Moderators: jsumali2, richierich, ua900, PanAm_DC10, hOMSaR

 
SimonL
Posts: 56
Joined: Tue Mar 12, 2019 3:38 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:18 pm

As said: With all the attention the MCAS has been given after the Lion Air crash the crew must have been very well aware of it and it was most likely the first that came to their mind. Thats how humans work, with too much attention on a specific issue it might even happen that other issues are interpreted as the first issue if they are similar because you've heard/read so much about it.
 
AngMoh
Posts: 1205
Joined: Fri Nov 04, 2011 5:03 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:19 pm

danj555 wrote:
Couldn't the pilots in any case of malfunction just turn off all electronic bs? Like you're a pilot. You know how to fly a plane. You have flown thousands of take-offs. You know the right speed, right angle, right altitude. You know how to do it without electronic interference if need be.

So why not hit the kill switch if the computer is having a fit?


Isn't that what the AirAsia pilots did just before they smashed into the sea?
 
SuperGT
Posts: 8
Joined: Wed Mar 13, 2019 8:13 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:26 pm

Derico wrote:
Trin wrote:
[

Like you, I am trying to sit here and figure out how this system even came into being let alone got certified. .


Given this sentiment about this system is being echoed my quite a few on the av boards right now, this brings a follow up issue.

Because it already would be concerning enough that an aerospace company designed and approved such a solution, and that one national aviation authority certified it. But obviously all the other major aviation authorities around the world also approved it as safe for real world utilization.

What does this mean? To an outsider like me, this suggests either blind trust in the airplane designer and manufacturer, and or in the national authority that certified it. Otherwise it suggest they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features of new equipment or systems being introduced into the airspace they oversee.

That's puzzling and worrying.


- blind trust in the airplane designer and manufacturer
- or in the national authority that certified it
- they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features

You have hit nail on head so to speak. All of the above, in my view!

Otherwise, there is no other way this madness could happen. As mentioned earlier on this thread, the entire thing stinks of 'politics' now between two or more parties....
Last edited by SuperGT on Fri Mar 15, 2019 2:29 pm, edited 3 times in total.
 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:26 pm

dtw2hyd wrote:
That is just a theory because previous flight didn't crash. It could be just MCAS trim down did not reach a point of no return and crew could recover.

Well true... they didn't wait until MCAS had trimmed full nose down to turn off the electric trim. Doing that would require some expedient hand cranking to get the aircraft back in trim. Never the less.... the PIC noticed that the aircraft was trimming down after every SIC trim up, so he turned off electric trim. Later in the climb, the PIC turned electric trim back on and the nose down trim started again, so the PIC turned off electric trim for the remainder of the flight.

SomebodyInTLS wrote:
You forgot to add "by luck"! They had no idea what was going on but happened to guess correctly that trim could be involved. THERE WAS NO PROCEDURE.

By luck? Guess? Give me a break. The pilot was able to troubleshoot a problem and was able to apply a known procedure (runaway electric trim) to another problem (uncommanded electric trim).
From the preliminary report:
While handling the problem, the PIC instructed the SIC to continue acceleration and flap retraction as normal. The PIC commanded the SIC to follow FD command and re-trim the aircraft as required. The PIC noticed that as soon the SIC stopped trim input, the aircraft was automatically trimming aircraft nose down (AND).
After three automatic AND trim occurrences, the SIC commented that the control column was too heavy to hold back.
The PIC moved the STAB TRIM switches to CUT OUT and manually trimmed.
The PIC re-engaged the STAB TRIM switches to NORMAL, but almost immediately the problem re-appeared. The PIC then moved the STAB TRIM switches back to CUT OUT and continued with manual trim without auto-pilot until the end of the flight.
 
GalaxyFlyer
Posts: 9273
Joined: Fri Jan 01, 2016 4:44 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:30 pm

If the stick shaker activates due to the same erroneous AOA data that started the MCAS operation, shutting off the stab trim probably won’t stop the shaker. That now poses a problem, flying the plane with the shaker going. Very abnormal, possible difficult and, if tripping breakers is required to stop it, possibly taking time. I just thought that part thru, the BBD products I also flew has stall warn switches in front of each pilot, turn either off disarmed the system.

GF
 
User avatar
PW100
Posts: 4126
Joined: Mon Jan 28, 2002 9:17 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:32 pm

edu2703 wrote:
Investigators found piece of stabilizer with trim in unusual position similar to doomed Lion Air jet, according to airlive.net.


We are all focusing on MCAS, but could any other system be a cause of that? That raises the question, which systems can manipulate stabilizer trim?

Per following link, slide 44 and further

1) Pilots: manual control through hand-turning trim wheel (connected through old-fashioned cables and pulleys to elevator jack screw, both NG and MAX series);
2) Pilots: per electric trim switches on yoke controlling electric trim motor, located at stabilizer jackscrew (both NG and MAX series);
3) Autopilot: through electric trim motor (both NG and MAX series);
4) STS - Speed Stability System: through electric trim motor (both NG and MAX series);
5) MCAS - Maneuvering Characteristics and Augmentation System: through electric trim motor (supposedly only when flaps are fully retracted, and autopilot off). Unique for Max series.
6) . . . . any other system I might have missed . . . ?

NOTE 1: link applies to 737NG, which would be the same for NG and Max, except for MCAS.
NOTE 2: trim change through electric motor movement is fed back to trim wheel (mechanically, through above mentioned cables and pulleys), so all trim corrections made by whoever/whatever are visible (and audible) to both pilots in the form of trim wheel turning and associated clacks.

Is it feasible that other systems might be at play? Or even systems working against each other?

So why did two 737 crashes in short time succession, both involved MAX series, and not NG? That would suggest a system different to, or unique for MAX compared to NG?
ERGO: MCAS.



The above link also gave some info on the stabilizer trim cut out (again for 737NG).
The 737NG has two electric stabilizer trim cut out switches, to disable (undesired) electric motor trimming;
1) Pedestal switch in the form of guarded toggle/flip switch;
2) Column switch, which activates when the control column moves in opposite direction from the stabilizer trim direction.

SUPPOSEDLY the column trim switch has been eliminated in the 737 Max (anyone able to confirm?), mainly because of MCAS which introduces a stall prevention functionality for a certain part of the flight envelope (flaps up, high speed, at certain alpha) in manual control. For this functionality to be effective, a desire exits for MCAS to override pilot command in its stall prevention functionality.

Apparently (again, confirmation needed), the elimination of the electronic trim cut out on the control column was not included in the pilot conversion course from NG to Max. So experienced 737 pilots might not have been aware that pulling he control column will not stop electronic trim motor.

So why did two 737 crashes in short time succession, both involved MAX series, and not NG? That would suggest a system different to, or unique for MAX compared to NG?
ERGO: elimination of column trim cut out switch.

If this line of thinking is followed, it can not be ignored that other systems than MCAS were in play (autopilot, STS) perhaps through corrupt ADIRU data. An event (not being elevator trim runaway**) that would be a relative non-issue on NG.

** defined in the link above as: "Uncommanded stabilizer trim movement occurs continuously".
 
BEG2IAH
Posts: 1135
Joined: Thu Apr 22, 2004 3:42 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:36 pm

michi wrote:
Stick shaker is triggered by excessive AOA, as far as I am aware.


Stick Shaker is activated any time you approach stall speeds. I was on a customer acceptance flight and witnessed it. We were flying level and the test pilots slowed down to stall speed. Stick shaker kicked in, as designed.
 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:36 pm

AngMoh wrote:
danj555 wrote:
Couldn't the pilots in any case of malfunction just turn off all electronic bs? Like you're a pilot. You know how to fly a plane. You have flown thousands of take-offs. You know the right speed, right angle, right altitude. You know how to do it without electronic interference if need be.

So why not hit the kill switch if the computer is having a fit?


Isn't that what the AirAsia pilots did just before they smashed into the sea?

