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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:28 pm

morrisond wrote:
speedbored wrote:
morrisond wrote:
The report actually looks quite comprehensive however it conveniently doesn't talk about the last few minutes of the flight when DOWN electric trim was recorded.

But that is automatic down trim. And it is mentioned in the report.


Which could only have been activated if they had turned the Electric Trim back on - which the Boeing Bulletin specifically says not to do.

Perhaps but they probably decided that the checklist was worthless at the point where it says use the manual trim wheel, and it didn't work.

You keep criticising the pilots for not following the checklists to the letter. Well, alongside following the unreliable airspeed checklist, and the runaway trim checklist, and the AD, and fighting the controls, they also had terrain warnings and stick shakers to distract them. And not very many seconds in which to handle all of this. You seem to be totally forgetting that pilots are human and there are limits to what a human can achieve in such a short space of time.
 
VV
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:35 pm

ContnlEliteCMH wrote:
VV wrote:
Reading the comments above I became confused.

Were the switches flipped off or were they on?

Is flipping the switch back on part of the procedure?


The report does not state the position of the trim cutout switches. Per the checklist, the system should not be reenabled.


So I am confused by some press articles that mention the pilot tried repeatedly the procedure.

Thanks for the information. That's enough for me today.
I will wait until the final report is issued next year.
 
mzlin
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:36 pm

The listing of events is a short read. I'll post it here to save others trouble and so we can have an informed discussion. If everybody could read this BEFORE posting any questions or comments, that would be nice.

1.1 HISTORY OF FLIGHT
On March 10, 2019, at about 05:44 UTC1, Ethiopian Airlines flight 302, a Boeing 737-8 (MAX), Ethiopian registration ET-AVJ, crashed near Ejere, Ethiopia, shortly after takeoff from Addis Ababa Bole International Airport (HAAB), Ethiopia. The flight was a regularly scheduled international passenger flight from Addis Ababa to Jomo Kenyatta International Airport (HKJK), Nairobi, Kenya. There were 157 passengers and crew on board. All were fatally injured, and the Aircraft was destroyed.
The following is based on the preliminary analysis of the DFDR, CVR and ATC communications. As the investigation continues, revisions and changes may occur before the final report is published.
At 05:37:34, ATC issued take off clearance to ET-302 and to contact radar on 119.7 MHz.
Takeoff roll began from runway 07R at a field elevation of 2333.5 m at approximately 05:38, with a flap setting of 5 degrees and a stabilizer setting of 5.6 units. The takeoff roll appeared normal, including normal values of left and right angle-of-attack (AOA). During takeoff roll, the engines stabilized at about 94% N1, which matched the N1 Reference recorded on the DFDR. From this point for most of the flight, the N1 Reference remained about 94% and the throttles did not move. The N1 target indicated non data pattern 220 seconds before the end of recording. According to the CVR data and the control column forces recorded in DFDR, captain was the pilot flying.
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 3⁄4 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 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.
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 05:38:58 and about 400 ft radio altitude, the flight director pitch mode changed to VNAV SPEED and Captain called out “Command” (standard call out for autopilot engagement) and an autopilot warning is recorded.
At 05:39:00, Captain called out “Command”.
At 05:39:01 and about 630 ft radio altitude, a second autopilot warning is recorded.
At 05:39:06, the Captain advised the First-Officer to contact radar and First Officer reported SHALA 2A departure crossing 8400 ft and climbing FL 320.
Between liftoff and 1000 ft above ground level (AGL), the pitch trim position moved between 4.9 and 5.9 units in response to manual electric trim inputs. At 1000 ft AGL, the pitch trim position was at 5.6 units.
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.
Six seconds after the autopilot engagement, there were small amplitude roll oscillations accompanied by lateral acceleration, rudder oscillations and slight heading changes. These oscillations continued also after the autopilot was disengaged.
At 05:39:29, radar controller identified ET-302 and instructed to climb FL 340 and when able right turns direct to RUDOL and the First-Officer acknowledged.
At 05:39:42, Level Change mode was engaged. The selected altitude was 32000 ft. Shortly after the mode change, the selected airspeed was set to 238 kt.
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 05:39:50, the selected heading started to change from 072 to 197 degrees and at the same time the Captain asked the First-Officer to request to maintain runway heading.
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 05:40:05, the First-Officer reported to ATC that they were unable to maintain SHALA 1A and requested runway heading which was approved by ATC.
At 05:40:06, left and right flap position reached a recorded value of 0.019 degrees which remained until the end of the recording.
The column moved aft and a positive climb was re-established during the automatic AND motion.
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.
From 05:40:23 to 05:40:31, three Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.
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 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
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.
At 05:40:56, the First-Officer requested ATC to maintain 14,000 ft and reported that they are having flight control problem. ATC approved.
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 05:41:21, the selected altitude was changed from 32000 ft to 14000 ft.
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 05:42:10, the Captain asked and the First-Officer requested radar control a vector to return and ATC approved.
At 05:42:30, ATC instructed ET-302 to turn right heading 260 degrees and the First-Officer acknowledged.
At 05:42:43, the selected heading was changed to 262 degrees.
At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.
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 13,400 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.
Last edited by mzlin on Thu Apr 04, 2019 5:43 pm, edited 1 time in total.
 
