Another Country Grounds The 737-MAX

[tamada]

The point is Boeing is an old-school, union-labor, US flagship that were allowed to buy out the other US manufacturers and thus killed off any local competition. This was supposed to present a better, unified American challenge to the then, mostly EU government-funded Airbus. The fact that they stopped making the B-52 almost 57 years ago is only testament to the longevity of a single, functional, limited role, combat aircraft and shouldn't be seen as an endorsement of their ability to tweak aging commercial airframes to meet new technology and new markets. There's little innovation beyond retrofits and re-engineering and wringing the last buck out of tired old tubes. Airbus is a bespoke manufacturer of aircraft and from day one, they have always embraced a fleet-wide commonality of cockpit layout and how their fly-by-wire systems perform. Thus it's easier for pilots to migrate from narrow-body to wide-body and larger, high bypass engines with none of Boeing's optional iPad lessons and MCAS bolt-ons.

[sometimewoodworker]

There is now a Aircraft Accident Investigation Preliminary Report
From
Ethiopian Airlines Group

Data from the 2 black boxes show

It took of slightly after 05:37:34

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 ¾ 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.

About 2 minutes later At 05:40:35 the MCAS having activated twice was disabled (stab trim cut-out).

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.

At 05:43:20, approximately five seconds after the last manual electric trim input (nose up), 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. (About 2.3 would be normal)

So from that it is pretty clear that the automatic AND (Aircraft Nose Down) command was unable to be overcome by the pilots (too high a speed, too close to the ground)

Though not clear in the report it is probable that because the pilots were unable to manually adjust the trim due to high airspeed and other control surfaces loading the stabilisers that they decided to reengaged the stab trim to permit them to use the electric trim motor, this will have let the MCAS issue an active AND command 5 seconds after a manual trim command. There seems to be nothing in The Boeing documentation that comments on the resetting and reactivation of MCAS 5 seconds after a manual trim command.


The standard way to permit manual trim if the plane is badly trimmed is to let the nose sink by releasing pressure on the stick but so fast and so close to the ground that would not be safe.

[tamada]

Good take on the whole, sad affair here.

https://spectrum.ieee.org/aerospace/avi ... -developer

"The anti-stall system depended crucially on sensors that are installed on each side of the airliner—but the system consulted only the sensor on one side."

When taken in conjunction with the earlier YouTube comment about the single input from the AoA sensor toggling between port and starboard computer automatically between each flight rotation, it does seem that a bit of blind faith was placed in technology. With regard to an early suggestion that the Lion Air technician who either tested or simply replaced the 'faulty' AoA sensor, ie. the WRONG sensor, that may be a case of a badly trained or misinformed local airline technician (the preferred excuse?) or a technical training shortcoming from Boeing that matches the minimal training given to transitioning pilots via iPad.

The 'self-certification' procedure has opened a wider path to criminal charges but since this was an agreement between a government regulator and the nation's singular, flagship airplane maker, I think it will be just a case of how much time, money and lawyers fees are needed to bury it.

[pipoz4444]

Good take on the whole, sad affair here.

https://spectrum.ieee.org/aerospace/avi ... -developer

"The anti-stall system depended crucially on sensors that are installed on each side of the airliner—but the system consulted only the sensor on one side."

When taken in conjunction with the earlier YouTube comment about the single input from the AoA sensor toggling between port and starboard computer automatically between each flight rotation, it does seem that a bit of blind faith was placed in technology. The 'self-certification' procedure has opened a wider path to criminal charges but since this was an agreement between a government regulator and the nation's singular, flagship airplane maker, I think it will be just a case of how much time, money and lawyers fees are needed to bury it.

Correct and correct that it alternates from one side to the other after each flight, or after a Maintennace Test/Check, and miss the defective one, as it did in the Lion Air incident.

