LE BOURGET—Boeing is getting a head start on retrofitting the 737 MAX fleet with an additional angle-of-attack monitoring system by rolling out new aircraft with the needed wiring in place and preparing a service bulletin for operators to use on in-service airframes.

"All the airplanes we are building now are pre-wired," 737 Customer Leader Bob Michael told ShowNews on June 18 at the Paris Air Show. "We actually started to install the wiring on production [aircraft] last summer."

The enhanced angle of attack (eAOA)—required by the European Union Aviation Safety Agency (EASA) as part of agreeing to the 737 MAX's return to service following fatal accidents in 2018 and 2019 and its subsequent grounding—provides a third source of AOA data. It uses five software monitors embedded into existing hardware to track data from the aircraft's two physical AOA sensors, explained Boeing 737 MAX Chief Pilot Justin Carlson. Any abnormalities are detected and flagged, and the malfunctioning AOA sensor is removed. 

"All of that happens automatically," Carlson said.

The system also includes new switches that allow pilots to disable nuisance alerts triggered by a malfunctioning AOA. The new monitoring is designed to do this, but the switches serve as a backup, Carlson said.

Boeing has agreed to roll out the entire package of changes on the rest of the 737 MAX fleet within three years once it gets certified on the 737-10. Ideally, the work will be done during scheduled heavy maintenance visits.

"There's a fair amount of wiring that has to be added in the flight deck and in the [electronic equipment] bay," Michael said.

The company is working on a service bulletin that operators can use to pre-wire their 737 MAXs. It is expected to be released by yearend. Once the 737-10 is certified, a second service bulletin will detail the entire upgrade. Boeing's latest plan includes FAA approval in 2024.