* Economic problem that the 737 engines used too much fuel, so they decided to install more efficient engines with bigger fans and make the 737MAX.
* Airframe problem. They wanted to use the 737 airframe for economic reasons, but needed more ground clearance with bigger engines.The 737 design can't be practically modified to have taller main landing gear. The solution was to mount them higher & more forward.
* Aerodynamic problem. The airframe with the engines mounted differently did not have adequately stable handling at high AoA to be certifiable. Boeing decided to create the MCAS system to electronically correct for the aircraft's handling deficiencies.
* Systems engineering problem. Boeing wanted the simplest possible fix that fit their existing systems architecture, so that it required minimal engineering rework, and minimal new training for pilots and maintenance crews.
* Sensor problem. The AoA vane on the 737MAX appears to not be very reliable and gave wildly wrong readings. On #LionAir, this was compounded by a
* Pilot expertise problem. If the pilots had correctly and quickly identified the problem and run the stab trim runaway checklist, they would not have crashed.
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