It (MCAS) was always just a cheap fix system for the Design based error

https://www.youtube.com/watch?v=4koccb8suOQ

pipoz4444

[sometimewoodworker]

Good take on the whole, sad affair here.

https://spectrum.ieee.org/aerospace/avi ... -developer

Unfortunately there is at least one factual error in the article by By Gregory Travis according to all the other information published by others and it contradicts the documentation on the MCAS system operation from Boeing its self, Boeing is not going to publish documentation that can be shown to be wrong as that will open them up to much greater problems that the have now.

Because of that known error I have to doubt his all his other statements related to the mechanics of the control systems and servomechanism related to them. I don't know that they are wrong but he has lost all credibility because of the known error. Peer review of the article would be the only way to discover the correctness of his claims, I certainly don't have the knowledge to say how much is correct.

While it is pretty clear that Boeing is at fault from the lack of pilot training requirements, lack of information on the system available to both pilots a maintenance crew, terrible software design and possibly other things we don't know of at the moment, the final outcome for the MAX range of planes is far from certain. It is also far from clear what should or will be the final result, it is almost certainly more dependent on politics than engineering.

[tamada]

Good take on the whole, sad affair here.

https://spectrum.ieee.org/aerospace/avi ... -developer

Unfortunately there is at least one factual error in the article by By Gregory Travis according to all the other information published by others and it contradicts the documentation on the MCAS system operation from Boeing its self, Boeing is not going to publish documentation that can be shown to be wrong as that will open them up to much greater problems that the have now.

Because of that known error I have to doubt his all his other statements related to the mechanics of the control systems and servomechanism related to them. I don't know that they are wrong but he has lost all credibility because of the known error. Peer review of the article would be the only way to discover the correctness of his claims, I certainly don't have the knowledge to say how much is correct.

While it is pretty clear that Boeing is at fault from the lack of pilot training requirements, lack of information on the system available to both pilots a maintenance crew, terrible software design and possibly other things we don't know of at the moment, the final outcome for the MAX range of planes is far from certain. It is also far from clear what should or will be the final result, it is almost certainly more dependent on politics than engineering.

Can you define exactly this "one factual error" you speak of?

Is it, "MCAS is implemented in the flight management computer, even at times when the autopilot is turned off, when the pilots think they are flying the plane." ?

[sometimewoodworker]

Can you define exactly this "one factual error" you speak of?

Is it, "MCAS is implemented in the flight management computer, even at times when the autopilot is turned off, when the pilots think they are flying the plane." ?

Exactly, MCAS is only functional while the pilots are manually flying the plane.

That is abundantly clear from the documentation, so that error which is known, as I said means that the other statements specially the ones under are thrown into doubt, as I said I don't have the knowledge to say that those are wrong but without independent peer comments supporting them they certainly seem extremely difficult to believe, the second one seems to be a clear misstatement or deliberate misleading description of the difference between the forces that are able to be applied by the stabilisers and the elevators.

When the flight computer trims the airplane to descend, because the MCAS system thinks it’s about to stall, a set of motors and jacks push the pilot’s control columns forward. It turns out that the flight management computer can put a lot of force into that column—indeed, so much force that a human pilot can quickly become exhausted trying to pull the column back, trying to tell the computer that this really, really should not be happening.

And

Indeed, not letting the pilot regain control by pulling back on the column was an explicit design decision. Because if the pilots could pull up the nose when MCAS said it should go down, why have MCAS at all?

A lot of the comments related to the financial choices and reasons for getting the 737 MAX designs signed off seem correct, and may we'll be true. It is a shame that, for what ever reason, he has shot himself in the foot.

[tamada]

I take special note of his wording. He states:

"MCAS is implemented in the flight management computer, even at times when the autopilot is turned off, when the pilots think they are flying the plane."

That is not the same as;

"MCAS is implemented in the flight management computer when the autopilot is turned off, when the pilots are flying the plane."

