Friday, November 09, 2018

Pilots of Lion Air plane that crashed may have been overwhelmed in seconds

The final moments of Lion Air Flight 610 as it hurtled soon after dawn from a calm Indonesian sky into the waters of the Java Sea would have been terrifying but swift.

The single-aisle Boeing aircraft, assembled in Washington State and delivered to Lion Air less than three months ago, appears to have plummeted nose-first into the water, its advanced jet engines racing the plane toward the waves at as much as 400 m.p.h. in less than a minute. The aircraft slammed into the sea with such force that some metal fittings aboard were reduced to powder, and the aircraft’s flight data recorder tore loose from its armored box, propelled into the muddy seabed.

While investigators have not yet concluded what caused Flight 610 to plunge into the sea, they know that in the days before the crash the plane had experienced repeated problems in some of the same systems that could have led the aircraft to go into a nose dive.

On Wednesday, the Federal Aviation Administration of the United States warned that erroneous data processed in the new, best-selling Max 8 jet could cause the plane to abruptly nose-dive. Investigators examining Flight 610 are trying to determine if that is what happened.

Boeing this week issued a global bulletin advising pilots to follow its operations manual in such cases. But to do so, experts said, would have required Flight 610’s captain, Bhavye Suneja, a 31-year-old Indian citizen, and his co-pilot, Harvino, a 41-year-old Indonesian, to have made decisions in seconds at a moment of near-certain panic.

They would have had to recognize that a problem with the readings on the cockpit display was causing the sudden descent. Then, according to the F.A.A., they would have had to grab physical control of the plane.

That would not have been a simple matter of pushing a button. Instead, pilots said, Captain Suneja could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength. Or he could have undertaken a four-step process to shut off power to electric motors in the aircraft’s tail that were wrongly causing the plane’s nose to pitch downward.'

All this would have needed to have happened within seconds — or the aircraft would be at serious risk of entering a death dive.

During the two days before Flight 610 began its final journey, there were repeated indications that pilots were being fed faulty data — perhaps from instruments measuring the speed and a key angle of the plane — that would have compromised their ability to fly safely.

Engineers tried to address the issue in at least three airports, Indonesian investigators said.

After the plane’s penultimate flight, for instance, technicians recorded in a maintenance log that they had fixed the pitot tubes, external probes on the airplane that measure relative airspeed. Earlier that day, on the resort island of Bali, engineers swapped out a sensor that measures the angle at which oncoming wind crosses the plane.

Called the angle of attack sensor, this instrument tells the pilot if the nose of the plane is too high, which could cause the aircraft to stall. In the Max 8, if the data indicates the nose is too high, the aircraft’s systems will automatically pull the nose down.

If the sensor data is wrong, the system could cause the plane to dive.

It is not yet certain if the airspeed sensors and angle of attack sensors malfunctioned on the final flight, or if the computers that process the information coming from the censors malfunctioned.

It is only with further analysis of data on the plane’s so-called black boxes, of which only one has been found, that the cause will be determined.

The Last Flight

When the 11th minute of Flight 610 began, the plane was still in nearly level flight at an altitude of about 5,000 feet. By the end of that minute, it had shattered into a kaleidoscope of pieces in the water, after hurtling earthward nose-first at perhaps 400 miles per hour, according to measurements from the Flightradar24 online data service.

What caused the aircraft to tip downward so sharply in that final minute is the greatest enigma. Over the past two days, investigators have been looking into whether it was a maintenance failure or a possible shortcoming in the Boeing 737 Max 8 that could affect other fleets operating the popular jet. Investigators also are exploring the possibility that the pilots were not adequately trained in how the plane differed from earlier models.

Older versions of the Boeing 737 have a reputation among pilots for being easy to adjust the angle of the plane’s nose should a problem arise, said John Cox, the former executive air safety chairman of the Air Line Pilots Association in the United States and now chief executive of Safety Operating Systems, a consulting firm.

But in the new version, Boeing introduced an emergency system that automatically corrects the nose angle to prevent the plane from stalling. In its safety bulletin, Boeing said the system could push the nose down for a full 10 seconds without the pilot’s authorization.

Boeing’s new system was intended to safeguard against what some studies have suggested is the most frequent cause of plane crashes — a stall.

But if the data fed into the system was inaccurate — which investigators are looking into — it could have theoretically caused the plane to pitch forward, presenting even the most experienced pilots with a difficult situation, said Peter Marosszeky, a longtime aircraft engineer and former senior executive at Qantas, the Australian air carrier.

“Training is everything in these situations, and experience is crucial,” he said.

The recommended response issued by Boeing and the F.A.A. this week would not be a pilot’s natural reaction. The flight crew is instructed to switch off the electricity powering stabilizers in the tail of the aircraft that are propelling the downward pitch of the nose.

But without specific training on this anomaly, what pilot would think to turn off part of the plane? When flight crews learn how to helm a new model of aircraft, they typically study the differences between older and newer models. Aviation experts worry that pilots at hard-driving carriers like Lion Air may not be given adequate time for such training.

In addition, differences between models sometimes manifest themselves only after months or years of operation. The Boeing Max 8 went into service just last year. Even though Captain Suneja was an experienced aviator for his age, he would not have had time to fully familiarize himself with the latest version of Boeing’s workhorse jet.

And with only seconds to wrestle the plane out of its fatal plunge, he never got that chance.
09/11/18 Hannah Beech & Keith Bradsher/New York Times

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