As the Boeing 737 MAX 8 planes face airspace bans across the world due to safety fears following two deadly crashes, more news has emerged of pilots struggling to control the aircraft.
Pilots on at least two US flights reported autopilot systems in use on the 737 MAX 8 seemed to cause their planes to tilt downwards and lose altitude suddenly.
The pilot reports were filed last year in a database compiled by Nasa. They are voluntary safety reports and do not publicly reveal the names of pilots, the airlines or the location of the incidents.
In one of the incidents the plane’s captain said immediately after putting the plane on autopilot, the co-pilot called out “Descending,” and there followed by an audio cockpit warning: “Don’t sink, don’t sink!”
The captain immediately disconnected the autopilot and resumed climbing.
“With the concerns with the MAX 8 nose down stuff, we both thought it appropriate to bring it to your attention,” the captain wrote in the report. “Best guess from me is airspeed fluctuation”, which he said could have been due to a weather system overwhelming the plane’s automation.
On another flight, the co-pilot said seconds after engaging the autopilot, the nose of the aircraft tipped downward and the plane began descending at 1,200 to 1,500 feet (365 to 460 metres) a minute.
As in the other flight, the plane’s low-altitude-warning system issued an audio warning. The captain disconnected the autopilot, and the plane began to climb.
In the second incident the co-pilot said he could not “think of any reason the aircraft would pitch nose-down so aggressively.”
But in both incidents the reports said the issue did not appear to be related to the new automated anti-stall system suspected of contributing to the Lion Air crash in Indonesia in October 2018 in which 189 people were killed.
In that crash, data indicates the pilots also struggled with repeated nose-down commands from the plane before it crashed into the Java Sea,
However, the anti-stall system only activates if the autopilot is turned off, according to Boeing.
Three days ago an Ethiopian Airlines flight crashed six minutes after takeoff killing 157 people. The cause of the crash it not yet known.
Additional reporting by AP