FAA is pressing on with planned changes to Boeing 737 MAX aircraft stemming from the October 2 Lion Air Flight JT610 accident, but has not seen any evidence from Sunday’s Ethiopian Airlines’ MAX 8 crash to take additional steps, such as a fleet-wide grounding.

Everyone onboard each aircraft was killed in the two crashes.

"Following the accident of an Ethiopian Airlines Boeing Model 737-8 airplane on March 10, 2019, the National Transportation Safety Board (NTSB) as the accredited representative, and the FAA as technical advisors, are supporting the Ethiopian Accident Investigation Bureau," FAA said in a March 11 continued airworthiness notification.

"FAA has dispatched personnel to support the investigative authorities in determining the circumstances of this event. All data will be closely examined during this investigation, and the FAA will take appropriate action if the data indicates the need to do so."

Multiple operators and two regulators, the Civil Aviation Administration of China and the Indonesian Directorate General of Civil Aviation, have taken the unusual step of proactively grounding aircraft until more is known about the Ethiopian accident, Flight ET302. That has placed about one-third of the delivered 350 MAX-family aircraft, including MAX 8s and MAX 9s, out of service.

FAA's notification emphasized actions taken after JT610, which went down in the Java Sea shortly after takeoff as its crew battled with, among other issues, erroneous data from angle-of-attack (AOA) sensors.

Among them: plans advanced by Boeing to modify the MAX's maneuvering characteristics augmentation system (MCAS), a flight-control law added to the MAX family to prevent stall.

MCAS provides automatic nose-down inputs to assist pilots in certain manual, flaps-up flying scenarios, especially at slow airspeeds and high angle of attacks (AOA). The MAX's larger CFM LEAP-1B engines compared to the 737NG's CFM56-7B create lift at high AOAs. MCAS was added as a certification requirement to help mitigate this.

Sean Broderick, sean.broderick@aviationweek.com