Posted on 11/18/2020 5:52:54 AM PST by RoosterRedux
after all this global freakage, it’ll be the safest plane in the sky. I’m sure the FAA over-certified it, boeing isn’t going to shoot itself in the man-parts again, and the european regulatory agencies didn’t want to make it back into production in the first place out of their desire to help airbus.
I’d be happy to be the first to fly on it.
Beyond bad software, it’s a bad design concept. No way low altitude, low speed flight should depend on a single AoA probe, and software reacting properly. Not like we’re talking a military system here, passenger jets should prioritize robustness over everything, be very boring.
I don't know if this Boeing Update has been posted but This required software function operates in unusual flight conditions only and now relies on two sensors, activates only once and never overrides pilots’ ability to control the airplane.
The revised MAX uses both AOA sensors at all times, plus it synthesizes a third AOA reading from the other sensors onboard (air speed, GPS positioning, etc.,) as a cross check. If the two physical AOA sensors disagree, the third synthetic AOA will decide which of the two are closer to the truth. This third synthetic sensor was mandated by the European regulator EASA.
I still maintain that the second Ethiopian Airlines crash only occurred because the flight crew didn't read the Airworthiness Directive that Boeing sent to all MAX operators after the first crash.
Had the Ethiopian crew did what that AD directed, there would not have been a second crash.
The crashes happened because pilots were not aware of MCAS and it's ability to create a runaway trim scenario from faulty sensor input (AOA and/or airspeed). Worse, MCAS could create a repeated scenario by re-engaging after pilots used their electric trim controls to recover. Pilots would think they had recovered by trimming up and disengaging the autopilot. MCAS would re-engage and recreate the problem all over again. MCAS was not disabled by disengaging the autopilot – always on.
With MCAS malfunctioning and repeatedly engaging and calling for nose-down trim pilots would have to use their electric trim controls to command nose up. This would dis-engage MCAS, briefly, but then it would re-engage. This was seen not only in flight data from the crashes but from other flights where pilots were able to recover. The solution is to recover reasonable trim attitude then pull the breaker removing MCAS's ability to change control surfaces. This was successfully done on several other flights with sensor issues that did not crash.
The gotcha is once the pilots pull the breaker, they have to use the manual hand wheels to adjust trim. SOP but... Recovering from significant trim (stabilizer deflection up or down) requires time and strength due to aerodynamic forces on the stabilizer, particularly when it is fully or nearly fully deflected. On the 737 the trim system changes the AOA of the entire horizontal stabilizer. When trimmed nose down this can create more nose down pitch than is possible to counter-act with the elevators commanding full nose up. (note, as an engineer I'm not sure I'd have designed the controls that way. I'm assuming there's some reason why it is necessary for the trim system to have that much aerodynamic control)
I’ve read that the Ethiopian crash was due to their inability to manually recover trim. They had successfully pulled the breakers but without the electric assist they could not manually trim back up in time. The net is that like so many aviation incidents it isn’t just one thing, it’s a whole sequence or series of things.
Did Domimion get the software problem solved?.
Perhaps you are unaware that the airline specifies the interior, not Boeing or Airbus. For example, the Boeing 787 economy class can be configured 3+3+3 (17.5" wide seats) or 2+4+2 (19" wide seats).
Some airlines will stuff that extra seat in each row, some do not. I've flown on them in both configurations. Even with the extra (narrower) seat, I find it much more spacious than the competing Airbus A330.
Of course that's because the 787 is 15" wider than the A330. But then the A350 is 5" wider than the 787. And then again the 777 is 11" wider than the A350.
It's the airline that's cramming in the people, not the aircraft manufacturer
Have you flown on a Boeing 787?
The cabin is at higher pressure and humidity, thanks to the carbon fiber fuselage's superior strength and corrosion resistance. The difference is noticeable. I've flown in them numerous times, including 15 hour flights. I am in much better shape when I land after a long flight in a 787 compared with any other plane.
I also appreciate the much larger windows and LED mood lighting (cool colors to help sleep, warm colors to help wake you up).
But seriously, the higher pressure and not-super-dry air (from electric driven compressors, not smelly engine compressor bleed air) is marvelous. And Airbus offers nothing like it.
I was thinking about you today when I heard this news. I hope you enjoy your first flight on one of them!
Megan
“Beyond bad software, it’s a bad design concept. No way low altitude, low speed flight should depend on a single AoA probe, and software reacting properly.”
Actually, that isn’t true at all.
The Federal Aviation Regulations (FAR) require that for an aircraft to be type rated the same as any previous aircraft that the control pressure must be the same. The Max changed control pressure by a small amount, so MCAS was created to change the pressure by putting the nose down slightly.
The Max flies great and is perfectly stable as is.
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