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

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

Post by sanjet »

ykzrampie wrote: Wed Apr 03, 2019 6:34 am 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.
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Laser Tilt
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by Laser Tilt »

Preliminary report out today says the crew correctly followed all procedures to handle the emergency.
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HavaJava
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by HavaJava »

Laser Tilt wrote: Thu Apr 04, 2019 3:01 am 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?
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tps8903
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by tps8903 »

HavaJava wrote: Thu Apr 04, 2019 4:04 am
Laser Tilt wrote: Thu Apr 04, 2019 3:01 am 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
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BMLtech
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by 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.
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Kaykay
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by Kaykay »

HavaJava wrote: Thu Apr 04, 2019 4:04 am
Laser Tilt wrote: Thu Apr 04, 2019 3:01 am 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.
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tbaylx
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by tbaylx »

BMLtech wrote: Thu Apr 04, 2019 7:36 am 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.
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BMLtech
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by 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."
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BMLtech
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by 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?
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J31
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by 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.
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J31
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by J31 »

tbaylx wrote: Thu Apr 04, 2019 8:14 am
BMLtech wrote: Thu Apr 04, 2019 7:36 am 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.
You flew the B737-500 I believe. Does the quote in the QRH "manual trim forces increase with airspeed" " it make take two pilot force on the manual trim to move the trim wheel" ring any bells.
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sherryfly
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by sherryfly »

http://avherald.com/h?article=4c534c4a
Very detailed report on the incident, please read.
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tbaylx
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by tbaylx »

J31 wrote: Thu Apr 04, 2019 10:05 am
tbaylx wrote: Thu Apr 04, 2019 8:14 am
BMLtech wrote: Thu Apr 04, 2019 7:36 am 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.
You flew the B737-500 I believe. Does the quote in the QRH "manual trim forces increase with airspeed" " it make take two pilot force on the manual trim to move the trim wheel" ring any bells.
I flew the 200, 300 and 800. It's been 5 years since i've flown the classic but that may have been in the QRH. Maybe 737 pilots are going to need to meet a certain physical strength test now on recurrent sims.
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boeingboy
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by boeingboy »

]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 First-Officer 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


Proof that they did cutout the stab and that MCAS will not move when in cutout.

However - it is what happens after this that will be interesting to find out. If wether or not they did turn the system back on.
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BMLtech
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by BMLtech »

sherryfly wrote: Thu Apr 04, 2019 10:40 am http://avherald.com/h?article=4c534c4a
Very detailed report on the incident, please read.
Wow. 500 knots IAS, that must be nearly supersonic, speed would have been quickly beyond flap extend speed.Air loads on the stab would have been massive, and they didn't reduce the power from 94%N1 .. but I suppose keeping the power up is consistent with trying to pitch up.
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sportingrifle
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by sportingrifle »

BML Tech....I think you may be very close to the truth here. Some of the check pilots at my airline gamed it in the sim and ran into just such a situation.

Just speculation on my part, but I am wondering if the knowledge of this scenario is what perhaps caused Boeing/FAA to announce a further delay in the certification of the "fix." The difficulty of returning the trim manually and need to keep the thrust to maintain pitch attitude would open a whole new set of considerations.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by boeingboy »

Come on guys......They airspeed was 250 - 320 kts for most of the flight - it only increased to stuipidly high numbers in the last 5 secs when it nosed over to 40 degrees down.

It actually sounds like they had it mostly under control until that last 2 min or so....I'd really like to know if they turned the system back on. Unfortunately - I don't believe the stab cutout switches are a monitored FDR parameter. They would have to dissect the CVR for the sound of the switches being selected.
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by boeingboy »

Just speculation on my part, but I am wondering if the knowledge of this scenario is what perhaps caused Boeing/FAA to announce a further delay in the certification of the "fix."
I don't know what the extra time required is about - but I know when Boeing held an update for all the regulatory agencies and companies to outline the fixes - EASA didn't even show up! Kinda hard to address your concerns when you don't even participate. The jets are not going to be flying again until everyone signs off on it.

Maybe EASA is just trying to help out Airbus with a few more sales.
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Gino Under
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by Gino Under »

BoeingBoy

You have been quite insistent and smug with your support of Boeing over these accidents and how easy an MCAS event is to deal with. Now that the preliminary report has been released by Ethiopian authorities we hear via press release from Boeing that MCAS was the issue and these two accidents happened despite both accident flight crews following Boeing STAB TRIM RUNAWAY procedures contained in both the MAX FCOM and AD issued in December. I was wondering whether or not you've had an opportunity to reflect on your position now that Boeing state in that same press release that they "own it"?

Gino Under
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LittleNelly
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Re: Ethiopian Airlines: 'No survivors' on crashed Boeing 737 max

Post by LittleNelly »

People seem to be overlooking the fact that the investigators are the OWNERS of the company.. ethiopian is 100% owned by the government of Ethiopia which is an authoritarian regime that ranks as one of the most corrupt in the world.
You can bet the government is directing the investigation clear of their investment.

The fact remains that the trim can be BOTH electronically or manually overridden. And disconnected. The MCAS commanded trim can not override the pilots.


Let's not forget the ECAA in their official report of Egypt air 990 tried to blame flight control problems instead of the obvious pilot suicide that everyone else had determined. Corrupt third world countries have a reputation of skewing reports in their favor.

Wait to see what the NTSB says.
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