How Do Crews Detect and Prevent Fuel Contamination?

DALLAS — Crews can prevent aircraft fuel contamination using a combination of testing and preventative strategies. Water, particulate, and microbial contamination can all cause severe damage to an aircraft if left untreated. However, it is possible to detect, eliminate, and prevent contamination in any fuel system.

What steps can crew members take to minimize the risk of aircraft fuel contamination?

Use Fuel Sampling

The standard approach for identifying and addressing aircraft fuel contamination is fuel sampling. The process is straightforward and usually only takes a few minutes. A crew member simply drains a sample of fuel from the aircraft’s tank into a clear cup or container.

In a well-lit area, any contaminants should be visible if the container is held up to the light. Particulate matter is often immediately visible, although water can be harder to spot. It may help to pour a small amount of food coloring into the sample. If water is present, it will attach to the food coloring. Otherwise, the food coloring will sink to the bottom of the container. 

It’s important to make sure crew members drain their fuel samples from a low point in the fuel system. This is because water and particulate matter typically settle rather than float. Sampling “downhill” will drain contaminants out quicker and easier. 

Microbial Contaminant Detection in Samples

Unfortunately, microbial contamination is usually difficult to detect with purely visual inspection. Crew members need to use chemical tests to identify it. The main methods used to test for microbial contaminants are ATP and CFU. 

Some commercial test kits are available today for completing these tests independently. However, they do often require professional lab equipment. For instance, colony-forming unit (CFU) testing conventionally requires incubation, which can only be performed in a lab. A typical lab testing process can take about a week.

Luckily, crew members don’t need to test for microbial contamination as often as they do for water or particulate contamination. Microbial contamination takes much longer to form, often over weeks or months. Additionally, microbial contamination comes from water contamination, so keeping water out of fuel systems can prevent microbial growth from forming. 

Microbial testing is still important, though. Studies have shown that while the risk of microbial contamination is low, the potential damage can be serious. If allowed to grow, microbial contamination can root in fuel tanks, making it very difficult to permanently remove.

It’s also a good idea to check the health of the fuel tank itself periodically. This can be a lengthy process because it requires emptying the tank to inspect the interior. However, it’s worth taking the time to perform a thorough tank inspection now. Microbial growth in this particular area can cause serious physical damage. An inspection also provides a good chance to clean the interior of the tank if needed.

Install Filters

The best way to remove particulate contaminants is through filtering. By installing filters in the fuel system, crew members can often trap and remove all particulate contamination. Filters are often installed in the fuel line right before it meets the engine.

While filters are easy to use, it is vital for crew members to remember to regularly check them. If they get clogged, filters can do more harm than good, depending on whether the filter has a bypass or not.

When aircraft fuel contamination includes particulate matter, it will usually show up in the sampling process. If crew members notice it there, they should definitely check the filters. Otherwise, crew leaders should make a regular schedule for filter inspections to ensure they are analyzed, emptied, or replaced if needed.

What to Do If Contamination Is Detected

If crew members detect aircraft fuel contamination in their tests, there are a few strategies for addressing the issue and any chain reaction it might have.

First, start by simply continuing to drain samples of fuel until they come out clear and free of contaminants. The benefit of sampling from a low point in the fuel system is that most of the contamination will naturally accumulate there. So, crew members can often get rid of it by simply continuing to drain samples.

If there is concern that the contaminants may have caused damage to the aircraft, crew members can run some additional tests. For example, digital detector arrays and ultrasounds are both non-destructive testing methods frequently used to identify aircraft fatigue, damage, and other maintenance issues. Crew members can use both of these without risking further damage to the aircraft.

A non-destructive test of the aircraft as a whole will deliver a big-picture view of its mechanical and structural health. Pay attention to the fuel system and surrounding components, as well as the engine. Fuel tanks are especially likely to experience damage from fuel contamination since microbial growth can collect there unnoticed.

Preventative Best Practices

What can crews do to prevent aircraft fuel contamination from developing? Preventing microbial contamination is relatively easy if crews can prevent water contamination. So, focus on minimizing exposure to sources of water in the fuel system. 

Keep Fuel Lines Full and Covered

Water usually gets in through entry points to the fuel system. Even if it isn’t raining, the air itself can contain moisture that the fuel system may absorb. This is especially common in humid environments. Even in a hangar, an uncapped fuel line is likely to get a bit of dust or small particulate matter in it. 

So, one easy way to prevent aircraft fuel contamination is simply keeping fuel lines covered at all times. Minimizing the amount of air in the fuel lines will also help since this is a common source of water contamination. As a result, it’s a good idea to keep fuel systems topped up as much as possible. 

Use Preventative Fuel Additives

It may sound counterintuitive to add something to aircraft fuel to minimize contamination, but additives can be helpful. In fact, some types of fuel come with anti-contamination additives mixed in. 

Some fuel additives are healthier than others. For example, 100LL fuel is usually sold positive with the additive tetra-ethyl lead, which is designed to help prevent engine damage. The FAA recommends avoiding additives that contain lead, including TEL, like in 100LL fuel. Luckily, more alternatives are emerging today, particularly for small aircraft.

When choosing an additive to minimize water buildup in aircraft fuel, always consider the additive’s safety data. Choose one that is lead-free if possible. Anti-icing additives, like Hi-Flash Hi-Flo, are the most common type used to prevent water contamination.

How to Prevent Aircraft Fuel Contamination

It’s important for crews to establish a system of maintenance procedures to prevent aircraft fuel contamination. If contaminants are left in the fuel system, they will eventually lead to corrosion, physical deterioration, and potentially even permanent damage.

Regular testing and a few best practices can go a long way toward preventing and resolving contamination in aircraft fuel.

Featured image: Airport worker refueling a plane. Photo: Jose Lebron via Unsplash.