Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

[tbaylx]

The stab trim cutout switches are checked for position in the first flight, "before start checklist to the line" by every crew, before every first flight of the day every time. They aren't some obscure switches never dealt with unless it's called for in a QRC or NNC. The Captain touches the switches before every first flight of the day.

I’ve never heard of a “before start checklist to the line”. With the Boeing SOP’s the switch position is checked in the captains pre flight flow but not backed up with any checklists.

The Captain calls for the Before start checklist "to the line" after the flows are complete. In our checklist(B737-200 ad 300) we have an item on the checklist for first flight of the day... "Stab trim cutout switches" ... "Normal".

5T uses an SOP based on Westjets rather unique SOP. Outside of those two airlines most others are using Boeing based SOP and don’t use to the line anywhere and have memory items instead of QRC’s.

Like previously mentioned it’s part of the captains Preflight flow and not on any checklist if you’re using Boeing’s SOP like most airlines.

[Eric Janson]

The stab trim checklist is a memory item.....why the hell is everyone flipping through manuals?? Has no-one been drilled in this??

It appears that there may have been multiple failures. Some of which may have masked the trim movement (like a continuously operating Stick Shaker).

A number of ambiguous warning messages will only add to the confusion imho.

I can certainly see how this combination could rapidly overload a crew.


Here's something you can try in the Sim sometime - I used to give this on the Command upgrade Sim (737 Classic).

On descent - dual Generator failure.

The overhead panel lights up like a Christmas tree - hard to isolate the failure. The crew didn't realise what the failure was.

Next session - dual Engine failure on descent.

The overhead panel lights up like a Christmas tree - the crew start doing the dual Generator failure checklist! The indications on the overhead panel are identical. The only differences are 2 low oil pressure lights below the Captain's flight instruments and the indications on the Standby Engine Instrument display. Very easy to miss.

On a more modern Type a Simultaneous Engine Flameout on one side and a Fire indication on the other side will create plenty of issues as the crew follows the Checklist on the screen and shuts off the only engine developing power!

The above scenario happened in real life to a Sabena crew (who managed it correctly).


My point is that I don't believe that the Lion Air or Ethiopian crash was a simple, easily managed event.

[TheStig]

What a obscenely antiquated airplane to still be rolling off the production line.

Eric, I know you're familiar with both Airbus and Boeing products. However, for anyone who wonders about the differences between the two. The same scenarios in an Airbus identified as follows:
Master Warning & Upper ECAM:
ELEC GEN 1 FAIL
ELEC GEN 2 FAIL

ENG 1 FAIL
ENG 2 FAIL

Under those messages are checklists of corrective actions for the Pilot Monitoring to follow, the items are removed from the checklist after they are completed.

Obviously, Airbus' aren't perfect, but you have to wonder how much of Boeing's own 777/787 developed systems are worth omitting in order to keep the common type rating.

[BMLtech]

Now reported that MCAS implicated in Ethiopian crash:
https://www.bbc.com/news/business-47745191

[FICU]

Now reported that MCAS implicated in Ethiopian crash:
https://www.bbc.com/news/business-47745191

The latest media report is saying the nose pitched down at about 450 feet AGL. MCAS is supposed to be inhibited with the flaps extended so unless this crew raised the flaps to zero by 450 feet AGL this doesn't seem like an MCAS problem. Could it be a 200 hour wonder problem in a classic Metro nose dive after take off?

Makes you wonder... no pun intended

[Mick G]

Who is sick of this thread? I know I am. Does this make me a troll for asking?

Consensus please.

[FICU]

Who is sick of this thread? I know I am. Does this make me a troll for asking?

Consensus please.

I think the point of this thread is to discuss the accident.

You have the option of reading, posting, and ignoring.

[BMLtech]

It sounds like they are reporting that for whatever reason, they experienced uncommanded nose down trim. Preliminary report should be out any day.

[J31]

Boeing's fix for 737 MAX will take additional weeks....

https://www.cnn.com/2019/04/01/politics ... index.html

[ykzrampie]

So now MCAS was alive and well even after it (the trim system presumably) was disabled? Rrrrealllly??? Hmmmm

https://www.cbc.ca/news/business/boeing ... -1.5082472

[sanjet]

So now MCAS was alive and well even after it (the trim system presumably) was disabled? Rrrrealllly??? Hmmmm

https://www.cbc.ca/news/business/boeing ... -1.5082472

From what I understand, they re-activated the trim system hence why the MCAS reactivated.

[Laser Tilt]

Preliminary report out today says the crew correctly followed all procedures to handle the emergency.

[HavaJava]

Preliminary report out today says the crew correctly followed all procedures to handle the emergency.

Pretty sure the media have quoted a press release from Ethiopian Airlines on that. I don’t think the report has been released...do you have a source?

[tps8903]

Preliminary report out today says the crew correctly followed all procedures to handle the emergency.

