TransAsia plane crashed after faulty sensor, errors by pilots

A faulty connector sending inaccurate information and pilots mistakingly shutting down the wrong engine during a flameout led to the February crash of a TransAsia Airways Corp. plane, investigators said.

Flight GE235 had a connector that failed to send right information to the propeller plane’s computer systems, triggering an unnecessary automatic correction move, known as autofeather, according to a factual data report published by Taiwan’s Aviation Safety Council Thursday.

The ATR plane’s two pilots then followed a procedure that shut down the wrong engine, its executive director Thomas Wang said in Taipei.

“He called it wrong” when calling for shut down of engine 1, when engine 2 flameout procedure was displayed on screen in cockpit, Wang said.

“We didn’t see some procedures being followed,” he said.

The pilot in command of TransAsia Flight GE235 called for reduction in power to engine 1, five seconds after a master warning sounded, the Aviation Safety Council said in its factual report. Flight GE235 lost altitude, clipped an elevated highway and crashed into a nearby river minutes after takeoff from Taipei’s Songshan airport on Feb. 4, killing 43 people including the pilots. Some people survived the crash.

About 36 seconds after takeoff, the propeller-driven plane’s No. 2 engine autofeathered with the No. 1 engine being shut off 46 seconds after that, according to a preliminary report by the Aviation Safety Council published Feb. 17. The pilots discussed an engine flameout 35 seconds before making a Mayday call and subsequent crash three minutes and three seconds after takeoff.

Temporary grounding

Autofeather is a feature in propeller aircraft that automatically turns a propeller’s blades parallel to airflow, called feathering, to reduce drag.

The crash was the airline’s second fatal accident involving an ATR72 turboprop aircraft within a year. The first, in July 2014, killed 48 people.

While aviation authorities temporarily grounded all ATR aircraft in Taiwan for checks after the February crash and ordered retraining of TransAsia pilots, the airline won a delay of a new flight-safety rule introduced specifically for TransAsia after the July crash.

Logbooks for the aircraft that crashed Feb. 4, which were released publicly and reviewed by Bloomberg, showed that pilots didn’t meet new requirements to remain at the gate at least 30 minutes between flights to allow time to conduct safety checks.

A 20-minute turnaround earlier on the day of the crash didn’t necessarily breach the new rules because TransAsia had requested, and was granted, a delay in implementation of the regulation by two months, the Civil Aeronautics Administration said at the time.