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

[OldnGrounded]

Just published on WSJ site:

MAX’s Return to Flight Delayed by FAA’s Reevaluation of Safety Procedures for Older 737 Models (https://www.wsj.com/articles/maxs-return-to-flight-delayed-by-faas-reevaluation-of-safety-procedures-for-older-737-models-11558728091)

The agency is considering changes in how pilots are trained to respond when the flight-control computer or other systems erroneously push the plane’s nose down

FORT WORTH, Texas—A review of Boeing Co.’s 737 MAX jets has expanded to include emergency procedures used by pilots on earlier 737 models, further delaying the MAX’s return to service, according to U.S. government officials.

The Federal Aviation Administration hasn’t questioned the safety of older jets currently in service, these officials said, but the broadened review has become a significant factor in adding months to the time expected to get the grounded fleet of 737 MAX jets back in the air.

[hans brinker]

Just published on WSJ site:

MAX’s Return to Flight Delayed by FAA’s Reevaluation of Safety Procedures for Older 737 Models (https://www.wsj.com/articles/maxs-return-to-flight-delayed-by-faas-reevaluation-of-safety-procedures-for-older-737-models-11558728091)

The agency is considering changes in how pilots are trained to respond when the flight-control computer or other systems erroneously push the plane’s nose down

FORT WORTH, Texas—A review of Boeing Co.’s 737 MAX jets has expanded to include emergency procedures used by pilots on earlier 737 models, further delaying the MAX’s return to service, according to U.S. government officials.

The Federal Aviation Administration hasn’t questioned the safety of older jets currently in service, these officials said, but the broadened review has become a significant factor in adding months to the time expected to get the grounded fleet of 737 MAX jets back in the air.

It is about time. There is no difference between the NG and the MAX in manual trim, so if the pilots were unable to manually trim in the last crash, they wouldn't have been able to trim in any of the 6500 B737s flying.

[Loose rivets]

I know it's too late now, but just why is the H-stabilizer not hinged at the front?

It would take a long lever arm to reach the jack-screw, but it is doable within existing confines.

[b1lanc]

It is about time. There is no difference between the NG and the MAX in manual trim, so if the pilots were unable to manually trim in the last crash, they wouldn't have been able to trim in any of the 6500 B737s flying.

So what you are saying is that all pre-Max versions of the 737 are unsafe? I don't think that is what the 'article' is implying. Has there ever been a non-Max 737 crash caused by inability of the crew to trim the horizontal stab?

[kiwi grey]

So what you are saying is that all pre-Max versions of the 737 are unsafe? I don't think that is what the 'article' is implying. Has there ever been a non-Max 737 crash caused by inability of the crew to trim the horizontal stab?

No, only the NGs.
As I understand it:

the manual trim wheels were reduced in size from Classic to NG, making them harder to turn (less mechanical advantage)
the trimmable horizontal stabiliser size was increased from Classic to NG, but the elevators were not proportionally increased, reducing the relative authority of the elevators; and
the information about the 'bunt and wind the trim wheel' trim recovery technique disappeared from documentation and training syllabi for the NG

The Classics were properly certificated as safe, by the standards of the day

[MemberBerry]

About "safe" vs "unsafe", many people like to divide things as "black" or "white", but usually reality consists of shades of gray.

Statistically previous versions are clearly safer. A stabilizer runaway that would bring the aircraft in a situation similar to that of the two crashed MAXes is much less likely in previous versions. That is enough to make them safer even with everything else being equal.

But there is no question that previous versions are susceptible to similar issues when electric trim is inoperable and the aircraft is severely out of trim. It was even documented in the manuals.

[ProPax]

About "safe" vs "unsafe", many people like to divide things as "black" or "white", but usually reality consists of shades of gray.
In fact, ALL people divide safe and unsafe as black and white. Either the manufacturer guarantees that the plane will be safe and pilots in full control till the plane is disembarked at the gate, or it is unsafe. For the same reason the pregnancy test only has two indications. You cannot be "slightly pregnant".

[hans brinker]

So what you are saying is that all pre-Max versions of the 737 are unsafe? I don't think that is what the 'article' is implying. Has there ever been a non-Max 737 crash caused by inability of the crew to trim the horizontal stab?

Just because it hasn’t caused a crash doesn’t mean it’s okay. After the A330/QF72, the Iberia Bilbao crash, the DLH Bilbao incident Airbus changed the programming/procedures to prevent these things from happening again. None of these had any fatalities, but it was enough to change things. Two B737s have crashed, in both the runaway trim part was caused by something new, but it seems likely at least one crew was unable to manually trim the aircraft before they left the envelope. There have been several videos of sim sessions showing just how hard it is to manually trim once you get very AND and high speed. These were in NG sims, and Boeing has just admitted the sims underscore the severity. I think Boeing should at least reconsider the procedure where you always switch both trim switches off, and rewire the max back to the NG way, so pilots have the electric manual trim option without the automatic electric trim.

[yarpos]

" So what you are saying is that all pre-Max versions of the 737 are unsafe? "

So, that was very Cathy Newman

[fdr]

" So what you are saying is that all pre-Max versions of the 737 are unsafe? "

The Max8 MCAS debacle has exposed inadequacies in the certification standards. The NG is different to the Classics, however the MCAS shows that if the aircraft encounters conditions that place it out of trim substantially, then handling that is not being trained, and airspace etc is needed in order to recover. The NG/Max has a greater potential problem due the the design change from the Classic, but none of these aircraft, and likely many other Part 25 aircraft can enter conditions that unloading of the stab could be required, the certification standard does not give protection from all possible conditions, just the level as specified.

[SMT Member]

And yet, Boeing are still telling us the aim is to have the aircraft back in the air by end June, or roughly a month from now. They might twist the arm of the FAA sufficiently to achieve that in the US, but I have serious doubt the grounding will be lifted anywhere else by that time.

[MemberBerry]

In fact, ALL people divide safe and unsafe as black and white. Either the manufacturer guarantees that the plane will be safe and pilots in full control till the plane is disembarked at the gate, or it is unsafe. For the same reason the pregnancy test only has two indications. You cannot be "slightly pregnant".

I disagree. Safe/safer/safest. You can clearly compare safety levels, so safety is a continuum. I could even argue that this continuum is multidimensional, but for simplicity let's assume it's unidimensional.

In any case, you can't guarantee with 100% certainty that "the plane will be safe and pilots in full control till the plane is disembarked at the gate". At most you could guarantee that, statistically, 99.9999999% of the time it will happen.

But, indeed, while subjective, as demonstrated by the FAA being the last to ground the MAX, there are two distinct conditions: either the aircraft should be allowed to fly, or it should not. Meaning that it's either "safe enough to fly", or "not safe enough to fly". From a legal point of view that would be called "airworthy" vs "not airworthy".

According to Wikipedia:


Airworthiness is defined in JSP553 Military Airworthiness Regulations (2006) Edition 1 Change 5 as:

The ability of an aircraft or other airborne equipment or system to operate without significant hazard to aircrew, ground crew, passengers (where relevant) or to the general public over which such airborne systems are flown

This definition applies equally to civil and military aircraft. However, military aviation despite being governed by regulations, this is performed in a less standardized and more fragmented way as compared to civil aviation.

An example of a method used to delineate "significant hazard" is a risk reduction technique used by the military and used widely throughout engineering known as ALARP (As Low As Reasonably Practicable). This is defined as:

‘The principle, used in the application of the Health and Safety at Work Act, that safety should be improved beyond the baseline criteria so far as is reasonably practicable. A risk is ALARP when it has been demonstrated that the cost of any further Risk reduction, where cost includes the loss of capability as well as financial or other resource costs, is grossly disproportionate to the benefit obtained from that Risk reduction.’


The key point is "without significant hazard". You can't completely eliminate risks. The only question is if the risks are acceptable or unacceptable, in relation to the cost of reducing them further.

Anyway, that's enough semantics for me. And no, I don't even want to open the pregnancy can of worms.

[b1lanc]

There have been several videos of sim sessions showing just how hard it is to manually trim once you get very AND and high speed. These were in NG sims, and Boeing has just admitted the sims underscore the severity. I think Boeing should at least reconsider the procedure where you always switch both trim switches off, and rewire the max back to the NG way, so pilots have the electric manual trim option without the automatic electric trim.

I've seen the videos and manual trim on the NG is just about impossible at higher speeds. But there is a subsequent procedure to unload the force on the stab to allow pilots to regain the ability to manually trim and allow some elevator authority (assuming sufficient altitude and trim isn't jammed). I agree with the last sentence, however. That change was not well thought out.

[b1lanc]

And yet, Boeing are still telling us the aim is to have the aircraft back in the air by end June, or roughly a month from now. They might twist the arm of the FAA sufficiently to achieve that in the US, but I have serious doubt the grounding will be lifted anywhere else by that time.

Hard to believe that will happen given that United for one just cancelled their Max flights into August. Also, 150 hour per Max for a fix seems like more than a software upgrade.

[LowObservable]

Safety, for the passenger, is always relative and a matter of perception. I have been regular SLF since 1974, in which year there were 11 major losses including the THY Paris crash, the first 747 loss, two Pan Am 707s and a TWA bombing. To take a SWAG, with today's traffic and aircraft sizes, such a mishap rate would see a crash every week with an average of ~200 fatalities.

That's been the result of both improved engineering, better training in sims, and better understanding of flying practices (CRM), among other things.

As for perception: I believe the passenger expects the flight to be safe. I'm estimating that most people in the flying public have never lost a family member or an acquaintance in a public-transport aviation mishap. They may not be consciously aware of how much safety has improved (perhaps because of the prominence given to protection against terrorist attack), but it would be unwise at this point to underestimate the impact of the MAX accidents: two closely related accidents, with large loss of life, hitting the same aircraft type within months of its introduction.

[Chas2019]

Just published on WSJ site:

MAX’s Return to Flight Delayed by FAA’s Reevaluation of Safety Procedures for Older 737 Models (https://www.wsj.com/articles/maxs-return-to-flight-delayed-by-faas-reevaluation-of-safety-procedures-for-older-737-models-11558728091)

The agency is considering changes in how pilots are trained to respond when the flight-control computer or other systems erroneously push the plane’s nose down

FORT WORTH, Texas—A review of Boeing Co.’s 737 MAX jets has expanded to include emergency procedures used by pilots on earlier 737 models, further delaying the MAX’s return to service, according to U.S. government officials.

The Federal Aviation Administration hasn’t questioned the safety of older jets currently in service, these officials said, but the broadened review has become a significant factor in adding months to the time expected to get the grounded fleet of 737 MAX jets back in the air.

if that is what it takes to prevent future crashes then it is justified.

[capngrog]

In fact, ALL people divide safe and unsafe as black and white. Either the manufacturer guarantees that the plane will be safe and pilots in full control till the plane is disembarked at the gate, or it is unsafe. For the same reason the pregnancy test only has two indications. You cannot be "slightly pregnant".

I agree that most people use the terms "safe" and "unsafe"; however, there is no such thing as "safe". "Safety" is a concept of relativity. There will always be risk in every human endeavor, ranging from "slight risk" to "severe risk", and the real world deals with risk management, not attempts to achieve absolute safety ... whatever that is. For example, walking is a relatively safe activity given normal circumstances; yet, walking on the edge of an icy precipice in a snowstorm involves more risk, requiring more caution ... hence "risk management". I could go on and on about this, but I won't.

This is just my opinion; but that opinion is based on 43 years of safety related work and accident investigation.

Cheers,
Grog

[GlobalNav]

The Max8 MCAS debacle has exposed inadequacies in the certification standards. The NG is different to the Classics, however the MCAS shows that if the aircraft encounters conditions that place it out of trim substantially, then handling that is not being trained, and airspace etc is needed in order to recover. The NG/Max has a greater potential problem due the the design change from the Classic, but none of these aircraft, and likely many other Part 25 aircraft can enter conditions that unloading of the stab could be required, the certification standard does not give protection from all possible conditions, just the level as specified.
How can you be sure the standards are inadequate? I think it’s more likely the process of delegation and signing off on compliance. If exiting standards had been complied with, this would not have happened.

[yellowtriumph]

In fact, ALL people divide safe and unsafe as black and white. Either the manufacturer guarantees that the plane will be safe and pilots in full control till the plane is disembarked at the gate, or it is unsafe. For the same reason the pregnancy test only has two indications. You cannot be "slightly pregnant".


Point of order Mr Chairman:

https://www.rottentomatoes.com/m/a_slightly_pregnant_man

Not serious and I will now bow out again.

[OldnGrounded]

I've seen the videos and manual trim on the NG is just about impossible at higher speeds. But there is a subsequent procedure to unload the force on the stab to allow pilots to regain the ability to manually trim and allow some elevator authority (assuming sufficient altitude and trim isn't jammed).

Emphasis added.

Right, and the videos and reports from the sim episodes suggest that "sufficient altitude" may well be 8K feet in addition to whatever else you may need. The porpoising maneuver seems very much like a Hail Mary play, at least in many of the circumstances in which it might be seen as necessary.

[ProPax]

I disagree. Safe/safer/safest. You can clearly compare safety levels, so safety is a continuum. I could even argue that this continuum is multidimensional, but for simplicity let's assume it's unidimensional.
From where I am sitting (1A, please) safety is not a continuum. It's not even a line. It's a dot where all those lines cross. What you're saying does make sense, but only as politics. Or, God forbid, policy. The law cannot scope all possible variables, of which aviation has a lot. But as long as safety is the priority for all parties involved, it's a very small dot in the universe.
If the engineer is absolutely sure he's done everything in his power and to his knowledge to make the plane safe, there is no continuum for him. He may have missed something that is impossible to check or even unknown (who knew you can't fly next to a volcano before BA9), and it very well may be the deciding factor in disembarking at the gate, but he should be sure he's done his part. The pilot must be sure he has full control of the aircraft and its systems. There should be no surprises for him, and he must have enough time to react to variables, be it a memory recall or an FCOM expedition. And for the passenger safety is an even smaller dot - will I be alive after the plane comes to a stop on the ground?

Everything else, the laws, the standards, the policies, is just politics, or worse, semantics. Bottom line that I hope everyone here agrees - if a plane is too expensive to be made safe, it mustn't fly.

[ProPax]

For example, walking is a relatively safe activity given normal circumstances; yet, walking on the edge of an icy precipice in a snowstorm involves more risk, requiring more caution ... hence "risk management". I could go on and on about this, but I won't.
Agreed. However in this particular case, you are walking on the edge of an icy precipice in a snowstorm while the weather forecast says sunshine and issues no warning about the precipice or it being icy. And you are pulling a sled with 200 people who rely on you to get them home safely. And the CEO of the weather forecast says it's absolutely safe because the Weather Supervisor allowed him to do that.

In you 43 years of safety investigations haven't you come to the conclusion that safety cannot exist if the people who are supposed to observe a system's safety don't understand the system or don't know it exists?

[safetypee]

Way back, ‘Reevaluation of 737 Safety Procedures’,
at # 2, ‘There is no difference between the NG and the MAX in manual trim,….’
Technically - mechanically the trim system could be identical, but the installation and use, redefined by aircraft characteristics, new variants, could result in small changes which in specific circumstances are critical in safe operation.

As discussed in this thread, these changes may not be clear cut and have evolved through each generation of aircraft development. Also https://www.pprune.org/10479475-post105.html for some of the changes.

A key issue in safety is learning. Revisiting previous beliefs and assumptions after an accident is an important safety process - safety involves what is done opposed to a stagnant what we have.
A difficulty in reassessment is in identifying what the original beliefs and assumptions were, especially in design and certification as they may not be overtly recorded, being the conclusions of judgements about human - system interaction and human performance.

[safetypee]

A clear summary of the current situation.
A disturbing view of the NG and imminent future of the MAX.
https://www.moonofalabama.org/2019/05/boeing-737-max-crash-reveals-a-severe-problem-with-older-boeing-737-ngs.html

[SLF3]

Despite the quirky website address the moonofalabama article is both interesting and well written. Hard to argue the 737 NG is not 'safe' given it's track record, but Boeing (and the FAA) will struggle to explain how they got to this place: 'We made the stabiliser bigger, which increased the loads it could generate, and made the trim wheel smaller, so it was harder to turn. And then deleted the procedure that told you how to use the trim wheel at high loads.'

[FRogge]

Since I don't have any experience on other jetliners than the 737, can someone explain how trim runaways are sorted out on aircrafts that doesn't have a trim wheel at all. Personally I think that trim runaways happens so rarely, that once it's eliminated that MCAS can't trim full nose down anymore, I would not be to worried anymore to get on a MAX plane.

[SteinarN]

Since I don't have any experience on other jetliners than the 737, can someone explain how trim runaways are sorted out on aircrafts that doesn't have a trim wheel at all. Personally I think that trim runaways happens so rarely, that once it's eliminated that MCAS can't trim full nose down anymore, I would not be to worried anymore to get on a MAX plane.

FBW planes like A320 and newer and B777 and newer have much more redundancy like several FCC with several channels each continuously comparing their output with each other, possibly more than one motor driving the jack screw, more than one signal path to the motors etc. In sum this makes it exceedingly unlikely that a runaway can happen. Think at how unlikely it is to loose both engines over water far from nearest airport on a two engine aircraft. It is not guaranteed it can never happen, but the likelyhood of it happening is so exceedingly small that the risk is deemed acceptable.

Edit: On FBW aircraft like the A320 there is no significant force required to hold say full aft stick, so less physically demanding compared to the B737 where a pilot might need to use all his force just to hold against a badly mistrimmed stabilizer. Further the elevator on say the A320 is much larger as a percentage of the stabilizer so the elevator has significantly more authority to hold against a badly mistrimmed stabilizer. In sum all these differences make the B737 much more demanding to controll when the stabilizer get significantly out of trim, and the likelyhood of it running away is probably also much larger.

[Luc Lion]

FRogge, you then might find that the following runaway incident report is interesting.
It's a FBW airplane, of course.
Ultimately, the cause is linked to an incorrect safety risk assessment (again).

One of the manufacturer's responses was to put a button that disconnects the automation.

https://www.bea.aero/uploads/tx_elydbrapports/hb-n110525.en_01.pdf

[Smythe]

Personally I think that trim runaways happens so rarely, that once it's eliminated that MCAS can't trim full nose down anymore, I would not be to worried anymore to get on a MAX plane.

MCAS is not runaway stab. MCAS kicks in under certain conditions, MCAS was a solution for those conditions, and those conditions remain to be dealt with.

Currently, the ac has 2 sensors, one of which is used for STS and MCAS. The results a faulty or damaged AoA sensor initiated MCAS.
On the NG, the stab switches could cutoff AP and Elec stab control separately. Currently, the MAX stab switches cut off the electric stab control entirely, leaving the crew to manually trim the aircraft.
Given that it appears that in both cases, the AoA was damaged, it looks like the crew will be manually trimming the ac for the rest of the flight. That is not realistic.
Adding an AoA disagree light, so what? Changing the switches back to NG config...okay, then again, if one AoA is gone or damaged....
Adding a 3rd AoA vane, damn near impossible.
The underlying reasons and conditions MCAS was added in first place.

While it doesnt happen that often (until MCAS) when it did, it exposed the issues with the MAX AND the NG...
The "roller coaster" hasnt been in the manual since the -200 with a different stab/elev config.
Extending flying on manual trim with no AoA or limited, yet another lost art?

All adds up to a real big mess that a "software fix" is but a small part.

[Judd]

The "roller coaster" hasn't been in the manual since the -200 with a different stab/elev config

That is true. But the roller coaster method of regaining partial manual stabilizer control certainly is effective in the Boeing 737 Classic simulators despite nothing in the FCTM that specifically states how it is done. It is alluded to by the FCTM statement "In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming" The roller coaster method is designed to do just that.

[capngrog]

In you 43 years of safety investigations haven't you come to the conclusion that safety cannot exist if the people who are supposed to observe a system's safety don't understand the system or don't know it exists?

Accident investigators must understand all factors involved in an accident, and reaching that understanding is the point of the investigation. Accident investigators begin the process from a point of relative ignorance and, must maintain a rather steep learning curve, hopefully resulting in an understanding of the circumstances/factors of the accident. These circumstances/factors range primarily from hardware, to software, to the human element and many others; however, nobody is expert or even conversant in the intricacies of all aspects of modern technology, hence such procedures as the "Party to the Investigation" system utilized by the NTSB (USA) and others. The "Party" system employed by the NTSB, for example, relies heavily upon outside expertise, and the NTSB Investigators themselves have their specialties such as "Power Plant", Weather", "Structures", "ATC" etc. As you suggested in your above statement, to reach an understanding of complex factors in an investigation, requires the input of many competent individuals.

Cheers,
Grog

[cessnapete]

Accident investigators must understand all factors involved in an accident, and reaching that understanding is the point of the investigation. Accident investigators begin the process from a point of relative ignorance and, must maintain a rather steep learning curve, hopefully resulting in an understanding of the circumstances/factors of the accident. These circumstances/factors range primarily from hardware, to software, to the human element and many others; however, nobody is expert or even conversant in the intricacies of all aspects of modern technology, hence such procedures as the "Party to the Investigation" system utilized by the NTSB (USA) and others. The "Party" system employed by the NTSB, for example, relies heavily upon outside expertise, and the NTSB Investigators themselves have their specialties such as "Power Plant", Weather", "Structures", "ATC" etc. As you suggested in your above statement, to reach an understanding of complex factors in an investigation, requires the input of many competent individuals.

Cheers,
Grog

I'm sure I read in an initial report of the Ethiopian accident, the crew left/forgot to reduce power after takeoff. Whatever any MCAS problems, leaving full power on until you make a hole in the ground is not good practice?

[Fly Aiprt]

the crew left/forgot to reduce power after takeoff. Whatever any MCAS problems, leaving full power on until you make a hole in the ground is not good practice?

One must remember that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.
So there is nothing wrong with leaving full thrust with a stickshaker alarm at takeoff.

Duly warned and briefed pilots experienced great difficulties in the sim when confronted with the same scenario.
Even though nothing was at stakes, they say they had their hands full with dealing with the recovery and fighting tunnel vision.

What with a real unexpected alarm in a real aiplane with no previous briefing ?
And remember, the "certified" 737 was supposed to be hand trimmable at the time.

Only now do we know Boeing "autocertified" their airplanes, and there are suspicions of trim difficulties on the MAX as well as the NG.

[MurphyWasRight]

One must remember that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.
So there is nothing wrong with leaving full thrust with a stickshaker alarm at takeoff.

Duly warned and briefed pilots experienced great difficulties in the sim when confronted with the same scenario.
Even though nothing was at stakes, they say they had their hands full with dealing with the recovery and fighting tunnel vision.

What with a real unexpected alarm in a real aiplane with no previous briefing ?
And remember, the "certified" 737 was supposed to be hand trimmable at the time.

Only now do we know Boeing "autocertified" their airplanes, and there are suspicions of trim difficulties on the MAX as well as the NG.

Totally aggree with above, while leaveing power up was not ideal it was not a cause of inability to trim, snip from a post in other thread:

Known facts from, report.
Airspeed at start of first MCAS input 250 kts.
MCAS applied 9 seconds ND trim the ET pilot applied 3 seconds NU trim 6 seconds later.
MCAS acitvated 5 seconds after that but was interrupted at 6 seconds by 9 seconds NU trim. (possibly interrupted by trim cutout)

Total MCAS 15 seconds ND total pilot NU 12 seconds left the aircraft severely out of trim and just under VMO in under 40 seconds and likely unrecoverable using manual/mechanical trim.

[RVF750]

Remember the trim works at two speeds too. The pilots can command a slow speed trim with flaps up and fast with flaps not up. MCAS works at fast speed I believe? 9 seconds at full speed and 3 seconds back at half speed wouldn't end well....

