Lion Air is a commercial operating aviation brand which takes up the skies in Indonesia. A Boeing 737 MAX 8 manufactured by the United States which is also the fastest selling plane aroung the globe. On October 28th 2018, An usual journey began from the Jakarta Airport to Bali. There were 189 people on board. A 70 Minute’s journey turned the fate of the people, 15 minutes after take off, the flight crashed into the Java sea and all people on-board had the last breath.
What caused this ?
The New Boeing 737 Max 8 had the new Anti – stall system called the MCAS ( Maneuvering Characteristics Augmentation System ) , angle of attack sensor basically which sends the information to cockpit at which angle the aircraft is flying and prevent the flight from stall event by initiating the plane’s pitch nose down without any input from the pilot. Right after the B737 Max8 take off, the captains control column began to shake as a stall warning, and for the next 13 minutes there has been an indication of nose down & up 26 times which would have been a terrifying experience. An AOA giving out erroneous data can lead to incorrect speed readings, potentially causing confusion among the flight crew and a rapid loss of altitude. The captain’s side gave an erroneous reading of 20 degree difference from the first officer. As the Pilot had struggles in controlling the Aircraft, had requested to return to the nearest airport to the Air Traffic Controller. The pilots managed to pull the nose back up over and over until finally losing control, leaving the plane, Lion Air Flight 610, to plummet into the ocean at 450 miles per hour, killing all 189 people on board.
For a simple understanding of this above graph, let’s start with the 3rd line from top of the graph(Green colored) As we move towards the right side of green line graph, we see small purple line with box like structure, which indicates the aircraft’s nose down movement due to faulty reading from the sensor. While the first line from the top, typically shows the pilots deseperately counteract by pulling the nose up. Let’s come to the 5th line where one can see a red and green line relatively having the same graph shape representing (RED – Left AOA sensor, Green – Right AOA sensor). Unfortunately if we take a look onto the scale value indicated on the left side, red is higher than zero in most of the time and it caused the erroneous wrong angle input to the pilot’s cockpit while the right side sensor is functioning properly. Coming to the last line, one can see a blue line, that indicates the altitude which rises up first, and plunges down further in last indicating the last few moments of the aircraft before crashing into the Java sea.
The Post event analysis:
An AOA ( Angle of Attack ) had been changed by mechanics on the ground in Bali the day before the crash, after similar problems occurred on previous flights, Indonesia’s National Transportation Safety Committee said. The directives prompted several of the biggest US pilots’ unions to say this was the first time they were hearing about the new flight system which majority of the pilots did not know such system existed in the brand new 737 max 8. After this incident , the Boeing Company came up with an immediate Air-Worthiness DIrective on November 6th 2018 indicating the prevention of this repetitive uncommanded nose down cycle can be avoided if the stabilizer trim system is deactivated by use of both TRIM CUTOUT switches.