The use of "even at times" and "when the pilots think" suggests that what we are being led to believe by Boeing may not be as cut and dried or black and white as they suggest. The understanding up to now is that MCAS is only enabled after flaps are retracted. That understanding comes from what Boeing tells us. This is what we are told is written in (possibly hastily re-written) manuals and training guides. Since both doomed aircraft experienced difficulty relatively quickly after take-off and during early climb-out, the author may be offering that there may be more to the interaction of the MCAS than has been suggested? Something was issuing the AND command and spinning the trim wheels faster than the human hand was ever able to do.

The point I take from the article isn't so much the financial and market forces that drove the manufacturer and the regulator down this road but the aircraft is being 'flown' by software with code that is written by non-pilots in an effort to make the add-on bits of an old-fashioned, conventional, hydraulically controlled aircraft more like the Airbus's 'fly by wire' architecture. The Airbus was built this way from the ground up and had its own painful, sometimes fatal teething troubles in the development stage whereas Boeing's MCAS appears more of a digital patch on an analog problem with something that is already airborne with passengers in the seats.

[sometimewoodworker]

I take special note of his wording. He states:

"MCAS is implemented in the flight management computer, even at times when the autopilot is turned off, when the pilots think they are flying the plane."

That is not the same as;

"MCAS is implemented in the flight management computer when the autopilot is turned off, when the pilots are flying the plane."

The use of "even at times" and "when the pilots think" suggests that what we are being led to believe by Boeing may not be as cut and dried or black and white as they suggest. The understanding up to now is that MCAS is only enabled after flaps are retracted. That understanding comes from what Boeing tells us. This is what we are told is written in (possibly hastily re-written) manuals and training guides. Since both doomed aircraft experienced difficulty relatively quickly after take-off and during early climb-out, the author may be offering that there may be more to the interaction of the MCAS than has been suggested? Something was issuing the AND command and spinning the trim wheels faster than the human hand was ever able to do.

The point I take from the article isn't so much the financial and market forces that drove the manufacturer and the regulator down this road but the aircraft is being 'flown' by software with code that is written by non-pilots in an effort to make the add-on bits of an old-fashioned, conventional, hydraulically controlled aircraft more like the Airbus's 'fly by wire' architecture. The Airbus was built this way from the ground up and had its own painful, sometimes fatal teething troubles in the development stage whereas Boeing's MCAS appears more of a digital patch on an analog problem with something that is already airborne with passengers in the seats.

It is exactly the takeaway from the article that is what is wrong with it. There is no peer review to support the dangerously provocative suggestions. The statement that "aircraft is being 'flown' by software with code that is written by non-pilots" suggests that pilots, who have extensive training in flying, would somehow be better at writing computer code, a job that they are not trained for and generally incapable of doing, than people who have the training and experience in writing and debugging code.

I know that the 737 NEO has automatic computer controlled stabaliser adjustment. The 737s are certified ( individually as with any plane) for ILS CAT III landings (that is a completely automatic landing possible in zero visibility) and for Simultaneous Offset Instrument Approach (SOIA) landings. Neither of these can certifications function with "add-on bits" they are totally integrated

Flap retraction in virtually all flights for big airliners starts at about 1,000 feet, Boeing manuals state that it should be complete by 3,000, many companies have policies to retract flaps at a much lower altitude than that as deployed flaps create drag and drag uses more fuel. Retraction of flaps at a lowere altitude saves tonnes of fuel per year.

So flap retraction starts usually about 30 seconds into the flight, later with a shallow takeoff angle.

Ethiopian report.

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,

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.

No suggestion that MCAS operation wasn't as stated by Boeing, flaps retracted at about 82 seconds into the flight

Lion Air problems started at about 7,000 feet, at least 4,000 feet after flap retraction.

Something was issuing the AND command and spinning the trim wheels faster than the human hand was ever able to do.

suggest that that is bad, whereas it is perfectly normal for the electric trim motor to spin the trim wheels faster than the human hand was ever able to do.

Boeing is already in such deep doodoo and so clearly at fault for the incidents that if it is shown that they have published anything about MCAS that is not true they will have made such an enormous mistake that they will not be trusted for anything. It would probably be the beginning of the end for them.

[Giggle]

Yeah, the beginning of the end.