[Fortissimo]

Hard to argue the 737 NG is not 'safe' given it's track record

This was exactly the argument used for the Nimrod MR2 until 14 aircrew were killed by a latent airworthiness problem that had not manifested to the point where it had been recognised in the previous 25 years. (Yes, the number of aircraft and hours flown were a couple of orders of magnitude different but it's the same logic.) As ever, it's the combination of unforeseen circumstances that are the killer but if the manufacturer had foreseen and ignored, you have a very different equation.

[groundbum]

there's still the issue if MCAS is disabled under certain circumstances. how can the MAX meet the certification requirement about consistently increasing forces on the Yoke as the aircraft approaches a stall, which seems a very desirable attribute!

And the liability/fraud issue about the Boeing paperwork that stated MCAS authority would be limited to 0.4 units, thus justifying much less scrutiny and code that wasn't level 1, then actually allowing it 2.5 units of authority? It would be even worse if it was found that B deliberately wrote in 0.4 to get it passed under the radar whilst knowing/having a good guess it would need much much more in actual use. That counts as gaming the regulator.

G

[Smythe]

That is true. But the roller coaster method of regaining partial manual stabilizer control certainly is effective in the Boeing 737 Classic simulators despite nothing in the FCTM that specifically states how it is done.

Of course, in the classic.

The NG has a larger stab, and a smaller elevator....

What is the procedure for this configuration?

It appears the FAA has finally caught up, and well,

the lazy B has been caught.

In reality, I am far over this ****. The aircraft industry is held back by all of the bull**** regulations, that when you read them, are so old, dont relate, or are so vague to be unusable.
New designs and technology are hampered by attempts to fit into 1950s capabilities, (or abused by compliance)

If you want to let the aviation business really soar, fix the regulatory process to allow technology to expand as a NEW FN system, rather than a legacy bull**** system. FK the " its the same and no new training is required or type" It is not....

I would much rather be trained on a new fightdeck capabilities, and the intricacies of the AP, than they tell me it is the same as a -700 or -800, FK an iPAD and I am cert'd, and expect me to react when the FN nose points down......

I WANT to know the differences, I WANT to know when the **** hits the fan, what I need to do about it. This bull**** about hand flying the aircraft, is becoming just that, bull****.
The MTOW and thrust alone between these variants should tell someone with "experience' that it just doesnt work that way anymore...

[RickNRoll]

Despite the quirky website address the moonofalabama article is both interesting and well written. Hard to argue the 737 NG is not 'safe' given it's track record, but Boeing (and the FAA) will struggle to explain how they got to this place: 'We made the stabiliser bigger, which increased the loads it could generate, and made the trim wheel smaller, so it was harder to turn. And then deleted the procedure that told you how to use the trim wheel at high loads.'

They also put a damper in there as well because there was also a new trim motor.



Regarding the trim wheels: When the NG was being introduced, I happened to be the Lead Engineer in charge of them and a whole lot of other stuff. There were some issues. The new display system created a pinch point between the dash and the wheel. We had to make the wheel smaller. And the new trim motor resulted in the wheel, which is directly connected to the stabilizer by a long cable, springing back when electric trim was used. It was an undamped mass on the end of a spring. We had to add a damper.
Result: Depending on the flight conditions, the force to manually trim can be extremely high. We set up a test rig and a very fit female pilot could barely move it.



International Skeptics Forum - View Single Post - [Ed] 737 Max Crashes (was Shutdown caused Boeing crash.) (http://www.internationalskeptics.com/forums/showpost.php?p=12651539&postcount=143)

[DaveReidUK]

The NG has a larger stab, and a smaller elevator...

The elevator has stayed the same size on every 737 variant as the size of the stab gradually grew.

[Icarus2001]

In fact, ALL people divide safe and unsafe as black and white. How ridiculous.

Is flying in an aircraft "safe"?

Is driving a car "safe"?

These are not absolutes.

[cessnapete]

One must remember that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.
So there is nothing wrong with leaving full thrust with a stickshaker alarm at takeoff.

Duly warned and briefed pilots experienced great difficulties in the sim when confronted with the same scenario.
Even though nothing was at stakes, they say they had their hands full with dealing with the recovery and fighting tunnel vision.

What with a real unexpected alarm in a real aiplane with no previous briefing ?
And remember, the "certified" 737 was supposed to be hand trimmable at the time.

Only now do we know Boeing "autocertified" their airplanes, and there are suspicions of trim difficulties on the MAX as well as the NG.

“Nothing wrong with leaving full power on”. Why would a competent crew ever do that? With speed whistling through 250/300 kts you are obviously not stalling. ( easily confirmed by GS readout). Reduce power, pitch and power ( covered in your Type Rating) if ASI indications unreliable. Partial flap as required, no automatics due erroneous Stick Shaker, and manually fly a return circuit to land.

[Zeffy]

https://www.wsj.com/articles/boeing-737-max-could-stay-grounded-for-at-least-two-months-trade-group-says-11559117714


Boeing 737 MAX Could Stay Grounded for at Least Two Months, Trade Group Says
IATA boss says the impact of the global suspension of MAX flights on airlines has been significant

By Robert Wall and Na-young Kim
May 29, 2019 4:15 a.m. ET
The boss of the airline industry’s largest trade group Wednesday said the Boeing BA -0.01% 737 MAX fleet could remain grounded for another two months or more in the wake of two crashes.

IATA Director General Alexandre de Juniac said the timing on the MAX’s return to service was up to regulators, but airlines were bracing for 10 to 12 more weeks of delay before the plane can resume commercial service.

The U.S. Federal Aviation Administration last week hosted foreign regulators to discuss the process of clearing the MAX to commercial service after the grounding that followed the March 10 crash of one of the planes in Ethiopia. It was the second MAX crash in less than five months.

“We have to maintain an alignment between those authorities. Hopefully an alignment in terms of schedule,” Mr. de Juniac told reporters.

Boeing has been working on a fix to the flight-control flaw implicated in both crashes, but hasn’t submitted the formal submission to the FAA as it responds to questions from regulators.

He said the impact of the grounding on airlines was significant, though IATA doesn’t yet have a figure for the financial hit from canceled flights, higher costs and lower sales. If the plane remains grounded for another three months, it would hit airlines for the bulk of their summer flying, the busiest travel period for most MAX operators.

Mr. de Juniac said it was unfortunate that the FAA meeting last week didn’t spell out a timeline for the MAX’s return to flight. IATA on the same day held a meeting of 23 airlines that have the MAX in their fleet or on order. Boeing and the FAA provided information to the carriers at the event. Mr. de Juniac said carriers are hopeful that regulators will “find a reasonable time frame” to safely return the MAX to the sky.

Mr. de Juniac said a meeting between airlines, Boeing and regulators is likely to be held in five to seven weeks to prepare for a smooth MAX return to service. “We need to restore confidence in our industry,” he said, both related to the MAX and the certification process for planes more widely.

IATA members are gathering for their annual meeting, which starts Sunday, against a backdrop of global trade tensions and uncertainty over Britain’s exit from the European Union, which have dented demand for air travel.

Air freight demand in April fell 4.7% compared with a year earlier, continuing a slump in demand that began in January, IATA said.

The Trump administration this summer plans to impose higher tariffs on numerous goods made in China, denting freight demand. The airline industry is only one of several to feel the sting. Danish shipping giant A.P. Moeller-Maersk AS last week reported a first-quarter loss and warned that rising trade tensions between the U.S. and China could cut container growth by up to a third this year.

Write to Robert Wall at [email protected]

[fdr]

One must remember that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.

unfortunately, that is not quite correct. There is an assumption that the crews can cope with an out of trim case at all times, e.g., there is always sufficient authority of the elevator to cope with an out of trim stabiliser, but reality is that is not what the rules actually require. The protection of the certification standard gives a partial coverage for out of trim conditions, of a 3 second error only in the trim at all speeds within the normal envelope effectively. That is sorely tested by the MCAS system, and even without it, there could easily be conditions where you can alter the thrust enough that an additional 3 second of error in trim can place you outside of normal protections under the certification standard. [think of the A310's, the A320 @ Perpignan etc, and other wildly out of trim from thrust/trim mismatches].

The B737 is not alone in being able to be put into a severe out of trim case, but the fact that a condition can arise where the trim cannot function at all as a result of the error is a serious lack of certification shortfall in the protections provided by certification. The only part of the regs that the MCAS appears to be actually non compliant with is related to stability augmentation systems. The trim case it may well have been compliant, the rules themselves were deficient in this case, and appear to be in any case where a condition may arise where the stabiliser can only be returned to function by undergoing special procedures that were not generally taught or discussed, could require a breach of the single crew on the controls policy, and would exceed the control input force requirement of certification. That latter item is a possible breach.

The OEM and the industry have had an expensive lesson on the real world behaviour of the worlds favourite jet transport, and as always the industry will learn from the wreckage and reinforce rules as a result. This particular deficiency is going to be more than a minor matter, personally, I would think that there is some serious issues raised in how to ensure trim is always able to be controlled. watch out for some T tabs on elevator TE in the near future etc... Perhaps nothing gets fixed.

[RobertP]

JSP 553 is not the only definitive statement regarding aeronautical products and reflects the USA Military and CFR14 FAR interpretations. This is a good definition, however Nations signatory to the ICAO Convention and in particular Annex 8 have jurisdiction concerning the interpretation and this is reflected in the National Regulatory Organisational standards. Whilst acceptance of Aeronautical Product certification standards between many but not all nations is to date convention this MAX 8 situation indicates that this may not hold true for the future. EASA have made it quite clear that automatic acceptance of FAA MAX 8 changes will not happen. This may have implications wrt the ICAO Convention not least as it also may affect Annex 13 and its interpretation.

[Fly Aiprt]

“Nothing wrong with leaving full power on”. Why would a competent crew ever do that? With speed whistling through 250/300 kts you are obviously not stalling. ( easily confirmed by GS readout). Reduce power, pitch and power ( covered in your Type Rating) if ASI indications unreliable. Partial flap as required, no automatics due erroneous Stick Shaker, and manually fly a return circuit to land.

Of course, in an armchair flight, no problem doing what has been discussed here for weeks. It is all too easy to pick just one part of the event and in the light of hindsight, choose the relevant C/L, which we now know would solve the problem.
Now, in the real airplane at takeoff, why would a crew reduce thrust while battling with a persistent stickshaker (it makes noise, no whistling sound) and lots of most distracting alarms, instead of climbing away to sort things out ?
Even just in a sim, warned and briefed crews had their hands full doing the correct thing, which implied resorting to the roller-coaster maneuver.
And just got away by a small margin that the real crew in the real event didn't have.

And BTW, it appears that no flight sim to date reflects the real airplane...
So...I must admit that I'd not be so affirmative...

[Fly Aiprt]

that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.


unfortunately, that is not quite correct. There is an assumption that the crews can cope with an out of trim case at all times, e.g., there is always sufficient authority of the elevator to cope with an out of trim stabiliser, but reality is that is not what the rules actually require. The protection of the certification standard gives a partial coverage for out of trim conditions, of a 3 second error only in the trim at all speeds within the normal envelope effectively.

Point taken.
Was meaning "the trim was supposed to be moveable"...

[safetypee]

fdr #44,
Interesting views, no disagreement.

‘This particular deficiency is going to be more than a minor matter …’
It might be premature to discuss specific solutions for a deficiency which as yet is not clearly understood (at least publicly).
Elevator effectiveness, yes; but also in normal operation consider the combined horizontal tail surfaces - trim drag. What do you imply with TE tabs; corrective effect must overcome the failed trim condition, but not detract from normal operation.

Alternative thoughts could question why it was necessary to increase the tail area, yet retain the same size elevator. More trim range required whilst the pitch control appeared to be adequate.
The obvious longer, heavier, cg, arguments apply, but pitching moment with varying thrust levels could add another dimension.
Another question is why the trim range was chosen (horiz stab angles), is this relatively large, what are the limiting aerodynamic conditions; high, low speed, configuration, cg, thrust.
Have these changed with the evolving variants.

Background ref; https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html

[ProPax]

IATA Director General Alexandre de Juniac said the timing on the MAX’s return to service was up to regulators, but airlines were bracing for 10 to 12 more weeks of delay before the plane can resume commercial service.

“We have to maintain an alignment between those authorities. Hopefully an alignment in terms of schedule,” Mr. de Juniac told reporters.

Mr. de Juniac said it was unfortunate that the FAA meeting last week didn’t spell out a timeline for the MAX’s return to flight.

Mr. de Juniac said a meeting between airlines, Boeing and regulators is likely to be held in five to seven weeks to prepare for a smooth MAX return to service. “We need to restore confidence in our industry,” he said, both related to the MAX and the certification process for planes more widely.
So, correct me if I'm wrong here. The "decadent capitalist pig", the "Pentagon puppet", the "Trump man" Daniel Elwell says that 737MAX investigation "will be driven by safety and not by schedule". Whereas the French socialist who went to the same school as the recent French president Francois Hollande, a school where Jean-Paul Sartre, no less, was a teacher once, says that MAX investigation should reach an "allignment" (whatever that is) "in terms of schedule" because - OMG!!! - summer schedule is in danger.

And he thinks rushing an investigation of this magnitude and "alligning" it to a schedule will "restore confidence in [his] industry"?!

I think, IATA needs a new CEO.

[Fly Aiprt]

Daniel Elwell says that 737MAX investigation "will be driven by safety and not by schedule". Whereas the French socialist who went to the same school as the recent French president Francois Hollande, a school where Jean-Paul Sartre, no less, was a teacher once, says that MAX investigation should reach an "allignment" (whatever that is) "in terms of schedule" because - OMG!!! - summer schedule is in danger.

And he thinks rushing an investigation of this magnitude and "alligning" it to a schedule will "restore confidence in [his] industry"?!

That's wishful talk.
Didn't it occur to you that both may be wrong^^?


I think, IATA needs a new CEO.

What's IATA to do ? There's no fault on the part of IATA. They bought aircraft, confident that they would be up to modern standards, and actually certified by a real, up to the task, aviation agency.

[ProPax]

What's IATA to do?
That's actually a very good question. What do they usually do? ICAO issues and enforces the rules of international aviation, such as the freedoms of airspace. But what does IATA do? I'm seriously asking this question. I have NO idea. I'm sure there is an article in Wikipedia that will give me the official blurb, but what actual function do they perform, does anyone know? I honestly have never heard anything about IATA actions, good or bad, but then again, I may have not been paying attention.

[n5296s]

What do they usually do?
I'm pretty sure they assign the three-letter airport identifiers. No idea what else they do.

[c52]

I'm afraid that reading the Wikipedia article will not enlighten you.

[DaveReidUK]

But what does IATA do? I'm seriously asking this question. I have NO idea. I'm sure there is an article in Wikipedia that will give me the official blurb, but what actual function do they perform, does anyone know?

Almost every industry has a trade association. Most of those carry out the functions that you would expect from such an organisation. IATA is the airline industry's trade association.

[wheelsright]

Certification is a binary process denoting an acceptable level of risk. Safety or risk is inherently not binary but is subject to the exercise of judgment to arrive at a compromise that can be certified. Not sure what the pregnancy argument is about but clearly no system is absolutely safe but when you are pregnant you are absolutely.

MCAS is popularly considered to have introduced an unnecessary level of risk that should not have been certified. It is probable that the aircraft would have been safer without MCAS and the pilots were responsible for potential pitch up conditions due to the new engine locations. The investigation will have to resolve these suppositions and whether there were fundamental irregularities with the design and certification process. Quite rightly the focus must be on whether the design and certification was appropriate. Consideration of pilot performance are of course relevant, but are not the primary cause of the accidents and are not capable of obvious remedial action. There will always be pilots of varying ability. It is far from certain that the situation that they found themselves would have been recoverable by average pilots... more information is required to establish what the pilots actually did at all stages of the flights.

Based on the limited information, it appears to me that MCAS introduced an unacceptable level of risk and those risks were known to Boeing and possibly the FAA. It is not a good situation for public confidence in safety.

[PAX_Britannica]

It is about time. There is no difference between the NG and the MAX in manual trim, so if the pilots were unable to manually trim in the last crash, they wouldn't have been able to trim in any of the 6500 B737s flying.

Umm, apologies if I've misunderstood what you're saying, but...

The entire point of the introduction of MCAS is that the 737 MAX without MCAS responds to pitch control inputs differently to earlier models. In particular, runaway pitch-up is possible.

Without MCAS, the 737MAX would fail to meet FAR 25 requirements for controllability in manual flight.

In another thread (https://www.pprune.org/showthread.php?p=10336645)
I like "25.203 Stall characteristics", as it may provide a clue why MCAS was incorporated. The first paragraph requires:
No abnormal nose-up pitching may occur. The longitudinal control force must be positive up
to and throughout the stall.

[neville_nobody]

It is probable that the aircraft would have been safer without MCAS and the pilots were responsible for potential pitch up conditions due to the new engine locations.

Whilst in hindsight that is probably true, MCAS came about because the MAX didn't actually meet the certification standard in the first place. It would be interesting to know how far off the certification standard they were that Boeing believe it necessary to actually put in the MCAS system.

[WHBM]

ICAO issues and enforces the rules of international aviation, such as the freedoms of airspace. But what does IATA do? I'm seriously asking this question. I have NO idea.
IATA is a trade body of all the mainstream carriers, on the commercial side. They represent interline agreements, revenue division, commercial policies, relations with travel agencies and other sales agents, and such like. This mirrors what ICAO do on the operational and technical side.

Their relevance to the situation is in the forward planning of schedules and making reservations, where the aircraft provision and schedules are currently substantially disorganised by the grounding, such that carriers currently are unsure what capacity they may have available for the season ahead. It now looks likely the Max is going to be grounded right through the summer peak period, and carriers affected are going to be facing up to different timetables, and offering different fare structures through their yield management plans, to what they might have hoped.

[tdracer]

As others have noted, absolute safety is a myth - nothing in life is completely safe.
For certification purposes, there is a definition of safe:
The probability of a catastrophic outcome is ~ 10-9/flight hour (or less - less is always better).
The miss was that no one at Boeing or the FAA (or EASA) identified MCAS as being a flight critical system that needed to meet that 10-9 requirement.
I'm not privy to everything the 'fix' entails, but 10-9/hr. is the standard it will need to meet to be determined safe.

[Water pilot]

I don't think the MAX will be flying in Europe any time soon, there is a very nasty trade war brewing. The WTO has found that Airbus has been illegally subsidized by the government and so the US will be able to impose tariffs. Boeing is also illegally subsidized but the case is not as far along so there is going to be five or six months of one-sided tariffs (affecting cheese makers, etc.) over airplanes. It is a little hard to see that the European regulators are going to cut Boeing much slack, I imagine a "work to rule" type situation and they have plenty of ammunition. I don't know how many airlines will be affected; I do know that Sunwings in Canada is already cancelling flights and blaming Boeing (although they are affected by a different trade war.)

[Bidule]

SWhereas the French socialist who went to the same school as the recent French president Francois Hollande, a school where Jean-Paul Sartre, no less, was a teacher once, "?!

Which school? To my knowledge, Jean-Paul Sartre was never a teacher in HEC (Hautes Etudes Commerciales) or ENA (Ecole Nationale d'Administration).

As you do not seem to like the socialists, you should not be comfortable in Zurich as I think the mayor still is a socialist (for a number of years).
.

[DaveReidUK]

Which school? To my knowledge, Jean-Paul Sartre was never a teacher in HEC (Hautes Etudes Commerciales) or ENA (Ecole Nationale d'Administration).

Lycée Pasteur (Neuilly-sur-Seine) (https://fr.wikipedia.org/wiki/Lyc%C3%A9e_Pasteur_(Neuilly-sur-Seine))

[Icarus2001]

The entire point of the introduction of MCAS is that the 737 MAX without MCAS responds to pitch control inputs differently to earlier models. In particular, runaway pitch-up is possible.
Only at a very small part of the flight envelope at or near the critical angle of attack.

How many times...

[ProPax]

Lycée Pasteur (Neuilly-sur-Seine)

Thank you. :-)

[ProPax]

IATA is a trade body of all the mainstream carriers, on the commercial side. They represent interline agreements, revenue division, commercial policies, relations with travel agencies and other sales agents, and such like. This mirrors what ICAO do on the operational and technical side.

Their relevance to the situation is in the forward planning of schedules and making reservations, where the aircraft provision and schedules are currently substantially disorganised by the grounding, such that carriers currently are unsure what capacity they may have available for the season ahead. It now looks likely the Max is going to be grounded right through the summer peak period, and carriers affected are going to be facing up to different timetables, and offering different fare structures through their yield management plans, to what they might have hoped.

Making schedules and reservations. IATA does that? Not the airlines themselves? So if, say, Lufthansa or British Airways want to open a new route, they have to go through IATA?

And another thing that caught my eye is "revenue division". How do they do that? Airlines pay to some kind of fund which then gets redistributed? I have never heard of any of this. Very interesting.

Is membership in IATA mandatory for any airline?

Just trying to understand how it works. (insert confused smiley)

[GLAEDI]

Making schedules and reservations. IATA does that? Not the airlines themselves? So if, say, Lufthansa or British Airways want to open a new route, they have to go through IATA?

And another thing that caught my eye is "revenue division". How do they do that? Airlines pay to some kind of fund which then gets redistributed? I have never heard of any of this. Very interesting.

Is membership in IATA mandatory for any airline?

Just trying to understand how it works. (insert confused smiley)

not really for this thread but IATA covers things like interlining bags from one airline to another, tickets so that BA can ticket on AA and the like, they collect revenue from one airline that needs to pay another for services. They also cover route fares (an airline can reduce tickets from the IATA fare) ie a single from NY to LHR economy would be say $1,500. You don’t have to be a member but then you working with other airlines can be difficult. If you a small airline and you want to sell a route where one leg is with you and another is on a major airline, they won’t entertain you unless you have an IATA registration as it’s an insurance they’ll get paid if you go bust.

[groundbum]

maybe the IATA bits need a separate thread..

G

[ProPax]

not really for this thread but IATA covers things like interlining bags from one airline to another, tickets so that BA can ticket on AA and the like, they collect revenue from one airline that needs to pay another for services. They also cover route fares (an airline can reduce tickets from the IATA fare) ie a single from NY to LHR economy would be say $1,500. You don’t have to be a member but then you working with other airlines can be difficult. If you a small airline and you want to sell a route where one leg is with you and another is on a major airline, they won’t entertain you unless you have an IATA registration as it’s an insurance they’ll get paid if you go bust.

OOOOH! Like a clearing house of sorts. I see now. Thank you so much for the information. Looks like we do need them after all. Okay, Monsieur de Juniac, you may stay a while longer. :-)

maybe the IATA bits need a separate thread..
Nah. I got all the info I wanted... for now. :-)
Thanks.

[Bergerie1]

IATA does many things for the aviation industry in addition to acting as a clearing house, such as training courses for airlines, publishing manuals like this one on dangerous goods:- https://www.iata.org/publications/dgr/Pages/index.aspx
and this one on ground handling:- https://www.iata.org/publications/store/Pages/iata-ground-operations-manual.aspx

These manuals and the work of the various specialist groups help to standardise procedures across the whole industry.

IATA also works with ICAO, national ANSPs and airports to improve facilities for international aviation:- https://www.iata.org/whatwedo/workgroups/Pages/operations.aspx

ProPax, it helps to do your homework!!

[DaveReidUK]

OOOOH! Like a clearing house of sorts. I see now.

In fact they couldn't think of a more imaginative name for it.

IATA Clearing House (https://www.iata.org/services/finance/clearinghouse/Pages/index.aspx)

[BluSdUp]

Non of the big European Low Cost airlines are IATA members.
IATA is a club for the Big Flag carriers of old with any Commuters that wants business joining for a hefty fee.
The ONLY thing effecting me as a 737-800 pilot and future Max pilot from IATA is the Dangerous Goods Manual , once a Year on the Swimming Course ( Safety Course) with the girls.
IATA has NOTHING to do with the Certification of any Aircraft, they just have members that has bought a few 737 Max.
As a potentially united customer group they could push Boeing, but I doubt they are able to agree on any specific and productive demands.

So
ICAO and FAA issue Recommendations, NCAA, FAA and EASA set Rules, Regulations and Practices for Certification of Aircraft.
IATA play with the Toy and the Money.

This is the bigger picture , the way I see it.
Regards
Cpt B

[Zeffy]

https://www.seattletimes.com/nation-world/ethiopian-pilot-pleaded-for-training-weeks-before-max-crash/

Ethiopian pilot pleaded for training weeks before Max crash
May 29, 2019 at 12:47 pm Updated May 30, 2019 at 7:35 am

By BERNARD CONDON
The Associated Press

NEW YORK (AP) — Just days after a Lion Air Boeing 737 Max nosedived in Indonesia and killed all 189 people aboard, an Ethiopian Airlines pilot began pleading with his bosses for more training on the Max, warning that crews could easily be overwhelmed in a crisis and that one of their planes could be the next to go down.

“We are asking for trouble,” veteran pilot Bernd Kai von Hoesslin wrote in a December email obtained by The Associated Press, adding that if several alarms go off in the cockpit at once, “it will be a crash for sure.”

That prediction proved all too accurate.

What Ethiopian Airlines did in response to his warnings is unclear, and whether it made any difference is a matter of dispute. But within weeks, an Ethiopian Max indeed went down, killing all 157 people on board. It slammed into the ground amid a flurry of alarms as the pilots struggled to control a malfunction in the automatic anti-stall system.

While the anti-stall system has gotten most of the scrutiny in the two Max crashes five months apart that have led to a worldwide grounding of the planes, the concerns raised by von Hoesslin have added to a debate on the role pilot error played, and whether Ethiopian’s pilots were as prepared as they could have been to avert disaster.

Von Hoesslin, a Canadian citizen who resigned from Ethiopian last month, argued in three emails to senior managers after the anti-stall system came under scrutiny in the Lion Air crash that crews flying Ethiopian’s five Max jets should have been given more information and training on how the system worked. He also said pilots should be drilled on the steps to override it if it faltered. Von Hoesslin’s emails were first reported by Bloomberg.

The Max’s system, called MCAS, for Maneuvering Characteristics Augmentation System, automatically pushes the plane’s nose down when it is at risk of stalling. It misfired in both fatal crashes, with pilots losing control of the plane as they fought against it.

According to the email chain obtained by the AP, Ethiopian responded to the Oct. 29 Lion Air crash with a few emails to pilots detailing bulletins from the U.S. Federal Aviation Administration and Boeing on what do if the anti-stall system malfunctioned. Other Ethiopian pilots who spoke to the AP say those emails required no signoffs that pilots actually read and understood the directives, and no mandated additional training.

“Ethiopian Airlines is a rapidly expanding airline and they have extremely inexperienced crews,” von Hoesslin said in documents obtained by the AP. “You need to spoon-feed them the information and make sure they understand.”

To underscore his point, von Hoesslin made a video shortly after the Ethiopian crash in which he quizzed a Max pilot on a Boeing list of warning signs on the stall system that crew members were required to commit to memory. That video, obtained by AP, shows him going blank on most of it.

“You have to have confirmation that they opened it, that they read it and that they understood it,” von Hoesslin said in a document obtained by the AP. “They should have done a little online test with 10 questions. You don’t pass until you get the 10 questions.”

Ethiopian Airlines tweeted Wednesday that “the source of these false allegations is a disgruntled former employee … who has left the airline after many administrative problems.”

Von Hoesslin’s lawyer, Darryl Levitt, issued a statement saying the pilot was not fired but “resigned due to legitimate concerns he had raised that he felt were not adequately addressed.” He added that von Hoesslin will be cooperating with regulators and authorities “with his sole objective of contributing to make air travel safe.”

Ethiopian has said that the requirements for warning and training Max pilots after the Lion Air crash were set by the FAA and Boeing and that their directives were used to “brief all our pilots” and incorporated into flight manuals.

CEO Tewolde Gebremariam said in an interview shortly after the Ethiopian crash, “Today we believe that might not have been enough.”

Gebremariam declined to say whether the pilots on the doomed flight took additional training after the Lion Air crash on Ethiopian’s Max simulator, a multimillion-dollar piece of equipment most airlines don’t have, but said “it wouldn’t have made any difference” because the simulator wasn’t designed to imitate problems in the new jet’s flight-control system.

Ethiopian has said both the captain and co-pilot followed all the steps Boeing laid out in its bulletin on how to respond to a malfunction in the anti-stall system.

But the preliminary report on the March 10 crash of Ethiopian Airlines Flight 302 from Addis Ababa to Nairobi showed that the pilots deviated from the directives and made other mistakes, notably flying the plane at an unusually high speed and inexplicably reactivating the anti-stall system shortly after manually overriding it.

Six minutes into its flight, the plane with passengers from nearly a dozen countries cratered into the ground about 40 miles from the airport.

Former FAA Administrator Randy Babbitt said the Ethiopian pilots clearly bear some of the blame.

“So Boeing was at fault because a light came on or this thing tripped mistakenly, but it shouldn’t have brought the airplane down,” Babbitt said of the anti-stall system. “That was very fixable and a pretty simple solution. And they didn’t come to grips with it. … They let the plane get away from them.”

Peter Lemme, a former Boeing engineer who worked on flight control systems, said apportioning blame between Boeing and the crew is difficult.

“Some pilots in their easy chairs are saying they would have known how to react, but it’s not so easy,” he said. “Did the pilots cause the accident? No. Could they have prevented it? Yes.”

Von Hoesslin, a 56-year-old pilot with three decades of flying experience, initially wrote to his bosses Nov. 11 in response to the airline’s five-sentence email to dozens of pilots alerting them to the Boeing bulletin and reminding them about the checklist of steps to perform should something similar go wrong.

He urged Ethiopian to give more information because pilots are not “fully or even aware of how” the MCAS works. That prompted a second email from the airline with more detail.

A month later, on Dec. 12, von Hoesslin sent another email, urging a close reading of a preliminary report from Indonesian regulators on the crash there. He pointed out several potential problems with the Max and recommended steps be taken to make sure pilots know the checklist.

The next day, he sent a third email recommending new simulator training designed to roughly re-create what went wrong in the Indonesian flight, adding that he had already practiced in a simulator rigged in such a way and his experience with all the alarms going off was frightening.

“Throw in a GPWS PULL UP” — a warning to pilots that the plane is in danger of crashing into the ground — “and it would be a crash for sure.”

Boeing has said that its fix to software on the Max’s anti-stall system will be accompanied by additional training for pilots. The acting chief of the FAA, Daniel Elwell, said last week that his agency hasn’t decided whether that training should be conducted on computers or in flight simulators.

___

AP writer David Koenig in Dallas and researchers Jennifer Farrar, Randy Herschaft and Rhonda Shafner in New York contributed to this report.

BERNARD CONDON

[aixois]

Water Pilot wrote :


I don't think the MAX will be flying in Europe any time soon, there is a very nasty trade war brewing. The WTO has found that Airbus has been illegally subsidized by the government and so the US will be able to impose tariffs. Boeing is also illegally subsidized but the case is not as far along so there is going to be five or six months of one-sided tariffs (affecting cheese makers, etc.) over airplanes


That is right of course and for the disputes there is a brief on this website ::


leehamnews.com/2019/03/28/wto-appeals-court-rules-against-boeing-airbus-claims-minimum-15bn-in-harm/
:

Good evening to everyone.

[nevillestyke]

Well, one thing they (IATA) do is set the rules for air transport of hazardous lithium-ion batteries. I see, from a listing for a power bank on ebay, that there are some Chinese suppliers who openly admit to flaunting these safety regulations.
Quote from the listing:
" 5、 The delivery time of each country's post office is different, the arrival time may be delayed, please be sure to wait patiently

6、Our product capacity is large, if the huge capacity (MAH) is printed on the power bank, it can not be allowed to transported by the aircraft,so our products are not printed capacity information, please understand

7、We ensure that the product 100% is brand-new, but the transport time is long, and the collision in the transport process may cause a small number of product damage, which is unavoidable, if there is damage please contact us in time. "

[ProPax]

We do need a separate thread on IATA, it seems. :-) I'm learning more and more and I have more questions, but I do realize I started an off-top. Can we somehow move it to another thread?

[BluSdUp]

A very interesting article on what Cpt Bernd von Hosselin had asked ET after the Lion accident.
I find that disturbing.
I hope he gets support to tell and document the truth.
Regards
Cpt B

[Chris2303]

When I first started in the industry in 1967 IATA was responsible for:

Clearing house for interline travel
Tariff setting
Inflight standards (configuration/meals/alcohol)

Amongst other things that my old brain has forgotten

[Bend alot]

As per the tread title - the delay seems to be more Boeing not officially submitting the fix to the FAA.

Why is there the delay?

Boeing say they have fixed it (not that there was ever a problem), is there fear in the test flight stage of not being able to manually move the trim wheel, when it is expected to be movable. Surely most regulators will want evidence of the trim wheel "actual flight" forces to move until it will not move.

Then since MCAS is not a part of this test flight now (had it's one input so locked out) and the MAX is essentially a NG with a trim wheel not able to move.

Nothing quite like doubling the bet - MAX grounding lifted or MAX and NG grounded.

[Bergerie1]

Chris2303,

In its early days IATA was concerned too much with ticket pricing and meals standards etc. But now, as well as cting as a clearing house, a large part of IATA's work has been to work alongside ICAO to improve the Standards and Recommended Practices and to promote their application by member states to provide consistent standards for better worldwide ATC, airports and air navigation facilities. https://www.icao.int/safety/safetymanagement/pages/sarps.aspx

In the early days it was much like a cartel, but since then it has moved with the times, pushing for safer standards, more ATC and airport capacity to reduce delays and greater cost effectiveness. It also conducts safety audits for member airlines. https://www.iata.org/whatwedo/safety/audit/iosa/Pages/index.aspx

[Beausoleil]

I agree that most people use the terms "safe" and "unsafe"; however, there is no such thing as "safe". "Safety" is a concept of relativity. There will always be risk in every human endeavor, ranging from "slight risk" to "severe risk", and the real world deals with risk management, not attempts to achieve absolute safety ... whatever that is. For example, walking is a relatively safe activity given normal circumstances; yet, walking on the edge of an icy precipice in a snowstorm involves more risk, requiring more caution ... hence "risk management". I could go on and on about this, but I won't.

This is just my opinion; but that opinion is based on 43 years of safety related work and accident investigation.

Cheers,
Grog

I think that for practical purposes, making "safe" means reducing the risk from an activity so that there is no significant additional risk from taking part above the risk encountered on a typical day.

At my age, I have about a 1 in 500000 chance of dying on any given day. Sitting in a commercial airliner for 8 hours protects me from some everyday risks but exposes me to some others (chiefly medical I suspect). Also the radiation exposure slightly increases my risk of developing cancer at some point. The risk from a crash is negligible... less than 1 in 10 million last time I looked.

The risk from crashes has been reduced far below the practical safe level as much for commercial reasons as anything. It is tremendously impressive

[PEI_3721]

Bend alot, # 78

Boeing proposed a modification, 17 Apr. https://www.boeing.com/commercial/737max/737-max-software-updates.page
This was rejected by the FAA, no specific reasons given, thus Boeing reviewed and amended the design. According to some US sources this was recently resubmitted together with a training plan; training is reported as being essentially the same as the information above - no simulator (CNN 30 May https://amp.cnn.com/cnn/2019/05/30/politics/737-max-computer-simulator/index.html).

In parallel, other certification authorities have been briefed and are considering the new proposals. Although the lead certification is the FAA, there is great pressure on having a worldwide consensus due the ‘loss of trust’, procedural - oversight, self regulation embarrassments. This could be a lengthy process especially if linked with subjective assessments of procedural effectiveness as below.

The FAA has launched a separate study of procedures, assumed to be for trim runaway, this could apply to both the Max and NG. From Pprune discussions there appears to be significant concern about the viability of the drill which depends on quick identification and action, and difficulty in moving the trim wheel.

The NG and Max could differ in the severity of a runaway and / or effectiveness of recovery. Aerodynamically there is the difference - the need for MCAS; then there are changes in thrust levels, wings ….

Test flights might be difficult. The normal trim curve technique of trimming against stick force (constant speed / altitude - but covering the full operational environment and configuration) might find that the interpretation of stick top elect trim inhibition (EASA query) creates additional problems with the use of trim wheel - elect trim for failure, manual trim wheel for recovery. Also limiting forces might be encountered before maximum trim. In addition it might be easier to mis-trim the aircraft (away from trim) opposed to recovering from a failure condition - effect of asymmetric elevator force in aiding or opposing trim with respect to the trim wheel input.

The obvious is to avoid situations where recovery might not be assured; - evaluate the effectiveness of roller coaster manoeuvre before hand - but how.
Design quality simulation would be essential, but where did the training simulator discrepancies originate. If the source data is incorrect / unavailable, test flights would need to collect and validate new data, this too could involving the problems above.
Whilst the test aircraft might have escape doors and the crew equipped with parachutes to mitigate unforeseen risk, the associated political and commercial risks might be so great that testing will be a very slow process or alternative means of compliance are being considered, requiring worldwide agreement in the fullness of time.

P.S. Not quite the same tone or confidence which might be expected at this time :-
‘… expressed cautious optimism’
‘… hopeful that the FAA will exercise its usual due diligence and swiftly approve the recently completed software fix’
https://www.airlive.net/boeing-ceo-hopes-faa-will-swiftly-approve-the-recently-completed-software-fix-of-the-737max 1 June

[Fly Aiprt]

As per the tread title - the delay seems to be more Boeing not officially submitting the fix to the FAA.

Why is there the delay?

Boeing say they have fixed it (not that there was ever a problem), is there fear in the test flight stage of not being able to manually move the trim wheel, when it is expected to be movable. Surely most regulators will want evidence of the trim wheel "actual flight" forces to move until it will not move.

Then since MCAS is not a part of this test flight now (had it's one input so locked out) and the MAX is essentially a NG with a trim wheel not able to move.

Nothing quite like doubling the bet - MAX grounding lifted or MAX and NG grounded.

Excellent post, Bend alot !
What if Boeing has fixed the MCAS part of its software, but is secretly negociating for the flight test to NOT show what the control forces and trim wheel ability to be moved actually are ?

[Bend alot]

PEI 3721 - This we expect to be covered then in the iPad differences training!

"The NG and Max could differ in the severity of a runaway and / or effectiveness of recovery. Aerodynamically there is the difference - the need for MCAS; then there are changes in thrust levels, wings …."

My bold.

[PEI_3721]

Bend alot,
What if the difference now focuses on trim runway.
The NG in-service, apparently without incident. The Max grounded following two accidents which suggests that the trim runaway drill might be ineffective.

NG no events - ‘successful’ outcome, history; but this does not change the risk of a trim malfunction.
The risk in the Max could be similar if not the same, but with different history. One ‘success’ out of three does not change the system risk, but it could influence the regulatory views on crew’s contributions in recognition and action. Unfortunately the ‘success’ suggests that the Max requires three qualified crew, or conversely reinforces view that two cannot be expected to detect and manage a trim runaway in proportion to severity of the event’s circumstance (risk).

What if … this is the central topic of inter-regulator discussions; who judges, how, when, perhaps after more testing and data to assess.
Meanwhile historical risks are accepted (who bears that risk); future risk - wait and see.

[gums]

Salute!
Thanks Bend and PEI.
I just have a hard time with Boeing not keeping the manual electric trim operating when MCAS does its trick.

Looks like Boeing is sticking to the "existing procedures would have prevented the crashes" story. Ditto for some of the uber pilots here. Problem is recognizing what is wrong and the magnitude/length of the MCAS commands.

PEI might be able to explain it in technical terms that some here will not fathom, but I say go for it.
- Why can't the trim commands be a function that uses "q" and mach as we did in the Viper instead of a "bang-bang" fixed amount and fixed time of application? In other words, follow a geometric plot as we did for AoA versus gee and control deflection gains.
- If MCAS is using the A/P circuits, why disable other force functions such as the control column switches for force ( not the electric switches).

Gotta be nore than meets the eye, and I do not feel training is the answer. Fer chrissakes, we are not training Top Gun fighter pilots or NASA astronauts.

Gums sends...

[Longtimer]

When I first started in the industry in 1967 IATA was responsible for:

Clearing house for interline travel
Tariff setting
Inflight standards (configuration/meals/alcohol)

Amongst other things that my old brain has forgotten
To name two very important ones:
IATA's Live Animals Regulations (LAR) is the worldwide standard for transporting live animals by commercial airlines. live animals, safety, welfare, traveler's pet corner, regulations, LAR, live animal regulations, corrigendum-I, wildlife products, training, LAPB, live animals and perishables board, illegal wildlife trafficking https://www.iata.org/whatwedo/cargo/live-animals (https://www.iata.org/whatwedo/cargo/live-animals)
Dangerous Goods Regulations (DGR) (https://www.iata.org/publications/dgr)IATA's Dangerous Goods Regulation (DGR) helps you classify, mark, pack, label and document dangerous shipments and hazardous materialshttps://www.iata.org/publications/dgr (https://www.iata.org/publications/dgr)
And many more …..

[ProPax]

If this whole unmovable trim wheel kerfuffle plays out to its full potential, Boeing is staring down the barrel of BOTH MAX and NG being grounded. And that might very well be the end not only for the 737, but for the Boeing Company. I'm not even sure their military division will be able to bail them out, unless they quickly disconnect the two parts but that would require a shareholders meeting which won't be quick. (Correct me if I'm wrong.)

So, just hypothetically, wouldn't it be safer for Boeing to simply close the 737MAX program, cut their losses, buy back the MAXes and try to cuddle the FAA into stopping the NG trim wheel inquiries? They could then concentrate on NSA, or NMA, or MOM, or whatever it is they want to do. They would likely come out of this way behind Airbus in sales and customer trust, and will have to fight back into that market, AND they have very little experience in that kind of marketing. It will be a HUGE loss and an enormous effort. But, IMHO, it's the lesser evil. The more this drags on, the less likely Boeing is to come out of this alive. As much as I like Airbus, I don't want them to be an unopposed monopolist.

[gums]

Salute ProPax!

You have cracked the code.

Years ago Lockheed had a design problem with their Electra turboprop. Harmonics and weak components resulted in a few fatal accidents.

Lockheed bit the bullet, grounded all the planes and then refurbished all of them at their expense. The descendants became the P-3 Orion anti-sub platform and they still have one or two flying somewhere.

Apparently, the 800 and 900 and such have been big sellers, and only reason I see for the MAX was better fuel economy.

Gums sends...

[SometimeFlyer]

SLF here who worked for the UK government for too long. Please don't shoot me, it kept me off the streets.

It seems possible that when the FAA allowed Boeing to self certify they assumed a level of Trust. Speculation, but they *may* now feel that Boeing did not act entirely in line with that level of trust. In which case I wouldn't be surprised if the FAA (et al) are now reviewing every document, email and report they received from Boeing ref the newer 737 offerings with a fine tooth comb, in the light of recent experience. Depending on the time scales, they may also feel that now is good time for a detailed review of the stuff they were sent on the Drainliner and perhaps the also 777X. Could take a while.

[yoko1]

If this whole unmovable trim wheel kerfuffle plays out to its full potential, Boeing is staring down the barrel of BOTH MAX and NG being grounded. And that might very well be the end not only for the 737, but for the Boeing Company. I'm not even sure their military division will be able to bail them out, unless they quickly disconnect the two parts but that would require a shareholders meeting which won't be quick. (Correct me if I'm wrong.)


Not to say that there is never room for improvement, but such a drastic action would have to be reconciled with the fact that the 737NG has one of the best safety records of any commercial aircraft ever built.

[PEI_3721]

Yo, gums,
Why not use ‘q’
I don’t know; superficially speed for trim would be a logical association.
However, as much as Boeing sticks to the stability line, the aircraft’s sensitivity at low speed suggest that AoA is required for avoiding a stick force reduction with decreasing speed (pre stall region), particularly at high altitude where Mach is also used in the computation (restriction).

Given the above, there is nothing in the accidents to indicate that MCAS did not work as expected, except for the ‘single’ sensor failure - rubbish in rubbish out. We must assume that this error path is now completely shutdown with cross checking etc, and does not introduce any further contribution to trim failure than in previous aircraft.
MCAS fades into the background similar to STS; crew knowledge required, no immediate action except awareness of areas of reduced stability. For that, a MCAS ‘off’ alert would be preferred, opposed to a deduction from AoA Disagree. Would MCAS shut down for any other reason.

ProPax,
There could be many intermediate alternatives.
Why is such a large trim range required; if this could be reduced then the trim wheel force might be reduced. This might require cg, speed, altitude restrictions; room for compromise.
Reduced elect trim speed (trim motor electrics - runaway scenario) could be another option, or an increased lever arm for manual wheel operation, or increased gearing for wheel speed.
Adjust the elevator effectiveness - might be a bit drastic, but if needs must.

[A and C]

I just don’t see this trim wheel kerffufflle as you put it, the method of bringing the trim back into the normal range has been known since the days of the B707 and has not been an issue.

The issue is that training departments in airlines have forgotten the lessons of the past.

[futurama]

Boeing is staring down the barrel of BOTH MAX and NG being grounded. And that might very well be the end not only for the 737, but for the Boeing Company.
The NG has nearly 7,000 aircraft in service and has been in the air for 22 years with zero crashes due to runaway trim.

The chances that the NG will be grounded: zero. It has proven itself to be a very safe aircraft.

With MCAS disabled (post fix), the MAX's safety profile from a trim runaway is the same as the NG.

The "end of Boeing" scenario being posed here is pure fantasy.

[safetypee]

A and C,
The difficulty appears to be with the ability of the elevator to control pitch - nose up, before the procedure can be used.
Larger tail area - trim, same elevator, changes in aerodynamics, hydraulic jack stall. Perhaps small changes, but incrementally eroding the margin for recovery.
Inaccurate simulation, false assumptions based on previous, smaller aircraft.

futurama, ‘zero accidents’ does not affect the inherent risk of system failure - outcome bias.
Never a zero chance of anything, particularly in aviation.

[gums]

Salute!

Prolly should discuss the technical stuff on other forum, but if I were on the review cmte for releasing the MAX for widespread use I would question Boeing about several aspects of their MCAS implementation from tht of a user viewpoint and an aero engineer and experienced pilot having flown half a dozen jets with various "gotchya's" and such.
@PEI I propose "q" because it appears MCAS uses mach to determine the amount of deflection and such. Gotta review, but seems mach became a player above 0.65 M or so.Without a good diagram of the function, we can only guess. But FCeng indicated that at higher mach the incrememntal stab movement is not only less but maybe not even as long of application.If the thing can use mach, then it can use "q'. That would avoid the severe forces that cause problems with the manual wheel trim, heh? It is not hard to design a simple analog chip that integrates AoA and Q to determine how much and how fast to move the stab in order to meet the requirements.

Let's face it. 10 seconds of nose down trim at a quarter degree per pulse is harsh!!! Yeah, yeah, yeah, the Yeager folks here will simply "go manual" as R2D2 is melting. But seriously, Boeing has to do more than recommend training and more adjustments to the kludge.