MSPNWA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:36 pm

XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Unfortunately that's not confirmation they flipped the cut-offs, only an assumption. We need FDR data for confirmation of the switch position. That piece is missing. It's inferred later here "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", however. Strange how they wrote the report.
Last edited by MSPNWA on Thu Apr 04, 2019 5:38 pm, edited 1 time in total.
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:37 pm

morrisond wrote:
PlaneInsomniac wrote:
morrisond wrote:

No - no one will know anything unless the FDR traces are released. You can't treat the Ethiopian report as Gospel.


The preliminary offical investigation report is far and away the best source we have at the moment.

All you have OTOH is wishful thinking. You should really stop trying to impose arbitrary standards of proof on others because the facts keep disagreeing with your world view. It's getting embarrassing to watch.



The report actually looks quite comprehensive however it conveniently doesn't talk about the last few minutes of the flight when DOWN electric trim was recorded.


I think we'd all like to know where you read about these last minutes and down electric trim being applied?

This can be paired with you previously thinking the plane was only in the air 40 seconds. You clearly have decided what happened, even though you have some of the most basic of the facts of the flight wrong. That is not how investigations work thank god.

As for flicking the switch back on, well the plane was uncontrollable with the control columns so what choice did they have? Especially in an area of rising terrain elevation, they probably had the choice of not turning the trim on and definitely flying into terrain, or turning the trim on and MCAS quite possibly flying them into terrain. Poor poor guys.

They may not have performed perfectly and we will know more in due course but they certainly don't appear inept and given the perfect storm of things going wrong immediately after takeoff at a high altitude airport, with rising terrain in the flight path, anyone claiming they could definitely have handled it is deluding themselves.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:38 pm

XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Correct. We only know the stab trim cutout was done based on what the crew said, not by any direct evidence cited in the preliminary report. When they switched it back on later they didn't say anything at all (that's referenced in the report anyway). We only know they switched it back on by they fact that the report says the stab moved in response to their ANU trimming.
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scbriml
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:46 pm

hivue wrote:
XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Correct. We only know the stab trim cutout was done based on what the crew said, not by any direct evidence cited in the preliminary report. When they switched it back on later they didn't say anything at all (that's referenced in the report anyway).


It's right there in the report - "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"
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Exeiowa
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:49 pm

Can we at least all agree the data is consistant with a damaged AoA sensor during or shortly after, take off, probably from an impact with an object.
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:49 pm

So to sum up the key action of the pilots as compared to the checklist.

- They did trim up to counter the MCAS movement before hitting the trim cutout switch.
- They did try to use manual trim as the procedure states when they still couldn't control the aircraft.
- Manual trim didn't work.

What exactly could they have done except reengage electric trim at this point? Note the checklist has now ended. The same checklist various posters insisted the pilots obviously hadn't followed.
 
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PixelFlight
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:51 pm

MSPNWA wrote:
XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Unfortunately that's not confirmation they flipped the cut-offs, only an assumption. We need FDR data for confirmation of the switch position. That piece is missing.

We have yet to see at least a single 737 FDR record with the position of the switches to be certain that this information ever exists. It's possible that this is not the case.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
mzlin
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:52 pm

To me the events seem to confirm what I posted above, that the pilots almost DID save the flight. I do believe their efforts were professional and heroic. Sadly it also appears they could have saved the flight too. Let me explain below.