Pretty sure the media have quoted a press release from Ethiopian Airlines on that. I don’t think the report has been released...do you have a source?

If you read the article by the CBC it says they followed the guidance of Boeing. Then it goes on to say that they turned the trim back on (which is not the guidance of Boeing). Sounds like someone is trying to spin this. Either they did, or they did not follow the new checklist. Sounds like they did not by turning the faulty system back on. Pretty hack job reporting as far as the titles go. Should read "Unsure if Ethiopian Crew followed Boeing Procedures"

The crew of the Ethiopian Airlines jet that crashed shortly after takeoff last month performed all of the procedures recommended by Boeing when the plane started to nosedive but could not control it, according to a preliminary report released Thursday by Ethiopia's government.

What also isn't clear is whether the Ethiopian pilots followed Boeing's recommendations to the letter in dealing with the system repeatedly pointing the nose down.

The pilots initially followed Boeing's emergency steps by disconnecting the MCAS system, but for an unknown reason, they turned the system back on, an official familiar with the crash investigation told The Associated Press

https://www.cbc.ca/news/world/ethiopian ... -1.5083960

[BMLtech]

It is very much looking like the ethiopian crew was not able to manually trim the stab nose up due to out of trim aerodynamic forces, which explains why they would have selected the stab trim cut out back to on to attempt to electrically trim up...but MCAS trims down at a faster rate than normal up trim. yikes.

[Kaykay]

Preliminary report out today says the crew correctly followed all procedures to handle the emergency.

Pretty sure the media have quoted a press release from Ethiopian Airlines on that. I don’t think the report has been released...do you have a source?

CNN was saying that on TV this morning. They claimed it was the preliminary report and went on and on about how damning it is for Boeing. Grains of salt needed.

[tbaylx]

It is very much looking like the ethiopian crew was not able to manually trim the stab nose up due to out of trim aerodynamic forces, which explains why they would have selected the stab trim cut out back to on to attempt to electrically trim up...but MCAS trims down at a faster rate than normal up trim. yikes.

MCAS does not override crew electric trim inputs. You can trim the aircraft nose up, but then when you release the trim MCAS activates nose down again and continues to do so until the crew either trims nose up again or disables the trim system.

So if for some reason they were unable to manually trim (never heard of being unable to trim nose up manually due to 'Aerodynamic forces") the crew could use the electric trim to get it close, then use the stab cutout switches to disable MCAS. You may have some out of trim condition still but you'd be close enough to be able to fly it without much effort even without using manual trim.

[BMLtech]

Its being reported that MCAS trims at a faster rate than normal trim, so a one step forward, two steps back scenario. I have also read multiple reports that if the stab is in a severe out of trim condition, manual trim forces become excessive unless the aerodynamic load is relieved by relaxing the elevator input, something that is not possible at low altitude...the sad thing is it would seem that all they needed to do to save it was lower the flaps.

"Industry observers on 3 April also mulled reports that manuals for Boeing's first-generation 737 mentioned that, under certain conditions, pilots might struggle to adjust the stabiliser using the manual trim wheel.

Specifically, that condition might occur when the stabiliser is in a nose-down position while a pilot is pulling back on the column, placing the elevator in a nose-up position and resulting in countering forces.

Pilots interviewed by FlightGlobal said their 737NG and 737 Max flight manuals include no such warnings and that they were unaware such conditions could exist on 737 Classics.

But they wondered whether such a scenario could exist on newer 737 variants, particularly at high speeds, when forces on control surfaces are greater."

[BMLtech]

MCAS does not override crew electric trim inputs. You can trim the aircraft nose up, but then when you release the trim MCAS activates nose down again and continues to do so until the crew either trims nose up again or disables the trim system.

So if for some reason they were unable to manually trim (never heard of being unable to trim nose up manually due to 'Aerodynamic forces") the crew could use the electric trim to get it close, then use the stab cutout switches to disable MCAS. You may have some out of trim condition still but you'd be close enough to be able to fly it without much effort even without using manual trim.
[/quote]

I agree with what you are suggesting, why would they not have been able to electrically trim up, and then immediately shut off the trim, but perhaps this is due to task saturation with other false warnings etc. Here's a question for a Max driver- does the electric column trim switch operate the trim continuously if held, or only for so many seconds?

[J31]

I agree with what you are suggesting, why would they not have been able to electrically trim up, and then immediately shut off the trim, but perhaps this is due to task saturation with other false warnings etc. Here's a question for a Max driver- does the electric column trim switch operate the trim continuously if held, or only for so many seconds?

All Boeing 737 series control column trim switches will continuously trim all the way to the electric trim limits as long as you hold the switches. Normal trim (flaps up) is about 2.5 turns per second and MCAS is about 4 turns per second.

To undo the trim that MCAS did would take almost twice as long. For example: if MCAS trimmed nose down for 5 seconds and you stop it with nose up trim via the control column electric trim, it will take about 8-10 seconds of continuous trimming to return to the original trim setting.