Similar to the United States National Transportation Safety Board (NTSB), France’s Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) has publicly issued its own comments regarding the recently published final report into the fatal Ethiopian Airlines Boeing 737 MAX crash. The Ethiopian Aircraft Investigation Bureau (AIB) published its findings on December 23, 2022.
Meanwhile, the NTSB publicly issued its own additional findings five days later, criticizing the Ethiopian investigators for omitting key details from the report, including the crew’s actions and wildlife activity at Bole International Airport (ADD) in Addis Ababa, Ethiopia. The BEA focused on pilots’ actions throughout the flight, something that was “insufficiently addressed in the EAIB final report, in particular with regard to the sequence of events that occurred before the activation of the 1st MCAS [Maneuvering Characteristics Augmentation System – ed. note],” the French investigators commented.
Focus on Ethiopian Airlines 737 MAX pilot actions
The BEA focused on the fact that it had found several shortcomings related to how the flight crew reacted to various alerts and the nose-down inputs from MCAS.
“Shortcomings relating to the crew’s actions, particularly in the first phase of the flight, is not accompanied by a thorough analysis of the reasons for the behaviors observed, in relation with their training, their experience and the company organization with regard to the training and knowledge acquisition principles,” the BEA noted in a statement prior to the bureau issuing its own comments.
According to the BEA, following the erroneous data from the left Angle of Attack (AoA) sensor, the left stick shaker – indicating an aerodynamic stall – activated on the flight. As such, the crew had to apply the Approach to Stall or Stall recovery procedure, which is a memory item described in Boeing’s Flight Crew Operating Manual (FCOM) and/or the Quick Reference Handbook (QRH). However, the pilots only proceeded to push the nose of the aircraft down, without disabling the autothrottle and insisting on activating the autopilot (A/P) system.
Much like the NTSB, the BEA reiterated that several analyses were performed by the manufacturer of the AoA sensor as to why the sensor failed, with data being handed over to the AIB. The Ethiopian investigation concluded that “production-related intermittent electrical/electronic failure involving the airplane’s Electrical Wiring Interconnection System (EWIS) and the AOA Sensor part” was to be blamed for the failure of the instrument. The NTSB concluded that a foreign object, most likely a bird, impacted the sensor upon take off.
Additionally, following the appearance of the Indicated Speed (IAS) and Altitude (ALT) DISAGREE alerts on both Primary Flight Displays (PFD), the pilots should have applied the Airspeed Unreliable Non-Normal Checklist. The first item on the checklist is to disable the autopilot, then the autothrottle, and to put the Flight Director (F/D) switches on the OFF position before setting a 10° pitch attitude and the engine thrust (N1) to 80%.
The French investigators concluded that the captain unsuccessfully tried to engage the A/P, did not turn off the autothrottle, and neither of the pilots acknowledged de IAS and ALT DISAGREE Alerts vocally, as nothing was heard on data from the Cockpit Voice Recorder (CVR).
But the Ethiopian Airlines Boeing 737 MAX captain was persistent in his attempts to active the A/P, doing so prematurely at 350 feet, despite the airline’s procedures requiring to wait at least until the aircraft reaches 500 feet of altitude.
“This premature action, although not appropriate in stick shaker conditions, may be symptomatic of a state of stress that had been rapidly developing following the activation of the stick shaker and Master Caution immediately after take-off,” the BEA commented.
Once the aircraft failed to reach the proper altitude, the pilot made another attempt, which failed, prompting him to loudly question “what’s going on?”, per the CVR data. The first officer did not respond to the question and the French investigators have suggested that no process of information acquisition, cross-check or crew decision-making followed the second failed attempt to activate the A/P.
Finally, on the third attempt at 1,000 feet, the autopilot finally engaged. But because the pilots chose a speed that was above the maximum operating limit speed (VMO/MMO), the autopilot trimmed the 737 MAX’s nose down to accelerate and after being on for 33 seconds, the A/P disconnected.
“The lack of thrust reduction aggravated the difficulties encountered by the crew to control the aircraft throughout the remainder of the flight,” the BEA noted. Furthermore, the French authority pointed out that “coordination and the communication between the captain and the F/O [First Officer – ed. note] was very limited and insufficient”, and that the pilots’ ability to be aware of the situation and solve various issues throughout the flight were “deeply impacted”. Moreover, the relatively low flight experience of the F/O could have contributed to the lack of proactivity and CVR’s transcripts showing that he was startled from the very moment that the stick shaker triggered.
Other issues apart from the MCAS
While the Ethiopian AIB identified the erroneous activation of MCAS as the probable cause of the crash, both the NTSB and BEA sees the crew’s actions as another causing factor.
While the captain applied a nine-second electric trim input upon the second nose-down maneuver by MCAS, it was not enough to counter the first and second MCAS activations. Thus, the aircraft was never fully trimmed for the remainder of the flight. When the aircraft’s speed exceeded the VMO, pilots heard the overspeed warning and expressed their surprise, the BEA noted, which “may indicate that after retracting the flaps, the crew lost track of the IAS values”. The autothrottle was still on.
“During this phase, the physical efforts applied by the crew on the column probably impacted their situational awareness and their cognitive resources and did not allow them to undertake the proper actions,” the French investigators said.
As a result, the BEA would add “the crew’s inadequate actions and the insufficient Cockpit Resource Management (CRM)”, as one of the probable causes of the fatal accident that claimed the lives of 157 people onboard the 737 MAX.
The French authorities would also add five contributing factors, including the crew’s failure to apply the Approach to Stall or Stall Recovery Maneuver and the Airspeed Unreliable Non-Normal Check-list, the captain’s persistent attempts to activate the A/P, insufficient electric trim usage, and the failure to reduce the thrust of the engines.
Finally, the BEA also pointed out that the current Ethiopian Airlines Logipad system to spread information about new operational procedures and/or systems does not evaluate the crews’ understanding and knowledge acquisition about the new procedures and/or systems.
“This system was used to disseminate the information related to the MCAS system issued following the previous 737 Max accident and did not allow the airline to ensure that the crews had read and correctly understood this information,” the BEA concluded.