Ethiopia’s Aircraft Accident Investigation Bureau today released a preliminary accident investigation report into the March 10 crash of Ethiopian Airlines Flight 302 shortly after takeoff from Addis Ababa on a scheduled flight to Nairobi, Kenya. All 157 passengers and crew on board the Boeing 737 MAX 8 aircraft were killed in the crash.
The report contains a fight history based on preliminary analysis of the airplane’s digital flight data recorder (DFDR) and cockpit voice recorder and air traffic control (ATC) communications. In their initial findings, investigators found that shortly after takeoff, the value of the left angle of attack (AOA) sensor deviated from the right one, with the left AOA sensor reaching 74.5 degrees while the right sensor indicated 15.3 degrees. The stick shaker activated shortly thereafter. The flight crew twice reported flight control problems.
According to the report, the DFDR recorded an automatic aircraft nose down (AND) trim command four times without pilot input. The DFDR data also indicated the flight crew utilized the electric manual trim to counter the automatic AND input, and that the crew performed the runaway stabilizer checklist, put the stabilizer trim cutout switch to cutout position and confirmed the manual trim operation was not working.
Information in the preliminary report is subject to change as the investigation continues.
Following release of the report, Boeing issued a statement and then followed up with a recorded message from Dennis Muilenburg, chairman, president and CEO. In his message, Muilenburg says in part: “The full details of what happened in the two accidents [Lion Air Flight 610 and Ethiopian Flight 302] will be issued by the government authorities in the final reports, but, with the release of the preliminary report of the Ethiopian Airlines Flight 302 accident investigation, it’s apparent that in both flights the Maneuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information.
“The history of our industry shows most accidents are caused by a chain of events. This again is the case here, and we know we can break one of those chain links in these two accidents. As pilots have told us, erroneous activation of the MCAS function can add to what is already a high workload environment. It’s our responsibility to eliminate this risk. We own it and we know how to do it.”
Muilenburg said Boeing is “working to finalize and implement a software update that will ensure accidents like that of Lion Air Flight 610 and Ethiopian Airlines Flight 302 never happen again. … We’re nearing completion and anticipate its certification and implementation on the 737 MAX fleet worldwide in the weeks ahead.”
The two Boeing statements can be found here.