AILSA CHANG, HOST:
Now to Indonesia where authorities say the jetliner that crashed last month into the Java Sea had experienced similar problems the day before and was not airworthy. That's one of the findings in a preliminary report released today by Indonesia's National Transportation Safety Committee. And that report sheds new light on the 13 minutes of chaos in the air. NPR's David Schaper reports.
DAVID SCHAPER, BYLINE: Imagine you're in the cockpit flying a commercial airline with 188 other people on board when you get into a tug of war with the heavily automated machine you're flying. Investigators say that appears to be what happened on October 29 when the Lion Air Boeing 737 MAX plane took off from Jakarta.
PETER LEMME: As soon as the wheels left the ground and the airplane became airborne, the captain, the person in the left seat, their column, the wheel that they're holding to fly the airplane, started to shake.
SCHAPER: Peter Lemme is an aerospace engineer.
LEMME: There is a device on board called a stick shaker, and its purpose is to alert the pilot that they're impending a stall, that they're flying much too slowly.
SCHAPER: But that wasn't the case at all. The copilot was not getting those indications, and the plane was flying normally. But the warning was troubling. So 90 seconds into the flight, the pilot radioed air traffic control to check air speed and altitude. Investigators say a sensor that indicates a plane's pitch malfunctioned, telling onboard computers that the nose was pointed up much higher than it actually was. That led an automated flight control system to take over and point the nose down, corrective action that wasn't needed. So Lemme says the pilot fought to regain control.
LEMME: In short order, they started to get into a cycle of the airplane pitching down and the pilot pitching it back up again. And this about every 15 seconds would repeat.
SCHAPER: That back-and-forth cycle happened more than two dozen times through almost the entire 13 minutes of the flight. Former Boeing safety engineer Todd Curtis says the pilots could have turned off the system and manually flown it. In fact, that's what another pilot did the day before on the very same plane. But on the day of the crash...
TODD CURTIS: That apparently wasn't done, and they were literally fighting the control system throughout the flight trying to keep the airplane's nose up while the system was trying to point the nose down.
SCHAPER: Experts say it appears the pilots may have been confused about the new flight control system in the 737 MAX and did not know how to disengage it. Since the crash, other pilots have criticized Boeing for not providing enough detail and training, a charge Boeing denies. The cockpit voice recorder, which has not yet been found, could help investigators answer more questions. But crash investigators say the faulty sensor was a recurring problem and after being replaced still malfunctioned the day before the crash. Indonesian authorities say this plane was not airworthy, and Lion Air, which experts say has a checkered safety record, should have grounded it. Todd Curtis agrees.
CURTIS: And, again, it doesn't say that that problem led to the crash, but, clearly, whether it did or did not, that airplane shouldn't have been flying.
SCHAPER: The preliminary report calls for improved maintenance procedures and more pilot training. Lion Air indicates it will comply with those recommendations. David Schaper, NPR News.
(SOUNDBITE OF DAVID HOLMES' "STORY OF THE INK") Transcript provided by NPR, Copyright NPR.