Gums sends...

[futurama]

safetypee, no where did I write that the risk is zero. Very safe is not zero risk.

Also, "outcome bias" does not mean what you think it means. :hmm:

[FrequentSLF]

ProPax,
There could be many intermediate alternatives.
Why is such a large trim range required; if this could be reduced then the trim wheel force might be reduced. This might require cg, speed, altitude restrictions; room for compromise.
Reduced elect trim speed (trim motor electrics - runaway scenario) could be another option, or an increased lever arm for manual wheel operation, or increased gearing for wheel speed.
Adjust the elevator effectiveness - might be a bit drastic, but if needs must.

In case the forces have increased the complete mechanical system might be unsafe. First thing that comes to my mind are the steel cables... but is not limited to those only

[hec7or]

gums
I just have a hard time with Boeing not keeping the manual electric trim operating when MCAS does its trick.

sorry to be a pedant, but the B737 has manual trim, aileron trim, rudder trim, main electric trim, auto trim, mach trim, and speed trim - (of which MCAS is a subsystem)

there is no such thing as manual electric trim

[ProPax]

There are many solutions to this problem, indeed. Add a few switches, string a few cables, reduce/enlarge, install a motor, etc. BUT!!! Any of those would need to be certified. And that won't be easy. There are at least three disgruntled parties involved - China with increased tariffs, Europe with increased tariffs, and Canada with a badly enginnered attempt to increase tariffs. So whatever Boeing does, whatever solution they come up with, it will hit the wall worse than Dale Earnhardt.

EASA, TCCA, and CAAC will, with almost 100% probability, demand full re-certification if any new systems are added to an already troubled airplane. And actually, I don't think FAA will be too accomodating, either, after Boeing humiliated them with this whole "self-certify" calamity. The political climate is such that the current administration needs to "do something right". And Boeing may just as well serve as an object lesson.

I just don't see a different way out of this for Boeing. They were late grounding the MAX when it was apparent that MCAS was involved in both accidents, and were forced to take action. They blamed the crew. They enraged the pilots community. Their reputation is badly damaged. If they are again forced to re-certify the MAX and then the NG, it may become the proverbial nail in the coffin. They should really bite the bullet and make a proactive move. Considering that many MAXes were sold with incredible discounts, buying them back won't be such a terrible expense.

It still leaves the issue of the NG trim wheel loads, but considering it's been in the skies for quite some time, and provided Boeing acts fast, certifies the modification, and modifies the fleet at their own expense, they may get away with it.

[Smythe]

article from NYT on the foundation of MCAS...very interesting

https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html

[ProPax]

article from NYT on the foundation of MCAS...very interesting

https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html

If they needed to have G-force sensors removed, but still needed to have an AoA safeguard, why not attach the gyros to the system? Does 737 have gyroscopes? That would be a safeguard that won't affect slow-speed anti-stall activation but would still allow MCAS to stay quiet if AoA sensors failed.

Or am I talking rubbish?

[airsound]

The excellent Roger Latham has this offering in Private Eye

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/492x360/img_4568_36720139339ef5a6d6b755da4879fabe09f9db73.jpg


airsound

[gums]

Salute!

Excuse me, mister hector , and sorry to not refer to those switches on the control column that most of us refer to as "manual electric trim switches" as opposed to cranking that wheel on the center console.

Most of us are also fully aware of the numerous ways Hal can trim the stab, and we have even looked at and commented on the electrical wiring for the MAX with MCAS.. As Paul Simon said in a song, "there must be 50 ways to......",

In all three MCAS incidents the "manual electric trim switches" worked and countered the rogue MCAS trim commands. All three, according to the FDR traces. And one crew went manual real early whether they understood what was wrong or not ( their squawk comment was "STS working backwards", and you can look it up on post 2,56x or whatever).

The beef with the MCAS implementation is that the corrective procedure for "runaway trim/MCAS/x" disables those column switches that worked on all three incidents. GASP!!! I don't like it, and I would have raised a stink if flying a route in those planes.

@smythe...... a great New York Slimes link and maybe even more damning evidence for the juries to consider in the upcoming lawsuits, ya think?

Gums sends...

[MurphyWasRight]

gums
I just have a hard time with Boeing not keeping the manual electric trim operating when MCAS does its trick.


gums

sorry to be a pedant, but the B737 has manual trim, aileron trim, rudder trim, main electric trim, auto trim, mach trim, and speed trim - (of which MCAS is a subsystem)

there is no such thing as manual electric trim

I suspect gums was referring to the change in the trim cutout switches from NG > MAX, likely he meant pilot thumb switch trim by 'manual electric trim'

NG one switch disables all automatic trim inputs, the other disables ALL including pilot electric trim inputs.

MAX either switch disables ALL electric trim.

Reverting to the NG configuration 'might' be one way out of the stuck trim question.

[Zeffy]

https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html


Boeing Built Deadly Assumptions Into 737 Max, Blind to a Late Design Change

By Jack Nicas, Natalie Kitroeff, David Gelles and James Glanz
June 1, 2019

SEATTLE — The fatal flaws with Boeing’s 737 Max can be traced to a breakdown late in the plane’s development, when test pilots, engineers and regulators were left in the dark about a fundamental overhaul to an automated system that would ultimately play a role in two crashes.

A year before the plane was finished, Boeing made the system more aggressive and riskier. While the original version relied on data from at least two types of sensors, the ultimate used just one, leaving the system without a critical safeguard. In both doomed flights, pilots struggled as a single damaged sensor sent the planes into irrecoverable nose-dives within minutes, killing 346 people and prompting regulators around the world to ground the Max.

But many people involved in building, testing and approving the system, known as MCAS, said they hadn’t fully understood the changes. Current and former employees at Boeing and the Federal Aviation Administration who spoke with The New York Times said they had assumed the system relied on more sensors and would rarely, if ever, activate. Based on those misguided assumptions, many made critical decisions, affecting design, certification and training.

“It doesn’t make any sense,” said a former test pilot who worked on the Max. “I wish I had the full story.”

While prosecutors and lawmakers try to piece together what went wrong, the current and former employees point to the single, fateful decision to change the system, which led to a series of design mistakes and regulatory oversights. As Boeing rushed to get the plane done, many of the employees say, they didn’t recognize the importance of the decision. They described a compartmentalized approach, each of them focusing on a small part of the plane. The process left them without a complete view of a critical and ultimately dangerous system.

The company also played down the scope of the system to regulators. Boeing never disclosed the revamp of MCAS to Federal Aviation Administration officials involved in determining pilot training needs, according to three agency officials. When Boeing asked to remove the description of the system from the pilot’s manual, the F.A.A. agreed. As a result, most Max pilots did not know about the software until after the first crash, in October.

“Boeing has no higher priority than the safety of the flying public,” a company spokesman, Gordon Johndroe, said in a statement.

He added that Boeing and regulators had followed standard procedures. “The F.A.A. considered the final configuration and operating parameters of MCAS during Max certification, and concluded that it met all certification and regulatory requirements,” Mr. Johndroe said.

At first, MCAS — Maneuvering Characteristics Augmentation System — wasn’t a very risky piece of software. The system would trigger only in rare conditions, nudging down the nose of the plane to make the Max handle more smoothly during high-speed moves. And it relied on data from multiple sensors measuring the plane’s acceleration and its angle to the wind, helping to ensure that the software didn’t activate erroneously.

Then Boeing engineers reconceived the system, expanding its role to avoid stalls in all types of situations. They allowed the software to operate throughout much more of the flight. They enabled it to aggressively push down the nose of the plane. And they used only data about the plane’s angle, removing some of the safeguards.

The disasters might have been avoided, if employees and regulators had a better understanding of MCAS.

A test pilot who originally advocated for the expansion of the system didn’t understand how the changes affected its safety. Safety analysts said they would have acted differently if they had known it used just one sensor. Regulators didn’t conduct a formal safety assessment of the new version of MCAS.

The current and former employees, many of whom spoke on the condition of anonymity because of the continuing investigations, said that after the first crash, they were stunned to discover MCAS relied on a single sensor.

“That’s nuts,” said an engineer who helped design MCAS.

“I’m shocked,” said a safety analyst who scrutinized it.

“To me, it seems like somebody didn’t understand what they were doing,” said an engineer who assessed the system’s sensors.

MCAS Is Born
In 2012, the chief test pilot for the Max had a problem.

During the early development of the 737 Max, the pilot, Ray Craig, a silver-haired retired Navy airman, was trying out high-speed situations on a flight simulator, like maneuvers to avoid an obstacle or to escape a powerful vortex from another plane. While such moves might never be necessary for the pilot of a passenger plane, the F.A.A. requires that a jet handle well in those situations.

But the plane wasn’t flying smoothly, partly because of the Max’s bigger engines. To fix the issue, Boeing decided to use a piece of software. The system was meant to work in the background, so pilots effectively wouldn’t know it was there.

Mr. Craig, who had been with Boeing since 1988, didn’t like it, according to one person involved in the testing. An old-school pilot, he eschewed systems that take control from pilots and would have preferred an aerodynamic fix such as vortex generators, thin fins on the wings. But engineers who tested the Max design in a wind tunnel weren’t convinced they would work, the person said.

Mr. Craig relented. Such high-speed situations were so rare that he figured the software would never actually kick in.

To ensure it didn’t misfire, engineers initially designed MCAS to trigger when the plane exceeded at least two separate thresholds, according to three people who worked on the 737 Max. One involved the plane’s angle to the wind, and the other involved so-called G-force, or the force on the plane that typically comes from accelerating.

The Max would need to hit an exceedingly high G-force that passenger planes would probably never experience. For the jet’s angle, the system took data from the angle-of-attack sensor. The sensor, several inches long, is essentially a small wind vane affixed to the jet’s fuselage.

Adding More Power
On a rainy day in late January 2016, thousands of Boeing employees gathered at a runway next to the 737 factory in Renton, Wash. They cheered as the first Max, nicknamed the Spirit of Renton, lifted off for its maiden test flight.

“The flight was a success,” Ed Wilson, the new chief test pilot for the Max, said in a news release at the time. Mr. Wilson, who had tested Boeing fighter jets, had replaced Mr. Craig the previous year.

“The 737 Max just felt right in flight, giving us complete confidence that this airplane will meet our customers’ expectations,” he said.

But a few weeks later, Mr. Wilson and his co-pilot began noticing that something was off, according to a person with direct knowledge of the flights. The Max wasn’t handling well when nearing stalls at low speeds.

In a meeting at Boeing Field in Seattle, Mr. Wilson told engineers that the issue would need to be fixed. He and his co-pilot proposed MCAS, the person said.

The change didn’t elicit much debate in the group, which included just a handful of people. It was considered “a run-of-the-mill adjustment,” according to the person. Instead, the group mostly discussed the logistics of how MCAS would be used in the new scenarios.

“I don’t recall ever having any real debates over whether it was a good idea or not,” the person said.

The change proved pivotal. Expanding the use of MCAS to lower-speed situations required removing the G-force threshold. MCAS now needed to work at low speeds so G-force didn’t apply.

The change meant that a single angle-of-attack sensor was the lone guard against a misfire. Although modern 737 jets have two angle-of-attack sensors, the final version of MCAS took data from just one.

Using MCAS at lower speeds also required increasing the power of the system. When a plane is flying slowly, flight controls are less sensitive, and far more movement is needed to steer. Think of turning a car’s steering wheel at 20 miles an hour versus 70.

The original version of MCAS could move the stabilizer — the part of the tail that controls the vertical direction of the jet — a maximum of about 0.6 degrees in about 10 seconds. The new version could move the stabilizer up to 2.5 degrees in 10 seconds.

Test pilots aren’t responsible for dealing with the ramifications of such changes. Their job is to ensure the plane handles smoothly. Other colleagues are responsible for making the changes, and still others for assessing their impact on safety.

Boeing declined to say whether the changes had prompted a new internal safety analysis.

While the F.A.A. officials in charge of training didn’t know about the changes, another arm of the agency involved in certification did. But it did not conduct a safety analysis on the changes.

The F.A.A. had already approved the previous version of MCAS. And the agency’s rules didn’t require it to take a second look because the changes didn’t affect how the plane operated in extreme situations.

“The F.A.A. was aware of Boeing’s MCAS design during the certification of the 737 Max,” the agency said in a statement. “Consistent with regulatory requirements, the agency evaluated data and conducted flight tests within the normal flight envelope that included MCAS activation in low-speed stall and other flight conditions.”

‘External Events’
After engineers installed the second version of MCAS, Mr. Wilson and his co-pilot took the 737 Max for a spin.

The flights were uneventful. They tested two potential failures of MCAS: a high-speed maneuver in which the system doesn’t trigger, and a low-speed stall when it activates but then freezes. In both cases, the pilots were able to easily fly the jet, according to a person with knowledge of the flights.

In those flights, they did not test what would happen if MCAS activated as a result of a faulty angle-of-attack sensor — a problem in the two crashes.

Boeing engineers did consider such a possibility in their safety analysis of the original MCAS. They classified the event as “hazardous,” one rung below the most serious designation of catastrophic, according to two people. In regulatory-speak, it meant that MCAS could trigger erroneously less often than once in 10 million flight hours.

That probability may have underestimated the risk of so-called external events that have damaged sensors in the past, such as collisions with birds, bumps from ramp stairs or mechanics’ stepping on them. While part of the assessment considers such incidents, they are not included in the probability. Investigators suspect the angle-of-attack sensor was hit on the doomed Ethiopian Airlines flight in March.

Bird strikes on angle-of-attack sensors are relatively common.

A Times review of two F.A.A. databases found hundreds of reports of bent, cracked, sheared-off, poorly installed or otherwise malfunctioning angle-of-attack sensors on commercial aircraft over three decades.

Since 1990, one database has recorded 1,172 instances when birds — meadowlarks, geese, sandpipers, pelicans and turkey vultures, among others — damaged sensors of various kinds, with 122 strikes on angle-of-attack vanes. The other database showed 85 problems with angle-of-attack sensors on Boeing aircraft, including 38 on 737s since 1995.

And the public databases don’t necessarily capture the extent of incidents involving angle-of-attack sensors, since the F.A.A. has additional information. “I feel confidence in saying that there’s a lot more that were struck,” said Richard Dolbeer, a wildlife specialist who has spent over 20 years studying the issue at the United States Department of Agriculture, which tracks the issue for the F.A.A.

A Simple Request
On March 30, 2016, Mark Forkner, the Max’s chief technical pilot, sent an email to senior F.A.A. officials with a seemingly innocuous request: Would it be O.K. to remove MCAS from the pilot’s manual?

The officials, who helped determine pilot training needs, had been briefed on the original version of MCAS months earlier. Mr. Forkner and Boeing never mentioned to them that MCAS was in the midst of an overhaul, according to the three F.A.A. officials.

Under the impression that the system was relatively benign and rarely used, the F.A.A. eventually approved Mr. Forkner’s request, the three officials said.

Boeing wanted to limit changes to the Max, from previous versions of the 737. Anything major could have required airlines to spend millions of dollars on additional training. Boeing, facing competitive pressure from Airbus, tried to avoid that.

Mr. Forkner, a former F.A.A. employee, was at the front lines of this effort. As the chief technical pilot, he was the primary liaison with the F.A.A. on training and worked on the pilot’s manual.

“The pressure on us,” said Rick Ludtke, a cockpit designer on the Max, “was huge.”

“And that all got funneled through Mark,” Mr. Ludtke added. “And the pushback and resistance from the F.A.A. got funneled through Mark.”

Like others, Mr. Forkner may have had an imperfect understanding of MCAS.

Technical pilots at Boeing like him previously flew planes regularly, two former employees said. “Then the company made a strategic change where they decided tech pilots would no longer be active pilots,” Mr. Ludtke said.

Mr. Forkner largely worked on flight simulators, which didn’t fully mimic MCAS.

It is unclear whether Mr. Forkner, now a pilot for Southwest Airlines, was aware of the changes to the system.

Mr. Forkner’s attorney, David Gerger, said his client did not mislead the F.A.A. “Mark is an Air Force veteran who put safety first and was transparent in his work,” Mr. Gerger said.

“In thousands of tests, nothing like this had ever happened,” he said. “Based on what he was told and what he knew, he never dreamed that it could.”

The F.A.A. group that worked with Mr. Forkner made some decisions based on an incomplete view of the system. It never tested a malfunctioning sensor, according to the three officials. It didn’t require additional training.

William Schubbe, a senior F.A.A. official who worked with the training group, told pilots and airlines in an April meeting in Washington, D.C., that Boeing had underplayed MCAS, according to a recording reviewed by The Times.

“The way the system was presented to the F.A.A.,” Mr. Schubbe said, “the Boeing Corporation said this thing is so transparent to the pilot that there’s no need to demonstrate any kind of failing.”

The F.A.A. officials involved in training weren’t the only ones operating with outdated information.

An April 2017 maintenance manual that Boeing provided to airlines refers to the original version of MCAS. By that point, Boeing had started delivering the planes. The current manual is updated.

Boeing continued to defend MCAS and its reliance on a single sensor after the first crash, involving Indonesia’s Lion Air.

At a tense meeting with the pilots’ union at American Airlines in November, Boeing executives dismissed concerns. “It’s been reported that it’s a single point failure, but it is not considered by design or certification a single point,” said Mike Sinnett, a Boeing vice president, according to a recording of the meeting.

His reasoning? The pilots were the backup.

“Because the function and the trained pilot work side by side and are part of the system,” he said.

Four months later, a second 737 Max crashed in Ethiopia. Within days, the Max was grounded around the world.

As part of the fix, Boeing has reworked MCAS to more closely resemble the first version. It will be less aggressive, and it will rely on two sensors.

Jack Nicas reported from Seattle, and Natalie Kitroeff, David Gelles and James Glanz from New York. Julie Creswell, Tiffany Hsu and Agustin Armendariz contributed reporting from New York. Kitty Bennett and Alain Delaquérière contributed research.

A version of this article appears in print on June 2, 2019 of the New York edition with the headline: The Late Change, And Fatal Flaws, In Boeing’s Plane. Order Reprints | Today’s Paper | Subscribe

[sansmoteur]

I don’t recall a lot of discussion in the various MAX threads about MCAS in high speed / high G scenarios, is its behavior there known?

[nevillestyke]

PR people, is this good PR, or is it just Boeing signing-off? At least they show that they're willing to look for short cuts.
https://www.youtube.com/watch?v=5j3ob0CfH9I

[gums]

Salute!

Thanks, Murphy, I just reverted to my old days. No offense to Hector. He say "toe-may-toe", I say "toe-mah-toe".

My first exposure to "manual electric trim" was when I had a backseat joyride in a T-33 in 1960. Up til then I had to crank a wheel for elevator trim and had no aileron trim gizmo. Hell, I learned on WW2 observation planes as a youngster in the late 50's. That T-33 "coolie hat" trim switch on top of the stick was a neat thing. A few years later my T-37 IP told me I wouldn't graduate high enuf to get a fighter unless I had a hole in my glove's thumb from trimming all the time. I never lost that habit, even in the Viper 20 years later when you only trimmed gee unless gear was down.

Gums sends....

[Dee Vee]

Boeing Built Deadly Assumptions Into 737 Max, Blind to a Late Design Change

One word explains it all, happens all the time, everywhere its implemented.

"Agile"

Just do it, test once, if it works once, push it out, bugs will be fixed in production by a different team.

[Bend alot]

Yes very interesting that NY times link.

Test pilots, engineers and regulators - do not seem to be pointing toward poorly trained third world pilots!

I was not me, I did not know seems what can be implied. That and - I'm seeing that bus you want to throw me under!

Seems Boeing has had cancer for quite some time, it has spread expediently and is still refusing treatment.

[RickNRoll]

You would think the 787 would have been a learning experience. Despite it's rocky start it is a very popular plane now and bringing in a lot of cash for Boeing. The battery problem was really all down to making sure that it was done right. They instead decided to assume the batteries from the supplier were all perfect and caused themselves a lot of needless pain.

[Water pilot]

The new news here is that "the MAX doesn't handle well in stalls at low speeds." So MCAS #2 was a bandaid to fix that problem, which is apparently a separate issue from the high angle of attack issue that we knew about, which was fixed by MCAS bandaid #1. Now the fix is to make MCAS less likely to trigger, what does that do to the low speed near stall handling?

Fingers are already being pointed. This probably came from Boeing's PR team, so the true story must be pretty bad. Were laws broken? The government tends to take the paperwork seriously, and this looks like a conscious effort to suppress information about the MAX's handling issues, which affects both the FAA and the SEC if they want to push it. Boeing seems to be positioning the blame onto one "rogue" flight tester, who now works for Southwest. "Oh no sir, nobody else knew about this change, or hardly anybody else and certainly not the CEO." That worked for Volkswagen for about -1 seconds.

Is it a typical career path for a top flight tester and former top FAA official to become a first officer?

[Bend alot]

Water Pilot.

Band-aid # 1 - introduce MCAS at 0.6 degrees from design estimates.
Band-aid # 2 - increase speed and travel of MCAS to 2.5 degrees, and a few other changes to fix the "opposite end of envelope" unforeseen issues.
Band-aid # 3 - tell pilots that MCAS exists and supply a vague reference about trim runaway procedure with a "note" that it could be a good idea to trim to neutral, before hitting the cutouts.
Band-aid # 4 - change the position, colour and shape of band-aid # 2.

But the big problem is that almost every day a new wound is being discovered, I expect much more is to follow.

[568]

The new news here is that "the MAX doesn't handle well in stalls at low speeds." So MCAS #2 was a bandaid to fix that problem, which is apparently a separate issue from the high angle of attack issue that we knew about, which was fixed by MCAS bandaid #1. Now the fix is to make MCAS less likely to trigger, what does that do to the low speed near stall handling?

Fingers are already being pointed. This probably came from Boeing's PR team, so the true story must be pretty bad. Were laws broken? The government tends to take the paperwork seriously, and this looks like a conscious effort to suppress information about the MAX's handling issues, which affects both the FAA and the SEC if they want to push it. Boeing seems to be positioning the blame onto one "rogue" flight tester, who now works for Southwest. "Oh no sir, nobody else knew about this change, or hardly anybody else and certainly not the CEO." That worked for Volkswagen for about -1 seconds.

Is it a typical career path for a top flight tester and former top FAA official to become a first officer?He (Mark) wasn't a "top flight tester" at Boeing.Anyone joining an airline has to join at the FO level due to seniority rules and work up.

[ProPax]

Not to say that there is never room for improvement, but such a drastic action would have to be reconciled with the fact that the 737NG has one of the best safety records of any commercial aircraft ever built.

The comfort of sitting on a powder keg is directly proportionate to the length of the fuse.

[fdr]

fdr #44,
Interesting views, no disagreement.

‘This particular deficiency is going to be more than a minor matter …’
It might be premature to discuss specific solutions for a deficiency which as yet is not clearly understood (at least publicly).
Elevator effectiveness, yes; but also in normal operation consider the combined horizontal tail surfaces - trim drag. What do you imply with TE tabs; corrective effect must overcome the failed trim condition, but not detract from normal operation.

