Thanks to the Transasia Airways ATR flight data recorder (FDR), we know a little more about what happened during the tragic events that took place a week ago in Taipei, and several questions arise.
37 seconds after take-off, the right turboprop engine was recorded as being in idle mode.
A critical situation ?
No, having only one of the two engines operating in this phase of a flight is certainly delicate, but does not prevent the ascent of an airplane, as in this case. Thanks to its still functioning left engine, it rose an additional 135 metres (440 feet).
What is the procedure ?
In the case of engine failure, the procedure manual defines precisely what must be carried out (Memory Item). The pilot at the controls should reduce the power output of the faulty motor by activating one of two Power Levers. The other pilot, in manipulating the Condition Levers feathers the propeller to prevent it from slowing the aircraft, and then shuts off the fuel supply. Finally, the fire switch of the failed engine, has to be activated in order to completely isolate it. This procedure seems to have been respected by the Transasia pilots, although on the wrong engine - the still functioning left.
Did the crew have any reason to cut the left engine ?
No. In such cases, there is no justification for cutting the only operating engine. In this stressful situation, the pilots may have misidentified the non-functioning engine; in any case the left engine was switched off, and maximum power applied to the non-functioning right. It was at this point that the crew transmitted a distress call: "Mayday", an anglicised phonetic transcription of the French "M’aider" (help me !), repeated three times.
42 seconds after voluntary extinction, perhaps upon realizing their mistake, the pilots restarted the left engine. At that time the aircraft had been gliding for 1 minute and 15 seconds, then it stalled, and crashed.
The toll of Flight GE235 crash victims has risen. The crash has so far killed 40 people, and three passengers are still missing.