Ethiopian airliner down in Africa [Archive] - Page 6

73qanda

14th Mar 2019, 01:33

I think it is common for those who don’t fly Airliners, and also for those with only one or two years experience on them, to underestimate the effect of contradictory information being presented on the Primary Flight Displays.
For me, just when I thought I was a gun at flying appropriate thrust settings and attitudes during simulated Airspeed Unreliable scenarios, just as my confidence was peaking ( about six years on the NG after ten years on turbo-props), I was presented with a pitot-static issue on departure ( in the sim) that really had me struggling to know what was right. With the machine blaring WINDSHEAR WINDSHEAR WINDSHEAR while the stick shaker rattled away and the IAS was a moderately believable number......what to do? Is the WINDSHEAR real and I need to pitch to 15 etc etc or is the stickshaker real and I need to reduce pitch etc? Here come the Pitch Limit Indicators, gotta respect them right? They’re now down at 6 degrees nose up......
I managed to sneak away with it because of good support from my First Officer but it has given me a reality check with regard to the effects of contradictory information being presented when in IMC. I am now quicker to check my First Officers screen and I am also more aware of when Winshear is simply not going to be possible.
My point though, is that the machine (NG sim) applied no nose down trim, even without the machine applying nose down trim it can be very very challenging to apply sensible attitudes and thrust settings in real time as an event of this nature unfolds.
With unexpected and potentially unknown flight control inputs taking place in conjunction with contradictory information being presented one would hope to be in VMC with an excellent horizon.
Just my thoughts for those who think it is as simple as setting 10/80 and calling for the stab trim cutout switches to be operated.

speedbirdconcorde

14th Mar 2019, 02:07

Interesting article:
https://www.theatlantic.com/notes/2019/03/heres-what-was-on-the-record-about-problems-with-the-737-max/584791/

“These knobs don't seem to work in flight. The First Officer offered to hit the SEL function in flight, to test it out, but I thought something irreversible or undesirable might happen (not knowing what we were actually selecting), so we did not try it out in flight.”

SERIOUSLY????????

edmundronald

14th Mar 2019, 02:28

At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.

Edmund

73qanda

14th Mar 2019, 02:33

At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.
Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.

lomapaseo

14th Mar 2019, 02:35

Salute MJB !!

..... snip

A pure FBW control system has all the "protections" and limits/warnings and such as part of the basic design. But no FBW commercial airliner has failed to meet the basic aerodynamic requirements for stability and control if they all had ropes, levers, pulleys, cables, torque tubes, etc to move the ailerons, rudder and elevator. They are not the military or utility platforms and do not haul 200 folks about to visit aunt Clara.
So Boeing adds another thingie besides the STS speed stability doofer to meet Part 25 requirements and it gets signed off. Most of we pilots would handle the new thingie if and a BIG IF we knew it was added AND we were told what possibel failure indications existed AND we practiced a bit. GASP!! None of that was done.
My experience was in military planes and before each flight we had to sign off every little notice, directive and change and such before flying. On some mods we had to fly with an instructor before being cleared "solo". The MCAS mod required none of those things, and I have problems with not having seen a revolt by a thousand 737 pilots that only discovered MCAS after Lion 610 pranged.

'nuff bitching, and I close for now

Gums

A salute back to you

You point to a problem which i whole heartedly agree. https://www.pprune.org/images/infopop/icons/icon14.gif

Now can you also point to a solution in commercial service among the various nations flying these aircraft?

josephfeatherweight

14th Mar 2019, 02:55

Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.
Not only that, but you have to be sure the sim accurately represents what happens with such failures in the real aircraft - for a "behind the scenes" system such as MCAS, this is NOT guaranteed - yet.

Condor99

14th Mar 2019, 03:15

It seems that the German bureau of accident analysis refuses to receive the CVR/FDR from request of Etiopia... (BFU, Bundesstelle für Flugunfalluntersuchung, repeat afer me !)
So, the french BEA (= AAIB or NTSB or ATSB) will take care of this...

I'm not authorized to post a link/url, but search for :

francetvinfo.fr crash-aerien-en-ethiopie-les-boites-noires-seront-analysees-en-france on Google...

FCeng84

14th Mar 2019, 03:20

I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place! So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is. Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes. By the time he actually realises how out of trim he is, he's doing 350, and despite the stab still being at the same X° nose down since cut-out, the forces have multiplied. Now if there is any nose down attitude or reduction in power then there's absolutely no chance to recover.

Obviously all hypothetical, an airspeed disagree on takeoff could lead to circumstances similarly, or a multitude of other possible reasons, however, in the situation that I've hypothesized, it would almost certainly always end in a similar steep nose down attitude.

737 is not a FBW system with augmented elevator control. The elevator follows only the column. The pilot will know at all times when flying manually just how out of trim the airplane is by how much column force/displacement is needed to maintain the target pitch attitude. Having shut off electric stabilizer control, the workload associated with maintaining pitch trim is increased as it requires manual, mechanical rotation of the trim wheel, but the cues as to when trim is needed, in which direction, and how much are the same as what the pilot has seen for every hour of flying that airplane manually that he or she has done. As with every day flight with a completely healthy airplane, the amount of pitch trim required to recenter the column after having used that column to compensate for the pitching moment changes associated with thrust and configuration changes will be no different and thus the cue to provide pitch trim will be no different. The task of inserting that trim is higher workload, but nothing any 737 pilot (MAX or otherwise) should find particularly difficult to keep up with.

From your mention of "autotrim" I get the sense that you may not realize that when flying the 737 manually the automatic stabilizer control functions that are active (STS and MCAS) tend to drive the stabilizer away from trim thus making the pilot trim workload higher than it would be without them. The automatic stabilizer control is not there to "automatically trim the stabilizer". It is in fact there to "automatically untrim the stabilizer" such that the pilot has to provide column in the opposite direction yielding handling qualities and awareness that are dictated by the FARs.

Vessbot

14th Mar 2019, 03:21

edmundronald

14th Mar 2019, 03:37

Before the damages trials for Indonesian and Ethiopian take place, someone is going to have to run through a bunch of these scenarios in the sim, and see in what percentage of a few hundred trials of AoA sensor faults the pilots manage to survive even if they apply all recommended Boeing procedures.

Edmund

FCeng84

14th Mar 2019, 03:40

Just trying glean what flight regime MCAS needs to protect. So, they didn't want the column cutout switch to work because they envisioned pulling hard and not trimming. Trimming would normally return the column to neutral. Two things come to mind. Windshear escape in the clean config and steep turns with guys that don't trim. I (having the T-38 training mantra embedded, "trim trim trim") would trim during steep turns so that would not be a problem for me or MCAS. Of course steep turns are a simulator exercise so not really relevant. Again I ask why put out the original AD and not caution about being careful when pulling with the loss of MCAS.

Handling qualities regulations require starting from a wings level, trimmed condition and then demonstrating flying to high AOA (both by slowing and by executing a wind-up turn at constant speed) and showing that the stick force throughout the maneuver (flown without trimming) increases monotonically (i.e., the required pull does not decrease throughout the maneuver). These maneuvers involve insertion of enough aft column to go past the column cutout switch and thus MCAS must be able to continue to add airplane nose down stabilizer with the column pulled past the position of this switch.

On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.

Condor99

14th Mar 2019, 04:00

Where are the CVR/FDR boxes right now ?

Who knows ?

Halfnut

14th Mar 2019, 04:01

Sooooooooooooo when will they release a transcript of the CVR from the Lion Air crash?

jimtx

14th Mar 2019, 04:18

Handling qualities regulations require starting from a wings level, trimmed condition and then demonstrating flying to high AOA (both by slowing and by executing a wind-up turn at constant speed) and showing that the stick force throughout the maneuver (flown without trimming) increases monotonically (i.e., the required pull does not decrease throughout the maneuver). These maneuvers involve insertion of enough aft column to go past the column cutout switch and thus MCAS must be able to continue to add airplane nose down stabilizer with the column pulled past the position of this switch.

On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.

The T-38 did not have an elevator. It had a stabilator. But in all the other commercial transport aircraft I flew “trim trim trim” worked for me. Except for, thankfully, only in the simulator, stalls and wind shear events. But in any normal airline flying you woul expect to be in trim when sht happened. We don’t have “maneuvers” but if I did I would trim if I had an airplane that required it. I’m supposing that some current aircraft don’t require trim. I could adapt to that. There might be that some guys can’t adapt, old to new, young to old, not capable to required capable.

Super VC-10

14th Mar 2019, 04:32

i have had some dealings with transponders, and the rule of thumb is that.

Mode-c gives 1013 baro altitude.
Mode-s gives 1013 baro altitude.
Ads-b also gives 1013 baro altitude, to be compatible with the above.
Flarm and paw give gps altitude.

As far as i know, fr24 is simply picking up ads-b 1013 pressure altitudes, so you will need to know the qnh of the day, and the altitude of the airport, to calculate the true height of the aircraft. Transponders were designed for seperation on airways, not for separation with terrain, so the older units all used 1013 baro, and ads-b follows suit.

(if ads-b used gps alt, then atc would not be comparing like with like. However, newer systems like flarm and paw can happily use gps alt, because they all use gps, so they are comparing like with like.)

silver

metar HAAB 100500Z 06008KT 9999 FEW025 16/10 Q1029

Airfield elevation 2,334m / 7,625 ft

Condor99

14th Mar 2019, 05:44

Crash in Ethiopia: Germany can not analyze black boxes
http www.bfmtv.com/economie/crash-en-ethiopie-l-allemagne-ne-peut-pas-analyser-les-boites-noires-1651600 . html

Australopithecus

14th Mar 2019, 05:52

Crash in Ethiopia: Germany can not analyze black boxes
http www.bfmtv.com/economie/crash-en-ethiopie-l-allemagne-ne-peut-pas-analyser-les-boites-noires-1651600 . html

Dead link, but the gist of a google search using those terms is that Germany currently lacks the ability to assess this new version of the FDR. I do hope that there is a non-US avenue for analysis. I never used to feel that way, but lately I get to feeling a bit queasy getting between Americans and money.

Condor99

14th Mar 2019, 05:58

Dead link, but the gist of a google search using those terms is that Germany currently lacks the ability to assess this new version of the FDR. I do hope that there is a non-US avenue for analysis. I never used to feel that way, but lately I get to feeling a bit queasy getting between Americans and money.

Just add ".html" to the link (I'm not yet authorized to post a link/url).

France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...

dfens42

14th Mar 2019, 06:17

Just add ".html" to the link (I'm not yet authorized to post a link/url).

France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...
It's not like there won't be an FAA/NTSB team and Boeing reps in the room. I fail to see what the big deal is.

Condor99

14th Mar 2019, 06:48

Ethiopian Airlines on Twitter: "An Ethiopian delegation led by Accident Investigation Bureau (AIB) has flown the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) to Paris, France for investigation."

ManaAdaSystem

14th Mar 2019, 07:14

STS is subject to column cutout such that large column motion in opposition to STS stabilizer command will stop STS command. Not true with MCAS. This is an important differnce between these two automatic stabilizer control functions.

How large? I have tried to let it trim without counter trimming just to see how far out of trim the aircraft gets. I get more and more back pressure on the yoke but STS keeps trimming.
On top of that, STS trims on all departures, not only in the light aircraft, high thrust aft CG situation.
It’s a weird system that I could do without.

mfeldt

14th Mar 2019, 07:20

After 1000 feet I noticed a decrease in aircraft performance. I picked up that the autothrottles were not moving to commanded position even though they were engaged. I'm sure they were set properly for takeoff but not sure when the discrepancy took place. My scan wasn't as well developed since I've only flown the MAX once before. I manually positioned the thrust levers ASAP. This resolved the threat, we were able to increase speed to clean up and continue the climb to 3000 feet.

Shortly afterwards I heard about the (other carrier) accident and am wondering if any other crews have experienced similar incidents with the autothrottle system on the MAX? Or I may have made a possible flying mistake which is more likely. The FO (First Officer) was still on his first month and was not able to identify whether it was the aircraft or me that was in error.

So there was a captain unable to quickly grasp what was happening because it was only his/her second flight on the type, and an FO with less than month of experience who couldn't grasp what was wrong??? I'm never going to fly again!

DaveReidUK

14th Mar 2019, 07:25

I think the satellite data *could* refer to any ACARS maintenance information transmitted to Boeing and/or GE and/or Ethiopian.

It could also mean that, though the Canadians specifically referred to "satellite tracking data".

In effect, FR24 on steroids.

bill fly

14th Mar 2019, 07:59

As has been very well explained, the reason for MCAS was to cause ANU stick force to increase or at least not to decrease when AoA approaches stall angle. That was a certification requirement.
However, by repeating the trim input at remaining high AoA, something more than just desired stick force increase is achieved.
What is needed is a one time increment in stick force to bring the Max into line with the other 737 models - if that was the aim.
This can be achieved by adding feel spring force to the control run, cut in point determined by AoA.
If there were then a fault in the AoA signal, the increment would be applied - once - which would be trimmable and controllable.
The whole sorry idea of playing with the stab trim to achieve what is really a desired primary control feel correction is unnecessary and as we see, unsatisfactory and potentially dangerous.
A feel spring solution should satisfy the certification authorities and the desire by the manufacturer to keep the Max in the 737 family, rating wise.

fox niner

14th Mar 2019, 08:13

It was established yesterday evening that the BEA (France) is going to read them out.

They have arrived in Paris:

https://mobile.twitter.com/flyethiopian/status/1106068808454860800

EDLB

14th Mar 2019, 08:14

If the manufacturer is interested in technical solving the issue, then the real data FDR and CVR of both flights are required. With the money at stake I have no doubt he is. So why should you think Boing has any benefit with tampering FDR or CVR data? It will be difficult enough to restore customer trust into that plane. So anything short of a thorough analysis yielding a transparent technical solution scrutinised by all parties including the regulatory bodies will not do.
So Honeywell would be my first shot to ask, the recorders hand delivered and the restorrage overseen by some trustable and technical savvy people.
Ask Airbus guys and some of the national experts in the regulatory bodies to participate.

DaveReidUK

14th Mar 2019, 08:50

“Less Hair“ already answered your question and I do not have much to add: the BFU has limited resources and up to now there are no MAX in the country, so no surprise (to me) that they cannot read the FDR.

OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.

N600JJ

14th Mar 2019, 08:57

Er, aren't the LEAP engines manufactured by CFM, a joint venture between Safran (a French company) and General Electric ?

France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...

Has anyone criticized the work that was done by French BEA re. the analysis of data from AF447 involving both the French national carrier and an aircraft manufactured by European Airbus whose ties with France are well known to all? From a pure France's perspective AF447 was presumably much more critical to France than ET302 may ever be. And I doubt that anyone (sensible) in France feels happy that this is happening to Boeing today....

enginebird

14th Mar 2019, 08:59

OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.

Totally agree, not their smartest move.

groundbum

14th Mar 2019, 09:00

So there was a captain unable to quickly grasp what was happening because it was only his/her second flight on the type, and an FO with less than month of experience who couldn't grasp what was wrong??? I'm never going to fly again!

And here I was thinking a 737 was a 737 was a 737 was a 737 ;-)

G

Rated De

14th Mar 2019, 09:01

Has anyone criticized the work that was done by French BEA re. the analysis of data from AF447 involving both the French national carrier and an aircraft manufactured by European Airbus whose ties with France are well known to all? From a pure France's perspective AF447 was presumably much more critical to France than ET302 may ever be. And I doubt that anyone (sensible) in France feels happy that this is happening to Boeing today....

Certainement pas, nous sommes tous connectés!

Perhaps the CVR/FDR being sent to France may be a tacit recognition underneath pragmatism, that there needs to be other eyes looking at this?

FCeng84

14th Mar 2019, 09:03

How large? I have tried to let it trim without counter trimming just to see how far out of trim the aircraft gets. I get more and more back pressure on the yoke but STS keeps trimming.
On top of that, STS trims on all departures, not only in the light aircraft, high thrust aft CG situation.
It’s a weird system that I could do without.

The switch involved is the same one that interrupts pilot electric pitch trim if opposite the column displacement direction. I believe this interrupt is also active on the ground. When positioning the stabilizer for takeoff using wheel mounted thumb switch try moving the column in the opposite direction at the same time to see how far it has to be out of detent before stabilizer motion stops even though thumb switch remains activated. A note of caution that thumb switch input in opposition to column such that the column cutout activates if held for very long may trip a monitor designed to detect persistent contradictory column and trim commands. That might take some explaining. I apologize that I don't know the details on such monitoring (in particular how long the condition must persist before said monitor trips). I'm sure there must be some 737 savvy PPRUNErs out there who know and by the amount of traffic on this thread they are probably monitoring.

rcsa

14th Mar 2019, 09:28

OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.

Absolute guess here, but Lufthansa have managed and supervised ET's tech and mech support for many years, so it's possible the default response to a problem in Addis is 'send it to Germany', or 'ask the Germans'.

futurama

14th Mar 2019, 09:28

OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.
I don't think the ECAA is driving this decision to have the black boxes analyzed in Europe, and I didn't see them announcing anything in this regard.

Rather, I think this maneuvering is coming from Ethiopian Airlines -- more specifically, the airline's CEO, who has a lot of influence in the country's aviation sector.

ChicoG

14th Mar 2019, 09:35

Paris/Addis Ababa - Two black boxes from the Boeing 737 MAX aeroplane that crashed in Ethiopia arrived on Thursday in Paris for expert analysis, officials said, as regulators around the world awaited word on whether it was safe to resume flying the jets.

A spokesman for France's BEA air accident investigation agency said the flight data and cockpit voice recorders would be handed over to the agency later in the day.

https://www.iol.co.za/news/africa/ethiopianairlinescrash-black-boxes-arrive-in-paris-for-analysis-19877943

Cows getting bigger

14th Mar 2019, 09:37

ManaAdaSystem

14th Mar 2019, 10:00

The switch involved is the same one that interrupts pilot electric pitch trim if opposite the column displacement direction. I believe this interrupt is also active on the ground. When positioning the stabilizer for takeoff using wheel mounted thumb switch try moving the column in the opposite direction at the same time to see how far it has to be out of detent before stabilizer motion stops even though thumb switch remains activated. A note of caution that thumb switch input in opposition to column such that the column cutout activates if held for very long may trip a monitor designed to detect persistent contradictory column and trim commands. That might take some explaining. I apologize that I don't know the details on such monitoring (in particular how long the condition must persist before said monitor trips). I'm sure there must be some 737 savvy PPRUNErs out there who know and by the amount of traffic on this thread they are probably monitoring.

It works on ground. I have seen this when the wind push the yoke forward and I want to set takeoff trim. I need to pull the yoke back before I can engage the trim.
With STS it will continue to trim up even if I need to apply quite a lot of forward pressure to keep the nose from rising. I thing the parameters for the trim cut out to function are very high. Or possibly it doesn’t stop STS from operating.

Less Hair

14th Mar 2019, 10:01

France is one of the MAX engine Co-manufacturers. This is why they likely have all the software needed from the very beginning.

Rated De

14th Mar 2019, 10:07

To quote a 737 Max pilot:

"..what else don’t I know?"

From https://leehamnews.com/2019/03/13/commentary-boeings-tylenol-moment-and-the-need-for-radical-transparency/

"Herein lies an essential lesson for Boeing: When your reputation depends on safety, it does not matter what has been proven or who is at fault. What matters is that you are seen taking the lead to protect the safety of the public – at all costs."