Alternative thoughts could question why it was necessary to increase the tail area, yet retain the same size elevator. More trim range required whilst the pitch control appeared to be adequate.
The obvious longer, heavier, cg, arguments apply, but pitching moment with varying thrust levels could add another dimension.
Another question is why the trim range was chosen (horiz stab angles), is this relatively large, what are the limiting aerodynamic conditions; high, low speed, configuration, cg, thrust.
Have these changed with the evolving variants.
Background ref; https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-range.html

Increasing the span of the stab increases the tail volume for the stab system. It also increases the slope slightly of the CL/AOA curve for the stab and the elevator as a system. It does however as you have intimated, reduce the effective balance of stabiliser to elevator authority, which could be a problem. The increased slope may be a factor that is being observed in the creep of the trim in ET302, and if so, that will need some sober thought to resolve. I would think that a solution for a possible authority mis match between the stab and the elevator is resolved in the first instance with a T tab on the TE of the elevator, which markedly increases the control authority. That can also be achieved elegantly by a thicker TE section, much as is seen on some Airbus aircraft and others.The addition of wedges would achieve the same outcome. Any addition at the TE of a flight control comes with it's very own aeroelastic issues. Altering the elevator authority has considerable knock on effects in certification, but is doable. Another method of increasing authority is low profile VGs in the cove of the stab-elevator, that become exposed on deflection of the elevator. That sort of device only makes a difference when the control deflection has exceeded around 5-8 degrees of deflection, below that there is not much separation effect on the surface. Blowing is a viable solution as well and has very large authority change possible, but it would be a reliability headache for certification.

I think any potential problem in this area is able to be viewed from the other end, the stab manual movement needs to be reworked to permit manual control in all cases, or the industry has to dust off the old training information, and make sure that the crews are fully trained to deal with stabilisers that are defeated by air loads. Defeated, not immobile, as ET appears to show that the trim was creeping in the wrong direction all by itself, and that is not a happy place to be.

Alternatively, the industry will shrug it's shoulders, and look at the probability of the event and just suggest that the passengers be careful in buying tickets that are unlucky.

The article on the development of MCAS is depressing reading. Incremental change is usually reasonably safe, but only until trigger points are crossed. The problem is that the risk resulting from further change from known processes is not linear.

[ManaAdaSystem]

The NG handles well in low speed high angle of attack scenarios. For a NG to end up in a situation with near full AND trim (a situation where manual trim wheel operation is not possible) you need an unnoticed runaway trim for quite some time.
I have trained runaway trim in the simulator. A nose up trim is harder to notice since STS trims nose up, but you can turn the trim wheel manually in this situation.
A trim down will be noticed long before you get full AND. The runaway trim QRH procedure takes care of this problem.
The NG is safe.

[Bend alot]

The NG handled well in the simulator - but the real event apparently is very different from what most have experienced in the simulators.

Have they rectified that simulator trim wheel force issue on the NG & MAX simulators or is that work in progress?

[BDAttitude]

Yes very interesting that NY times link.

Test pilots, engineers and regulators - do not seem to be pointing toward poorly trained third world pilots!

I was not me, I did not know seems what can be implied. That and - I'm seeing that bus you want to throw me under!

Seems Boeing has had cancer for quite some time, it has spread expediently and is still refusing treatment.
Add a management who is of course not to blame, because they never asked for a unsafe product just a ever faster spinning cycle of 'make it faster', 'make it cheaper', 'we don't need no worrywarts, we need men of action', 'if you can't make it happen, there will be someone else who can'.
So we are now at the stage where the scrape goat subordinates come forward with their stories. I feel for them. They are going to have a hard time. Ask Mr. Oliver Schmidt from Volkswagen. Hopefully it will be beneficial for them to be US citizens.

[ManaAdaSystem]

The NG handled well in the simulator - but the real event apparently is very different from what most have experienced in the simulators.

Have they rectified that simulator trim wheel force issue on the NG & MAX simulators or is that work in progress?

What issue (NG) would that be? You can’t move the trim wheel manually in the NG sim with the trim fully forward and with strong aft pressure on the yoke. Low speed, high speed, it doesn’t matter.

[Bend alot]

What issue (NG) would that be? You can’t move the trim wheel manually in the NG sim with the trim fully forward and with strong aft pressure on the yoke. Low speed, high speed, it doesn’t matter.


The issue that the simulator trim wheel forces are lower than in the actual aircraft - so it is not a simulation, and we/most do not know at what stage the manual trim wheel will not be able to be moved ( near full forward or not far past natural, in seconds of a runaway trim). Given the manual trim wheel is hardly used in normal flight, most pilots I expect would be very surprised in the force required to move a moderate out of trim stabiliser. That comment based on known history and recent reductions in trim wheel size - they certainly did not make "it" easier to move!

This was a recent discovery, so your training may not be relevant in a real case of survival incident - but you would pass with flying colours in the simulator.

[safetypee]

fdr, #116, https://www.pprune.org/showpost.php?p=10484586&postcount=116 (https://www.pprune.org/showpost.php?p=10484586&postcount=116)
Thank you for the well considered views; interesting challenges.

A solution might require a combination of back-end and front-end fixes.
Adding relatively simple, low risk, minimum certification items at the back, ‘T’ strip, wedge, VGs, could restore the lost ability to move the trim wheel. Also can the severity of a trim runaway be limited (suggestions from other posters), less trim range, new - slower electric trim motor (then requires more, or predictive STS, autopilot issues).
I agree that change is never without risk, flight test surprise, or certification effort, particularly with an already highly modified variant aircraft, which may have less leeway for adjustment.

Front-end change should concentrate on the mechanics. What effect does the smaller trim wheel have, can this be changed, or the lever arm, or gearing be improved.
The human involvement might be the biggest challenge - the expected human contribution in mitigating high risk conditions; recognition, understanding, then choice of action. The accidents have challenged the fundamental beliefs in this area.

I disagree with the notion that the industry can turn the clock back. Even if the new variants are sufficiently similar to the original design, suggesting that trim runaway could be mitigated by training.
Times have changed (part of the problem). Piloting skill levels and range of experiences differ; not lower standards, but a sufficient standard to match the different challenges today, more complexity, more to know, to remember. People (pilots, regulators, manufactures) have not changed, but the conditions in which they work have, possibly with great effect.

‘shrug it's shoulders’, not to walk away. There is an interesting argument to be made re ‘the greater good’, which could differentiate action between the NG and Max.
After 9/11, reduced air travel resulted in more road deaths because of change of travel method, more than might be expected from aircraft accidents. Thus, NG grounding could be involve greater risk from change in travel than the continued risk in service.
Not so easy for the Max because of the relatively shorter time scale, the accidents, and public knowledge of the Boeing FAA situation - emotional effect. Fix the Max; MCAS done, but trim runaway requires a lot of effort.

We should not expect the FAA to judge a NG and Max split; however, the collective authorities might be able to, being the next best thing to a world opinion short of governmental agreement via ICAO, with political and time scale problems.
But we should not misjudge the fickle public opinion, swayed by media or politically motivated; I doubt a quick resolution in any area

[WHBM]

Concerns by operators over splits between different national regulators.

https://www.bbc.co.uk/news/business-48489082

It would seem if this has been "leaked", that the recent meeting of regulators over the issue was not conclusive.

If only Dennis Muilenburg was not so obviously beholden principally to Wall Street, leavened only by periodic "our first concern" statements which have all the hallmarks of being written by the legal and PR teams, along with what seem to be somewhat inappropriate and "pushy" statements about the FAA. Come on, Boeing board, we can all see it.

[RudderTrimZero]

Excellent article by the NYT

https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html#commentsContainer?register=google

[ProPax]

There is an interesting argument to be made re ‘the greater good’, which could differentiate action between the NG and Max.
After 9/11, reduced air travel resulted in more road deaths because of change of travel method, more than might be expected from aircraft accidents.

Thus, NG grounding could be involve greater risk from change in travel than the continued risk in service.

Driving deaths and injuries post-9/11
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3233376/

2001-to-2002 changes: fatalities rose by 112, fatal injuries - by 86, incapacitating injuries dropped by 14, "possible or non-incapacitating injury, or injury with severity unknown" dropped by 36.

Total deaths toll rose by (112+86=) 198.

Number of fatalities in LionAir 610 alone was 189. Add ET302, and the number grows to 349.

[Bend alot]

‘shrug it's shoulders’, not to walk away. There is an interesting argument to be made re ‘the greater good’, which could differentiate action between the NG and Max.
After 9/11, reduced air travel resulted in more road deaths because of change of travel method, more than might be expected from aircraft accidents. Thus, NG grounding could be involve greater risk from change in travel than the continued risk in service.


A number of years ago where I lived had NO SPEED LIMIT, and I regularly travelled at + 100 M/PH (160 K/PH).

Speed limits were then introduced to below 70 M/PH, the first year since the introduction of the speed limits had a very large increase in road fatalities.

Given the current situation/s grounding the NG may not be in the control of FAA and Boeing & that might spread to the other models. The 787 seems to have some other than battery and engine issues, that are being kept very quiet - hush money?

[BluSdUp]

With regards to the development and flight testing of the Max I would like to point out that Incompetence and Arrogance is never a good combination.

[Smythe]

The NYT article is very interesting on so many levels.

Test pilots validating in the sim only? Hopefully, something is lost in translation with the reporters. Makes me wonder if the "tests" Boeing stated it has done have been on the production ac or in the sim?

Also curious, according to the article, MCAS was supposed to use AoA and G force measurements. Unclear if MCAS as implemented included G-force or not.
In going back to the original intent or design of MCAS, does this include the G-force, to my knowledge, this hasnt been mentioned before as part of MCAS.

On flying again, damn...

Clark warned it could take six months to restore operations as other regulators re-examine the U.S. delegation practices - though U.S. majors have only suspended MAX schedules to August.

"That is why it is going to take time to get this aircraft back in the air. If it is in the air by Christmas I'll be surprised - my own view," he told reporters. Emirates' sister carrier flydubai is a major 737 MAX customer.

https://www.yahoo.com/news/2-airlines-want-joint-lifting-042835842.html

[ktcanuck]

If the NYT article is accurate Boeing found the lower speed stall characteristics of the Max to be unacceptable and prompted them to increase the effect of MCAS by 800% and to initiate the effect at a much lower speed.

The current fix that has been reported reduces MCAS effect back to the originally conceived stab movement rate. Has Boeing indicated how they will solve the lower speed stall characteristics by other means?

[Water pilot]

He (Mark) wasn't a "top flight tester" at Boeing.Anyone joining an airline has to join at the FO level due to seniority rules and work up.

According to the article (I know...) this person was responsible for the major redesign of the MCAS system based upon his input. He was also (again according to the article) the point man for FAA documentation on the issue, and if I read it correctly he is the one who convinced the FAA to allow Boeing to remove the mention of MCAS from the flight documents. You cannot convince me that an organization such as Boeing would make such dramatic changes based upon anybody who was not at the top of the flight test food chain.

To be honest I do find the sequence described in the article a little hard to believe; they imply that it was test that came up with the engineering solution which is pretty rare in my experience, but I don't work with aircraft. I feel that there is a goat named "Scape" somewhere in this story.

[VFR Only Please]

If this whole unmovable trim wheel kerfuffle plays out to its full potential, Boeing is staring down the barrel of BOTH MAX and NG being grounded. And that might very well be the end not only for the 737, but for the Boeing Company. I'm not even sure their military division will be able to bail them out, unless they quickly disconnect the two parts but that would require a shareholders meeting which won't be quick. (Correct me if I'm wrong.)

So, just hypothetically, wouldn't it be safer for Boeing to simply close the 737MAX program, cut their losses, buy back the MAXes and try to cuddle the FAA into stopping the NG trim wheel inquiries? They could then concentrate on NSA, or NMA, or MOM, or whatever it is they want to do. They would likely come out of this way behind Airbus in sales and customer trust, and will have to fight back into that market, AND they have very little experience in that kind of marketing. It will be a HUGE loss and an enormous effort. But, IMHO, it's the lesser evil. The more this drags on, the less likely Boeing is to come out of this alive. As much as I like Airbus, I don't want them to be an unopposed monopolist.

I've basically asked this same question before: At what point does this become a dead horse they're flogging here? And the deader it gets, the worse it smells. And the worse the PR.

Unfortunately it apparently goes beyond the 737. My apologies if this 48-minute documentary has been posted before -- if so, I missed it. It was published several years before the MAX began delivery and has to do with the 787. But what it's really about is Boeing management these days. (And yes, a Boeing / Airbus duopoly is preferable to an Airbus monopoly.)

What do I know? Perhaps Boeing has just been lucky with the 787. Or could it be that fasteners hammered home any-old-how by drug-addled employees under deadline pressure require dozens of thousands of hours and cycles before they finally fail, having maybe escaped detection in D-checks? But when a 32-year veteran Boeing engineer says she wouldn't fly on the 787, that has to mean Something.

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

[DieselOx]

The view from outside looking in: Boeing needs to start over, design a new clean slate single aisle. All this fussing around on how to thread this needle is wasted effort, lipstick on a pig.

I, and I suspect most of the public, still have a foundation of trust toward Boeing, even after how the 787 launch occurred, for everything up to the MAX, but how they handle this could erase it all.

Down playing anything= trust gone. Blaming anyone outside Boeing= trust gone.

(What gobsmacks me most about the NYT article is how casually MCAS came into existence, and how casually it was implemented.)

If Boeing did their strategy right, the MAX is a neutralization innovation in the market, intended to level the playing field in the short term, which only works if they simultaneously started development of a disruptive offering, a new clean slate single aisle. So they should be only 2-4 years away from launching that new one, right?

[edmundronald]

SLF, engineer and ex-college teacher here.

Based on the NYT article, it appears Boeing has "technical pilots" who write checklists, manuals and instructional materials. But the accountants at Boeing barred these "technical pilots" at Boeing from flying (did they keep their licenses current?) and so the "technical pilots" based the Max instruction manuals they wrote on the NG-derived sims, which of course do not evidence the significant force necessary to manually trim using the small NG trim wheels, especially at speed.

This is going to go down in the annals of computer simulation methodolgy as a textbook teaching case of method failure, reliability engineers breathing their own exhaust and considering their own simulator as a valid replacement for the physical thing for safety validation. The unfortunate fact is that both Boeing and the FAA should have a technical process in place for ensuring that emergency checklists and procedures are validated against the real thing and not just the sim. My own feeling is that every list important enough to be memorised should be checked in the air. The fact the FAA did not do this for certification means that it will now be necessary to go over all the Max and possibly even NG checklists with a fine tooth comb to look for other cases where the real world might -so very inconveniently- diverge from a well-behaved simulation.

The farce is now such that one does wonder where incompetence stops and full-bleed corruption has taken over. Even the NYT clearly smells a dead rodent.

Edmund

[ProPax]

Could someone please explain what is the difference between "test pilot" and "technical pilot"?

[derjodel]

article from NYT on the foundation of MCAS...very interesting

https://www.nytimes.com/2019/06/01/business/boeing-737-max-crash.html

wow, if this article is correct, MCAS _is_ an anti-stall system. That changes everything. It’s a system designed on purpose to continously trim down based on a single aoa input _to prevent stall_.

[Smythe]

From Job announcement SEP 2017: (this is the Chief position, so...a qual as a Cpt)

747 Chief Technical Pilot

Boeing Commercial Airplanes (BCA) has an exciting and unique opportunity for a 747 Chief Technical Pilot to join our Commercial Aviation Services team.
This team support a variety of training and flight services for commercial airplanes and their customers around the world.
As a Chief Technical Pilot you will perform as a chief technical consultant on the 747. In this role you will provide flight operations, safety and technical support to Boeing internal and external customers at multiple levels. While this role is not primarily a flying job, the selected applicant will still maintain qualification as a Boeing Captain on at least one aircraft model.
Other responsibilities include:

Supports new aircraft and system development and certification efforts.


Develops and validates procedures and operating techniques and assists other Technical Pilots with cross-model procedures.
Provides information and specialized technical services to Company and customer flight crews to enhance flight operation efficiency.
Consults with cross-functional teams during accident investigations and analysis as needed.
Researches, edits, documents and coordinates publication of procedures and techniques for operating Boeing aircraft.
Represents Boeing as a technical lead by authoring and presenting professional papers at worldwide safety and flight operational forums.
Meets with regulatory agencies at the executive level.
Supports sales campaigns by discussing and demonstrating airpcraft and new flight technology.
Serves as a consultant to senior management and other industry professionals.
Works under minimal direction.
Test Pilot, well, that is the flying position.

FAA Test Pilot job announcement:

Flight Test Pilot (FTP) with primary responsibilities to ensure type certification of the performance, stability, and control requirements including envelope expansion, handling qualities and performance of new or modified Title 14, Code of Federal Regulations (CFR) Part 23 and/or Part 25 aircraft.

Incumbent serves as a Flight Test Pilot (FTP) with primary responsibilities to ensure type certification of the performance, stability, and control requirements including envelope expansion, handling qualities and performance of new or modified Title 14, Code of Federal Regulations (CFR) Part 23 and/or Part 25 aircraft.

Responsible for the flight test compliance of the type certification processes for avionics, propulsion, and mechanical/electrical systems and equipment installations on those same aircraft.

The FTP conducts qualitative and quantitative flight tests and evaluates engineering data on modified and new type design aircraft to oversee and spot-check applicants' compliance showings for applicable airworthiness requirements.

The FTP also applies expertise and experience to recommend improvements to internal/external processes related to certification and organizational issues.



In my organisation, we have plenty of technical pilots who only have the college degree, with no actual experience flying a commercial aircraft. They get typed in the sim, that is about the extent of it for most.

Usually they are working the sim on the RNAV/VNAV procedures to check for any issues, temperature limits, weight limited OEI procedures, and especially temporary obstacles. (ie verifying NOTAMs)

There are levels where the ATP and 1500 hrs is the minimum...that being said, even with those quals, it is not a flying position.

[GordonR_Cape]

The following story popped up in my news feed: https://www.reuters.com/article/us-boeing-faa-airplane/some-boeing-737-max-planes-may-have-faulty-parts-faa-idUSKCN1T30RX
The U.S. Federal Aviation Administration said on Sunday some Boeing Co 737 MAX and NG planes may have parts that were improperly manufactured and that it will require their replacement
The FAA said up to 148 leading edge slat tracks manufactured by a Boeing sub-tier supplier are affected and cover 133 NG and 179 MAX aircraft worldwide.

Edit: Sorry, only quoted the first part of the story:
Boeing, the world’s largest plane maker, said it has identified 20 737 MAX airplanes most likely to have the faulty parts and that airlines will check an additional 159 MAXs for these parts.
Boeing said one batch of slat tracks with specific lot numbers produced by a supplier was found to have a “potential nonconformance” and said airlines “are to replace them with new ones before returning the airplane to service.”


Edit: Parallel thread created around the same time as my post: https://www.pprune.org/rumours-news/622123-boeing-notifies-faa-parts-max-other-737s-may-susceptible-premature.html

[ProPax]

Oh, joy! How long does it take the MTX to replace the slats, per aircraft?

[edmundronald]

Oh, joy! How long does it take the MTX to replace the slats, per aircraft?

On the bright side, replacing parts won't impact revenue from the MAX. :)

Edmund

[Smythe]

On the bright side, replacing parts won't impact revenue from the MAX. :)

Edmund
exactly the issue, every AD will make the news, even though there have always been many, the public didn't know (or cared)

[FrequentSLF]

The following story popped up in my news feed: https://www.reuters.com/article/us-boeing-faa-airplane/some-boeing-737-max-planes-may-have-faulty-parts-faa-idUSKCN1T30RX
Something wrong with the numbers 300 planes affected by 148 parts?

[RickNRoll]

Something wrong with the numbers 300 planes affected by 148 parts?

Might not know which plane they are on till you check them individually.

[patplan]

The following story popped up in my news feed: https://www.reuters.com/article/us-boeing-faa-airplane/some-boeing-737-max-planes-may-have-faulty-parts-faa-idUSKCN1T30RX
(https://www.reuters.com/article/us-boeing-faa-airplane/some-boeing-737-max-planes-may-have-faulty-parts-faa-idUSKCN1T30RX)The FAA said up to 148 leading edge slat tracks manufactured by a Boeing sub-tier supplier are affected and cover 133 NG and 179 MAX aircraft worldwide.



The defective parts which had affected 179 Max'es?? That's more than half of the Max'es in operation. Another question: the defective parts had not been installed in either PK-LQP or ET-AVJ, had they? I don't like the odd. The chance of any random Max'es got affected by the defect is bigger than 50:50.

[bill fly]

Oh, joy! How long does it take the MTX to replace the slats, per aircraft?

The slats are OK. It is some tracks which will need replacement. 2 day down time was quoted on CNN news - presumably after delivery of heat treated parts.

[ManaAdaSystem]

The issue that the simulator trim wheel forces are lower than in the actual aircraft - so it is not a simulation, and we/most do not know at what stage the manual trim wheel will not be able to be moved ( near full forward or not far past natural, in seconds of a runaway trim). Given the manual trim wheel is hardly used in normal flight, most pilots I expect would be very surprised in the force required to move a moderate out of trim stabiliser. That comment based on known history and recent reductions in trim wheel size - they certainly did not make "it" easier to move!

This was a recent discovery, so your training may not be relevant in a real case of survival incident - but you would pass with flying colours in the simulator.

No training, we just tried out various stab settings and speeds vs manual trim.
I imagine manual trim can be impossible at nearly any stab settings. It’s all about the load on the stab.
This is a 737 issue since none of the other aircraft I have flown have had a manual trim wheel like the 737.
Had Boeing removed the trim wheel on the Max and made it electric only, we would not have this discussion.
I have no worries about the NG. I have never had a runaway trim. I have never had an AOA fail.

*Knock on wood*

[yanrair]

Salute!
Thanks Bend and PEI.
I just have a hard time with Boeing not keeping the manual electric trim operating when MCAS does its trick.

Looks like Boeing is sticking to the "existing procedures would have prevented the crashes" story. Ditto for some of the uber pilots here. Problem is recognizing what is wrong and the magnitude/length of the MCAS commands.

PEI might be able to explain it in technical terms that some here will not fathom, but I say go for it.
- Why can't the trim commands be a function that uses "q" and mach as we did in the Viper instead of a "bang-bang" fixed amount and fixed time of application? In other words, follow a geometric plot as we did for AoA versus gee and control deflection gains.
- If MCAS is using the A/P circuits, why disable other force functions such as the control column switches for force ( not the electric switches).

Gotta be nore than meets the eye, and I do not feel training is the answer. Fer chrissakes, we are not training Top Gun fighter pilots or NASA astronauts.

Gums sends...
Hi there Gums. Always enjoy your posts which throw up interesting points
Think this is the core of the problem. My view is that the pilots I grew up with were the top guns of the civil world. They needed to be. B747 quadruple engine failure. b744 turned upside down by intruder and lost 2 miles altitude in 90 seconds. Sioux City. Hudson River + a thousand more. All flown to the a safe landing, or least worst outcome as per Sioux City.

So, Boeing fix MCAS and make sure you can trim STAB in all realistic scenarios. Done already I would imagine. Software + hardware fixes. Awaiting the politicians and spin doctors on both sides - ah! And lawyers, to release plane for service.
So alls we’ll then. Back to “normal”. Well no. Because we’ve been going down a path for some years of downgrading pilot training to the point where the only time they are really needed- when automatics fail badly, they can’t cope.
A daily example and exception is xwind landings which currently automatics can’t do > 25 kts wet. Max wind 30:kts.
But they practice it so often that’s ok.
But given an ET style multiple failure scenario, or QF Ex SIN they have nothing to fall back on. And unless our engineer friends can produce a crash proof plane, dream on, this is going to get worse.
so the nightmare facing the industry and regulators is not MCAS or STAB issues. It’s the thousands of pilots already out there like this, and the 30,000 needed over next few decades.
My view? Bite the bullet and train them. But, the core of the problem is there aren’t enough of them with the “right stuff” to be trained. Start up airlines popping up and just buying “”:buses with wings” and some xbox guys to fly them.
In my airline (one of...) it took 10-15 years 10,000 hours to be put in command. And boy were you glad when the unexpected was thrown at you.
But I hear some say”get that dinosaur off this forum before my brain explodes with anger and indignation! “
Isn’t there a forum for old farts that he could join? Where he can dream of halcyon days when pilots could fly a plane with stick and rudder and a thing called airmanship? And think outside the box and understand the systems enough to know right from wrong?
I will tootle off now and take my blood pressure pills.
Y
Im looking for one,

[alf5071h]

yanrair,
“My view? Bite the bullet and train them. But, the core of the problem is there aren’t enough of them with the “right stuff” to be trained.”
You appear to exclude yourself - ‘train them’, but no training for you. Retired ? But you still need to train your mind.
When would the industry reach the required standard, who would judge, how.

alf, … just ‘an old f…’, but prepared to consider alternative views, consider what the industry’s current safety needs are, and how they could be met - practical, cost effective.

