MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

[Fly Aiprt]

Originally Posted by SLF3

the NTSB doesnt buy pilot error. EASA doesn’t buy it either.

Nor do pilot union representatives and many experienced pilots.

[BDAttitude]

I love Muilenbergs statement

It's like in best soviet times. Everything is printed between the lines.

The company is fine-tuning a software upgrade for the Max’s flight-control computers in its simulation lab, girding for the evaluation of a final version by line pilots — all while discussing the timing of the certification flight with U.S. officials. That’s the final hurdle before the Federal Aviation Administration determines whether the flying ban can be lifted, Muilenburg said Monday.

Means :

We would like to make you believe that we made significant progress, but in fact we are still busy iteratively reworking whatever solution we have come up with.
Meanwhile we will increase our public relation efforts. And there is still no timeline for the certification, by the way.

[Grebe]

Originally Posted by BDAttitude

It's like in best soviet times. Everything is printed between the lines.

Means :

IOW Trust but Certify- Safety ( of my bonus for cost savings ) is MY priority

Hell we said the same thing months ago - the rest of the time is we had to dress up our power point presentations, add a few lines of code, tweak and retweak our full motion simulator AFTER kluging our engineering simulator and figure out how to make sure our weakest pilot would never have to use the trim wheel except when parked to set takeoff angle as a function of Gross weight. And making sure our weakest pilot is always crewed with Mr Charles Atlas disciples.

Oh yes - provide lots of travel time to many many FAA grunts to florida with accomodations in disneyland.

[pilotmike]

Originally Posted by jugofpropwash

Am I the only one who thinks that ultimately it would have been safer to leave the MCAS off the planes entirely, and just remind the pilots that stalling the aircraft was possible and to monitor their AOA?

... But there's a HOLE in my bucket, dear liza, dear Liza, THERE'S A HOLE IN MY BUCKET, dear Liza, a HOLE......

Which bit about a failed AOA sensor being right at the heart of the problem has been missed?

[boofhead]

Originally Posted by Tomaski

IMHO, framing some of the crew’s actions as “pilot error” is not particularly helpful. “Error” implies that the pilots’s actions were inconsistent with the training culture and operational expectations to which they were exposed. We have a sense for what Boeing expected the pilots to do in this situation, but there was obviously a gap between their assumptions and reality. Before we get anywhere near suggesting pilot error, I think the following questions should be asked and answered:

• How often and when was the last time these pilots practiced a Runaway Stabilizer event in the sim? Was this accomplished at low altitude? How much exposure did they have using the manual trim wheel?
• How often and when was the last time these pilots practiced an Airspeed Unreliable event in the sim? Was this done during the takeoff phase and did it include an erroneous stick shaker?
• Were the pilots ever taught to associate a bad AOA input with unreliable airspeed and altitude?
• Did any of the pilots’ training involve multiple malfunctions, startle, or distraction?
• What was the automation policy at the pilots’ airline, and did their training and operational culture encourage or discourage hand-flying?
• Did any of their training or experience prepare them for situations in which there was no obvious written procedure available?

To the degree that the pilots reacted in a manner consistent with how they were trained, I think it is inaccurate to file those actions under the label “pilot error.”

I flew most of the Boeings and I certainly was trained on this, I did repeat it in recurrent training and I was always aware of the problems a runaway trim could cause as well as the QRH procedures. This emergency is one of those outlined as an immediate action and all of those actions are mandatory knowledge items that require action without reference to the QRH. I consider that as a minimum responsibility as a PIC. How in Heck do you say that is not true? How do you pass the buck on this? What else is not the pilot's responsibility under your amazing new deal? If the loaders put an extra couple of thousand Kg in the aft hold does that allow the pilot to sit there and let the airplane run off the runway through the trees to grandma's house free of responsibility? If the engine blows up because the mechanic put the wrong nozzles in does the pilot now have your permission to turn the airplane into a pinwheel?

The first rule in any situation is to Fly the Airplane. These crews did not do that. They abandoned their basic responsibilities. Sure it was not all their fault because they were badly trained. The airlines they worked for failed them, as did Boeing who were aware of the low quality training and experience. We all dropped the ball by not objecting to the lowering of pilot skills, not just in Indonesia but at home too (Atlas? Air France?). But ignoring and excusing an obvious problem with pilot skills will lead to more of the same. The airplanes are almost perfect and the number of accidents caused by mechanical failures is dropping but the pilot error factor has not changed. maybe because we won't try to fix it because it is not polite to do so?

