Ethiopian 737 - same as Indonesia ?

[emerydc8]

Has anyone determined conclusively whether the A/P was in use during either of these crashes?

[andrej]

This resourceful website provides interesting information on the MCAS.

http://www.b737.org.uk/mcas.htm

Cheers,

[tango4]

Thanks for this link.
So it would seem it is an aerodynamic effect from the nacelle that would be causing concern and not the center of trhust.
Nevertheless, I have the feeling that had they designed a new airplane, this would have been a no go.
But as they found themselves "forced" to update the 737 with the latest generation of engines, they validated this bad aerodynamic configuration and put a bandaid on it.
When you see what they are doing with the landing gear of the MAX10, it looks kind of the same.
They are once again "forced" by the market (meaning the A321NEO LR which is selling very well) to make a bigger 737 to compete. But once again, the aircraft was never designed for such a length and they are forced to come with "strange" solutions to say the least.


Charles

[torrence]

Has anyone determined conclusively whether the A/P was in use during either of these crashes?

I haven't yet - and I was looking for some information on the AP since, as I understand the checklist for Unscheduled Stab Trim (at least on the 747), it includes turning off the autopilot as well as setting the cutout switches to Cutout.  I assume the autopilot state for both MAX accidents may be one of the things they may get from the black boxes.

Torrence

[Will]

If I am putting this together correctly, the Lion Air MAX8 had the MCAS activate because a faulty sensor gave incorrect information about the angle of attack.

Do we have any evidence that something similar happened (faulty AOA information leading MCAS to trim nose-down) in the Ethiopian MAX8?

[torrence]

There hasn't been any report I've seen of what the AOA was doing in the Ethiopian case.  As far as I can see from published reports the strongest suggestion that something similar was going on is the similarities of the records of altitude variations.

[farrokh747]

US as well now.....

https://edition.cnn.com/world/live-news/boeing-737-max-8-ethiopia-airlines-crash/index.html

fc

[emerydc8]

Now we'll see how political Boeing, the FAA and NTSB are. It has been weeks since the Atlas crash and we haven't really heard jack squat even though they have the recorders. Watch how fast they figure out what happened on the Ethiopian crash and come up with a fix for it, since there's big money at stake. Remember this when you hear them tell you it takes a long time for the investigators to put all the pieces together and we have to be patient, like has been said of the Atlas crash.

[Zapp]

This sounds pretty bad ....

(taken from CNN)

Speaking with reporters on a conference call, acting FAA Administrator Daniel Elwell said the grounding of the 737 Max 8 and 9 will remain in effect pending new information including from the flight data recorder and voice recorder. 

"Since this accident occurred we were resolute that we would not take action until we had data," Elwell said.

"That data coalesced today."
Elwell said the new data was "added fidelity -- missing pieces that we did not have prior to today." It aligned the Ethiopian flight data to the Lion Air incident.


Andrea

[torrence]

Re: Lion Air and Ethiopian Air 737 MAX crashes

Tragic as the circumstances are, I'm beginning to think the investigations of these incidents may mark an important watershed moment in crash investigations – driven primarily by the rapid availability of key flight data in near real time from ADS-B and related capabilities.  Hoppie and others have been discussing this on the Forum for some time.  Although not yet all-flight-data-in the cloud-all the time, the current capabilities (i.e. Flightradar24 and similar) are a long way from waiting days/weeks for black box recovery, more weeks/months for transport to specialized facilities for forensic analysis, more months/years for 'final' accident reports.  Although not definitive by themselves these data showed alarming similarities and prompted (finally) the US to ground the MAX aircraft temporarily.  Personally, these groundings may inconvenience me for this weekend's upcoming flight to a science conference, but I'll put up with it happily if it means lower probability for further loses (the old nautical 'souls on board' for the passenger count should be remembered - and yes, 3 SOB for the Atlas accident is just as tragic).

Torrence

[John H Watson]

driven primarily by the rapid availability of key flight data in near real time from ADS-B and related capabilities.

It's good if we can agree on the data that is being sent to us by ADS-B. Do all flight tracking programs show the same data? With the old ATC systems, the transponders sent altitude data based on standard baro (1013mb), not corrected (local) baro, and the ATC centres applied corrections as necessary.

Do ADS-B flight tracking programs use IRU/GPS groundspeed (not computed airspeed)? Do flight tracking programs use corrected baro? All programs interpolate data, so the data displayed is not always accurate.

[farrokh747]

Wouldn't the MCAS system be a sub-part of the larger SMYD - stall management yaw damper system ?

I haven't seen any info on how this is hooked up internally - typically the AOA sensors feed directly to the SMYD computers....   edit: perhaps they feed multiple systems, adc etc....

