Indonesian Officials: Problems with Sensor Found on Crashed Jet

Updated at 4:32 p.m. on 2018-11-7

American plane maker Boeing has sent airlines an advisory after Indonesian transportation safety officials notified the company about a problem with a sensor on a Lion Air 737 Max 8 that crashed off West Java last week.

Boeing manufactures the Max 8 model, which first entered commercial service last year. But problems with a faulty sensor on the new Lion Air plane did not go away after it was discovered and fixed ahead of a flight the night before it crashed into the Java Sea, Indonesian officials said Wednesday.

The plane had shown erroneous inputs from one of its angle of attack (AOA) sensors during a flight from Bali to Jakarta on Oct. 28 that immediately preceded its doomed flight the next morning, officials said.

“There are indications that the replacement of the AOA did not resolve the problems, but may have instead worsened them,” Nurcahyo Utomo, an investigator with Indonesia’s National Transportation Safety Committee (KNKT), told a news conference in Jakarta on Wednesday. “Was it fatal? That’s what we are looking into.”

“It’s not only about the component but how it was installed,” he said. “Was it done correctly?”

Even though the faulty AOA sensor was replaced before the plane took off from Bali to Jakarta, the problem persisted during the Lion Air flight JT 610, Nurcahyo said.

The plane crashed minutes after taking off from Jakarta’s Soekarno-Hatta International Airport en route to Pangkal Pinang, in the Bangka-Belitung islands off Sumatra. The pilot had radioed the tower a request to return to the airport shortly before the jet crashed, officials said. All 189 people on board were presumably killed.

Boeing said the AOA is the angle between the oncoming air or relative wind and a reference line on the airplane or wing.

In response to the finding by Indonesian crash investigators, Boeing issued a bulletin “directing operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor,” said a statement posted on the company’s website.

Separately, the U.S. Federal Aviation Administration (FAA) sent out a statement saying it planned to issue an airworthiness directive in connection with Boeing’s bulletin.

“Boeing has released a Flight Crew Operations Manual Bulleting regarding the potential for erroneous angle of attack inputs on 737 Max aircraft,” the FAA said Wednesday in a message posted on Twitter.

“The FAA has alerted affected domestic carriers and foreign airworthiness authorities who oversee air carriers that use the 737 Max of the agency’s forthcoming action,” the agency added.

On its website, Boeing said the 737 Max is the company’s fastest-selling aircraft in its history. The aircraft maker said it had received 4,700 orders from 100 customers worldwide.

Nurcahyo, the Indonesian air crash investigator, said the manner in which the pilots responded to the problem on the Bali-Jakarta flight would be among recommendations submitted to Boeing and that would be shared with airlines, so other pilots could take similar action should such a situation arise again.

Indonesian investigators, who have been assisted by experts from Boeing and the U.S. National Transportation Safety Board (NTSB), previously said data from the aircraft’s recovered flight recorder had revealed speed indicator malfunctions on its last four flights.

Nurcahyo said KNKT had recommended actions to be taken by Boeing.

“The draft has been submitted and we have agreed to publish it immediately regarding the existence of a new procedure,” he said.

The replaced AOA sensor would also be sent to a factory in Chicago that manufactured the device for inspection, the Indonesian investigator said.

Weak signal

Meanwhile, search teams continued to scour the crash site in the Java Sea for the missing cockpit voice recorder (CVR), which records conversations between the pilots and air traffic control.

Nurcahyo said a ping signal had been detected but it was very weak.

“Probably because it is buried in thick mud,” he said.

The search has been complicated by the existence of an oil pipeline on the sea bed, officials said.

Muhammad Syaugi, the head of the National Search and Rescue Agency (Basarnas), said the search operation had been extended for another three days, and it would consist of 220 personnel from the agency, including 60 divers, as well as four ships.

At least 186 bags of body parts have been handed over to the police for identification, but only 44 victims of the crash have been identified,” said Asep Winardi, the head of disaster victim identification with Jakarta police.

Last week’s crash was the second deadly accident in 14 years involving a plane from budget carrier Lion Air.

In 2004, an MD-82 from its fleet overshot the runway of the airport in Solo, Central Java. It crashed into a cemetery, killing 25 people.

Nine years later, a Lion Air Boeing 737 carrying more than 100 people crashed into the sea while trying to land on Bali island, nearly splitting the fuselage into two. There were no fatalities.