Following the two crashes of MAX8 jets, Boeing is back with the software developing team to update the MCAS software.
MCAS (Maneuvering Characteristics Augmentation System) software was designed to swivel the horizontal stabiliser to push the nose pitch down to avert a stall.
The updated MCAS software, will now;
– give the system input from both angle-of-attack sensors,
(Currently it takes only from one angle of attack sensor)
– MCAS will limit how much it moves the horizontal tail.
(currently it moves four times faster than was stated in the initial safety analysis document.)
– Software limits MCAS to kick in only for one cycle, rather than multiple.
(Currently it kicks in multiple times as long as it senses AoA change)
Flight data retrieved after the Lion Air crash indicated a faulty AoA sensor, that triggered MCAS multiple times during the flight before it crashed.
Like all 737s, the MAX actually has two AoA sensors, one on each side of the fuselage, but MCAS was designed to take a reading from only one of them.
A software engineer Trevor said in a trail of tweets, the crashes were “Economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed”