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ASN Wikibase Occurrence # 233878
Last updated: 9 June 2021
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Time:c. 00:10 UTC
Type:Silhouette image of generic A321 model; specific model in this crash may look slightly different
Airbus A321-211
Owner/operator:Titan Airways
Registration: G-POWN
MSN: 3830
Fatalities:Fatalities: 0 / Occupants: 7
Other fatalities:0
Aircraft damage: Minor
Category:Serious incident
Location:near London-Gatwick Airport, Horley, Surrey -   United Kingdom
Phase: Take off
Departure airport:London-Gatwick Airport (LGW/EGKK)
Destination airport:London-Stansted Airport (STN/EGSS)
Investigating agency: AAIB
As part of scheduled maintenance overseas, Airbus A321-211 G-POWN underwent a biocide shock treatment on its fuel system, using Kathon biocide, to treat microbial contamination. The aircraft returned to the UK on 24 February 2020, once the maintenance was complete.
In the 24 hours preceding this serious incident, there were abnormalities with the operation of both engines across four flights. On the flight before the fourth (event) flight, the crew reported momentary indications of a No 2 (right) CFM56-5B3/3 engine stall. After the aircraft landed, this was investigated using an inappropriate procedure obtained from an aircraft troubleshooting manual not applicable to G-POWN, but no fault was found.
The aircraft took off from London Gatwick Airport runway 26L at 00:09 hrs on 26 February 2020 but, at around 500 ft agl, the No 1 (left) engine began to surge. The commander declared a MAYDAY and turned right downwind for an immediate return to the airport but, shortly afterwards, the crew received indications that the No 2 engine had stalled. The crew established that the engines were more stable at low thrust settings and the thrust available at those settings was sufficient to maintain a safe flightpath. They continued the approach and the aircraft landed at 00:20 hrs.

The investigation identified the following causal factors:
1. G-POWN’s fuel tanks were treated with approximately 38 times the recommended concentration of Kathon.
2. The excessive Kathon level in the aircraft’s fuel system caused contamination of the engine Hydro Mechanical Units (HMU) resulting in a loss of correct HMU regulation of the aircraft’s engines.
3. A troubleshooting procedure was used for the engine No 2 stall that applied to LEAP-1A32 engines, but G-POWN was fitted with CFM56 5B3/3 engines. The procedure for CFM56-5B3/3 engines required additional steps that would have precluded G-POWN’s departure on the incident flight.

The investigation identified the following contributory factors:
1. The Aircraft Maintenance Manual (AMM) procedure did not provide enough information to enable maintenance engineers to reliably calculate the quantity of Kathon required, and the specific gravity value of Kathon was not readily available.
2. There were no independent checking procedures in place at the base maintenance Approved Maintenance Organisation (Base AMO) to prevent, or reduce the likelihood of, calculating and administering an incorrect quantity of biocide.
3. There were organisational factors at the Base AMO that contributed to the incorrect Kathon quantity calculations. In particular, the workload was high for the available facilities and personnel, and there was no internal technical support function for engineers to consult when they were uncertain.
4. The manufacturer’s recommended method of searching the troubleshooting manual was not used to find the applicable procedure relating to the engine No 2 stall.


1. AAIB Final Report:
2. AAIB Special Bulletin:

Accident investigation:
Investigating agency: AAIB
Status: Investigation completed
Duration: 1 year and 2 months
Download report: Final report
Other occurrences involving this aircraft

6 May 2012 OE-LET NIKI Luftfahrt GmbH 0 Wien-Schwechat International Airport - LOWW min


Photo of G-POWN courtesy

Glasgow - International (EGPF / GLA)
17 February 2021; (c) David Unsworth

Radar track of G-POWN with timing of significant events highlighted Figure: AAIB

Revision history:

11-Mar-2020 14:36 harro Added
21-Apr-2020 16:25 harro Updated [Total occupants, Source, Narrative, Photo]
30-Apr-2020 10:39 Anon. Updated [Source, Narrative]
21-Oct-2020 22:20 Dr. John Smith Updated [Source, Embed code, Narrative]
04-May-2021 19:06 Dr. John Smith Updated [Location, Source, Embed code, Narrative]
04-May-2021 19:09 Dr. John Smith Updated [Embed code]
05-May-2021 12:26 Dr. John Smith Updated [Source]
05-May-2021 19:08 harro Updated [Source, Embed code, Narrative, Accident report]

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