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The 320 page final report on the crash of Lion Air 610 by the Indonesian aviation authority, the Komite Nasional Keselamatan Transportasi (KNKT), was released on October 25, 2019 and is lengthy, thorough and well-written.  It contains accurate recitation of facts, analyses of the accident flight, the certification process, pilot training, and information not provided to pilots, and faulty airline and contractor maintenance practices.  No one in the accident chain is left out from this investigative body’s thorough review—nor should they be.  

This Lion Air 610 crash is a classic example of multiple factors, acts and omissions lining up to produce a tragic result.  One cannot read the report, however, without the inevitable take-away that had Boeing and the FAA done their jobs correctly, the errors that occurred downstream might not have caused the crash.

Many of the Report’s conclusions echo the recommendations of the Joint Authorities Technical Review (JATR) released on October 11, 2019, and discussed in a previous article on this site. Selected conclusions are reported below with comments where appropriate:

3.   Uncommanded MCAS function was considered Major during the FHA. Boeing reasoned that such a failure could be countered by using elevator alone. This lower level designation meant that Boeing did NOT have to perform Failure Modes and Effects Analysis (FEMA) would have been able to identify single-point and latent failures which have significant effects as in the case of MCAS design. It also provides significant insight into means for detecting identified failures, flight crew impact on resolution of failure effect, maintenance impact on isolation of failure and corresponding restitution of system. 

Several conclusions focused on the differences between what Boeing assumed would be the flight crew’s response and the actual response of the flight crew:

7.  During the accident and previous LNI043 flights, the flight crew initially responded by pulling back on the control column, however, they did not consistently trim out the resulting column forces as had been assumed. As a result the Boeing assumption was different from the flight crew behavior in responding to MCAS activation. 

12.  During the accident flight, multiple alerts and indications occurred which increased flight crew’s workload. This obscured the problem and the flight crew could not arrive at a solution during the initial or subsequent automatic aircraft nosedown stabilizer trim inputs, such as performing the runaway stabilizer procedure or continuing to use electric trim to reduce column forces and maintain level flight. 

13.  The MCAS software uses input from a single AOA sensor only. Certain failures or anomalies of the AOA sensor corresponding to the master FCC controlling STS can generate an unintended activation of MCAS. Anticipated flight crew response including aircraft nose up (ANU) electric trim commands (which reset MCAS) may cause the flight crew difficultly in controlling the aircraft. 

Redundancy Not Considered in Design

19.  The MCAS architecture with redundant AOA inputs for MCAS could have been considered but was not required based on the FHA (Functional Hazardous Assessment) classification of Major. 

Excessive Control Forces

21. The DFDR data indicated that during the last phase of the flight, the aircraft descended and could not be controlled. Column forces exceeded 100 pounds, which is more than the 75-pound limit set by the regulation (14 CFR 25.143). 

Lack of Training Requirements and Confusing Cockpit Indications

30. Flight crew training would have supported the recognition of abnormal situations and appropriate flight crew action. Boeing did not provide information and additional training requirements for the 737-8 (MAX) since the condition was considered similar to previous 737 models. 

35. 14 FAR 25.671 (c) requires that probable malfunctions of the flight control system must be capable of being readily counteracted by the flight crew. This necessitates that normal flight crew should be able to readily identify problems and respond quickly to mitigate them. However, during the accident flight multiple alerts and indications concealed the actual problem and made it difficult for the flight crew to understand and mitigate it. 

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