On February 4, 2015, TransAsia Airways Flight 235 loses both engines shortly after takeoff and then plummets, inverted, into the Keelung River in Taipei, Taiwan. In episode 103 of Take to the Sky: the Air Disaster Podcast, we cover the shocking sequence of events that led to the disaster that killed 43 of 58 people onboard, including all three pilots and two cabin crew members. The ASC investigation found that a faulty torque sensor thought that the right engine was failing, even though it was not, and so the engine feathering system was activated. This caused a master caution warning to sound in the cabin. However, due to his inability to multitask and handle emergency situations according to the ASC, the pilot flying the plane accidentally shut down the left engine instead of the right engine. Without engine power, the plane stalled, banked to the left, and plummeted into the river. The investigation revealed that the pilot flying had a history of “insufficient knowledge leading to hesitations” during verbal tests about what to do during an engine shutdown on takeoff or loss of electronic engine controls, according to the report. The ASC report also highlighted the many failings of the airline itself, which had grown exponentially without forming a solid foundation of pilot training. As Flight 235 was the second fatal accident for TransAsia Airways in less than two years, the airline eventually ceased operations in November 2016.
TransAsia Airways Flight 235 Departs Taipei for Kinmen with 58 People Onboard
It's February 4, 2015, and TransAsia Airways Flight 235 is getting ready to takeoff from Taipei headed for its one-hour journey to Kinmen, Taiwan, just off the coast of mainland China. Onboard are 53 passengers, including 49 adults and 4 children.
Also onboard we have 5 crew members, including three highly trained pilots in the cockpit and two flight attendants in the cabin. Captain Liao Chien-tsung is 42 and has a total of almost 5,000 flight hours (including 250 hours on the aircraft type they’re flying today). He is also a former military pilot. His co-pilot, who is also a captain, is Liu Tze-chung, 33, who has almost 7,000 flight hours, including over 5,000 hours on the aircraft type they are flying today. Joining them is a third pilot and observer, Hung Ping-chung, 63, who sits in the cockpit jump seat.
Speaking of the type of aircraft they are flying today, it is an ATR 72-600 series aircraft, which is a twin-engine turboprop, short-haul regional airliner developed and produced in France and Italy by aircraft manufacturer ATR. Not surprisingly, the number "72" in its name comes from its passenger-carrying configuration, which could seat 72–78 passengers. This specific series, the ATR 72-600, featured various improvements over prior models to increase efficiency, dispatch reliability, lower fuel burn, and operating costs. While broadly similar to the earlier -500 model, key differences include improved engines and a new glass cockpit.
As we have covered in previous episodes, a “glass cockpit” means here that their cockpit features electronic (or digital) flight instrument displays, typically via large LCD screens, rather than the traditional style of analog dials and gauges. Basically, state-of-the-art onboard systems and displays.
Shortly After Takeoff TransAsia 235 Right Engine Flames Out
Soon, just before 11 AM local time, Flight 235 is cleared for takeoff, and they begin their takeoff roll. Within seconds, the plane’s speed reaches V-1, the point beyond which the plane cannot abort a takeoff – it’s the commitment threshold. Right after liftoff, Captain Chien-tsung engages the autopilot and programs the plane’s airspeed and altitude. As Flight 235 climbs out over the busy city of Taipei, the pilots start working through the after takeoff and initial climb checklists. But just seconds into performing these tasks, and when the plane is just at 1,200 feet (or 365 m) altitude, the pilots are startled by a master caution warning, which indicates there is an urgent situation unfolding onboard. They have just lost one of their two engines. And passengers who are frequent flyers of this route or the cabin crew onboard would have noticed something was wrong at this moment – they would have heard a sudden drop in sound coming from the engine.
Immediately, Captain Chien-tsung disengages autopilot and takes manual control. This situation means the pilots must return to the airport and land. While this is not a catastrophic situation by any means, it is a precarious situation – this is a twin engine, turboprop airplane, which means they will need to ensure that they can fly the plane level and watch their airspeed so as not to cause an upset. This should be standard operating procedure for most pilots who are trained for this very scenario. But the plane’s speed and rate of climb are dropping fast. Captain Tze-chung, who is the non-flying pilot and, in his role, must monitor the flight controls, warns Captain Chien-tsung, who is the pilot flying, to “watch the speed.”
TransAsia Airways Flight 235 Crashes into Keelung River Less Than Three Minutes After Takeoff
Now a stall warning sounds, and the control stick begins to shake, an indication they are flying too slowly to maintain lift. Just as they reach 1,630 feet (or 496 m) altitude, the plane begins to sink. But, if there is one ounce of good news, it is that they are less than a mile (or 1.6 km) from the airport. And yet, what’s in between the plane and the runway is a city full of people and tall skyscrapers. In fact, the pilot flying exclaims, “low terrain,” as they head back toward the airport. If this wasn’t confirmation enough, the pilot observing calls out, “you are too low!” And to make matters worse, the second engine has now also flamed out. We can only imagine the stress level these three pilots are experiencing right now.