If I was running any airline there would be a minimum standard of knowledge and ability required of all the staff, and especially the pilots. Being able to respond correctly to any emergency listed in the QRH would be mandatory. I cannot believe some of the stuff I read here; no real pilot in the real world would come up with it. I may be a dinosaur but I still fly jets and still train pilots and I would never allow this to happen on my watch. I owe that to the people who buy tickets on the airplanes I am responsible for or that I fly.

Tell me that it is OK to reduce the standards. Professionalism is not a requirement for a pilot, especially an airline pilot. Any pilot can do anything he wants no matter the consequences. A pilot is not paid to keep the operation safe; that is always someone else's job. If that is what you believe, say so.

[Fly Aiprt]

Originally Posted by boofhead

The first rule in any situation is to Fly the Airplane. These crews did not do that.

Very well but how can a crew fly the airplane if they are experienceing control troubles preventing them from establishing a correct pitch attitude ?
It is assuming they should have guessed what it took us weeks and thousands of exchanges and documents to determine.

It is sometimes as if what Boeing had assumed was right.
Why still abide by this flawed assumption, when we *know* that no one did even try it in the sim, let alone in flight ?

[fdr]

Originally Posted by boofhead

I flew for several airlines that had a reputation (well deserved) for a high accident rate while flying perfectly serviceable airplanes and it was only after the problem was recognized as pilot error and action was taken to rectify that cause that the accident rates dropped. The point is that it is necessary to identify the root cause no matter how unpalatable it might be and to address it with actions that will reduce the risk. Going after Boeing as if their aircraft was the sole cause of the accidents is not going to help. I mentioned the previous accidents in 1996 that were caused by a loss of static information to the flight instruments for example. Neither of these were failures in the aircraft and both could still be safely flown but hundreds of people died.

80 percent of all accidents are pilot error. These accidents are no different. Burying your head in the sand does not help.

1. That the flightcrew were proximate to the event does not make them the primary cause of the event.
2. Under no stretch of the imagination did the aircraft meet the standards to be certified as presented to the crew.
3. The first event, the crew did not know about the fitment of the defective system, yet you place causation on their shoulders?
4. On the second event, the crew were not provided useable information or training on the weasel words that exist in the FCTM on the operational curiosities of the manual trim.
5. The manual trim as discussed in the FCTM does not by any reasonable stretch of the imagination meet the standards of certification.
6. Post all of the rhetoric, the issue remains a problem for a crew that is alerted to the issue. When simulations conducted with more generous start points than the events and with prior knowledge of the issues, and the fact that the session is going to evaluate the specific problem, when that setup nearly buries in the ground, then it is unreasonable and incorrect to assume that the events come under the all encompassing catch all of pilot error/human error/"80% of all...." for causation.

The design is done by humans, and certification is as well, that is where the problem developed here, and it was exacerbated by assumptions of goodness in the knowledge that the average crew operating the aircraft have.

If the industry does not desire to provide training in the off the wall events such as the manual trim constraints, don't blame the damned messenger who is stuck in the smoking hole and unable to defend themselves. If the industry is happy to put in service deficient designs that don't meet the standards of the day, again, don't blame the messenger.

You and all the other parties that follow this thread and the news on this tragedy have information that should improve your ability to cope with this particular abnormality, hopefully it will also provides some heuristics towards other anomalous conditions that would benefit from similar knowledge, however, nature has a way of reminding us of the limitations of our constructs; blaming the crew as a primary cause is incorrect under any fault analysis such as a W-B, or herringbone or otherwise, and does not cure the problem.

If the crew are the cause, then pray tell why the plane is still grounded, and will be going through what is in effect a full design review not only by the FAA as state of manufacturer regulator, but by almost all other regulators that will have any relationship with the aircraft.

TBC has a continued whiffiness emanating from the head of the fish. The poor schmuck at the design table is the symptom of the problem that had developed there, and the corporate response to this debacle stands in mute testimony of the problems that beset the OEM. Want to be a great corporation again? look in the mirror or listen to what you espouse, and sort your damn act out. Joe Sutter is rolling over in his grave in disgust at the corporate response that is detrimental to the entity.

[Ian W]

Originally Posted by Fly Aiprt

Very well but how can a crew fly the airplane if they are experienceing control troubles preventing them from establishing a correct pitch attitude ?
It is assuming they should have guessed what it took us weeks and thousands of exchanges and documents to determine.

