As divers approached the underwater area where they expected to find the black boxes of Indonesia’s Sriwijaya Air jet that crashed into the sea, it became clear their task wasn’t going to be easy.
The site was strewn with sharp debris from the shattered Boeing aircraft, posing a danger to them. Some pieces were too heavy to dislodge with lifting balloons, which are usually used to surface smaller parts. A navy vessel with a crane was called.
Searchers are struggling to find and reach the devices that are critical to uncovering how and why the plane—a 26-year-old Boeing 737-500 that Sriwijaya Air says was in good condition before the flight—went down minutes after it took off from the capital, Jakarta, on Saturday, carrying 62 people.
Both the flight-data and cockpit-voice recorders—the so-called black boxes—are critical to understanding what occurred aboard SJ182 before the crash. Flight-data recorders typically collect information ranging from basic speed and altitude to flight-control inputs by the crew, while voice recorders capture sounds and conversations from the cockpit. Together, they can help investigators determine the accident’s cause. “We hope we can have an idea of what happened in the flight,” said Nurcahyo Utomo, head of aviation investigations for Indonesia’s national transport safety committee. “That’s basically what we expect from these black boxes.”
It isn’t unusual for the search for black boxes to take time after a plane crashes into the sea. Authorities said Sunday that they detected pings from the boxes—an emergency feature intended to help recover the devices after an accident. Divers dispatched to seek out the recorders were equipped with direction finders to pinpoint their location more precisely, the chief of the country’s search and rescue agency, Bagus Puruhito, said.
The devices are designed to withstand harsh conditions. Black boxes from an Air France jet that crashed in 2009 were found nearly two years later at a depth of almost 12,900 feet. After a Lion Air jet crashed in 2018, also in the Java Sea, authorities found the memory unit from one of the plane’s two black boxes within days of the accident that killed 189 people. But it took 2½ months to retrieve the cockpit-voice recorder.
The Boeing aircraft involved in the 2018 accident was the 737 MAX, the newest version of the company’s single-aisle jet family, which was grounded nearly two years ago following the Indonesia crash and another one in Ethiopia in 2019. The Sriwijaya Air jet that plunged into the water Saturday is an older model that doesn’t use the flight-control system largely blamed in the two 737 MAX crashes.
Among the questions investigators have is why the aircraft made an unexpected shift in direction shortly after taking off, flying northwest, which prompted air-traffic control to ask the plane to report its direction. The aircraft disappeared from the radar seconds later.
Stormy weather that afternoon had delayed takeoff, another factor investigators are probing. The plane departed at 2:36 p.m. local time on Saturday, climbing to a maximum altitude of 10,900 feet about four minutes later and then beginning a steep descent, according to aviation data provider Flightradar24. Authorities said they didn’t receive a distress call.
“Based on what we have, there was no declaration from the pilot that they have a problem, or any report that they have an abnormality,” Mr. Utomo of the transport safety committee said. “Based on the pilot communication with the traffic control, everything looks normal.”
Geoff Dell, an air safety investigator based in Queensland, Australia, said what is known already—that the plane changed course shortly after takeoff and went down quickly—still leaves many questions unanswered.
“There are any number of possibilities, but the recorders will give clues,” he said.
If the recorders on this aircraft were the original installation set, they would contain data about hundreds of flight parameters that would tell investigators whether the plane was flown into the water deliberately, if decompression in the cabin was a factor, or if the aircraft was behaving unusually in any way, Mr. Dell said.
“You can put it into a computer program that translates all that data into something that’s really easy to read, so you get a real-time playback and you can see it all unfold,” he said.
The flight’s 54-year-old pilot Afwan was a former Indonesian air-force pilot with years of experience flying older versions of Boeing aircraft like the 737-500, a spokeswoman for Sriwijaya Air said. His record was “very positive,” the spokeswoman said.
Mr. Afwan’s co-pilot was Diego Mamahit, who had worked for seven years at Sriwijaya Air, most recently as a senior first officer, and flew all around the Indonesian archipelago, according to his profile on professional networking site LinkedIn. “I really love to fly and enjoy my duties to operate Boeing 737 aircraft to all domestic route in Indonesia,” his profile reads.
The crash comes as the Covid-19 pandemic has battered the airline industry around the world. In Indonesia, the transport ministry suspended most flights in late April and gradually resumed some air travel in early May. Asia-based aviation industry experts said domestic travel has since stabilized at around 50% of pre-pandemic flight frequency.
Some aviation experts worry that the lower frequency of air travel during the pandemic could impact pilot practice or aircraft flightworthiness. Planes grounded in Indonesia might also require especially stringent maintenance inspections due to the country’s tropical climate which could speed the rate of corrosion, said Shukor Yusof, the founder of Malaysia-based aviation consulting firm Endau Analytics.
A spokeswoman for Sriwijaya Air said the airline hired specialized firms for aircraft maintenance, but didn’t respond to requests for comment on what maintenance the aircraft that crashed had undergone before the flight. She also didn’t comment on whether the pilots of SJ182 had been flying regularly in recent months.
Rama Noya, vice president of the Indonesian Pilot Association and a Sriwijaya pilot, said although pilots’ flying hours had been roughly cut in half due to reduced flights during the pandemic, Sriwijaya pilots were still flying around 40 to 50 hours a month, including planes that were used for cargo transport. He thought those hours were enough to keep them sharp. “This is sufficient,” he said.
Throughout the day, search-and-rescue crews pulled out human remains from the sea. Srie Rahayu, a 38-year-old resident of a Jakarta outskirt, whose cousin and four other relatives were on board, said she hopes search crews can recover the bodies.
This article originally appeared on Wall Street Journal