The non-flying pilot declares a Mayday emergency to air traffic control (ATC). The plane, without engine power, is now banking dangerously to the right. Desperate, the pilots try and re-engage the autopilot two times, but it fails to reconnect. Flabbergasted, the pilot observing cries out, “how come it becomes like this,” meaning, how is this possible? Remember, this is a highly automated flying machine.
Now, just a mere 500 feet (or 150 m) above the streets of Taipei, the plane struggles to stay airborne. On either side of them are buildings, high rises, housing. The plane, crippled without engine power, now begins banking left in the direction of a bridge and the Huandong Viaduct, tilting from 10 degrees to an unimaginable 80 degrees. As it begins to turn almost all the way onto its left side, its underbelly now facing the car traffic on the bridge below, the aircraft’s left wing clips a taxi driving on the overpass. The wing then smashes into a fence and a light pole at the edge of the overpass. Less than three minutes after takeoff, the aircraft continues to bank to the left after those collisions, flipping all the way over, entering the Keelung River inverted, slicing through the surface of the water upon impact.
We talked about another flight that stalled and hit a passenger bridge way back in episode 1 of our podcast, Air Florida Flight 90, which stalled during takeoff, clipped a bridge full of stopped cars, and then dove into the icy Potomac River near Washington, D.C.
Rescuers Find Just 15 Survivors from TransAsia 235 Crash into Keelung River
Seeing that Flight 235 has gone missing from its radar, ATC immediately initiates emergency procedures and contacts search and rescue. According to the official rescue report, the first nine rescue vehicles arrive at the crash site within 15 minutes of the plane’s collision with the bridge. Rescuers also arrive by helicopter and by rubber boats. And they cannot believe their eyes: a group of 10 survivors are standing on one of the overturned wings. After helping the shivering and shocked passengers into boats and then onto the riverbank, the other rescuers begin to break apart the submerged fuselage and the rear service door at the plane’s tail section. To their amazement and absolute delight, five more people emerge from the dark cabin inside. But it is not only happy news. When rescuers enter the cabin, it is dark and inundated with the smell of fuel. They use explosion-proof lights as they make their way through the aisle, now almost covered up to their necks by river water. And then their hearts sink. They can see that many, many passengers were unable to escape – they are still sitting in their seats with their seat belts fastened, suspended upside down under water, their feet and legs floating on the water’s surface.
This is the worst aviation accident ever witnessed by the city of Taipei. By midday of the day of the crash, about a dozen relatives of the crash victims arrive at the riverbank to perform traditional mourning rituals. Accompanied by Buddhist monks ringing brass bells, they bowed toward the river and held out cloth inscriptions tied to pieces of bamboo meant to guide the spirits of the dead to rest.
Of the 58 people on board Flight 235, four crew members (including all three pilots and one flight attendant) and 39 passengers do not survive. The remaining 14 passengers and one flight attendant survive, but all have injuries ranging from head trauma and bone fractures to cuts and bruises. The taxi driver of the taxi on the bridge that the plane collied with sustained serious injuries, and the taxi passenger sustained minor injuries.
Survivability of TransAsia 235 Crash Came Down to Where People Sat and How Quickly They Regained Consciousness
All 15 survivors were seated after row 10. They later tell investigators that, after the aircraft impacted the water, the middle-aft (or back) section of the fuselage broke apart and rotated counterclockwise in an inverted position. The cabin environment became dark and was inundated by fuel odor as water rapidly poured into the cabin through the broken fuselage. Some of passengers were rendered unconscious immediately after impact and were upside down in the cabin restrained by their seatbelts. It was reported that the unconscious passengers then regained consciousness as they began to choke on the water that was engulfing the cabin. Those who stayed conscious were still in their seats and unbuckled their seat belts by themselves or were assisted by other passengers before the water covered their faces.
There was a break in the right side of the aircraft’s fuselage around rows 14 to 15. The survivors reported that they saw light from outside through this opening, and they decide to escape through this opening. Floating seats, luggage, and other debris get in their way, making it hard to escape quickly. But they do. A total of 10 survivors escape from this break in the fuselage and then make their way to standing on the aircraft wing awaiting rescue. There were five survivors seated closest to the aft (or back) cabin who escaped through the service door. One of the five survivors comforted and took care of other 4 survivors when waiting for rescue.
