The grounding continues

The latest on the Boeing 737 MAX grounding. Mark Broadbent reports

THE GROUNDING of the Boeing 737 MAX continues, with the return to commercial operations for the aircraft looking highly unlikely for some time yet.

The 737 MAX has been grounded since March after the crash of Ethiopian Airlines Flight 302 earlier that month, the second disaster to involve the 737 MAX 8 after the October 2018 crash of Lion Air Flight 610 off Indonesia. The two crashes killed a total of 346 people.

The focus for the investigations into these accidents is the aircraft’s Manoeuvring Characteristics Augmentation System (MCAS), a flight control law designed to enhance pitch stability by activating in manual flight, automatically trimming the horizontal stabilisers on the tail upwards when the system’s angle of attack (AOA) sensors determines the upward pitch of the aircraft might become too steep.

Boeing says it has developed a software update for the system to provide “additional layers of protection if the AOA sensors provide erroneous data”.

More software issues

In May, Boeing completed development of updated MCAS software, including associated simulator testing and engineering test flights. The Federal Aviation Administration (FAA) then held a full-day meeting with representatives from 33 global regulatory bodies to discuss the process for bringing the 737 MAX back into service.

Test pilots from the regulators were hosted by Boeing in mid- June to test out the software in the company’s engineering flight simulator to review specific flight conditions and scenarios. However, those simulator sessions identified an additional issue with the 737 MAX’s software. An FAA statement said the agency had, “found a potential risk that Boeing must mitigate”.

Neither Boeing nor the FAA gave specific information about the “potential risk”, with Boeing Chief Executive Officer Dennis Muilenburg describing the issue in a video message posted on Twitter in late June as, “an additional flight condition we must address to reduce pilot workload”.

Widespread media reports, however, say the risk is related to a flaw in data processing aff ecting stabiliser trim and specifically ‘trim runaway’ conditions. In his Twitter video message, Muilenburg said: “We agree with the FAA that we must take action on this and we’re already working on the required software.”

Slat tracks

Separate from the additional software issue, in June the FAA said it had been informed by Boeing that certain slat tracks on the leading edges of some 737 MAX (and 737NG) aircraft, “may have been improperly manufactured and may not meet all applicable regulatory requirements for strength and durability”.

The FAA said: “Following an investigation conducted by Boeing and the FAA Certificate Management Office, we have determined that up to 148 parts manufactured by a Boeing subtier supplier are aff ected.

“The aff ected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process. Although a complete failure of a leading-edge slat track would not result in the loss of the aircraft, a risk remains that a failed part could lead to aircraft damage in flight.”

The investigation identified 179 737 MAX aircraft and 133 737NGs on which these suspect parts may have been installed. The FAA issued an Airworthiness Directive to mandate Boeing’s service actions to identify and remove the aff ected parts within ten days.

Operational disruption

The aggregation of all these issues – the slat track problem, the identification of the further software issue and the work to update the MCAS software – all add to the sense that the 737 MAX is a beleaguered programme.

This is a sense only heightened by the fact that additional software changes will inevitably take time to implement, meaning it is likely the 737 MAX’s re-entry into service is still some months away. Adding to the ‘beleaguered’ sense is the fact that there are the ongoing Congress and Senate reviews into the certification process for the aircraft.

Boeing has given no indication how long it will take to rectify the latest issues, but it stressed it will not off er the 737 MAX for FAA certification until it has “satisfied all requirements for certification and its safe return to service”.

Being led by requirements rather than time constraints is clearly a sensible approach, even if it does mean the aircraft remains grounded for some time yet.

Of course, the continued grounding means there is in the intervening time a continued and not insignificant consequence for the daily operations of the airlines to have received 737 MAX deliveries, with carriers having to carry on leasing replacement capacity and cancelling or amending flight schedules.

The latest announcements from the FAA and Boeing have extended the cancellations. Both United Airlines and American Airlines have removed the 737 MAX from their schedules into September, with American also forced to completely drop a route (Dallas/Fort Worth to Oakland) due to the lack of 737 MAX capacity.

Southwest Airlines, which has received more 737 MAX aircraft than any other customer prior to the grounding with 34 jets, has removed around 150 flights on the 737 MAX from its daily schedules up to October 1. The airline’s Chief Executive Officer Gary Kelly has been quoted by several media outlets as saying the latest issues uncovered mean it is likely to have to keep the jet out of its schedule beyond that date.

Meanwhile, in early July the Saudi carrier Flyadeal said it would not finalise a provisional commitment from last year for 50 737 MAX, and instead receive 30 Airbus A320neos via parent company Saudi Arabian Airlines. This might be seen as a sales blow, but equally, Flyadeal is an incumbent A320 operator, while IAG recently committed to 200 737 MAX for British Airways.

Boeing’s Q2 deliveries data, revealed early in July, showed 737 MAX deliveries were down by 75% compared to the previous quarter, to 24 aircraft, reflecting the production cut to 42 aircraft per month.

The Boeing 737 MAX test fleet photographed in 2016, before the type’s service entry. Boeing continues to work on returning the aircraft to flight, but recent simulator sessions identified an additional potential risk Boeing has been ordered to fix.
Paul Weatherman/Boeing