Third Pilots' Union Raises Concern About Boeing 737 Max Jet (opens in new tab)

Exactly this. Following the existing memory items and QRH checklist items taught to every 737 pilot is (very, very likely) enough to overcome this contemplated scenario of a runaway trim from a flaw in the stability system. (It's remotely possible that the crew holds no blame in that they followed the checklist properly and the cutout switches were defective or the checklist response was otherwise insufficient.)

Here's a picture of the cockpit, showing the location of the power switches, trim switches, and the wheel that turns when the stab trim is running.

I find it hard to understand how the pilots would not know the stab trim was moving, and how to cut it off.

https://www.nytimes.com/interactive/2018/11/16/world/asia/li...

One question I have: on Boeing how easy is it to just jump down to secondary law to give up some of the flight envelope protections. Can that be switched manually? How exactly does that look?

If you know computer is getting garbage data / plane acting in an unusual way, you can dial things back. These planes and their engines are so reliable and maintenance is usually so good that it seems you could fall back to closer to direct law flying (power setting / pitch / etc) and at least keep plane out of the drink / gain some altitude.

I think I read somewhere that they are not getting the 'pings' from the Cockpit Voice Recorder like they did the Flight Data Recorder, which was recovered.

I believe the force of impact, which was almost vertically nose down at high speed just caused such a shattering of the airplane that it might have fatally destroyed the CVR, or else driven it under many feet of mud and silt.

Re: Your last point - I think this time around the CVR could vindicate the crew and point the blame at Boeing, so it may seem in their best interest to recover it and have extra proof for the court case. Then again, the level of corruption in Indonesia could affect what happens with the recovery process.

Yes. This is a very specific failure mode, and given the publicity of this event, it's not going to catch anyone else out.

Now, that doesn't mean I didn't double check the aircraft types for some upcoming flights flights...

Pulling back on the controls moves small control surfaces (elevators) on the horizontal stabilizer (the "tail wing"). The way the anti-stall measure works on the MAX (and many other planes, to be fair) is by adjusting the pitch trim. Adjusting the trim changes the angle of the entire horizontal stabilizer.

https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi...

It's very possible for the effect of the extreme trim condition to be more than the elevators can overcome. The pilot can certainly override the trim setting, but the issue here is that they weren't expecting that to change, since they weren't trained on the fact that the plane might do it automatically (in those flight conditions).

Here's a good video explaining how trim works (in normal operation) on a (slightly older) 737:

https://www.youtube.com/watch?v=l62NvkRWa5E

No, my first instinct is to give it the beans and push the nose down more because more often then not you're in a stall if that happens. Also, as a general "rule", it's pretty common for American aircraft to provide easily accessible overrides to the envelope protection stuff. I've never seen the cockpit of an Airbus, but, from what my friends have said, it's much harder to do. I don't know if Boeing is going in that direction, but I doubt they would.

Yes, but this is where it gets a little complicated, and why this accident is so fascinating to many people in aviation...

>> if the nose of a plane suddenly drops, isn't the pilot's first instinct to pull back on the controls to raise it?

Not exactly, as the correct way to get out of a stall is pointing the nose down, in order to pick up airspeed to gain more lift. The stall horns were going off, so the pilots may have thought they were stalling. In addition, as others have mentioned, the yoke alone may be unable to beat out the trim by the autopilot.

>> From what I've read, in Boeing aircraft at least, the pilot's controls can always override the automatic systems.

Historically, you are exactly right. This is the _biggest_ reason pilots are pissed at Boeing right now. It's believed that the autopilot was turned off entirely when the plane started thinking it was stalling, and trying to point itself down. This is not present on any of the original 737 aircraft, only the MAX series, and Boeing didn't inform pilots of this.

The aircraft was serviced just the night before. Somehow, that failed.

If the company knew about this issue, I doubt they would have authorized putting the aircraft in service.

Yes, same aircraft.

I have less ire for Boeing than I do the FAA.

There was an interesting comment on airliners.net that the USSR operated new airliners on freight services for several years before putting them on passenger services. So far I've confirmed that for the Tu-154 trijet, for example, which flew freight for two years before taking a revenue passenger.

But in the West there has always been a tension between certificating for safety versus commercial imperative. Why hasn't the 737Max been grounded pending investigation? Because that would lead to companies losing money. Why would the FAA care about that? Because it considers manufacturers and airlines as 'stakeholders'.

“I’d rather be hit by a bus than fly in an Airbus”

There’s versions of these type of statements for all aircraft manufacturers. Does it add anything to the conversation to state them? Not in my opinion.