The 737 appears to have an Elevator Feel Shift Module, which increases the stick force in a stall..   I don't think the 744 has this device.....

http://www.737ng.co.uk/B_NG-Flight_Controls.pdf

Stall Identification
Stall identification and control is enhanced by the yaw damper, the Elevator Feel Shift (EFS) module and the speed trim system. These three systems work together to help the pilot identify and prevent further movement into a stall condition.
During high AOA operations, the SMYD reduces yaw damper commanded rudder movement.
The EFS module increases hydraulic system A pressure to the elevator feel and centering unit during a stall. This increases forward control column force to approximately four times normal feel pressure. The EFS module is armed whenever an inhibit condition is not present. Inhibit conditions are: on the ground, radio altitude less than 100 feet and autopilot engaged. However, if EFS is active when descending through 100 feet RA, it remains active until AOA is reduced below approximately stickshaker threshold. There are no flight deck indications that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the stabilizer nose down and enables trim above stickshaker AOA. With this trim schedule the pilot must pull more aft column to stall the airplane. With the column aft, the amount of column force increase with the onset of EFS module is more pronounced.

fc

[emerydc8]

This sounds like a very complicated version of the 767 "nudger." Boeing seems to be at a loss for words when explaining the details of its operation in the FCOM. I have never seen a demonstration as to how it works in the sim. I doubt it's even programmed into the sim. Maybe it's just on a "need-to-know" basis and I guess the flight crews don't need to know. No doubt a certification Band-Aid.

[Steve Hose]

This may be unrelated to the tragic incidents with Ethiopian & Lion Air, however a recent media report in Australia made these claims regarding the MAX:

"It comes hours after at least four pilots made reports following the October crash of a Lion Air flight in Indonesia shortly after takeoff, all complaining that the aircraft suddenly pitched downward, according to documents reviewed by AFP on a flight safety database. The incidents seem to involve the flight stabilisation system designed to prevent the aircraft from stalling, the "MCAS," which was implicated in the fatal accident in the Lion Air crash that killed 189 people shortly after takeoff.

One pilot logged an incident in November 2018, just weeks after the Lion Air crash, saying the plane "pitched nose down" two to three seconds after engaging the autopilot following takeoff, according to the report on the Aviation Safety Reporting System, maintained by NASA.

"The captain immediately disconnected the autopilot and pitched into a climb," the report said. "The rest of the flight was uneventful." The report said the flight crew reviewed the incident "at length ... but can't think of any reason the aircraft would pitch nose-down so aggressively." Another pilot on a flight in November said the crew discussed the concerns about the aircraft and "I mentioned I would engage the autopilot sooner than usual." But again once engaged, there was a quick automated warning of "DONT SINK DONT SINK!"

"I immediately disconnected the AP (autopilot) ... and resumed climb," the officer said. But after review, "frankly neither of us could find an inappropriate set up error."

Source (may be unreliable): https://www.news.com.au/travel/travel-updates/incidents/us-resists-pressure-to-ground-boeing-planes-despite-canada-banning-planes-pilots-concerns/news-story/734948a8165a4af53d4c6053f4b55bea

[Hardy Heinlin]

If there are two main factors -- AOA sensor system and MCAS software -- I ask myself which one is more likely to be the cause of the problem in all this similar incidents and accidents?

If 5000 737s have no problems with this AOA sensor system, and 50 737s fitted with a special software have a problem, then common sense tells me the problem probably lies in the software rather than in the AOA sensor. Especially if the software operates when it shouldn't (A/P engaged).

[Dirk Schepmann]

This may be unrelated to the tragic incidents with Ethiopian & Lion Air, however a recent media report in Australia made these claims regarding the MAX:

[...][¡]Another pilot on a flight in November said the crew discussed the concerns about the aircraft and "I mentioned I would engage the autopilot sooner than usual." But again once engaged, there was a quick automated warning of "DONT SINK DONT SINK!"

"I immediately disconnected the AP (autopilot) ... and resumed climb," the officer said. But after review, "frankly neither of us could find an inappropriate set up error."[/i]

The aural ,,DON'T SINK" alert also implies that the flaps were out of up in this case (immediately after takeoff). That's also a condition where the MCAS should not be active. It is either a different issue with the automatic pitch trim or another (poorly documented) protection system chimed in.

It is sad to read what Boeing has done with their incredible reliable 737 product line.

Dirk

[John H Watson]

I think one of the problems lies in the fact that only one AOA is used [EDIT: at a time] in the MCAS system. There are no comparisons/mixing/etc.

AOA sensors don't break very often (other than by physical damage from birds, ground equipment, etc). A bent AOA may cause an airspeed disagree. Airspeed disagrees can be resolved by the crew. MCAS does what it wants to do based on one AOA position.

I thought I read somewhere that the engineers didn't calibrate the AOA properly prior to the accident, but I can't find any calibration procedures in the AMM (for the standard NG)

[John H Watson]

It is sad to read what Boeing has done with their incredible reliable 737 product line.

I think the 737 has had its fair share of dramas ... rudder hardovers, fire systems crosswired, primitive fault annunciation systems (on the earlier aircraft), etc, causing quite a few catastropic incidents. 

[Swiso]

Possible ?
I mean..if reality, then it's a shame....
https://www.businessinsider.com/boeing-ethiopian-crash-government-shutdown-delayed-plane-software-fix-2019-3?r=US&IR=T

[farrokh747]

according to this:   

http://www.b737.org.uk/mcas.htm

The AoA source

I had assumed that the AoA source for MCAS was always the Captains AoA probe but the following explanation from an engineer suggests that it alternates between AoA probes each flight:

MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight.

so i guess only one sensor reading at a time....

fc