FDR shows electric trim inputs by either the computer or pilot all the way up until the last maybe half second of flight. The accident flight did not turn off electric trim. The flight prior to the accident did turn off electric trim and had the uncommanded nose down trim stop. They then turned electric trim back on, had the uncommanded nose down trim happen again, so turned electric trim off and left it off.
 
chicawgo
Posts: 464
Joined: Tue Nov 29, 2011 5:09 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:40 pm

SomebodyInTLS wrote:
dragon6172 wrote:
dtw2hyd wrote:


Also, everyone claims pilots need to flip two cut-off switches and they are good. Did anyone test this theory with MAX/MCAS (or) just based on runaway stab procedures?

The Lion Air crew prior to the accident flight tested this procedure and it worked as advertised.


You forgot to add "by luck"! They had no idea what was going on but happened to guess correctly that trim could be involved. THERE WAS NO PROCEDURE.


Just absolutely spreading lies. They didn't just blindly guess. They made an educated decision based on experience and the situation. The trim was running wild so they cut the auto trim switches.
 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:47 pm

PW100 wrote:

SUPPOSEDLY the column trim switch has been eliminated in the 737 Max (anyone able to confirm?), mainly because of MCAS which introduces a stall prevention functionality for a certain part of the flight envelope (flaps up, high speed, at certain alpha) in manual control. For this functionality to be effective, a desire exits for MCAS to override pilot command in its stall prevention functionality.

Apparently (again, confirmation needed), the elimination of the electronic trim cut out on the control column was not included in the pilot conversion course from NG to Max. So experienced 737 pilots might not have been aware that pulling he control column will not stop electronic trim motor.

So why did two 737 crashes in short time succession, both involved MAX series, and not NG? That would suggest a system different to, or unique for MAX compared to NG?
ERGO: elimination of column trim cut out switch.

If this line of thinking is followed, it can not be ignored that other systems than MCAS were in play (autopilot, STS) perhaps through corrupt ADIRU data. An event (not being elevator trim runaway**) that would be a relative non-issue on NG.

** defined in the link above as: "Uncommanded stabilizer trim movement occurs continuously".

As far as I know, the control column cutout is still installed, just doesn't work when it is MCAS that is making trim inputs.

The signal from the flight control computer to the electric trim motor for MCAS trim inputs bypasses the control column cutout switch.
 
ec99
Posts: 262
Joined: Mon Mar 16, 2015 2:18 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:56 pm

Derico wrote:
Trin wrote:
[

Like you, I am trying to sit here and figure out how this system even came into being let alone got certified. .


Given this sentiment about this system is being echoed my quite a few on the av boards right now, this brings a follow up issue.

Because it already would be concerning enough that an aerospace company designed and approved such a solution, and that one national aviation authority certified it. But obviously all the other major aviation authorities around the world also approved it as safe for real world utilization.

What does this mean? To an outsider like me, this suggests either blind trust in the airplane designer and manufacturer, and or in the national authority that certified it. Otherwise it suggest they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features of new equipment or systems being introduced into the airspace they oversee.

That's puzzling and worrying.


You rightly ask about the FAA approving this system and why did they do that. There are several issues, one being Boeing capturing the FAA's leadership, it is a big problem. But another big issue is government funding. I work for the Federal government and deal with this on a daily basis. The graph in the FAA budget document below (page 6) shows that the FAAs budget was basically flat from 2010 to 2016. You can't ask the FAA to keep up with this type of work if you aren't going to fund it properly. This is doubly true for very technical stuff. Engineers and coders are so in demand right now, a problem across the federal government is lack of flexibility (and funding) to pay these people enough to get them to stay. When Amazon will pay you 300K, you have to really love your job to stay on as a GS-14 making 140K. I also know a few people who work at FAA (in non-aviation jobs) and the morale there has the same issues as any non DoD federal agency. Getting furloughed and having the President strongly oppose even a 1.9% cost of living raise doesn't do wonders for morale or productivity.

Sorry if that got a bit political but the FAA and its employees don't work in a vacuum. Understanding the challenges the FAA is dealing with is essential to understanding and preventing future incidents like this.

https://www.faa.gov/about/office_org/he ... t_2016.pdf
 
GalaxyFlyer
Posts: 9273
Joined: Fri Jan 01, 2016 4:44 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 2:57 pm

Interesting comment on PPW

My wife flies this airplane. The MCAS is far more than the MD-11s LSAS on steroids. There are a few disconnects between what’s commonly being reported and what’s in the flight safety reports and records.

First the MCAS should only be active when the autopilot is OFF. In that case what it is supposed to do is not much more than push the nose when it thinks the angle of attacking is too high. There are some obvious problems here in whether the aoa is really too high or not.


Next, if it is pushing the nose down while the a/c is in a proper climb, the pilots reaction is to pull back and attempt to restore the proper pitch attitude. This might be proper for a runaway stab trim, but for an errant MCAS it’s exactly the wrong thing to do and makes the situation worse. So how do you know what to do? Until the Lion Air crash, they didn’t. There was ZERO info in the manuals about it. You simply ran a checklist with NO memory items. Apparently while fighting the aircraft and trying to figure out wtf was happening. Today, they know but it’s still the same abnormal procedures checklist.


Now for the truly scary part. The industry reports are running contrary to the design of an active MCAS only whike the autopilot is off. So while the MCAS is supposed to be inactive with the autopilot ON. it’s still kicking in while George is flying. So now the autopilot is on, it’s fighting the MCAS when it malfunctions and you’re trying to fight both.


The Boeing proposed software fix for April 1(No Joke) was to modify the MCAS while the aircraft was in manual flight. But that’s not where the greatest danger is.


The Max isn’t your basic 737. It flies quite different, lands different, handles different, has different wings and different engine placement. It’s another dynamically unstable aircraft that requires stability augmentation to be flyable.



The UAL max training? a 20 minute computer slide show. My wife has flown DC-4’s, BAC111’s, DC-9, BAe146, 757, 767, 747 of various flavors and every version of the 737. She has nearly 20,000 hours flight time and this is the first aircraft she absolutely dreads flying.
 
User avatar
SheikhDjibouti
Posts: 2348
Joined: Sat Sep 30, 2017 4:59 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:08 pm

GalaxyFlyer wrote:
If the stick shaker activates due to the same erroneous AOA data that started the MCAS operation, shutting off the stab trim probably won’t stop the shaker. That now poses a problem, flying the plane with the shaker going. Very abnormal, possible difficult and, if tripping breakers is required to stop it, possibly taking time.
GF

Thank you. thank you, thank you. (have I mentioned recently that I do appreciate your contributions... :D )

I was half-way to asking the question as a follow-up to this that I wrote just over an hour ago.
(The Lion Air crew prior to the accident flight tested this procedure and it worked as advertised.)

Very Sheikhy wrote:
"Tested the procedure" - love it!

Isn't that the flight where the guy in the left hand seat had his stick shaker active for 84% of the time?

I bet it would have been fun to watch him try and eat soup for his dinner. :old:

EDIT; it was 100% of the flying time - the stick shaker was inactive during taxying.


What is the betting that one (or both) pilots on ET302 were at the very least distracted by constant stick shaker?
 
LTC8K6
Posts: 1599
Joined: Fri Jun 05, 2009 8:36 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:09 pm

I haven't seen accounts where MCAS was active when it should not have been?
 
hivue
Posts: 2187
Joined: Tue Feb 26, 2013 2:26 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:12 pm

GalaxyFlyer wrote:
Interesting comment on PPW

Now for the truly scary part. The industry reports are running contrary to the design of an active MCAS only whike the autopilot is off. So while the MCAS is supposed to be inactive with the autopilot ON. it’s still kicking in while George is flying. So now the autopilot is on, it’s fighting the MCAS when it malfunctions and you’re trying to fight both.


The Boeing proposed software fix for April 1(No Joke) was to modify the MCAS while the aircraft was in manual flight. But that’s not where the greatest danger is.