[PiggyBack]

Hi there Gums. Always enjoy your posts which throw up interesting points
Think this is the core of the problem. My view is that the pilots I grew up with were the top guns of the civil world. They needed to be. B747 quadruple engine failure. b744 turned upside down by intruder and lost 2 miles altitude in 90 seconds. Sioux City. Hudson River + a thousand more. All flown to the a safe landing, or least worst outcome as per Sioux City.


The thing is that however good the legendary pilots of yesteryear it is far safer now than in the past. I think there is a lot of selective memory and golden age fallacy going on.

I am not going to rehash the problems with MCAS but this was clearly behaviour of a system in the event of a single fault with a probability of a catastrophic outcome that was not small. You can argue that in the past the excellance of pilots meant that they would on average have handled it better, but it is irrelevant, it would still have a significant chance of causing a crash and it would still be considered an unacceptable design that must be rectified.

[ManaAdaSystem]

My cockpit is full of protective systems that got developed because of past years top gun pilots who flew their aircraft into the ground, crashed with other aircraft or flew straight into thunderstorms.

[gums]

Salute!

As one of the "legendary" pilots of yesteryear along with yan and others,,,,,,,,,,

We would not be commenting/contributing here if we were just plain "lucky". As one of my mentors told me early on, "luck is when preparation meets opportunity". We encountered many problems to get here and we are still alive to comment, lucky or not. I prefer "or not".

Did our training help? You bet your a$$$.
Did we have great IP's? Ditto
Did most of us have good "hands"? Pretty sure I had/have. Too many flights when asking Joe Baggodonuts student "can you feel that?" "Feel what?". Gasp, this was gonna take some time......... Believe it or not, but I gor a poor grade in the T-37 for stall/spin entry! I protested, claiming that I was not supposed to stall or spin. Intentionally stalling and spinning wasn't high on my priority list, heh heh. I resented the buffet and wing rock you encountered when pulling back on the stick and then putting in rudder at the stall. Sheesh.

So I support the folks here that like better training. At the same time, I do not appreciate the Yeager types here that claim "Oh yeah, if that were me there would be no problem".

You do not know the problem until something you least expect happens when you least expect it, and there is no memory item to mitigate the situation. You must rely upon past experience and mental exercises you did when sitting in the barber chair or waiting for your physical blood test or...... I used those stoopid times to imagine a problem and what I would do. Worked for me......
+++++++++++++++++++++
I do not like a kludge soulution to the 737 MAX handling characteristics at high AoA, and those are below the stall AoA.

IMHO ( not so humble), Boeing needed an aerodynamic solution and not an bandaid that could activate when they least expected it to activate. And then remove the manual electric trim if the crew followed the procedure!!!

Gums sends....

[sky9]

OK just an old fart but:
In the 1970's the company I joined demanded 2000 to sit in the right hand seat of a 737 and 5,000 for earliest move into the left.
Currently how many hours to sit in the right seat (the Ethiopean F/O Ahmed Nur Mohammod Nur, 25 had 361 hrs) and how many airlines now consider that 2000 hours is sufficient experience for the LHS.

[Banana Joe]

My airline has a minimum requirement of 1500 hours and minimum time in the company of 5 years.
Ryanair have a minimum requirement of 2900 hours.

[gums]

Salute!

To be very honest, I would want to know how many landings and approaches and shorthaul routes like the regional folks do versus the 6 or 8 hours of monitoring the gauges and then only taking the wheel for the flare, rollout and such.

If possible, I would also like to know how many hours flying with the A/P disabled and the FMS doofer FUBAR. You know the drill ....pull out all those charts and tune the nav stations and..........

Gums....

[Vilters]

@ Gums
Exactly, you put the hammer to the nail.
This automatization to take the "stupid" pilot out of the loop has gone too far. When the system fails, he simply does not know what to do any more.
One faulty wire, one loose connection, is all it takes to get the system out, and the pilot has no clue where, what, how.
Certainly when that "fail-safe" system starts giving contradicting information, and even more so when the pages of errors go so fast on and off screen that even a robot could not track all of them.

And we are doing the same thing in cars.
Gruise control
Automatic lane keeping
Automatic braking
Night vision
And when the system fails? ? ? We continue to being passengers wondring what is happening till impact.

In a previous post you talk about "feel" .
Where feel, what feel, with a digital control system?

PS; the 16 is the same thing. Where feel, what "feel"? I will always remember the loss of another one of our "B" models.
Ran out of speed, nose vertical up at 18.000ft, pilots looking outside at bandit during a BFM (Pilots survived after ejection at 6.000 ft)
There is no "feel" with the surfaces pressures in a digital airframe.

[radken]

A June 2nd front page Seattle Times article goes “Fateful 737 MAX revamp left key players in the dark.” The sub-head says “Critical decisions on design certification were based on misguided assumptions.”

The article is devoted 100% then to the proposition that the MAX’s “fatal flaws” have been “traced to a breakdown late in the plane’s development, when test pilots, engineers and regulators were left in the dark about a fundamental overhaul to an automated system that would ultimately play a role in two crashes.” No mention is made of the ships new, larger, more powerful engines, and their placement vis a vis the airframe, as the true and FUNDAMENTAL cause of why the MAX flys “differently” at times than any of its brethren. So differently, in fact, that an entirely new system had to be invented to cope with what Boeing is subtly admitting is a major and certain “aerodynamic” (as Gums says) shortfall.

But as for test pilots being left in the dark? Far from it I would venture. The latter would have been first to witness the new “bucking bronco” do her “characteristics” thing as she kicked up her heals to their spurs. Unless they’d been warned what maybe to expect (?), it must have been pretty unsettling. But that would be another story.

[Maninthebar]

But as for test pilots being left in the dark? Far from it I would venture. The latter would have been first to witness the new “bucking bronco” do her “characteristics” thing as she kicked up her heals to their spurs. Unless they’d been warned what maybe to expect (?), it must have been pretty unsettling. But that would be another story.



That is an interesting speculation, and you have good reason to expect it to be true. BUT, if there had been test flights under the original development program in which MCAS was caused to activate erroneously and the pilots recovered the situation gracefully then I am certain that Boeing would have quoted the flight data by now.

As no example of successful recovery from erroneous MCAS activation in flight HAS been publicly given I am assuming that none had occurred prior to the JT and ET tragedies

[yoko1]

But as for test pilots being left in the dark? Far from it I would venture. The latter would have been first to witness the new “bucking bronco” do her “characteristics” thing as she kicked up her heals to their spurs. Unless they’d been warned what maybe to expect (?), it must have been pretty unsettling. But that would be another story.


The test pilots test flew the conditions for which MCAS was designed - an approach to stall. By all accounts MCAS performed as desired.

What they did not do, and what they may not have understood as being possible, was test fly the scenario where MCAS activates due to an erroneous AOA sensor input.

[Maninthebar]

Thank you Yoko, that is my assumption also.

So, a question for those fluent in Certification, is there a requirement to demonstrate that the failure of a single component should result in a flyable aircraft?

If so the (and pace many pages of discussion with regard to whether the 'frame WAS flyable after an erroneous activation) the fact that it has not been demonstrated ought to have been a limiting factor. I assume here that the FAA had previously been satisfied that the failure of a single AOA vane would not trigger a dangerous condition.

[yoko1]

So, a question for those fluent in Certification, is there a requirement to demonstrate that the failure of a single component should result in a flyable aircraft?



I think the more germane question is whether anyone actually realized that a single-point failure had been introduced into the design after all the modifications. It appears that there were too many chefs with a hand in the MCAS design and no one stepping back to give it a thorough top to bottom review. We would like to think that during the design phase someone would have seen what has now become obvious to everyone, but given the time pressures and compartmentalization built into the process, I can also see how this might have been missed.

[Smythe]

In reading the NYT article, the test pilots comments struck me as rather humurous..

Old school Boeing test pilot: aircraft doesnt feel right, add vortex tabs.

Millennial Boeing engineer: aircraft doesnt feel right, add software.

Another observation, from the onset, we were lead to believe MCAS was needed due to lift from the engine nacelles at high angle of attack. If the NYT article is correct, the test pilot noted issues with low speed stall.
It also noted that the original MCAS had G force component (that was removed) so that would encompass a whole additional set of conditions or parameters.

Reading and wordsmithing the Boeing press releases on testing the software fix, and waiting for FAA approval for a validation flight, leads me to believe that much of the "testing" is being done in the sim.

If all of this is correct, then this does not appear to me to be a simple software and/or minimal training adventure.

[b1lanc]

compartmentalization

Key word. The KC-46 team recognized the potential. I can't speak for information sharing within Boeing between development teams. Be curious to know if the MCAS software between the two platforms was designed/developed by the same team.

[derjodel]

Reading and wordsmithing the Boeing press releases on testing the software fix, and waiting for FAA approval for a validation flight, leads me to believe that much of the "testing" is being done in the sim.

This right there is one of the biggest issues in the whole story. How can you certify a plane according to its sim!?

[Maninthebar]

I think the more germane question is whether anyone actually realized that a single-point failure had been introduced into the design after all the modifications. It appears that there were too many chefs with a hand in the MCAS design and no one stepping back to give it a thorough top to bottom review. We would like to think that during the design phase someone would have seen what has now become obvious to everyone, but given the time pressures and compartmentalization built into the process, I can also see how this might have been missed.

.
It would have to been an oversight at original design of the software
That oversight would have to have been missed by whatever peer review process is invoked within Boeing
Missed when drafting submission for Certification
Missed by Certifying authority
Missed by Boeing when quantum of movement changed (speed/extent of stabiliser deflection) (to be fair this is probably the point at which it would have been least likely to have been spotted)

That's a lot of misses it seems to me. Your question is VERY pertinent and this Human Factors element of the investigation will be interesting to unpick

[Fly Aiprt]

This right there is one of the biggest issues in the whole story. How can you certify a plane according to its sim!?

Boeing guarantees, and everyone around agrees, that the 737 sim is perfectly flyable in case of MCAS event.
It's just that the airplane doesn't correctly replicate the sim...

[Smythe]

As was feared....

Boeing's (BA (https://seekingalpha.com/symbol/BA) -1.7%) 737 MAX jets likely will get the green light to fly again by the end of this year, CEO Dennis Muilenburg tells CNBC, while declining to provide a specific timetable.

The company is conducting simulated flights with air safety regulators this week and expects to fly the MAX with the Federal Aviation Administration "very soon" afterward to get the grounded plane cleared to return to service, the CEO says.

Boeing will work closely with customers to repair "damaged trust" of the flying public but this "will take time," Muilenberg says.

emphasis added....

[Maninthebar]

As was feared....

Boeing's (BA (https://seekingalpha.com/symbol/BA) -1.7%) 737 MAX jets likely will get the green light to fly again by the end of this year, CEO Dennis Muilenburg tells CNBC, while declining to provide a specific timetable.

The company is conducting simulated flights with air safety regulators this week and expects to fly the MAX with the Federal Aviation Administration "very soon" afterward to get the grounded plane cleared to return to service, the CEO says.

Boeing will work closely with customers to repair "damaged trust" of the flying public but this "will take time," Muilenberg says.

emphasis added....

Perhaps Muilenberg could use the example of Lauda and organise himself a ride with erroneous MCAS activation. That would both prove recoverability and demonstrate confidence.

After all, if he wont do it, why should any of the rest of us?

[formulaben]

Perhaps Muilenberg could use the example of Lauda and organise himself a ride with erroneous MCAS activation. That would both prove recoverability and demonstrate confidence.

After all, if he wont do it, why should any of the rest of us?

Absolutely! Anything short of this is disingenuous.

[gums]

Salute!

"As was feared....." Uh huh. No need to see the real deal. No need to conduct tests that fail things in conditions that the engineers never thot of. You know...... at high alpha ( not speed!!!!).

Chuck Wannabe, "this new plane has a light stick when close to the stall"
.
Non-pilot engineer, "No problem, we can crank the stab up a bit so it's harder to pull back to a higher AoA ( NOTE!!! not speed, but AoA). In all the Boeng FCOM stuff I have accessed, the term "speed" is used lots more that AoA. yet MCAS and the stall shaker use AoA as the primary driver. Even STS is named "speed xxx xx" Yet AoA in most condiitions determines the need for trim, or am I too old? And isn't AoA that determines stall regardless of gee or true airspeed or bank angle or.......

Pilot, "errrr, what about the elevator feel system, won't it make it harder to pull back ?".

Engineer, "nope. apparently moving motors and doing other stuff reduces longitudinal pitch moments when a few degrees AoA below stall., and the feel system uses airspeed more than AoA"

Pilot, "why use the stab to increase back stick force versus the existing elevator feel sytem that affects the column?

Engineer, "well, the EFS uses speed more than AoA. You know, the old dynamic pressure we call "q" that the FBW folks use for what they call "gains" and you guys call indicated airspeed or pounds per foot squared or ..... there must be fifty ways......"

Pilot, "Oh, but what about the increasing back column force if the AoA is really high, and not just due to "q"?"

Engineer, : Hmmmmm...... may have to fly another test flight or two or three........"

Gums sends...
P.S. Wait until you see my questions at the trials of the survivors WRT mis-management and possible negligence resulting in a few hundreddeaths. @ mods..... maybe need a thread over on Tech Log, huh? We all appreciate your patience and apolitical stance thus far in this debacle. Salute!

[WHBM]

Boeing's (BA (https://seekingalpha.com/symbol/BA) -1.7%) 737 MAX jets likely will get the green light to fly again by the end of this year, CEO Dennis Muilenburg tells CNBC, while declining to provide a specific timetable.
Is that the first we have heard of this date now from official sources ? December ?

https://www.cnbc.com/2019/06/03/boeing-plans-to-fly-a-boeing-737-max-certification-flight-soon-ceo-says.html

[GordonR_Cape]

Is that the first we have heard of this date now from official sources ? December ?

https://www.cnbc.com/2019/06/03/boeing-plans-to-fly-a-boeing-737-max-certification-flight-soon-ceo-says.html

The Emirates airline president Tim Clark dropped a big hint at the recent IATA meeting: https://www.reuters.com/article/us-airlines-iata-emirates-boeing/airlines-want-joint-lifting-of-737-max-ban-but-eu-cautious-idUSKCN1T301Z
Clark warned it could take six months to restore operations as other regulators re-examine the U.S. delegation practices - though U.S. majors have only suspended MAX schedules to August.

“That is why it is going to take time to get this aircraft back in the air. If it is in the air by Christmas I’ll be surprised - my own view,” he told reporters.

[VFR Only Please]

The thing is that however good the legendary pilots of yesteryear it is far safer now than in the past. I think there is a lot of selective memory and golden age fallacy going on.

I am not going to rehash the problems with MCAS but this was clearly behaviour of a system in the event of a single fault with a probability of a catastrophic outcome that was not small. You can argue that in the past the excellance of pilots meant that they would on average have handled it better, but it is irrelevant, it would still have a significant chance of causing a crash and it would still be considered an unacceptable design that must be rectified.

And if you look at the legendary crashes of yesteryear, quite a number were caused by flightdeck negligence. Need I recite them?

OK just an old fart but:
In the 1970's the company I joined demanded 2000 to sit in the right hand seat of a 737 (...).
Currently how many hours to sit in the right seat (the Ethiopean F/O Ahmed Nur Mohammod Nur, 25 had 361 hrs) [...].

But if the '70s F/O had spent 1,000 hrs teaching amateurs like me to fly single-engine VFR and the Ethiopean F/O had gained 150 hours as part of training at a flight academy for airline pilots, which of these sums is the better preparation for the job?

I've heard there are today 200-hr pilots out there flying nuclear-armed aircraft. If true, what does that mean?

[gums]

Salute!

Careful there, VFR.

Lottsa difference in supervision and such besides total flying hours for the military folks. Figure about 200-250 hours of military training and then to the buff or nuke capable attack plane. Oh yeah!!! How many hours do the missile folks have that sit 100 feet underground and can launch a dozen ICBM's?

In my own case, I had about 500 military hours when I first sat nuclear alert up north waiting for the horde of Bears and Bisons destined for Chicago, Kansas City, St Paul, Detroit, and such - the "central flyway".No offense to our Russian folks here, as we all know what was going on back then 50 years ago. I was an Air Defense Command interceptor pilot.

The difference is that the military crew is not flying a nuclear mission several times a week and has tons more supervision and cross checks than a nugget civilian regional route pilot.

So let's get back to the issue here that will have a dramatic influence on all commercial aircraft development and testing. Huh?

Make no mistake. The Boeing 737 MAX certification process and their engineering solution of an aerodynamic problem is gonna have a long lasting and serious impact on Boeing as well as the entire commercial industry. Just me speaking.

Gums sends...

[Smythe]

When in doubt , add vortex
tabs

[BluSdUp]

Just for the record , there is 125hrs pilots starting the Line training in Europe as we speak.
Many are good , most are not.
All are up to standard and the standard is to low.

Do not confuse this with Military training, please.

So ,how come FAA demands 1500hrs for 737 and Europe 120hrs.
Trust me , it is not a good idea!

BTW
I am looking forward to see the Max training requirement.
Ps Training is defined as Sim or Flight, can anyone tell Boeing and the Authorities!

Regards
Cpt B

[fdr]

When in doubt , add vortex
tabs

it often appears to be the solution, but not so much in this case.

VG's generally control separation, or introduce shock forming structures into the boundary layer.

The general problem with the Max is change in the Cp on the wing around the engines at varying AOA, that is the result of the lift being generated by the nacelle. There may be some interference effects from the nacelle at low AOA that add to the relative shift and that would be able to be altered by VGs, but otherwise not going to do much there. A possible solution would be to reduce the strake effectiveness on the nacelle, but that comes with total lift penalties over that gained at present for modest AOA values.

The Stab itself is not going to benefit from VG's.... The elevators may, for low profile VGs that are well forward on the elevator surface, which would improve elevator authority at high deflections, but then that also results in a load change that may affect the existing stick force per G which is the symptom that is being dealt with. Increasing elevator authority can improve the controllability against a jammed stabiliser, but that does not benefit directly freeing up the stabiliser itself when it has become immovable due to aero loads when using manual trim. Trailing edge tabs, as T, L's or ramps increase the elevator authority (thickening the TE), but that is the same outcome, improved control margin over the jam, but no change to the immovable stab case directly. Presumably sufficient elevator authority would permit getting the plane to a condition where the crew can then unload the control system sufficiently to permit manual trim in the period that the aircraft is following the incorrect trim. Maybe.

VGs' are not certainly the solution in this case, there is a fair bit of CFD needed to sort out the underlying issue, and then a whole bunch of playing with the subsequent control forces to ascertain the real extent and solution of the problem, if, and only if it is considered that having a stab that cannot be controlled due to excessive airloads in manual mode is a bad thing. I still think it is, in the absence of training and analysis of the operational envelope safety that comes along for the ride of this phenomena.

The kludge is that the operators should be aware of the issue, and should ensure that they never get that far out of trim, but sods law is that crews won't stay in that area at all times. As it is an underlying characteristic of the design of the B737 particularly, where a manual backup exists, then it is a product related issue, but, I hazard to guess that the fundamental issue of a locked stab from airloads floats nearby all trim systems, and the margin in actuator force required would bear looking at for other types as well to ensure that the emperor has clothes.

[Smythe]

Engineer, : Hmmmmm...... may have to fly another test flight or two or three........"

Correction: Hmmmmm...... may have to sim test another flight or two or three....

@fdr...I was being factitious. In reference to the NYT article, the test pilot found the aircraft had issues with low speed stall...he recommended adding VG...engineers said software..

my point being, in the beginning, the 747 had low speed stall issues on initial test flights, they added vg tabs to the wings as a 'temporary measure". (and never left)
now, vg tabs continue on Boeing wing designs, as well as showing up in odd places as 'fixes' such as in front of the windscreen....

hence my comments..

Flight test shows stall issues....

Old school Boeing test pilot: "add vortex tabs"

Millennial engineers: 'add software"

Where does the part about "design wings correctly" come in?

[neville_nobody]

Where does the part about "design wings correctly" come in?

That's the heart of this whole issue, there is no design. If this was a clean sheet aircraft none of the problems with the MAX would have existed

[PiggyBack]

.
It would have to been an oversight at original design of the software
That oversight would have to have been missed by whatever peer review process is invoked within Boeing
Missed when drafting submission for Certification
Missed by Certifying authority
Missed by Boeing when quantum of movement changed (speed/extent of stabiliser deflection) (to be fair this is probably the point at which it would have been least likely to have been spotted)

That's a lot of misses it seems to me. Your question is VERY pertinent and this Human Factors element of the investigation will be interesting to unpick

There were a lot more misses than this starting with the specification of the MCAS system itself. Often this sort of issue is caused by a change the effect of which is not fully assessed and understood invalidating an earlier safety analysis. I am really just speculating but in this case it seems to be change after change after change without a fundamental reappraisal of the effect on safety. This should be the subject of an in depth review to make sure that lessons for the developoment process are learnt.

[infrequentflyer789]

Old school Boeing test pilot: "add vortex tabs"

Millennial engineers: 'add software"

Where does the part about "design wings correctly" come in?

But the wings were correctly designed. The engines were designed too large, or undercarriage designed too short - take your pick.

They had to extend the nose gear for all Max and design and certify a magic folding link thing on the main gear for the -10, I'm not sure why they didn't just do that job properly and give -8/-9 and -10 long enough legs to put the engines same place as the NG so that it flew like the NG, with no need for crazy software bodges.

I think the root of the problem will turn out to be the modelling/simulation at the very start of the process, this was what lead them to believe that they could just mount the engines forward and up a bit, and the only resulting problem was it got a bit light on the stick in a small part of the envelope - so just tweak software to nudge the stab if anyone ever goes there, job done.

It was a brilliant plan with only one teeny tiny flaw - the modelling was b:mad:cks. Over confidence and over promise on schedule meant that by the time they found that out they were in a corner where the only possible "fix" looked like changing that nudge on the stab to a full blown miles-out-of-trim yank, and over large areas of the envelope based on only on sensor. Cross fingers, collect bonus, and hope it doesn't break too often and that the regulator won't notice (if we don't tell)...

[Icarus2001]

that they could just mount the engines forward and up a bit, and the only resulting problem was it got a bit light on the stick in a small part of the envelope - so just tweak software to nudge the stab if anyone ever goes there, job done. Once again, that part of MCAS was not the issue from what we know so far. It was that ONE FAILED AOA vane could cause MCAS to activate. THAT was the issue. A software fix is fine, the fact that it could operate on erroneous data from a single source is not.

If you don't like software "nudging the stab" up or down then I guess you hate Tailstrke Avoidance inputs right? Or Airbus Alpha floor? Or Embraer stall avoidance?

[fdr]

Smythe, you have a point,;to a carpenter the fix is a hammer.

