Indonesian aircraft missing off Jakarta

[SpeedBurn]

737 elevator was considered as a cause for crash before also.

For example, Flydubai Flight 981 (Report:'Flydubai Flight 981 Crash')

Even though it was filed as pilot error, there is still a controversy because, one dissenting commission member, a Rosaviatsiya representative, filed an alternative opinion report, claiming the commission ignored a possible mechanical malfunction of the Boeing 737's elevator controls.

As of now, the Interstate Aviation Committee has not released their final report of the crash.

Seems like there are some serious issued in elevator controls of 737's.

[Gary Brown]

Originally Posted by SpeedBurn

737 elevator was considered as a cause for crash before also.

For example, Flydubai Flight 981 (Report:'Flydubai Flight 981 Crash')

Even though it was filed as pilot error, there is still a controversy because, one dissenting commission member, a Rosaviatsiya representative, filed an alternative opinion report, claiming the commission ignored a possible mechanical malfunction of the Boeing 737's elevator controls.

As of now, the Interstate Aviation Committee has not released their final report of the crash.

Seems like there are some serious issued in elevator controls of 737's.

I think you're conflating two separate 737 crashes. Tatarstan 363 which had the dissenting opinion you mention (and both the Official and Dissenting Reports have been published), and FlyDubai 981, whose report has not yet been issued. There are some similarities with the present LionAir - but lots of dissimilarities too.

[MurphyWasRight]

Originally Posted by Hi_Tech

I doubt it Sax R54
I will believe this statement and several similar ones posted by others that Crew are not briefed about this system, only if one B737 MAX certified pilot tells this forum that he was not aware of it. This mod in MAX is a significant change from previous -800 etc, to protect the aircraft exceeding AOA approaching a stall. I am sure there will also be an EICAS alert when the system is active.
So is there any one with B737 MAX training / Certified in this forum to clarify this matter?

Unless it is totally fake this line from the e-mail halfnut posted should answer the question. ( https://www.pprune.org/rumours-news/614857-indonesian-aircraft-missing-off-jakarta.html#post10307740 )

This is the first description you, as 737 pilots, have seen. It is not in the AA 737 Flight Manual Part 2, nor is there a description in the Boeing FCOM. It will be soon.
...
...
...
Captain XXXXXXX
DFW 737I
APA Safety Committee Chairman

[Concours77]

Originally Posted by Hi_Tech

I doubt it Sax R54
I will believe this statement and several similar ones posted by others that Crew are not briefed about this system, only if one B737 MAX certified pilot tells this forum that he was not aware of it. This mod in MAX is a significant change from previous -800 etc, to protect the aircraft exceeding AOA approaching a stall. I am sure there will also be an EICAS alert when the system is active.
So is there any one with B737 MAX training / Certified in this forum to clarify this matter?

I do NOT meet your criteria for responding....

I would point out simply that your use of the word “briefed...” is not germane. The FAA has required addition to the TEXT of the Operators Manual.

It is required that there be written description, not “briefing...”

To be read, and understood by the Operators.

[Rananim]

Not necessarily, it is entirely conceivable that a design flaw has been lurking there since day one of commercial operation. It just takes a specific sequence to cause an accident

I prefer this theory..We dont know if this is MAX specific.A cursory glance at the NG AMM confirms that this will happen in a NG as well.There may well be differences between MCAS and STS but they both involve trim,they both require inputs that may be corrupted.....you will get unwanted trim if the holes in the swiss cheese line up whether youre sitting in an NG or MAX.

Because of the many variables involved(type of UAS/piloting ability/which FCC is controlling) this specific sequence just never occurred before.We know piloting ability is definitely a variable because this was the 4th flight in sequence.Which FCC is controlling the trim is just a throw of the die...software logic...the pilot wont know this in the heat of the moment(the data is buried in the AMM anyway).The type of UAS is a huge variable(ie multiple ADIRU inputs to FCC,single side vs both side etc).

Is it a design flaw?You cant design perfection...not yet anyway.They need the protection systems but unfortunately those systems may be fed with corrupt data.

Manual flight....you establish this as a recall item during a UAS event.What is manual flight?AP/AT/FD are de-selected.You dont de-select trim....now you may well de-select trim if you recognize STS (or MCAS) responding to bad side data(alertness good airmanship),or you may even disable the AP stab trim as a precaution before STS or MCAS even has a chance to trim(high level of airmanship)....or you may not recognize the insidious trim until its too late due startle factor/panic/inexperience/distraction of tactile aural warnings.So many variables...