Wow (if that's actually true).
 
User avatar
PW100
Posts: 4126
Joined: Mon Jan 28, 2002 9:17 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:23 pm

anfromme wrote:
Pluto707 wrote:
MCAS is not the cause, but it gave the final blow

There's rarely a single cause, so in that sense you're right.
But all other things being equal, there is reason to doubt that we'd have more than 300 people dead without MCAS.
(Yes, I know, we are not 100% sure MCAS even played a role in ET302, but current satellite data and trim jackscrew findings do suggest this is the case, according to the Canadian and US authorities, at least.)

Regarding MCAS, I'm also wondering how a solution design with the following characteristics even made it past the very fist architectural stages, never mind through certification:
1) uses input from a single sensor
2) has no quorum/sanity check/tie-breaker or similar mechanism in place to determine whether sensor data is valid to begin with
3) has no automatic switch-off mechanism
4) has no limit on the level of trim it can exert
5) has no limit on the number of times it will cause trim input

That's just sloppy design and most non-safety-critical systems I've seen implemented first-hand were designed with more care.


Playing devils advocate . . . . :
1) Many systems do. The practice is not inherently unsafe. It would be if it concerns a (flight-) critical system.
In this case, on could argue that pitch trim is a flight critical system. Such system would require at least double redundancy (triple sensor system).
The design thoughts in this case were (and in-line with certification requirements), that sensor no.2 was PF (Pilot Flying) and sensor No.3 is PNF (Pilot Not Flying). In order to include the pilots in such critical loop, requires a slow system, which MCAS is (0.27 deg / sec). See below.

2) Sensor 2 and Sensor 3 (see above).

3) Switch off mechanism is embedded in Sensor 2 and Sensor 3.

4) It does have a limit: 2.5 deg AND 9.2 seconds operation.

5) Which is the normal state for many functions. Its function is to prevent the pilots from doing something undesired (stalling the plane). If the pilot(s) keep continue doing just that, the system must keep preventing entering the stall. Similarly, there is (rightfully) no limit to amount of stick shaker and stick pusher actions.


Of course a conflict of interest arises when the pilot has responsibility for flying the plane (which could include unintentional and unknowingly approaching stall condition) and at the same time needs to (unknowingly, as in, not trained in MCAS) assume responsibility for functions 1), 2) and 3). This becomes a particular problem when system go berserk (perhaps because of rogue ARIDU data) and all sorts of warning go off outside the straight forward memory items . . .
 
KingOrGod
Posts: 232
Joined: Mon Jan 16, 2017 3:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:30 pm

PW100 wrote:
anfromme wrote:
Pluto707 wrote:
MCAS is not the cause, but it gave the final blow

There's rarely a single cause, so in that sense you're right.
But all other things being equal, there is reason to doubt that we'd have more than 300 people dead without MCAS.
(Yes, I know, we are not 100% sure MCAS even played a role in ET302, but current satellite data and trim jackscrew findings do suggest this is the case, according to the Canadian and US authorities, at least.)

Regarding MCAS, I'm also wondering how a solution design with the following characteristics even made it past the very fist architectural stages, never mind through certification:
1) uses input from a single sensor
2) has no quorum/sanity check/tie-breaker or similar mechanism in place to determine whether sensor data is valid to begin with
3) has no automatic switch-off mechanism
4) has no limit on the level of trim it can exert
5) has no limit on the number of times it will cause trim input

That's just sloppy design and most non-safety-critical systems I've seen implemented first-hand were designed with more care.


Playing devils advocate . . . . :
1) Many systems do. The practice is not inherently unsafe. It would be if it concerns a (flight-) critical system.
In this case, on could argue that pitch trim is a flight critical system. Such system would require at least double redundancy (triple sensor system).
The design thoughts in this case were (and in-line with certification requirements), that sensor no.2 was PF (Pilot Flying) and sensor No.3 is PNF (Pilot Not Flying). In order to include the pilots in such critical loop, requires a slow system, which MCAS is (0.27 deg / sec). See below.

2) Sensor 2 and Sensor 3 (see above).

3) Switch off mechanism is embedded in Sensor 2 and Sensor 3.

[b]4) It does have a limit: 2.5 deg AND 9.2 seconds operation.[b]

5) Which is the normal state for many functions. Its function is to prevent the pilots from doing something undesired (stalling the plane). If the pilot(s) keep continue doing just that, the system must keep preventing entering the stall. Similarly, there is (rightfully) no limit to amount of stick shaker and stick pusher actions.


Of course a conflict of interest arises when the pilot has responsibility for flying the plane (which could include unintentional and unknowingly approaching stall condition) and at the same time needs to (unknowingly, as in, not trained in MCAS) assume responsibility for functions 1), 2) and 3). This becomes a particular problem when system go berserk (perhaps because of rogue ARIDU data) and all sorts of warning go off outside the straight forward memory items . . .


That's a rate, and not what the other poster meant. MCAS can trim it to full nose down which means that full back stick cannot stop a descent. If you realise it too late, and you're in a steep descent already, and you've killed the electric trim as they advocate, are you gonna be able to spin that wheel by hand to recover with just a few thousand feet remaining?

And my biggest gripe is no annunciation that it is activated. That's just plain stupid.
 
SunsetLimited
Posts: 1029
Joined: Thu Oct 02, 2014 6:20 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:32 pm

GalaxyFlyer wrote:
Interesting comment on PPW

My wife flies this airplane. The MCAS is far more than the MD-11s LSAS on steroids. There are a few disconnects between what’s commonly being reported and what’s in the flight safety reports and records.

First the MCAS should only be active when the autopilot is OFF. In that case what it is supposed to do is not much more than push the nose when it thinks the angle of attacking is too high. There are some obvious problems here in whether the aoa is really too high or not.


Next, if it is pushing the nose down while the a/c is in a proper climb, the pilots reaction is to pull back and attempt to restore the proper pitch attitude. This might be proper for a runaway stab trim, but for an errant MCAS it’s exactly the wrong thing to do and makes the situation worse. So how do you know what to do? Until the Lion Air crash, they didn’t. There was ZERO info in the manuals about it. You simply ran a checklist with NO memory items. Apparently while fighting the aircraft and trying to figure out wtf was happening. Today, they know but it’s still the same abnormal procedures checklist.


Now for the truly scary part. The industry reports are running contrary to the design of an active MCAS only whike the autopilot is off. So while the MCAS is supposed to be inactive with the autopilot ON. it’s still kicking in while George is flying. So now the autopilot is on, it’s fighting the MCAS when it malfunctions and you’re trying to fight both.


The Boeing proposed software fix for April 1(No Joke) was to modify the MCAS while the aircraft was in manual flight. But that’s not where the greatest danger is.


The Max isn’t your basic 737. It flies quite different, lands different, handles different, has different wings and different engine placement. It’s another dynamically unstable aircraft that requires stability augmentation to be flyable.



The UAL max training? a 20 minute computer slide show. My wife has flown DC-4’s, BAC111’s, DC-9, BAe146, 757, 767, 747 of various flavors and every version of the 737. She has nearly 20,000 hours flight time and this is the first aircraft she absolutely dreads flying.



Truly interesting to read this because the 40 or 50 pilots I’ve talked to who fly the MAX regularly all say basically the opposite - just another 737 with a better cockpit layout, handles essentially the same, very stable aircraft, etc. None of them said they dread flying it. Quite the opposite, actually.
 
SuperGT
Posts: 8
Joined: Wed Mar 13, 2019 8:13 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:33 pm

GalaxyFlyer wrote:
Interesting comment on PPW

My wife has flown DC-4’s, BAC111’s, DC-9, BAe146, 757, 767, 747 of various flavors and every version of the 737. She has nearly 20,000 hours flight time and this is the first aircraft she absolutely dreads flying.


