By Faith Hung and Siva Govindasamy
TAIPEI/SINGAPORE (Reuters) - Pilots at Taiwan's TransAsia Airways are being tested on how they handle an engine failure and subsequent emergency, days after the fatal crash of one of the airline's ATR 72-600s, an official from the country's aviation regulator said.
Initial data from the flight recorders indicates the plane lost power in one engine just after take-off from Taipei's Songshan airport, Taiwan's Aviation Safety Council (ASC) said on Friday..
The crew then shut down the other engine, which was working, and attempted to restart it shortly before the aircraft crashed into a river killing at least 40 people.
Commercial aircraft can fly with just one working engine, and the authorities have not released any information from the recorders that indicates why the pilots shut down the working engine.
They said on Friday, however, that a combined loss of thrust caused the almost new aircraft to stall soon after take-off. The aircraft then lurched over buildings and banked sharply to the left before crashing upside down in the shallow river.
Officials in Taiwan and industry analysts say evidence presented so far raises questions over whether the crew may have accidentally cut the wrong engine.
"There must have been something wrong with what the crew did," said a Civil Aviation Authority (CAA) official, who did not want to be identified due to the sensitivity of the matter.
"It's a very big deal to turn off one engine after take- off. It needs to be double checked by the crew."
It was the second TransAsia ATR crash in seven months, and the fifth involving the airline since 1995, raising questions about safety standards at Taiwan's third largest carrier.
The CAA said the flight tests would only involve TransAsia's 71 ATR pilots, and not those who fly its Airbus aircraft. Pilots from China Airlines and EVA Air, Taiwan's two largest airlines, were not being tested.
The CAA official said the test results would be released on Wednesday.
The move has been questioned by Taiwan's pilots' union, which said crashes happen due to a combination of factors.
"The CAA and the ASC can't just jump to a conclusion like that," said Lee Ping-chung, secretary general of the union. "It could be mechanical, the weather, airline's management of pilots and how tired pilots are."
TransAsia said on Sunday it would cancel 52 flights Monday and Tuesday, in addition to the 90 already canceled following the crash.
Rescuers have recovered 40 bodies, with three still missing. Fifteen people survived.
A fuller preliminary report on the crash will be available in the next 30 days, with a final one expected in the next three to six months.
(This version of the story corrects spelling of TransAsia in the intro and removes extraneous word in penultimate para)