It is sometimes as if what Boeing had assumed was right.
Why still abide by this flawed assumption, when we *know* that no one did even try it in the sim, let alone in flight ?

We do not know that at all. We do know that both Lion Air captains successfully handled the problem. The first actually completed the flight. The second was let down by the first officer who he handed control to.
It is NOT a pilot's fault if you are put into a position that you are not trained for but had the pilots been trained then they could have flown the aircraft back safely that is Boofhead's point.

[OldnGrounded]

Originally Posted by boofhead

I cannot believe some of the stuff I read here; no real pilot in the real world would come up with it.

These forums are full of real pilots and real engineers, from all over the real world, a large majority of whom have been saying the things you can't believe ever since enough information about the MAX crashes emerged to permit informed opinion.

And it's becoming a broken record (<<< old person's expression), but those opinions seem to be shared by the world's real civil aviation authorities.

[fdr]

Originally Posted by safetypee

boofhead - The myth of human error

https://static1.squarespace.com/stat...ech-Report.pdf

http://www.iploca.com/platform/conte...afetyMyths.pdf

http://www.dcabr.org.br/download/eve...-%20Dedale.pdf

jugofpropwash, #2796
Without MCAS the aircraft could not be certificated.

Like in slide 38 it might be possible to operate, although some parts of the operational flight envelope should be avoided - no Mrs, no stabilising MCAS.

S-Pee;

thanks for the links that includes Erik Holnagels work. Erik is one of the leaders in the field of stochastic system behaviour and safety. He established years ago the concept of FRAM, which has altered subtly over the years but still gives a rational view of the world in contrast to the rather simplistic linear or quasi linear models of causation that has underpinned HF/CRM/SMS development of the industry for the last 35 years. The downside of non linear causation is that safety managers have to alter their way of looking at the world, and the limitations of pure compliance has to be comprehended. To take advantage of non linear causation, system observers need to ascertain the extent of variation that exists between their assumption of the system behaviour and what is happening in the real world. That takes rather more care in observation than pure compliance does.

To continue to consider critical processes as simplistic models limits the ability to avoid being in the bandaids on bandaids routine that most management by exception results in. As often as not, our fixes do not work quite as advertised, the current apparent dismay and wailing over apparent erosion of flying skills is an obvious example.

[Fly Aiprt]

Originally Posted by Ian W

We do not know that at all.

I do not concur.
We do know from the NTSB official report, that Boeing did *not* try the MCAS fault in the sim.
They just played "runaway trim".

Some posters here *believe* that they (those posters) could have kept control of the airplane.
Unfortunately, this will remain a conjecture forever.

Meanwhile, the NTSB, CAA agencies worldwide, pilots in the sim, pilot unions and renowned air captains do agree that the situation was very difficult, even knowing what to expect and what to do at what moment.

[Speed of Sound]

Originally Posted by Ian W

It is NOT a pilot's fault if you are put into a position that you are not trained for but had the pilots been trained then they could have flown the aircraft back safely that is Boofhead's point.

The pilots’ abilities in a situation like ET and Li need to be broken down into two distinct parts.

The first is their knowledge, understanding of, and ability to successfully carry out to the runaway trim checklist to a point where trim is restored to normal or near normal enough to safely continue the flight. This is something the pilots need to know although we seem to be in agreement that this is something which has been neglected of late, not least because of the comparative rarity of runaway trim incidents. This is a general training issue.

The second is the ability to diagnose the problem facing them and apply the correct checklist in time to remedy the situation. This is an MCAS specific issue.

Did the accident flights end as they did because the pilots were not able to execute the runaway trim checklist or was it that they left it too late to execute that checklist due to difficulties experienced in working through the problem? Difficulties which continued to beset them even after they had started to apply the correct procedure?

[Grebe]

Joe Sutter is rolling over in his grave in disgust at the corporate response that is detrimental to the entity.

This SLF-retired Boeing engineer with over 30 years agrees- but its not only Joe Sutter.
Bill allen and T .wilson combined with joe are rolling fast enough that throw a coil of wire around them and they could light up Seattle.

There are also a few not yet dead but long ago removed or quit who would never have allowed the corporate BS PR blaming the pilots and /or allowing a single sensor failure to not only seduce fido, but take final control away from the pilot.

Tex Johnson did not die in bed because he was a dumb hot dogger who rolled every model plane he had tested.