The aero around the engine/pylon/wing is pretty complex, and modelling is anywhere from rough to detailed, but the full detail takes enormous amounts of CPU hours even for a single solution such as RANS. To get unsteady solutions that tend to better approximate the real world is a whole bunch of magnitude greater in computational overhead. URANS, DES/LES or other sorts of unsteady solutions will hint at the outcome, but then they are also limited, unless the underlying model that is used to develop the mesh of the structure is able to move appropriately from the loads applied, as an aeroelastic model. That will dim the lights across the oceans to undertake, so the best guesses in the wind tunnel models which have their own problems go out in sheet metal or carbon, and get flown. The wings are not rigid structures, and flow occasionally goes where you expect, as often as not it does weird stuff. That is the world we live in, and that makes design an art form. The 787 was a surprise to see VGs on the outer sections, that is for quite specific reasons and that would have been annoying to the guys at TBC to encounter.

Flow control by VGs makes some sense on some issues, there is only a slim likelihood that alteration to the strakes could remove the issue on the Max, VGs around the wing won't do anything much. VGs on the elevator, and T's, Ls, wedges etc would alter the control power of the elevator, which may assist. Doing that always makes for a review of aeroelastics and also PIO susceptibility.

Repurposing the MCAS was obviously seen as an elegant and expedient solution, which is regrettable in hindsight, however the reason why that was done is now of interest, as if it was related to stall prevention, then there is a whole lot of issues that needed to be covered in the design and that seems to be pretty darn quiet.

In the end, the Max will be a good plane, it is a painful experience for everyone concerned, particularly those torn up by the accident directly. If the OEM grows a conscience, they will learn from this and be better for it in the future. The industry needs both of the major OEMs, so they need to get this right.


Icarus: "If you don't like software "nudging the stab" up or down then I guess you hate Tailstrke Avoidance inputs right? Or Airbus Alpha floor? Or Embraer stall avoidance?". There is nothing wrong with having devices, when they have been appropriately assessed for failure modes. The expedient action of the repurposing missed opportunities to get the risks sorted, and to make the system compliant with the existing regs however safe their protection may be. A stick pusher without an override function is effectively what MCAS had morphed to, from being a limited authority SAS. That is a big change and the devil is still in the details which remain obscured at this point in the public arena.

[SteinarN]

Once again, that part of MCAS was not the issue from what we know so far. It was that ONE FAILED AOA vane could cause MCAS to activate. THAT was the issue. A software fix is fine, the fact that it could operate on erroneous data from a single source is not.

If you don't like software "nudging the stab" up or down then I guess you hate Tailstrke Avoidance inputs right? Or Airbus Alpha floor? Or Embraer stall avoidance?

Well, I dont know which Embraer aircraft you have in mind and wheter it is fully FBW.
Speaking of Airbus aircraft a major difference compared to the 737 it that the Airbus (and Boeing from the 777 up) is fully FBW with triple redundancy or more of everything. To name a few on the 320, triple AOA sensors, triple FCC with two separate processors in each for a combined six processors running in parallell. Triple electric motors and power supply and additional hydraulic motor for the stab. This is done to decrease the risk of erroneous activation of the flight control surfaces, as well as giving backup should any one system fail to activate.

Compare this with the 737 stab where most components is single. Single stab motor, single power supply to that motor, only two processors in total in those two FCC so if one give erroneous data there is no way to know which one is correct and which one is at fault.

[Water pilot]

There is no problem with a properly designed fly by wire system because from the very start the designers know how catastrophic sensor and computer failures can be if not planned for. It is hard to argue that the 737 MAX was designed that way, or if it was designed at all. It is like opening the electrical box of a 60 year old house that has been remodeled by several generations of "weekend warriors" (guilty of that myself). You can't really say that such an electrical system is "designed", stuff gets patched in as you go and you are always thinking "if I could rip out the walls I really should add a separate circuit for the microwave but oh look, here is a wire that is only being used for the smoke alarms, so I'll tap into that circuit...." and you end up with a house where if the microwave short circuits the smoke alarms are disabled...

I have found it difficult to find any decision that Boeing made in this debacle where they put safety first. I'm sure there must be some place where they thought "oh, this would be an easy fix but it is not the safest way to do it so we will do something harder/more expensive" but it is not apparent.

[calypso]

The A320 can be dispatched and hence flown for revenue with a single failure on most triple redundant systems.

[gums]

Salute!

Thanks, FDR. Sound like a pilot with advanced degree, maybe even a test pilot. But don't know due to no public background on these forums. So credibility is not 100%.. It;'s good, but only based upon good technical arguments and explanations.
++++++++++++++++
I shall stand by initial assertion that the "problem" was aero, and that Boeing chose to use a kludge versus an aero solution just as they did with the STS. Apparently, the basic plane had been modified enuf thru the ages that it was too "slippery" and longitudinal stability needed "help" to tell the pilot that the plane was going faster than the last "trimmed airspeed". But most here know that it is the AoA change that increases induced drag and then actual CAS for the parasite drag and such, so it ain't just speed. It's AoA and the change in Cl that uses rho vee squared and surface area, and so on.

The "single point/sensor" failure would not have played a role if the basic aero problem was solved with basic aero engineering. Nevertheless, the MCAS was implemented with warts and all. Shoddy fault tree analysis, maybe even lack of flight tests to look at the slow and low envelope versus a medium altitude, turning, banked maneuver. I am glad I was not a line pilot that had not been informed of the system and how it worked.

Gums sends...

[Smythe]

VGs' are not certainly the solution in this case, there is a fair bit of CFD needed to sort out the underlying issue, and then a whole bunch of playing with the subsequent control forces to ascertain the real extent and solution of the problem, if, and only if it is considered that having a stab that cannot be controlled due to excessive airloads in manual mode is a bad thing.

What concerns me is that the initial CFD modelling showed at 0.6 degrees would be enough to mitigate the issues. On flight test, that was found not to be sufficient, and somewhere, the 0.6 turned in 2.5 degrees.
That is an exponential difference, and I would really like to see the modelling and assumptions that supported either numbers...

There is also the NYT report where the test pilot stated MCAS orginally used G force, and that was dropped somehwere along the line...now what was that used for? It seems that the high G manuevers the pilot was talking about such as wake turbulence or avoidance (that caused stall?)

Again, the CFD assumptions that required MCAS or where mitigated by MCAS would be very, very interesting to look at.

Vortex tabs to prove laminar flow over the wings should not required at this point in design evolution. I was really surprised when they showed up on the 787....will see on the 777-W

[yoko1]

.

What concerns me is that the initial CFD modelling showed at 0.6 degrees would be enough to mitigate the issues. On flight test, that was found not to be sufficient, and somewhere, the 0.6 turned in 2.5 degrees.
That is an exponential difference, and I would really like to see the modelling and assumptions that supported either numbers...

There is also the NYT report where the test pilot stated MCAS orginally used G force, and that was dropped somehwere along the line...now what was that used for? It seems that the high G manuevers the pilot was talking about such as wake turbulence or avoidance (that caused stall?)

Again, the CFD assumptions that required MCAS or where mitigated by MCAS would be very, very interesting to look at.



I’ve seen no mention of CFD modeling, so I don’t know if they used CFD or actual flight tests to determine the design parameters.

According to the article you reference, MCAS was originally designed to mitigate undesirable handling characteristics during a high-speed accelerated stall. The g-meter input was used along with the AOA as a sanity check on the accelerated stall condition. At the higher speeds, the 0.6 unit input was probably enough.

Later on, it was decided to expand MCAS’s role to correct control feel issues during low-speed, 1-g stalls. This required removing the g-meter from the loop and increasing the input to 2.5 degrees because at the lower speed a greater stab movement was needed. At this point someone should have noticed that 1) there was no redundancy to prevent the single-point failure, and 2) there was no test for high-speed (0.6 input) versus low-speed (2.5) stab input.

Too many chefs, to little communications, and no one providing a thorough top to bottom review of the final design.

[Zeffy]

https://www.seattletimes.com/business/boeing-aerospace/boeing-on-hold-as-it-awaits-737-max-verdict-from-global-regulators/


Boeing on hold as it awaits 737 MAX verdict from global regulators
By Dominic Gates
Seattle Times aerospace reporter

Top Boeing executive Greg Smith said Wednesday the jetmaker is in a holding pattern, waiting for the verdict from aviation regulators worldwide on its fix to the 737 MAX before it can move ahead with getting the plane back in service.

Separately, he raised the possibility that production of the second version of the forthcoming 777X may be delayed due to lack of near-term demand.

Smith, chief financial officer and executive vice president for strategy, said Boeing has turned over to the regulators its software fix for the 737 MAX flight-control system, as well as recommendations for additional pilot training and is now answering detailed technical questions from all corners of the globe every day.

The fix should prevent the erroneous malfunction of the system that contributed to the fatal crashes of two MAX jets in Indonesia and Ethiopia, killing 346 people. The plane has been grounded worldwide for more than 11 weeks.

“We’ve completed the software and training and passed that over,” said Smith. “Now we’ve got regulators from around the world coming in with more questions before we go to the next milestone.”

“We’ve pulled out all the stops as far as what anyone needs in any part of the globe and being responsive,” he said.

His remarks make clear that Boeing is working to achieve at least a measure of consensus among safety regulators round the world before moving to have the MAX fly passengers again. And one reason for that, he said, is concern that the brands of both the 737 MAX and Boeing itself have been damaged and need careful repair.

Smith said Boeing is looking outside the company for image and reputation support, “hiring folks on the brand management side, or on crisis management, getting some experts in there to help us manage that.”

“We’re putting whatever resources are required, inside and outside the company, to help us restore the MAX brand and work on the company brand,” he said. “We need to bring the best and brightest to do that, to understand where we are globally with the brand and what do we need to do in the U.S. versus in China and by airline.”

Speaking at the UBS Global Industrials conference in New York, Smith said that even after the regulators give clearance to end the grounding of the MAX, the process of returning the fleet to service will be an enormous logistical challenge that will take weeks or months depending on the needs of each airline.

He said Boeing teams are doing detailed planning for when that moment comes, negotiating with each customer airline and getting ready to deploy teams of technicians to take planes out of storage, install the software fix and provide the necessary pilot-training resources.

Meanwhile, Boeing is coordinating with its 737 suppliers, many of which are struggling to maintain a production rate to supply parts for 52 jets per month even though Boeing itself has cut back to rolling out 42 finished planes a month.

Separately, Smith also hinted at some issues with the new widebody 777X jet program in Everett. Two of the new airplanes with giant carbon composite wings have already rolled out of the factory, with two more in final assembly, and first flight is expected soon.

Smith said that GE has had “challenges” in producing the huge GE-9X engines for the airplane. “They are having to do some re-testing,” he said.

The plane is still expected “to fly this year and enter service in 2020,” said Smith.

In addition, demand for the 777X, and in particular for the smaller 777-8X version, has been soft and recent sales have been sparse.

Boeing will build the 777-9X first and was expected to deliver the -8X model perhaps a year later. Smith said Boeing is “looking at the timing and demand for the -8 to see if that still makes sense and do we want to push that out?”

Dominic Gates: 206-464-2963 or [email protected]; on Twitter: @dominicgates.

[fdr]

.

What concerns me is that the initial CFD modelling showed at 0.6 degrees would be enough to mitigate the issues. On flight test, that was found not to be sufficient, and somewhere, the 0.6 turned in 2.5 degrees.
That is an exponential difference, and I would really like to see the modelling and assumptions that supported either numbers...

There is also the NYT report where the test pilot stated MCAS orginally used G force, and that was dropped somehwere along the line...now what was that used for? It seems that the high G manuevers the pilot was talking about such as wake turbulence or avoidance (that caused stall?)

Again, the CFD assumptions that required MCAS or where mitigated by MCAS would be very, very interesting to look at.

Vortex tabs to prove laminar flow over the wings should not required at this point in design evolution. I was really surprised when they showed up on the 787....will see on the 777-W

Hi. The NYT article gives the background that really answers those questions.

Originally the MCAS is conceived and accepted as a high g & high AOA triggered SAS device, which doesn't need a great range of motion to achieve it's outcome, the 0.6 value is born. Along the way, the device gets repurposed to being a low speed "anti-stall" device, and as the issue is a low speed event, the g trigger is removed, and the motion rage gets increased markedly. Ooops. In doing so, the two trigger AND logic that protected from single point failures was removed, and the response rate had increased by more than 4 times. doing this set up JT and ET accidents. The requirement in here was likely a need to comply with §25.203(a), "No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls." § 25.145 Longitudinal control may also have triggered the repurpose, § 25.145(a) It must be possible, at any point between the trim speed prescribed in § 25.103(b)(6) (https://www.law.cornell.edu/cfr/text/14/25.103#b_6) and stall identification (as defined in § 25.201(d) (https://www.law.cornell.edu/cfr/text/14/25.201#d)), to pitch the nose downward so that the acceleration to this selected trim speed is prompt with(1) The airplane (https://www.law.cornell.edu/cfr/text/14/25.145) trimmed at the trim speed prescribed in § 25.103(b)(6) (https://www.law.cornell.edu/cfr/text/14/25.103#b_6);
(2) The landing gear extended; (3) The wing flaps (i) retracted and (ii) extended; and (4) Power (i) off and (ii) at maximum continuous power on the engines.

§ 25.103 Stall speed (b)(6) The airplane (https://www.law.cornell.edu/cfr/text/14/25.103) trimmed for straight flight at a speed selected by the applicant, but not less than 1.13VSR and not greater than 1.3VSR.

So, it is possible that the early flight tests showed less than desirable nose down pitch authority near or in the stall with the stab trimmed at 1.13VSR to 1.3VSR. That this was found in early flight test wouldn't have needed a large error in CFD modelling to occur. It is why testing is done.

A simple fix would have been to add trim at that point, which it appears is what the repurposed design would now do. But doing so, the removal of the g trigger of the original accepted high speed, high g design now opened up a single failure point design which could trigger a very powerful trim change authority at any time.

Underneath this the testing issue would range from, an unacceptable under any case pitch up tendency, to a "less than prompt" response near or in the stall when set up under the rules for demonstration. I would guess to the pitch up tendency, but both are possible. In any event, while focusing on one problem, a simple fix probably set up the latent conditions for lack of fault tolerance. The design at this stage would probably be a no go item for an AOA probe failure of any form, I understand it alternates use between the single sensors, but is not user selectable to the other side in a failure case. As an SAS system that was deemed necessary to meet the § 25 subpart B requirements, it would have needed a warning system to the crew of a failure, and that puts the design as built into likely conflict with the rules. Sad day all round. The repurpose suggests that the low speed model was slightly different to expectation, the high speed case may have been found not to occur, or may still have existed, conclusion can't be drawn i\on the high speed case from the info provided. The decision makers probably didn't think that there was any consequential risk in removing a trigger requirement, it's not like adding more stuff, they removed a criteria that could have faults as well, but in so doing, made an intolerant design without failure alerting, alerting that had already been missed in the first set of design acceptance review. The process to end up at this point doesn't need overt action by any players, it just needs assumptions and lack of imagination or curiosity, and in a project under commercially derived time constraints and a policy driven by the customer through commercial to avoid changes necessitating differences training, well, the engineers are human, and the system has room for improvement.

Organisationally, the QA whistleblower & KC scandals pointed towards a broken high level institution in need of some navel contemplation, and such activity if still occurring in this case would be pretty ugly in the impending proceedings. Whether the ethics issues have been fixed will be on display in the wash up.

[fdr]

Where is the thrust line compared to the NG? And with the more powerful engine can you cite any data that exists about how the handling would be affected had there simply been enough ground clearance to put the thrust line in the same place as the NG?
‘Large areas of the flight envelope’ is rather subjective. Can you cite the relationship between stab trim and flight envelope parameters of velocity, load factor and altitude, that formed the basis of MCAS as it was certified?

The Max engine center line is near the same as the NG. the moment has changed as the thrust can be higher. Neither design has the engine orthogonally aligned, so the forward position of the Max would alter the arm of the thrustline unless the incidence angle of the engine was adjusted. The original angle is a compromise for performance and handling.

The geometry problem is ground clearance for installing a larger diameter fan. Moving the engine forward permits bringing the engine core upwards from where it would have been if the gear had been extended only, reducing the extent of moment change that would occur just from the thrust line. That then added the aero moment which MCAS was expected to fix elegantly in the first instance.

[Icarus2001]

A stick pusher without an override function is effectively what MCAS had morphed to, from being a limited authority SAS.Except that it is not.

It can be overridden by the trim switch on the control column.

It can be switched off by using the switches on the centre console.

How is that "not capable of being overridden"?

[fdr]

Except that it is not.

It can be overridden by the trim switch on the control column.

It can be switched off by using the switches on the centre console.

How is that "not capable of being overridden"?


Icarus, fair point. it was then just a stick pusher system added without the awareness of the crew, and led to 2 crews planting planes into the turf. Without that information the crew are left in the dark in a single AOA failure in flight, that they have lost more than just an indicator or input to the ADC etc, they have lost something that affects the control of the aircraft, and is not annunciated or reported as such. MMEL permits despatch with heaters inop for the AOA in certain situations, without the crew being aware that an inadvertent icing encounter now may affect a system that they were not aware of being available. The MMEL also permits despatch with one of the two control yoke trim switches inop, there is always a manual trim and the cutout as you indicate. If the fault occurs on departure, there would be a pilot with a pickle switch.. If it happens during a comfort stop, then the pilot in the cockpit has to use what he can reach to sort it out and that comes to using the cutouts.

I stand corrected, but it remains a lousy architecture that does not appear to meet the advisory requirements of certification of a SAS system.

[Smythe]

The Max engine center line is near the same as the NG. the moment has changed as the thrust can be higher. Neither design has the engine orthogonally aligned, so the forward position of the Max would alter the arm of the thrustline unless the incidence angle of the engine was adjusted. The original angle is a compromise for performance and handling.

I really doubt they would change the incidence angle of the engine to compensate for the increase moment arm due to the location being further forward and upwards.

Decreasing the incidence angle of the engine would have profound consequences in cruise. The decoupling of the wing angle and engine angle would send the flow computations out of control. Boeing has enough problems with laminar flow over the wings as it is.

Here is the logic. SMYD 1 is used for primary yaw damping and is connected to the both ADIRUs and left AOA Sensor for inputs.


https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/640x406/screen_2bshot_2b2018_11_20_2bat_2b8_50_14_2bam_6b472f376d927 a5ca4e34965c48b3622f63442d0.png

A single AoA sensor is connected. 2 sensors are not connected to look at a disagree.

SMYD 2 is used to match SMYD 1 primary yaw damper commands, and is available as a backup under certain conditions when SMYD 1 is not available. SMYD 2 uses both ADIRUs and the right AOA sensor for inputs.

Only one FCC can control the mach trim actuator at a time. The IFSAU receives the FCC select signal from FCC B. This signal controls a relay in the IFSAU to find which FCC will give the mach trim actuator signals. The IFSAU sends the mach trim select status signal to the FCCs to show which FCC is in control. The IFSAU then sends mach trim power and motor drive signals to the mach trim actuator.

Only one FCC at a time supplies the speed trim signal to the stabilizer trim electric actuator. When the FCCs get electrical power, FCC A supplies the speed trim signals. If power remains on the FCCs, the on ground signal from the proximity switch electronics unit (PSEU) switches the FCC which supplies the speed trim signals. If one FCC fails, the other FCC automatically supplies the speed trim signal.

For Mach trim, Speed trim, (and MCAS?); the single active FCC CPU#1 command is made regardless of CPU#2, and regardless of the non-active FCC.

more at https://www.satcom.guru/2018/11/737-fcc-pitch-axis-augmentation-command.html

[WHBM]

They had to extend the nose gear for all Max and design and certify a magic folding link thing on the main gear for the -10, I'm not sure why they didn't just do that job properly and give -8/-9 and -10 long enough legs to put the engines same place as the NG so that it flew like the NG, with no need for crazy software bodges.
I understand that this, which was really the start of the whole issue, was due to the basic 1960s 737-100 frame structure of the aircraft not having sufficient space between the ribs and spars for a landing gear of the new required length to be retracted into. Sorting that out would have been a complete frame redesign.

[tdracer]

The maximum thrust of the engine is limited on the 737 by the ability to counteract the thrust induced pitch-up moment - hence the max thrust on the 737-8 is not a whole lot different than the max thrust on the 737-800. It might appear higher if you only look at the Sea Level Static rating, but big turbofan thrust lapses (decreases) with forward speed - the higher the bypass ration, the greater the lapse with forward speed. So, while the SLS thrust might be higher for the MAX, the thrust at ~120 knots will be pretty similar to the equivalent NG.
BTW, this is nothing new - limiting the max thrust goes back to the 737-3/4/500 'classic' - the only difference being on the 'classic' the -300 and -500 had throttle blockers to prevent more thrust than the tail could handle, on the NG and MAX it's done with a rating plug.

[Peter H]

Taking a tiny fragment from a large post.
A stick pusher without an override function is effectively what MCAS had morphed to ...

[SLF] Would a "real" stick pusher have been an adequate solution to the handling/certification problems MCAS was intended to solve?

1a) Would a stick pusher meet the "control column feel" certification requirements that MCAS is intended to address?
1b) Would it introduce any problematic certification issues?
1c) Would any false triggering be acceptably benign and infrequent?
1d) Are there any additional sim training obligations for certification?
1e) What have I forgot? e.g. any hi/low speed issues; is more than control column feel needed for approach-to-stall avoidance?

2) What additional benefits to handling/airworthiness would a bug/feature free implementation of MCAS provide?

[fdr]

[QUOTE=Smythe;10487440]I really doubt they would change the incidence angle of the engine to compensate for the increase moment arm due to the location being further forward and upwards.

Decreasing the incidence angle of the engine would have profound consequences in cruise. The decoupling of the wing angle and engine angle would send the flow computations out of control. Boeing has enough problems with laminar flow over the wings as it is.

/QUOTE]

Don't disagree. Back in the last century a well known airline based around the south china sea evaluated various trim angles for the engines on their 4 engine jets, and gained a benefit from doing so from how the planes were being delivered. There wasn't much difference in handling but there was a difference in fuel burns.

[Fly Aiprt]

it was then just a stick pusher system added without the awareness of the crew, and led to 2 crews planting planes into the turf.

Except that a stick pusher acts on the elevetor, not the stabilizer, though.
And so is never beyond the stick authority.

[yoko1]

The maximum thrust of the engine is limited on the 737 by the ability to counteract the thrust induced pitch-up moment - hence the max thrust on the 737-8 is not a whole lot different than the max thrust on the 737-800. It might appear higher if you only look at the Sea Level Static rating, but big turbofan thrust lapses (decreases) with forward speed - the higher the bypass ration, the greater the lapse with forward speed. So, while the SLS thrust might be higher for the MAX, the thrust at ~120 knots will be pretty similar to the equivalent NG.
BTW, this is nothing new - limiting the max thrust goes back to the 737-3/4/500 'classic' - the only difference being on the 'classic' the -300 and -500 had throttle blockers to prevent more thrust than the tail could handle, on the NG and MAX it's done with a rating plug.

The 737NG is rarely thrust limited, so there's not a compelling reason to provide much additional thrust in the MAX. The new LEAP engines were added primarily for increased fuel efficiency and not increased thrust.

[yoko1]

​​​​​​Inside the Effort to Fix the Troubled Boeing 737 MAX (https://www.wsj.com/articles/testing-the-fix-for-the-troubled-737-max-11559772634)

[Fly Aiprt]

​​​​​​Inside the Effort to Fix the Troubled Boeing 737 MAX (https://www.wsj.com/articles/testing-the-fix-for-the-troubled-737-max-11559772634)

Interesting article in the WSJ, thank you yoko1.
We discover that previous tests were run on a fixed sim. And the aircraft is manageable when no MCAS interferes, which we already knew.
It seems they did not test what the "new MCAS" does when it kicks in, though.

