BA Boeing Co

CANBERRA, Australia—Investigators believe debris found off Tanzania in June offers the best new clue to the final moments of Malaysia Airlines Flight 370, including whether it was under pilot control.

The Australian Transport Safety Bureau, which has spent weeks studying the piece—a main flap from a Boeing 777, which experts say is "highly likely" to be from Flight 370—aims to complete its analysis in around two weeks. Its conclusions will be part of a broader report to be reviewed by experts, including from Boeing Co., before being released to the public.

Investigators continue to seek answers to one of the world's biggest aviation mysteries even as governments prepare to suspend the search after months spent scouring the floor of the southern Indian Ocean failed to find any trace of the plane. Flight 370 vanished from radar en route to Beijing from Kuala Lumpur on March 8, 2014, with 239 people on board.

Authorities have long believed the plane wasn't under human control at the time of its apparent crash, based on communications between the aircraft and an Inmarsat PLC satellite. That communications data—central to fixing on a 120,000 square-kilometer search area, more than 90% of which has now been covered—suggest Flight 370 was plummeting at a rate of at least 12,000 feet a minute when it entered the water.

However, another theory—that the plane was in a controlled glide following a loss of engine power—hasn't been ruled out, though authorities consider it less likely. While either theory would lead to largely the same search area, the edges would vary; a simulation shows the aircraft, starting from 40,000 feet, could have gone an extra 140 miles if under control.

Peter Foley, program director for the Operational Search for Flight 370 at the ATSB, said the main flap is particularly significant because damage analysis may determine how it broke off the plane. Unlike other parts recovered so far, such as the flaperon found on Ré union Island and being examined in France, the main flap is deployed manually.

"It has to be deployed by a human, from the cockpit," Mr. Foley said in an interview. "And you have to have hydraulic power to do so."

The flap, its honeycomb interior clearly visible, now sits on an office desk in a room at the ATSB's Canberra headquarters that resembles an ordinary garage more than a sterile laboratory. Among the clues being sought by investigators: impact marks where hydraulic actuator arms were situated—which Mr. Foley said would help determine whether they were in a normal housed position or deployed at impact—and damage to the material within the flap, which could indicate the speed and angle of the aircraft as it hit the water.

"The good thing about engineering is that it's generally pretty conclusive, it's either one way or it's not that way," Mr. Foley said. "The evidence points you in a direction."

A recent analysis by Australian defense scientists of burst frequency signals from Flight 370 to satellites indicated the aircraft had been descending fast, likely in an automated series of swooping dives called fugoids. The high speed points away from a gliding descent under pilot control, Mr. Foley said.

"So in a sense, quite recently, it put a line under our thinking in terms of alternate scenarios," he said.

While analysis of the main flap may provide a strong indicator about what happened when the plane entered the water, it offers fewer clues about Flight 370's whereabouts. Australian ocean current modeling has showed some debris could have drifted thousands of miles west toward Africa from the search area.

Mr. Foley said the flap analysis would be passed to the governments of Australia, Malaysia and China to decide whether it justifies extending the search, which the three countries said on July 22 would be suspended if the current area doesn't yield results.

"Governments are at the point where they need us to present them with some fairly compelling evidence of where that aircraft is before they are going to extend the search," said Mr. Foley. "We're working harder to find that crucial piece of evidence. We need something that is going to give us something pretty conclusive about what happened at the end of the flight, where that aircraft impacted the sea."

Authorities haven't drawn firm conclusions around why the flight veered sharply off its intended flight path, turning hard to the west and then flying steadily south toward a remote corner of the Indian Ocean.

"Unfortunately, this is not an exact science," Australian Transport Minister Darren Chester said in an interview. "We are pushing the boundaries of aviation research and analysis, and in many ways we are pushing the boundaries of human endeavor to search one of the most inhospitable places on the planet, in water six kilometers deep."

"The fact that we are doing additional drift modeling and continuing to analyze satellite modeling, and revisit all the evidence and data, is an indication that we are not giving up on this search," he said.

Write to Rob Taylor at rob.taylor@wsj.com and David Winning at david.winning@wsj.com

(END) Dow Jones Newswires

August 12, 2016 02:25 ET (06:25 GMT)

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