Maneuvering Characteristics Augmentation System

The Maneuvering Characteristic Augmentation System, usually called MCAS, is a feature made by Boeing. It is famous for its role in crashing two planes.

The system was put into the planes because the engines on the new 737 MAX were bigger and were further forward on the wing. This would cause the engines to push the nose (front) of the plane higher than usual leading to a stall.

On Lion Air Flight 610 and Ethiopian Airlines Flight 302, investigators found out that the MCAS was activated by errors in the angle-of-attack sensors. This caused the system to repeatedly force the nose of the plane down.^[1] After the plane had done this too many times, the plane hit the ground, killing everyone that was on it.

After the planes crashed, airlines all around the world stopped using the planes.^[2]