Says it all really about this plane! Would love to hear input from more pilots who are on here? (or links if anyone finds something elsewhere?)
 
mcdu
Posts: 1749
Joined: Thu Apr 28, 2005 5:23 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:35 pm

SheikhDjibouti wrote:
mcdu wrote:
osiris30 wrote:
At 380kts at 8600' alt, the aircraft was definitely in a 'severe overspeed' condition. That is a speed that can incur structural failure unless managed very well.

You won’t see pilots operating at those speeds normally. First of all in the USA and many other places the limit is 250kts below 10k.

That is an ATC restriction, and nothing to do with aircraft structural issues.
The 250kt limit would apply to a Piper Malibu just as it would apply to Concorde (if it was still flying)

Did you see the Hawaiian airspeed indicator or just the data showing TAS?

I was half expecting that comment, and it is a fair question.
It was ground speed, but I believe I have seen it on flights operating in both directions at the same time, which means only one of them is benefitting from any tailwind. Tell me if I'm wrong.

I accept it isn't brilliant science, but currently it's better than anything anybody else has added to the subject. :D

Is there nobody here with actual verifiable figures from Boeing?


But no one flies around at the barber pole even when allowed (offshore). If you are on the barber pole there is no margin if you hit a bump and causes a momentary overspeed. That is a required maintenance inspection when you land. Also it is terrible inefficient to fly on like that.
 
User avatar
7BOEING7
Posts: 3039
Joined: Fri Oct 12, 2012 5:28 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:37 pm

estorilm wrote:
dtw2hyd wrote:
planecane wrote:
The issue isn't MCAS, it is the terrible implementation with no safeguards in the event of erroneous sensor inputs. The autopilot will disengage in that situation.


It appears MCAS thinks the plane is stalling and human is not able to handle, so let me help the poor human by trimming nose down for 10 more seconds.

If its sole purpose is to solve unstable flight, they wouldn't have put it in an infinite loop, first human interaction would disable like STS.

This is a case of computer thinks it knows better than humans, which is historical with stall handing,

Also, everyone claims pilots need to flip two cut-off switches and they are good. Did anyone test this theory with MAX/MCAS (or) just based on runaway stab procedures?

You have to dig a bit deeper than that though. For 50 years, normal stall recovery procedures were perfectly adequate on prior aircraft, even when it came time to certify the NG. For some reason, that's not the case with the MAX.


Actually the NG has a system similar to MCAS. It has one sentence in the ops manual and no procedures.
 
mzlin
Posts: 143
Joined: Sat Mar 31, 2012 6:32 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:38 pm

Bjorn's analysis is up at leeham news. Thinks unreliable AOA indicator can explain unreliable airspeed. Informative graphs.
 
frmrCapCadet
Posts: 5418
Joined: Thu May 29, 2008 8:24 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:42 pm

Is it possible for a pilot, in any of the accidents or serious incidents, to know in a timely manner true situation awareness. Where they are, how fast they are going, to what degree are all the systems are working (and I know they are multitudinous), and to what degree the plane is flying itself, and if certain systems may be inaccurate how will it affect the automatic flying, and how much control they actually have over the airplane. And what is the danger of information overload (which I suspect may have contributed to both MAX crashes).
 
User avatar
7BOEING7
Posts: 3039
Joined: Fri Oct 12, 2012 5:28 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:45 pm

PW100 wrote:
mandala499 wrote:
Jetty wrote:
It shouldn’t go into effect until flaps are retracted. That doesn’t mean it doesn’t go into effect until flaps are retracted. From the Lion Air crash we know it has gone into effect when it shouldn’t before and there’s no way of knowing if this is isolated to one specific set of circumstances or an wider issue.

What I fear is that there is unreliable airspeed from the take off roll, and they were shocked to see stick shaker on from the take off roll, and decided to shallow out the climb to "get out of it"... only to not see it not disappear.... with the increasing speed and confusion with the stick shaker and the unreliable airspeed then comes the next question... did they pull up the flaps at 800' AGL?

Retracting the flaps at very high speeds (400 KTS) of speeds, in relatively thick air(below 10000 ft), what will that do to the aerodynamic trim balance of a 737 Max?
If auto trim is already off (MCAS deactivated / elevator trim cut switches activated), can the change in pitch trim be easily corrected manually?


The flaps (if extended) probably wouldn’t still be attached to the airplane at 400 kts.
 
osiris30
Posts: 2681
Joined: Sat Sep 30, 2006 10:16 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:47 pm

frmrCapCadet wrote:
Is it possible for a pilot, in any of the accidents or serious incidents, to know in a timely manner true situation awareness. Where they are, how fast they are going, to what degree are all the systems are working (and I know they are multitudinous), and to what degree the plane is flying itself, and if certain systems may be inaccurate how will it affect the automatic flying, and how much control they actually have over the airplane. And what is the danger of information overload (which I suspect may have contributed to both MAX crashes).


GPS and a lookup chart can get you close enough on airspeed and position.

Hell at 8600ft (edit) MSL if you know the winds you can pretty much use raw GPS speed

(edit had agl not msl there)
Last edited by osiris30 on Fri Mar 15, 2019 4:03 pm, edited 1 time in total.
 
Amsterdam
Posts: 454
Joined: Thu Mar 17, 2011 12:52 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:54 pm

dragon6172 wrote:
dtw2hyd wrote:
That is just a theory because previous flight didn't crash. It could be just MCAS trim down did not reach a point of no return and crew could recover.

Well true... they didn't wait until MCAS had trimmed full nose down to turn off the electric trim. Doing that would require some expedient hand cranking to get the aircraft back in trim. Never the less.... the PIC noticed that the aircraft was trimming down after every SIC trim up, so he turned off electric trim. Later in the climb, the PIC turned electric trim back on and the nose down trim started again, so the PIC turned off electric trim for the remainder of the flight.

SomebodyInTLS wrote:
You forgot to add "by luck"! They had no idea what was going on but happened to guess correctly that trim could be involved. THERE WAS NO PROCEDURE.

By luck? Guess? Give me a break. The pilot was able to troubleshoot a problem and was able to apply a known procedure (runaway electric trim) to another problem (uncommanded electric trim).
From the preliminary report:
While handling the problem, the PIC instructed the SIC to continue acceleration and flap retraction as normal. The PIC commanded the SIC to follow FD command and re-trim the aircraft as required. The PIC noticed that as soon the SIC stopped trim input, the aircraft was automatically trimming aircraft nose down (AND).
After three automatic AND trim occurrences, the SIC commented that the control column was too heavy to hold back.
The PIC moved the STAB TRIM switches to CUT OUT and manually trimmed.
The PIC re-engaged the STAB TRIM switches to NORMAL, but almost immediately the problem re-appeared. The PIC then moved the STAB TRIM switches back to CUT OUT and continued with manual trim without auto-pilot until the end of the flight.


No system should be able to trim an aircraft in an attitude beyond unrecoverable from that attitude

It would be striking if that would be possible
Last edited by Amsterdam on Fri Mar 15, 2019 3:56 pm, edited 1 time in total.
 
birdbrainz
Posts: 517
Joined: Fri May 27, 2005 6:57 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:54 pm

Completely unrelated comment: Has anyone wondered why the Chinese were so quick to ground the MAX?

Could it be that they have their own flight tracking, and picked up the similarities (if any) to the Lion Air crash? Or was it just a knee-jerk? Just wondering.

As for flying the MAX, I'd really love to see more comments by those who actually fly the MAX. Is it really so bad? Yes. I saw the five reports in the media about those that hate it, and all I can think about is how much the the quirks of the 727 must have had its detractors at the time.
 
tupolev141
Posts: 19
Joined: Mon Dec 30, 2013 12:41 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 3:55 pm

ec99 wrote:
You rightly ask about the FAA approving this system and why did they do that. There are several issues, one being Boeing capturing the FAA's leadership, it is a big problem.


