EASA issues Emergency Airworthiness Directive for A359s due to possible fuel/air ignition in fuel tanks. On Aug 24th 2017 The European Aviation Safety Agency (EASA) released Emergency Aiworthiness Directive (EAD) 2017-0154-E for all Airbus A350-941 aircraft stating:
In the A350 design, the hydraulic fluid cooling system is located in the fuel tanks. Recently, an overheat failure mode of the A350 hydraulic Engine Driven Pump (EDP) has been found. Such EDP failure may cause a fast temperature rise of the hydraulic fluid.
This condition, if not detected and corrected, combined with an inoperative Fuel Tank Inerting System (FTIS), could lead to an uncontrolled overheat of the hydraulic fluid, possibly resulting in ignition of the fuel-air mixture in the affected fuel tank.
Airbus have released an updated Master Minimum Equipment List “that incorporates restrictions to avoid an uncontrolled overheat of the hydraulic system”. Several items have changed to “NO GO”.
The new dispatch requirements and MEL requirements must be implemented on the next flight.
The EASA advises that this EAD is an interim measure, additional Airworthiness Directives may follow.