At some point between 5:41:46 [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.] and 5:43:11 [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.], the stab cutout switches were returned to the active position. This is clear because manual electrical trim inputs in the up (ANU) direction were able to move the stabilizer up.

However, the final event was MCAS issuing AND down inputs to the electrical trim system to move the stabilizer down: "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." And sadly that was the final event.

That the AND inputs were MCAS-issued seems pretty clear as they began 5 seconds after the last manual electric trim input.

What's unfortunate is that there were no further manual electrical trim inputs to counter the nose-down effect of MCAS after 5:43:20, but clearly the manual electrical trim was functional as it was working at 5:43:11, and the stabilizer even moved in response to those manual inputs at 5:43:11. So it appears neither pilot made inputs to counteract MCAS from the moment it started again at 5:43:20 to the end of the flight. Recall at that point they were at 13000 feet so they did have some time to react.

What's doubly odd is there was no callout by either pilot asking or confirming reactivation of electrical trim power. There was also no callout or confirmation of the use of manual electrical trim. So it makes me wonder if one pilot reactivated electrical trim without notifying the other, and if the same pilot also did not realize that they would then have to counter MCAS with manual electrical trim. This may then be very much like the Lion Air situation where the caption countered MCAS with manual electrical trim to keep neutral trim 20 times, then passed control over to the FO, who then only countered MCAS with single manual inputs which were insufficient to keep trim at neutral, allowing MCAS to push trim to the fully down position.

I think they could have saved the plane if they had continued to use manual electrical trim (the thumb switches on the column) at 5:43:20. Recall they were able to reach altitude of 13400 feet at 5:43:11 when the electrical trim had been (mysteriously) reactivated. Although MCAS was reactivating as well, I am guessing they had enough altitude that they could have kept the plane level by using the manual electrical trim to counteract MCAS.

By the way someone asked how the flight manual/checklist could suggest applying manual trim before and after cutout. I think manual trim before cutout means manual electrical trim, whereas after cutout means using the wheels. It's confusing and it would have been better for the manual to define those two types of pilot-inputted adjustments differently. For example, this prelim report uses the term "manual electrical trim" which is unambiguous.
Last edited by mzlin on Thu Apr 04, 2019 5:56 pm, edited 1 time in total.
 
patplan
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:55 pm

ET-AVJ Preliminary Accident Report, pp26-27

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Image
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Finn350
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:57 pm

MSPNWA wrote:
XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Unfortunately that's not confirmation they flipped the cut-offs, only an assumption. We need FDR data for confirmation of the switch position. That piece is missing. It's inferred later here "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", however. Strange how they wrote the report.


Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.
 
patplan
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:58 pm

ET-AVJ Preliminary Accident Report
Maintenance Log, pp 19-20


Image
Image
 
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Pellegrine
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:00 pm

The first wrongful death lawsuit has been filed against Boeing, ET, and Rosemount Aerospace. I hope they get at least 10 million for this young lady's life.

https://www.cnn.com/2019/04/04/us/ethio ... index.html
We fly JETS, we don't fly donkeys.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:13 pm

Exeiowa wrote:
Can we at least all agree the data is consistant with a damaged AoA sensor during or shortly after, take off, probably from an impact with an object.


No. Read the preliminary report. The crew refer to an iced AoA vane.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
ltbewr
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:13 pm

We must all understand this is a preliminary report, but it does give us some idea of the difficult and terrifying situation the plane was in. I wonder if what happened with this flight are similar as with the Lion Air crash and reported close calls or something different.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:14 pm

scbriml wrote:
hivue wrote:
XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Correct. We only know the stab trim cutout was done based on what the crew said, not by any direct evidence cited in the preliminary report. When they switched it back on later they didn't say anything at all (that's referenced in the report anyway).


It's right there in the report - "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"

The gamers will probably require time stamped cockpit video and finger print recognition as part of the FDR package.
 
MSPNWA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:16 pm

Finn350 wrote:
Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.


That's disappointing. I was assuming that would be recorded. Well, we can infer they were shutoff and then turned back on by the rest of the info.
Last edited by MSPNWA on Thu Apr 04, 2019 6:16 pm, edited 1 time in total.
 
oschkosch
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:16 pm

So do I see it correctly that the flaps were retracted but Mcas then self-activated?

