fuel Quantity Indication (FQI) Probes

    The biofilm created in the fuel due to microbial growth can cover and foul the FQI probes. It can also interfere with the capacitance measurement between the tubes. It often leads to erroneous fuel quantity measurement or a degraded fuel quantity indication. The compromised probes send wrong indications of the fuel tank levels to the cockpit, often reporting higher levels. Malfunctioning probes can result in grounded aircraft. If not replaced, they can also lead to the complete loss of fuel quantity indication for one or several fuel tanks.

    The Imperative for Prevention

    Prevention is a strategic imperative considering the safety hazards and massive operational disruptions microbial contamination can cause to an aircraft. The comprehensive prevention measures the aviation industry must take include:

    • Regular Water Drainage: Ensuring regular water drainage is essential to mitigate the risk of microbial proliferation in jet fuel. Even though jet fuel is sterile by nature, water can infiltrate fuel tanks even during normal operations. That can spur microbial growth in the fuel. The fuel systems on high-end aircraft are designed to handle and reduce water quantity in the fuel tanks. However, implementing regular water drainage strategies ensures no water remains to accumulate. Maintenance crews should follow systematic water drainage protocols to ensure the overall safety, reliability, and performance of aviation fuel systems.
    • Periodic Microbial Testing: To ensure aviation safety and operational efficacy, while maintaining environmental responsibility, periodic fuel testing is a critical necessity. Microbial testing is important for fuel operators. It helps them understand the condition of their fuel and detect contamination early on. Thus, they can take preventive measures to dodge expensive maintenance.

    The International Air Transport Association (IATA) suggests conducting a jet fuel test at least once a year. Operators have a range of options for fuel testing – CPU growth test, ATP test, and immunoassay antibody test. However, for operators looking for immediate and onsite detection of microbial contamination in their jet fuel, leveraging high-end immunoassay antibody kits such as FUELSTAT® by Conidia Bioscience can be a very sensible investment. Unlike ATP or CFU tests, the immunoassay antibody method requires no special/heavy equipment for the detection process. In addition, accurate results can be obtained in 10-15 minutes.

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