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Today the Australian Transport Safety Bureau (ATSB) released its report on the contaminated aviation gasoline (Avgas) investigation that followed the grounding of thousands of piston engine aircraft across eastern Australia in January 2000.

The investigation found that a very small amount of an anti-corrosion chemical that was not removed in Mobil's avgas refining process in late 1999, and not detected by the usual tests, led to the safety problem.

The ATSB has made 24 separate recommendations that include recommended safety actions for Mobil Oil Australia, US and UK fuel standards bodies, the Civil Aviation Safety Authority, and other Australian regulatory organisations.

ATSB Executive Director Kym Bills said, "The scale of the avgas contamination was an unprecedented event anywhere in the world and was unexpected in such a mature industry as fuel refining. As a result, it caught the refiner and regulators by surprise. The investigation highlighted certain deficiencies in international fuel standards."

The investigation found that a temporary variation in the production process at Mobil's Altona refinery in late 1999 involving problems with reduced caustic wash and increased acid carry over, led to an increased dosage of an alkaline anti-corrosion chemical by a contractor. This was not totally removed from the final avgas. The normal tests for the quality of avgas did not pick up the very small concentration of the chemical contaminant in the avgas that was sufficient to react with brass in aircraft fuel systems and form a black 'gunk' that clogged them.

A number of warning signs and system deficiencies that could have been better dealt with by the refiner and other parties are the subject of safety recommendations.

"ATSB's role is not to ascribe 'blame' to any party. It is our task to uncover the facts including all of the significant contributory factors (including weaknesses in defences), and then to publish findings and recommendations as we have done today.

"As with all ATSB's investigations, it is important that relevant parties learn from these safety deficiencies and act promptly on the 24 recommendations made by us to reduce the chances of a recurrence, either with Avgas or jet fuel, that could endanger flight safety," Mr Bills said.

The report, Systemic Investigation into Fuel Contamination.

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Last update 29 January 2014