Officials Release Preliminary Report on Crash of Lion Air 610

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On October 29, 2018, Lion Air Flight 610 crashed into the Java Sea while on an early morning flight from Jakarta to Pangkal Pinang.  The crash of the Boeing 737 MAX resulted in the loss in 189 people. Over the course of the past month, there has been plenty of finger pointing between Lion Air, Indonesian authorities, and the aircraft manufacturer, Boeing.  I did not provide any updates about the back and forth between the entities because I wanted to provide the facts.  Today, the Indonesian National Transportation Safety Commission released a preliminary report about the crash.

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The entire 78 page report can be found here or here..  The report has a ton of information so I will try my best to summarize it.

What We Know

  • On October 28, prior to the flight from Denpasar to Jakarta, the pilot’s Angle of Attack (AoA) sensor was replaced (AoA sensors measure the angle of the aircraft’s nose relative to incoming air).  The aircraft was deemed airworthy by maintenance.
  • On takeoff, the pilot noticed that his airspeed and altitude instruments differed significantly from the co-pilot’s. He checked both flight displays, cross checked with a standby instrument, and determined that his side was the problem.  The aircraft started to perform an automatic trim (part of the safety system of all 737 MAX aircraft to recover from a stall when on autopilot) which was stopped only when the pilot performed a STAB TRIM cutout (overriding the autopilot system). The copilot manually flew the aircraft to Jakarta without incident.
  • Once on the ground in Jakarta, maintenance was informed of the incident and began troubleshooting. A flush of the pitot and static data modules and a cleaning of the elevator feel connector were performed.  The aircraft was deemed airworthy.
  • On October 29, the pilot’s and copilot’s AoA sensors showed a difference of 20 degrees after takeoff, according to the recovered Flight Data Recorder (FDR).
  • The pilots asked air traffic controllers for assistance when they could not determine the speed or altitude of their aircraft. Soon after, the pilots reported a flight control problem.
  • Automatic trim began, as it had on the previous night, and continued until the FDR stopped recording approximately 12 minutes after takeoff.

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From this report, it is obvious that the pilots on the last two flights reacted to the problem in different ways.  On the second to last flight, the pilots overrode the system, while the pilots did not on the fatal flight.  Additionally, the maintenance action performed prior to the last flight seemed to be lackluster.  The mechanic, in my opinion, did not address the AoA issue at all.

Final Word

This report does not offer a definitive answer as to what specifically went wrong on the fatal flight. It does, however, offer more insight into the minutes prior to the crash.  I will continue to provide updates as they become available.

tip of the hat to Flightradar24. 

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