Nobody has the data yet on MCAS but Im assuming it works via the AP stab trim motor(even though Boeing in their AD says to disconnect both trim motors) and its controlled by one FCC at a time...
What surprises me here is the total absence of any discussion on the need for pilots to disable loud tactile aural warnings being fed by corrupt data.This to me is the key.The need to establish calm and quiet in a confusing environment can not be over-stated.IMO,the 4 circuit breakers for left/right overspeed and stick shaker should be on the center pedestal right next to the pilots.Those warnings are life savers when correct....but they may be killers when corrupted by bad data.

[lomapaseo]

What surprises me here is the total absence of any discussion on the need for pilots to disable loud tactile aural warnings being fed by corrupt data.This to me is the key.The need to establish calm and quiet in a confusing environment can not be over-stated

In some regards I agree, however I have seen pilots who killed the noise and then took an action which they assumed corrected the cause and then continued on unaware that the problem was still there hiding in the background to catch them out later in the flight

[A Squared]

Originally Posted by Rananim

I prefer this theory..We don't know if this is MAX specific.

Boeing think that Boeing knows. The Boeing's manual bulletin and subsequent AD say that it is applicable to the 737MAX8 and 737MAX9 (But not the 737MAX7) They didn't choose that list of applicable models at random. I don't know what their reasons are, but for some reason they believe that this is limited to the -8 and -9. Is the MCAS installed only on the -8 and -9 but not on the -7, or any previous models? I don't know, just asking the question. It doesn't appear that there's a lot of information about this MCAS.

[GarageYears]

Originally Posted by A Squared

Boeing think that Boeing knows. The Boeing's manual bulletin and subsequent AD say that it is applicable to the 737MAX8 and 737MAX9 (But not the 737MAX7) They didn't choose that list of applicable models at random. I don't know what their reasons are, but for some reason they believe that this is limited to the -8 and -9. Is the MCAS installed only on the -8 and -9 but not on the -7, or any previous models? I don't know, just asking the question. It doesn't appear that there's a lot of information about this MCAS.

I think that is exactly the case. This MCAS system is something added for the MAX (but not documented...). There are lots and lots of NGs out there, and I think it safe to assume both Boeing and the FAA (and the APA for that matter) would have mentioned it, had it applied to the NG series.

The question "why?" is was added to the MAX doesn't seem to have been addressed? Was there some aspect of certification that required it? If so, how can the aircraft need it for certification, but not have it documented in the info that the folks in the pointy-end use?

- GY

[Concours77]

Originally Posted by A Squared

Boeing think that Boeing knows. The Boeing's manual bulletin and subsequent AD say that it is applicable to the 737MAX8 and 737MAX9 (But not the 737MAX7) They didn't choose that list of applicable models at random. I don't know what their reasons are, but for some reason they believe that this is limited to the -8 and -9. Is the MCAS installed only on the -8 and -9 but not on the -7, or any previous models? I don't know, just asking the question. It doesn't appear that there's a lot of information about this MCAS.

Trying not to be pedantic. If MCAS is “Manual Control Enhancement”, but is uncommanded, (automatic) does that make the nomenclature oxymoronic? To claim it is not oxymoronic is to require an “assumption” on the Operator’s part? In the absence of written reference, I would say it does. Isn’t that the basis for the AD?

[underfire]

There is some legacy stuff in the box that does get sorted out now and then. I noted a few when first getting into the RNP-AR coding. Smiths box would not allow an airport rwy endpoint over 10,000 feet. We were specifically always using flyby waypoints, even on tangent, tangent legs. There was a memorable waypoint which was erroneously coded flyover, when the ac passed over they waypoint, it porpused down about 300 feet and leveled off. Turns out, there was a legacy item the code looked up (in the sequence) that looked back to a simple radius of the Earth that was coded in. The ac went from the GPS geiod altitude to the simple radius altitude on the lookup.

Took a while to debug that one, but when you actually look through all of the code, you see all kinds of crap. No one is sure where/when to fix it, because not sure all of the myriad of sequencing possibilities in tracing the code.

Note: a long while back, there was a question on submerging the box in fresh water. Anything that has been submerged need to be soaked in fresh water, as the salt is so corrosive. Artefacts such as cannon from shipwrecks are soaked for years.

[PPRuNe Towers]

A word of warning. In the last 24 hours a video has started floating around supposedly of a flight sim flight with the FDR track running on it.

You'll know it when you see it as the sim user had a complete fetish for moving the external view position. It is unattributed but looks plausible, ignores things like the massive 'upward' FR24 spike prior to descent and shows repeated attempts to maintain control of attitude until impact.

Don't bother putting it on here due to the lack of provenance, the amateur use of the sim software and the building of confirmation bias with pretty pictures.

Rob

[Concours77]

Originally Posted by underfire

There is some legacy stuff in the box that does get sorted out now and then. I noted a few when first getting into the RNP-AR coding. Smiths box would not allow an airport rwy endpoint over 10,000 feet. We were specifically always using flyby waypoints, even on tangent, tangent legs. There was a memorable waypoint which was erroneously coded flyover, when the ac passed over they waypoint, it porpused down about 300 feet and leveled off. Turns out, there was a legacy item the code looked up (in the sequence) that looked back to a simple radius of the Earth that was coded in. The ac went from the GPS geiod altitude to the simple radius altitude on the lookup.