Precisely, the old Boeing would not need reminding.
Nor would they have lobbied the President to intervene if they were certain the data supported their public rehearsed statements of safety.

N600JJ

14th Mar 2019, 10:08

And exactly how many F-reg MAX's are there I wonder .......
Not so much a question of D-reg or F-reg aircrafts here but more on Honeywell software (and potentially associated hardware), expertise, timescales and bandwidth I guess

Redbeard

14th Mar 2019, 10:09

It is quite unavoidable with a new model joining a fleet
i partially agree with you on that, yes the captain possible first/ second flight as one day you just have to start. But the decision to add a totally fresh out of school,FO, no experience in aviation is just bad planning and judgement of the airline.
wondering how much extra sim emergency training (if at all possible) crew’s got after the Lion crash and info given by Boeing

boxmover

14th Mar 2019, 10:12

Have we passed the point in modern aviation where it is not possible to (quickly) switch off all these pilot and performance aids and fly “manually”?

At very least, the last resort if flying in VFR conditions?

Mjb

With a aircraft with powered flying controls let alone fly by wire signaled power controls define what manual control is.

Without any force feedback and at higher speeds it would be easy to badly over stress an aircraft.

plus

If you want pilots trained and current to fly without the “aids to flight” under stressful conditions you will need significant training both initial and recurrent. That won’t come cheap.

procede

14th Mar 2019, 10:15

France is one of the MAX engine Co-manufacturers. This is why they likely have all the software needed from the very beginning.
More that they are the home of Airbus and Dassault and electronics manufacturers such as Thales.

Rated De

14th Mar 2019, 10:23

“Boeing has determined — out of an abundance of caution and in order to reassure the flying public of the aircraft’s safety — to recommend to the FAA the temporary suspension of operations of the entire global fleet of 371 737 MAX aircraft,”

Does anybody find it odd, that Boeing's public statement is attempting to suggest they the company 'ordered' the grounding?
Isn't that Cart before the Horse?
Or is it evidence of regulatory capture??

infrequentflyer789

14th Mar 2019, 10:27

OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.

<cynic mode> First announcement for political reasons (i.e. not France) then unavoidably changed to France for technical reasons?

HarryMann

14th Mar 2019, 10:28

So MCAS was born from meeting certification requirements re: stick force per alpha (or maybe stick force per G) in the 》1G range.

Can anyone tell.ne authoritatively whether this requirement stems from stall or maneouvre overload prevention ?

Oh! Or both!

thanks

boxmover

14th Mar 2019, 10:45

averow

14th Mar 2019, 10:52

Your summation of the situation 'bill fly' is much appreciated. There seems to me to be something "off" about the concept of MCAS as it currently exists, and seems to be causing problems for flight crews. The repetitive, insidious nature of the correction is what baffles me. I do not understand why this mismatch of "real life application" of MCAS in its intended role was not thoroughly wrung out during the test pilot phase.

boxmover

14th Mar 2019, 10:59

i partially agree with you on that, yes the captain possible first/ second flight as one day you just have to start. But the decision to add a totally fresh out of school,FO, no experience in aviation is just bad planning and judgement of the airline.
wondering how much extra sim emergency training (if at all possible) crew’s got after the Lion crash and info given by Boeing

At lots of airlines crews get 4 days per year in the sim, either 4 individual days or 2 blocks of 2 days. Few if any airlines will have added extra sim trips. Adding sim trips is not straight forward, you need both sim capacity and the ability to take crews off flying. These days most airlines have very little slack in their system.

Sailvi767

14th Mar 2019, 11:48

PerPurumTonantes

14th Mar 2019, 11:49

Anyone like to hazard a guess, assuming the MCAS is indeed the problem, what Boeing's technical solution will be (not to mention how long it will take!)?

Input from minimum 2 AOA vanes, disabling (with warning) if disagreement
Automatic disabling of MCAS if pilot counters with manual trim

Assuming everyone well motivated, which fleet grounding should do nicely, here's a guess on timescales:
Redesign and recode: 2 weeks
Safety case, prototype, testing, certification: 6 months
Fleet fitment: 3 months
My consultancy fees: $2.4m

dead_pan

14th Mar 2019, 12:03

Luc Lion

14th Mar 2019, 12:03

Adding a spring system would involve incorporating new hardware on the Max. That new hardware would come at an on cost. The attraction of the Boeing solution is that it uses the existing hardware plus some new software.Boeing got the cheaper solution certified so what is there motivation to go to a more expensive solution.
The question is is should it have been certified.
Why adding a spring ?
There is already an Elevator Feel System (EFS) which is controlled by a calculator, the Elevator Feel Computer module, thus it is controlled by software.

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/640x430/screen_2bshot_2b2018_11_12_2bat_2b8_33_51_2bpm_b227691f6591b f201797845a85d5c851207ba902.png
The elevator feel computer receives pitot pressure, hydraulic pressure, and mechanical inputs. The elevator feel computer sends metered hydraulic pressure output to the dual feel actuator on the elevator feel and centering unit. Feel hydraulic pressure in the elevator feel computer varies between 180 psi (base feel) and 1400 psi (maximum). The actual feel pressure to the dual feel actuator is determined by the hydraulic pressure from system A and system B, pitot pressure, and stabilizer mechanic
(from www.satcom.guru (https://www.pprune.org/www.satcom.guru))

So, if the issue at stake was just about restoring the linearity of the control pitch force versus AoA angle, this could have been done just by enhancing the EFS system algorithms.
Just one little issue: the FCC doesn't feed the Elevator Feel computer with the AoA information.

It bet that Boeing engineers have balanced this against creating a new software function called MCAS whose implementation only affects the FCC module.
Now that the implementation costs of MCAS appear to be vastly different from the initial estimates, Boeing might reconsider enhancing the EFS.

I mean, that route might be preferable to adding even more complexity to a MCAS module whose existence and purpose is debatable.

WHBM

14th Mar 2019, 12:07

Originally Posted by mfeldt https://www.pprune.org/images/buttons/viewpost.gif (https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa-post10417828.html#post10417828)So there was a captain unable to quickly grasp what was happening because it was only his/her second flight on the type, and an FO with less than month of experience who couldn't grasp what was wrong??? I'm never going to fly again!It is quite unavoidable with a new model joining a fleet
Perfectly possible. Train the training captains first, let them have some real, non-sim experience of it on test flights, all to a plan, start revenue flights with two captains, then progressively have them train the FO's, starting with the experienced ones. It's not hard to come up with that. Isn't devising this sort of transition what the role of Chief Pilot is all about ?

EternalNY1

14th Mar 2019, 12:15

Input from minimum 2 AOA vanes, disabling (with warning) if disagreement
Automatic disabling of MCAS if pilot counters with manual trim

Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".

Maninthebar

14th Mar 2019, 12:21

Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".

And add training module for crew type rating

bill fly

14th Mar 2019, 12:27

LL,

Thanks. That would work, while requiring differing software and inputs for Max and rest of the family, however.
Could be that a dedicated separate system would be simpler to calibrate and quicker to certify.

El Bunto

14th Mar 2019, 12:36

Another SLFie who may be stating the obvious, but surely the goal of any airframer is to produce an aircraft that even the minimum standard of pilot can fly and have a decent chance of successfully troubleshooting in the event of something going awry? Not prejudging anything BTW

The FAA language is "a pilot of average skill".

However the first time such a pilot now gets behind the yoke is after the aircraft has been certificated, sold to an airline, built, delivered... Maybe they should involve FO Joe Average a bit earlier in the lifecycle.

Gone are the days when airline chief pilots would schlepp off to Seattle and throw the thing around the sky for a while before telling the executives whether it was suitable to buy. Now if it promises a 1% operational cost saving it is bought straight off the CAD screen.

Back in the 1960s there was even a BOAC inspection and flight-test team at Everett!

Luc Lion

14th Mar 2019, 12:44

With STS it will continue to trim up even if I need to apply quite a lot of forward pressure to keep the nose from rising. I thing the parameters for the trim cut out to function are very high. Or possibly it doesn’t stop STS from operating.

ManaAdaSystem,
look at the diagram below ; the "control column stab trim cutout switches" only operate on the electric path of the electric trim buttons.
The STS is on the other electric path, the path of the autopilot system.
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1024x768/b737_ng_flight_controls_48_1024_35f857abc2872868e1c583e3239a 290377cc5a5b.jpg

PerPurumTonantes

14th Mar 2019, 13:04

Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".

Yep personally I would pull the thing out and design the airframe properly. Or, second best, properly integrate with existing stab trim/efs.

But the question was what will Boing do. And the answer is, whatever gets the fleet flying the quickest.

dgordon42

14th Mar 2019, 13:08

Why adding a spring ?
There is already an Elevator Feel System (EFS) which is controlled by a calculator, the Elevator Feel Computer module, thus it is controlled by software.

The Elevator Feel Computer in all models of the B737 is a mechanical computer. It shown in the drawing you posted. It varies elevator feel by using pitot pressure to regulate hydraulic pressure to an actuator which tensions a spring. The faster you fly the stiffer the elevator feels to the pilot. No software involved!

Dave.

oldoberon

14th Mar 2019, 13:10

These were discussed before - they are not MCAS as they occurred with autopilot ON, A previous poster pointed out that this change of level happens on NG as well not only 'this aircraft' and is due to pressure setting mismatch.

The purpose of ASRS is to highlight issues that need attention without come back on crews that may have made errors. A common error (and pressure setting problems are VERY common around 2 a day reported) indicates that attention is needed in one or more areas. Unfortunately, journalists are not capable of reading these reports and understanding what is being reported indeed they do NOT want to understand they want things to be as inflammatory as possible so readers click on their headlines. This is not really useful to the industry.

Ian I assume you read all of the narratives.

A few quick points from memory
Pilots not being able to usual scan and see what they are looking for
Pilots not familiar with new displays
Pilots not Knowing what the "Maint" msg means and unable to find it in pilots notes
Pilots not knowing what a particular switch labelled SEL was for.

That is abysmal conversion training (classroom and sim) , abysmal documentation and DANGEROUS

Vilters

14th Mar 2019, 13:16

Choose : You just got airborne and cleaned up in IMC;

2 Warnings come up, screaming and flashing, ringing and tinkling.
- Overspeed
- STALL

Choose what you will do because : Some failing sensors, or some twisted code lines, are giving you and your co-pilot conflicting information and warnings.

Then, like in most modern airframes where ( willing or not) some parts of the flight control management system are ALWAYS ON, the airplane itself starts trimming itself.

But to what information IS the airplane trimming itself? ? ? ? ?
Do you know?
Does it know?

Food for thought.

silverstrata

14th Mar 2019, 13:17

I am going to assume you don’t fly for a living. There is no way you would not recognize a stab out of trim condition while hand flying the aircraft. In addition the aircraft would only accelerate like you portray if the pilot failed to adjust power to maintain the desired airspeed.

Sure about that? Someone new to the aircraft, captain average, and a bit tired.

At 3,000 ft, the stick shaker starts going like mad, causing a hell of a racket, and you think you have an airspeed problem and might be stalling. Sure, the controls are getting heavier and heavier, and you trim a bit for that, but this is caused by the aircraft stalling - isn’t it? (You cannot hear the trimmer, over the din of the stick-shaker.) So you have to let the nose drop, untill you are sure you have enough airspeed.

Ok, you are getting a bit low now, time to pull back. Ahh, but the aircraft will not respond - pull as hard as you like, but the stick feels jammed (you need 60 kg of force to counter full stab-trim). You shout to the f/o to help pull, but the ground is coming up fast.... End of short story...

Silver

BrandonSoMD

14th Mar 2019, 13:22

The handling differences due to thrust line may have been tuned out but it wasn't by MCAS. Windup turns are done with set thrust.

I think that deserves some clarification. I don't fully agree.

I'm a 30-year flight test engineer and am currently helping to rewrite the handling qualities flight test manual for the US Navy Test Pilot School. We focus more on military than transport aircraft, but we do test and fly 737-derivative airplanes (P-8A Poseidon and the C-40 Clipper) and the test methods are universally applicable.

Windup turns are done with set thrust, yes. Power is set as required to maintain the specified airspeed. What is being compared is the response of the airframe to increasing AOA or g at a fixed airspeed, and throttles are fixed during the maneuver to avoid contaminating the results with another independent variable. Several things can be learned from WUTs, including control force or deflection as a function of load factor or AOA, buffet characteristics as a function of AOA, and structural characteristics as a function of g.

While each test point is conducted at a specific power setting, the tests are typically conducted at a range of power settings. This provides a chance to assess the effect of power setting on the various aforementioned characteristics.

MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines. As such, it is a handling qualities difference that is definitely related to thrust line changes. Those differences would typically be revealed by a series of WUT test points. In this case, a WUT at high thrust would be worse, because of the increased pitch-with-power tendencies.

Capn Bloggs

14th Mar 2019, 13:32

MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines.
I thought the MCAS increases the (lightening) stick force required to keep pulling back as AOA increases (so pilots have less tendency to pull thru into a stall), the more pronounced nose-up pitch occurring because of the aerodynamic lift generated by the bigger, more forward-positioned engine cowls.

In any case, the mention of wind up turns in the context of pax 737s is a bit of a furphy, IMO. The main issue is high AOA and reducing stick force, however you arrive at the high AOA.

Vilters

14th Mar 2019, 13:33

I think that deserves some clarification. I don't fully agree.

I'm a 30-year flight test engineer and am currently helping to rewrite the handling qualities flight test manual for the US Navy Test Pilot School. We focus more on military than transport aircraft, but we do test and fly 737-derivative airplanes (P-8A Poseidon and the C-40 Clipper) and the test methods are universally applicable.

Windup turns are done with set thrust, yes. Power is set as required to maintain the specified airspeed. What is being compared is the response of the airframe to increasing AOA or g at a fixed airspeed, and throttles are fixed during the maneuver to avoid contaminating the results with another independent variable. Several things can be learned from WUTs, including control force or deflection as a function of load factor or AOA, buffet characteristics as a function of AOA, and structural characteristics as a function of g.

While each test point is conducted at a specific power setting, the tests are typically conducted at a range of power settings. This provides a chance to assess the effect of power setting on the various aforementioned characteristics.

MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines. As such, it is a handling qualities difference that is definitely related to thrust line changes. Those differences would typically be revealed by a series of WUT test points. In this case, a WUT at high thrust would be worse, because of the increased pitch-with-power tendencies.

That is all good and well, and always works when all sensors are giving you and the systems the correct information.

AF447 => An iced over AOA probe gives false info, and it does not matter what happened the next minutes, they never figured out in time what the actual problem was.
The B-2 crash => See? With failing sensors there simply is NO TIME.
The X-31 crash => (Where pitot anti-ice was not connected) => The plane goes out of control SO FAST, the only way out is to eject.

When given false information from failing sensors, (and not knowing it) or the failure codes redraw so fast on screen that you simply can not keep track of all of them => It is game over.

BrandonSoMD

14th Mar 2019, 13:37

Sure about that? Someone new to the aircraft, captain average, and a bit tired.
At 3,000 ft, the stick shaker starts going like mad, causing a hell of a racket, and you think you have an airspeed problem and might be stalling. Sure, the controls are getting heavier and heavier, and you trim a bit for that, but this is caused by the aircraft stalling - isn’t it? (You cannot hear the trimmer, over the din of the stick-shaker.) So you have to let the nose drop, untill you are sure you have enough airspeed.

Ok, you are getting a bit low now, time to pull back. Ahh, but the aircraft will not respond - pull as hard as you like, but the stick feels jammed (you need 60 kg of force to counter full stab-trim). You shout to the f/o to help pull, but the ground is coming up fast.... End of short story...

This is one of the better comments in this discussion. As a long-time flight test engineer with personal experience flying jumpseat aboard Boeing commercial-class airplanes during many test flights, and many hundreds of hours in the related simulators both testing and flying the simulators, I have personally witnessed aircrew in simulated emergency situations with all four feet standing on the bottom of the forward display panel to gain enough leverage to pull with >100 lb on the yoke to control the airplane (and specifically in runaway stab trim and hyd-fail situations). Nobody had a hand free to fiddle with manual trim or deal with the stab trim cutout switch and its guard (at least on the aircraft types I've tested).

Yes, these things are addressed in pilot training. But I've also watched extremely-intelligent and supremely-trained flight test pilots miss very obvious things due to the confusion surrounding automation (I helped test a major glass-cockpit upgrade to a Boeing 707-derived military jet, which included adding modern-day Honeywell autopilot systems). I've personally sat behind them in the jump seat and watched them completely miss what was going on outside the window, as two pilots and a flight engineer got wrapped up trying to figure out some stupid aspect of VNAV operation, to the point where a safety "knock it off" call had to be made to get them to break their "target fixation" on the troubleshooting.

Watch the video of the recreation of the cockpit troubleshooting in the AeroPeru crash due to tape covering the Pitot-static ports... two well-trained pilots so confounded by an airplane acting differently than they expected, that some very basic hand-flying principles and alternate information sources were missed for nearly an hour.

It's easy to armchair-quarterback a situation after the fact - but I've seen it all happen enough times to recognize the reality of the man-machine interfaces.
Ultimately, if a design is such that a pilot can get confused enough to lose all situational awareness, the problem fundamentally is a poor design, not just pilot training or problem-fixation.

BrandonSoMD

14th Mar 2019, 13:38

That is all good and well, and always works when all sensors are giving you and the systems the correct information.

AF447 => An iced over AOA probe gives false info, and it does not matter what happened the next minutes, they never figured out in time what the actual problem was.
The B-2 crash => See? With failing sensors there simply is NO TIME.
The X-31 crash => (Where pitot anti-ice was not connected) => The plane goes out of control SO FAST, the only way out is to eject.

When given false information from failing sensors, (and not knowing it) or the failure codes redraw so fast on screen that you simply can not keep track of all of them => It is game over.

You will probably find a lot of things to learn and appreciate in this video of the AeroPeru crash due to Pitot-static port blockage.
https://www.dailymotion.com/video/x6m3uwb

boxmover

14th Mar 2019, 13:42

Sure, but I bet there is plenty of motivation now we know how it works/fails.

See the teacup a few posts further up “If you think safety is expensive... etc”

I agree the decision making process that got to the current system and its certification will come under a lot of scrutiny in the next few weeks.

boxmover

14th Mar 2019, 13:47

How much longer could Boeing build new NGs?

If it had customers it could build them almost for ever.

The bigger question is how long would it take to spin up the production of NG engines and other parts. I suspect that getting back to building 100 plus NG engines per month would take 6 plus months to fully achieve.

Maninthebar

14th Mar 2019, 13:49

If it had customers it could build them almost for ever.

The bigger question is how long would it take to spin up the production of NG engines and other parts. I suspect that getting back to building 100 plus NG engines per month would take 6 plus months to fully achieve.

They will almost certainly be able to divert resources budgeted to the MAX towards other airframes

boxmover

14th Mar 2019, 13:56

Perfectly possible. Train the training captains first, let them have some real, non-sim experience of it on test flights, all to a plan, start revenue flights with two captains, then progressively have them train the FO's, starting with the experienced ones. It's not hard to come up with that. Isn't devising this sort of transition what the role of Chief Pilot is all about ?

These days the roll of the Chief Pilot is to get the program flown at minimum cost. The will design a program that meets the minimum legal standards and if they think it necessary a bit above that. Training Captains off line flying non revenue flights is way beyond what’s going to happen unless it’s legally mandated.