Most of us who work in this industry realise that sometimes this industry is too small. You have an FAA which is supposed to keep manufacturers in check, but there is just one massive US civil manufacturer left. And where does the FAA get their high profile bureaucrats from? From that manufacturer. Europe has the same problem, really. Of course, the FAA still has their aura and their word is still global law.

The immense pressure Airbus and Boeing are under to keep improving their aircraft and designing new ones all the while having a knife on their throat by the airlines who don't want to invest in a penny too much pilot training is just not healthy.
 
frmrCapCadet
Posts: 5418
Joined: Thu May 29, 2008 8:24 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:02 pm

osiris30 wrote:
frmrCapCadet wrote:
Is it possible for a pilot, in any of the accidents or serious incidents, to know in a timely manner true situation awareness. Where they are, how fast they are going, to what degree are all the systems are working (and I know they are multitudinous), and to what degree the plane is flying itself, and if certain systems may be inaccurate how will it affect the automatic flying, and how much control they actually have over the airplane. And what is the danger of information overload (which I suspect may have contributed to both MAX crashes).


GPS and a lookup chart can get you close enough on airspeed and position.

Hell at 8600ft agl if you know the winds you can pretty much use raw GPS speed


I believe that the electronics are available to augment GPS. I think surveyors use them all the time.
 
Interested
Posts: 890
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:04 pm

SuperGT wrote:
Derico wrote:
Trin wrote:
[

Like you, I am trying to sit here and figure out how this system even came into being let alone got certified. .


Given this sentiment about this system is being echoed my quite a few on the av boards right now, this brings a follow up issue.

Because it already would be concerning enough that an aerospace company designed and approved such a solution, and that one national aviation authority certified it. But obviously all the other major aviation authorities around the world also approved it as safe for real world utilization.

What does this mean? To an outsider like me, this suggests either blind trust in the airplane designer and manufacturer, and or in the national authority that certified it. Otherwise it suggest they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features of new equipment or systems being introduced into the airspace they oversee.

That's puzzling and worrying.


- blind trust in the airplane designer and manufacturer
- or in the national authority that certified it
- they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features

You have hit nail on head so to speak. All of the above, in my view!

Otherwise, there is no other way this madness could happen. As mentioned earlier on this thread, the entire thing stinks of 'politics' now between two or more parties....


Until this week I would have blindly trusted every new Boeing plane in operation to be perfectly safe. I would only be worried about bird strikes and terrorists. Now if I was on a max plane I would want to sit near the front ready to remind the pilots of lion and Ethiopia issues if anything weird happened on takeoff!
 
Amsterdam
Posts: 454
Joined: Thu Mar 17, 2011 12:52 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:06 pm

After 5 years on the 737/8/9 and more than 3000 hours I can see that it has always behaved predictable. Excellent airplane and highly reliable. In 5 years I have only had that Turkish Airlines failure, on a flight at 10.000 feet exactly the auto throttle went to idle after the radio altimeter on the active side of the auto pilot suddenly showed 0 feet, at 10.000 feet. Besides that, great aeroplane.

Boeing should fix whatever is needed and get the 73 airworthy again, and hurry up with a true succesor, something that they should do anyway.
 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:07 pm

Amsterdam wrote:

No system should be able to trim an aircraft in an attitude beyond unrecoverable from that attitude

It would be striking if that would be possible


Electric trim on any aircraft can result in an unrecoverable attitude if no action is taken.
 
Waterbomber2
Posts: 1482
Joined: Mon Feb 04, 2019 3:44 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:08 pm

dragon6172 wrote:
AngMoh wrote:
danj555 wrote:
Couldn't the pilots in any case of malfunction just turn off all electronic bs? Like you're a pilot. You know how to fly a plane. You have flown thousands of take-offs. You know the right speed, right angle, right altitude. You know how to do it without electronic interference if need be.

So why not hit the kill switch if the computer is having a fit?


Isn't that what the AirAsia pilots did just before they smashed into the sea?

FDR shows electric trim inputs by either the computer or pilot all the way up until the last maybe half second of flight. The accident flight did not turn off electric trim. The flight prior to the accident did turn off electric trim and had the uncommanded nose down trim stop. They then turned electric trim back on, had the uncommanded nose down trim happen again, so turned electric trim off and left it off.


Did Boeing add another hidden flight envelope protection besides MCAS perhaps?

A feature that is perhaps uncovered by another failure at the instruments level?

This is starting to freak me out... Thank god they are all grounded.
Last edited by Waterbomber2 on Fri Mar 15, 2019 4:09 pm, edited 1 time in total.
 
WIederling
Posts: 10041
Joined: Sun Sep 13, 2015 2:15 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:09 pm

dtw2hyd wrote:
This is a case of computer thinks it knows better than humans, which is historical with stall handing,

Also, everyone claims pilots need to flip two cut-off switches and they are good. Did anyone test this theory with MAX/MCAS (or) just based on runaway stab procedures?


There is no AI in safety critical computers.( at least not yet.)
Even heuristics are probably frowned on.
AI would result in action from stimulus being unpredictable.

MCAS acting on false input is not stab runaway.
Stab runaway is defined as continuous activation of trim in one direction
going by what has been posted here. like stuck contacts on a relay.
 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:12 pm

Waterbomber2 wrote:
dragon6172 wrote:
AngMoh wrote:

Isn't that what the AirAsia pilots did just before they smashed into the sea?

FDR shows electric trim inputs by either the computer or pilot all the way up until the last maybe half second of flight. The accident flight did not turn off electric trim. The flight prior to the accident did turn off electric trim and had the uncommanded nose down trim stop. They then turned electric trim back on, had the uncommanded nose down trim happen again, so turned electric trim off and left it off.


Did Boeing add another hidden flight envelope protection besides MCAS perhaps?

A feature that is perhaps uncovered by another failure at the instruments level?

This is starting to freak me out... Thank god they are all grounded.

How do you come to that conclusion?
 
ikramerica
Posts: 15232
Joined: Mon May 23, 2005 9:33 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:17 pm

Pluto707 wrote:
ikramerica wrote:
Notes:
-did not climb correctly. Much too low. Cant be MCAS in that phase

Why a suggestion that MCAS cannot be involved at low agl ?

Are they retracting flaps with net elevation less than 1000 feet? So the initial loss of control isn't MCAS.

Now, after a minute or two, the pilot asks to continue "normal" (not sure who's words) climb out to 14,000. One might assume he has flaps retracted then? So maybe it's then that MCAS comes on? But he's very low and something is preventing climb. He's also very fast because all the high thrust setting is going forward (and down when they pitch down) rather than into the climb.

Still want a commercial jet pilot's take on this:

If you are below 1000 feet from the ground, is it safe to bank a fully functioning aircraft for a 180 return to the airfield? Is it safe when your aircraft is acting like a petulant child and you don't know why?
 
dtw2hyd
Posts: 9100
Joined: Wed Jan 09, 2013 12:11 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:21 pm

WIederling wrote:
...
There is no AI in safety-critical computers.( at least not yet.).


I didn't mean AI, collective brains behind the code.
 
ikramerica
Posts: 15232
Joined: Mon May 23, 2005 9:33 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:23 pm

WIederling wrote:
dtw2hyd wrote:
This is a case of computer thinks it knows better than humans, which is historical with stall handing,

Also, everyone claims pilots need to flip two cut-off switches and they are good. Did anyone test this theory with MAX/MCAS (or) just based on runaway stab procedures?


There is no AI in safety critical computers.( at least not yet.)
Even heuristics are probably frowned on.
AI would result in action from stimulus being unpredictable.

MCAS acting on false input is not stab runaway.
Stab runaway is defined as continuous activation of trim in one direction
going by what has been posted here. like stuck contacts on a relay.

AI tells adopted kids to kill their parents. (Amazon Alexa)
It orders cat food after hearing a commercial.
It thinks a computer voice spontaneously comforting a crying person will comfort them and not creep them out.
It laughs for no reason. It whistles for no reason. It lists off names of local cemeteries for no reason.

