Lion Air flight

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#2127864 16-Nov-2018 11:36

networkn:

alasta:

On Airbus aircraft inconsistent pitot, static port and AOA readings usually engage direct or alternate law, which effectively disengages the flight envelope protection.

I would have thought that Boeing would have implemented something similar?

I have no idea what you just wrote :)

Disengaging the anything protection doesn't sound like a good idea :)

It can be a good idea. For instance in a multiple blocked PITOT (airspeed sensor) situation in the climb the Airbus will think it's overspeeding as the altitude increases so will pitch up until the aircraft stalls (it takes a while to do this)

Sim training is all about recognizing and practicing for situations like this.

https://www.atsb.gov.au/publications/investigation_reports/2018/aair/ao-2018-053/

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k1w1k1d

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#2127869 16-Nov-2018 11:53

Interesting article.

Makes me wonder about the pre-flight walk arounds if three 300mm red streamers were not noticed against a white aeroplane???

networkn

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#2127873 16-Nov-2018 11:58

They didn't just miss one either.

PolicyGuy

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#2127877 16-Nov-2018 12:06

empacher48:
From what I’ve read so far is that the appropriate action to prevent the crash is in the manuals the pilots have access to (buried in a book no less than 5,500 pages long), however the situation the crew found themselves in and what they had to do to stop it were not immediately obvious.

No
One of the big issues here is that none of the manuals the pilots (or their airline employers!) had access to mentions this new 737 MAX "feature" - the MCAS.
Details only emerged in a Boeing bulletin after this crash

empacher48:
What they tried to do, and what every pilot in the world has been trained to do in this situation has made the problem worse.

Yes

networkn:
I'm certainly no expert, pilot and so my comments are made from a laypersons perspective, however, if the plane went into a dive, surely "pull up, pull up" would have been screaming at them from the cockpit computer.

The simulation I saw (that admittedly I don't know if accurate" was that the plane went into the ocean nose first at a VERY steep angle. Maybe there just wasn't the height to bring it out of the dive or something.

I would imagine, that if the plane dives, it builds up speed, which if you can get the plane to somewhat of an angle, gets wind under the wings to provide lift.

It's obviously, much more complicated than that, I am just struggling to understand how a plane hits the ocean nose first like that (if the simulation was accurate).

Because of the way the MCAS works, when it got an erroneous Angle of Attack signal, it was automatically - and completely unknown to the pilots - trimming the horizontal stabiliser to push the aircraft nose down.
Because the stabiliser is big, and the elevators that the pilots control directly are relatively small, the pilots cannot pull back (nose up command) hard enough on the elevators even if both are pulling as hard as they can to overcome the nose-down effect of the stabiliser. Technically this is called "insufficient control authority".

There is a good explanation of the MCAS here: https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/

edit to correct spelling & grammar

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#2127888 16-Nov-2018 12:22

tdgeek:

Sounddude:

Goosey:

I always saw many a incident that involved air speed sensors.....

This one seems quite different, as it wasn't in any of the material given to the Airlines for training. Its unique to the MAX model due to its bigger engine sizes which results in a much faster stall speed.

AND, no extra training if you already know the 737.

Not true. They did get training on the differences between the MAX and other 737s. It just didn't cover one (or more?) of the new features; the stability augmentation system.

tdgeek

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#2127890 16-Nov-2018 12:27

empacher48:
sbiddle:

It would seem based on what we know so far that as a result of incorrect data the plane has entered a dive to prevent a stall and the pilots have potentially not taken the appropriate action which would have prevented the crash.

From what I’ve read so far is that the appropriate action to prevent the crash is in the manuals the pilots have access to (buried in a book no less than 5,500 pages long), however the situation the crew found themselves in and what they had to do to stop it were not immediately obvious.

What they tried to do, and what every pilot in the world has been trained to do in this situation has made the problem worse.

There are more questions to ask, and more answers to be uncovered as I believe from what I’ve read, we don’t know everything yet about this.

Not in this case. Its likely they reacted correctly to what was in the manuals, which excluded the new design stall protection. Boeing released that new design via a standard bulletin one week after the crash. Its now going into the manual. They were flying an aircraft that had a redesigned feature that they and every other MAX pilot did not know existed or what the revised procedure is. Its also quite possible that a better pilot as @sbiddle alluded to, might/could do things to react to what was not making sense.

tdgeek

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#2127894 16-Nov-2018 12:33

frankv:

tdgeek:

Sounddude:

Goosey:

I always saw many a incident that involved air speed sensors.....

This one seems quite different, as it wasn't in any of the material given to the Airlines for training. Its unique to the MAX model due to its bigger engine sizes which results in a much faster stall speed.

AND, no extra training if you already know the 737.

Not true. They did get training on the differences between the MAX and other 737s. It just didn't cover one (or more?) of the new features; the stability augmentation system.

Ok, maybe I read too much into this

"Boeing marketed the MAX 8 partly by telling customers it wouldn’t need pilots to undergo additional simulator training beyond that already required for older versions, according to industry and government officials."

