Jakarta. The Lion Air jet that crashed into the Java Sea northeast of Jakarta last month was not in an airworthy condition even on its second-last flight, when pilots experienced similar problems to those on its doomed last journey, investigators said on Wednesday.
In a preliminary report, the National Transportation Safety Committee (KNKT) focused on the airline's maintenance practices and pilot training and a Boeing anti-stall system but did not give a cause for the crash that killed all 189 people on board.
The report unveiled fresh details of efforts by pilots to steady the 737 MAX 8 jet as they reported a "flight control problem," including the captain's last words to air traffic control asking to be cleared to "five thou" or 5,000 feet.
Contact with the jet was lost 13 minutes after it took off from Soekarno-Hatta International Airport in Tangerang, Banten, heading north to Pangkal Pinang in Bangka Belitung.
Information retrieved from the flight data recorder showed the "stick shaker" was vibrating the captain's controls warning of a stall throughout most of the flight. The captain was using his controls to bring the airline's nose up, but an automated anti-stall system was pushing it down.
Pilots flying the same plane a day earlier had experienced a similar problem, en route from Denpasar, Bali, to Jakarta, until they used switches to shut off the system and used manual controls to fly and stabilize the plane, the KNKT said.
"The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight," the report said. "This condition is considered as un-airworthy condition" and the flight should have been "discontinued."
The pilots of that flight reported problems to Lion Air's maintenance team, which checked the jet and cleared it for takeoff on the doomed flight JT-610 the next morning.
After the crash, Lion Air instructed pilots to provide a "full comprehensive description" of technical defects to the engineering team, the KNKT said.
In a statement, Boeing drew attention in detail to a list of airline maintenance actions set out in the report but stopped short of blaming ground workers or pilots for the accident.
The company, which has said procedures for preventing an anti-stall system activating by accident were already in place, said pilots of the previous flight had used that drill but noted the report did not say if pilots of the doomed flight did so.
Boeing's statement did not make any reference to a revised anti-stall system introduced on the 737 MAX, which US pilots and Indonesian investigators say was missing from the operating manual.
Boeing says the procedure for dealing with a so-called runaway stabilizer, under which anti-stall systems push the nose down even when the plane is not entering a stall or losing lift, had not changed between the earlier version of the 737 and the newly delivered 737 MAX.
However, pilots say the control column behaves differently in certain conditions, which could confuse pilots who have flown the earlier model.
Lion Air chief executive Edward Sirait said he had not yet read the KNKT report but would comply with all the investigators' recommendations.
The report provided new recommendations to Lion Air on safety on top of earlier recommendations about the flight manual that have already been implemented by Boeing.
'Too Early'Nurcahyo Utomo, an investigator at KNKT, said on Wednesday that it was too early to say whether issues with an updated Boeing 737 anti-stall system contributed to the crash.
He said the agency had not yet determined if the anti-stall system, which was not explained to pilots in manuals, was a contributing factor.
"We still don't know yet, if it contributed or not," he said in response to a question at a briefing. "It is too early to conclude for now."
KNKT head Soerjanto Tjahjono said on Wednesday that the committee held meetings with victims' families in Jakarta and Pangkal Pinang.
A family member of one of the victims told local media the information provided was "disappointing," with much of it already in the public domain.
The Lion Air crash is the world's first involving the 737 MAX jet, a fuel-efficient version of Boeing's workhorse narrow-body introduced into service globally last year.