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hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:17 pm

MSPNWA wrote:
Unfortunately that's not confirmation they flipped the cut-offs, only an assumption.


It's not an assumption. It is inferred from, "...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"

But note the "consistent with." It could be consistent with other things as well.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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ikolkyo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:18 pm

oschkosch wrote:
So do I see it correctly that the flaps were retracted but Mcas then self-activated?

Gesendet von meinem SM-G950F mit


MCAS is only active when flaps are up.
Last edited by ikolkyo on Thu Apr 04, 2019 6:19 pm, edited 1 time in total.
 
frequentflyr91
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:19 pm

So do we know why MCAS self-activated itself?
 
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litz
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:20 pm

speedbored wrote:
morrisond wrote:
The report actually looks quite comprehensive however it conveniently doesn't talk about the last few minutes of the flight when DOWN electric trim was recorded.

But that is automatic down trim. And it is mentioned in the report.


The report quite clearly states that DOWN electric trim was automatically commanded (presumably by MCAS) ... and that the stabilizer did not move due to the cutout switches being engaged
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:21 pm

One thing that's curious to me is that the AT apparently was set to a "thrust" mode and not a "speed" mode and not altered for the entire flight. I assume the thrust set would be OK for a climb, but they were never really climbing. One airspeed indicator apparently reached 500 kts IAS, and the other also reached a very high reading.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:24 pm

frequentflyr91 wrote:
So do we know why MCAS self-activated itself?


It "self-activated" due to erroneous AoA data. The preliminary report provides NO evidence that MCAS "self-activated" in the sense that it was able to move the stab even when there was no electricity going to the stab trim motor.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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litz
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:25 pm

ikolkyo wrote:
oschkosch wrote:
So do I see it correctly that the flaps were retracted but Mcas then self-activated?

Gesendet von meinem SM-G950F mit


MCAS is only active when flaps are up.


And that's the saddest thing of all right there ... both of these crashes would never have happened had the crew simply re-extended the flaps,and returned for an emergency landing.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:28 pm

hivue wrote:
Exeiowa wrote:
Can we at least all agree the data is consistant with a damaged AoA sensor during or shortly after, take off, probably from an impact with an object.


No. Read the preliminary report. The crew refer to an iced AoA vane.

No. The report refers to a master caution anti-ice warning and an AoA vane heat parameter change. This could, IMO, also be consistent with a damaged sensor.

The deviations seen on the faulty sensor from (roughly) -5 to +60 degrees compared to the other sensor would also suggest damage. I can't see how the sensor icing up would cause such a large deflection so quickly, if at all.
 
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ikolkyo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:29 pm

litz wrote:
ikolkyo wrote:
oschkosch wrote:
So do I see it correctly that the flaps were retracted but Mcas then self-activated?

Gesendet von meinem SM-G950F mit


MCAS is only active when flaps are up.


And that's the saddest thing of all right there ... both of these crashes would never have happened had the crew simply re-extended the flaps,and returned for an emergency landing.


I had the same thought but in that moment with a plane trying to nose dive itself at high speeds, flaps aren’t going to be on the mind. These accidents are extremely upsetting with how poorly implemented MCAS was.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:30 pm

litz wrote:
And that's the saddest thing of all right there ... both of these crashes would never have happened had the crew simply re-extended the flaps,and returned for an emergency landing.


The ET crew could not have deployed flaps at the kinds of airspeeds they were traveling. As I said in a post up-thread, it looks like they were caught in an awful trap. How much of that was due to MCAS and how much to crew actions is yet to be determined.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:33 pm

litz wrote:
speedbored wrote:
morrisond wrote:
The report actually looks quite comprehensive however it conveniently doesn't talk about the last few minutes of the flight when DOWN electric trim was recorded.

But that is automatic down trim. And it is mentioned in the report.


