Crashed jet was ‘not airworthy’

PROBE: IT SHOULD HAVE BEEN GROUNDED DAY BEFORE

Anti-stall system procedure also not included in operating manual of new 737.

Jakarta

ALion Air jet that crashed into the sea off Indonesia last month was not in an airworthy condition on its second-to-last flight, when pilots experienced similar problems to those on its doomed last journey, investigators say.

In a preliminary report, Indonesia’s transport safety committee (KNKT) focused on the airline’s maintenance practices and pilot training and a Boeing anti-stall system, but did not give a cause for the October 29 crash that killed all 189 people on board.

KNKT investigator Nurcahyo Utomo said the agency had not determined if the anti-stall system, which was not explained to pilots in manuals, was a contributing factor. The report unveiled fresh details of efforts by pilots to steady the 737 MAX jet as they reported a “flight control problem”.

Contact with the jet was lost 13 minutes after it took off from Jakarta. Information retrieved from the flight data recorder showed the “stick shaker” was vibrating the controls, warning of a stall throughout most of the flight. The captain was using his controls to bring the plane’s nose up, but an automated anti-stall system was pushing it down.

“It’s very distracting and unnerving,” former Boeing flight control engineer Peter Lemme said of the stick shaker activation.

Pilots flying the same plane a day earlier had experienced a similar problem until they shut off the system and used manual controls to fly, KNKT said. “This is considered as unairworthy condition” and the flight should have been “discontinued”. The pilots of that flight reported problems to the maintenance team, which checked the aircraft and cleared it for take-off the next day.

Boeing, which has said procedures for preventing an anti-stall system activating by accident were in place, said pilots of the penultimate flight had used that drill but the report did not say if pilots on the doomed flight did so.

Boeing did not refer to a revised anti-stall system introduced on the 737 MAX which US pilots and Indonesian investigators said was missing from the operating manual. Boeing said the procedure to deal with a runaway stabiliser, under which anti-stall systems push the nose down when the plane is not entering a stall, had not changed between earlier version of the 737 and the 737 MAX.

But pilots said the control column behaves differently in some conditions, which could confuse pilots who have flown the earlier model. – Reuters