Thread by @QuisitiveInvest

1/ A brief refresher on why the Boeing 737 MAX has significant engineering problems that make it uncompetitive versus the Airbus 320neo $BA

All sources, research and documents available here:
unhedged.com/exchange/5dd14…

2/ Around 20-25% of the cost to fly an airplane is fuel costs. Therefore, fuel efficiency is critical. When Airbus unveiled the 320neo, it was 15-20% more fuel efficient than existing 737s or prior Airbus 320's

3/ The solution to fuel efficiency is larger engine sizes (hence why large cargo ships are more cost-efficient than small cargo ships - larger engines, among other things).

To make a more fuel efficient aircraft means placing larger engines on it.

4/ By shear dumb luck, owing to designs made over 5 decades ago, the Airbus 320 has wings placed higher on the fuselage than the 737. This gives more room for a larger engine under the wings.

5/ When Boeing saw the Airbus 320neo, they knew they also needed a larger engine. But their wings were too close to the ground. So they mounted the engine forward and lifted it up off the ground.

6/ This seemed to work fine in the computer models, and then again in the wind tunnel testing of the prototypes, seemed to work out okay. Then came the actual airborne tests, which occur 3-4 years after design and after billions of dollars spent on research & development

7/ Once airborne, Boeing learned that the forward placement of the larger engines created additional lift during high-G force turns (climbing turns, during take off, for example). This causes the aircraft to become aerodynamically unstable and want to "stall"

8/ A "stall" means the aircraft has lost its ability to produce lift, or, in simple terms, it will fall out of the sky.

Not necessarily the end of the world, you can add foils and flaps around the aircraft to control these deficiencies.

9/ Turns out, though, that the addition of these extra flaps that would make the MAX aerodynamically stable introduced excess drag that essentially eradicated the fuel efficiency gains that were needed to justify the program in the first place

10/ So Boeing tried to create some software to prevent the aircraft some entering a stall during a climbing turn (famously, "MCAS"). Problem is the software doesn't work well, and without it, the MAX is the only aerodynamically unstable aircraft trying to enter commercial service

11/ To fix the problem requires physical changes that reduce fuel efficiency. In other words, the changes necessary make the product uncompetitive against the Airbus 320neo. Hence why they keep fiddling with MCAS. Doesn't change the math or the engineering. Its a flawed design.

12/ Back to the drawing board. Boeing needs to design a new airframe. End of story.