Wiring modifications to ensure aircraft meet certification requirements
Credit: Boeing
Operators also must spend up to 200 work hours per aircraft modifying wire bundles that do not meet electrical wiring interconnection system (EWIS) separation standards put in place after the 737NG was developed but before the 737 MAX was launched. The changes are to prevent the highly unlikely scenario of a short-circuit triggering an uncommanded horizontal stabilizer movement. Work on this began in mid-summer 2020 after Boeing and the FAA agreed on the requirements. Instructions differ slightly between the 737-8 and 737-9, but the general fix is the same. On the 737-8, it requires re-routing two existing bundles and installing five new ones. The work requires accessing the nose wheel well, forward cargo compartment, electrical and electronics compartment, and the rear fuselage area. The new bundles add 2.6 lb to the 737-8’s gross weight and 3.2 lb to the 737-9.