TransAsia 235 Survivors Share Harrowing Stories of Escape
Dr. Liu Chau-Hui was last to board Flight 235. He had wanted to get on an earlier flight home, so he moved up his boarding to Flight 235. After impact, he is briefly knocked unconscious. When he comes to, he is disoriented and does not immediately understand that the plane has just crashed into the river. In fact, he wonders, why is there water down where my shoes are? Inside the dark cabin, the water begins to rise quickly, and any survivor who is able to move has already unbuckled their seatbelts and are now running wildly toward the nearest escape route. In the distance, Dr. Chau-Hui can hear the sound of helicopter rotors and speed boats. He feels overcome with relief as first responders arrive on scene and immediately begin ripping pieces of the wreckage apart, pulling people out of the submerged airplane.
Taiwanese couple Lin Mingwei and Jiang Yuying were travelling on the plane with their two-year-old son, Lin Riyao. Lin Mingwei had changed seats from the left-hand side to the right before take-off because he was unsettled by a noise coming from the wing, something that might have saved their lives. He was seated near where the fuselage broke apart, so when the plane was submerged, he was able to get out and help his wife and son to scramble out of the opening.
Flight attendant Huangjing Ya was the only member of the flight’s crew who survived. Following the crash, she had to be taken to an intensive care unit here she was treated for her physical injuries but also for psychological trauma.
The crash of Flight 235 is the second fatal accident for TransAsia Airways in just the last seven months. In July 2014, Flight 222, also an ATR aircraft, had crashed, killing 48 of the 58 onboard. In a major twist of fate, Flight 235’s sole surviving crew member, Huangjing Ya, was also onboard that flight that crashed but survived that one as well.
Taiwan ASC Investigates TransAsia Flight 235 Crash, Rules Out Flight Control Problems
The Taiwan Aviation Safety Council (or ASC) is the agency that will lead the investigation. And amazingly, the ASC receives an important piece of evidence even before the wreckage is fully retrieved from the river. A second taxi driver who was on the bridge right as Flight 235 was banking into the river, caught the final moments of the flight, including its left banking, collision with the bridge, and then its continued descent toward the water. Rarely does this kind of witness evidence emerge in an air crash investigation. We have also linked to still photos of this video and to the video itself in the show notes for this episode. The global press also shares the dash cam footage of these final moments, and soon, the world is horrified by the images of the crash.
But investigators can glean important details from the video, including that the plane’s left engine seemed to be performing slowly, as indicated by the slow rotation of the propellors. They wonder if the crew experienced problems with this engine, or instead, if a left flap or aileron jammed after takeoff.
By noon on the day after the crash, investigators now have access to the entire wreckage, which has been pulled from the Keelung River and taken to a hangar. The ASC immediately rules out a flight control problem from the equation, as all the control surfaces, such as actuators or hydraulics systems, seem to have been working properly up to the moment of impact.
ASC Determines Both Engines on TransAsia Airways Flight 235 Were Working Normally
They next examine the left engine to determine if the engine caused the plane to bank left just before impact. But what they find is shocking – nothing is wrong with the engine. All parts were working properly and functioning all the way up to impact. Finding no clues within the left engine, they next examine the right engine, and here is where they find their first curious clue: the blades on the right engine are feathered despite the fact that the engine was fully functional.
We talked about feathering during Patreon episode 11, when we covered the VSS Enterprise spacecraft disaster. When a propellor is feathered, it is basically in its own failsafe position. On this aircraft, feathering happens when a propellor engine loses power in flight, the blades automatically rotate parallel to the airstream to reduce drag. This is all done to help maintain the plane’s climb performance. But this is odd because the right engine is feathered, and not the left engine, and the plane was banking left, indicating the left engine was the source of the issue. But now we know neither engine was failing prior to impact. Why was the right engine feathered and why did the plane bank dangerously to the left?
The ASC now has the data from the flight’s data recorder (or FDR) to analyze. The FDR proves that both engines were operating completely normally. However, the right engine torque, which measures the engine’s power to spin the propellors, is all over the place, fluctuating wildly. Investigators learn the plane’s feathering system includes an electronic torque sensor, which measures how much twisting force the right engine is producing. Low torque would indicate the engine has failed, which would then trigger the feathering system. But neither engine on Flight 235 ever failed. This leads investigators to wonder if the problem was not with the right engine but with the torque sensor itself. They examine the right engine’s torque sensor and discover microscopic faults within the circuit board of the sensor. This damage was enough to interrupt the signal that feeds into the torque sensor. On the right engine, the torque sensor could not detect any power even though the engine was working perfectly, and instead, caused the propellors to feather. But losing one engine should not have been a catastrophic event.
ASC Investigation Reveals Pilot Flying Shut Down Wrong Engine
Now, their second question: why was the plane banking to the left when the right propellors were feathered? According to the FDR, they can tell that while the left engine is operating normally, the throttle power is gradually being reduced to the left engine until it is shut off completely. This finding is chilling because there is only one way that could happen: it means one of the pilots manually shut down the power to this left engine. The throttle power settings are not automatic on the ATR aircraft – they can only be moved by hand. Why on earth would a pilot ever shut down a perfectly functioning engine?