The report quite clearly states that DOWN electric trim was automatically commanded (presumably by MCAS) ... and that the stabilizer did not move due to the cutout switches being engaged

But that is referring to the command at ~5:40:45 (which is very clearly labelled on the graph) morrisond was referring to the down trim command near the end of the flight at ~5:43:20
 
VV
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:34 pm

I stumbled upon this article. Perhaps it is already posted.

https://www.nytimes.com/interactive/201 ... ckpit.html
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:34 pm

hivue wrote:
One thing that's curious to me is that the AT apparently was set to a "thrust" mode and not a "speed" mode and not altered for the entire flight. I assume the thrust set would be OK for a climb, but they were never really climbing. One airspeed indicator apparently reached 500 kts IAS, and the other also reached a very high reading.


How much do you reduce thrust by? You're close to ground with unreliable airspeed readings and stick shaker. As far as I know there are no figures in the manual for thrust with unreliable airspeed at low level if you can't climb. So how comfortable would you feel reducing thrust close to ground with no reference for what it should be?

To add, this rather highlights the absolute catastrophically bad design philosophy here. MCAS' reaction to AoA failure forces you to deactivate a key element of your pitch control in unreliable airspeed situations close to ground. That is a death trap by design. Did Boeing ever actually test this thing in anything other than normal operation?
Last edited by Planetalk on Thu Apr 04, 2019 6:37 pm, edited 1 time in total.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:34 pm

hivue wrote:
Exeiowa wrote:
Can we at least all agree the data is consistant with a damaged AoA sensor during or shortly after, take off, probably from an impact with an object.


No. Read the preliminary report. The crew refer to an iced AoA vane.

Fake news and you know it me-laddo.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:35 pm

speedbored wrote:
hivue wrote:
Exeiowa wrote:
Can we at least all agree the data is consistant with a damaged AoA sensor during or shortly after, take off, probably from an impact with an object.


No. Read the preliminary report. The crew refer to an iced AoA vane.

No. The report refers to a master caution anti-ice warning and an AoA vane heat parameter change. This could, IMO, also be consistent with a damaged sensor.

The deviations seen on the faulty sensor from (roughly) -5 to +60 degrees compared to the other sensor would also suggest damage. I can't see how the sensor icing up would cause such a large deflection so quickly, if at all.


Ah, I see. Good point. Thanks.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:44 pm

Planetalk wrote:
hivue wrote:
One thing that's curious to me is that the AT apparently was set to a "thrust" mode and not a "speed" mode and not altered for the entire flight. I assume the thrust set would be OK for a climb, but they were never really climbing. One airspeed indicator apparently reached 500 kts IAS, and the other also reached a very high reading.


How much do you reduce thrust by? You're close to ground with unreliable airspeed readings and stick shaker. As far as I know there are no figures in the manual for thrust with unreliable airspeed at low level if you can't climb. So how comfortable would you feel reducing thrust close to ground with no reference for what it should be?

To add, this rather highlights the absolute catastrophically bad design philosophy here. MCAS' reaction to AoA failure forces you to deactivate a key element of your pitch control in unreliable airspeed situations close to ground. That is a death trap by design. Did Boeing ever actually test this thing in anything other than normal operation?


I agree those are valid points. I'm thinking that the thrust setting accounts for the dangerously high airspeeds. But you're right, even if the crew realized this they may have been reluctant to do anything about it given the whole situation.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
WorldFlier
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:45 pm

hivue wrote:
litz wrote:
And that's the saddest thing of all right there ... both of these crashes would never have happened had the crew simply re-extended the flaps,and returned for an emergency landing.


The ET crew could not have deployed flaps at the kinds of airspeeds they were traveling. As I said in a post up-thread, it looks like they were caught in an awful trap. How much of that was due to MCAS and how much to crew actions is yet to be determined.


What is the maximum airspeed for which you can deploy minimum flaps?
 
2175301
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:47 pm

Condolences to the families of all involved: Here is my understanding of what happened.

1) The pilots correctly cut out electric trim controls; at which point they could manually fly the aircraft in a somewhat stable configuration, and apparently were doing so with difficulties.

2) Key difficulty is that they were already over the speed envelope of the aircraft - which made manual trim control very difficult (if not impossible).

A likely - although unnatural solution would have been to reduce thrust and slow the aircraft down - and sacrifice altitude in the process to regain usability of the manual trim. Given they were at about 14,000 ft already that would be a scary thought; not to mention all the other distractions in the cockpit at the time. Unless you trained repeatedly in how to slow an aircraft down that was above flight envelope speed this would not likely occur to the pilots.

