What happened
On 25 April 2014, an Airbus A320, registration CS-TKP, operated by Thomas Cook, departed Brussels for Tenerife. During the cruise phase, the crew was alerted by the ECAM to an oil level issue on engine no.1. Shortly thereafter, a Master Warning indicated low oil pressure on the same engine, prompting the crew to reduce thrust to idle and shut down the engine. The aircraft, carrying 179 passengers and 7 crew members, diverted first to Bordeaux-Merignac.
While preparing for arrival in Bordeaux, the crew received a Master Caution alert indicating a low hydraulic level in the yellow system. To avoid a more complex dual hydraulic failure, the crew chose to limit the application of the ECAM procedure, specifically electing not to shut down the yellow system pumps. Following instructions from the operator, the flight diverted again, this time to Toulouse-Blagnac Airport.
During the final approach at Toulouse, the crew transitioned the aircraft to configuration 1. This movement caused pressures in both the yellow and green hydraulic systems to drop significantly. Although pressures temporarily recovered before landing gear extension, the high hydraulic demand during the landing roll—driven by the use of flight control surfaces and the engine 2 thrust reverser—triggered a dual hydraulic failure. The aircraft came to a stop on the runway with the nose gear steering inactive and several flight control surfaces, including spoilers and slats, remaining extended.
The investigation
Investigators examined the aircraft's maintenance history and physical components following the incident. A hydraulic fluid leak was identified at the junction between the engine no.2 pylon and the engine. The investigation revealed that a sealing ring for this connection had been displaced from its housing, likely due to an error in tightening during a recent maintenance task.
Regarding the engine no.1 oil issue, the investigation focused on recent maintenance performed on 25 April, involving the replacement of the engine-driven pump. Investigators considered two possibilities: either the O-ring on the pump drive shaft was incorrectly positioned or damaged during the swap, or an internal failure of the magnetic seal occurred due to long-term deterioration.
Findings
- The yellow hydraulic system failure was caused by an incorrectly performed maintenance operation involving a loose connection.
- The engine no.1 oil pressure drop was attributed to either recent pump maintenance errors or the deterioration of a magnetic seal.
- The crew's decision to partially bypass the ECAM procedure for the yellow system low level—intended to prevent a dual failure—unintentionally left the aircraft vulnerable to the hydraulic depletion that occurred during the landing roll.