Boeing 737 Max Hit Trouble Right Away, Pilot’s Tense Radio Messages Show

ISTR that after a carrier catapult takeoff, Naval aviators have 10 seconds for AoA to get into the "green zone." Otherwise it's an automatic eject. Forgot where I read that and if it's only for specific aircraft types, though.

The AoA sensor, previously largely irrelevant in civilian aviation as posted by an earlier poster, became a deadly concern seeing as a malfunctionimg sensor pumping inaccurate data to a downstream control unit with seemingly no way to validate or reject incoming bad data would respond just as happily to a reading 20 degrees off of where it should be. That this happened in a manner completely foreign to someone thoroughly experienced with a 737 just exacerbates the risk. Especially when said response is no longer overriden in the traditional response in old airframes. This is a usability regression, and should have been explicitly documented.

You seem very convinced that MCAS is some trivial system when it is very clear physically and legally speaking that that +/- 2.5 degree stabilizer movement at the right time is what the air-worthiness certification is dependent on.

>on re-cert as 737, and failure to train

Just because the damn thing flies doesn't mean basic automation system architecture, design, and ethical principles stop applying. You do not make a decision for an operator/user and not communicate the importance to them ahead of time. Doing so fundamentally changes the nature of the device.

To put it another way:

>"If you change the working parts, you make a different machine."-The Protomen, Father of Death

Or if you prefer someone a bit more established here's Edward W. Demmings view on it:

>"Every system is perfectly designed to get the results it gets."

From which comes the corollary:

>"Given two systems, if one produces results irreproducible in the other, then the systems are not the same."

>On Software that has the potential to kill people

Has no one learned from the lessons of THERAC-25? How many more need to die before "hide interlocks in software and skimp on training" stops claiming lives?

I fight the attitude that leads to these types of poorly thought through decisions every day in far less life threatening systems. Seeing it happen in such a high stakes industry just makes it all the more painful to have to endure.

>on appeals to occupation/authority

You don't need a pilot's license to connect the dots. You just need time, the right skill set and exposure to engineering in multiple contexts, and enough exposure to human social dynamics to realize that the MCAS augmentation is exactly the type of innocuous looking change to have slipped through the cracks. When you're in the trenches developing highly complex systems, you are in a highly faith based environment in the sense that while you are working from empirical measurements and simulations you have to have faith that all the relevant questions have been asked and answered. Engineers frequently discount the impetus of Sales/Business pressure, then turn around and don't question the deadlines those commitments made elsewhere, and accept the consequences thereof (I.e. questions not asked/answered due to time constraints).

As I said before. I'm waiting for more data. Even if MCAS isn't involved, the above mentioned issues are gross failures of system implementation that need to be remedied or otherwise addressed.

I'm not arguing it's one and done, but even if it turns out leprechauns swarmed the plane en masse disassembling it in flight, enough information has come to light that anyone can see there has been some serious ball dropping going down; ball dropping so serious that uninitiated customers are speaking out in discomfort instead of simply "leaving it to the eggheads".

I am very vocal on issues like this. I have been told I have a knack for the highly technical subjects, the inquisitivenes to run down things I don't know, and a bullish propensity to follow the facts wherever they lead. I see it as my responsibility to ask and find answers to the questions others don't even know how to ask, and to present them as best I can so that others may understand and come to their own judgements. Hell, I even learn something every now and again.

If that is your definition of non-triviality then the ash tray in the toilet is also a non-trivial system since the certification is dependent upon it being there.

MCAS is only there to compensate for one part of the flight envelope where normal operations shouldn't be taking place.

Point being, without that system the aircraft would still fly. In fact Lion air wouldn't have happened without it.

Of course there could be a fault (beyond the nonsense of it not being triple redundant). Or it could be something unrelated to MCAS which is my own pet theory (partly based on the reports of pitch excursions with the autopilot engaged where MCAS is irrelevant).

From your senario when the trim moves nose down. You apply nose up on the elevator which makes the trailing edge of the elevator go up which applies a downwards force on the trailing edge of the stabilizer. In order to move the trim back towards neural you need to lift the trailing edge against this force.

If the trim is extreme you may have to relax back pressure to reduce that force.

By in trim speed they mean the speed at which the aircraft would naturally settle at given the current trim setting.

If you are referring to the documented procedure for recovering from a trim runaway, then all 737s would be dangerous, as this is the same procedure for trim runaway recovery as it is for the prior versions, and regardless of whether it is caused by an MCAS fault or for any other reason. The pilot is not expected to determine whether it is an MCAS fault before acting, because the recovery from runaway trim is the same, regardless of cause.