An airline carrier was seeking to increase the efficiency of their regular biocide programme and testing regime to identify and tackle the problem of contamination by microorganisms, as it meant the loss of several days per year and revenue generation while carrying out this vital investigation.

The airline identified its testing regime based on the Colony Forming principles as a major factor in this downtime. They were concerned with the high costs of treatment, the impact on aircraft availability, as well as the safety issues of sending aircraft into flight potentially with contamination awaiting results or by potential over treating with biocide (the ‘bugs’ develop resistance) over time.

The Solution

FUELSTAT® on-site fuel testing kits offered substantial opportunity to save costs, reduce the risk of an aircraft not being available, and by only treating aircraft that have been identified with contamination, it reduced the risk of over-treating as much as is possible.

FUELSTAT® gives results in 10 minutes in a simple to interpret format (traffic light system for results) and its long reliable track record in Aviation and other Fuel Markets gave the assurance of dependability that the airline required. The airlines also chose FUELSTAT® for its ability to be carried out in the hangar, or at line maintenance, by non-skilled workers and was not prone to cross contamination.

The Outcome

Samples from the FUELSTAT® test were as representative as possible because they were being tested almost immediately (heat is a considerable factor in changing composition of fuel samples). Additionally, as the FUELSTAT® kit required virtually no labour input, no special laboratory or conditions, it meant that the airline gained all these benefits at less than 50% of its previous costs, without taking fuel transport or lost days availability costs into account.

Now less than 5% of samples are being treated, which makes the change to FUELSTAT® testing a very good decision for the airline as it has reduced costs and improved its safety position so it can continue to offer best value without compromise to its customers 

Leon Jennings


A Hunter 376 US built yacht had her engine conk out navigating between the Greek islands. There was no wind so the only choice was third party assistance. The owner and captain from a neighbouring yacht also on passage (who by chance was a yacht surveyor by profession) swam across to offer assistance. On inspection a fuel line blockage was discovered.

The engine was started again from a Gerry can of fuel. This wasn’t a workable solution as the excess diesel from the return pipe was spewing out through the full tank breather tube and began sloshing around the deck creating an environmental and fire hazard. The good Samaritan surveyor assisted in towing the yacht back to port in this case Nidri in Kephalonia where local engineers undertook a clean up.

Unfortunately, the yacht owner stopped short of the surveyors recommendation of a full clean through and only dealt with the blockage, stopping before the injectors. As the diesel bug was still there it flared up again on a subsequent voyage only this time there was no good Samaritan to assist. The tow back and subsequent 2nd diesel bug clean-up bill ran to more than 1000Euros.

The Americas

A major international airline became concerned with increasing numbers of cases of jet fuel fungus contamination in their single-aisle fleet. Aircraft flying into airports with less than sophisticated fuel systems, seemed to be most susceptible, with 10 to 20% of their aircraft being contaminated with the jet fuel fungus every year. To overcome the problem the airline introduced stringent procedures into their maintenance programmes. The procedures included regular water drains from the fuel tanks and jet fuel fungus testing. Now, 5 years on, the airline reports that cases of jet fuel fungus are almost unheard of. The airline uses Conidia’s Fuelstat® resinae kit as its front line test against the Jet fuel fungus.

The Pacific Rim

A regional operator was experiencing severe jet fuel fungus contamination across the whole fleet, on both internal and international routes. The airline approached Conidia Bioscience Ltd for advice on testing and maintenance procedures that would reduce or eradicate the jet fuel fungus problem. Conidia Bioscience Ltd pointed them to the IATA Guidance Material on jet fuel fungus in Aviation Fuel Tanks, which had recently been published. The Guidance Material includes best practice advice on the whole issue. The airline adopted those procedures, and chose Conidia’s Fuelstat® resinae kit for testing their fuel tanks. The airline’s risk assessment of their aircraft routes showed that jet fuel fungus contamination occurred more quickly on some sectors than others. Accordingly, the test intervals vary between aircraft dependent upon their utilization. The problem is now under control, although they still find cases of jet fuel fungus contamination, but at the Moderate level, not the Heavy level.


A major international airline decided that it was safe to return deplaned fuel into their own on-airfield storage tanks using the one-in-nine principle. This principle states that one litre of deplaned fuel will be absorbed into nine litres of clean fuel resulting in ten litres of clean fuel. The deplaned fuel was filtered when it was deposited into the fuel storage system and then again when it was uploaded into an aircraft. However, the airline soon noticed that they had a fleet-wide case of contamination of jet fuel fungus. Having studied the situation it became clear that the one-in-nine principle was fatally flawed. Further investigation showed that the filtration was removing the larger contaminants (mainly the moulds) but the single cell organisms (mainly bacteria and yeasts) passed through the filters and re-infected the aircraft.

Business Jets

A major fractional business jet operator found that one particular type of aircraft seemed very susceptible to jet fuel fungus contamination. The maintenance engineers also reported that they could not detect the jet fuel fungus using the FUELSTAT® resinae test kits, which gave accurate readings on all other aircraft types. A study into the problem found two causes. The first problem was that this type of aircraft had a refuelling point on top of the wing. This resulted in much larger volumes of water finding its way into the tank than was the case in aircraft with under-wing refuelling points. The extra water gave the jet fuel fungus a much better chance of establishing itself and creating a problem. The second issue was that the engineers were draining the water out of the tanks prior to testing and then using the fuel in the FUELSTAT® resinae test. Unfortunately, all the evidence of jet fuel fungus contamination was drained away with the water and an incorrect reading was obtained. The airline introduced more frequent water drains on this type of aircraft, and started using the water phase for the Fuelstat™ tests. The number of cases of jet fuel fungus contamination dropped away markedly, and the results obtained from the Fuelstat® tests gave accurate results from then on.