Indonesian authorities released a preliminary report regarding their findings into the crash of Lion Air Flight 610. As mentioned in prior posts, early reports indicated that accident investigators were focusing on the aircraft’s new Maneuvering Characteristics Augmentation System (M.C.A.S.) which is an automated system designed to prevent the aircraft from entering an aerodynamic stall. The preliminary report confirmed that this was the investigators’ focus, although the report stated that it was still too early to identify a specific cause for the crash.
Analysis of the aircraft’s Digital Flight Data Recorder (DFDR) demonstrated that the flight crew struggled with the aircraft immediately upon take-off. The data indicated that the aircraft began to experience “stick shaker” activation on the Captain’s control column immediately after take-off. Stick shaker is an automatic system that causes the pilot’s control yoke to vibrate indicating that the aircraft is about to enter an aerodynamic stall. Apparently, a faulty Angle of Attack sensor was providing inaccurate information to the aircraft’s automated stall protection system, including the M.C.A.S., indicating that the nose of the aircraft was too high. As a result, the M.C.A.S. activated causing the aircraft to automatically push the nose downward to prevent what it falsely believed to be the onset of an aerodynamic stall.
During the 11 minute flight, the flight crew attempted on approximately 26 occasions to correct the nose down attitude of the aircraft caused by the activation of the M.C.A.S. Each time the aircraft automatically lowered its nose, the flight crew countered attempting to lift the nose of the aircraft. However, the pilot’s nose up control inputs were not strong enough to override the aircraft’s automatic response to what it erroneously believed was the beginnings of an aerodynamic stall. Tragically, the flight crew ultimately lost this battle and the aircraft entered a step dive into the Java Sea at approximately 450 miles per hour.
The Preliminary Report also indicated that the aircraft experienced a similar problem on the day prior to the crash but that flight crew was able to disable the automatic stall protection system in-flight. As a result the aircraft had undergone maintenance the night prior to the crash in an attempt to correct the problem.
Authorities continue to search for the aircraft’s Cockpit Voice Recorder which will provide investigators with crucial information as to what the flight crew was saying to one another as they attempted to correct the automatic nose down forces. We will continue to provide updates as more information becomes available.