LION AIR FLIGHT 610
On October 29, 2018, Lion Air Flight 610 crashed into the Java Sea, 12 minutes after takeoff from Jakarta-Soekarno-Hatta International Airport, Indonesia, killing all 189 people on board. The accident site was located 18 nautical miles off the coast of the island of Java. It was the first major accident involving the new Boeing 737 MAX series aircraft. The aircraft involved, was a Boeing 737 MAX 8, registered as PK-LQP. The aircraft was delivered new to Lion Air on August 13, 2018. At the time of the accident, the aircraft had flown about 800 hours in service.
The Flight 610 was a scheduled domestic flight from Soekarno-Hatta International Airport in Jakarta to Depati Amir Airport in Pangkal Pinang. The aircraft took off from Jakarta in a westward direction, before circling around to a northeast heading, which it held until crashing offshore northeast of Jakarta. During takeoff, the flight data recorder recorded a difference between left and right angle of attack, of about 20 degrees, which continued until the end of the recording. During rotation of the aircraft, the left control column stick shaker activated, and continued for most of the flight. After the flaps were retracted, the flight data recorder recorded automatic aircraft nose down trim for 10 seconds, followed by flight crew commanded aircraft nose up trim. Automatic nose down trim briefly stopped, when the flaps were temporarily extended to 5. In their communications with air traffic control, the flight crew asked the controller to confirm the altitude of the aircraft, and later also asked the speed as shown on the controller radar display. The co-pilot reported experiencing a flight control problem, and that they were flying the aircraft manually. The flight crew had requested clearance to return to the Jakarta airport 19 nautical miles into the flight. Last radio contact was when the captain requested the arrival controller to block altitude 3000 feet above and below, for traffic avoidance. The controller asked what altitude the pilot wanted, to which the captain responded "five thou". The controller approved the pilot request. The flight data recorder stopped recording within twenty seconds of the pilot's response, as the aircraft impacted the sea.
The CFM International LEAP engines of the Boeing 737 MAX have a higher bypass ratio, and have a larger nacelle than the engines of previous 737 models, so the engines are placed higher and further forward in relation to the wing, than on previous models. This destabilises the aircraft pitch at higher angles of attack. To deal with this, Boeing designed a Maneuvering Characteristics Augmentation System for the 737 MAX series. This feature was added to prevent the aircraft from entering a stall under specific conditions. The logic behind the automatic nosedown trim lies in that system. Former Boeing engineers expressed the opinion, that a nose down command triggered by a sensor single point of failure, is a design flaw. A malfunction in the angle of attack sensors could lead the Maneuvering Characteristics Augmentation System to believe, that the aircraft is stalling, when it isn't, causing it to dip the aircraft's nose to recover from a non-existent stall even in level flight.
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