History of the Flight
On 20 May 2023, an Airbus A320, registration A6-EIX, operated by Etihad Airways, was scheduled as flight EY535 from Abu Dhabi International Airport (OMAA), United Arab Emirates, to Beirut Rafic Hariri International Airport (OLBA), Lebanon. There were 122 persons on board: 114 passengers, 2 flight crewmembers, and 6 cabin crewmembers. The commander was the pilot flying and the copilot was the pilot monitoring.
During the takeoff roll at 1736:48 UTC, when the aircraft was at 47 knots ground speed and 49 knots indicated air speed, an electronic centralized aircraft monitoring (ECAM) alert "VENT SKIN VALVE FAULT" triggered, followed by a master caution activation. The commander decided to proceed with the takeoff, and the aircraft lifted off at 1737:21.
After completing the takeoff/climb checklist, at 3,000 feet mean sea level (MSL), the crew initiated the abnormal procedures associated with the ECAM alert. They set the avionics ventilation system extract and blower pushbuttons to the override position. As the aircraft continued to climb, the cabin did not pressurize normally; the cabin rate of climb was similar to the aircraft's actual rate of climb. At 1744:31, while passing 11,400 feet MSL, the crew stopped the climb and leveled off at 11,600 feet MSL. The master warning triggered with ECAM warning "Cabin Excess Altitude". Following standard procedures, the crew descended to 10,000 feet at 1744:49, reaching 9,980 feet MSL. The pilot monitoring initially declared mayday but later cancelled it, as the cabin altitude was not expected to exceed 10,000 feet. The flight data recorder showed the cabin altitude never exceeded 10,000 feet.
At 1753, the aircraft entered a holding pattern to coordinate with maintenance and network operations centers. After the technical status was confirmed, the commander decided to return to the departure airport. The aircraft held for 1 hour 55 minutes to burn off fuel to reach maximum landing weight. It exited the hold at 1948:22 and landed at 2020:53 without further events.
Aircraft and Personnel Information
The aircraft, an Airbus A320 with manufacturer serial number 6134, was manufactured in 2014 and delivered to Etihad Airways on 24 June 2014. It was fitted with two IAE Aero engines. At the time of the incident, the airframe had accumulated 30,507 hours and 9,684 cycles since new. The most recent A-check was conducted on 21 February 2023. The flight technical logs indicated a deferred maintenance item under MEL 21-26-04A.
The commander held a valid ATPL and medical certificate, with a condition to wear prescription glasses for near vision. The copilot also held a valid ATPL and medical certificate. Both had completed the operator's mandated training.
Technical Background
The avionics ventilation system cools avionics components using two fans and skin air inlet/outlet valves. It has three configurations: open circuit (on ground), closed circuit (in flight), and partially open circuit. The skin air outlet valve (SAOV) is an electrically operated single flap valve with a smaller flap. Post-incident maintenance identified that the SAOV was in the fully open position.
Conclusion
No damage to the aircraft, property, or environment occurred. The incident was classified as an incident. The probable cause has not been determined by the investigation.