The smooth re-entry into service of the 8 and 9 has hit a hick-up on April 9, when Boeing advised sixteen operators to address “a potential electrical issue” in a specific group of aircraft. Correcting the issue could take a few hours or days and so looks limited, but still, some have withdrawn the MAX from their operations for checks and repairs.

A Boeing statement contains rather scarce information on the issue, except for saying: “The recommendation is being made to allow for verification that a sufficient ground path exists for a component of the electrical power system.” The FAA told Bloomberg that the issue “could affect the operation of a backup power control unit.”

One airline affected by the recommendation is American. In a statement, COO David Seymour said that the issue is related to a production change made in the installation process. This concerns aircraft that were delivered to American after it received the last one before the of the MAX in March 2019, which followed after the fatal Ethiopian crash just months after the Lion Air crash in October 2018. A Boeing spokesperson stresses to Airinsight that the issue is unrelated to MCAS, the system that has played a detrimental role in the two crashes and has been modified since.

The Seattle Times reports that the issue involves a back-up electrical power unit, which instead of being secured by rivets is using fasteners to keep it in place. This has a resulted in a potential unsafe situation, as the unit is insufficiently grounded. This could lead to a malfunction of other systems, including potentially the auxiliary power unit (APU). All affected aircraft need to be modified.
The newspaper also reports on a quality issue with a batch of stabilizer motors that are fitted on various 737s versions. They also need replacement.

The newspaper report confirms that the latest issue is unrelated to the re-wiring of the electrical system that drives to the horizontal stabilizer motor. In the original design, the wiring looms were too close together and could trigger a short circuit, resulting in the loss of stabilizer function. After this deficiency was discovered in January 2020, Boeing did a redesign. Re-entry into service of the MAX in December 2020 was conditional to this modification to be executed, the FAA said. Other regulators, including Transport Canada, ’s ANAC, the UK’s CAA, EASA, and GCAA in the have included this condition in their requirements.

On April 9, Southwest Airlines said it would remove thirty MAX 8s from service for checks and repairs, out of 58 active aircraft with the airline. American would remove seventeen out of 41 aircraft, United sixteen out of thirty in service, and Alaska Air all four in service. No details have emerged yet from other MAX operators, including Air Canada and GOL.

Since the ungrounding of the MAX in December, Boeing has (re-)delivered 183 aircraft. The United Arab Emirates has been the last country to approve the return to service, with flydubai resuming MAX services on Thursday with the first flight to Pakistan.

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