Boeing insisted on Monday that it did not intentionally deactivate the angle of attack disagree alert on the 737 Max narrowbodies delivered to Southwest Airlines following a report on Sunday by the Wall Street Journal that the carrier “disabled” the feature on models that did not come with angle of attack (AOA) indicators. Boeing did concede, however, that the disagree alert did not activate in airplanes that came with the AOA indicators.
“The disagree alert was intended to be a standard, standalone feature on Max airplanes,” said Boeing in a statement released Monday. “However, the disagree alert was not operable on all airplanes because the feature was not activated as intended.
“The disagree alert was tied or linked into the angle of attack indicator, which is an optional feature on the Max. Unless an airline opted for the angle of attack indicator, the disagree alert was not operable.”
A Boeing spokesman confirmed to AIN that the company at first failed to recognize that the disagree alert would not work on airplanes not equipped with an angle of attack indicator. He said he could not yet elaborate on the reasons behind the oversight, however.
Boeing has since decided to include the disagree alert independent of the still optional angle of attack indicator once the Max returns to service. A service bulletin will instruct airlines on how to activate the disagree alert on the Max, it added.
The company said although it included the disagree alert as a standard function on the Max, it does not consider the feature necessary for the safe operation of the airplane.
“On every airplane delivered to our customers, including the Max, all flight data and information needed to safely operate the aircraft is provided in the flight deck and on the flight deck display. This information is readily accessible to pilots, and it always has been,” said Boeing.
“The airspeed, attitude, and altitude displays, together with the stick shaker, are the primary flight information indicators in the flight deck. All recommended pilot actions, checklists, and training are based upon these primary indicators, not on the AOA disagree alert or the angle of attack indicator.”