Biocide overdose blunder suspected in A321 dual-engine incident

Summary

UK investigators probing a serious dual engine problem on a departing Airbus A321 have discovered its fuel system had previously been overdosed with biocide, after a maintenance engineer misunderstood a measurement term. The engineer was confused by the term ‘ppm’ – meaning ‘parts per million’ – while conducting a biocidal shock treatment of the Titan Airways A321’s fuel tanks, as the jet neared the end of a month-long maintenance check. While the anti-contamination treatment required a biocide concentration of 100ppm, no explanation or instruction for calculating the overall quantity featured in the aircraft maintenance manual task, and the engineer resorted to an internet calculator. But he miscalculated the dose and, instead of the correct quantity of just under 0.8kg, he poured 30kg of biocide into each of the right- and left-hand wing tanks – equivalent to more than 37 times the maximum permitted dosage, given that the tanks both held 6,200kg of fuel. “The task had not been designated as a critical task, and therefore no additional measures were used to check that it was performed in accordance with the [manual],” says the UK Air Accidents Investigation Branch. “No control measures were in place at the [maintenance organisation’s] stores or planning departments to prevent unusually large quantities of chemicals being issued to [engineering] staff.” It adds that the pouring of the biocide directly into the tanks was not an approved process, and it should have been pre-mixed with fuel. While the inquiry suspects the excessive level of Kathon FP 1.5 biocide is connected to the subsequent engine problems, it is still working to understand the impact of the errors. The A321 experienced a number of engine start-up and performance difficulties while conducting flights on 26 February, two days after the aircraft returned to operations post-maintenance. Show Fullscreen But the most serious of these occurred as it took off from London Gatwick on a crew-only ferry to Lond...