Investigators get a much clearer picture of events once they listen to the cockpit voice recorder (or CVR) overlaid with the data from the FDR. At first, everything goes perfectly as the pilots work their checklists prior to takeoff. Then, the master warning light comes on, indicating that the right engine has flamed out (even though we know it was just a problem with the sensor). At this moment, the pilot flying disconnects the autopilot, which was not the right thing to do as the autopilot would help ensure in this case that power remained constant and steady to the remaining left engine, which is necessary to maintain climb performance especially at such a low altitude (remember, they are only right after takeoff and just 1200 feet above ground).
Even though the right engine is OK, the faulty sensor thinks the engine is failing which has created the warning. Now the pilots must complete an engine fail checklist for the right engine, which should be displayed on their display screens, and they can follow the resolution procedures step by step. But instead of doing that, the pilot flying does something unexplainable: he reduces engine power to the LEFT engine. The one remaining engine. Investigators can only deduce that the captain does not understand what the onboard flight computer is telling him about the true nature of the warning (which is about the right engine and not the left). This means the pilot flying has left them without engine thrust to either engine.
Crew Resource Management Problems Led to Confusion in TransAsia Airways Flight 235 Cockpit
But the pilot flying cannot simply just shut down an engine all by themself. Pilots are required to perform a cross-check with their co-pilot first, so that the non-flying pilot monitoring the flight can affirm the decision. But in this case, the pilot flying shut it down too quickly, without ever cross-checking this decision with the non-flying pilot. But to his credit, the non-flying pilot did say, “wait a second cross check”, but the pilot flying interrupted him by asking him for a new heading back to the airport. There was zero confirmation from the pilot flying about what the actual nature of the emergency was and there was never a cross check about the decision to reduce throttle to the left engine. The non-flying pilot is probably caught off guard and is unsure of what is happening right now.
And the most chilling part of what investigators hear as they listen back to the CVR is one of the last things that Captain Chien-tsung, the pilot flying, says, right before impact: “wow pulled back the wrong side throttle”. He has just realized he shut down the WRONG engine. The pilot flying keeps shouting to the co-pilot to restart the engines, but that was not possible at this point. He repeated that request over and over, seven times. But it was too late – they all knew what came next. From that time on, the aircraft entered an aerodynamic stall from which it never recovered.
TransAsia Flight 235 Crash Captain Had History of Performance Issues, According to ASC
The ASC dives into the backgrounds of all three pilots. What they uncover here is disturbing to say the least. They find that the pilot flying, Captain Chien-tsung, had a history of performance problems. He had failed a simulator test earlier in 2014 over emergency procedures including engine fires, loss of hydraulic systems, and flying on a single engine. After another training session, he passed a follow-up check a month later. But subsequent training in Singapore found that he had “insufficient knowledge leading to hesitations” during verbal tests about what to do during an engine shutdown on takeoff or loss of electronic engine controls, according to the report. Even with additional remedial training, he could not meet the airline’s pilot performance standards and requirements. What happened onboard Flight 235 was consistent with his performance weaknesses noted during his training. The ASC found that TransAsia Airways did not effectively address the evident and imminent flight safety risk that Captain Chien-tsung presented. Essentially, he never should have been flying with humans onboard his aircraft.
In another twist of irony, the ASC found that when the right engine flamed out, all the pilots would have needed to do was…nothing – literally. If they had just kept the plane flying on autopilot, they could have leveled off and then returned to the airport without any mishaps.
ASC Report Leads to Safety Recommendations while TransAsia Airways Shuts Down
There are a total of 25 findings from the ASC’s Final Report, and 16 safety recommendations issued to the related organizations, many of which were directed at TransAsia Airways, where it was revealed to have sloppy operations. According to the investigation report, when selecting eligible pilots for the position, the company did not follow its own rules and downgraded the quality of the pilots. Defects were also identified in TransAsia Airways’ training programs, leading inexperienced pilots to neglect their duties. After the crash, ten of 49 TransAsia Airways pilots failed emergency tests ordered by the Civil Aeronautics Administration of Taiwan after the crash.
However, the crash of Flight 235 spelled out the beginning of the end for TransAsia Airways. The airline ceased operations in November 2016, just one year and nine months after the fatal crash of Flight 235.
Unfortunately, looking back at the crash of Flight 235, many experts in the aviation industry say that this fatal accident was inevitable given how poorly the airline was run. However, this hindsight knowledge does nothing for the families of the 43 people who died that day. Instead, what they are left with is their loved ones’ final moments forever replaying over and over on repeat in a digital universe that seldom puts faces to names or stories behind numbers of fatalities. And this is, perhaps, the greatest tragedy of this crash.
And THAT is the tragic story of the crash of TransAsia Airways Flight 235.