China Airlines will modify its training syllabus to allow pilots to better manage dual bleed air faults following an incident aboard one of its Airbus A330-300s in June.
The incident involved an A330, registered B-18317, which was operating flight CI781 from Taipei Taoyuan International airport to Tan Son Nhat International airport in Ho Chi Minh city on 3 June with 200 passengers and crew on board.
Approximately one minute after take-off, the aircraft’s electronic centralised aircraft monitoring (ECAM) system displayed a message indicating a fault with the number two engine bleed air system. After executing the ECAM procedures, the crew continued ascending to a cruising altitude of 40,000ft (12,200m). The crew reset the bleed air system, but the same message was displayed shortly afterwards. Nevertheless, the flight continued.
As the aircraft descended around 110nm (204km) northeast of its destination, an ECAM alert showed that the bleed system on the number one engine was also experiencing a fault. In response to the fault, the crew activated the aircraft’s speed brakes to speed the aircraft’s descent. At this time, the the cabin was pressurised at 6,720ft.
Three minutes later, the ECAM displayed a “CAB PR EXCESS CAB ALT” message as cabin altitude pressure rose to 9,536ft. In accordance with procedure, the pilots donned oxygen masks and declared a mayday to ATC. However, masks were not deployed in the passenger cabin.
The crew descended to 10,000ft. They observed the cabin and cockpit altitude were "normal" and decided to cancel the mayday call. The crew then continued on a normal descent and arrived at Ho Chi Minh with no damage to the aircraft and or injury to passengers.
With the aircraft on the ground, CAL maintenance personnel replaced the fan air valve thermostats on both engines, which resulted in the systems returning to normal. Engineers also attempted to retrieve the cockpit voice recorder, but failed to disconnect the power supply, which resulted in the incident being over-written.
A Taiwan Aviation Safety Council (ASC) investigation found that contamination from broken O-rings in both fan air valve thermostats reduced the openings of the fan air valves, resulting in an over temperature that triggered the excess cabin altitude warning.
It also found that the A330’s ECAM did not have a procedure for handling dual engine bleed faults, nor was there any training for it in CAL’s A330 syllabus. There were also inconsistencies between the operator and manufacturer’s procedures for handling the fault.
As a result of the investigation, CAL has made a number of changes related to the maintenance on its fan air valve thermostats, and revised checklists for ground personnel for retrieving cockpit voice recorders.
CAL has also committed to implementing training for dual engine bleed faults as part of its recurrent training from 2014. Temporary revisions were also made to its operations manual to remove the inconsistency.
The ASC adds that Airbus has revised the dual bleed fault ECAM procedure in the A330’s flight warning computer, which was certified in August 2013.