WHBM

14th Mar 2019, 13:59

The FAA language is "a pilot of average skill".

However the first time such a pilot now gets behind the yoke is after the aircraft has been certificated, sold to an airline, built, delivered... Maybe they should involve FO Joe Average a bit earlier in the lifecycle.
This seems a poor FAA perspective. By definition, 50% of pilots will be below that average skill level.

Particularly when they only have 200 hours total.

ManaAdaSystem

14th Mar 2019, 14:09

ManaAdaSystem,
look at the diagram below ; the "control column stab trim cutout switches" only operate on the electric path of the electric trim buttons.
The STS is on the other electric path, the path of the autopilot system.
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1024x768/b737_ng_flight_controls_48_1024_35f857abc2872868e1c583e3239a 290377cc5a5b.jpg

So this means the STS system will trim even if the column cut out switches are in the cut out position?

DaveReidUK

14th Mar 2019, 14:12

Does anybody find it odd, that Boeing's public statement is attempting to suggest they the company 'ordered' the grounding?
Isn't that Cart before the Horse?
Or is it evidence of regulatory capture??

No, it's not odd, although the wording is slightly misleading.

My understanding is that, while regulators like the FAA, EASA, etc have imposed territorial bans on the Max flying through the airspace that they have jurisdiction over, Boeing has sought the grounding of the worldwide fleet (I don't know if that has actually happened yet).

The FAA, as well as being responsible for what is and isn't allowed in US airspace, is also the continuing airworthiness authority for the 737. It has the power to grant a request by Boeing to temporarily suspend the aircraft's Type Certificate (in respect of only the Max, obviously). If it did so, other airworthiness authorities (EASA, ANAC, etc) would have no option but to follow suit and the Max would be effectively grounded worldwide.

CRayner

14th Mar 2019, 14:23

This seems a poor FAA perspective. By definition, 50% of pilots will be below that average skill level.

Particularly when they only have 200 hours total.

The use of average here is sloppy. Leaving out of account the numerical quantification of skill, and its distribution among pilots, it is quite possible that a majority of them are below average. However, what I want is the aeroplanes I travel in to be manageable safely by pilots of minimum allowable skill. Not every flight deck will be occupied by superhero pilots. If the first officer has just got his licence I want the captain to be a senior trainer, and if the captain has just been promoted then please may his co-pilot be of considerable experience on the type.

formulaben

14th Mar 2019, 14:36

Another SLFie who may be stating the obvious, but surely the goal of any airframer is to produce an aircraft that even the minimum standard of pilot can fly and have a decent chance of successfully troubleshooting in the event of something going awry? Not prejudging anything BTW
Therein lies the problem. What would be your minimum standard? Aviation authorities have different standards. Do you happen to know what the FO had for total flight time? And what was the Captain's total time in airframe? If you take the time to discover these significant facts, then that should scare you.

I'm not letting Boeing off the hook for such a poor design, but there's a reason that several other crews have documented this very issue and landed safely.

Zeffy

14th Mar 2019, 14:42

NTSB Sends Additional Investigators to Assist in Ethiopian Investigation (https://www.ntsb.gov/news/press-releases/Pages/NR20190314.aspx)
3/14/2019

WASHINGTON (March 14, 2019) —The U.S. National Transportation Safety Board (http://www.ntsb.gov/)is dispatching three investigators to France Thursday to assist with the downloading and analysis of flight recorders from the Boeing 737 MAX 8 that crashed Sunday near Addis Ababa, Ethiopia.

The NTSB investigators have expertise in recorders, flight crew operations and human factors. The French Bureau d'Enquêtes et d'Analyses (BEA) will be downloading the flight data recorder and cockpit voice recorder in support of the Ethiopian investigation.

The investigation is being led by the Ethiopian Aircraft Accident Investigations Bureau in accordance with the standards defined in International Civil Aviation Organization (https://www.icao.int/) Annex 13. The NTSB appointed an accredited representative to the investigation under the ICAO standards because the airplane was manufactured in the United States. All investigative data regarding the investigation will be released by Ethiopian authorities.

For more information on NTSB participation in foreign investigations go to: https://go.usa.gov/xEswV.

The NTSB investigators dispatched to France will work in coordination with investigators on the ground in Addis Ababa. Those investigators were sent immediately after the accident and have been integral to the efforts underway in Ethiopia. They are being assisted by technical advisers from the Federal Aviation Administration, Boeing and GE/Safran, the manufacturer of the engines.

The NTSB is an independent U.S. federal agency charged with investigating transportation accidents and issuing recommendations to improve safety.###

sonicbum

14th Mar 2019, 14:45

If the first officer has just got his licence I want the captain to be a senior trainer, and if the captain has just been promoted then please may his co-pilot be of considerable experience on the type.

Amazingly enough in many realities in EASA as well as a few others jurisdictions worldwide, You will find that a newly promoted Captain with 100 hours (yes one hundred) PIC time is considered "experienced" and can hence fly with any newly 250 hours released FO. Forget Senior Trainers flying with released FOs, hence non training flights, that's "not efficient" or having experienced (and skilled, which is not always the same) FOs to fly with newly promoted Capts as well. Let's enjoy the deregulation.

Vilters

14th Mar 2019, 14:54

If the airframe/sensors are feeding the pilots/systems with wrong information, it does not matter if they have 20.000 or 200 hrs PIC.
If at high speed and low altitude as in this case, there is NO time.
If error codes refresh so fast on screen that you can not follow them visually? You have no time to fall back on experience and evaluate and have mere minutes/seconds till impact.

cervo77

14th Mar 2019, 14:56

For those who want to understand how we came to this amateur job:

It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines. The nacelles for the MAX are larger and placed higher and further forward of the wing,

By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.

The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity will contribute to destabilize the aircraft in pitch.

The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft’s natural tendency to Dutch Roll = Wagging its tail).

Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described l which assisted the pilot to exit the stall.

The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt.

The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings.

But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the manoeuvre has a high pitch ratio. The aircraft’s inertia can then provoke an over-swing into stall AOA.

To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.

It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.

It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.

How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.

They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.

Source: https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/

Unfortunately the lion and Ethiopian's pilots have not had this chance

DaveReidUK

14th Mar 2019, 15:05

By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.

Almost, but not quite. The Max has typically 2-3 inches less ground clearance under the engines than the NG.

Otherwise, an excellent summary of the issues, though you might want to delete your other copy of the same post in the Software Fixes thread as the mods tend not to like cross-posting the same thing twice.

TerryKing

14th Mar 2019, 15:06

Journalists tend not to involve themselves in discussions but prefer to just lift chunks of it, often out of context, and don't even have to register as this is a public site.

Some of us Journalists are Engineers who try to write clear explanations of complex situations with unknown variables, that the average reader will understand.

The last 2 days of articles I've read sure could use a LOT more of that approach.

How would you (guys) react to a serious, well-stated question that could clarify some of the complexities of THIS situation, from an admitted Journalist?

rog747

14th Mar 2019, 15:07

Just recalled this from 1989 - 30 years ago...

Most of the world's 46 new Boeing 737-400 jetliners have been grounded in recent days after an engine type that has become increasingly suspect failed twice in the last week.
The airplanes affected are the 28 foreign 737-400's that are powered by that engine and 5 more planes, all flown by Piedmont Airlines, which use a similar engine.
The groundings followed an advisory, issued by Boeing on Tuesday, that urged airlines not to fly the planes until engine parts were replaced and power output was restricted. A Boeing 737-400 using the same engine crashed in Britain in January, killing 47 people a British Midland Airways 737-400 G-OBME

The Boeing advisory was followed by an emergency airworthiness directive issued yesterday by the Federal Aviation Administration. That directive officially grounded the Piedmont planes, which, having already been taken out of service and repaired, according to the Boeing advisory, were expected to resume flying today.
The engines involved are the CFM56-3C in the foreign planes and the CFM56-3B in the Piedmont planes.

In its emergency order, the F.A.A. warned that without the modifications the engine's fan blades might fracture, causing ''a complete loss of engine power.'' Engines that had failed on British 737-400's this past week showed signs of such fractures. In the Air Europe, BMA, Dan Air and Air UK Leisure fleets.

The most recent problems with the engine developed last Friday, when a Dan Air 737-400 carrying 100 passengers from London to Menorca returned to London after developing severe vibration in one engine. On Sunday, a Boeing 737-400 flown by British Midland Airways also had to return to London after developing engine trouble.
Piedmont Airlines, whose parent company is USAir Inc., is the sole operator of the 737-400 in this country. Although the Piedmont planes are powered by a different model engine, they had been flown at the higher power levels while being tested by Boeing and therefore fell under the F.A.A.'s emergency order.

cervo77

14th Mar 2019, 15:09

Almost, but not quite. The Max has typically 2-3 inches less ground clearance under the engines than the NG.

Otherwise, an excellent summary of the issues, though you might want to delete your other copy of the same post in the Software Fixes thread as the mods tend not to like cross-posting the same thing twice.

okay
done!

Falcon666

14th Mar 2019, 15:11

FDR printout of Lionair flight is now on “US grounds all Max’s “ thread

canyonblue737

14th Mar 2019, 15:38

Unfortunately the lion and Ethiopian's pilots have not had this chance

cervo77 obviously a well thought out and accurate explanation of MCAS and why it exists. as a Captain on the 737 MAX and previous generation 737s I don't agree with this last statement of yours, the Ethiopian crew *was* trained about MCAS per their CEO as all 737 MAX pilots in the world were by emergency AD after the Lion Air accident. further while i fully admit that a great deal of confusion can exist if you aren't aware of MCAS because of yoke behavior etc. it doesn't prevent one important fact being true, if you have improper trimming occurring that is not being made by you, the pilot, the stab trim cutout switches are right next to you and have been for decades on this aircraft. they fix this. heck you can physically grasp and hold the trim wheel itself and it will prevent this. lots of blame to go around here and hopefully when it comes to MCAS the software fix coming shortly as Boeing describes is very comprehensive (as it should have been on day 1.)

DaveReidUK

14th Mar 2019, 15:44

The perils of posting something without attributing it. :O

boxmover

14th Mar 2019, 16:03

They will almost certainly be able to divert resources budgeted to the MAX towards other airframes

Yes, but the lead times of some of the arts needed to build NG engines are not short, even if money is thrown at the problem.
To go from low rate production mostly for spares back up to more than 100 a month won’t be quick.

cervo77

14th Mar 2019, 16:16

cervo77 obviously a well thought out and accurate explanation of MCAS and why it exists. as a Captain on the 737 MAX and previous generation 737s I don't agree with this last statement of yours, the Ethiopian crew *was* trained about MCAS per their CEO as all 737 MAX pilots in the world were by emergency AD after the Lion Air accident. further while i fully admit that a great deal of confusion can exist if you aren't aware of MCAS because of yoke behavior etc. it doesn't prevent one important fact being true, if you have improper trimming occurring that is not being made by you, the pilot, the stab trim cutout switches are right next to you and have been for decades on this aircraft. they fix this. heck you can physically grasp and hold the trim wheel itself and it will prevent this. lots of blame to go around here and hopefully when it comes to MCAS the software fix coming shortly as Boeing describes is very comprehensive (as it should have been on day 1.)

If the engineers did not invent this MCAS system for the 737 max, and that the trim system remained 100% identical to what we have on the 737-800

question: what would be the result on the way of flying this 737 max ? a huge effort required to pull and push the yoke ?? I am curisous to know

boxmover

14th Mar 2019, 16:18

As has been said many times before, if you think training is expensive, try having a serious airliner accident

What you say is completely true.
Have you met an airline bean counter that gets it? They tend to look at today’s costs an hope luck and low odds will work in their favour.

etrang

14th Mar 2019, 16:25

Does anybody find it odd, that Boeing's public statement is attempting to suggest they the company 'ordered' the grounding?
Isn't that Cart before the Horse?
Or is it evidence of regulatory capture??

No, it's just PR management. Once grounding becomes inevitable Boeing will focus on damage limitation and try and claim some of the credit.

jimtx

14th Mar 2019, 16:27

I think that deserves some clarification. I don't fully agree.

I'm a 30-year flight test engineer and am currently helping to rewrite the handling qualities flight test manual for the US Navy Test Pilot School. We focus more on military than transport aircraft, but we do test and fly 737-derivative airplanes (P-8A Poseidon and the C-40 Clipper) and the test methods are universally applicable.

Windup turns are done with set thrust, yes. Power is set as required to maintain the specified airspeed. What is being compared is the response of the airframe to increasing AOA or g at a fixed airspeed, and throttles are fixed during the maneuver to avoid contaminating the results with another independent variable. Several things can be learned from WUTs, including control force or deflection as a function of load factor or AOA, buffet characteristics as a function of AOA, and structural characteristics as a function of g.

While each test point is conducted at a specific power setting, the tests are typically conducted at a range of power settings. This provides a chance to assess the effect of power setting on the various aforementioned characteristics.

MCAS is (at the core) merely a trim application system, designed to reduce the control forces which develop at higher AOA and g with the new-and-repositioned engines. As such, it is a handling qualities difference that is definitely related to thrust line changes. Those differences would typically be revealed by a series of WUT test points. In this case, a WUT at high thrust would be worse, because of the increased pitch-with-power tendencies.
MCAS is there to increase, not decrease, stick force. That stick force either becomes non linear or reverses (need to ask Boeing) at high AOA due to the aero effect of the new engines nacelles. I'm not sure there are any thrust line changes to the handling of the Max. The engines were re-positioned forward and UP.

Aloha_KSA

14th Mar 2019, 16:29

Have we ruled out the Max's FBW spoilers?! On the NG and previous the spoilers/ speed brake were cable/ hydraulic. On the MAX they are fly by wire. The change from cable/ hydraulic to fly by wire is a *HUGE* change in the flight control regime. The Max spoilers have various complicated automatic triggers that could have a complex interaction with other systems. On the NG and previous the symmetrical spoiler deployment could be overridden by stowing the speed brake handle. The automatic deployment is very difficult to override on the Max. One has to reach up and move a guarded switch. That motion is not a memory item nor is it intuitive. On the NG and previous, symmetrical deployment of the speed brakes / spoilers was indicated by motion of the speed brake handle. On the Max the spoilers deploy for various MCAS and non-normal scenarios without proportional movement of the speed brake handle. That means the pilots (1) are not aware of their deployment, and (2) cannot easily override their deployment. IMHO the precipitous and unrecoverable descent would be consistent with un-commanded spoiler deployment. The FDR will confirm or refute my opinion, but regardless, changing a major flight control from manual - cable/ hydraulic to fly by wire is very suspect. I don't know if there is any precedent for a derivative aircraft being introduced with a major flight control system being changed from manual control to fly by wire without a new type or at least difference training being required. The differences training between NG and Max was about 4 hours of CBT... I have NG pilot friends who were signed off to fly the MAX without so much as a sim session.

sky9

14th Mar 2019, 16:42

As a retired oldie this problem seems to have similarities with the BAC1-11 deep stall problem during certification. The 1-11 and Trident had the problem of the wing shielding the T tailplane and the aircraft going into a deep stall with no aerodynamic flow over the tailplane and elevator. This issue was resolved by having both a stick shaker and finally a stick push, both being controlled by AOA vanes that shook the daylights out of the control column followed by a definite push down. Recovery from the stick shake was the same as the 737 200, relax the back pressure and apply power for minimum height loss.

If my understanding is correct there is only one AOA vane on the Max why isn't there a dispatch requirement for 3 and another for redundancy making 4 vanes. At least the MCAS software would then be operating with correct information. The original 737-200 had one AOA vane and there was an incident of an aircraft rotating on take off straight into a stick shake that remained on at all indicated airspeeds.

jimtx

14th Mar 2019, 17:22

If the engineers did not invent this MCAS system for the 737 max, and that the trim system remained 100% identical to what we have on the 737-800

question: what would be the result on the way of flying this 737 max ? a huge effort required to pull and push the yoke ?? I am curisous to know

Just guessing. 1. You're in a clean hold off autopilot and you let your speed decay, but not to stick shaker, while rolling into a bank and you pull to maintain altitude and either you have to let off the pull or actually push to keep the nose from rising more than you want.
2. You are clean on long final with windshear in the vicinity when you get a windshear warning and perform the escape. When you click off the autopilot and pull the pull force has to decrease or reverse to a push to maintain the attitude you want.

dsc810

14th Mar 2019, 17:26

What you say is completely true.
Have you met an airline bean counter that gets it? They tend to look at today’s costs an hope luck and low odds will work in their favour.

...and their customers are exactly the same
They know the low cost cheap flights risk a monumental mess up every now and then that leaves them stranded for XX hours in some ghastly place
But they also just hope the odds work in their favour and its not them that get caught.
Its the same everywhere: people complaining how some corporate is cutting services or not doing it "properly" while the same complainers are busy bodging up their electrics, roof, guttering whatever and hope the next purchaser does not notice.
So its circular - each side drives the next, and round and round we for ever lower costs taken from somewhere - 'cos you can have the most wonderful,ticketing,maintenance, backup whatever regime but if you have no customers as they have all gone to the next cheapest down the road you are going bust.

wheelsright

14th Mar 2019, 17:29

Putting on one side the fundamental aerodynamic issues and the lack of clarity or coverage in the operating manual. There is no getting away from the fact that there is a major flaw in the MCAS system that allows automation to try to crash the aircraft. It is obvious from the FDR trace that is what has happened. It is true that the pilots could have averted the accident had they acted quickly and with sufficient knowledge, but that does not take away that Boeing and the FAA (and perhaps the Lion Air investigators) are culpable for allowing an unsafe aircraft into the air. The AoA sensor/s and the MCAS system is not fail safe and does not provide adequate notification to the pilots. The general guidelines and practice of duplication and redundancy were not followed for the MCAS system.

It is a sad day for the aircraft industry that it is likely to show that politics has apparently superseded the proud tradition of safety always coming first. It is unforgivable and should not be tolerated. For my part, I hope the matter is fully investigated and those that are culpable face the full force of the law.

Lastly, I would like to offer my condolences to those that have lost their lives and the families and friends they have left behind. It is shameful.

gums

14th Mar 2019, 17:38

Salute!

you are wrong, sky9
There are two vanes.

The problem is the MCAS switches from one to the other upon reset. Had Lion crew MCAS been using the good vane all they would have had would have been unreliable something or other warnings and no flight control interference. And no stick shaker for left seat guy.
I am more scared by what Aloha hints. AoA inputs and who knows what other things for the spoiler What other things on the MAX that we do not know, nor the pilots?

Gums sends.....

poldek77

14th Mar 2019, 17:56

I'd love to know what your background and knowledge base is on this. To date my understanding is that MCAS is trim specific in function and adds incremental trim specific to certain criteria. Taken in a vacuum it's difficult to fathom how this by itself could lead to a loss of control by a qualified aviator. Under what possible circumstances would speed brakes be deployed except during landing??? Or are you confusing speed brakes with the leading edge flaps and slats on the 737?

Most probably not in this case but here it is:Elevator Jam Landing Assist
This will give limited changes to the vertical flight path from the spoilers to assist the approach and landing if the normal elevator system jams. The control panel is located on the Aft Overhead Panel, even if it is switched on it will only be active when the flaps are 1 or greater. When in use, the spoilers rise to a preset position; they then extend or retract as the elevator column is pushed or pulled to increase or decrease the rate of descent.