[tamada]

I know that the 737 NEO has automatic computer controlled stabaliser adjustment. ...

Are these the ones you speak of?

[sometimewoodworker]

I know that the 737 NEO has automatic computer controlled stabaliser adjustment. ...

Are these the ones you speak of?

No, there are no problems with the NEO stabilisers AFIK I wasn't suggesting that there were.

I was making the point that automatic computer controlled stabaliser adjustment is not a new system. As implemented in MCAS, yes that certainly is new. The system is not.

[tamada]

I know that the 737 NEO has automatic computer controlled stabaliser adjustment. ...

Are these the ones you speak of?

No, there are no problems with the NEO stabilisers AFIK I wasn't suggesting that there were.

I was making the point that automatic computer controlled stabaliser adjustment is not a new system. As implemented in MCAS, yes that certainly is new. The system is not.

I was humorously trying to make the point that AFAIK there's no such bird as a 737 NEO.

[sometimewoodworker]

I know that the 737 NEO has automatic computer controlled stabaliser adjustment. ...

Are these the ones you speak of?

No, there are no problems with the NEO stabilisers AFIK I wasn't suggesting that there were.

I was making the point that automatic computer controlled stabaliser adjustment is not a new system. As implemented in MCAS, yes that certainly is new. The system is not.

I was humorously trying to make the point that AFAIK there's no such bird as a 737 NEO.

OK you are correct, my mistake 737NG

[tamada]

Here's new, albeit a bit recycled, article that does collate some of the known knowns from the day before the Lion flight crashed and the similarities to what's already been gleaned from preliminary findings from the Ethiopian crash investigation. It also parallels it with Boeing's frantic efforts not to miss the wave WRT more fuel-efficient aircraft and bigger profits. The FAA's irresponsibility is also highlighted and no mention is made of airlines willingly buying something they may have suspected was compromised or a rush-job.

https://www.theverge.com/2019/5/2/18518 ... r-mcas-faa

[sometimewoodworker]

Here's new, albeit a bit recycled, article that does collate some of the known knowns from the day before the Lion flight crashed and the similarities to what's already been gleaned from preliminary findings from the Ethiopian crash investigation. It also parallels it with Boeing's frantic efforts not to miss the wave WRT more fuel-efficient aircraft and bigger profits. The FAA's irresponsibility is also highlighted and no mention is made of airlines willingly buying something they may have suspected was compromised or a rush-job.

https://www.theverge.com/2019/5/2/18518 ... r-mcas-faa

There is one assumption in the article that is probably correct but is not spelled out in the Ethiopian crash that the Stab trim was switched back on. From the report it is very probably correct and I have also guessed that it is what happened but without the full report it is still not absolutely clear

The other point that has an incorrect slant in the article that the experienced pilot flying did not diagnose the problem and that "It was Mohammed — the pilot whose experience was called “absurdly low” by Chesley “Sully” Sullenberger himself — who correctly diagnosed the problem."
Well was Mohammeds job, he wasn't flying so he had to go through the check lists so it was he who would probably suggest the correct diagnosis, so even though he was inexperienced he correctly found the problem.

It is quite likely that the ultimate diagnosis if the Ethiopian crash will be that the contributory factors will be in no specific order
MCAS fault,
pilot distraction allowing the thrust to continue at 94%,
Lack of information about the MCAS system
lack of pilot simulator training on MCAS failures.
Probable re-engagement of the electric stabilisers 30 seconds prior to the crash

[tamada]

^ I like your summary findings.

I too didn't like 'Sully's' referal to co-pilot's inexperience in the linked FB comment. Is there a pre-determined point in a pilot's hours accrual where he magically transitions from 'absurdly low' to 'acceptably low'? Is that absurdity level change between (say) 500 hours and 501 hours? I mean everyone has to be a rookie up to some point and despite the intervention of the dead-heading second pilot on Lion's penultimate flight, there are no instant experts even in the cockpit. In his FB comment, he goes on (an on) about how a pilot gains all the experience to handle every conceivable routine disturbance of a flight plan which makes him/her much more capable to address the inconceivably non-routine ones... like a geese strike and belly-flopping in the Hudson. I reckon Sully got lucky; there could have been a ferry in the way or it could have been pissing down rain with poor visibility and he could have planted it in Hoboken instead. I hope he doesn't see himself as somehow being better than the deceased, 200 hour + 5 minutes FO.

