Re:Airplanes and Accounting Games: The Coming Boeing Collapse?
by sokoloff on Friday December 20, 2019 @09:40AM
(#21844444)
25.173.a requires the aircraft to meet this section at speeds as low as the minimum speed for steady unstalled flight.
25.173.c requires the stick force curve to have a stable and minimum slope of 1 lbf/6 knots.
At high angles of attack (low speeds), the stick force reduces slightly as compared to lower angles of attack (higher speeds). This requires a negative slope at a point on the stick force curve, violating both the minimum slope and the stable slope requirement of 25.173. (indirect source: https://www.wsj.com/articles/how-boeings-737-max-failed-1155... ). They couch it as "pushes the nose up" (though the image cited is dual sourced to Boeing and a WSJ graphics author, so I'll wager that "pushes the nose up" is WSJ content rather than Boeing content).
25.173.c requires the stick force curve to have a stable and minimum slope of 1 lbf/6 knots.
At high angles of attack (low speeds), the stick force reduces slightly as compared to lower angles of attack (higher speeds). This requires a negative slope at a point on the stick force curve, violating both the minimum slope and the stable slope requirement of 25.173. (indirect source: https://www.wsj.com/articles/how-boeings-737-max-failed-1155... ). They couch it as "pushes the nose up" (though the image cited is dual sourced to Boeing and a WSJ graphics author, so I'll wager that "pushes the nose up" is WSJ content rather than Boeing content).