Right now, AI would crash more planes than it would prevent a pilot from crashing. Maybe in 20 years it will be different.
 
osiris30
Posts: 2681
Joined: Sat Sep 30, 2006 10:16 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:25 pm

Interested wrote:
SuperGT wrote:
Derico wrote:

Given this sentiment about this system is being echoed my quite a few on the av boards right now, this brings a follow up issue.

Because it already would be concerning enough that an aerospace company designed and approved such a solution, and that one national aviation authority certified it. But obviously all the other major aviation authorities around the world also approved it as safe for real world utilization.

What does this mean? To an outsider like me, this suggests either blind trust in the airplane designer and manufacturer, and or in the national authority that certified it. Otherwise it suggest they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features of new equipment or systems being introduced into the airspace they oversee.

That's puzzling and worrying.


- blind trust in the airplane designer and manufacturer
- or in the national authority that certified it
- they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features

You have hit nail on head so to speak. All of the above, in my view!

Otherwise, there is no other way this madness could happen. As mentioned earlier on this thread, the entire thing stinks of 'politics' now between two or more parties....


Until this week I would have blindly trusted every new Boeing plane in operation to be perfectly safe. I would only be worried about bird strikes and terrorists. Now if I was on a max plane I would want to sit near the front ready to remind the pilots of lion and Ethiopia issues if anything weird happened on takeoff!


Well, there is no reason for you to change your behavior. Even as a fan of Boeing's products I will be the first to admit there have been some critical flaws (every aircraft ever has had them, sometimes they manifest in accidents, other times incidents) and they get worked out over time. Remember the jackscrew issue with the 737. Fuel tank inerting problems (all types). Wiring issues leading to fires (all types at that time period), Dc 10 issues. More than a few gremlins in Airbus's computers over the years. 99% of the time the pilots flying deal with these issues and they get reported and fixed. Sometimes things go wrong. Even Concorde it could be argued had critical flaws (despite being an absolute marvel of engineering ESPECIALLY given when it was built). Dash 8s had wonky landing gear issues for a while. I mean the list is pretty much endless and that is the stuff we KNOW was fixed. All the stuff that was fixed silently would likely fill volumes.

People acting like this is a unique thing are forgetting their history.
 
Interested
Posts: 890
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:31 pm

osiris30 wrote:
Interested wrote:
SuperGT wrote:

- blind trust in the airplane designer and manufacturer
- or in the national authority that certified it
- they don't particularly bother to take time and resources to independently scrutinize and go over the engineering, schematics, architecture, and features

You have hit nail on head so to speak. All of the above, in my view!

Otherwise, there is no other way this madness could happen. As mentioned earlier on this thread, the entire thing stinks of 'politics' now between two or more parties....


Until this week I would have blindly trusted every new Boeing plane in operation to be perfectly safe. I would only be worried about bird strikes and terrorists. Now if I was on a max plane I would want to sit near the front ready to remind the pilots of lion and Ethiopia issues if anything weird happened on takeoff!


Well, there is no reason for you to change your behavior. Even as a fan of Boeing's products I will be the first to admit there have been some critical flaws (every aircraft ever has had them, sometimes they manifest in accidents, other times incidents) and they get worked out over time. Remember the jackscrew issue with the 737. Fuel tank inerting problems (all types). Wiring issues leading to fires (all types at that time period), Dc 10 issues. More than a few gremlins in Airbus's computers over the years. 99% of the time the pilots flying deal with these issues and they get reported and fixed. Sometimes things go wrong. Even Concorde it could be argued had critical flaws (despite being an absolute marvel of engineering ESPECIALLY given when it was built). Dash 8s had wonky landing gear issues for a while. I mean the list is pretty much endless and that is the stuff we KNOW was fixed. All the stuff that was fixed silently would likely fill volumes.

People acting like this is a unique thing are forgetting their history.


It's a different world in 2019 though don't you think?

Health and safety rules. Any of my staff have any kind of accident at work I have to report it and do something to stop it happening again. I can't have them carry on working with the same risk in place? Whikst I spend 4 months trying to figure out what to do different?

I could get prosecuted and lose my business if if I did.

And that's me a small business owner. This is Boeing in 2019.
Last edited by Interested on Fri Mar 15, 2019 4:34 pm, edited 1 time in total.
 
osiris30
Posts: 2681
Joined: Sat Sep 30, 2006 10:16 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:34 pm

ikramerica wrote:
Pluto707 wrote:
ikramerica wrote:
Notes:
-did not climb correctly. Much too low. Cant be MCAS in that phase

Why a suggestion that MCAS cannot be involved at low agl ?

Are they retracting flaps with net elevation less than 1000 feet? So the initial loss of control isn't MCAS.

Now, after a minute or two, the pilot asks to continue "normal" (not sure who's words) climb out to 14,000. One might assume he has flaps retracted then? So maybe it's then that MCAS comes on? But he's very low and something is preventing climb. He's also very fast because all the high thrust setting is going forward (and down when they pitch down) rather than into the climb.

Still want a commercial jet pilot's take on this:

If you are below 1000 feet from the ground, is it safe to bank a fully functioning aircraft for a 180 return to the airfield? Is it safe when your aircraft is acting like a petulant child and you don't know why?


The aircraft wasn't climbing despite more than enough airspeed, ostensibly flaps and everything else. This tells me the AC was out of trim before it left the ground. It makes me think that the previous crew disabled auto-trim and this crew never even turned it on, until possibly way too late.

As time has gone on I have continued to flesh out what *I* feel the chain of events is and to my mind now it starts before the take-off roll:

1) Either on prior flight or before commencing this flight; pilots of last flight or this flight disable MCAS as a precatuion (stab cut-off)
2) PIlots of this flight miss (or knew it was off), but fail to trim plane correctly.
3) Take off roll starts. IAS is broken.
4) Pilots attempt to rotate too early based on broken IAS. Nose comes off by AC doesn't unstick from the ground until 160kts (FR24 data). This is pretty high for a max IIRC.
5) Aircraft won't climb (bad trim). Pilots apply more pressure.
6a) Pilots fight with AC while continuing to increase speed to dangerous levels (no one watching the GPS ground speed). Cockpit is FULL of alarms at this point.
6b) Someone withdraws flaps during this time (or they come clean off depending on the extent of deployment, but probably the first option)
7) More time passes
8a) Someone in the cockpit notices the auto-trim is off and flips it on. Manual trim should have been used but for whatever reason wasn't (pilot may have thought they were fighting MCAS the entire time and they weren't).
8b) MCAS or autotrim (it could be either) kick in
(OR)
8a) Pilots notice trim is out and trim the AC the wrong way in error. At that altitude and speed it does not take much to cause really bad things to happen.

everything up to 7 is pretty solid in my mind based on the data we have (1/2 are obvious extrapolations of how it starts). 8 is obviously conjecture.
 
trnswrld
Posts: 1424
Joined: Sat May 22, 1999 2:19 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:36 pm

danj555 wrote:
Couldn't the pilots in any case of malfunction just turn off all electronic bs? Like you're a pilot. You know how to fly a plane. You have flown thousands of take-offs. You know the right speed, right angle, right altitude. You know how to do it without electronic interference if need be.

So why not hit the kill switch if the computer is having a fit?


I asked this exact question many pages ago. It got pretty much no response. Big problems in IMC is one thing, but to not be able to fly an airplane in clear blue VMC daylight conditions just baffles me....computer issues or not. How does this happen? Look out the window.....fly the airplane FIRST, then figure what the heck is going on. I know easier said than done.
 
Interested
Posts: 890
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:36 pm

osiris30 wrote:
ikramerica wrote:
Pluto707 wrote:
ikramerica wrote:
Notes:
-did not climb correctly. Much too low. Cant be MCAS in that phase

Why a suggestion that MCAS cannot be involved at low agl ?

