[GregTravis]

Hello,

This is Gregory Travis, who wrote the original article on which the EE Times article is based. If any of you have a specific question regarding my conclusions or how I got them or want to discuss any statements of fact, I'm more than happy to engage.

[F111John]

Gregory,

In your paper, you erroneously claim that the MCAS system creates forward pressure on the control column ("pushes the pilot's control columns in the down direction".) This is incorrect. MCAS only acts on Horizontal Stabilizer Trim, and doesn't work at all when autopilot (which does provide control column forces) is active.

You also claim that the 737MAX doesn't have "mechanical connections between the pilot's controls and the things on the wings, rudder, etc." when the 737MAX does have full mechanical linkages between the control columns and the flight control surfaces. Those surfaces are normally hydraulically actuated, but if all hydraulics fail there is physical manual control of the elevator and ailerons, also known as "manual reversion."

Because of these glaring errors, your paper loses much of its credibility in critiquing Boeing designers.

[prolepunk]

Thank you for your paper.

It was a worthwhile read and it filled in a lot of details I didn't notice about the crash also affirming the criticism I hold of the process of software development -- where all of the decisions are deferred to the magical 'algorithms' without considering what who writes the algorithms and how decisions about them are made.

The more persistent problem would be how artificial intelligence is used to increase 'engagement' while also fueling hate, and is an example of programmers and their managers not listening to social scientists and journalists.

When planes goes down it's the case programmers and their managers don't listen to engineers and people on the ground.

[rconti]

Thanks for checking in, hopefully this gets the visibility it needs. (and sorry it's the eetimes article getting the publicity!)

https://drive.google.com/file/d/1249KS8xtIDKb5SxgpeFI6AD-PSC...

[jordan_clark]

Hey Greg - serious question - The A320NEO has a very similar engine placement as the Max8. Wouldn't that air frame be faulty too if the problem was solely due to engine placement being in front of the wings?

[mhb]

Why is this: “once this thing pitches up, it wants to keep pitching up”? And why is it more of an issue with the engines in their new position? Thanks.

[GregTravis]

Couple of things here to keep in mind. First, when the A320 came out I wrote extensively about its fly by wire system, which was highly controversial at the time (early 1990s). It’s been nearly thirty years since then and long story short, Airbus has vastly more experience with implementing cockpit automation than Boeing. Boeing simply got in far over their expertise with deadly results

Second, Airbus’ 320 airframe does not impose the same issues with larger engines that the 737 does. For starters, the 330 airframe started life in the era of large high-bypass turbofans — its initisl engines were much larger than the 737’s initisl engines

[GregTravis]

It wants to keep pitching up because the engine cowlings are now far ahead of both the center of gravity and the center of lift. And the cowlings generate significant lift themselves. Aerodynamically they act as levers that pull the nose up and the higher the angle of attack, the more they pull. That is dynamic instability and as I point out you want to have ejection seats in any dynamically unstable aircraft (ir fighter jets)