China Airlines A333 near Ho Chi Minh on Jun 3rd 2013, loss of cabin pressure

A China Airlines Airbus A330-300, registration B-18317 performing flight CI-781 from Taipei (Taiwan) to Ho Chi Minh City (Vietnam) with 185 passengers and 15 crew, was climbing through 1500 feet out of Taipei when the crew received a right hand bleed air fault (engine CF6). The crew continued the flight, climbed the aircraft to FL400 and attempted to reset the right hand bleed air system however to no avail. The aircraft had already started to descend descending through FL380 towards Ho Chi Minh City (former Saigon) when the left hand bleed air system was indicated failed shortly followed by excess cabin altitude. The crew initiated an emergency descent and landed the aircraft safely on Ho Chi Minh Airport's runway 07R.

The French BEA reported in their weekly bulletin quoting Taiwanese Authorities, that Vietnamese Authorities delegated the investigation of the occurrence rated a serious incident to Taiwan's Authorities.

On Nov 22nd 2013 Taiwan's Aviation Safety Council (ASC) released their factual report in Chinese as final report arguing that no safety recommendations would result from the investigation and stating that about one minute after becoming airborne the right hand bleed air system failed. The crew succcessfully reset the system, however, another minute later the system failed again. The crew continued the flight and had already begun the descent towards Ho Chi Minh about one minute after leaving cruise level the left hand bleed air system indicated failed prompting the crew to accelerate the descent. After a cabin pressure warning activated the crew donned their oxygen masks, declared Mayday and initated an emergency descent to 10,000 feet. The passenger oxygen masks were not released. The investigation found that the right hand fan thermostat valve was defective and the left hand sealing gasket of the fan thermostat valve was contaminated so that both valves could not open sufficiently to provide sufficient supply to the air conditioning systems. As a result the engine pressure regulating valves were closed causing the failure of both air conditioning systems.

The return flight CI-782 was cancelled.

The incident aircraft was able to depart for the return flight, callsign CAL-782, after 13 hours on the ground, climbed to FL410 right after departure and reached Taipei with a delay of 11.5 hours.