Nov. 7 (UPI) -- Faulty sensors made it difficult for the pilots of Lion Air Flight 610 to determine how fast they were flying, crash investigators and Boeing said.
Investigators are trying to pin down the cause of the plane's crash off Indonesia last week. It involved a new Boeing 737 MAX 8 that was just a few months old, a model for which Boeing is now issuing a safety bulletin.
Boeing on Tuesday issued a bulletin directing flight crews to update their procedures when there's erroneous input from an angle of attack sensor. The equipment provides data on the angle at which wind passes over the airplane's wings. A false reading could cause a plane to go into a steep dive.
Flight 610 crashed Oct. 29 into the Java Sea after departing Indonesia. All 189 people aboard are presumed dead.
The Boeing 737 MAX is designed to automatically go into a dive if a stall is detected, which is the standard tactic to recover and maintain flight. A faulty reading from one of the sensors could trick the plane's computerized flight systems into thinking it's in a stall, experts said.
Investigators said Tuesday the plane experienced airspeed sensor problems on its last four flights.
Boeing's updated procedure Tuesday tells pilots to counter such a scenario by deactivating the stabilizer system.
"The investigation into Lion Air flight 610 is ongoing and Boeing continues to cooperate fully and provide technical assistance at the request and under the direction of authorities investigating the accident," the bulletin states.
The same plane went into a deep dive on a flight the day before the crash, according to passengers and data from a flight-tracking website.
Investigators have determined the plane hit the water while still intact and with both engines running. It may have been traveling up to 600 mph in its dive.