Pilots fought frantically to keep Lion jet airborne

The pilots of the Boeing 737 that crashed off Indonesia last month struggled 26 times to stop the flight computer pulling the plane down after a recurring problem with crucial monitoring instruments.

A preliminary report by Indonesia’s national transport safety committee (NTSC) said that the plane was not airworthy on its previous flight and should not have been cleared to fly after earlier crews experienced similar problems.

The new Lion Air Boeing 737 Max 8 plunged into the Java Sea a month ago on a flight from Jakarta to Pangkal Pinang, killing all 189 passengers and crew.

The preliminary report does not assign responsibility for the crash but confirms that it occurred after faulty measurements of airflow by instruments mounted on the wings caused the computer to force the nose down to prevent what it mistakenly concluded was an imminent stall.

Flight data from one of the ‘‘black box’’ recorders shows that the two pilots tried repeatedly to correct the downward course in vain.

The same problem had been experienced by different pilots on the same aircraft the day before, when it flew to Jakarta from Denpasar in Bali. They solved the problem by overriding the automated systems and flying the aircraft manually.

The investigators have not yet discovered why the crew on the doomed flight did not do the same.