Plato90s

What difference would this make given the information to date is that the MCAS system took its reading from a single AoA sensor?

I haven't seen any indication that the MCAS software (as of now, pre-patch) would/could change its sensor feed based on a condition of "failed". If MCAS has that functionality, I'd be interested in seeing any report/coverage people have seen.

LarryJ

A big unanswered question since the Ethiopian accident is why would two AoA vanes/sensors fail in such a short timespan. Every airliner has AoA vanes and they rarely fail.

The data released today suggests that the AoA malfunctioned shortly after takeoff which suggests something hit it. Ethiopian said that it wasn't a bird strike. We'll have to wait for more definitive data to know.

Plato90s

Unless the AoA sensor was so badly damaged as to cease to generate data, nothing in the thus-far released info suggests that MCAS would start utilizing data from the other AoA sensor.

In that sense, it doesn't make any difference what happened to the 2nd sensor.

The MCAS automation software was triggered by bad data being fed from a single source, and every bit of information released to date suggests that Boeing didn't even have a rudimentary sense of safety/redundancy when it came to the design of this piece of software.



I'm not a pilot or involved in aviation except as a passenger.

I do have extensive experience with automation software, enterprise software, monitoring software, etc... That's why my view is that Boeing bears primary responsibility for the death of 350+ people because this MCAS software was either designed by a team of morons unaware of the basic principles of redundancy, or there was some non-technical manager who decided to go cheap (or worse - profit by selling safety features as pay-for-play) by ignoring those basic principles of software.

This kind of software should NEVER have made it past a QA team.

serfty

Ethiopia Says Pilots Performed Boeings Recommendations To Stop Doomed Aircraft From Diving Urges Review Of 737 Max Flight Control System | Washington Post

serfty

The Preliminary report (Full) can be found here: http://www.ecaa.gov.et/documents/204...8-d7af1ee17f3e

Here is a Timeline:

• At 05:38:00 Take off roll commenced
• At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in ¾ seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.
• At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.
• At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the flaps were retracted and the pitch trim position decreased to 4.6 units.
• At 05:39:45, Captain requested flaps up and First-Officer acknowledged. One second later, flap handle moved from 5 to 0 degrees and flaps retraction began.
• At 05:39:55, Autopilot disengaged,
• At 05:39:57, the Captain advised again the First-Officer to request to maintain runway heading and that they are having flight control problems.
• At 05:40:00 shortly after the autopilot disengaged, the FDR recorded an automatic aircraft nose down (AND) activated for 9.0 seconds and pitch trim moved from 4.60 to 2.1 units. The climb was arrested and the aircraft descended slightly.
• At 05:40:03 Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.
• At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
• At 05:40:20, approximately five seconds after the end of the ANU stabilizer motion, a second instance of automatic AND stabilizer trim occurred and the stabilizer moved down and reached 0.4 units.
• At 05:40:27, the Captain advised the First-Officer to trim up with him.
• At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.
• At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.
• At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position
• At 05:40:44, the Captain called out three times “Pull-up” and the First-Officer acknowledged.
• At 05:40:50, the Captain instructed the First Officer to advise ATC that they would like to maintain 14,000 ft and they have flight control problem.
• From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position. The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left. The data indicates that aft force was applied to both columns simultaneously several times throughout the remainder of the recording.
• At 05:41:20, the right overspeed clacker was recorded on CVR. It remained active until the end of the recording.
• At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.
• At 05:41:32, the left overspeed warning activated and was active intermittently until the end of the recording.
• At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try.
• At 05:41:54, the First-Officer replied that it is not working.
• At 05:42:54, both pilots called out “left alpha vane”.
• At 05:43:04, the Captain asked the First Officer to pitch up together and said that pitch is not enough.
• At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.
• At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.
• The left Indicated Airspeed increased, eventually reaching approximately 458 kts and the right Indicated Airspeed reached 500 kts at the end of the recording. The last recorded pressure altitude was 5,419 ft on the left and 8,399 ft on the right

Stewie Mac

Am I right in thinking that this procedure is exactly what Boeing mandate, and all the pilots here agree, is the correct procedure in this instance (MCAS erroneous activation or any stabiliser runaway)?

In which case, I can't write what I'm thinking, as FT would censor it but.... f

DenverBrian

And the Ethiopian pilots apparently performed the existing runaway stabilizer procedure. And crashed anyway.

This is a cluster.

LarryJ

They cutout the electric stab trim after they had allowed MCAS to run the stab trim to nearly the full nose-down position without countering it (~40sec), and retrimming it, with the primary electric trim. They then turned it back on, which the procedure specifically forbids, and let it drive the stab trim the rest of the way to the full nose-down position.

We know that the primary electric trim works in practice, not just in theory, from the Lion Air DFDR data. That Captain was able to keep the airplane in-trim through 21 MCAS activations, and several minutes, by using the primary electric trim.

DenverBrian

You're becoming the lone voice blaming the pilots here.

chipmaster

It too how long for the CEO to issue an apology and fall on his sword, wonder why he needed to wait till it was obviously BA's issue. He talks about safety first, LOL

Plato90s

That's like saying that a car crash would not have killed everyone on board if the driver had the same skill level as the drivers appointed by Secret Service to drive the president of the United States around.



Technically true, but extremely unfair to the driver (or pilot).

Boeing never should have allowed a software to be deployed that put the Lion Air and Ethiopian Air pilots into the position they were put in.

MSPeconomist

chipmaster

The issue I see is that BA should be creating a system; controls, software, training that is reasonably capable to the lowest skilled pilot they likely will get. Of course no system is foolproof, there is a reason pilots are supposed to have thousands of hours and such before they get such an airplane and the lives of hundreds in their hands.

Clearly many flights have takenoff and landed in less than ideal conditions but it is exactly this kind of thing that quality/reliability engineers are paid for, sadly they got an F

osamede

One has to wonder if Boeing is also running a propaganda army.

peasant

https://www.nytimes.com/2019/04/08/b...-737-max-.html

Boeing’s 737 Max: 1960s Design, 1990s Computing Power and Paper Manuals

My opinion - FAA & Boeing pushed 'derivative' grandfather certification too far. If the MAX was a clean sheet design, it wouldn't be allowed (and, to be fair, Boeing wouldn't ever produce a MAX as a clean sheet design - it would be much more like a larger A220/ smaller B787)

As to the 'blame the pilots' - they were certified & trained as per Boeing/ ICAO standards, and in both cases, sure, someone absolutely on the ball, and aware of all the issues, making the right decisions could have saved the aircraft. But Sully failed as well from that POV (pilots in the simulator could land his aircraft safely back, rather than ditching) Ironically, the Boeing AD after the Lion crash may have meant that the ET flight crashed sooner - they were so concerned about MCAS and trim that they didn't cut speed (which may have put them slow enough that manually hauling the stabiliser would be easier. But that is back seat driving)

End of the day, if this arcraft requires Sully like levels of experience & skill to fly safely, well, Airbus A320 and A220 sales engineers will have a very easy time. Aviation is growing so fast outside the US, that needing wise greybeards isn't going to cut it