Indonesian transport authorities said Wednesday they have advised that airline pilots flying Boeing 737 MAX 8 planes carry out certain procedures devised by a Indonesian pilot to cope with any air speed indicator malfunction.
National Transportation Committee chief Soerjanto Tjahjono told reporters that the recommendation was submitted to Boeing Co. in the wake of the last week's crash of Lion Air Flight 610, which plunged into the Java Sea claiming the lives of all 189 people on board.
Earlier, data downloaded from the plane's flight data recorder, which was recovered from the seabed, showed that it experienced air speed indicator problems during its ill-fated flight on Oct. 29 and three previous flights.
The three previous flights were from Bali to Jakarta on Oct. 28, from the North Sulawesi provincial capital of Manado to Bali on that same day and from Bali to Manado on Oct. 27.
The committee's investigator Nurcahyo Utomo told reporters that after the Manado-Bali flight, a technician in Bali detected a problem with an angle of attack (AOA) indicator, which offers a visual indication of the amount of lift the wing is generating at a given airspeed or angle of bank.
"The technician decided to replace the left AOA and cleared the plane to fly to Jakarta," Nurcahyo said, referring to the Bali-Jakarta flight that was delayed for almost 16 hours.
Despite the replacement, that flight piloted by Capt. William Martinus experienced the same problem, and it "was apparently getting bigger."
The left AOA indicator on the pilot's side was 20 degrees higher than the right AOA indicator on his copilot's side, Soerjanto explained.
The pilot, however, "carried out some procedures and finally could overcome the problem and the plane could safely land in Jakarta," he said.
"The success of the (Bali-Jakarta) pilot to fly the problematic plane became the reason of the National Transportation Safety Committee to provide recommendations to Boeing for airlines around the world on what to do when their Boeing 737 MAX 8 aircraft suffer a similar problem," he added.
In an aircraft flight and maintenance logbook, a copy of which was seen by Kyodo News, the pilot wrote that "IAS (indicated air speed) and ALT (altitude) disagree shown."
According to FlightRadar24, after taking off late Sunday and reaching an altitude of 480 meters, the Bali-Jakarta flight dropped to 410 meters in 20 seconds. After increasing its speed to 453 kilometers per hour, the plane was able to reach an altitude of 1,700 meters before dropping back to 1,400 meters in 25 seconds.
A similar case was seen in the data of Flight JT610 before it crashed shortly after taking off from Jakarta. It had been bound for Pangkalpinang on Bangka Island, off southeastern Sumatra.
Investigators, Soerjanto said, have interviewed pilots and cabin crew in three flights before Flight JT610, as well as technicians in Manado, Bali and Jakarta to verify what has been shown by the flight data recorder.
Efforts to find the other so-called "black box" containing the plane's cockpit voice recorder continued Wednesday with more equipment to be deployed Thursday.
National Search and Rescue Agency chief Vice Marshal Muhammad Syaugi also said the search of the plane's debris and bodies will be extended for another three days starting Thursday.
As of Wednesday afternoon, a total of 51 victims have been identified from the remains of their bodies, mostly based on DNA samples.