JAKARTA, Indonesia – The last four flights of a crashed Lion Air jetliner all experienced problems with the new one
airspeed indicator, analysis of data from the flight data recorder recovered from the seabed Monday.
Soerjanto Tjahjono, head of the National Transport Safety Committee of Indonesia, said that researchers had come to the conclusion in the course of analyzing data from the memory unit of the recorder, one of the so-called black boxes of the aircraft.
The data of the recorder is considered crucial to understand the cause of the crash of October 29, the first with the Boeing 737 Max 8, the latest version of the single-aisle 737. All 189 people on board were killed. The aircraft was delivered to Lion Air, one of the largest low-cost airlines in Asia, in August.
Researcher Nurcahyo Utomo said that a team of experts tries to determine whether the error in the airspeed indicator was with a sensor, the computer system or the display. Researchers will question the pilots and technicians involved in the previous flights to see what actions they have taken to solve the problem.
The lethal crash of a Lion Air Boeing 737 aircraft in Indonesia is one of the worst aviation disasters of 2018. The WSJ looks at a number of big questions that have emerged as researchers try to find the cause of the crash. Photo: AP images
The analysis of 69 hours of flight data from the recorder started Monday and continues. Researchers said they had not concluded that the defective airspeed indicator was responsible for the crash. They added that they had not yet looked at the height and other information from the recorder.
Aeronautical pilots are routinely trained to deal with unreliable flight speed indicators and such defects are not in themselves regarded as an immediate danger to the safety of the flight. Typically, the reaction is to maintain thrust or increase slightly, while avoiding dramatic climbs or descents.
After the problem occurred last week on the Lion Air jet, the cockpit crew returned to manual flight and got permission from air traffic controllers to gradually go up about 2,500 feet to solve problems, according to US authorities and industry leaders who are familiar with the probe. The immediate response was consistent with general training expectations, according to these officers and independent safety experts.
But researchers are now concentrating on the reasons for a subsequent sudden high drop, said these people, followed by the fatal dive. The operation of another flight control system, called the angle attack indicator, can also be examined by the probe according to safety experts. Such devices are crucial for telling pilots how high or low the nose of an aircraft is. Angle or attack sensors work independently of air velocity sensors.
More generally, international accident investigations are also focused on the actions Lion Air's maintenance staff has taken in response to previous airspeed indications that ended in safe landings, including interactions between pilots and fitters, according to these people.
The maintenance logs can be important for finding the cause of the crash, said the US government and industry officials, because regulators and carriers that fly the same 737 variant have not exposed any pattern of defects or problematic airspeed indications.
The Indonesian authorities have suggested that they prefer the US Federal Aviation Administration or crash investigators of the National Transportation Safety Board to consider comprehensive inspections or new safety bulletins for pilots. However, such movements are considered unlikely unless information downloaded from the flight data recorder refers to more specific causes. On Monday, after the last revelations in Indonesia, FAA officials did not consider safety initiatives, according to a person familiar with the details.
Indonesian air traffic control lost contact with flight 610 at 6.33 pm, about 13 minutes after the take-off from Jakarta's main airport to the island of Bangka. Officials said the pilots had asked to return to Jakarta airport before they disappeared from the radar.
Data collected by Flightradar24, a flight monitoring network, indicate that the aircraft experienced possible erratic speed and altitude measurements on the flight that crashed and the previous flight, from Bali to Jakarta. Lion Air said that the jet on the previous flight had an unspecified "technical problem".
Possibly incorrect or misleading airspeed indications in the cockpit have already emerged as a first focus of safety experts concentrating on the crash, according to officials from the sector who follow the investigation.
The Chicago-based Boeing Co., which built the aircraft, has shown at least one airline operator and an external security expert interested in whether the pilots have received unreliable speed data, according to people familiar with the calls.
The Indonesian researchers said in a statement that they had asked Boeing and the US National Transportation Safety Board, both participating in the probe, to "take necessary actions to prevent similar accidents from happening again." This includes advising pilots on what to do if they encounter problems with the airspeed indicator, researchers told reporters.
A Boeing spokesman declined to comment. In a statement last week, it said it gave technical assistance to the probe and addressed questions to the Indonesian authorities. The NTSB did not have an immediate comment.
Boeing has orders for more than 3,000 of the 737 Max 8 jets and has delivered around 220 copies since the start of last year's flights.
The flight data recorder, repaired by divers at a depth of about 100 feet three days after the crash, has provided information on the last 19 flights of the crashed jet and contains about 1,800 data parameters.
Researchers are still trying to find the second black box, the cockpit voice recorder, which is thought to lie on the seabed under the mud. Mr. Utomo said the investigation teams had heard weak pings thought to have been broadcast by the recorder throughout the weekend.
The accident is the second worst Indonesian air disaster, after a
crash that killed 234 in September 1997.
The country has a long history of aviation accidents and the airlines have been limited in flying for security reasons to the US and Europe for years. The last restrictions for Indonesian airlines were lifted in June of this year.
-Robert Wall, Gaurav Raghuvanshi and Andy Pasztor contributed to this article.
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