The 737 MAX continues to give Boeing problems. Last month, some of the planes were grounded again due to electrical grounding issues in three different parts of the aircraft.
These problems are unrelated to the software malfunction that caused two fatal crashes in 2018 and 2019 and led to the worldwide grounding of the aircraft, but they did result in a removal from service of almost 25 percent of the global MAX fleet: 109 in-service planes and more than 300 in Boeing’s inventory.
A total of 16 airlines pulled the planes from active duty after Boeing warned of an electrical grounding problem in the aircraft’s cockpit backup power control unit. Boeing identified that there was insufficient electrical bonding on some of the panels in the cockpit, which could “result in loss of critical functions … which may prevent continued safe flight and landing.” The problem could cause malfunctions in a variety of systems, including the engine de-icer and the tail’s auxiliary power unit, as well as other issues in the cockpit. No airline has reported having these problems—meaning the issue was caught in time before any incidents occurred.
Subsequent grounding problems were found in the unit’s storage breaker panel and the main instrument panel. The problems originated on the production line, meaning that delivery of new planes was halted while the problem was being addressed. The flaw resulted from a minor change in the manufacturing process: the power control unit was attached to the flight deck rack with fasteners rather than rivets, which led to an improper electrical grounding.
This change was implemented as a measure to speed up aircraft production via an improved hole-drilling process.
Boeing originally said it had identified the problem, having discovered the issue in a newly built plane that hadn’t been delivered yet. The aerospace giant also claimed it knew how to fix the issue—proposing adding a bonding strap or cable that workers would screw onto two different surfaces to create a grounding path. It sounded like it would be a quick fix—requiring as little as a few hours to rectify, or at most about 24 hours. The company had prepared service bulletins detailing how to fix the problem.
The repairs are expected to cost about $155,000 to fix the planes owned by American carriers.
But while the FAA originally signed off on the bulletins—the regulator later changed its mind. The FAA asked the plane maker for additional analysis regarding whether other subsystems on the aircraft would be affected by the grounding issue—and to provide documentation to support its conclusions. The FAA finally approved Boeing’s proposed fix—over a month later.
This extra analysis delayed the aircraft’s return to the skies—and such a measure for what would normally be a routine fix indicates that the FAA still doesn’t trust Boeing. The agency’s sometimes cozy relationship with Boeing was heavily criticized in the aftermath of the fatal crashes.
And as if that weren’t enough, the FAA also issued an Airworthiness Directive regarding possible engine corrosion in some CFM LEAP-1B engines used to power some of the MAX aircraft. This corrosion could have developed from the planes being put into storage for over two years while the MAX was grounded worldwide. While not considered dangerous, the corrosion could lead to reduced thrust.
It’s clear that even though the 737 MAX is back in service, with Boeing’s backlog steadily being delivered to eager customers, the aircraft will still be watched closely by the FAA for the slightest defects. This is bound to continue for the foreseeable future.
Read more about the return to the air of Boeing’s best-selling plane at FAA Clears the 737 MAX for Takeoff.