3) The evidence strongly suggest that they re-powered the electric trim in an attempt to regain control as they then imputed manual electric trim commands that worked... and an automatic MCAS trim down command also worked - which put the aircraft into a final dive.

The full report may identify other things and will likely identify other factors. While some may claim that the aircraft was saveable with manual flying (it likely was with the right person who innately understood some things); I would not expect an average pilot to have figured out to slow the aircraft down and sacrifice altitude to allow manual trim wheels to work again; especially in the time allowed.

Keep in mind that Sully was a very experienced glider pilot and was used to non-powered landings. He innately did some things that most pilots would not.

Have a great day,
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:55 pm

Also worth noting, given how he was slandered on here, that the FO seems to have performed well throughout and it was he that called out 'Trim cutout'. One poster who had said some particularly nasty things about him on another popular flying forum has already issued a Mea Culpa and acknowledged he performed admirably.
 
B777LRF
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:59 pm

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 05:40:05, the First-Officer reported to ATC that they were unable to maintain SHALA 1A and requested runway heading which was approved by ATC.
At 05:40:06, left and right flap position reached a recorded value of 0.019 degrees which remained until the end of the recording.
The column moved aft and a positive climb was re-established during the automatic AND motion.
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.


And there you have it. 20 seconds from 4.6 to 0.4 units. That's how you make a deathtrap.

Rip the damn contraption out of the aircraft, find a way to restore an acceptable level of stability and stall behaviour through natural aerodynamic means, accept it's going to fly differently and to hell with the common type rating.

This is not your grandfather's 737.
Signature. You just read one.
 
Jetty
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:00 pm

PixelFlight wrote:
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 3⁄4 seconds while the right AOA reached a maximum value of 15.3°.

Which shows that the plane didn't even need to compare the 2 AoA sensors to establish a malfunction. Such quick changes are impossible and should never be relied upon to automatically adjust the trim in any decently designed plane even with only 1 sensor present. And if one AoA sensor provides logical outputs and the other does not it should have been plain obvious to rely on the sensor that makes sense, no need to disable MCAS in that scenario as Boeing is planning to do with the software update.
 
Eyad89
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:01 pm

2175301 wrote:
Condolences to the families of all involved: Here is my understanding of what happened.

1) The pilots correctly cut out electric trim controls; at which point they could manually fly the aircraft in a somewhat stable configuration, and apparently were doing so with difficulties.

2) Key difficulty is that they were already over the speed envelope of the aircraft - which made manual trim control very difficult (if not impossible).

A likely - although unnatural solution would have been to reduce thrust and slow the aircraft down - and sacrifice altitude in the process to regain usability of the manual trim. Given they were at about 14,000 ft already that would be a scary thought; not to mention all the other distractions in the cockpit at the time. Unless you trained repeatedly in how to slow an aircraft down that was above flight envelope speed this would not likely occur to the pilots.

3) The evidence strongly suggest that they re-powered the electric trim in an attempt to regain control as they then imputed manual electric trim commands that worked... and an automatic MCAS trim down command also worked - which put the aircraft into a final dive.

The full report may identify other things and will likely identify other factors. While some may claim that the aircraft was saveable with manual flying (it likely was with the right person who innately understood some things); I would not expect an average pilot to have figured out to slow the aircraft down and sacrifice altitude to allow manual trim wheels to work again; especially in the time allowed.

Keep in mind that Sully was a very experienced glider pilot and was used to non-powered landings. He innately did some things that most pilots would not.

Have a great day,


+1
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:03 pm

2175301 wrote:
Given they were at about 14,000 ft already that would be a scary thought; not to mention all the other distractions in the cockpit at the time.


That's MSL, not AGL.

2175301 wrote:
I would not expect an average pilot to have figured out to slow the aircraft down and sacrifice altitude to allow manual trim wheels to work again; especially in the time allowed.


They did not have sufficient surplus altitude AGL to sacrifice.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
fabian9
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:04 pm

morrisond wrote:
My take on reading the accident report is that the flight was saveable until they turned the Electric Trim back on which reactivated MCAS which due to the high speed they were travelling at they were not able to recover from as the airspeed was excessive.


I can’t find the part of the report that says the electronic trim was switched back on. Could you point me at it?