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#2127896 16-Nov-2018 12:39

PolicyGuy:
empacher48:
From what I’ve read so far is that the appropriate action to prevent the crash is in the manuals the pilots have access to (buried in a book no less than 5,500 pages long), however the situation the crew found themselves in and what they had to do to stop it were not immediately obvious.

No
One of the big issues here is that none of the manuals the pilots (or their airline employers!) had access to mentions this new 737 MAX "feature" - the MCAS.
Details only emerged in a Boeing bulletin after this crash

empacher48:
What they tried to do, and what every pilot in the world has been trained to do in this situation has made the problem worse.

Yes

networkn:
I'm certainly no expert, pilot and so my comments are made from a laypersons perspective, however, if the plane went into a dive, surely "pull up, pull up" would have been screaming at them from the cockpit computer.

The simulation I saw (that admittedly I don't know if accurate" was that the plane went into the ocean nose first at a VERY steep angle. Maybe there just wasn't the height to bring it out of the dive or something.

I would imagine, that if the plane dives, it builds up speed, which if you can get the plane to somewhat of an angle, gets wind under the wings to provide lift.

It's obviously, much more complicated than that, I am just struggling to understand how a plane hits the ocean nose first like that (if the simulation was accurate).

Because of the way the MCAS works, when it got an erroneous Angle of Attack signal, it was automatically - and completely unknown to the pilots - trimming the horizontal stabiliser to push the aircraft nose down.
Because the stabiliser is big, and the elevators that the pilots control directly are relatively small, the pilots cannot pull back (nose up command) hard enough on the elevators even if both are pulling as hard as they can to overcome the nose-down effect of the stabiliser. Technically this is called "insufficient control authority".

There is a good explanation of the MCAS here: https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/

edit to correct spelling & grammar

Why is mcas needed to push nose down when it is already nose heavy?

frankv

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#2127901 16-Nov-2018 12:54

From that: "Maneuvering Characteristic Augmentation (MCAS) ... is intended to improve pitch response at high angles of attack. It was added to the MAX models partly because the aircraft has heavier engines than the previous 737 NG models and the airplane's center of gravity is biased more forward."

A forward CoG makes the plane more stable (i.e. harder to pitch up or down). So, my reading is that, at high AoA (i.e. close to stall), MCAS will trim the nose down when the stick is pushed forward, and trim nose-up when the stick is pulled back, so that the stick is more effective than otherwise.

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#2127915 16-Nov-2018 13:25

frankv:
See also https://www.avweb.com/avwebflash/news/Pilots-Not-Told-About-737-MAX-Auto-Trim-System-Updated-231846-1.html

From that: "Maneuvering Characteristic Augmentation (MCAS) ... is intended to improve pitch response at high angles of attack. It was added to the MAX models partly because the aircraft has heavier engines than the previous 737 NG models and the airplane's center of gravity is biased more forward."

A forward CoG makes the plane more stable (i.e. harder to pitch up or down). So, my reading is that, at high AoA (i.e. close to stall), MCAS will trim the nose down when the stick is pushed forward, and trim nose-up when the stick is pulled back, so that the stick is more effective than otherwise.

When it first flashed up on my breaking news headlines, i was shocked it was a brand new plane, with good weather and "experienced" pilots, but that the brand new plane has had a history of problems. New is not always better.

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#2127934 16-Nov-2018 14:08

Bring on fully automated transport! Umm, maybe not just yet.

“We’ve arranged a society based on science and technology, in which nobody understands anything about science technology. Carl Sagan 1996

hairy1

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#2127980 16-Nov-2018 14:49

Dingbatt: Bring on fully automated transport! Umm, maybe not just yet.

Everytime there is an article about autonomous aircraft I think about the complexity of the current airliner and procedures.

There are squillions of articles and research on how pilots have made an error resulting in a crash however there is no research on how many accidents pilots have prevented.

There is no way of measuring or estimating what the accident rate would be on an autonomous aircraft. I think about the number of trapped errors (whether by automation or otherwise) that airlines catch every day and I can't see autonomous aircraft happening any time soon.

* Just my opinion. This post is in no way related to the Lion Air crash but about automated transport. *

My views (except when I am looking out their windows) are not those of my employer.

networkn

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#2127982 16-Nov-2018 14:53

I would not willingly board a autonomous aircraft.

I do wonder however, if in this situation, it would have prevented this particular tragedy?

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#2127985 16-Nov-2018 14:57

Dingbatt: Bring on fully automated transport! Umm, maybe not just yet.

I will never get on one that leaves the ground.

alasta

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#2128102 16-Nov-2018 17:34

networkn:

I would not willingly board a autonomous aircraft.

I do wonder however, if in this situation, it would have prevented this particular tragedy?

I doubt it. The sensors that the autonomy would have relied upon were feeding anomalous readings. Therefore the situation required the pilots to react based on factors that were probably outside of the awareness of the aircraft's electronic systems.

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