Took a while to debug that one, but when you actually look through all of the code, you see all kinds of crap. No one is sure where/when to fix it, because not sure all of the myriad of sequencing possibilities in tracing the code.

Note: a long while back, there was a question on submerging the box in fresh water. Anything that has been submerged need to be soaked in fresh water, as the salt is so corrosive. Artefacts such as cannon from shipwrecks are soaked for years.

Hi. Aren’t the boxes constructed to keep sea water OUT of the interior? I can see washing the box to flush salt a couple times, but soaking? An example would be AF447? After TWO years in salt, the boxes were undisturbed by corrosion. At a depth of 4000 meters?

[slacktide]

Originally Posted by A Squared

The Boeing's manual bulletin and subsequent AD say that it is applicable to the 737MAX8 and 737MAX9 (But not the 737MAX7)

The 737-7 is not yet certified. You cannot write an airworthiness directive against a model that does not have a type certificate.

[CaptainMongo]

Originally Posted by A Squared

The current Lion crash is the only accident I can think of where inaccurate AoA data was (may have been) a triggering event. What are some others?

Accident on 27 November 2008 off the coast of Canet-Plage (66) to the Airbus A320-232 registered D-AXLA operated by XL Airways Germany

and

Lufthansa Airbus A321-200, registration D-AIDP performing flight LH-1829 from Bilbao,SP (Spain) to Munich (Germany) near Bilbao on Nov 5th 2014, loss of 4000 feet of altitude

are a couple examples

[FCeng84]

On the topic of stabilizer jack-screw speed I believe the video clip attached a few entries back is not showing the fastest available speed. 777 and 787 have stabilizer ranges of approximately 15 degrees with the maximum surface movement rate of 0.5 deg/sec. That gives 30 seconds to go from one end stop to the other. I believe that the 737 has a similar stabilizer motion range and may operate a bit slower. As a lower bound, I know that the 737 stabilizer can be moved at a rate of at least 0.25 deg/sec.
This is a slow surface and for that reason (among others) advertised piloting procedure is to always fly maneuvers and establish steady flight via the column (i.e., the elevator) using stabilizer trim only as a means of relieving steady column forces.

[Vessbot]

Originally Posted by Concours77

Trying not to be pedantic. If MCAS is “Manual Control Enhancement”, but is uncommanded, (automatic) does that make the nomenclature oxymoronic?

Sounds like an enhancement to manual control, that works automatically.

[CurtainTwitcher]

If you do a google search for "Maneuvering Characteristics Augmentation System" (must be in quotes to search fro the exact phrase, or MCAS, but limit the search to prior to 01 Nov 2018 there are no results.

[Concours77]

Originally Posted by Vessbot

Sounds like an enhancement to manual control, that works automatically.

Except that the “augmentation” works in opposition to manual control “feel”. Making it the opposite of enhancement or augmentation.

By the way, the Artificial Horizon locates the nose, and can be used to suss AoA from FPV, no?

cheers.

[infrequentflyer789]

Originally Posted by CurtainTwitcher

If you do a google search for "Maneuvering Characteristics Augmentation System" (must be in quotes to search fro the exact phrase, or MCAS, but limit the search to prior to 01 Nov 2018 there are no results.

Yes, however if you search for "Maneuvering Characteristics" near "Augmentation System" with the date limit you do get a result.
The actual search is (with date before 1 Nov 2018),

["Maneuver Characteristics" AROUND(10) "Augmentation System"]

This throws up a PDF FCOM for 737-800 from Newgen/Sabaidee. The reason it doesn't match your search is that the expansion of MCAS is split over two lines. The only match in the document is a glossary entry:

It is possible that the glossary is (or is intended to be) common to -800 and MAX documents, it is also possible that there are no other hits because other 737 FCOMs online predate the change and there are no MAX FCOMs online. It doesn't really tell us much except that there was a clear intent to document MCAS in some way - whether it actually was documented or how well we don't know. I'd be interested in what was in the AMM, if anything.

[Concours77]

“...what does this mean? Why is this search so difficult?”

Because the system is proprietary?

wiedehopf: Are we not discussing the accident? If the tailplane is automatically trimming nose down due to (erroneous) and high AoA, and making nose up more difficult, until the Pitch cannot be overcome by elevator, that seems to me to be opposite to operators’ inputs. The “expected” feel is not “heavy”, making it opposite to (expectation of) manual control feel, no?

Explain your reference to “stall”? That was not the pilots problem. Their issue was inability to climb, not stall recovery. Right?