PS: I posted this question earlier, but I think it got deleted.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:07 pm

Jetty wrote:
PixelFlight wrote:
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 3⁄4 seconds while the right AOA reached a maximum value of 15.3°.

Which shows that the plane didn't even need to compare the 2 AoA sensors to establish a malfunction. Such quick changes are impossible and should never be relied upon to automatically adjust the trim in any decently designed plane even with only 1 sensor present. And if one AoA sensor provides logical outputs and the other does not it should have been plain obvious to rely on the sensor that makes sense, no need to disable MCAS in that scenario as Boeing is planning to do with the software update.

But that would not have helped in the case of the Lionair flight, where both sensors provided readings within the bounds of normality but consistently just over 20 degrees apart.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:08 pm

hivue wrote:
morrisond wrote:
It appears as though they initially flipped them off but then several minutes later they turned them back on.


The preliminary report doesn't state any straight, direct evidence that they switched off the stab trim cutouts. It's inferred that they actually did because of a subsequent AND command to the electrical trim which wasn't answered by actual stab movement. Later, there was a ANU command to the electrical trim (which would not come from MCAS but only from the crew) which was answered by stab movement.


How would the ANU command and the stab movement have been possible unless power was restored to the Electric Trim?
 
mzlin
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:09 pm

2175301 wrote:
Condolences to the families of all involved: Here is my understanding of what happened.

1) The pilots correctly cut out electric trim controls; at which point they could manually fly the aircraft in a somewhat stable configuration, and apparently were doing so with difficulties.

2) Key difficulty is that they were already over the speed envelope of the aircraft - which made manual trim control very difficult (if not impossible).

A likely - although unnatural solution would have been to reduce thrust and slow the aircraft down - and sacrifice altitude in the process to regain usability of the manual trim. Given they were at about 14,000 ft already that would be a scary thought; not to mention all the other distractions in the cockpit at the time. Unless you trained repeatedly in how to slow an aircraft down that was above flight envelope speed this would not likely occur to the pilots.

3) The evidence strongly suggest that they re-powered the electric trim in an attempt to regain control as they then imputed manual electric trim commands that worked... and an automatic MCAS trim down command also worked - which put the aircraft into a final dive.

The full report may identify other things and will likely identify other factors. While some may claim that the aircraft was saveable with manual flying (it likely was with the right person who innately understood some things); I would not expect an average pilot to have figured out to slow the aircraft down and sacrifice altitude to allow manual trim wheels to work again; especially in the time allowed.

Keep in mind that Sully was a very experienced glider pilot and was used to non-powered landings. He innately did some things that most pilots would not.

Have a great day,


So I think one interesting question is why was there no

4) additional upward manual electric trim inputs to counteract downward MCAS inputs

... when the pilots already knew there was a trim problem?After all that time, why not keep an eye on the trim? I suggest they got some safety in attitude and just got distracted by the task of returning to the airport, plus perhaps some miscommunication as I described above and the possibility that electric trim and thus MCAS was reactivated by one pilot without telling the other.
 
hivue
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:11 pm

morrisond wrote:
hivue wrote:
morrisond wrote:
It appears as though they initially flipped them off but then several minutes later they turned them back on.


The preliminary report doesn't state any straight, direct evidence that they switched off the stab trim cutouts. It's inferred that they actually did because of a subsequent AND command to the electrical trim which wasn't answered by actual stab movement. Later, there was a ANU command to the electrical trim (which would not come from MCAS but only from the crew) which was answered by stab movement.


How would the ANU command and the stab movement have been possible unless power was restored to the Electric Trim?


Obviously power was restored by the crew switching stab trim back on. But that's inferred from the preliminary report, not actually stated anywhere.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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BaconButty
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:12 pm

frequentflyr91 wrote:
So do we know why MCAS self-activated itself?

05:39:55, Autopilot disengaged
Down with that sort of thing!
 
Amexair
Posts: 56
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:15 pm

patplan wrote:
ET-AVJ Preliminary Accident Report
Maintenance Log, pp 19-20


Image
Image


This, in and of itself is worrisome about the MAX jet. Are these types of malfunctions even common in other a/c?

2) Poor guys gave it all they possibly could. The fact that they didn't have correct IAS indication of itself is a 50/50 chance of making it. You can only rely on your intuition there, and at 1000ft AGL, forget about it.

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