AAIB: Biocide overdose in fuel after maintenance caused serious engine issues on Airbus A321
At 00:09 UTC on 26 February 2020, G-POWN took off from London Gatwick Airport for a flight to London Stansted Airport. At approximately 500 ft agl in the climb, there was a loud noise and flames were seen coming from the tailpipe of the No 1 engine as it surged.
The crew made a MAYDAY call and turned right to return to the airport. Two minutes later, parameters relating to the No 2 engine began to fluctuate and the crew received an indication that the engine had stalled. The aircraft landed at 00:20 hrs.
An investigation revealed that the aircraft entered a period of extensive maintenance, starting on 23 January 2020. For most of this time, all the fuel tank access panels were open to allow work to be carried out inside the fuel tanks until 19 February 2020 when the aircraft was moved outside. Once outside, the fuel tanks were leak- checked and treated for moderate microbial contamination.
During the biocidal shock treatment, an excessive quantity of Kathon biocide was introduced into the aircraft’s wing fuel tanks, equating to 37 times the maximum permitted dosage in the AMM.
The AMO engineer who carried out this task had not performed it before and did not recognize that he was using an excessive quantity of biocide. The excessive level of Kathon in the aircraft’s fuel system is suspected to have caused the subsequent problems with the aircraft’s engines.
The investigation is ongoing.