(737 MAX - FBW Spoiler System (http://www.b737.org.uk/max-spoilers.htm#ejla))

flyingchanges

14th Mar 2019, 18:21

Have we ruled out the Max's FBW spoilers?! IMHO the precipitous and unrecoverable descent would be consistent with un-commanded spoiler deployment.

Nope, it barely descends with full boards...

SquintyMagoo

14th Mar 2019, 18:24

cervo77 asks "How should they know that pulling on the Yoke didn’t stop the trim?"

Shouldn't they hear or notice the trim wheel continuing to turn?

Airbubba

14th Mar 2019, 18:28

The NTSB is sending investigators to France to help with the recorders:

NTSB Sends Additional Investigators to Assist in Ethiopian InvestigationWASHINGTON (March 14, 2019) —The U.S. National Transportation Safety Board (http://www.ntsb.gov/)is dispatching three investigators to France Thursday to assist with the downloading and analysis of flight recorders from the Boeing 737 MAX 8 that crashed Sunday near Addis Ababa, Ethiopia.

The NTSB investigators have expertise in recorders, flight crew operations and human factors. The French Bureau d'Enquêtes et d'Analyses (BEA) will be downloading the flight data recorder and cockpit voice recorder in support of the Ethiopian investigation.

The investigation is being led by the Ethiopian Aircraft Accident Investigations Bureau in accordance with the standards defined in International Civil Aviation Organization (https://www.icao.int/) Annex 13. The NTSB appointed an accredited representative to the investigation under the ICAO standards because the airplane was manufactured in the United States. All investigative data regarding the investigation will be released by Ethiopian authorities.

For more information on NTSB participation in foreign investigations go to: https://go.usa.gov/xEswV (https://go.usa.gov/xEswV).

The NTSB investigators dispatched to France will work in coordination with investigators on the ground in Addis Ababa. Those investigators were sent immediately after the accident and have been integral to the efforts underway in Ethiopia. They are being assisted by technical advisers from the Federal Aviation Administration, Boeing and GE/Safran, the manufacturer of the engines.

The NTSB is an independent U.S. federal agency charged with investigating transportation accidents and issuing recommendations to improve safety.

airman1900

14th Mar 2019, 18:50

Precisely, the old Boeing would not need reminding.
Nor would they have lobbied the President to intervene if they were certain the data supported their public rehearsed statements of safety.

The "old Boeing" almost always tries to blame the pilots: USAir Flight 427, September 8, 1994 when Boeing said the pilots stepped on the wrong pedal.
https://www.ntsb.gov/investigations/AccidentReports/Pages/AAR9901.aspx

And sometimes an investigating agency tries to blame the pilots, especially when the aircraft is made in their country, like the French BEA when they blamed the pilots for American Eagle Flight 4184, October 31, 1994.
https://www.ntsb.gov/investigations/AccidentReports/Pages/AAR9601.aspx
https://www.ntsb.gov/investigations/AccidentReports/Pages/AAR9602.aspx

PaxBritannica

14th Mar 2019, 19:15

Boeing 737 Max aircraft grounded 'until May at least' (https://www.bbc.co.uk/news/business-47567039)

MPN11

14th Mar 2019, 19:31

As someone has recently posted on another Forum ..

Having TWO new types grounded in the space of 5-6 years is truly appalling by modern standards.

Something is wrong, deep down in the system either at Boeing or the FAA.

PJ2

14th Mar 2019, 19:41

As someone has recently posted on another Forum ..Something is wrong, deep down in the system either at Boeing or the FAA.

This will take an examination of culture at Boeing, particularly before and after 1997 to see the changes. Diane Vaughan examined NASA after the Challenger accident and issued "The Challenger Launch Decision: High Risk Technology, Culture and Deviance at NASA" in 1997, (revised 2016). The examination led to changes but not before Columbia was lost. I believe there is something similar here. Hopefully there is someone with the capacity, time and energy to do so because the question does at least need asking with regard to both organizations, (FAA & Boeing themselves, and also the relationship between the two).

WHBM

14th Mar 2019, 19:46

As someone has recently posted on another Forum ..

Something is wrong, deep down in the system either at Boeing or the FAA.
You can actually find this increasingly with government Regulatory Authorities, in various countries, and with other regulators/augitors, eg for the finance industry.

Time was when the regulators were quite independent, and looked at things with true external oversight. They would need the knowledgeable personnel to work through everything. Then it slowly occurred to them that they might get the industry they were regulating to do certain of their jobs for them, particularly if this lessened their own costs. Instead of checking everything out from the outside, get the industry to bear the cost and write up a description of what they had done, which could then just be signed off. Increasing the industry did all the work, and the Regulator just said "OK then". Of course, they did not then need as many of their own knowledgeable technical staff now, it becomes just admin staff checking that a box ticking exercise has been completed. If they don't know what boxes to ask to be ticked in the first place, well, just ask the industry to devise the list for you ...

oldoberon

14th Mar 2019, 19:47

PJ2 1396
would be good if they could get the same person to do it on FAA then boeing

WHBM

14th Mar 2019, 19:58

...and their customers are exactly the same
They know the low cost cheap flights risk a monumental mess up every now and then that leaves them stranded for XX hours in some ghastly place
But they also just hope the odds work in their favour and its not them that get caught.
Its the same everywhere: people complaining how some corporate is cutting services or not doing it "properly" while the same complainers are busy bodging up their electrics, roof, guttering whatever and hope the next purchaser does not notice.
The airline "customers" are often not those flying at all, but corporate central beancounter staff making bookings for their staff on what is the cheapest fare to the destination, regardless of other considerations. The staff actually flying end up just stuck with the choice. Certain carriers have made a whole market out of this ...

Some corporates are better at this than others. There is a general belief that oil companies, well used to very substantial Due Diligence of their helicopter operators, let this approach go through to the comercial airline bookings for their staff as well, who to use and who not. Others not so much. It's notable that a significant number of the Ethiopian passengers were travelling for a major worldwide organisation, who possibly procure their air tickets centrally.

Sailvi767

14th Mar 2019, 20:20

cervo77 asks "How should they know that pulling on the Yoke didn’t stop the trim?"

Shouldn't they hear or notice the trim wheel continuing to turn?

Yes.

filler

DaveReidUK

14th Mar 2019, 20:23

Surely BEA are responsible for recovering data not analysing

The BEA are responsible for whatever they have agreed to do on behalf of the ECAA who are leading the investigation.

I would be amazed if their remit did not include initial analysis of the recovered data. After all, that's what the 'A' in BEA stands for.

Joejosh999

14th Mar 2019, 20:23

Is there an airspeed input component to MCAS ?
http://www.b737.org.uk/mcas.htm
this mentions “at airspeed approaching stall”

I wondered because we know there was likely an UAS situation for ET, so potentially a pitot hardware issue.
If AoA was all that MCAS received , then we’d be looking at possible alpha vane failure as well, therefore we’d have hardware issues with two separate components.

So - could a blocked pitot be another single point of failure? And the AoA was fine?....

Ian W

14th Mar 2019, 20:32

Ian I assume you read all of the narratives.

A few quick points from memory
Pilots not being able to usual scan and see what they are looking for
Pilots not familiar with new displays
Pilots not Knowing what the "Maint" msg means and unable to find it in pilots notes
Pilots not knowing what a particular switch labelled SEL was for.

That is abysmal conversion training (classroom and sim) , abysmal documentation and DANGEROUS

If those points are correct then how were they even flying the aircraft? :ugh: The airline involved is responsible for ensuring conversion to type and should ensure that the crews are trained and tested. If the Boeing difference and conversion is insufficient then Boeing needs to be told. Then surely simple self preservation if you are put into a new cockpit and cannot 'scan and see what you are looking for' not find switches read displays or know what switches are for.... I would expect that crew to not fly the aircraft. That they did indicates something very very wrong at the airline involved. It seems we are starting to see the impact of the beancounters on flight safety and/or perhaps - if you are right either a gung-ho approach from some crews or an unwillingness to stand above the parapet and say I need more training for this one.

More to the point in both cases the aircraft were in good VFR at low level, speed should be apparent without looking inside so there is a visual cross check, the trim keeps going nose down - so switch off stab trim (AFAIK the switches are in the same place in all 73's) start using the trim wheel and fly manually and visually while PM goes through the various memory items and checklists. We know that this approach works as a Lion Air flight before the crash flight did just that and continued as a normal flight.

FCeng84

14th Mar 2019, 20:52

Is there an airspeed input component to MCAS ?
737 MAX - MCAS (http://www.b737.org.uk/mcas.htm)
this mentions “at airspeed approaching stall”

I wondered because we know there was likely an UAS situation for ET, so potentially a pitot hardware issue.
If AoA was all that MCAS received , then we’d be looking at possible alpha vane failure as well, therefore we’d have hardware issues with two separate components.

So - could a blocked pitot be another single point of failure? And the AoA was fine?....

MCAS activation requires AOA above an activation level that is a function of Mach number. The dependence on Mach is not particularly significant (i.e., errant Mach would not significantly impact the MCAS activation point). The amount of stabilizer motion that MCAS will command is also a function of Mach number. With Mach less than 0.4 MCAS will move the stabilizer as much as 2.5 degrees if AOA exceeds the activation threshold by many degrees. At cruise Mach number the size of the MCAS stabilizer motion increment is less than 1/3rd that at low Mach numbers. The bottom line with regard to the question posed here is that a blocked pitot coupled with healthy AOA data would not cause MCAS to activate unless actual (and thus properly sensed) AOA increased to a level significantly above that for normal operation. If you follow pitch/power guidelines after pitot blockage and detection of unreliable airspeed you will not get MCAS. If you get slow and get to elevated AOA following pitot blockage you are likely to encounter MCAS provide flaps are up and autopilot is not engaged.

Joejosh999

14th Mar 2019, 20:55

MCAS activation requires AOA above an activation level that is a function of Mach number. The dependence on Mach is not particularly significant (i.e., errant Mach would not significantly impact the MCAS activation point). The amount of stabilizer motion that MCAS will command is also a function of Mach number. With Mach less than 0.4 MCAS will move the stabilizer as much as 2.5 degrees if AOA exceeds the activation threshold by many degrees. At cruise Mach number the size of the MCAS stabilizer motion increment is less than 1/3rd that at low Mach numbers. The bottom line with regard to the question posed here is that a blocked pitot coupled with healthy AOA data would not cause MCAS to activate unless actual (and thus properly sensed) AOA increased to a level significantly above that for normal operation. If you follow pitch/power guidelines after pitot blockage and detection of unreliable airspeed you will not get MCAS. If you get slow and get to elevated AOA following pitot blockage you are likely to encounter MCAS provide flaps are up and autopilot is not engaged.

Thanks for the clarification!

So it’s possible we’ve had hardware failure in two separate components? Pitot and alpha vane?

El Bunto

14th Mar 2019, 21:04

Just looking at the Boeing 777-9 rollout photos. My question is, Have Boeing done a similar thing with the engine position on the 777-9 as they did with the 737-MAX? Forward and high.

They have actually lengthened the main gear legs to 16ft, the longest ever used on an airliner, but yes the diameter of the engine means that it does sit higher and farther forward.

Of course with the FBW 777 that should be less of a problem.

Trivium: the manufacturer of the 777X MLG, Héroux Devtek in Quebec, also supplied the legs for the Apollo Lunar Module.

Peristatos

14th Mar 2019, 21:09

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/800x988/902c9134_e796_4182_9cd5_ae496dedf62b_35788cbeb4be98e84794e50 67ed81c899dacc2f5.jpeg
Source: https://www.bloomberg.com/news/articles/2019-03-13/doomed-737-caught-on-satellite-data-that-could-aid-investigation

Lonewolf_50

14th Mar 2019, 21:33

After all, that's what the 'A' in BEA stands for. After reading through all 12 of the AF 447 threads, I came away with the impression that some people felt that the A in BEA stood for Airbus. :E

For PJ2: I have an idea that there are some corporate cultures that might need to awaken to training being viewed as a necessity, rather than as an expense, or a cost center. Which corporate (or even national) entities that message needs be to be digested in I'll leave as an exercise for the reader.

For someone further up the page: off to take a look at the LionAir FDR trace, thanks for the tip.

For anyone, last question.
MTBF of AoA probes. Who is Boeing's supplier? (If the AoA prob, or its signal to the FCC, doesn't go whacky do we ever hear about any of this?)
We had a fairly long discussion about pitot tubes after AF447 went down, and commentary about Goodrich probes that AB was working on putting on their fleet versus a Thales one. Are AoA probes held to the 1 x 10^-7th hours failure criteria, or a 1 x 10 ^-9?
I don't know how good the final report on LionAir will be, but I am very interested in the prelude to that accident, in terms of what maintenance actions were and weren't taken, and how the trouble shooting logic went, and the various repairs.

Photonic

14th Mar 2019, 21:51

For anyone, last question.
MTBF of AoA probes. Who is Boeing's supplier? (If the AoA prob, or its signal to the FCC, doesn't go whacky do we ever hear about any of this?)
We had a fairly long discussion about pitot tubes after AF447 went down, and commentary about Goodrich probes that AB was working on putting on their fleet versus a Thales one. Are AoA probes held to the 1 x 10^-7th hours failure criteria, or a 1 x 10 ^-9?

I don't have that info, but as a general comment on sensor reliability, up-thread somewhere there is a post by a NG pilot mentioning that a bird strike took out an AoA vane on one of his recent flights. Obviously the sensor should have the highest possible MTBF, but the system as a whole needs a safe method to recover from a sensor that can be taken out that easily, and that randomly.

a_q

14th Mar 2019, 21:53

Quote:Originally Posted by cervo77
Then there are differences, and the Pilots should have been informed about the differences. Unfortunately the lion and Ethiopian's pilots have not had this chance

Apparently the Ethopian pilots did, according to CNN:
Quote:GebreMariam said the Ethiopian Airlines pilots had received additional training on the flight procedures involving the 737 MAX 8 after the Lion Air crash.

Apologies with the mess of the quoting above but the site doesn't help you multi-quote....

Channel 4 News (UK) has just screened an interview with a "Senior Ethiopian Pilot".

Note that: the interview was voice disguised and anonymous. The pilot did not state that then flew 737 MAX-8, or if they did, what experience they had on that airframe.

In the interview the pilot stated that the MCAS had not been taught to them [by Boeing]. He went on to talk about not being able to defeat the system by pulling on the stick. He did NOT mention adjusting trim [as a means to defeat the system].

Having read from the professionals above about having to use trim wheels or cutout switches to defeat MCAS, and NOT using the stick alone, my conclusion from the interview was that the pilot had NOT been trained in the correct procedures, or surely he would have mentioned it?

Of course it might be that C4 found a pilot that hadn't flown the MAX 8, but the C4 journalists are usually pretty professional and wouldn't put this interview forward if that were the case.

Lonewolf_50

14th Mar 2019, 21:57

I don't have that info, but as a general comment on sensor reliability, up-thread somewhere there is a post by a NG pilot mentioning that a bird strike took out an AoA vane on one of his recent flights. Obviously the sensor should have the highest possible MTBF, but the system as a whole needs a safe method to recover from a sensor that can be taken out that easily, and that randomly. 100% concur on system robustness requirement.

FlightlessParrot

14th Mar 2019, 22:00

You can actually find this increasingly with government Regulatory Authorities, in various countries, and with other regulators/augitors, eg for the finance industry.

Time was when the regulators were quite independent, and looked at things with true external oversight. They would need the knowledgeable personnel to work through everything. Then it slowly occurred to them that they might get the industry they were regulating to do certain of their jobs for them....<SNIP>

Yes, except that this was not something that "slowly occurred" to the regulators: it was a deliberate political decision for "light-handed regulation" and self-regulation, taken throughout Anglophonia, in the belief that the market would ensure that the regulated entities would want to keep their good reputation (for commercial reasons), and so could attend to the material aspects of regulation, without being stifled by "bureaucratic inertia." We now see the costs, in many industries, in lives that would not have been lost under the old regime.

silverstrata

14th Mar 2019, 22:08

.(Two graphs of vertical speed).

Source: https://www.bloomberg.com/news/articles/2019-03-13/doomed-737-caught-on-satellite-data-that-could-aid-investigation

Interesting two graphs.
And of course the 21 second interval in vertical speed cycles, equates very nicely with 10 secs of MCAS trim input and 10 sects of manual trim resetting. Prima face evidence that MCAS was operating in this flight.

Silver

Nieuport28

14th Mar 2019, 22:22

777 was the last program I worked on at Boeing where I felt they did everything pretty much as it should be done. "Working Together" was the motto and that meant not just consulting with customers, but coordinating internally by having 'design/buil'' teams working with each other all the way rather than emerging from their individual tunnels at the end of the process to find miscommunications and things that didn't work together properly. After that program, Boeing dismantled their traditional design matrix organizations which served as checks and balances on each other, but required lots of staff. Later programs seemed to have lost that magic and each follow-on project was mandated to have a faster and cheaper design/build/test/certify cycle than the previous one. Most of the low hanging wasteful effort was eliminated long ago and it was value added activities that started being cut. I felt that trend culminated on the Max program which kicked off with a misguided dream by program leadership that they might actually be able to eliminate flight testing altogether because prediction methods and computational models were so accurate and mature. Pure hubris. Every program I ever worked on had unanticipated show stoppers which surfaced during flight testing and required panic fixes, yet that basic lesson seemed to have to be constantly relearned.

IMO, the day Alan Mulally left Boeing was the beginning of the end of "Working Together." I'm not surprised at Boeing's current situation. Look at the KC-46's being delivered with trash, and tools left in them. It's like WTF is going on? Seems like a dire situation IMO.

Loose rivets

14th Mar 2019, 22:24

krismiler

14th Mar 2019, 22:24

The MCAS is there to stop the aircraft from stalling so why not call it a "stall avoidance system" ? If it walks like a duck and quacks like a duck, then it's a duck.

The B757 and B767 first flew 15 years after the B737 and are already out of production except for freighter and military versions of the B767.

The move from the B742 to B744 required an extensive redesign of the flight deck and systems, Boeing didn't just stick in a couple of TV screens in front of the pilots. The B737 should have had a similar in-depth redesign if they were going to continue with the same airframe, rather than the patchwork quilt of modifications and work arounds it ended up with.

It's a first generation jet modified into a third generation one.

FCeng84

14th Mar 2019, 22:35

Interesting two graphs.
And of course the 21 second interval in vertical speed cycles, equates very nicely with 10 secs of MCAS trim input and 10 sects of manual trim resetting. Prima face evidence that MCAS was operating in this flight.

Silver

We must be careful trying to read too much into very limited data. Remember that MCAS will not come active a second time until the pilot as been off of the trim input for 5 continuous seconds. For the Lion Air event data showing pilot and MCAS trim commands has been presented in that PPRUNE thread. It would be interesting to line that up with these plots to see how that particular cycle corresponded to pilot trim inputs. Hopefully we have access to the ET data soon to do the same for that event.

thcrozier

14th Mar 2019, 22:37

Anyone know if Boeing has been able to duplicate the problem in flight testing?

GarageYears

14th Mar 2019, 22:43

Lion Air was deluged with heavy raid the night before the tragedy. Yes, I'm still looking for multiple glitches, that when combined cause chaos.

Those graphs seem too similar not to be very closely connected, but the similarity might be partly caused by human interpretation and resultant handling and not entirely by glitch sequences.

Unfortunately, I fear, unless you plot fifty other 737 departure vertical speed graphs, you cannot meaningfully tell anything from these. All flights may exhibit such a 20 second period. You are seeing what you hoped to see - something apparently similar. But you have no meaningful references.