[sometimewoodworker]

^ I like your summary findings.

I too didn't like 'Sully's' referal to co-pilot's inexperience in the linked FB comment.

Thank you.

In those situations you have to get everything right within seconds, you may get a second chance but not a third. You also need a significant amount of luck, Sully had 270 seconds and a lot of luck.

The Ethiopian captain and FO had 332 seconds, no luck or proper training on the faulty system. RIP
The Ethiopian FO correctly diagnosed the problem. The captain, correctly, flew the plane and did not, but correctly agreed with the FO's diagnosis.

Was the Ethiopian incident survivable? Maybe.

Did the thrust at 94% throughout make it unsurvivable ? I don't have the training to know. It may well have been a command decision and the correct choice. It may have been an oversight and a deadly one.

It is certainly possible that reduction in thrust would have caused the crash to happen sooner as the high thrust certainly contributed to keeping the nose up and allowed the plane to gain some altitude.

I hope that we get to see the final report as we have the Aircraft Accident Investigation Preliminary Report.

1.5.2 FIRST-OFFICER According to Ethiopian Airlines records, the First-Officer has the following flight experience:

 Total hours: 361

 Total hours in B737: 207

 Total hours in B737-8 MAX: 56

 Flight time in previous 90 days: 207 hours and 26 minutes

 Flight time in previous 7 days: 10 hours and 57 minutes

 Flight time in previous 72 hours: 5 hours and 25 minutes

The first-officer was 25 years old. According to ECAA records, the first-officer's most recent simulator event was listed as a proficiency check and occurred on December 3, 2018. His line training/check (conducted in the B737 aircraft) was completed on January 31, 2019.

The first-officer's ECAA license allowed him to act as first-officer in commercial air transport operations in Boeing 737-7/800 (dated December 12, 2018) and Boeing 737 MAX (dated December 12, 2018.)

1.5.1 PILOT IN COMMAND According to Ethiopian Airlines records, the captain has the following flight experience:

 Total hours: 8122

 Total hours in B737: 1417

 Total hours in B737-8 MAX: 103

 Flight time in previous 90 days: 266 hours and 9 minutes

 Flight time in previous 7 days: 17 hours and 43 minutes

 Flight time in previous 72 hours: no flight time

The pilot in command was 29 years old. According to Ethiopian Civil Aviation Authority (ECAA) records, the Captain's most recent simulator training experience was September 30, 2018, and his most recent simulator proficiency check was October 1, 2018. The captain completed the Ethiopian Aviation Academy on July 23, 2010. A review of the captains training records indicated that he received his 737-800 First Officer type rating on January 31, 2011 and completed his PIC type rating for the 737-800 October 26, 2017. 737MAX differences training on 3 July, 2018.

Spot on with the Sully comment
he could have read the report before posting, but didn't, (his post March 15, report March 10)
he could have seen that other countries do things and report things differently to the US, but didn't
he could have realised that modern pilots train differently than he did, but didn't.
He could have got the FO flight experience correct, but didn't

[Galee]

[youtube]https://www.youtube.com/watch?v=QytfYyHmxtc[/youtube]

Interesting programme on the MAX. Scary stuff.

[papafarang]

so the basic 737 with the new engines would not fly correctly, because of the poor design. I mean how could it be even air worthy if it cant fly level ? so a Heath Robinson slap together idea come up of not letting people fly the plane...giving full control of the plane to a computer program ...and that program has one mode , point the plane at the ground. Darwin awards galore.
I did note the CEO in video " concerned about the IMPACT on customers " Did he really say that