[david340r]

Originally Posted by Tobin

I don't think this is correct. There are a lot of posts in various threads to look through, so forgive me for being lazy and not quoting the exact one, but a while ago I did see an explanation like this:

The clutch mechanism is such that even a relatively small opposing force on the trim wheel (such a pilot grabbing the wheel without the handle) will engage the clutch. However, absent any resistance of the wheel, the electric trim motor can drive the jackscrew itself with very high torque and against a high resistance; far more than a human could.

This implies that the mechanism distinguishes between resistance from the wheel versus resistance from the jackscrew, yet still maintains direct correspondence between the wheel and jackscrew motion.

It's not immediately obvious to me how such a mechanism would be designed, but I don't doubt that it is possible to design one given sufficient smarts. Can someone confirm that this is how it actually works on a 737?

I puzzled over this strange two way game of rock/paper/scissors some weeks ago, but I've not been able to find anything conclusive as to how it might actually work. However it's possible to imagine a fairly simple mechanical system that would allow it. For example there could be two discs, one attached to the jackscrew and one to the trim wheels, face to face and with several rollers between them and with a spring pressing them together. In one of the discs there would be grooves that were circular segments that varied in depth, so that they got deeper and then shallower and the rollers would normally sit at the deepest point, but any rotation between the discs would make the rollers run up the slope and push the discs apart, but they would soon hit the end of the groove so they couldn't roll any more and then the two discs would be forced to turn together. The moving apart of the discs would push apart a set of clutch plates/dogs disengaging the electric motor drive. I'm sure there are other ways it could be done.

[MurphyWasRight]

Originally Posted by david340r

I puzzled over this strange two way game of rock/paper/scissors some weeks ago, but I've not been able to find anything conclusive as to how it might actually work. However it's possible to imagine a fairly simple mechanical system that would allow it. For example there could be two discs, one attached to the jackscrew and one to the trim wheels, face to face and with several rollers between them and with a spring pressing them together. In one of the discs there would be grooves that were circular segments that varied in depth, so that they got deeper and then shallower and the rollers would normally sit at the deepest point, but any rotation between the discs would make the rollers run up the slope and push the discs apart, but they would soon hit the end of the groove so they couldn't roll any more and then the two discs would be forced to turn together. The moving apart of the discs would push apart a set of clutch plates/dogs disengaging the electric motor drive. I'm sure there are other ways it could be done.

If I follow that it seems possible, although a bit complicated at least to describe without pictures.

The implementation of the trim wheel overide clutch really does not matter, the point is that there is a mechanism that disconnects the stalled/runaway trim motor when the manual trim wheel is blocked from rotating or rotated against the electric trim. This allows the electric trim to have sufficient torque to move the stab under any conditions yet be overridden by the manual wheel.

Another 'proof of concept' design is detecting tension above a small amount in the manual trim cables, think spring loaded pivoting fan belt tensioner, mechanically 'unclutching' the motor with no electronics/solenoids/etc required.

Friction has very little to do with any this, to help visualize consider a 10 foot balance beam with a bearing at the middle with a 100 pound weight at one end, with a perfect bearing it will take 100 pounds of force to push the other end down, with a 10 pound weight it will take 10 etc.
Even a badly damaged bearing will only increase the force a small amount, the increase will be higher with higher loads but as a percentage will likely be the same or even less.
The 100 pound weight represents the aerloads on the stab.
To reduce the force required to move the 100lb weight shift the pivot closer to the weight, less force but more travel is now needed.

[Lake1952]

THE boofhead has many perfectly valid points about poorly trained front office staff. The first crew LI did not know that there was software code called MCAS that would repeatedly deflect the barndoor sized HS into the airstream driving the nose down. There was a procedure for that, but their lack of prior knowledge that MCAS was even there as well as the multiple spurious alarms and warnings led to an accident. The ET crew should have known about MCAS from the AD that was issued after Indonesia. Yet they still got terribly confused, almost disoriented, allowing their aircraft to accelerate past VNE never reducing thrust. I have heard the excuses for keeping TO thrust... hot, high, and heavy along with stick shaker active etc. It has been repeated to the point of becoming trite in different ways..."fly the plane"... "pitch and power"..." power and attitude" etc. Software will get fixed, but the capability of the flight crew needs to be fixed as well.

[Bend alot]

Bowen said the updated MCAS performs its intended role—automatic horizontal stabilizer nose-down inputs to augment stability in certain high angle-of-attack (AOA) situations—“even better” than the original system.

Very strange statement.

