Divers Zero In on Black Boxes From Indonesia Plane Crash



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BANGKOK — Enticed by faint pings from the seafloor, Indonesian investigators have determined the general location of the data recorders that will be crucial in discovering what caused the crash of Lion Air Flight 610, one of the deadliest commercial air disasters in years, officials said on Wednesday.

Divers were zeroing in on the so-called black boxes in the muddy waters of the Java Sea, but strong currents hampered the search, said Air Chief Marshal Hadi Tjahjanto, Indonesia’s armed forces chief.

Based on signals from locator beacons attached to the recorders, a 50-strong team of divers was searching a watery square about 11.5 miles on a side northeast of the capital, Jakarta, said Soerjanto Tjahjono, the head of the National Transportation Safety Committee.

“There is a 70 percent likelihood that we will find the black boxes,” said Mr. Soerjanto, whose committee is leading the investigation in a country plagued by aviation mishaps. “The other 30 percent will be our prayers.”

“From our data, accidents in Indonesia are still mainly caused by human factors,” Mr. Soerjanto said. “For technical problems, there are very few. But we still don’t know about this accident.”

Indonesian aviation experts, who examined what they said was the maintenance log from the flight from Bali to Jakarta on Sunday, said the plane had experienced problems with unreliable airspeed readings. While it is difficult to guess what might have caused the crash without the black boxes, aviation experts have raised the possibility that problems with the delicate instruments that gauge speed and altitude could have contributed to the tragedy.

A variety of malfunctions or oversights could lead to inaccurate speed and altitude projections, including electrical glitches or obstructions to the monitoring instruments affixed to the outside of the plane. Part of what is called the pitot-static system, the external probes send three sets of measurements to the flight crew, and any discrepancy between readings is cause for concern, aviation experts said.

Lion Air technicians cleared the flight for takeoff on Monday, and checked the pitot tubes on the outside of the plane, according to the maintenance log viewed by Indonesian aviation analysts. The tubes can be compromised by invading insects or by ice forming during a flight, among other rare complications.

Peter Marosszeky, a longtime aircraft engineer and former senior executive at Qantas, said that while a full investigation of Flight 610’s final hours is needed, the initial evidence is consistent with problems with the pitot tubes. These tubes are particularly vulnerable in hot, equatorial climates like Indonesia’s to being blocked by wasps, he said.

“It’s very hard to see because the wasps go inside the tube and make a mud nest in there,” said Mr. Marosszeky, who is now the managing director of Aerospace Developments, a research and consulting company in Sydney.

In 2013, an Etihad flight that had been on the ground for little more than two hours in Brisbane, Australia, experienced a faulty airspeed reading during takeoff. Australian transport safety investigators later found that wasps had managed to build a nest in a pitot tube during the brief stopover.

“It’s imperative when you park the aircraft that you cover the pitot tubes,” Mr. Marosszeky said.

But the covers also need to be removed before a plane takes off for the tubes to work in flight. In July, a Malaysia Airlines flight left Brisbane, with all three covers still on the probes.

John Goglia, a former board member of the United States National Transportation Safety Board, said that because the pitot tubes of Flight 610 had reportedly been checked during the maintenance that took place hours before Monday’s fated takeoff, investigators will want to know exactly what was done to them.

“Given the fact that the aircraft had a previous problem, one of the first places to check is whether there was the possibility that a mistake was made” in maintenance, he said.

The proper functioning of the tubes could also have been affected if the systems connected to them were touched during maintenance, Mr. Goglia added.

The tubes are covered when a specialized box is attached to them to carry out a safety check, Mr. Goglia said. Again, the instruments must be unsheathed before the plane is flown again.

It is ultimately the pilot’s responsibility to ensure that the covers are off the pitot tubes, aviation experts said. Normally, pilots are supposed to walk around the plane before takeoff and run through a safety checklist, they said.

Given that the flight on Monday morning left before 6:30, this walk-around would most likely have happened before dawn.

“I always carry a strong torch and an extra battery with me to make sure I see things clearly in the dark,” said Budi Soehardi, an Indonesian pilot with 40 years’ experience flying with various carriers, including Garuda Indonesia and Singapore Airlines. “I’m not sure if everyone does that.”

It would have been standard procedure for Bhavye Suneja, the 31-year-old Indian captain of Flight 610, to be shown the maintenance log from the previous night’s flight that recorded the problem with unreliable airspeed.

The 737 Max 8 entered service last year, and the plane involved in Monday’s crash was delivered to Lion Air in August. It was owned by CMIG Aviation Capital, an aircraft leasing company that is a subsidiary of China Minsheng Investment Group, the company confirmed.

It also would have been customary for Mr. Suneja, who had flown with Lion Air for seven years, to have received training before taking the helm of the new model, to learn how it differed from previous versions of the workhorse 737 jet.

But veteran aviators said that what is less common, particularly among low-cost carriers, is for pilots to receive refresher courses on what to do if the flight faces unexpected difficulties, like inaccurate flight data.

Because planes are now so heavily computerized, basic skills like flying a plane without the aid of technology has become a less common art, pilots said.

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