The FAA has proposed a number of design changes to the Boeing 737 Max as a result of investigations into the problems that caused two fatal crashes and led to the aircraft’s grounding.
The global fleet of 737 Max aircraft has been grounded since March 2019 after two 737 Max crashes during 2018 in Ethiopia and Indonesia, which killed 157 and 189 people respectively.
Subsequent investigations identified problems with the 737 Max’s manoeuvring characteristics augmentation system (MCAS) as the main cause of the crashes. The MCAS, which was added to the 737 because of the heavier engines used in the Max version, automatically compensates when it senses the aircraft is stalling by turning the nose of the plane down and incorrectly operated when the crashes occurred.
Boeing has been working with the FAA to return the aircraft to service since it was grounded 18 months ago and is now targeting early 2021 for this. Earlier this week a key milestone in this process was achieved when the US regulator sent a notice of proposed rulemaking (NPRM) for a Boeing 737 MAX airworthiness directive (AD) to the Office of the Federal Register for publication.
An AD is a notice for owners and operators of an aircraft about technical corrections for safety problems that must be carried out before an aircraft can fly that issued by regulators. The changes also have to be carried out to aircraft that are on the production line or on order.
The NPRM proposes a list of design changes to address problems with the 737 Max. Once the NPRM is published in the Federal Register, a 45 day public comment period will begin.
The changes proposed by the FAA to the 737 Max include modifications to the flight control software, a revision of crew procedures and the rerouting of internal wiring.
The NPRM states: “This proposed AD would require installing new flight control computer software, revising the existing Airplane Flight Manual to incorporate new and revised flightcrew procedures, installing new Max display system software, changing the horizontal stabilizer trim wire routing installations, completing an angle of attack sensor system test, and performing an operational readiness flight.”
The FAA also published a preliminary report into the 737 Max “to assist in understanding of how the agency identified and is addressing the safety issues affecting the 737 MAX”.