-GY

FCeng84

14th Mar 2019, 22:54

Anyone know if Boeing has been able to duplicate the problem in flight testing?

Need to be specific about what you mean by "duplicate the problem".

Volume

14th Mar 2019, 23:29

Trimming the plane for neutral stick force is part of safely trying to get back to the ground. This is a fundamental airplane flying concept since the 172 presolo days. Literally lesson one.
A lot of "progress" happened since the 172... Modern Pilots rely a lot on Autotrim, all Airbus FBW aircraft can be flown completely ignoring the trim. Maybe this even is a good idea, as it makes the life easier for the pilot and eliminates sources for error. Until some systems fail, and all of a sudden the pilot has to deal with another very powerful flight control element (actually much more powerful than the elevator for most aircraft) he completely had forgotten about...
To decouple pilot controls from aircraft control surfaces may after all not be a very clever idea.

After reading through all 12 of the AF 447 threads, I came away with the impression that some people felt that the A in BEA stood for Airbus.
Probably those people have not read all 420 pages (including the appendices). There are some subtle but very clear points which BEA addresses, that could be understood as Airbus design deficiencies. For example the missing speed stability of the airbus FBW logic or the stall warning inhibit function.

Most probably the Boeing MCAS will also be mentioned as "not so clever idea" in the final reports, without identifying it as cause or contributing factor... So those reading only that part of the report will probably claim that the B in NTSB stands for Beoeing...

Need to be specific about what you mean by "duplicate the problem".
Boeing test pilots will never be able to duplicate the problem, that the pilots do not 100% understand the MCAS logic, and are taken by surprise.
If you know what will hapen and why it happens, if you are prepared, it is a totally different scenarion.

Airbubba

14th Mar 2019, 23:48

From The New York Times:

Boeing 737 Max Hit Trouble Right Away, Pilot’s Tense Radio Messages ShowBy Selam Gebrekidan (https://www.nytimes.com/by/selam-gebrekidan) and James Glanz (https://www.nytimes.com/by/james-glanz)

March 14, 2019
ADDIS ABABA, Ethiopia — The captain of a doomed Ethiopian Airlines jetliner faced an emergency almost immediately after takeoff from Addis Ababa, requesting permission in a panicky voice to return after three minutes as the aircraft accelerated to abnormal speed, a person who reviewed air traffic communications said Thursday.

“Break break, request back to home,” the captain told air traffic controllers as they scrambled to divert two other flights approaching the airport. “Request vector for landing.”

Controllers also observed that the aircraft, a new Boeing 737 Max 8, was oscillating up and down by hundreds of feet — a sign that something was extraordinarily wrong.

All contact between air controllers and the aircraft, Ethiopian Airlines Flight 302 to Nairobi, was lost five minutes after it took off on Sunday, the person said.

The person who shared the information, speaking on the condition of anonymity because the communications have not been publicly released, said the controllers had concluded even before the captain’s message that he had an emergency.

The account of the cockpit communications shed chilling new detail about the final minutes before the plane crashed, killing all 157 people aboard. The crash, which has led to a worldwide grounding of Max 8s, was the second for the best-selling Boeing aircraft in less than five months.

Regulatory authorities in the United States and Canada say similar patterns in the trajectories of both planes may point to a common cause for the two crashes. But they cautioned that no explanation had been ruled out yet, and said the planes might have crashed for different reasons.

The new disclosures about the last moments of Flight 302 came as pilots were discussing what they described as the dangerously high speed of the aircraft after it took off from Addis Ababa’s Bole International Airport.

Pilots were abuzz over publicly available radar data that showed the aircraft had accelerated far beyond what is considered standard practice, for reasons that remain unclear.

“The thing that is most abnormal is the speed,” said John Cox, an aviation safety consultant and former 737 pilot.

“The speed is very high,” said Mr. Cox, a former executive air safety chairman of the Air Line Pilots Association in the United States. “The question is why. The plane accelerates far faster than it should.”

Ethiopian Airlines officials have said the crew of Flight 302 reported “flight control” problems to air traffic controllers a few minutes before contact was lost. The new account of communications between air traffic controllers and the pilot, Yared Getachew (https://www.nytimes.com/2019/03/12/business/ethiopian-airline-crash-school.html?module=inline), who had 8,000 hours of flying experience, provides much more information about what was happening in the cockpit.

Within one minute of Flight 302’s departure, the person who reviewed communications said, Captain Getachew reported a “flight control” problem in a calm voice. At that point, radar showed the aircraft’s altitude as being well below what is known as the minimum safe height from the ground during a climb.

Within two minutes, the person said, the plane had climbed to a safer altitude, and the pilot said he wanted to stay on a straight course to 14,000 feet.

Then the controllers observed the plane going up and down by hundreds of feet, and it appeared to be moving unusually fast, the person said. The controllers, the person said, “started wondering out loud what the flight was doing.”

Two other Ethiopian flights, 613 and 629, were approaching from the east, and the controllers, sensing an emergency on Flight 302, ordered them to remain at higher altitudes. It was during that exchange with the other planes, the person said, that Captain Getachew, with panic in his voice, interrupted with his request to turn back.

Flight 302 was just three minutes into its flight, the person said, and appeared to have accelerated to even higher speeds, well beyond its safety limits.

Cleared by the controllers to turn back, Flight 302 turned right as it climbed further. A minute later, it disappeared from the radar over a restricted military zone.

The disaster drew immediate comparisons to the October crash of another Boeing 737 Max 8, operated by Lion Air, in Indonesia. Both took place soon after (https://www.nytimes.com/2019/03/11/business/ethiopian-airline-crash.html?module=inline) takeoff, and the crews of both planes had sought to return to the airport.

The possibility that the two crashes had a similar cause was central to regulators’ decision to ground all 737 Maxes, a family of planes that entered passenger service less than two years ago.

After the Indonesia crash, a new flight-control system meant to keep the jet from stalling was suspected as a cause. In both cases, pilots struggled to control their aircraft.

The investigation of the Ethiopian crash is still in its early stages, and safety regulators have noted that it is too soon to draw conclusions about the cause. The so-called black boxes (https://www.nytimes.com/2019/03/11/world/boeing-737-max-air-crash-ethiopia.html?module=inline), voice and flight data recorders that contain more detailed information about the Ethiopian flight’s final moments, arrived in France on Thursday for analysis.

Since the Indonesia crash, Boeing has been working on a software update for the 737 Max jets, expected by April. But the company and the Federal Aviation Administration face new questions over whether there should have been more pilot training as airlines added the new models to their fleets.

On Wednesday, the chairman of the transportation committee in the House of Representatives said he would investigate the F.A.A.’s certification of the 737 Max, including why the regulator did not require more extensive training.

GarageYears

15th Mar 2019, 00:07

Quote:Originally Posted by cervo77
Then there are differences, and the Pilots should have been informed about the differences. Unfortunately the lion and Ethiopian's pilots have not had this chance

Quote:GebreMariam said the Ethiopian Airlines pilots had received additional training on the flight procedures involving the 737 MAX 8 after the Lion Air crash.

Apologies with the mess of the quoting above but the site doesn't help you multi-quote....

Channel 4 News (UK) has just screened an interview with a "Senior Ethiopian Pilot".

Note that: the interview was voice disguised and anonymous. The pilot did not state that then flew 737 MAX-8, or if they did, what experience they had on that airframe.

In the interview the pilot stated that the MCAS had not been taught to them [by Boeing]. He went on to talk about not being able to defeat the system by pulling on the stick. He did NOT mention adjusting trim [as a means to defeat the system].

Having read from the professionals above about having to use trim wheels or cutout switches to defeat MCAS, and NOT using the stick alone, my conclusion from the interview was that the pilot had NOT been trained in the correct procedures, or surely he would have mentioned it?

Of course it might be that C4 found a pilot that hadn't flown the MAX 8, but the C4 journalists are usually pretty professional and wouldn't put this interview forward if that were the case.

So that puts the ball in the court of Ethiopian - I assume that’s your point? Because that’s my take.

- GY

GarageYears

15th Mar 2019, 00:15

Within one minute of Flight 302’s departure, the person who reviewed communications said, Captain Getachew reported a “flight control” problem in a calm voice. At that point, radar showed the aircraft’s altitude as being well below what is known as the minimum safe height from the ground during a climb.

We know MCAS is not operational below 1000ft and with flaps extended, so how does the report above square with this being MCAS related? It appears the root issue was evident as a flight control problem more or less from the point the aircraft took off.

Something doesn’t seem to add up here.

- GY

JamesT73J

15th Mar 2019, 00:50

That is interesting. Maybe a CoG problem, or misconfigured T/O trim?

Or if they had an AOA sensor fault they get a stick shaker straight away, crew are startled and arrest pitch up, a/c rapidly accelerates and flies to trim, thus creating a little porpoising. Maybe they then clean it up and MCAS finishes them off.

No idea. Very keen to see the data as and when.

GarageYears

15th Mar 2019, 01:10

CONSO

15th Mar 2019, 01:10

IMO, the day Alan Mulally left Boeing was the beginning of the end of "Working Together." I'm not surprised at Boeing's current situation. Look at the KC-46's being delivered with trash, and tools left in them. It's like WTF is going on? Seems like a dire situation IMO.

I'll second that- years ago and even after I retired after /when working on 777 I had excellent communications with Alan - I'm probably only one of maybe 200 people who have personally been hugged by Alan after sending him an email on a weekend about a close friend known to Alan who was in the Hospital . Alan answered within an hour. My friend later passed and Alan attended his funeral. he always responded to direct emails and made sure that an answer was forthcoming. But that ran counter to the MDC gang in power. And as you infer- the rest is history !

CONSO

15th Mar 2019, 01:14

Anyone know if the AOA sensors on the MAX are any different from the NG? If not, are their reliability issues with the NG AOA sensors?

Otherwise, what chance is there for another AOA sensor triggering a MCAS event just now, when there are thousands of NGs making daily flights with no issues?

It just doesn’t seem to make sense unless this is a new/different AOA sensor design, with a design flaw.

- GY

its not the sensor - its the fubar software and dependance on a single sensor which gets switched from side to side dependant on aircraft power cycles, but which can without any comparison or error checking drive a horizontal stabilizer !

wrench1

15th Mar 2019, 01:22

That is interesting. Maybe a CoG problem, or misconfigured T/O trim?
Interesting choice of words. One item from the FAA grounding order that is missing from most conversations:"On March 13, 2019, the investigation of the ET302 crash developed new information from the wreckage concerning the aircraft 's configuration just after takeoff that,..."

gums

15th Mar 2019, 01:29

GarageYears

15th Mar 2019, 01:32

its not the sensor - its the fubar software and dependance on a single sensor which gets switched from side to side dependant on aircraft power cycles, but which can without any comparison or error checking drive a horizontal stabilizer !

But the fubar software only does something if the AOA sensor is broken. My point is rather obvious. If there are thousands of the SAME sensors working perfectly, day in, day out, on NGs all over the world, it’s very unlikely that two suddenly go wrong within a few months.

Either it’s a different sensor, new with the MAX, or this could one of the universes rarest conincidences. Or the crash is unrelated.

- GY

GarageYears

15th Mar 2019, 01:39

Salute!

Sorry, Garage, but MCAS doesn't care about altitude. With flaps up and AoA at a certain value or above and not in A/P it will activate unless we have been misinformed for 5 months. Not sure about main gear being up, but there has been a mention of "configuration" shortly after takeoff.
Gums sends...

I rarely disagree with the smart folk, but there is DEFINITELY an altitude limit on MCAS engagement.

Pretty sure it is 1000 ft AGL, but I’m trying to find a definitive reference.

Respectfully, GY

Coborn C6

15th Mar 2019, 01:44

I've been a long time in read-only mode, felt it was time to contribute.:)

Interesting two graphs.
And of course the 21 second interval in vertical speed cycles, equates very nicely with 10 secs of MCAS trim input and 10 sects of manual trim resetting. Prima face evidence that MCAS was operating in this flight.
Silver
If I've read the second graph correctly, the 21 seconds is measured from 05:39:11Z to 05:39:32Z (per the FR24 data) - corresponding to 225 feet and 600 feet aal.

That seems rather low for the flaps to be fully retracted, for MCAS to kick in, and for 10 secs of manual trim to be completed.

It appears from the same data that ET302 had only just left the runway at 05:38:59Z or a few seconds earlier. From what we know about the system, is it really feasible that MCAS starts operating 12 seconds later?

Apologies if I've misunderstood something.

CONSO

15th Mar 2019, 01:51

But the fubar software only does something if the AOA sensor is broken. My point is rather obvious. If there are thousands of the SAME sensors working perfectly, day in, day out, on NGs all over the world, it’s very unlikely that two suddenly go wrong within a few months.

Either it’s a different sensor, new with the MAX, or this could one of the universes rarest conincidences. Or the crash is unrelated.

- GY

Bird strike or ramp rash or software error are three most obvious- the point is to alllow a SINGLE sensor to directly override pilot input and not be documented that it even exists is as close to criminal as one can imagine. MTBF makes no diff- And BA knows how to make a comparison for example 787

http://www.ata-divisions.org/S_TD/pd...ngtheB-787.pdf

see pages 40-41 (http://www.ata-divisions.org/S_TD/pdf/other/IntroducingtheB-787.pdf)

EternalNY1

15th Mar 2019, 01:58

That is interesting. Maybe a CoG problem, or misconfigured T/O trim?

What about the mentions of speed being far too high, even while they were climbing to a safer altitude?

That isn't a CoG or trim issue ... ??

boeingboy737

15th Mar 2019, 02:01

EDML

15th Mar 2019, 02:38

If there are any mx tech on here can you tell us if the Stab trim cut out switches are connected to the MCAS system ie will the switches in the cut out position actually stop the MCAS from trimming thanks

The manual ones next to the trim wheel are. The ones at the column sensing a pull against the trim obviously aren‘t because the MCAS has to trim against a strong pull to maintain the desired positive stick force gradient.

gums

15th Mar 2019, 02:40

@ Boeing boy

Our resident engineer , FCeng84, and the wiring diagrams show that the switches cut off the electric trim motor. Trim wheel still works.
"bumping the trim switches on the yoke stops MCAS. then it starts again after 5 seconds if the AoA is still high. You can clearl;y see this on the 610 accident flight data and preceding flight.
So no dedicated MCAS power switches. It's all in the FCC boxes, thence wires to the trim motor.

Gums...

P.S. still can't find an altitude restriction or enabling condition.

tarkay01

15th Mar 2019, 02:44

I rarely disagree with the smart folk, but there is DEFINITELY an altitude limit on MCAS engagement.

Pretty sure it is 1000 ft AGL, but I’m trying to find a definitive reference.

Respectfully, GY

i belive Lion Air was at 5000 feet when they had their issues. Doesn’t make any sense to altitude limit the system as it would need access to digital terrain model to make decisions.

ImbracableCrunk

15th Mar 2019, 02:46

Most probably not in this case but here it is:Elevator Jam Landing Assist
This will give limited changes to the vertical flight path from the spoilers to assist the approach and landing if the normal elevator system jams. The control panel is located on the Aft Overhead Panel, even if it is switched on it will only be active when the flaps are 1 or greater. When in use, the spoilers rise to a preset position; they then extend or retract as the elevator column is pushed or pulled to increase or decrease the rate of descent.

(737 MAX - FBW Spoiler System (http://www.b737.org.uk/max-spoilers.htm#ejla))

Wild. The MAX has Direct Lift Control like the L-1011? To bad that's not used under normal circumstances.

1_of_600

15th Mar 2019, 02:52

With regard to the many posts referencing the practice of various maneuvers and events during simulator training sessions:

Have a look at and thought about what is in those simulators.

Specifically, there was a fundamental shift over the last several years about where the software for the simulators comes from, and most specifically for the 787, 737 MAX and most recently the 777-X. One of the biggest differences between the current approach and the "classical" methods concerns the content of available malfunctions and fault scenarios to be trained. There was a very deliberate choice made to limit that content to only those events that are part of the QRH.

Since MCAS was never "advertised" to the flight crews, it almost certainly was not included in the list of "training events" for the MAX simulators. I *might* be wrong, but not based on the content I saw at several of the "working group" events up through about 2 years back.

Bear in mind that there is a huge difference between an engineering simulation and a crew training simulation. The latter type, especially for the MAX and other recent products, contains only what the provider decided that it should contain.

Take a guess as to who that provider is.

CONSO

15th Mar 2019, 03:22

[QUOTE=gums;10419051]@ Boeing boy

Our resident engineer , FCeng84, and the wiring diagrams show that the switches cut off the electric trim motor. Trim wheel still works.
"bumping the trim switches on the yoke stops MCAS. then it starts again after 5 seconds if the AoA is still high. You can clearl;y see this on the 610 accident flight data and preceding flight.
So no dedicated MCAS power switches. It's all in the FCC boxes, thence wires to the trim motor.

Gums...

P.S. still can't find an altitude restriction or enabling condition.[/QUOTE

This may help post 496 11 march 2019 ethopian airliner down thread (cannnot seem to post link )

Mar 2019, 21:55
permalink (https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa-25.html#post10414294)) #496 (permalink) (http://#496 (permalink))

11th Mar 2019, 21:55

jimtx

15th Mar 2019, 03:23

Mad (Flt) Scientist

15th Mar 2019, 03:38

Something isn't quite making sense here....

IF that supposed ATC info is correct - that there seemed to be a sustained and abnormal acceleration - and this DOES seem to be borne out by the FR24 data, which seems to show increasing speed and increasing altitude then the aircraft flight path is NOT the same as Lion Air. Whatever various press releases seem to be claiming.

The Lion Air FDR data appears to show an aircraft exchanging kinetic and potential energy as it dives and accelerates, then climbs and slows , as it either is "MCASed" nose down or pulled back nose up alternately. The final DIVE is where the speed finally builds to by far the highest speed in the whole accident sequence.

ET doesn't do that. The FR24 data (unless there's something newer floating around) shows ground speed continuously increasing (albeit not at a constant rate) while the overall altitude trend is to climb - albeit with some instability. In other words, the ET aircraft seems to be gaining significant energy throughout the flight. No stab system malfunction can add total energy to the aircraft.

Dare I suggest something totally unrelated to MCAS, even though everyone has already jumped on that bandwagon (and grounded the aircraft). What about an uncontrolled high thrust event? Too much thrust, inability to reduce power from TO, something like that.

CONSO

15th Mar 2019, 03:45

What about an uncontrolled high thrust event? Too much thrust, inability to reduce power from TO, something like that.

if you find the link to the nasa anon reporting system for pilots, etc that apply to 737max- you will find one descriptioon of an uncommaned throttle change which I recall was the opposite ( throttle cut ) but my memory may be incorrect . .

EDML

15th Mar 2019, 04:04

jimtx

15th Mar 2019, 04:17

Given boeingboy737 has been here since 1999 and has 20 times the number of posts you do that's a funny call.

i said draw your own conclusions. But with 737 in the screen name I’m happy that he’s not flying a Max, with or without the training that goes with it. Of course other than Brazil, there would have been no training. And I wonder what the Brazilian certifying authority allowed as training since they grounded their fleet anyway.

MickG0105

15th Mar 2019, 04:21

if you find the link to the nasa anon reporting system for pilots, etc that apply to 737max- you will find one descriptioon of an uncommaned throttle change which I recall was the opposite ( throttle cut ) but my memory may be incorrect . .

