The International Air Transport Association has raised safety concerns about possible microbial contamination of fuel stored in aircraft grounded during the Covid-19 pandemic. In a recent webinar hosted with Airlines for America (A4A) and the Joint Inspection Group (JIG), IATA also warned that the dangers could extend to fuel storage units that are seeing less demand as a result of some 16,000 airliners being inactive due to the crisis.
JIG is the organization responsible for the development of aviation fuel supply standards covering the entire supply from refinery to aircraft. Lee Taylor, a member of its technical team and a qualified inspector, explained that the three sides of the microbial growth triangle are jet fuel, microbes in the surrounding environment or as the result of downstream contamination, and water, which creates and sustains a viable environment for organisms to grow and thrive.
Due to the prevalence of microbes, eliminating them from the system is virtually impossible, so the goal, Taylor said, is preventing the conditions that can cause rapid proliferation of the microbes, which can lead to fuel system fouling and corrosion.
Onboard the aircraft the problems can include malfunctioning of fuel gauges, rapid filter clogging, corrosion throughout the wing tanks and fuel system, and the necessity of increased maintenance while in fuel farms. Microbe proliferation also can result in poor filter performance and so require more frequent cleaning to remove the accumulating biofilm. Since water is heavier than fuel, most microbial growth will be found at the bottom of the tank or at the water/fuel interface layer.
Taylor noted that while always a part of the routine daily assessment of fuel quality, visual inspection of samples during this time is even more crucial. “Not only does it provide an early indication of general contamination such as dirt and water, but also the presence of severe microbial contamination,” he commented, adding that removing the water by good housekeeping techniques such as routine sampling and system flushing is the best way to inhibit microbial growth.
For airports with hydrant fueling systems, Taylor said it is also vital to conduct effective routine maintenance of below-ground piping, where sediment and water can accumulate.
When it comes to testing for microbial contamination, the more sampling and testing the better, according to Amy Carico, A4A’s director of fuel services and technical standards. She told the webinar that results can be different depending on the location in the tank from which the sample came.
Carico said that water is present in all fuel, and there is no way to avoid having it in the system. She explained that as the fuel cools, any water molecules suspended in it will fall out of solution to accumulate at the lowest points of the tank or system, and from there is where samples should be taken. Indications of contamination can include foul odors, brownish water, particulate matter, a lacy foam between the water and fuel layers, slime or sludge, and discoloration on filters, but as Carico noted, a contaminated system may exhibit none of those symptoms. Once a sample is taken it should be tested as soon as possible because the amount and types of microbes present can change in just a few hours.