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from the pulled-the-handbrake-as-hard-as-I-could dept.
A 2018 FAA (Federal Aviation Administration directive advised pilots to handle MCAS (Maneuvering Characteristics Augmentation System) failure by disabling electric control of stabilizer trim using a pair of cutout switches. Pilots would then need to use a hand crank to move the stabilizer back to the desired position. It's noted that previous 737 models had separate switches to disable autopilot and electric stabilizer control, but the 737 MAX lacked this distinction.
Avionics engineer Peter Lemme explains how aerodynamic forces acting on the stabilizer and elevator in a nose-down situation would oppose pilots' attempts to correct the trim using their manual control.
A 1982 Boeing 737-200 Pilot Training Manual acknowledges this possibility, describing a series of maneuvers which can be used to relieve force on the controls and allow incremental correction of trim. However, it's suggested that the Ethiopian Airline plane had already gained too much speed and lost too much altitude for such a maneuver to be possible.
https://www.moonofalabama.org/2019/04/ethiopian-airline-crash-boeing-and-faa-advice-to-737-max-pilots-was-insufficient-and-flawed.html
https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html
(Score: 3, Insightful) by bussdriver on Tuesday April 09 2019, @01:17PM
They are appealing known biases to distract from the real issues. New is not always better; design is always a compromise of factors and revisions can go backwards.
The current problem didn't exist in the 1990s -- it was the changes made to the NEW jets that caused the problem. The answer is not to say it should have been completely re-engineered from the ground up. It takes time, testing, experience to refine something which is why most things are never truly NEW because we largely redesign around the previous knowledge. The so-called all-new products are usually 90% the old ones even where they re-evaluate everything, tweaking everything slightly is still mostly the same old design. They are just as likely to mess up on a newer model plane design, newer computer with a million more lines of code, if not more likely.
This is NOT a video game, extra computing power is not necessary-- it's EXTRA. Oh, there is a thriving market of retro games that do not require cutting edge processing power. My toaster works; it does not need a chip and certainly not one for nerds to hack into a webserver to show off (that's been done, BTW.)
If something works well or has been optimized it shouldn't require and will only marginally benefit from revision (odds are it goes backwards.)
REGULATORY CAPTURE and GREED that is the real problem.