Correct, the AT failed to maintain thrust. It's recorded in ASRS as ACN: 1590012. Here's the narrative:

After 1000 feet I noticed a decrease in aircraft performance. I picked up that the autothrottles were not moving to commanded position even though they were engaged. I'm sure they were set properly for takeoff but not sure when the discrepancy took place. My scan wasn't as well developed since I've only flown the MAX once before. I manually positioned the thrust levers ASAP. This resolved the threat, we were able to increase speed to clean up and continue the climb to 3000 feet.

Shortly afterwards I heard about the (other carrier) accident and am wondering if any other crews have experienced similar incidents with the autothrottle system on the MAX? Or I may have made a possible flying mistake which is more likely. The FO (First Officer) was still on his first month and was not able to identify whether it was the aircraft or me that was in error.

Mad (Flt) Scientist

15th Mar 2019, 04:26

Either they where to busy controlling the A/C and did not reduce thrust or they hoped the nose up momentum caused by engine thrust would help them to overcome a nose down trim or whatever caused the dive.
The normal reaction to too much thrust would be to simply continue the climb. That would buy some time to sort out whatever happened.

What if they were so concerned about MCAS that they were taking THOSE actions even though it wasn't an MCAS issue? And not addressing the thrust?

Ive seen previous cases where crews were so focused on the 'threat of the week' that they reacted to other symptoms as if they wree the expected, high profile, event.

Capt Kremin

15th Mar 2019, 04:41

CONSO

15th Mar 2019, 05:19

CONSO

15th Mar 2019, 05:26

and some more data

https://www.theatlantic.com/notes/2019/03/heres-what-was-on-the-record-about-problems-with-the-737-max/584791/

https://asrs.arc.nasa.gov/overview/database.html

CurtainTwitcher

15th Mar 2019, 05:39

Did the aircraft even make it to FMC thrust reduction altitude? Capt Kremin's scenario of a flapless takeoff, MCAS activation at liftoff and takeoff thrust for almost the entire duration of the flight could provide a plausible explanation for the continuous increase in speed during the sequence from the known data.

Capt Kremin

15th Mar 2019, 05:43

I have no quibble about the MCAS being involved somehow; but while we know why Lion Air had its activation of the MCAS, we don't know why ETH 302 did. This may be a reason. The aircraft took over 3 minutes to get above 500' AGL This points to very early activation of the MCAS, which needs the flaps to be up to work.

AndyJS

15th Mar 2019, 05:43

Apologies if already posted.

https://twitter.com/Reuters/status/1106423702776881153

bud leon

15th Mar 2019, 06:09

well here is a comparison plot just found in seattle times

Just one thing to note in that comparison graphic is that the altitude axis scale for the Ethiopian flight is 2,000 feet, but the altitude axis scale for the Lion Air axis is 5,000 feet.

krismiler

15th Mar 2019, 07:28

If the MCAS is triggered by one sensor, than simply adding another won't be enough. There needs to be three just like having a standby A/H as a tie breaker.

Surely any mandated modification will require more than a simple software update.

Concorde was grounded for a lengthy period after a design flaw led to a disaster. Extensive modifications were required to the wing tanks before the aircraft was deemed safe. Any solution proposed by Boeing will need to be very conclusive in restoring safety for it to be accepted and it won't be quick or cheap.

N600JJ

15th Mar 2019, 07:32

Any solution proposed by Boeing will need to be very conclusive in restoring safety for it to be accepted and it won't be quick or cheap.

And this time EASA may well not rely on the FAA for lifting ban or even worse re-certification if required...

DaveReidUK

15th Mar 2019, 07:37

Either it’s a different sensor, new with the MAX

Discussed in the Lion Air thread. It's the same part number on the NG and Max. I'd have been surprised if it wasn't.

And BA knows how to make a comparison for example 787

In fact Boeing knows how to make a comparison on the Max (and NG) too - if you pay the extra $$$ when you buy your 737, Boeing will add a few more lines of code to your Air Data System software that enables the "AOA DISAGREE" warning functionality. Both SWA and AAL have that on their aircraft.

WHBM

15th Mar 2019, 07:52

In fact Boeing knows how to make a comparison on the Max (and NG) too - if you pay the extra $$$ when you buy your 737, Boeing will add a few more lines of code to your Air Data System software that enables the "AOA DISAGREE" warning functionality. Both SWA and AAL have that on their aircraft.
If that is the case then there is likely only one version of the code (eases management of it), but a flag set Yes or No if the fee has been paid or not.

If so, and the right code to avoid the issue was actually installed in the aircraft but deliberately switched off, lawyers for the pax, especially those from the second accident, will have a field day.

DaveReidUK

15th Mar 2019, 07:58

DaveReidUK

15th Mar 2019, 08:02

well here is a comparison plot just found in seattle times

It's probably worth pointing out that the altitude anomaly shown at 08:40:51 on the ET plot is spurious.

Mike Flynn

15th Mar 2019, 08:03

This from Reuters. (It appears the lawyers want the claims heard outside the USA)

The crash of Boeing Co's 737 MAX 8 passenger jet in Ethiopia raises the chances that families of the 157 victims, even non-U.S. residents, will be able to sue in U.S. courts, where payouts are larger than in other countries, some legal experts said.

Sunday's crash occurred five months after the same model of the plane went down in Indonesia, an accident that prompted a string of U.S. lawsuits against Boeing by families of the 189 victims.

The company, which has its corporate headquarters in Chicago, has often convinced U.S. judges to dismiss air crash cases in favor of litigation in the country where the evidence and witnesses are, usually where the crash occurred.

That allows the company to avoid U.S. juries, which can award hefty punitive damages to accident victims for wrongful death, emotional suffering and economic hardships of surviving family.

Boeing may have a tougher time with that strategy after the Ethiopian crash, some legal experts said.

This is partly because eight U.S. citizens died and because plaintiffs could argue that liability hinges on system design and safety decisions made by Boeing executives since the Lion Air crash in Indonesia.

"Now with two crashes with a brand-new aircraft, what Boeing did in the intervening five months is more relevant, and that all happened in the United States," said Daniel Rose, a lawyer with Kreindler & Kreindler, a firm that represents air crash victims and their relatives.
Plaintiffs will also claim Boeing failed to exercise reasonable care in designing planes or failed to inform flight crews about how the planes operate, Wolk said.

Rose, the lawyer for passengers, said two accidents so close together will put the focus of any lawsuits on the Ethiopian crash on how Boeing tried to address problems with its MCAS system after the Lion Air crash.

"Were there other efforts by Boeing to essentially minimize the problem or hide the scope of the problem?" Rose asked. If lawyers can show Boeing management acted recklessly, it could clear the way for substantial punitive damages, he said.

Some lawyers who have worked on the other side of such cases are less sure about Boeing's potential liability.

Kenneth Quinn, a lawyer who represents airlines and manufacturers, said he thought Boeing had a good chance of getting both sets of U.S. cases dismissed on forum grounds.

He said the trend in U.S. courts was in Boeing's favor.

"Increasingly, attempts to litigate foreign crashes involving foreign airlines on foreign soil are being dismissed," he said.

In November, a federal judge in Washington, D.C. dismissed a case against Boeing and other defendants stemming from the disappearance of a Malaysian Airlines flight in 2014 because the presumed crash had a stronger connection to Malaysia than the United States.

In 2011, a federal judge in Los Angeles dismissed 116 wrongful death and product liability cases against Boeing over the 2008 crash of a Spanair jet on a domestic flight in Spain, where the judge determined the cases should be heard.

If the company has to defend U.S. cases, it would likely argue that claims against it are preempted because the FAA had approved the plane's design, said Justin Green, a plaintiffs lawyer.

https://mobile.reuters.com/article/amp/idUSKCN1QW05T?__twitter_impression=true

rog747

15th Mar 2019, 08:34

One options suggested by the FR data is that there was no flap set for takeoff.

The data shows a 63 second ground roll followed by a rotation at 207 knots. At this point the MCAS may have simply been doing its job.

Hard to believe this would happen, but it's happened before.

Interesting and of course would throw a spanner in -

Would any 737 MAX pilot ever entertain a flap-less takeoff from Addis with a 2300m Elev? -
This was a normal early morning departure (Temp was 16c) - busy pax load (149) for a 2 hour leg to NBO
Not sure if at or near MTOW (any cargo>?)
VR at 207 kts?
puzzled....

FlightCosting

15th Mar 2019, 08:56

AfricanSkies

15th Mar 2019, 09:03

I'm wondering why the engines seem to have been at high thrust in both accidents, this one and the Lion Air.

I'd imagine it to be a bit difficult to get to 383 knots at impact from 1000 feet agl, starting at 230kts say clean, at idle, because I imagine one of the first things one would do when the nose tipped over is reduce to idle.

sabbasolo

15th Mar 2019, 09:08

Good call Hunbet - looks like you were right !

“Evidence we found on the ground made it even more likely that the flight path was very close to Lion Air’s,”

I suspect they located the stab trim jackscrew and could tell it's position.

Also :“The FAA is ordering the temporary grounding of Boeing 737 MAX aircraft operated by U.S. airlines or in U.S. territory. The agency made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today. This evidence, together with newly refined satellite data available to FAA this morning, led to this decision," the FAA said.

https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive

A screw-like device found in the wreckage of the Boeing Co. 737 Max that crashed last Sunday in Ethiopia indicates the plane was configured to dive, a piece of evidence that helped convince U.S. regulators to ground the model, a person familiar with the investigation said late Thursday night.

Federal Aviation Administration chief Daniel Elwell on Wednesday cited unspecified evidence found at the crash scene as part of the justification for the agency to reverse course and temporarily halt flights of Boeing’s largest selling aircraft. Up until then, American regulators had held off as nation after nation had grounded the plane, Boeing’s best-selling jet model.

The piece of evidence was a so-called jackscrew, used to set the trim that raises and lowers the plane’s nose, according to the person, who requested anonymity to discuss the inquiry. (https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive)

Cloudee

15th Mar 2019, 09:36

737 MAX Software Enhancement Boeing’s Public Statement

The Boeing Company is deeply saddened by the loss of Lion Air Flight 610, which has have weighed heavily on the entire Boeing team, and we extend our heartfelt condolences and sympathies to the families and loved ones of those onboard.
Safety is a core value for everyone at Boeing and the safety of our airplanes, our customers’ passengers and their crews is always our top priority. The 737 MAX is a safe airplane that was designed, built and supported by our skilled employees who approach their work with the utmost integrity.

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.

Boeing has been working closely with the Federal Aviation Administration (FAA) on development, planning and certification of the software enhancement, and it will be deployed across the 737 MAX fleet in the coming weeks. The update also incorporates feedback received from our customers.

The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.

It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.

A pitch augmentation control law (MCAS) was implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack. It was put through flight testing as part of the certification process prior to the airplane entering service. MCAS does not control the airplane in normal flight; it improves the behavior of the airplane in a non-normal part of the operating envelope.

Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018.

Additionally, we would like to express our deepest condolences to those who lost loved ones on Ethiopian Airlines Flight 302. A Boeing technical team is at the crash site to provide technical assistance under the direction of the Ethiopia Accident Investigation Bureau and U.S. National Transportation Safety Board. It is still early in the investigation, as we seek to understand the cause of the accident.

Kolossi

15th Mar 2019, 09:37

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall.

(my emphasis) I'm reading this to mean that the intention is to "assist"(TM) during steep turns and not that a steep turn is a condition of MCAS operation.

That said, if the ATC is correct, there were issues including unusual speed/acceleration for most of the flight which would possibly have been with autopilot engaged when MCAS isn't active. The pilot requests turnback and then disappears off radar.

So, accepting it contradicts Occam's Razor and needs another cheesy hole, perhaps something else non-MCAS-related was seriously wrong, but then on turning back, MCAS nose down trim becomes the final nail in the coffin as evidenced by trim jack screw position on ground.

Rated De

15th Mar 2019, 09:55

One thing is clear amongst all the scuttlebutt, the 737 MAX is a new type not an ng with a few tweaks and a slightly different cockpit layout.
Buying a new aircraft type is a big undertaking for any airline and expensive getting their existing pilots certified on the type while still operational on the existing 737 fleet. This makes it more difficult for Boeing to sign up customers for big orders so they tricked customers into buying the MAX by certifying the aircraft as a variant so that current ng type rating applied with only new cockpit familiarity checks.

Precisely.
As year after year business schools pump out MBA graduates the only thing they conceive is cost and lowering it.
Labour unit cost is the single most controllable cost an airline has.

Manufacturers heard the drum beat a long time ago.
Regulators heard it too.

In the never ending battle of short term expense versus long term safety, the latter finishes a long way behind.

Consumers hear it too.

Our hubris as a species is incredible. We convince ourselves time and again absence of evidence is evidence of absence until again the 'unforeseen' appears again just to be re-learned as it was since long forgotten.
The normalisation of deviance.

derjodel

15th Mar 2019, 09:58

If that is the case then there is likely only one version of the code (eases management of it), but a flag set Yes or No if the fee has been paid or not.

If so, and the right code to avoid the issue was actually installed in the aircraft but deliberately switched off, lawyers for the pax, especially those from the second accident, will have a field day.

Ineed, after Lion Air I though Boeing should have made this feature available for free in all MAX airplanes. Could the ET be prevented if they had this display? Interestingly, Boeing only lost 15% at NYSE. For comparison, Volkswagen lost over 60% due to their emission scandal. But this could be, and should be big if it's due to MCAS.

deltafox44

15th Mar 2019, 09:59

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer.
If "safer" means avoiding a crash every six months, I would say that "safe" for Boeing means "dangerous". If not, why would a safe aircraft be grounded ?

krismiler

15th Mar 2019, 10:03

And this time EASA may well not rely on the FAA for lifting ban or even worse re-certification if required...

D.P. Davies required modifications to the B707 before it was allowed on the British register so the above scenario is very possible, especially if the French want to give Airbus a leg up.

I'm surprised we haven't seen the ambulance chasing lawyers descending on the victims families en mass yet. Those of us who remember the Bhopal disaster involving Union Carbide in 1984 will remember the spectacle.

RoyHudd

15th Mar 2019, 10:06

Options on a new aircraft have long been offered, just as in a motor car. Some enhance safety, some convenience, some comfort. They all cost. To incorporate all options as standard would render the product unsaleable.

If the airline decides not to take-up certain safety-related options, on their own head be it. Not the manufacturer's.

calypso

15th Mar 2019, 10:09

In summary then:

The newer engines required to optimise the MAX have a larger diameter than that allowed by the wing/ fuselage geometry. In order to fit those engines Boeing had to move them forward which changed the aerodynamic characteristics of the aircraft. That change consisted on insufficient pitch down moment when close to the stall in clean configuration. In order to meet certification criteria Boeing introduced a system that automatically moved the stabiliser to artificially induce the pitch down moment . In order to introduce this system with minimal costs existing equipment was used including a data input from a single source - the AOA probe. In order to reduce qualification costs this system was not mentioned in the MAX operation manuals.

In the Lion Air case the AOA probe was not calibrated properly, meaning the direction and magnitude where correct but the value was 20 degrees out. When the flaps where retracted the MCAS started to work as intended -based on the erroneous aoa data- by introducing bursts of down trim, those bursts got interrupted every time the pilot trimmed manually via the electric trim. At a certain point the crew started to pull hard at the yoke and the automatic stab trim cutout switch operated, with the effect that electric manual trim no longer worked, MCA trim in the other hand did continue to operate but it no longer got interrupted by manual pilot trim eventually trimming all the way nose down, a position that exceeds the authority of the elevator. At that point they only had two options left
1. Offload control column pressure to release the automatic stab trim cut-out then trim back to neutral.
2. Manually disconnect the electric stab trim via the override switches at the base of the throttle quadrant then use manual trim for the remainder of the flight.

Three crews managed the above but the fourth got overwhelmed in the Lion Air case. The Ethiopian on the face of it looks quite similar but there isn't enough data yet to even have a guess. A bit of a mess but where I tend to agree with Boeing is in which way is this any different from a classic runaway stabiliser? Ok there is more distractions going on but bottom line is if the stabiliser starts to run and you dont get on those disconnect switches soon enough you will end up in the same place.

Daysleeper

15th Mar 2019, 10:16

If the airline decides not to take-up certain safety-related options, on their own head be it. Not the manufacturer's.

Except the aircraft is required to achieve certain standards of safety and, it appears, does not achieve that standard without the option activated. Ergo the default design should have additional features and it is back with the manufacturer and their regulator to take action.

oldchina

15th Mar 2019, 10:21

deltafox44

15th Mar 2019, 10:26

The data shows a 63 second ground roll followed by a rotation at 207 knots. At this point the MCAS may have simply been doing its job.
The FR24 data do NOT show that.

After about 45" roll (05:38:45.798) and for 5 seconds the ground speed is stable at 182/183 kts while the vertical speed is positive, reaching 2368 ft/mn. Though the pressure altitude is not consistent with the speed and vspeed evolution, speed and vspeed indicates the aircraft is already airborne and climbing at 182 kts (about 170 kts IAS). And one minute later it has gained 1000 ft and speed (250 kts). Then only the problems begin, may be after retracting the flaps.

Rated De

15th Mar 2019, 10:32

Rated De said "As year after year business schools pump out MBA graduates the only thing they conceive is cost and lowering it"

Stop and think whether this is not utter nonsense.
You imagine Airbus gave the A320 a seven inches wider fuselage than the 737 to save operating cost?

Did they build the MCAS?
MCAS saved re-certification cost. It appears increasingly likely that a system considered necessary for safety wasn't explained and trained to the pilot. Why do you think that would be?

Post graduate courses are indeed pumping out the said graduates.
When did Airbus actually design the A320?

Go and listen to the opinions of the Boeing engineers who actually used to build the product.
Listen to what they say changed. Then have a look at any Ivy league business school, read the curriculum, look at the individual modules and see what the graduate is focused upon.

https://www.youtube.com/watch?v=rvkEpstd9os

deltafox44

15th Mar 2019, 10:39

Three crews managed the above but the fourth got overwhelmed in the Lion Air case. The Ethiopian on the face of it looks quite similar but there isn't enough data yet to even have a guess. A bit of a mess but where I tend to agree with Boeing is in which way is this any different from a classic runaway stabiliser? Ok there is more distractions going on but bottom line is if the stabiliser starts to run and you dont get on those disconnect switches soon enough you will end up in the same place.

Two crashes and 3 near crashes, that means that only above average (or more lucky) pilots can avoid a crash after a single AOA sensor failure... :ooh:

It would be interesting to know whether the MCAS ever was activated and avoided a stall in nominal conditions :confused:

averow

15th Mar 2019, 10:49

Prag

15th Mar 2019, 10:52

Bird strike or ramp rash or software error are three most obvious- the point is to alllow a SINGLE sensor to directly override pilot input and not be documented that it even exists is as close to criminal as one can imagine.