Are they retracting flaps with net elevation less than 1000 feet? So the initial loss of control isn't MCAS.

Now, after a minute or two, the pilot asks to continue "normal" (not sure who's words) climb out to 14,000. One might assume he has flaps retracted then? So maybe it's then that MCAS comes on? But he's very low and something is preventing climb. He's also very fast because all the high thrust setting is going forward (and down when they pitch down) rather than into the climb.

Still want a commercial jet pilot's take on this:

If you are below 1000 feet from the ground, is it safe to bank a fully functioning aircraft for a 180 return to the airfield? Is it safe when your aircraft is acting like a petulant child and you don't know why?


The aircraft wasn't climbing despite more than enough airspeed, ostensibly flaps and everything else. This tells me the AC was out of trim before it left the ground. It makes me think that the previous crew disabled auto-trim and this crew never even turned it on, until possibly way too late.

As time has gone on I have continued to flesh out what *I* feel the chain of events is and to my mind now it starts before the take-off roll:

1) Either on prior flight or before commencing this flight; pilots of last flight or this flight disable MCAS as a precatuion (stab cut-off)
2) PIlots of this flight miss (or knew it was off), but fail to trim plane correctly.
3) Take off roll starts. IAS is broken.
4) Pilots attempt to rotate too early based on broken IAS. Nose comes off by AC doesn't unstick from the ground until 160kts (FR24 data). This is pretty high for a max IIRC.
5) Aircraft won't climb (bad trim). Pilots apply more pressure.
6a) Pilots fight with AC while continuing to increase speed to dangerous levels (no one watching the GPS ground speed). Cockpit is FULL of alarms at this point.
6b) Someone withdraws flaps during this time (or they come clean off depending on the extent of deployment, but probably the first option)
7) More time passes
8a) Someone in the cockpit notices the auto-trim is off and flips it on. Manual trim should have been used but for whatever reason wasn't (pilot may have thought they were fighting MCAS the entire time and they weren't).
8b) MCAS or autotrim (it could be either) kick in
(OR)
8a) Pilots notice trim is out and trim the AC the wrong way in error. At that altitude and speed it does not take much to cause really bad things to happen.

everything up to 7 is pretty solid in my mind based on the data we have (1/2 are obvious extrapolations of how it starts). 8 is obviously conjecture.


Which of the above (if any) are caused by software failings?
 
1010101
Posts: 15
Joined: Tue Nov 14, 2006 12:13 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:40 pm

GalaxyFlyer wrote:
Interesting comment on PPW

My wife flies this airplane. The MCAS is far more than the MD-11s LSAS on steroids. There are a few disconnects between what’s commonly being reported and what’s in the flight safety reports and records.

First the MCAS should only be active when the autopilot is OFF. In that case what it is supposed to do is not much more than push the nose when it thinks the angle of attacking is too high. There are some obvious problems here in whether the aoa is really too high or not.


Next, if it is pushing the nose down while the a/c is in a proper climb, the pilots reaction is to pull back and attempt to restore the proper pitch attitude. This might be proper for a runaway stab trim, but for an errant MCAS it’s exactly the wrong thing to do and makes the situation worse. So how do you know what to do? Until the Lion Air crash, they didn’t. There was ZERO info in the manuals about it. You simply ran a checklist with NO memory items. Apparently while fighting the aircraft and trying to figure out wtf was happening. Today, they know but it’s still the same abnormal procedures checklist.


Now for the truly scary part. The industry reports are running contrary to the design of an active MCAS only whike the autopilot is off. So while the MCAS is supposed to be inactive with the autopilot ON. it’s still kicking in while George is flying. So now the autopilot is on, it’s fighting the MCAS when it malfunctions and you’re trying to fight both.


The Boeing proposed software fix for April 1(No Joke) was to modify the MCAS while the aircraft was in manual flight. But that’s not where the greatest danger is.


The Max isn’t your basic 737. It flies quite different, lands different, handles different, has different wings and different engine placement. It’s another dynamically unstable aircraft that requires stability augmentation to be flyable.



The UAL max training? a 20 minute computer slide show. My wife has flown DC-4’s, BAC111’s, DC-9, BAe146, 757, 767, 747 of various flavors and every version of the 737. She has nearly 20,000 hours flight time and this is the first aircraft she absolutely dreads flying.


This starts to make more sense to me now. The instinctive pilot reaction to erroneous MCAS nose trim down is to pull back on the control yoke which just makes the problem worse. That eats up valuable time trying to understand what is happening.

The other detail is something at least MCAS like operated while the autopilot is engaged. This is the second pilot report I have seen with this claim.
 
dakota123
Posts: 245
Joined: Wed Aug 30, 2006 11:03 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:45 pm

KingOrGod wrote:
PW100 wrote:
anfromme wrote:
There's rarely a single cause, so in that sense you're right.
But all other things being equal, there is reason to doubt that we'd have more than 300 people dead without MCAS.
(Yes, I know, we are not 100% sure MCAS even played a role in ET302, but current satellite data and trim jackscrew findings do suggest this is the case, according to the Canadian and US authorities, at least.)

Regarding MCAS, I'm also wondering how a solution design with the following characteristics even made it past the very fist architectural stages, never mind through certification:
1) uses input from a single sensor
2) has no quorum/sanity check/tie-breaker or similar mechanism in place to determine whether sensor data is valid to begin with
3) has no automatic switch-off mechanism
4) has no limit on the level of trim it can exert
5) has no limit on the number of times it will cause trim input

That's just sloppy design and most non-safety-critical systems I've seen implemented first-hand were designed with more care.


Playing devils advocate . . . . :
1) Many systems do. The practice is not inherently unsafe. It would be if it concerns a (flight-) critical system.
In this case, on could argue that pitch trim is a flight critical system. Such system would require at least double redundancy (triple sensor system).
The design thoughts in this case were (and in-line with certification requirements), that sensor no.2 was PF (Pilot Flying) and sensor No.3 is PNF (Pilot Not Flying). In order to include the pilots in such critical loop, requires a slow system, which MCAS is (0.27 deg / sec). See below.

2) Sensor 2 and Sensor 3 (see above).

3) Switch off mechanism is embedded in Sensor 2 and Sensor 3.

[b]4) It does have a limit: 2.5 deg AND 9.2 seconds operation.[b]

5) Which is the normal state for many functions. Its function is to prevent the pilots from doing something undesired (stalling the plane). If the pilot(s) keep continue doing just that, the system must keep preventing entering the stall. Similarly, there is (rightfully) no limit to amount of stick shaker and stick pusher actions.


Of course a conflict of interest arises when the pilot has responsibility for flying the plane (which could include unintentional and unknowingly approaching stall condition) and at the same time needs to (unknowingly, as in, not trained in MCAS) assume responsibility for functions 1), 2) and 3). This becomes a particular problem when system go berserk (perhaps because of rogue ARIDU data) and all sorts of warning go off outside the straight forward memory items . . .


That's a rate, and not what the other poster meant. MCAS can trim it to full nose down which means that full back stick cannot stop a descent. If you realise it too late, and you're in a steep descent already, and you've killed the electric trim as they advocate, are you gonna be able to spin that wheel by hand to recover with just a few thousand feet remaining?

And my biggest gripe is no annunciation that it is activated. That's just plain stupid.


Except that hitting the manual electric switch will stop MCAS and you can happily keep stopping it and taking back out the ND that MCAS put in all day long if one is so inclined (not that that is the procedure). That is what it appears the PF (apparently the captain) did with the accident Lionair flight - -for some reason after handing control to the FO, likely after not wanting to deal with the shaker another minute more, the FO didn’t keep with the program. Not fully, anyway because he apparently was stopping MCAS but didn’t take bac out what the MCAS had introduced. Maybe because one doesn’t normally trim in a turn? Who knows. (This is all consistent with the FDR traces published so far). I can absolutely see that being task-saturated one might not even realize that forces are gettign relentlessly heavier, especially in a turn when forces get heavier in any case. Reportedly Boeing’s change will (among other things) limit MCAS authority.

