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1 in 5 MAX jets affected by another electrical fault

written by Hannah Dowling | April 19, 2021

737 MAX Family in flight (Boeing)

Engineers have located additional manufacturing flaws in a significant number of 737 MAX jets following earlier inspections into possible electrical issues within the cockpit.

Last week, World of Aviation reported that dozens of 737 MAX jets were grounded due to production problems resulting in possible electrical faults within the aircraft cockpit’s backup power control unit.

Now, engineers working to identify and rectify said faults have found new similar manufacturing flaws elsewhere in the cockpit, which affect the devices’ grounding capabilities, according to sources close to the matter.

The new grounding issues were located in the storage rack where the backup power control unit is situated, and the instrument panel that faces the pilots, the sources said.

Electrical systems need to be grounded in order to maintain safety in the event of a surge of voltage that could otherwise lead to shock or electrocution in the event of a device malfunction.

Around one in five 737 MAX jets could be affected by the flaws, largely those that were delivered following the lifting of the 20-month grounding of the MAX by the Federal Aviation Administration in November 2020.

The faults have no connection to the MCAS operating system that was linked to the two fatal 737 MAX crashes in 2018 and 2019, which sparked the near two year grounding.


Boeing is expected to soon release a bulletin advising airlines how to fix the grounding issues, following consultation with the FAA.

Under last week’s grounding order, 16 airlines were forced to ground a total of 90 MAX jets for inspection.

Boeing reportedly found the initial fault to be as a result of a “production issue” that could affect the operation of a backup control unit.

Boeing said in a statement that it wants the relevant MAX operators to check and verify that a “sufficient ground path” exists for a component of the electrical power system.

The planemaker stated that the required repairs for each aircraft could take merely a matter of hours, or up to a few days. Once completed, airlines can reinstate the aircraft for operation.

The three major airlines in the US – American Airlines, United Airlines and Southwest Airlines – together had to remove more than 60 jets from service.

It is not yet clear whether future 737 MAX deliveries will be affected, or whether they too require checks for electrical faults.

However Cai von Rumohr, an analyst from investment banking firm Cowen, said that the “relatively straightforward” nature of the inspection and rectification effort for this problem means these additional inspections are “unlikely to be a show stopper”, if they are required.


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