Exclusive: Boeing software re-activated before Ethiopian crash - sources

Roto-Reuters ^ | April 3, 2019 | Eric M. Johnson, Tim Hepher

[Yo-Yo]

SEATTLE/PARIS (Reuters) - Boeing anti-stall software on a doomed Ethiopian Airlines jet re-engaged and pushed the jet downwards after the pilots initially turned it off due to suspect data from an airflow sensor, two people familiar with the matter said.

It was not immediately clear whether the crew chose to re-deploy the MCAS system, which was designed to push the nose of the 737 MAX down to prevent one kind of emergency but which is suspected of exacerbating a scenario linked to two crashes.

[Yo-Yo]

But investigators are studying the possibility that the software kicked in again without human intervention, one person with knowledge of the matter said, while a second said the software had engaged as many as four times.

The only way to disable MCAS is to disable power to the electric stabilizer trim motors. The only way for MCAS to engage again is to reactivate power to the electric stabilizer trim motors. The power cannot restore itself.

Flip both Stab Trim switches down to the Cut position, and the problem is solved.

The new problem is that you must then manually crank the Stabilizer Trim wheels, which can be a real physical workout. Maybe the pilots didn't want to crank the trim manually, so they kept turning the electric trim motor back on.

Here's an excellent video showing exactly how to disable MCAS:

https://youtu.be/xixM_cwSLcQ?t=753

[Moonman62]

The new problem is that you must then manually crank the Stabilizer Trim wheels, which can be a real physical workout. Maybe the pilots didn’t want to crank the trim manually, so they kept turning the electric trim motor back on.

...

I’d say they didn’t have the strength or the confidence.

[redshawk]

SkyNet.

[Delta 21]

Need more training.

[thoughtomator]

Software took the pilot’s authority away from him and made decisions it should not have been authorized to make, all on its own. That’s the crux of the problem here. Might be worth it to hire actual experienced pilots to program these things.

[Fido969]

Holy cow.

[Zathras]

As posted on another thread, EETIMES thinks its an airframe design issue caused by moving engine location.
Engineering mag written by engineers for engineers.

https://www.eetimes.com/document.asp?doc_id=1334482

[mylife]

MCAS is scary.

[Moonman62]

Software took the pilot’s authority away from him and made decisions it should not have been authorized to make, all on its own.

...

The pilot has the ultimate authority to disable any automation and fly the plane manually.

[mylife]

Boeing, you have a problem.

[Mr.Unique]

...due to suspect data from an airflow sensor, two people familiar with the matter...

Sounds like they aren't too familiar with the names of sensors.

[Yo-Yo]

MCAS is scary.

No, the scary part is realizing that pilots are not being properly trained.

MCAS is not new to the 737 MAX, nor is it exclusive to Boeing. All Airbus aircraft use similar computer-enhanced aircraft handling software, and in fact Airbus aircraft are exclusively "fly-by-wire" which means that ALL control inputs are actually performed by the flight computer. At least the 737 Max still has physical cables and linkages between the control column and control surfaces.

Granted, Boeing could have done a better job writing the MCAS software to automatically disable it if the pilot continues to enter counter trim to what MCAS thinks is appropriate, and Boeing could have tied in both AOA sensors into MCAS from the start, but the bottom line is that things fail in an aircraft, and the pilots need to be trained on how to diagnose and resolve those failures.

There was a giant stabilizer trim wheel right next to the Pilot's right knee, and another right nest to the co-pilot's left knee, that was whizzing very loudly and visibly, adding down trim to the aircraft. It wasn't a secret that down trim was being added automatically to the aircraft.

The autopilot can also enter stabilizer trim commands, so pilots are trained on a procedure to identify and correct for "runaway trim," which is what the pilots failed to properly execute.

[Mr.Unique]

Great video.

[an amused spectator]

“I’m sorry, Hal. I cannot let you disengage the MCAS.”

[pfflier]

There was a giant stabilizer trim wheel right next to the Pilot's right knee, and another right nest to the co-pilot's left knee, that was whizzing very loudly and visibly, adding down trim to the aircraft. It wasn't a secret that down trim was being added automatically to the aircraft.

Thanks for pointing this out. Most laymen think the elevator inputs occur secretly and silently. This is very visible and audible evidence of elevator trim inputs.

In the old days of steam gauges and seat of the pants flying, the pilot used to use this wheel to trim the airplane. Now, more and more are just spectators watching it turn.

[onedoug]

Like Andy Devine trimming his C-47 in “Island In The Sky” (1953).

[faucetman]

Compare this to the “cruise control” in your passenger vehicle.

You turn over maintaining your speed to the computer.

All you have to do to disable it is “step on the brake pedal”. Something that you would instinctively do to prevent say a rear end collision.

You didn’t need to “turn off” the cruise control or have to remember how to do so. You didn’t have to check the owners manual section on the cruise control.

If the car in front of you stopped quickly, would you have time to go through all those steps? CRASH! Likely just a fender bender.

In the pilot’s case it’s LIFE AND DEATH for himself and his crew and his passengers in the hundreds. Can you imagine the pressure/stress?

The pilots need to know what the cause of the problem is AND what to do about it.

They need INFORMATION! They don’t need or want the plane to TAKE OVER!

I no longer fly. If I still did, I would STOP! Pilotless planes is the goal, NOT passenger safety.

[trenton1776]

Something that is often overlooked in this mess is the fact that the Lion Air crash happened 2 or 3 months before this one. Anyone who even casually watched the news learned all about MCAS and how to disable it. Boeing put out a reminder to all pilots on what to do - which is simply to flip those two switches. This “problem” was known to anyone even mildly interested in aviation.

So how it it that these two pilots were overwhelmed and seemingly clueless?

Another mystery I’ve not seen addressed is due to the fact that the “problem” started at only 450ft of altitude. MCAS will not turn on if the flaps are extended or if the autopilot is engaged. So did they fully retract flaps by 450Ft? Were they even extended for takeoff?

Airplanes are made of thousands of parts, any of which could theoretically fail at any time. When one fails, it’s the job of the pilots to react correctly. In this case, I don’t think they did.

[snoringbear]

“ Might be worth it to hire actual experienced pilots to program these things.”

Might be worth it to require more than 200 hrs training.

[Revel]

Unless the off switches physically cut the power to this system then the software is still in control, and a glitch in the software could cause this.

The same goes for all of those who love there push button start on Automobiles. Only the old ignition switches gave the driver absolute control of power to the ignition.