[ARealTimTuffy]

There are plenty of accidents out there that point to the need for improved skills and better training all around.

While it may in fact be the case that these crews were under trained, these are cases much bigger. All pilots have human brains and we are all subject to the same or similar cognitive limitations as these crews. These accidents are a window into how a human pilot (any one of us) process information and makes decisions.

We best pay attention to what they are telling us.

[jack11111]

Before you blame the human and think, "I would do much better", watch this video please.
Most of us know about Three Mile Island, Unit 2. Here's the story behind the story.

You Tube

[Grebe]

Originally Posted by david340r

I puzzled over this strange two way game of rock/paper/scissors some weeks ago, but I've not been able to find anything conclusive as to how it might actually work. However it's possible to imagine a fairly simple mechanical system that would allow it. For example there could be two discs, one attached to the jackscrew and one to the trim wheels, face to face and with several rollers between them and with a spring pressing them together. In one of the discs there would be grooves that were circular segments that varied in depth, so that they got deeper and then shallower and the rollers would normally sit at the deepest point, but any rotation between the discs would make the rollers run up the slope and push the discs apart, but they would soon hit the end of the groove so they couldn't roll any more and then the two discs would be forced to turn together. The moving apart of the discs would push apart a set of clutch plates/dogs disengaging the electric motor drive. I'm sure there are other ways it could be done.

I'll admit I am at a loss as to why several posters insist on trying to redesign or get into nitty gritty details as to friction, clutches, trim wheel load design, etc. It contributes very little to the discussion- especially when it is obvious they dont bother to look for the multi pages-boxes, links of relevant information

So here are a few links for starters which IF time is taken to read and search for further info on the same sites **MAY** help to answer questions or at least provide clues as to where else to look, eventually resulting in part numbers of ' clutches" motors, etc which seem to be the subject of discussion.

https://www.satcom.guru/2019/08/conn...to-action.html


https://www.satcom.guru/2019/05/737-...incidents.html

https://www.satcom.guru/2019/04/stab...and-range.html

https://www.airliners.net/forum/view...?f=5&t=1424319

SEARCH on 737 trim wheel clutch for example

For a clue as to lube issues, etc try the following

https://www.federalregister.gov/docu...-737-airplanes

" We do not agree with the commenter. The intervals and tasks necessary for the lubrication, detailed inspection and overhaul/repair of the HSTA described in Boeing Alert Service Bulletin 737-27A1277, Revision 2, dated January 8, 2010, and proposed in this supplemental NPRM, address the unsafe condition of an undetected failure of the ballscrew primary load path and subsequent wear and failure of the secondary load path for affected airplanes. Due to these factors, we have determined that the desired level of inspection will be achieved when performing an HSTA overhaul. We have made no change to the supplemental NPRM in this regard."

" Inspections, Lubrications, Repairs/Overhauls, and Applicable Corrective Actions

(g) At the applicable compliance time and repeat intervals listed in Tables 1 and 2 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-27A1278, Revision 1, dated January 7, 2010; or Boeing Alert Service Bulletin 737-27A1277, Revision 2, dated January 8, 2010; as applicable (depending on airplane configuration): Do the inspections, lubrications, repairs/overhauls, installation(s), and applicable corrective actions, by accomplishing all the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 737-27A1278, Revision 1, dated January 7, 2010; or Boeing Alert Service Bulletin 737-27A1277, Revision 2, dated January 8, 2010; as applicable; except as provided by paragraphs (g)(1) and (g)(2) of this AD.

https://www.federalregister.gov/d/2011-9410/p-88

https://regulations.justia.com/regul...8/E8-9193.html
" SUMMARY: We propose to adopt a new airworthiness directive (AD) for
certain Boeing Model 737 airplanes. This proposed AD would require
repetitive inspections, lubrications, and repetitive repairs/overhauls
of the ball nut and ballscrew and attachment (Gimbal) fittings for the
trim actuator of the horizontal stabilizer; various installation(s);
and corrective actions if necessary; as applicable. This proposed AD
results from a report of extensive corrosion of a ballscrew used in the
drive mechanism of the horizontal stabilizer trim actuator (HSTA). We
are proposing this AD to prevent an undetected failure of the primary
load path for the ballscrew in the drive mechanism of the HSTA and
subsequent wear and failure of the secondary load path, which could
lead to loss of control of the horizontal stabilizer and consequent
loss of control of the airplane

*****

Note the long up to 25000 hours time for significant rework etc