There is no such thing as 100% reliable sensor. You can vote in software, but in case of two sensors you dont know, which value is OK and which is bad, you need at least three to have confident voting system. There are much better options sw engineer can use, if he knows something about the subject and phisical reality it deals with. I'm just plain earth based industry programmer, but can imagine some verification methods that works even with one sensor. The basic method is to observe sensor behavior in time, just as you watching if it works by your own eyes, in many phases of flight.
- during the takeoff run just before plane goes airborne, you can assume that values AoA should be close to zero. If not, sensor is stuck or misaligned.
- after that should the values change to positive normal range, if not, the sensor is stuck. This is also the case of normal in/flight behavior, values in acceptable range, that change slowly and possibly with small difference between two sensors according to actual flight conditions. So you can tell its still living and not stuck somewhere.
And the most significant, dont check for value constantly over the set threshold. You should check if value rises from accepted range dynamically and in one moment oversets it, then act.
Programmers working for Boeing or component manufactors should have known this. I'm somewhat surprised they obviously dont. Or maybe the flight computer is totally out of resources after mods.

DaveReidUK

15th Mar 2019, 10:58

Capt Kremin

15th Mar 2019, 11:11

The FR24 data do NOT show that.

After about 45" roll (05:38:45.798) and for 5 seconds the ground speed is stable at 182/183 kts while the vertical speed is positive, reaching 2368 ft/mn. Though the pressure altitude is not consistent with the speed and vspeed evolution, speed and vspeed indicates the aircraft is already airborne and climbing at 182 kts (about 170 kts IAS). And one minute later it has gained 1000 ft and speed (250 kts). Then only the problems begin, may be after retracting the flaps.

You must be looking at different data then.
The vertical speed is positive but nothing happens to the altitude till 207 knots is reached. The other possible scenario, which is probably more likely, may be that the aircraft was carrying out a Flaps 1 takeoff, which would be consistent with the speeds reached on the runway at rotate and the gear up call, (the 182 knots). The brand new FO, who at 200 hours may have been doing his first line sector, then inadvertently selected flap up instead of gear up. The aircraft settled back on to the runway and the captain rotated again at 207 knots, which would be a normal recovery, but now the MCAS is activated in a hot and high, extremely low altitude situation.

We will know soon anyway. The flight recorders are being looked at now in Germany.

jsypilot

15th Mar 2019, 11:15

You must be looking at different data then.

We will know soon anyway. The flight recorders are being looked at now in Germany.

I thought that they were in France.

Hotel Tango

15th Mar 2019, 11:16

I think that Capt Kremin is out of touch!

DaveReidUK

15th Mar 2019, 11:22

I thought that they were in France.

They are. Presumably at Le Bourget, HQ of the BEA.

I don't buy the "double rotation" scenario either.

N600JJ

15th Mar 2019, 11:22

Wondering if / when was AP engaged on ET302 - FDR will tell

Rated De

15th Mar 2019, 11:25

It's utter nonsense for many reasons, not least because of this odd idea that getting an MBA turns humans into sociopaths. All this rhetoric about bean counting, criticism of an aviation culture that has become one in which the industry doesn't care if people die, that pilots can't fly planes any more, and that technology has made planes unsafe, flies in the face of aviation safety statistics which show a continuous reduction in fatality frequency that any industry would be immensely proud of.

We simply do not live in a world in which humans don't make mistakes. To err is human. We must always learn from mistakes, and the history of aviation safety is an exemplar of that. Excluding malicious acts, every single death in the history of travel has occurred because one or more people made a mistake in strategy, decision making, design, or operation. It's quite possible that the Max story is going to become a classic safety case study. But witch hunting doesn't get us anywhere.

So the statistics of which you speak saw the Challenger launch successfully 10 times.
So the statistics of which you speak saw the 737 MAX fly successfully until it didn't last year. Statistically, extrapolating the hull loss of the 737 MAX indicates that the hull loss rate is now intolerable.
So which statistical data set is the valid sample?

The focus of the post graduate program in the modern age is to be relevant to business. Perpetual profit in a finite world is utter nonsense, yet every graduate is taught grow revenue and cut cost. Seemingly inexhaustible right?
How low can cost be cut before it matters? An endless loop question?
Nobody stated the graduates were sociopaths, that is alarmist. What is obvious to those of us who witness it is that these graduates know little of process, know little of design. Their skill set can be readily applied to any corporate endeavour. After all it is marketed as an Masters of Business Administration (Generic) One size fits all.

The normalisation of deviance is not a witch hunt, it is a scientific investigation into acceptance of deviance from safe practice.
The deviation takes place an increment at a time. Boeing engineers foretold their concerns about Boeing. The very people charged with building the product stated the process had been compromised.
Their focus was not to be quality, rather schedule and self evidently cost.

Management documents state that clearly, deviation from accepted quality was permitted to protect schedule. Not the 737 MAX program incidentally, it was the 787.
Similarly, the NASA engineers had their concerns with O-Ring by pass. As did the engineers of Morton Thiokol.
Progam management dismissed their concerns, focused on schedule and budget.

Sound familiar?
Program cost, budgets, schedule and commercial viability overcame opposition from concerns for launch integrity. Everybody knows what happened next.

The case study of which you speak need not have been the 737 MAX. People made mistakes in design, strategy, decision making and operation.
The Boeing 787 program had all the hallmarks, the engineers in Boeing noticed the change, they called out the deviance. Statistically they have gotten away with it so far.

Perhaps the 737 MAX need not be a case study, the Challenger Launch Decision shows the template to anybody bothered enough to read it, having read it, the similarities are stark.

If this horrible loss of life was triggered by the same system that is believed responsible for the Lion Air accident, then statistically Boeing is going to have a hard time pointing to their statistics.

admiral ackbar

15th Mar 2019, 11:29

boeingboy737

15th Mar 2019, 11:56

gums thanks for the reply jimtx i did not read all the pages so excuse me.. i was just wondering if there was something more to this. just wanted to know if the MCAS system has its own non controllable trim motors that we cant shut off in the cockpit!!! I know how its is supposed to work based on what I have been trained on. I flew one on tuesday and had NO issues. And by the way 20k plus years and hours in the 737!

ivor toolbox

15th Mar 2019, 11:58

This seems a poor FAA perspective. By definition, 50% of pilots will be below that average skill level.

Particularly when they only have 200 hours total.

It is what is written in part 14 of the electronic code of federal regulations. And while youre looking there, take a look at chapter 25. 672

Ttfn

EDML

15th Mar 2019, 12:04

One options suggested by the FR data is that there was no flap set for takeoff.

The data shows a 63 second ground roll followed by a rotation at 207 knots. At this point the MCAS may have simply been doing its job.

Hard to believe this would happen, but it's happened before.

1. I don‘t think it is possible to survive a flapless T/O at this density altitude and take off mass.
2. Even if they did - after reaching 1000ft and 300kt everything is fine and they could have continued the flight. However, here the disaster started at this point of the flight.

MPN11

15th Mar 2019, 12:16

Would the reported high speed of the aircraft in the latter stages (383 kts, as cited upthread) go to explain the 'falling debris' mentioned by eyewitnesses? Could that speed have started to initiate hull breakup, or detaching of some other components?

Sailvi767

15th Mar 2019, 12:24

FCeng84

15th Mar 2019, 12:35

If that is the case then there is likely only one version of the code (eases management of it), but a flag set Yes or No if the fee has been paid or not.

If so, and the right code to avoid the issue was actually installed in the aircraft but deliberately switched off, lawyers for the pax, especially those from the second accident, will have a field day.

The display options that Southwest and others purchased provides digital readout of AOA as sensed by each of the AOA vanes and a light bringing attention to significant disagreement between those two measurements. It is my understanding that the pair of digital displays and the disagree light may be fitted or just the disagree light. The operation of the control laws and the stick shakers that are driven by the AOA vane sensors are the same whether or not these display options are included on the flight deck.

DaveReidUK

15th Mar 2019, 12:45

The display options that Southwest and others purchased provides digital readout of AOA as sensed by each of the AOA vanes and a light bringing attention to significant disagreement between those two measurements.

Are you referring to the AoA display on the PFD, or to a separate annunciator that isn't present at all on non-equipped aircraft?

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/428x382/b737_pf_with_aoa_indicator_606aa7cd007c496349d8683d28e97c6c9 55dbdd4.jpg

Icarus2001

15th Mar 2019, 12:47

For comparison, Volkswagen lost over 60% due to their emission scandal. But this could be, and should be big if it's due to MCAS.

A ridiculous comparison. VW set out to deceive and cheat the emission testing for commercial gain. Boeing added a function to enhance safety when operating at the edge of the envelope, somewhere most crews should and will never be but perhaps a faulty sensor and lack of a second input has caught them out.
Just remember that the crew who flew the affected Lion Air aircraft the day before the fatal managed to land safely. There are trim cut outs, manual trim and electric trim all of which override MCAS inputs.

Jo90

15th Mar 2019, 12:48

BRE

15th Mar 2019, 12:51

and some more data

https://www.theatlantic.com/notes/2019/03/heres-what-was-on-the-record-about-problems-with-the-737-max/584791/

https://asrs.arc.nasa.gov/overview/database.html

Two cases where the aircraft pointed down just after AP engagement, and crew were aware that the augmentation system was only active with flaps 0 and no AP. Couldn't figure out a setup problem with the AP in either case.

So why did they report to the anonymous NASA system and not to their airline and the FAA to have the QAR pulled right away and conserve date?

FCeng84

15th Mar 2019, 12:53

Are you referring to the AoA display on the PFD, or to a separate annunciator that isn't present at all on non-equipped aircraft?

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/428x382/b737_pf_with_aoa_indicator_606aa7cd007c496349d8683d28e97c6c9 55dbdd4.jpg

I am not familiar with the AOA display layout so I am not sure if the AOA display option that Southwest has purchased is what you show on the PFD or another readout. My comment about displays was based on previous inputs by others on this forum. My comment about the display option not impacting control law logic is based on a number of sources - I am very confident in that.

JamesT73J

15th Mar 2019, 12:55

What about the mentions of speed being far too high, even while they were climbing to a safer altitude?

That isn't a CoG or trim issue ... ??

With the engines at takeoff thrust a low pitch angle would have the thing sledding along pretty quickly, I would guess. Especially if they weren't keeping an eye on it.

GLAEDI

15th Mar 2019, 12:56

Piece Found at Boeing 737 Crash Site Shows Jet Was Set to DiveBy
Alan Levin (https://www.bloomberg.com/authors/AQjkBDLS74Y/alan-levin)March 15, 2019, 12:06 AM EDTUpdated on March 15, 2019, 6:59 AM EDT

Screw was said to be configured to put plane into a dive
Downing of Boeing 737 Max in Ethiopia has grounded fleet

https://assets-bwbx-io.cdn.ampproject.org/i/s/assets.bwbx.io/images/users/iqjWHBFdfxIU/ilW7WVaoXmNg/v5/830x-1.jpg Boeing Suspends All 737 Max Aircraft Deliveries A screw-like device found in the wreckage of the Boeing Co. (https://www.bloomberg.com/quote/BA:US) 737 Max 8 that crashed Sunday in Ethiopia has provided investigators with an early clue into what happened, as work begins in France to decode the black boxes recovered from the scene.

The so-called jackscrew, used to set the trim that raises and lowers the plane’s nose, indicates the jet was configured to dive, based on a preliminary review, according to a person familiar with the investigation. The evidence helped persuade U.S. regulators to ground the model, said the person, who requested anonymity to discuss the inquiry.

France’s aviation safety agency BEA received the cockpit voice and data recorders on Thursday for decoding, while investigators on the scene near Addis Ababa continue to sift through the plane’s wreckage. The second crash in five months has thrown Boeing into a crisis, sending the shares plunging and raising questions about the future of its best-selling jet.

Separately, the New York Times reported (https://www.bloomberg.com/news/articles/2019-03-14/doomed-boeing-jet-s-radio-messages-showed-immediate-problem-nyt) that doomed Ethiopian Airlines Flight 302 to Nairobi was in trouble almost immediately after takeoff as it lurched up and down by hundreds of feet at a time. The captain asked in a panicky voice to turn back only three minutes into the flight as the plane accelerated to abnormal speeds, the newspaper reported, citing a person who reviewed the jet’s air traffic communications.

"Break break, request back to home," he told air traffic controllers as they scrambled to divert two other flights approaching the airport. The aircraft had accelerated far beyond what is considered standard practice. All contact between air controllers and the aircraft was lost five minutes after it took off, the report said.

Read: Black Box Politics: How National Pride Intrudes on Crash Probes (https://www.bloomberg.com/news/articles/2019-03-15/black-box-politics-how-national-pride-intrudes-on-crash-probes)

Federal Aviation Administration chief Daniel Elwell on Wednesday cited unspecified evidence found at the crash scene as part of the justification for the agency to reverse course and temporarily halt flights (https://www.bloomberg.com/news/articles/2019-03-13/trump-says-u-s-grounding-boeing-737-max-aircraft-after-crash) of Boeing’s largest selling aircraft. Up until then, American regulators had held off even as nation after nation had grounded the model.

Boeing shares have lost 12 percent, or $28 billion in market value, since Ethiopian flight 302 went down on March 10. The shares were trading at $372.20 in early U.S. trading Friday, little changed from Thursday’s close.

Read more: Chart on Boeing’s drop in market value (https://www.bloomberg.com/news/terminal/PODWO5SYF01U)

The jackscrew, combined with a newly obtained satellite flight track of the plane, convinced the FAA that there were similarities to the Oct. 29 crash of the same Max model off the coast of Indonesia. In the earlier accident, a safety feature on the Boeing aircraft was repeatedly trying to put the plane into a dive as a result of a malfunction.

Read More: Black Box Politics: How National Pride Intrudes on Crash Probes (https://www.bloomberg.com/news/articles/2019-03-15/black-box-politics-how-national-pride-intrudes-on-crash-probes)

All 157 people aboard died after the plane crashed near Addis Ababa, Ethiopia’s capital. The jet’s flight recorders are in France, where they are being analyzed at the BEA’s laboratories. The agency posted a photo of the mangled hardware and has yet to comment on any progress on getting the data. “The investigation process has started in Paris,” Ethiopian Airlines said in a Twitter post on Friday.

Sailvi767

15th Mar 2019, 12:59

MPN11

15th Mar 2019, 13:06

No, at the density altitude they were at that speed would be well under VNE.
Thank you ... it was just a passing thought.

pilotmike

15th Mar 2019, 13:13

Quote:For comparison, Volkswagen lost over 60% due to their emission scandal. But this could be, and should be big if it's due to MCAS.

A ridiculous comparison. VW set out to deceive and cheat the emission testing for commercial gain. Boeing added a function to enhance safety when operating at the edge of the envelope, somewhere most crews should and will never be but perhaps a faulty sensor and lack of a second input has caught them out.
Just remember that the crew who flew the affected Lion Air aircraft the day before the fatal managed to land safely. There are trim cut outs, manual trim and electric trim all of which override MCAS inputs.

Quite the opposite; it is a very good comparison - the paralles are very clear to see.

VW had to build a car that could pass the emissions standards. They achieved, through cunning, for commercial gain. And it polluted more than it should have.
Boeing had to build an aircraft that could pass certification. They achieved, through cunning, for commercial gain. Evidence suggests it has killed more people than it should.

Running Ridges

15th Mar 2019, 13:27

No, at the density altitude they were at that speed would be well under VNE.

Really? From what I can see Vmo is 340kts on the -800, not sure about the MAX but can't imagine it's different
383kts TAS is 339kts EAS at 8000'

slip and turn

15th Mar 2019, 13:27

1. I don‘t think it is possible to survive a flapless T/O at this density altitude and take off mass.My thoughts too when I also started musing about why a possible first rotation seem to fail (where those first VS reports occurred 2/3rds along the runway, and which DaveReidUK is inclined to put aside pending further clues :O) and then they seemed to use so much runway with no height gain, but at the lat/long of Capt Kremin's chosen 207kts GS datapoint (seemingly some 1700ft into the dirt), that dirt beyond the paved areas has already fallen perhaps 150 feet from the runway (according to Google Earth elevations). So it is no Courchevel, and no USS Gerald R. Ford (http://www.navy.mil/ah_online/ussford/), but the terrain beyond the runway with or without approach light towers, does perhaps offer a little launch ramp type forgiveness.

It is lucky for analysts, that by that point we have no less than 15 ADS-B "airborne" datapoints covering 80% of the available runway and all points without a hint of any spuriousness are located slap bang along the centreline of 07R. Clearly ET302 wasn't airborne at 93kts GS where the first airborne report became available, but that's no real mystery in itself. So thus far I do not question the accuracy of the ADS-B GPS locations reported. It is the altitudes, groundspeeds and vertical speeds which are more questionable, but not overly so. Indeed the altitudes reported along the middle of the runway do seem to reflect moderate undulations found in Google Earth. Whether Google Earth elevations are accurate along the runway is another story.
2. Even if they did - after reaching 1000ft and 300kt everything is fine and they could have continued the flight. However, here the disaster started at this point of the flight. ... everything is fine?? Are we sure about that? Where for example do we reckon they actually reached 1000ft above anything until the last few datapoints of the FR24 data?? And on the same score please, DaveReidUK, what point are you calling rotation and what point are you calling 1050ft AAL?

Sailvi767

15th Mar 2019, 13:33

DaveReidUK

15th Mar 2019, 13:43

And on the same score please, DaveReidUK, what point are you calling rotation and what point are you calling 1050ft AAL?

I believe rotation was at approximately the 05:38:47 datapoint (certainly before the next point at 05:38:50).

1050' AAL (8150' ADS-B altitude) was achieved by 05:39:50.

Sailvi767

15th Mar 2019, 13:46

Really? From what I can see Vmo is 340kts on the -800, not sure about the MAX but can't imagine it's different
383kts TAS is 339kts EAS at 8000'

Density altitude would have been above 10,000 feet at airport elevation. 11,000 feet if peak speed was at 1000 AGL

.Scott

15th Mar 2019, 14:17

derjodel

15th Mar 2019, 14:29

If this is what it appears to be - a problem that will need to be addressed by changing firmware and perhaps hardware, then the MAXs may be grounded for weeks or months.
Flight firmware is not quickly developed and certified.

787 was grounded for a month and the solution was a simple cage. I'm 100% sure there is no simple software solution for MCAS. Remember, MCAS is required for (self) certification, so it needs to be there in certain conditions. But it simply can't be there with only two AOA sensors, no matter how you hack it. Whatever you do, it could happen that MCAS does't engage when it should -> hence no certification, or it does when it's deadly.

slip and turn

15th Mar 2019, 14:40

I believe rotation was at approximately the 05:38:47 datapoint (certainly before the next point at 05:38:50). OK so it is not until 17 or 20 secs later that you reckon the VS figures begin to read true? And given the airfield elevation 7625' you are deducting how many feet for the QNH1029 correction to convert the 1013hPa 8or 1013.25hPa or 29.92inHg as you will) ADS-B figures to AAL?

1050' AAL (8150' ADS-B altitude) was achieved by 05:39:50.That implies you may have converted thus: 8150'-7625'+525'=1050'. Are you using 1029-1013.25=15.75 and 15.75hPa x 33.3'/hPa=525'? Because I would use 1029-1013.25=15.75 and 15.75hPa x 27.3'/hPa=430' and conclude that at the 05:39:50 datapoint ET302 was around 950' some odd AAL, but then I may have it all wrong if I am to adjust the rate up from 27.3 to 33.3 because we are well above sea level - if so, I missed it at school :O

infrequentflyer789

15th Mar 2019, 14:41

Having read (well skimmed) the interim report of the Lion accident particularly the part relating to the previous flight, it occurs to me that following a flight with major instrument discrepancies, continuous stick shaker and multiple uncommanded stab trim movements it might have been appropriate to add something to the tech log entries like "aircraft unfit for revenue flight pending maintenance action".
Would that have prevented the accident?

