Plane’s descent speed over 500kph, data shows

JAKARTA: The Indonesian airliner that crashed in waters near Jakarta was plunging at hundreds of kilometres an hour in its final seconds, according to preliminary data transmitted by the plane that could aid investigators looking for a cause.

Lion Air Flight JT610, a nearly new Boeing 737 Max jet, went down from 1,479m at altitude in just 21 seconds, according to data compiled by FlightRadar24, a flight-tracking system.

The plane was carrying 189 people and all are feared dead.

A routine descent for an airliner would be about 450m to 610m per minute, said John Cox, the president of the consulting company Safety Operating Systems who participated in numerous crash probes.

The final data point obtained by FlightRadar24 showed the plane descending at 9,441m per minute, meaning it was moving downward at about 563kph.

Such speeds are typical of midrange flight speeds, but unheard of for a descent.

“This thing really comes unglued,” Cox said. “The numbers are barely believable.”

FlightRadar24’s track of the flight raises as many questions as it answers.

It shows the plane rising and climbing repeatedly with the speed also varying, both of which aren’t typical on the latest, computer-driven aircraft.

Multiple failures involving the crew and equipment on the plane are possible explanations, from an erroneous speed indication to some sort of electronic failure.

Shortly after take-off from Jakarta, one of the plane’s pilots requested permission to return to the airport, indicating the crew may have been struggling with some type of failure.

The limited and sometimes contradictory information about the flight doesn’t obviously match any previous accidents, making it difficult to narrow down the possible cause, said Steve Wallace, the former head of accident investigations at the US Federal Aviation Administration.

“I have no ‘most likely’ scenario in my head for this accident,” Wallace said.

Cox said the data – which are generated by the plane’s own systems and transmitted to ground stations – should be approached with caution at this early stage of the investigation.

For example, even in cases when planes plunge to the ground, the descent speed isn’t typically as high as the Lion Air readings, he said. — The Jakarta Post/Asia News Network