MIAMI – The FAA has issued a notice of proposed rulemaking (NPRM). Its purpose is to supersede the previous Airworthiness Directive (AD) applying to Boeing 737 MAX airplanes.
Since the issuing of the 2018 AD, the agency has determined final corrective action for the aircraft to once again take flight. These actions are necessary to address the MAX’s unsafe condition.
List of Boeing 737 MAX Corrective Actions
The proposed AD would require Boeing to:
- Install new flight control computer (FCC) software
- Revise the existing Airplane Flight Manual (AFM) to incorporate new and revised flight Crew procedures.
- Install a new MAX display system (MDS) software.
- Change the horizontal stabilizer trim wire routing installations.
- Complete an angle of attack sensor system test.
- Perform an operational readiness flight.
According to the NPRM, the proposed AD would also apply to a narrower set of aircraft than the superseded AD.
It would also allow operation (dispatch) of an airplane with certain inoperative systems. However, it would do so only if the operator’s existing FAA-approved minimum equipment list (MEL) includes certain provisions.
Results from The Investigation
On October 29, 2018, a Boeing 737-8 operated by Lion Air (JT) -Flight 610- was involved in an accident. It occurred after takeoff from Soekarno-Hatta International Airport (CGK) in Jakarta, Indonesia, resulting in 189 fatalities.
Indonesia’s Komite Nasional Keselamatan Transportasi (KNKT)) completed the investigation. It had the assistance of the National Transportation Safety Board (NTSB), the US FAA, the manufacturer, and the operator.
Reports from the accident investigation indicate that the airplane’s flight
control system generated repeated airplane nose-down horizontal stabilizer trim commands that contributed to the accident.
Data from the flight data recorder indicated that a single erroneously high angle of attack (AOA) sensor input to the flight control system (while the flaps are retracted) can cause repeated airplane nose-down trim of the horizontal stabilizer and multiple flight deck effects.
Featured image: Boeing 737 MAX-9. Photo: Boeing