On July 1st 2013, Trans Asia Airways schedule revenue passenger flight GE 5111, an ATR 72-500 aircraft, registration B-22806 took off from Taipei Song-Shan airport for Kaohsiung airport with 2 flight crew, 2 cabin crew, and 72 passengers onboard. After takeoff, an overheat caution “OVERHEAT AIR” was illuminated at the instrument panel, the crew requested ATC for air turn back. When flight crew begin to perform abnormal procedures, an “ELECTRIC SMOK” warning sounded and the flight crew declared “Pan Pan” and requested immediate return to land. The aircraft landed safely without further incident.

During climb, the flight crew felt cockpit temperature begin to rise and hot air was blown out from cockpit area, a white vapor like moisture was presented in the cockpit and the temperature indication at upper flight compartment and duct had reached the maximum value of unity. When the aircraft climb to 4,000 feet, a master caution sounded and the captain instructed first officer to request Taipei Approach radar vector to Song-Shan airport. At 5,300 feet, the flight crew had not yet begun to conduct Engine #1 bleed overheat procedures, continuous master warning sounded and ELCE SMK red light at CAP (Crew Alert Panel) was illuminated, and Captain disengaged autopilot and instructed first officer to request emergency landing, and the first officer declared “pan pan”. Both flight crew stated that, they believed there was no electrical smoke therefore memory items were not executed and oxygen masks and goggles were not donned. When the aircraft descended through 3,000 feet, the crew opened the AVIONICS VENT EXHAUST, the vapor disappeared and the warning light stop illuminated and temperature back to normal level. The flight landed at 1631 safely and taxi back to the ramp.

The Aviation Safety Council, after confirmation of this occurrence, organized a team to conduct the investigation. The investigation team included members from Trans Asia Airways, Civil Aeronautics Administration Taiwan and the state of manufacture, represented by France BEA (Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile) including technical advisor from ATR. Investigation Report was published after approval by the ASC council members on February 25, 2014, at the 20th Council Meeting.

Finding related to probable cause of this occurrence is: hot air was continuously vented from air condition outlet, due to malfunctioning Pack #1 duct temperature sensor and temperature limiter that caused the modulating valve kept opening in the occurrence flight; as a result, temperature in the cockpit remained high. The flight crew did not shut off pack #1 immediately which enabled to stop hot air from continuously flowing into the cockpit.

There are 7 Findings related to Risks which include: flight crew believed the vapor like moisture was not smoke and did not conduct SMOKE abnormal procedures when vapor was present in the cockpit during initial climb, the flight crew were not able to correctly identify it was duct overheat, (If they had worked through the abnormal procedures and shut off the affected pack system, they could have stopped the hot air from coming into the cockpit); after ELECTRIC SMOK warning was present, a safer way should be execute smoke procedure memory items then identify the source; the Flight Operation Manuals and the Flight Crew Training Manual of ATR and Trans Asia Airways related manuals did not elaborate guidelines to verify smoke and provide procedures to follow when source of smoke is not clear; Trans Asia Airways did not request flight crew to execute smoke procedures when source of smoke is not clear during training; the captain disengage autopilot without informing the first officer (ATR Flight Operation Manual S
MOK procedure required to maintain autopilot on) and both ATR Flight Operation Manuals and Trans Asia Airways Flight Crew Operation Manual smoke procedures and air condition smoke procedures did not elaborate procedures to eliminate the smoke, thus there was no guidance for the flight crew to expel the hot air/vapor out of cockpit. There are 11 other findings include in the final report.

There is no safety recommendation issued to Trans Asia Airways and Civil Aeronautics Administration Taiwan owing to the concerning organizations and authorities had already implemented preventive and corrective measures to the Findings during the Investigation (details as Investigation Report). There are 3 Safety Recommendations issued to Avions de Transport Regional (ATR)：Use the Flight Safety Foundation (FSF) research as a reference to review the appropriateness and completeness of the design philosophy of ATR smoke procedures; Review the deviation between Flight Operation Manual and Flight Crew Training Manual regarding flight crew task sharing principles during abnormal and emergency situation; Review the emergency procedures in Flight Operation Manual that do not include smoke elimination, revise as appropriate so that flight crew can execute smoke procedures more efficiently.

The report in Chinese can be downloaded at http://www.asc.gov.tw

Contact: Sherry Liu, Engineer
TEL: +886-2-89127388 ext. 330
Email: sherry@asc.gov.tw