Maybe, maybe not. Remember, they did log uncommanded trim movements ("STS trimming wrong" - remember they had no knowledge of MCAS even existing) and maintenance action was taken before the last flight - it just didn't find or fix the real problem.

Also, even if it had prevented that accident, it wouldn't prevent one where the first crew that hits the problem cannot cope with it (and ET may well be that).

When trying to pin blame on crews, airlines, maintenance remember that the 737 MAX is a new variant of an existing type (lets restrict to the NG for comparison), same type certificate, same type rating, so similar that the only pilot training is apparently a powerpoint.

NG: ~7000 in service, 16 losses in >20 yrs
MAX: ~ 350 in service, 2 losses in <3 yrs

- same crews
- same training (modulo the powerpoint)
- same airlines
- same maintenance
- same procedures

MAX simply crashes more often, and there's a pattern (shortly after takeoff, flight control problems reported, uncontrolled dive). Even without any knowledge of MCAS you would have to say that there is something wrong with this aircraft and that it's something in the changes from the NG.

clearedtocross

15th Mar 2019, 14:51

System bugs are caused for three main reasons:
1. Bad Specs
2. Faulty implementatation
3. Incomplete tests and hasty correction of faults.

#1 is by far the worst because it affects #2 and #3 as well and may not be detected during the whole development process.What‘s worse is that in complex developments, this process is cascaded from one system to all of its subsystems.
So here we have an airplane design spec that was most likely not taking into account the aerodynamic behaviour of relocating the engines. I bet the problem was only detected after some test flying of the new airplane. So time runs out, a redesign of the aircraft is now impossible and so a software patch is called for to get better stall protection. The aircraft is not FBW and thus the triple redundancy and voting concept is neither required nor followed. And as all software engineers know, patches sometimes backfire because they have not been designed with the same care as the original system. Ask Bill Gates.

But the patched system is not self-contained, not isolated, it affects and is affected by a lot of other systems and components. If some of these sensors and systems feed wrong air-data, the result is unpredictable probably even for the inventors, but certainly for the poor pilots affected and for the majority of ppruners including me.

Now some of you say „hey that‘s just a little speed bump“, remain cool and switch some breakers and fly away serenely. Thats okay for the Chuck Yeagers and Neil Armstrongs. Those not having been trained as test pilots remain confused and try to fight a plane that does not behave as advertised and tries to kill you and your passengers. They might remember some FAA AD about trim anomalies when they are waiting to pass the pearly gates.

Conclusion: This patch is much worse than the original stability problem. Many aircraft pitch up to a stall if uncorrected after full power is applied, at least mine does. That‘s no issue. It baffles me that a device that can trim a jet fully nose-down without pilot input - caused by some erronous airdata - could ever be conceived and then certified and the facts about this box of Pandora not being passed on to the type-rated pilots and training facilities.

EDML

15th Mar 2019, 15:31

... everything is fine?? Are we sure about that? Where for example do we reckon they actually reached 1000ft above anything until the last few datapoints of the FR24 data?? And on the same score please, DaveReidUK, what point are you calling rotation and what point are you calling 1050ft AAL?

Why not? If you accidently take off w/o flaps the critical moment is when you get out of ground effect. If you manage to accelerate out of that low energy state the aircraft is perfectly flyable. 300kt TAS at 11000ft DA is for sure a safe clean speed. All you might need to do is trim and pull into a normal climb angle.

After a flapless T/O the critical moments would be before reaching 1000ft and not thereafter.

MELT

15th Mar 2019, 15:39

[QUOTE

"So here we have an airplane design spec that was most likely not taking into account the aerodynamic behaviour of relocating the engines. I bet the problem was only detected after some test flying of the new airplane. So time runs out, a redesign of the aircraft is now impossible and so a software patch is called for to get better stall protection."

Clearedtocross, suspect you are spot on with this, and it wouldn't be the first time this has occurred either.

I think Boeing will be lucky to have the aircraft back in the air within 6 months.

CONSO

15th Mar 2019, 15:41

Management documents state that clearly, deviation from accepted quality was permitted to protect schedule. Not the 737 MAX program incidentally, it was the 787.

Not unique to 787- for way too many years after Bill Allen retired, the mantra was ( is ? ) the three most important things in the factory are Schedule- and the other two dont count.
Often its ' load date' ( first load into a specific assembly jig.) Of course other variations - but the basic driving force is the same.

777 was a bit different as both Phil and Alan pushed the ' working together ' mantra in Engineering- and a reasonable amount of it trickled down to shop.

CONSO

15th Mar 2019, 15:46

So why did they report to the anonymous NASA system and not to their airline and the FAA to have the QAR pulled right away and conserve date?

preservation of job ? uncertain as to problem ? simple write up in log ' check ..... "

Rolesium

15th Mar 2019, 15:55

Not trying to defend the MCAS or anything, but wouldn't the last line of defense be the pilots' proficiency to identify the immediate problem and hit the Stab Trim cutout switch if there's a runaway trim in any event? Ample type-specific flight training in this case plays the biggest role in whether one is capable of saving the plane from crashing or not, in spite of not having the "paid" AoA indicator. Granted, the MCAS might've gone rogue on the ET flight, but pilot error seems to be the ultimate cause that sealed the aircraft's fate ..
As evident in the DPS-CGK Lion flight, crew handled the situation pretty well. Landed the plane safely.

Just my 0.02

Luc Lion

15th Mar 2019, 15:57

...
So here we have an airplane design spec that was most likely not taking into account the aerodynamic behaviour of relocating the engines. I bet the problem was only detected after some test flying of the new airplane. So time runs out, a redesign of the aircraft is now impossible and so a software patch is called for to get better stall protection. The aircraft is not FBW and thus the triple redundancy and voting concept is neither required nor followed. And as all software engineers know, patches sometimes backfire because they have not been designed with the same care as the original system. Ask Bill Gates.

What I find hard to understand is why Boeing didn't elect to upgrade the Elevator Feel System for compensating this undesired aerodynamic behaviour and instead created a new MCAS software module in the FCC.

Smythe

15th Mar 2019, 16:04

Article that looked at pilot filings on the MCAS issue...looks like it was common at early DEP, but handled by turning off Autopilot?

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.

This description is not currently in the 737 Flight Manual Part 2, nor the Boeing FCOM, though it will be added to them soon. This communication highlights that an entire system is not described in our Flight Manual. This system is now the subject of an AD.

I think it is unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models. The fact that this airplane requires such jury rigging to fly is a red flag. Now we know the systems employed are error prone--even if the pilots aren't sure what those systems are, what redundancies are in place, and failure modes.

https://www.theatlantic.com/notes/2019/03/heres-what-was-on-the-record-about-problems-with-the-737-max/584791/?utm_medium=offsite&utm_source=yahoo&utm_campaign=yahoo-non-hosted&yptr=yahoo (https://www.theatlantic.com/notes/2019/03/heres-what-was-on-the-record-about-problems-with-the-737-max/584791/?utm_medium=offsite&utm_source=yahoo&utm_campaign=yahoo-non-hosted&yptr=yahoo)

Smythe

15th Mar 2019, 16:08

I had my first flight on the Max [to] ZZZ1. We found out we were scheduled to fly the aircraft on the way to the airport in the limo. We had a little time [to] review the essentials in the car. Otherwise we would have walked onto the plane cold.

My post flight evaluation is that we lacked the knowledge to operate the aircraft in all weather and aircraft states safely. The instrumentation is completely different - My scan was degraded, slow and labored having had no experience w/ the new ND (Navigation Display) and ADI (Attitude Director Indicator) presentations/format or functions (manipulation between the screens and systems pages were not provided in training materials. If they were, I had no recollection of that material).

We were unable to navigate to systems pages and lacked the knowledge of what systems information was available to us in the different phases of flight. Our weather radar competency was inadequate to safely navigate significant weather on that dark and stormy night. These are just a few issues that were not addressed in our training.

I recommend the following to help crews w/ their introductory flight on the Max:
Email notification the day before the flight (the email should include: Links - Training Video, PSOB and QRG and all relevant updates/FAQ's)
SME (Subject Matter Expert) Observer - the role of the SME is to introduce systems navigation, display management, answer general questions and provide standardized best practices to the next generation aircraft.

Additionally, the SME will collect de-identified data to provide to the training department for analysis and dissemination to the line pilots regarding FAQs and know systems differences as well best practices in fly the new model aircraft.

Synopsis

B737 MAX First Officer reported feeling unprepared for first flight in the MAX, citing inadequate training.

etrang

15th Mar 2019, 16:13

Yes, except that this was not something that "slowly occurred" to the regulators: it was a deliberate political decision for "light-handed regulation" and self-regulation, taken throughout Anglophonia, in the belief that the market would ensure that the regulated entities would want to keep their good reputation (for commercial reasons), and so could attend to the material aspects of regulation, without being stifled by "bureaucratic inertia." We now see the costs, in many industries, in lives that would not have been lost under the old regime.

Well, it worked so well with the banking industry that they thought they would try in aviation.

marconiphone

15th Mar 2019, 16:22

1. Complacency, common in market leaders.

And/or

2. Gutlessness - unwillingness to recommend action that would cost (a) money; (b) damage to the company's reputation and customer relationships; (c) career prospects of superiors in corporate hierarchy.

infrequentflyer789

15th Mar 2019, 16:34

Remember, MCAS is required for (self) certification, so it needs to be there in certain conditions. But it simply can't be there with only two AOA sensors, no matter how you hack it. Whatever you do, it could happen that MCAS does't engage when it should -> hence no certification, or it does when it's deadly.

This is the key I think, triggering MCAS only when both FCCs (and therefore both AOAs) say so would surely be comparatively trivial and they would have done that IF the certification allowed it, ergo it likely doesn't.

Other points to consider:
- the earlier AD implies that MCAS still operates (presumably by design) even in event of AOA disagree (if that warning option is fitted)
- one (only) AOA sensor is on the MMEL for NG, but not for MAX
- speed trim is on MMEL, even for MAX
- MCAS... is not

All starts to look like MCAS is a "must work", more so than speed trim (also required for certification, but can be MELed). What seems to have gone very badly wrong is the assessment of the consequences (rather than the likelihood) of incorrect activation.

As you say, you can't fix this with just two AOA inputs. Adding a third AOA sensor (or calculated reference as on 777/787) to allow everything to work with one failure is going to be a big job.

FullWings

15th Mar 2019, 16:37

Originally Posted by CONSO https://www.pprune.org/images/buttons/viewpost.gif (https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa-post10419033.html#post10419033)
Bird strike or ramp rash or software error are three most obvious- the point is to alllow a SINGLE sensor to directly override pilot input and not be documented that it even exists is as close to criminal as one can imagine.
There is no such thing as 100% reliable sensor. You can vote in software, but in case of two sensors you dont know, which value is OK and which is bad, you need at least three to have confident voting system. There are much better options sw engineer can use, if he knows something about the subject and phisical reality it deals with. I'm just plain earth based industry programmer, but can imagine some verification methods that works even with one sensor. The basic method is to observe sensor behavior in time, just as you watching if it works by your own eyes, in many phases of flight.
- during the takeoff run just before plane goes airborne, you can assume that values AoA should be close to zero. If not, sensor is stuck or misaligned.
- after that should the values change to positive normal range, if not, the sensor is stuck. This is also the case of normal in/flight behavior, values in acceptable range, that change slowly and possibly with small difference between two sensors according to actual flight conditions. So you can tell its still living and not stuck somewhere.
And the most significant, dont check for value constantly over the set threshold. You should check if value rises from accepted range dynamically and in one moment oversets it, then act.
Programmers working for Boeing or component manufactors should have known this. I'm somewhat surprised they obviously dont. Or maybe the flight computer is totally out of resources after mods.
I agree with CONSO here. With just one sensor you have to do lot of magic with the input and it gets flaky near the edge of the envelope and/or when there are unusual environmental conditions present, which is just when you need it the most.

Any form of redundancy would be better, even if you just disabled the system when there was a difference between the sensors and displayed a caution to that effect. At least then you are back to pilot inputs only, rather than random stabiliser motion. GIGO, as they say...

EDML

15th Mar 2019, 16:37

What I find hard to understand is why Boeing didn't elect to upgrade the Elevator Feel System for compensating this undesired aerodynamic behaviour and instead created a new MCAS software module in the FCC.

Elevator feel / feedback is a simple mechanical system. It is not possible to simply extend that to cover special parts of the flight envelope.

etrang

15th Mar 2019, 16:45

For me it's difficult to see how this doesn't potentially finish off the "Max" IMO.

Increasingly the perception is that It isn't really a software problem, it's a aerodynamics design problem. Apparently those engines don't work with that body, at least not comfortably. Sure it can be sellotaped over with some software fixes/more sensor redundancy, whatever. But it doesn't solve the design issue and nowadays it isn't only regulator certification that has to be overcome, it's "public opinion certification" as well. We're not in the DC-10 era where controversy takes years to eek out into the open but in the age of instant global knowledge - even if that knowledge is incomplete or based on un-authoratitive sources. 1 hull loss can maybe be got away with by saying "we fixed it". But with 2 it's difficult to see how any ongoing controversy doesn't just mean that people won't refuse to get on the thing.

I think Boeing will definitely have to think of a new name for the MAX. B737 Voyager, B737 Discovery?

.Scott

15th Mar 2019, 16:56

If this is what it appears to be - a problem that will need to be addressed by changing firmware and perhaps hardware, then the MAXs may be grounded for weeks or months.
Flight firmware is not quickly developed and certified.
But Boeing is saying perhaps only 10 days...
https://www.cnbc.com/2019/03/15/boeing-shares-rise-on-report-that-company-will-roll-out-software-upgrade-for-737-max-in-10-days.html

I'm a Software Engineer. Paint me incredulous.

deltafox44

15th Mar 2019, 16:57

You must be looking at different data then.
The vertical speed is positive but nothing happens to the altitude till 207 knots is reached. The other possible scenario, which is probably more likely, may be that the aircraft was carrying out a Flaps 1 takeoff, which would be consistent with the speeds reached on the runway at rotate and the gear up call, (the 182 knots). The brand new FO, who at 200 hours may have been doing his first line sector, then inadvertently selected flap up instead of gear up. The aircraft settled back on to the runway and the captain rotated again at 207 knots, which would be a normal recovery, but now the MCAS is activated in a hot and high, extremely low altitude situation.

We will know soon anyway. The flight recorders are being looked at now in Germany.I'm referring to FR24 CSV data sheet downloaded from their blog : https://www.flightradar24.com/blog/flightradar24-data-regarding-the-crash-of-ethiopian-airlines-flight-302/

"nothing happens to the altitude till 207 knots is reached" : yes, altitude when reaching 207 kts is 7300 ft, it has been continuously rising for 16 seconds since 7075 ft at 182 kts

I admire your perspicacity (or is it imagination ?) but initiating rotation 225 ft above runway level puzzles me :confused:

PJ2

15th Mar 2019, 17:00

"The normailization of deviance." This. Exactly this. Shown to be a factor in many disasters, including Challenger. Sober thinking, smart people advised against certain actions and designs, and were shut down by others worried more about short term costs or schedule pressure.

Diane Vaughan coined this phrase in 1996 in her sociological examination of culture and deviance at NASA prior to the Challenger accident, (The Challenger Launch Decision).

The book is worth having in any flight safety library and is worth reading in the present circumstances, not because "it applies", but because don't know if it does but we need to find out.

Luc Lion

15th Mar 2019, 17:07

Elevator feel / feedback is a simple mechanical system. It is not possible to simply extend that to cover special parts of the flight envelope.
CORRECTION: Do you mean that what Boeing calls a "Elevator Feel Computer" is actually a mechanical computer ??? :bored::confused:

This is correct for the Elevator Feel Shift (EFS) module which simply increase by a factor 4 the system A pressure fed into the Elevator Feel & Centering Unit.
It is also true for the Elevator Feel & Centering Unit which transforms differential pressure into feel forces.
But the pressure normally fed into the Elevator Feel & Centering Unit is controlled by a computer unit, the Elevator Feel Computer, which uses airspeed and stab position inputs for computing how much hydraulic pressure it should transfer downstream.
I reckon that the AoA is NOT documented as an input data received by the Elevator Feel Computer ; AoA is only available to the EFS (in this area).
But an upgrade of the Elevator Feel Computer by adding AoA input and modifying its algorithms should not be more considerable than fixing the MCAS logic with dual AoA input.
The advantage of acting through the Elevator Feel System is obvious : no effect on the pilot pitch authority if the AoA probe goes mad in normal flight.

Vessbot

15th Mar 2019, 17:10

So why did they report to the anonymous NASA system and not to their airline and the FAA to have the QAR pulled right away and conserve date?

Why do you think they didn't report it to the company?

BobM2

15th Mar 2019, 17:17

Being an airline captain has always required a logical approach to problem solving & a good knowledge of the equipment flown. If on take-off rotation you get an immediate stick shaker, on ONE SIDE ONLY, with the aircraft climbing & accelerating normally, it should be obvious that you have a sensor failure. You're not going anywhere except back to maintenance. There is no reason to clean up the airplane or climb above pattern altitude. Just fly the circuit, make a normal landing & return to the gate. MCAS never gets activated.

Aircraft manufacturers & federal regulators have spent decades trying to make the airplanes "idiot proof". It can't be done. Any revision Boeing does to their software will be a futile attempt to make the airplane "double idiot proof", but maybe it will placate the public.

YRP

15th Mar 2019, 17:22

But Boeing is saying perhaps only 10 days...
https://www.cnbc.com/2019/03/15/boeing-shares-rise-on-report-that-company-will-roll-out-software-upgrade-for-737-max-in-10-days.html

I'm a Software Engineer. Paint me incredulous.

This is not for a fix from scratch. This is what they have been working on since the Lionair crash.

The question is whether it will satisfy the regulators (worldwide not just the FAA now) now that the second accident has happened. It appears clear that any FMEA analysis done originally on the MCAS system has turned out to be inadequate. They'd really need to do another -- very careful, very thorough -- think through of this. Relying on pilots to turn off the system has proven [1] not to be sufficient for sensor failure cases that lead to already potentially confusing/overloading situations for the pilots.

And maybe they've done that.

[1] Ya know, assumin' everything we are all assuming' about the cause turns out to actually be the cause.

Photonic

15th Mar 2019, 18:11

This is not for a fix from scratch. This is what they have been working on since the Lionair crash.

The question is whether it will satisfy the regulators (worldwide not just the FAA now) now that the second accident has happened.

And it's not just satisfying the regulators. Another "partner" in the decision to get the planes back in the air is the flying public at large, who were scrambling to avoid booking flights on the Max just before the grounding. That's why I'm skeptical that this is a fix that will be in place in 10 days. The flying public has to be convinced, and that will only happen if both crashes are shown to be from an identical cause that Boeing is addressing with the update. That's not going to happen in 10 days, I think, unless the investigation is moving at warp speed.

I know the point was made earlier in the thread somewhere, but it's worth repeating that this has some similarity to the EC225's demise in the offshore oil industry. Airbus never managed a good enough explanation and fix for what happened, and the North Sea oil workers refused to fly in them. It was the passengers that effectively killed off the aircraft model. Boeing and the regulators will have to do a better job of clearly explaining the problem, and why the "fix" solves it completely. At least in this case, the probable cause is known, again assuming both crashes were similar enough. If the root cause was different, the situation becomes vastly more difficult for Boeing.