Absolutely agreed, stupidly designed system. it will be really interesting to see why that design choice was made. If the Indonesian report isn’t fulsome, I hope the NTSB issues some sort of supplment.
 
CO953
Posts: 523
Joined: Tue Jan 08, 2013 4:05 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:46 pm

osiris30 wrote:
[...snip......]

People acting like this is a unique thing are forgetting their history.


I would respectfully submit that this is the first new aircraft type that repeatedly tries to commit suicide by diving toward the ground at low altitude.
 
VS11
Posts: 1827
Joined: Mon Jul 02, 2001 6:34 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:47 pm

How soon apart were the two crashed MAXes built? Who is the manufacturer of the pitot tubes and the AOA indicators? MCAS may have its issues and like all software it is work in progress - wouldn’t be surprised if Boeing was working on newer versions even before Lion Jet. However, there is this serious issue of low quality components being installed on jets. Does Boeing or Airbus test these component before installed?
 
Interested
Posts: 890
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:48 pm

1010101 wrote:
GalaxyFlyer wrote:
Interesting comment on PPW

My wife flies this airplane. The MCAS is far more than the MD-11s LSAS on steroids. There are a few disconnects between what’s commonly being reported and what’s in the flight safety reports and records.

First the MCAS should only be active when the autopilot is OFF. In that case what it is supposed to do is not much more than push the nose when it thinks the angle of attacking is too high. There are some obvious problems here in whether the aoa is really too high or not.


Next, if it is pushing the nose down while the a/c is in a proper climb, the pilots reaction is to pull back and attempt to restore the proper pitch attitude. This might be proper for a runaway stab trim, but for an errant MCAS it’s exactly the wrong thing to do and makes the situation worse. So how do you know what to do? Until the Lion Air crash, they didn’t. There was ZERO info in the manuals about it. You simply ran a checklist with NO memory items. Apparently while fighting the aircraft and trying to figure out wtf was happening. Today, they know but it’s still the same abnormal procedures checklist.


Now for the truly scary part. The industry reports are running contrary to the design of an active MCAS only whike the autopilot is off. So while the MCAS is supposed to be inactive with the autopilot ON. it’s still kicking in while George is flying. So now the autopilot is on, it’s fighting the MCAS when it malfunctions and you’re trying to fight both.


The Boeing proposed software fix for April 1(No Joke) was to modify the MCAS while the aircraft was in manual flight. But that’s not where the greatest danger is.


The Max isn’t your basic 737. It flies quite different, lands different, handles different, has different wings and different engine placement. It’s another dynamically unstable aircraft that requires stability augmentation to be flyable.



The UAL max training? a 20 minute computer slide show. My wife has flown DC-4’s, BAC111’s, DC-9, BAe146, 757, 767, 747 of various flavors and every version of the 737. She has nearly 20,000 hours flight time and this is the first aircraft she absolutely dreads flying.


This starts to make more sense to me now. The instinctive pilot reaction to erroneous MCAS nose trim down is to pull back on the control yoke which just makes the problem worse. That eats up valuable time trying to understand what is happening.

The other detail is something at least MCAS like operated while the autopilot is engaged. This is the second pilot report I have seen with this claim.


Scary stuff

Galaxy - why don't the pilots speak out etc?
 
hivue
Posts: 2187
Joined: Tue Feb 26, 2013 2:26 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:49 pm

trnswrld wrote:
danj555 wrote:
Couldn't the pilots in any case of malfunction just turn off all electronic bs? Like you're a pilot. You know how to fly a plane. You have flown thousands of take-offs. You know the right speed, right angle, right altitude. You know how to do it without electronic interference if need be.

So why not hit the kill switch if the computer is having a fit?


I asked this exact question many pages ago. It got pretty much no response. Big problems in IMC is one thing, but to not be able to fly an airplane in clear blue VMC daylight conditions just baffles me....computer issues or not. How does this happen? Look out the window.....fly the airplane FIRST, then figure what the heck is going on. I know easier said than done.


Killing all computers operating on an airplane would have the same effect as killing all computer chips that are operating in your car while you're driving (assuming you are not driving a Stone Age car).
 
ikramerica
Posts: 15232
Joined: Mon May 23, 2005 9:33 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 15, 2019 4:50 pm

osiris30 wrote:
ikramerica wrote:
Pluto707 wrote:
ikramerica wrote:
Notes:
-did not climb correctly. Much too low. Cant be MCAS in that phase

Why a suggestion that MCAS cannot be involved at low agl ?

Are they retracting flaps with net elevation less than 1000 feet? So the initial loss of control isn't MCAS.

Now, after a minute or two, the pilot asks to continue "normal" (not sure who's words) climb out to 14,000. One might assume he has flaps retracted then? So maybe it's then that MCAS comes on? But he's very low and something is preventing climb. He's also very fast because all the high thrust setting is going forward (and down when they pitch down) rather than into the climb.

Still want a commercial jet pilot's take on this:

If you are below 1000 feet from the ground, is it safe to bank a fully functioning aircraft for a 180 return to the airfield? Is it safe when your aircraft is acting like a petulant child and you don't know why?


The aircraft wasn't climbing despite more than enough airspeed, ostensibly flaps and everything else. This tells me the AC was out of trim before it left the ground. It makes me think that the previous crew disabled auto-trim and this crew never even turned it on, until possibly way too late.

As time has gone on I have continued to flesh out what *I* feel the chain of events is and to my mind now it starts before the take-off roll:

1) Either on prior flight or before commencing this flight; pilots of last flight or this flight disable MCAS as a precatuion (stab cut-off)
2) PIlots of this flight miss (or knew it was off), but fail to trim plane correctly.
3) Take off roll starts. IAS is broken.
4) Pilots attempt to rotate too early based on broken IAS. Nose comes off by AC doesn't unstick from the ground until 160kts (FR24 data). This is pretty high for a max IIRC.
5) Aircraft won't climb (bad trim). Pilots apply more pressure.
6a) Pilots fight with AC while continuing to increase speed to dangerous levels (no one watching the GPS ground speed). Cockpit is FULL of alarms at this point.
6b) Someone withdraws flaps during this time (or they come clean off depending on the extent of deployment, but probably the first option)
7) More time passes
8a) Someone in the cockpit notices the auto-trim is off and flips it on. Manual trim should have been used but for whatever reason wasn't (pilot may have thought they were fighting MCAS the entire time and they weren't).
8b) MCAS or autotrim (it could be either) kick in
(OR)
8a) Pilots notice trim is out and trim the AC the wrong way in error. At that altitude and speed it does not take much to cause really bad things to happen.

everything up to 7 is pretty solid in my mind based on the data we have (1/2 are obvious extrapolations of how it starts). 8 is obviously conjecture.


I hope that's not the cause. It would, however, match with what I think two of the main failure modes of the Lion air crash was:
1. lack of transfer of knowledge from the previous flight crew to the next. Not informing the fateful crew what the previous crew turned on/off and why.
2. lack of information provided by Boeing/Aircraft that something isn't working right, a safety mechanism is activating, something is disable, etc.

And number 2 seems to me is a broader issue of the 737NG as well, just not showing itself because the implications have YET to lead to a crash. I'm sure in the history of the 737NG there have been many incidents where the crew was not aware of some issues with the aircraft that were impacting flight control, and the aircraft wasn't designed to make them aware, but crashes didn't ensue, just white knuckles and dirty knickers.

Who is online

Users browsing this forum: a19901213, ASguy2012, Baidu [Spider], Cerecl, Chris8874, EightyFour, Google [Bot], hpff, ifly4free, Jalap, jetstream3399, LFA30095, masi1157, MonAmQB, NZdsgnr, ryanflyer, TK787, Vctony, ZK-NBT and 131 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos