FAA Poised to Require Electrical Wiring Fixes Before Boeing 737 MAX Jets Can Fly Again

U.S. air-safety regulators are poised to order electrical wires relocated inside Boeing 737 MAX jets in the latest complication and potential delay for their return to commercial service.

The preliminary decision covers all of the nearly 800 MAX airliners produced so far. Federal Aviation Administration managers and engineers have concluded that the potentially hazardous layout violates wiring-safety standards intended to prevent dangerous short-circuits. Under extreme circumstances, wiring failures could cause flight-control systems to sharply point down an aircraft’s nose in a similar way to the automated maneuvers that brought down two MAX jets and claimed 346 lives.

The emerging agency view is based on longstanding regulations put in place following electrical fires and fuel-tank explosions on commercial jets over decades. Complications stemming from mandatory wiring changes could delay FAA directives ungrounding the beleaguered fleet for at least several weeks, some of the people said, potentially beyond the mid-June timeline previously projected by industry and government officials.

The wiring concerns also have turned into a test case of what Dave Calhoun, Boeing new chief executive, has touted as his more realistic and conciliatory approach toward FAA safety demands before allowing the MAX fleet back in the air. The FAA said on Sunday that it continues to engage with Boeing on the wiring issue and the MAX will return to service only after the FAA is satisfied that all safety-related issues are addressed.

A Boeing spokesman said that discussions with the FAA continue, but regardless of the outcome the company’s estimate for a midyear return to service is unchanged.

Industry and government safety experts have said the wiring issues should have been identified and resolved during the initial certification of the MAX. The stricter safety standards for wiring didn’t apply to earlier 737 models. Among major questions that still need to be answered, according to these experts, is precisely how and when wiring will be redone on aircraft which operated before the grounding. Looking forward, Boeing has agreed to make wiring design changes once the assembly line revs up again.

The wiring debate follows a long string of setbacks and hurdles for Boeing regarding recertification of the 737 MAX, including a recent FAA directive proposing mandatory inspections and fixes to a metallic lining that serves as a shield against lightning strikes for engine-control wiring.

Before the FAA will authorize resumption of passenger operations, MAX jets also will be subjected to checks of fuel tanks for debris, along with verification of mandatory inspections, maintenance procedures and operational readiness flights. Unlike past FAA procedures, agency officials won’t delegate signoff authority to Boeing to ensure MAX jets are airworthy and ready for airline operations.