Following two fatal crashes and the eventual grounding of the Boeing 737 Max 8 aircraft, it has been revealed that the plane had two safety features that were sold as optional extras. The New York Times reveals that the additional sensors would have checked on data collected by existing sensors, and could have alerted pilots to potential issues.
Specifically, the 737 Max 8 of Lion Air and Ethiopian Airlines lacked an “angle of attack (AOA) disagree” light. To clarify, the AOA sensors essentially detects if the plane is about to stall, based on the direction the plane’s nose is pointing in relation to the airflow. And when two AOA sensors present data that don’t match, the AOA disagree light will light up to indicate so.
Another feature that was missing was an AOA indicator. Unlike the AOA sensor, the indicator is designed to translate the data from AOA sensors into a visual representation.
It was also reported that the Maneuvering Characteristics Augmentation System (MCAS) anti-stall system on the Boeing 737 Max planes only used one AOA sensor at a time, despite there being two on the plane. Upon detecting an imminent stall, the MCAS adjusts a plane’s tail stabilisers, pushing the plane’s nose downward. The increased airspeed when descending helps prevent a stall, but can be fatal when it kicks in at the wrong time, which has been made evident by the two crashes.
Having the AOA disagree light could have alerted pilots to faulty sensors. Thus allowing them to disengage the MCAS so that it doesn’t make the plane nosedive due to faulty sensor readings.
A source close to the New York Times also said that the AOA disagree light will be added as part of an update to the MCAS. The update in question is expected to be deployed by the end of April, and will also have the MCAS take readings from both AOA sensors instead of just one. That said, it looks like the AOA indicator will remain an optional extra.
These are just two items on a list of optional extras Boeing charges airlines. If anything, this is a scenario where microtransactions are so bad, they cost lives instead of money when an airline decides to save a few ringgit.
“There are so many things that should not be optional, and many airlines want the cheapest airplane you can get.” Mark H. Goodrich, an aviation lawyer, told the New York Times.