The US Federal Aviation Administration (US FAA) issued on August 3 a notice of proposed rulemaking for a Boeing 737 MAX airworthiness directive (AD), which proposes mandating a number of design changes to address an identified unsafe condition.

The proposed AD would require the following:

• Installation of new flight control computer software;
• Revision of the aircraft flight manual to incorporate new and revised flight crew procedures;
• Installation of new MAX display system software;
• Changing the horizontal stabiliser trim wire routing installations;
• Completing an angle of attack sensor system test;
• Performing an operational readiness flight.

In a notice on its website, the US FAA said the notice of proposed rulemaking will be open for a 45 day public comment period.

The FAA preliminarily determined that Boeing's proposed changes to the 737 MAX design, flight crew procedures and maintenance procedures effectively mitigate the aircraft-related safety issues that contributed to the Lion Air flight JT610 and Ethiopian Airlines flight ET302 accidents.

The FAA also preliminarily determined that the proposed design changes address additional safety concerns beyond those identified during the accident investigations.