Month: April 2021

Southwest is removing 30 aircraft from service.
American is pulling 17 of its 41-strong fleet.
United has grounded 16 planes.
A change in Boeing’s 737 MAX manufacturing process that was insufficiently vetted caused an electrical system problem.
In this change, fasteners were used to hold a backup electrical power unit in place, rather than rivets. Fasteners did not provide a complete electrical grounding path to the unit.

What’s at stake with new 737 MAX electrical issues

After the events of the past few years it’s no surprise that when the 737 MAX has an issue, it receives a lot of coverage. And the latest 737 MAX headlines concerning potential electrical problems are no doubt a big headache for Boeing and its operators alike. It’s bad publicity at the worst possible time for the 737 MAX, when everyone involved will have been hoping for a smooth and quiet reintroduction to service. But it also raises new questions and concerns, on top of many already existing ones, about Boeing’s manufacturing processes and corporate culture. So just what is going on here, and what’s at stake?

To be clear, this appears completely unrelated to the issues that caused two fatal crashes of the type prior to its worldwide grounding. So just how serious are these new electrical problems?

First: what happened exactly?

Boeing has said this is a “potential” issue that affects a certain number of 737 MAX, but not all of them. Accordingly we’ve seen many of the major operators in the US pull select planes from their fleets. Southwest is removing 30 aircraft from service. American is pulling 17 of its 41-strong fleet. And United has grounded 16 planes.

The Seattle Times published an in-depth piece on what the actual issue is last week. According to that article, a “A minor change in Boeing’s 737 MAX manufacturing process that was insufficiently vetted caused an electrical system problem.” It seems that in this change, fasteners were used to hold a backup electrical power unit in place, rather than rivets. Boeing has said that it discovered the issue while building a new MAX and that, according to the Seattle Times article, the fasteners “did not provide a complete electrical grounding path to the unit.”

Boeing 737 MAX China grounded — The 737 MAX remains grounded in China, where regulators have yet to say when they expect to re-certify the plane.

Is it serious?

While this doesn’t sound like the most serious of issues that could crop up in the manufacturing process, and presumably can be handled without too much complex rework – it’s still troubling. Something like this could be quite dangerous because it has the potential to cause all manner of electrical failures, and that’s not something you want while flying an aircraft.

So Boeing advised all operators that had taken delivery of aircraft with the improperly installed units to inspect and fix them before flying those planes again. And it seems this is not something fundamentally wrong with the 737 MAX systems. All of that is good news. And yet it is troubling, not only for the flying public who may have new concerns about the plane – but also for industry observers.

American Airlines 737 MAX — American has been making good use of its 737 MAX since reintroducing the type. It has had to ground several for inspections because of the latest issues.

The big issue: manufacturing processes

Boeing is under a lot of scrutiny at the moment for failures in its manufacturing processes in recent years that have led to quality control issues with several of its aircraft – most notably the 787 Dreamliner.

Although it’s been less noticed in mainstream press, the 787 has been beset with production issues that have led to a significant slowdown in deliveries in recent months as airframes needed to be checked and in many cases fixed before being delivered to customers. These manufacturing issues may end up costing Boeing billions to fix when all is said and done – to say nothing of the further hit to its reputation.

Boeing did recently begin delivering 787s again. And aside from this issue the 737 MAX has had a relatively smooth rollout with dozens of airlines sending them back into the skies and it being mostly a non-event outside of avgeek circles. Indeed it seems that the expected public mass anxiety about getting back on a 737 MAX was greatly exaggerated, and most people aren’t even noticing that they’re on one.

But the fundamental issues at Boeing remain an ongoing concern, and even as the company fixes aircraft problems as they come up, many are wondering just how deep these problems go, and whether we’ve now seen the end of them. This latest 737 MAX issue only feeds those concerns.

Reported by FlightRadar24 on 14 April 2021.

Airline software super-bug: Flight loads miscalculated because women using ‘Miss’ were treated as children

Weight blunder led to wrong thrust used on takeoff, says UK watchdog

A programming error in the software used by UK airline TUI to check-in passengers led to miscalculated flight loads on three flights last July, a potentially serious safety issue.

The error occurred, according to a report [PDF] released on Thursday by the UK Air Accidents Investigation Branch (AAIB), because the check-in software treated travelers identified as “Miss” in the passenger list as children, and assigned them a weight of 35 kg (~77 lbs) instead of 69 kg (~152 lbs) for an adult.

The AAIB report attributes the error to cultural differences in how the term Miss is understood.

“The system programming was not carried out in the UK, and in the country where it was performed the title Miss was used for a child, and Ms for an adult female, hence the error,” the report says.

The Register asked TUI where the system programming was done, but the company ignored that question in its response to our inquiry.

“The health and safety of our customers and crew is always our primary concern,” a TUI spokesperson said in an emailed statement. “Following this isolated incident, we corrected a fault identified in our IT system. As stated in the report, the safe operation of the flight was not compromised.”

Potentially fatal math

Flight load miscalculations have the potential to affect aircraft handling and to create serious safety issues: the figures are used for figuring out fuel levels, altitude, takeoff thrust, and so on. The 2018 fatal crash of Cubana de Aviación Flight 972, for example, has been attributed to excessive load, as has the 1997 crash of Fine Air Douglas DC-8 cargo flight.

According to the AAIB, the software issue was first spotted on July 10, 2020, when three adult passengers identified as Miss were checked in as children. Airline personnel caught the discrepancy and proceeded to make adjustments manually.

On July 17, the developer(s) working on the check-in application “adapted a piece of software, which changed the title of any adult female from Miss to Ms automatically.”

Alas, the revised code could only convert honorifics for passengers prior to check-in. Bookings made with the title Miss that had already checked in, including those checking in online 24 hours prior to departure, could not be changed.

“On 20 July, 2020, the programmer was making enhancements to the program to improve its performance,” the report says. “This should not have stopped the program from working, but as this was a ‘fix,’ it could not be known for sure. A combination of the [TUI] teams not working over the weekend [to make manual corrections] and the ‘online’ check-in being open early on Monday 20 July, 24 hours ahead of the flight, meant the incorrectly allocated passenger weights were not corrected.”

On 21 July, 2020, three TUI Airways flights departed from the UK with inaccurate load sheets as a result of the software issue, which would not be fixed until July 24, 2020.

The first of these, and the only one detailed in the report, was TUI Airways flight BY-7226, a Boeing 737-800 with the registration G-TAWG. The plane travelled from Birmingham International Airport in the UK to Palma de Mallorca in Spain, carrying 167 passengers and 6 crew.

The 737-800 departed with a takeoff weight that exceeded the load sheet (the projected weight) by 1,244 kg (~2743 lbs) because the load sheet listed 65 children on board, compared to the 29 children expected from the flight plan – which includes the actual weight. The load sheet also varied from the flight plan due to errant baggage weight calculations.

The result of all this was that the plane used less thrust to take off than it should have – 88.3 per cent instead of 88.9 per cent given its actual takeoff weight and environmental conditions. Fortunately, this was “marginally” more than the minimal regulatory requirements – 88.2 per cent – and the flight made it to its destination safely.

It’s suggested this won’t happen again: “An upgrade of the system producing load sheets was carried out to prevent reoccurrence,” the report concludes. ®

Reported by The Register on 8 April 2021.