Jet fuel contaminated by biodiesel led to an emergency quarantine at Birmingham earlier this year, disrupting supplies and threatening closure of the UK airport.

On 14 May, testing of fuel that had been piped through shared pipelines detected high levels of FAME - fatty acid methyl ester - leading to tanks at Kingsbury supply terminal near Birmingham and the neighbouring international airport being shut.

FAME is blended into diesel to produce automotive biodiesel and because it tends to stick to metal or glass surfaces, can contaminate supply chains that handle both jet fuel and biodiesel. It is a non-hydrocarbon fuel component and limited under current jet fuel specification rules to less than five parts per million (ppm).

The Joint Inspection Group (JIG) sets the operational and quality standards for aviation fuelling in the big jointly operated airports and its Product Quality Committee is co-ordinating industry activity. Following Kingsbury, a JIG bulletin was issued advising suppliers to assess all supply chains against the risk of FAME contamination.

While small volumes of biodiesel - only 1 litre (0.3USgal) of biodiesel in 10,000 litres of jet fuel can put the fuel off-specification - few laboratories can test for FAME at ppm concentrations, meaning test results are available only after delivery.

In response to this, the UK Energy Institute is fast tracking the development of a more widely available test method with defined precision and also producing industry guidelines on tank cleaning for ships, another big risk area.

The industry has also recognised the need for a higher permitted FAME content and the UK Energy Institute is co-ordinating a project with the aircraft and engine manufacturers with the objective of approving 100ppm FAME in jet fuel.

As part of this, Rolls-Royce has scheduled an altitude relight/cold start test in January with results expected in February. Further testing is scheduled for early 2009. Manufacturers are working together, so testing need not be repeated for each manufacturer.

All approval testing will be conducted at four times the required approval level (400mg/kg of a FAME cocktail comprising equal proportions of rapeseed, soy, palm and tallow).

Testing is unlikely to be completed before the middle of 2009, so airlines are being urged to prepare contingency plans and, ideally before an incident occurs, know what to do when fuelled with a contaminated batch, either en route or about to take off.

"We don't want to be scaremongers, but we believe that it is important to get contingency plans in place. This will require the aircraft and engine manufacturers agreeing with airlines what exposure is allowable for short periods until the formal approval for 100ppm is achieved," said Shell's Mike Farmery, chairman of the JIG committee.

Source: Flight International