U28735 - Incident: Easyjet A320 near Geneva on Aug 7th 2016

An Easyjet Airbus A320-200, registration G-EZUP performing flight U2-8735 from London Gatwick,EN (UK) to Bastia (France) with 129 passengers and 6 crew, was enroute at FL350 about 110nm south of Geneva (Switzerland) in French Airspace when the crew reported a bleed air leak on the left hand wing (engine CFM56) and decided to divert to Geneva. The aircraft landed safely on Geneva's runway 05 about 35 minutes later.

The occurrence aircraft remained on the ground in Geneva for about 21 hours, then positioned to London Gatwick and resumed service.

Switzerland's SUST reported they have opened an investigation into the occurrence advising the occurrence has been rated an accident.

The SUST released their summary report in French only (Editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a French only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).

The SUST now rated the occurrence a serious incident and analyses and concludes (in one):

The decision to divert was adequate and the diversion was carried out correctly after consultation with the operations center.

The "AIR L WING LEAK" procedure was properly applied without delay.

Communication with the cabin crew helped to keep passengers informed and out of danger.

The erroneous understanding of a fuel leak by emergency services instead of a bleed air leak had no consequences.

The diversion could have certainly been avoided if maintenance had processed 17 post flight messages reporting the (same) problems in the days prior to the diversion.

For this reason the SUST waives further investigation measures and concludes the investigation with the summary report.

The SUST reported the aircraft was enroute at FL350 when a warning light as well as the ECAM "AIR L WING LEAK" occurred. The bleed air valve #1 automatically closed according to the system logic thus isolating the leak. The crew carried out the relevant checklist procedures and checked the Minimum Equipment List to determine whether the aircraft was in a condition to perform the return flight, however, it turned out the aircraft needed repair before being able to depart for the return flight. The crew consulted with the operations center who informed the crew that a repair in Bastia could not be carried out. The crew subsequently informs ATC about the bleed air leak and requested the diversion to Geneva. Cabin crew was briefed, the diversion was announced to the passengers. The approach and landing was normal, the crew however was surprised that four fire trucks received the aircraft, the firemen inspecting the outside of the aircraft and subsequently entered the cockpit to tell the crew, they could not observe any fuel leaks. It turned out when the crew reported a bleed air leak, the ATC understood fuel leak.

The leak was located in the area of the air conditioning pack #1 downstream of the control valve between the air cycle machine and compressor intake. The seal was deteriorated and one of 8 screws was missing. The damaged seal could be the cause of hot air that was detected by the sensor chains. The seal is a spare part that could have been replaced on site by operator maintenance. The screw could have been damaged by mishandling or excessive tightening which could result in poor tightening of the other screws, however, the missing screw could not have caused the leak.

The read out of the flight data recorder revealed that this defect of the sealing had been reported 17 times in post-flight reports of previous flights.

In each wing the pneumatic system is being monitored by two chains of sensors (Loop A and Loop B). The systems work in parallel offering redundancy. If bleed air leaks the hot air causes the temperature to rise locally and trigger the sensors nearby. A leak detected by a single loop is being recorded in the post flight report. When both loops detect the leak, an alert is issued to the flight crew.

The pack seen after landing (Photo: SUST):

Related Flight: U28735, EasyJet News