The grounded Boeing 737 MAX fleet is destined to stay that way after the US Federal Aviation Administration indicated it could be several weeks before it receives final flight control software changes from the manufacturer.
Media reports had suggested the update could go for final approval as early as last week but the FAA said in a statement released Monday that it expected to receive the final software package “over the coming weeks”.
“Time is needed for additional work by Boeing as the result of an ongoing review of 737 MAX flight control system to ensure that Boeing has identified and appropriately addressed all pertinent issues,” the statement said.
“Upon receipt, the FAA will subject Boeing’s completed submission to a rigorous safety review,’’ the safety agency said.
“The FAA will not approve the software for installation until the agency is satisfied with the submission.’’
Boeing and the FAA are under intense scrutiny after the crash of two 737 MAX jets and the deaths of 346 people.
Several probes are underway into the certification of the aircraft type and regulatory agencies in Canada and Europe have indicated they will also be examining the software fixes independently.
The US manufacturer said it continued to work with the FAA and other regulatory agencies on the software update and training program.
“We are working to demonstrate that we have identified and appropriately addressed all certification requirements and will be submitting for FAA review once completed in the coming weeks,” Boeing said in a statement.
“Safety is our first priority, and we will take a thorough and methodical approach to the development and testing of the update to ensure we take the time to get it right.”
A preliminary report on the second crash involving an Ethiopian Airlines 737 MAX 8 on March 10 is believed to be imminent. Expectations it was due to be released Monday proved incorrect but the international convention is for the preliminary report to be released within 30 days of the crash.
That report should shed some light on speculation that a flight control law added to the 737 MAX to compensate for its bigger, repositioned engines was active at some stage in the second flight.
Quoting sources familiar with a high-level briefing to the US Federal Aviation Administration, The Wall Street Journal reported over the weekend that an emerging consensus among investigators was that the Manoeuvring Characteristics Augmentation System, or MCAS, was involved in both crashes.
Boeing was already working on changes to MCAS and pilot training when the second crash occurred and said last week it had complete confidence in the safety of its new software fix.\
READ Boeing has “complete confidence’ in MAX software fix.
MCAS activates in manual flight when the flaps are retracted and is part of the speed trim system that automatically commands changes to the horizontal stabilizer to trim the plane so there are no net forces on the control column.
Erroneous data from an angle of attack (AoA) sensor prompted MCAS to repeatedly push down the nose of aircraft in the Lion Air crash, something the pilots fought instead of deactivating the system. The angle of attack measures the position of the aircraft nose in relation to airflow.
The original version of MCAS took information from just one Angle of Attack sensor but there are two on the aircraft and the new version will compare inputs from both.
If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate and an indicator on the flight deck display will alert the pilots.
If MCAS activated in abnormal conditions, the new software will only provide one input for each elevated AoA event instead of resetting itself repeatedly.
It will also not be able to apply more force to the horizontal stabilizer than can be counteracted by the flight crew pulling back on the column.
Boeing is also making standard an AoA disagree alert that will tell the pilots if the two AOA sensors disagree by more than 10 degrees for more than 10 seconds.
“We’re going to do everything we can to ensure that accidents like these never happen again,’’ Boeing Commercial Airplanes vice product of product development Mike Sinnett told reporters last week.
“We are working with customers and regulators around the world to restore faith in the industry and to reaffirm our commitment to safety and to earning the trust of the flying public.”