[DaveReidUK]

The 737NG is rarely thrust limited, so there's not a compelling reason to provide much additional thrust in the MAX. The new LEAP engines were added primarily for increased fuel efficiency and not increased thrust.

That's certainly true of the Max 8/9 compared to the -800/-900.

I'm not sure sure that it holds for the bigger and heavier Max 10, for which there is of course no NG equivalent.

[Smythe]

not really larger engines for thrust, but for larger fans. Larger fans equals better fuel economy...

I guess it could be for that "high altitude, hot airport" they claimed they were limited! :mad:

[Loose rivets]

My recollection of the push on the 1-11 is of a system that pushed well after the shaker started and the nose drop was quite benign. Well, while safe at 310. I can recall being coached to pull and pull some more to make it happen.

From what I've learned over the last months is that MCAS is a fairly different animal - the prime objective seems to be not letting those last degrees of nose up be achieved with low stick forces. I can see why it is, and then again is not, an anti-stall device. It's more than just semantics.

Ground clearance. Is it even remotely possible the techniques used on the -10 undercarriage could be retro-fitted to the -8? That would buy, what was it, 10" ?

[atpcliff]

The Boeing CEO now says that they predict the return of the 737 max to the skies "by the end of the year"!!!
...
or maybe never...

[RickNRoll]

My recollection of the push on the 1-11 is of a system that pushed well after the shaker started and the nose drop was quite benign. Well, while safe at 310. I can recall being coached to pull and pull some more to make it happen.

From what I've learned over the last months is that MCAS is a fairly different animal - the prime objective seems to be not letting those last degrees of nose up be achieved with low stick forces. I can see why it is, and then again is not, an anti-stall device. It's more than just semantics.

Ground clearance. Is it even remotely possible the techniques used on the -10 undercarriage could be retro-fitted to the -8? That would buy, what was it, 10" ?

The -10 undercarriage doesn't lift the plane by 10", it makes the rotation more user friendly be effectively moving the wheels back and creating more height at rotation.

[tdracer]

That's certainly true of the Max 8/9 compared to the -800/-900.

I'm not sure sure that it holds for the bigger and heavier Max 10, for which there is of course no NG equivalent.

The -10 will be longer - which gives a better moment arm for the tail. So the -10 can have more thrust than a -9, which can have more thrust than a -8 (for the same reason).

Smythe, high/hot is a different issue - the airframe can still handle as much thrust at an equivalent IAS, but the engine may not be capable of producing as much thrust in the thinner and/or hotter air (without exceeding a limit - usually EGT - but other issues can come into play). If the engine is effectively derated for the baseline sea level operation, increasing high/hot thrust is relatively easy since the engine already has unused margin.

[armchairpilot94116]

The Boeing CEO now says that they predict the return of the 737 max to the skies "by the end of the year"!!!
...
or maybe never...
The problem with the MAX is turning out to be possibly the biggest problem Boeing has ever faced.

[Dee Vee]

The problem with the MAX is turning out to be possibly the biggest problem Boeing has ever faced.

Looks like they are bringing in the big (legal) guns now.

Boeing turns to high-powered defense attorneys in 737 MAX investigation (https://www.seattletimes.com/business/boeing-aerospace/boeing-turns-to-high-powered-defense-attorneys-in-737-max-investigation/)

The three attorneys leading the defense team are Mark Filip of the law firm Kirkland & Ellis, who served as deputy attorney general under President George W. Bush; Richard Cullen of MaguireWoods, a Virginia-based law and crisis-management firm; and William Burck, co-managing partner of the Washington, D.C., office of Quinn Emanuel Urquhart & Sullivan.

“As such, a primary goal of a white-collar criminal defense lawyer is persuading the government that her client did not commit a crime, in order to avoid an indictment,” Wolfe said. “Generally speaking, once an indictment is returned, it becomes very difficult for defense counsel to persuade the government to dismiss.”

[gums]

Salute!

The biggest legal cost to Boeng is gonna be the civil actions And U.S. juries are known to make ridiculous awards based on emotion and ignorance versus facts and stats.

A jury recently awarded zillions of bucks to a family that asserted the herbicide Roundup caused them to have non-Hodgkin's lymphoma.
The Oakland, California jury has awarded a couple $2 billion in punitive damages after concluding that sustained exposure to Monsanto Co.'s popular Roundup weed killer led to their cancer diagnoses.

The MCAS debacle has a much more clear chain of events than the Roundup herbicide case. The lack of training, the failure to inform crews of the system and how it worked, the "faulty" fault analysis, "there must be fifty ways...."..

Gums sends...

[krismiler]

The losses involved in the MAX debacle will make Airbus losses on the A380 program look like small change.

[JanetFlight]

Hi, i recognize this is a very delicate question, and of course its something that i would never, ever, wish to happen...but here it goes...in the event of an extreme and super bad worst scenario is there any remote chance that the MAX would never fly again and grounded forever as we know it?

EDIT» PS: Im a plane and boeing lover since as a child and i wish to all the colleagues at Boeing all the best!

[Maninthebar]

Hi, i recognize this is a very delicate question, and of course its something that i would never, ever, wish to happen...but here it goes...in the event of an extreme and super bad worst scenario is there any remote chance that the MAX would never fly again and grounded forever as we know it?

I think there IS a small but finite chance of this.

It is in the interest of all current parties (even including other marques) that a robust set of fixes is found, and in a timely fashion.

BUT

The longer this takes, and the more training might be required the greater the chance that either or both Boeing and customer airlines will decide to cut their losses and find something else,

[Zeffy]

https://www.seattletimes.com/business/boeing-aerospace/boeing-didnt-plan-to-fix-737-max-warning-light-until-2020/

Boeing didn’t plan to fix 737 MAX warning light until 2020
June 7, 2019 at 9:17 am Updated June 7, 2019 at 9:52 am

By Mike Baker
Seattle Times staff reporter

After discovering a problem in 2017 with a cockpit warning light on the 737 MAX, Boeing decided it would defer an update to fix the issue until 2020, congressional officials said Friday.

Even as it continued delivering MAX airplanes to customers, Boeing had kept quiet the details of the problem, which prevented a light from warning pilots when there was disagreement between the plane’s angle-of-attack sensors. Those sensors are now suspected of playing in a role in two MAX crashes.

The company didn’t disclose the issue to the FAA until after a 737 MAX crash in Indonesia last year, something that frustrated FAA leadership. Now, leaders with a transportation committee in the U.S. House said they have obtained information about the initial plan to fix the issue in 2020, although they did not immediately explain the origin of that information. They have sent letters to Boeing, the FAA and supplier United Technologies requesting documents around the problematic alert.

“An important part of the Committee’s investigation is finding out what Boeing knew, when the company knew it and who it informed,” said Rep. Rick Larsen, a Washington state Democrat who leads the aviation subcommittee. “I have questions about the decision to not deem the AOA Disagree alert as safety critical and I am concerned it took Boeing so long to report this defective feature to the FAA and its customers.”

Boeing has said its engineers discovered that the warning light wasn’t functioning in 2017. The company determined that the issue did not adversely impact the safety or operation of the plane.

The warning light, which is standard on the MAX and included in the pilot manuals, is designed to light up if there’s a disagreement between the two sensors on either side of the plane’s nose that measure the jet’s angle of attack — the angle between the oncoming air flow and the airplane’s wing.

At the time of the crashes, the alert worked only on planes flown by airlines that had bought a different indicator added to the main flight-display panel. Lion Air and Ethiopian Airlines did not have those packages.

If it had been working, the warning light would have lit up on the fatal flights of both the Lion Air and Ethiopian jets. It’s not clear that it would have made a difference, as Lion Air pilots were unaware of the MAX’s new automated maneuvering system that pushed the plane’s nose down in response to the erroneous angle-of-attack data.

With knowledge of the overall system in the wake of the Lion Air crash, the Ethiopian pilots might have benefited from the information, but a preliminary report suggests they were ultimately able to diagnose the problem. They still weren’t able to maintain control of the plane.


Mike Baker: 206-464-2729 or [email protected]; on Twitter: @ByMikeBaker.

[Smythe]

The -10 undercarriage doesn't lift the plane by 10", it makes the rotation more user friendly be effectively moving the wheels back and creating more height at rotation.

The MAX 10 gear is a 'scissor lift" which extends for DEP and ARR and compresses for stowing.

https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/960x671/40380051_998138447032939_296084544191201280_n_ebbbfd4a6bce2c 7a769b119141737e4e695a63b6.jpg

grounded forever as we know it?

Currently, it is grounded forever as we know it. There will need to some interesting changes to get it back in the air, not just a dashboard light and some software.

[Bend alot]

If I "owned it" I think it is well past the time to get my sword out.

That and confess the rest of the issues now, rather than the current death by a thousand cuts.

[krismiler]

If the MAX stays grounded until the end of this year, which is quite likely, then with current production rates and the number already sitting on the ground, we could be looking at nearly 700 aircraft parked.

Many airlines would be unable to have all their aircraft on the ground at their home base at the same time due to lack of space and rely on the fact that most of the time they will be in the air or turning around at out stations.

The MAXs already in service at the start of the grounding are reasonably well dispersed worldwide, however with the number already produced since they stopped flying and 40-50 more coming out of the factory doors each month, where are Boeing going to store them ?

[568]

If the MAX stays grounded until the end of this year, which is quite likely, then with current production rates and the number already sitting on the ground, we could be looking at nearly 700 aircraft parked.

Many airlines would be unable to have all their aircraft on the ground at their home base at the same time due to lack of space and rely on the fact that most of the time they will be in the air or turning around at out stations.

The MAXs already in service at the start of the grounding are reasonably well dispersed worldwide, however with the number already produced since they stopped flying and 40-50 more coming out of the factory doors each month, where are Boeing going to store them ?

Flight museums?

[568]

If I "owned it" I think it is well past the time to get my sword out.

That and confess the rest of the issues now, rather than the current death by a thousand cuts.

That's the problem, they, the BC, don't want the close scrutiny to be highlighted, especially when other "matters" will surface in due course.

[Icarus2001]

The Boeing CEO now says that they predict the return of the 737 max to the skies "by the end of the year"!!!

Did he say which year?

[Smythe]

I bet the 777X is not on an accelerated certification schedule anymore....

[armchairpilot94116]

Flight museums?
Perhaps Boeing should suspend production ! That of course brings other issues to light. But to build or not to build, that is the question.

[Gove N.T.]

I thought the software fix was in and that the aircraft had done a few hundred test flights and found to be fine - safe and ready for return.
One has to wonder whether self certification will be the feature of future releases.
Trust is an unquantifiable figure on the balance sheet - except for accountants of course

[yoko1]

I thought the software fix was in and that the aircraft had done a few hundred test flights and found to be fine - safe and ready for return.


I suspect that the new software isn't what's holding up the show. In the course of examining these accidents some other issues have come to light (like the difficulty in using the manual trim wheel is some situations) and the level of trust in Boeing and the FAA are at an all time low. Some regulators may also require sim training, and there are currently not enough sims to accommodate all the operators. This will take longer than anyone initially thought.

[krismiler]

Damned if they do and damned if they don't, Boeing want to get the aircraft back in the air asap however the fix has to be 100% because if there is another accident that's the end of the MAX. Boeing would then be left with several hundred unsellable aircraft which have cost them billions to produce and will be worth scrap value. They will lose their bread and butter income and have to survive on the B777/B787 and military contracts for several years whilst they need to fund the development of an all new replacement narrowbody which will be looked at sceptically by potential purchasers.

The British aircraft industry was dominant after WW2 until the Comet disasters, by the time the design flaws were sorted out the type had been overtaken by the B707 and British aviation never recovered. The Chinese C919 is only a couple of years away from first deliveries and might prove to be a credible option for airlines which are unable to secure Airbus A320s. If the C919 is a commercial success, Boeing will struggle to regain their position in the market and could be reduced to number three in the narrowbody arena behind Airbus and Comac. If the MAX is permanently grounded this would give a huge leg up to the Chinese aerospace industry and whilst the C919 currently falls short of current Airbus/Boeing types in terms of performance, once the orders and money start coming in improvements will soon follow.

[EIFFS]

I suspect that the new software isn't what's holding up the show. In the course of examining these accidents some other issues have come to light (like the difficulty in using the manual trim wheel is some situations) and the level of trust in Boeing and the FAA are at an all time low. Some regulators may also require sim training, and there are currently not enough sims to accommodate all the operators. This will take longer than anyone initially thought.

Simulator capacity needn’t be an issue, MCAS is not much more than a bolt on to the existing STS ( speed trim stability) system, therefore it would be relatively easy to put a software package on the NG simulators to mimic the MAX.

Having flown both, from a pilots perspective the NG/MAX are closer to each other than the CL/NG in terms of general handling, indeed this is how it was designed to be!

The crux of this is how to identify and deal with STAB TRIM RUNAWAY, the problem for the manufacture is that the QRH qualifies that statement by adding the word “continuously” to STAB TRIM RUNWAY condition statement and the MCAS does not result in the stab trimming running continuously, but rather 5 secs of stab movement to push the nose down, it only does it once, unless you ( as you will) trim nose up, then MCAS resets and trims down again, meanwhile unless you pull the power back the aircraft continues to accelerate requiring more trim, this whilst you’re trying figure what is going on! eventually you’ll either run out of height or elevator authority from which there is only one outcome.

In in the industry we are already seeing crews in sim sessions assuming that in the LVO section 6 thinking that they have a trim runway when the trim systems start to trim nose up at 400 during the auto land in preparation for a possible dual channel go around and pressing TOGA when in fact all is well......

What ever the eventual fix it has to be bullet proof.

[Maninthebar]

if there is another accident that's the end of the MAX.

If there is another accident attributable to MCAS then the risk is to Boeing as a whole and not just the MAX

[EIFFS]

Damned if they do and damned if they don't, Boeing want to get the aircraft back in the air asap however the fix has to be 100% because if there is another accident that's the end of the MAX. Boeing would then be left with several hundred unsellable aircraft which have cost them billions to produce and will be worth scrap value. They will lose their bread and butter income and have to survive on the B777/B787 and military contracts for several years whilst they need to fund the development of an all new replacement narrowbody which will be looked at sceptically by potential purchasers.

The British aircraft industry was dominant after WW2 until the Comet disasters, by the time the design flaws were sorted out the type had been overtaken by the B707 and British aviation never recovered. The Chinese C919 is only a couple of years away from first deliveries and might prove to be a credible option for airlines which are unable to secure Airbus A320s. If the C919 is a commercial success, Boeing will struggle to regain their position in the market and could be reduced to number three in the narrowbody arena behind Airbus and Comac. If the MAX is permanently grounded this would give a huge leg up to the Chinese aerospace industry and whilst the C919 currently falls short of current Airbus/Boeing types in terms of performance, once the orders and money start coming in improvements will soon follow.

I think a permanent ground unlikely, I guess Boeing could always restart the NG production, something 14% less fuel efficient but in the eyes of the public safe might work as a stop gap, Boeing’s leverage would be on pricing and that fact that Airbus production is sold out half a decade in advance, for 90% of the route market it does the job and on shorter sectors there will be little difference in cost per seat per kilometre, Boeing would have to go for a quantum leap aircraft that puts it way ahead of Airbus narrow body, composite, bleeds less with a nose that looks like a mini Dreamliner or A350 rather than a red London bus, a 20% fuel burn saving ought to be achievable.

I bet Boeing wished they’d trusted their original judgement to go for a clean sheet rather than be railroaded by south west and other big 73 buyers into keeping a common type rating.

[Smythe]

Simulator capacity needn’t be an issue Not sure where you are located, but sim time has been at a premium for quite a few years. Used to be, if we wanted to check something out quick, we could just run down to the sim, not anymore. Booked up with all the newbies especially.

The crux of this is how to identify and deal with STAB TRIM RUNAWAY MCAS isnt stab trim runaway. If it was that simple, there would simply be an off switch. MCAS was a cure for the problems, but doesnt solve the problems.
You have high AoA stall, low speed stall, and high G maneuver stall problems to deal with. That is not a dashboard light and software patch fix.

I thought the software fix was in and that the aircraft had done a few hundred test flights and found to be fine - safe and ready for return. According to Boeing, the software fix has not been submitted to the FAA for review. It also appears that the 'testing' has been, for the most part, in the sim, not actual flights.

Currently, the Congressional Committee is handing the Lazy B theirs B's.

[Lake1952]

If the MAX stays grounded until the end of this year, which is quite likely, then with current production rates and the number already sitting on the ground, we could be looking at nearly 700 aircraft parked.

Many airlines would be unable to have all their aircraft on the ground at their home base at the same time due to lack of space and rely on the fact that most of the time they will be in the air or turning around at out stations.

The MAXs already in service at the start of the grounding are reasonably well dispersed worldwide, however with the number already produced since they stopped flying and 40-50 more coming out of the factory doors each month, where are Boeing going to store them ?

Perhaps they can be stacked? But it will make quite an interesting photo... a few hundred brand new 738Ms parked somewhere. And when return to service does occur, it will take several months at least for the stored backlog production to be delivered, accepted and entry into service.

[safetypee]

Smythe, et al.
There was no need to change the basic MCAS algorithm. It was ‘tried and tested’, and certificated.
The safety issue involved the integrity of the AoA input to the computation, where an error resulted in unanticipated trim operation due to weaknesses in the implementation - design good, engineering and certification not so. Without changing or improving the AoA vane, the initial solution (1) concentrated on limiting the effect of an erroneous value; cross comparison of sensors, limiting the extent and rate of trim.
Apparently this did not meet with regulatory approval, thus a revised version is being considered.
Most system testing and validation could be completed with ground simulation / stimulation of the overall system. A test flight would validate the integrity enhancement with ‘simulated’ in-flight failures. Also it would be expected that the certification authorities require demonstrations of flight handling with MCAS disabled and any limitations in operation.

The extent of the flight tests is surprising and more likely to be related to other issues arising from the accidents; particularly the trim runway drill and the apparent inability to use the trim wheel or elevator to pitch the aircraft.
This might involve additional modification and flight testing; see tech discussions earlier in this thread.

1) https://www.boeing.com/commercial/737max/737-max-software-updates.page

[gums]

Salute!

Not so sure the Max will survive, and even with more and low-priced NG variants, folks will still be leery of buying the planes as long as it has "737" in the model number.

Back in the day Lockheed bit the bullet on the Electra and did major hardware/aero fixes. The result wound up as the P-3 ASW platform and served for over 4 decades, and even now being replaced by P-8's. However, public trust had been lost and Lockheed walked away from the commercial market and sold P-3 planes to all comers.

The looming, myriad of trials has yet to begin, and their publicity will not impress folks that discover their ride to visit grandma is one of the "fixed" Max platforms.

Only way Boeing can survive is to stop selling the MAX with MCAS. Fix the aero problem and advertise "no MCAS required", or simply stop selling the model and take the $$$ hits.

Gums opines...

[PEI_3721]

Yo gums,
As discussed previously, an aerodynamic correction (‘fix’) might not be particularly easy, if at all; and / or it could affect the economics aircraft operation. Aero fix might not sell so well, MCAS fix might require extensive PR / discount to improve sales, but does not guarantee commercial success.

As you note, a key parameter is public opinion. Historically, adverse perceptions fade or can be ‘adjusted’ - e.g. power of fake news, but the depth of feeling in this instance is unknown. Overseas operators, not on US soil, might be easier to dispel than would a home grown accident, but - the unknown effects of home certification error and poor oversight.

Beware the fickle human. Aviation safety has ranged from the domination of technical failure, through human ‘error’, to systems views, where in the widest sense the public within the ‘system’ has an input via media and politics.

It would be unfair to make a direct comparison with the demise of turboprops in the US regions. It happened, perhaps without great fanfare or body count, but it changed the operational industry and over time the marketing of newer types - the power of commerce, money talks.

If MCAS mods are approved, which appears likely, then why spend money on Aero fixes, but if other problems dominate - trim, then aero fixes could address both issues. Expensive and time consuming; requires balance, but as yet perhaps not Boeing’s call.

[Smythe]

Smythe, et al.
There was no need to change the basic MCAS algorithm. It was ‘tried and tested’, and certificated.
The safety issue involved the integrity of the AoA input to the computation, where an error resulted in unanticipated trim operation due to weaknesses in the implementation - design good, engineering and certification not so.

Tried and tested...certificated??? You are posting in jest, no? Such a simple fix, yet so far 87 days on the ground?

From 0.6 to 2.5 without notifying the FAA? What was tested? Test pilots dont appear to have tested 2.5?

What about the low speed stall, push the nose down 2.5 degrees at low speed, and presumably low altitudes?

High G issues? push the nose down 2.5 degrees on a high G manuever?

It is not that one of the AoA sensors failed, look at how they are wired. They are not coupled to a single source, each one is wired to different sources. That is a rewire, not just a software issue.

How do you explain the certification process with EASA and the FAA used MCAS at 0.6, and never revealed the 2.5 change to the regulators? The AoA light on disagree doesnt work? ooops. In reality, if 2 sensors disagree, well then, what, pick one you like? (while the ac is nosing down because it thinks its stalling...

all

[maxxer]

As they all have troubles with these lqtest generation engines.
I wonder really on a 737 flight how much it saves between a stansted to barcelona flight. The only thing you read is that they are more efficient so how much more ?
I live under a flight path in belgium well not actually the flight path , but just because they are not allowed to fly over brussel that much the take off to the south and then head west and then fly around brussel to go east again to germany for example.
But I checked the noise and an old 747f doesnt make more noise then a 787 while the 787 was on a shorter trip then the 747f so the super new engines dont really do much in the improvement of noise.
So i am curious if the the leap engine compare to the old CFM56 engine really makes so much up in fuel efficiency or this is just some guy with excel sheets.

[Max Angle]

I wonder really on a 737 flight how much it saves between a stansted to barcelona flight. The only thing you read is that they are more efficient so how much more ?
On the A320 (same engine with a slightly larger fan) the burns are around 15% down on the V2500 version, over the course of a year that is a lot of fuel.

[ARealTimTuffy]

The Max burns a little over 2000 KG an hour. Approx the same as the E190, but with 70 or so extra passengers.

On a 5 hour flight you should save approx 2500 to 3500 KG of fuel over a CFM56. It is pretty amazing how engine efficiency has changed in the last 20 yrs.

High G issues? push the nose down 2.5 degrees on a high G manuever?

According to the information I have the MCAS will still only trim .67 units for the high speed (high G) increasing AOA. The 2.5 was the mod for low speed to create the necessary stick pressures. .67 still worked for high speed, but it needed to be adapted. Ooops.

Tuff

[Vilters]

Did anybody properly "preserve" their aircraft?
Where all fluids drained and purged?
Time to start thinking about "long term storage procedures" and how to "preserve" those aircraft.

Non flying aircraft also collect moisture in the strangest places so also start thinking about corrosion inspections.

On the same level; Is there an approved "return to flight status" procedure??

Just some thoughts worth thinking about, because this is not the end, it is just the beginning of the troubles.

[safetypee]

Smythe, # 234
MCAS in normal operation worked exactly as designed; the system and design description appeared to meet the certification requirements. The AoA ‘failure’ was either not considered in the design, or judged insignificant in the failure effects analysis, thus it might never have been tested, ground or air. Theory and practice may have disagreed, but how can we tell.

0.6 to 2.5 appears to be a simple error; this might have been one of the self certification items without specific ground rig measurements, only software validation.

You appear to overlook that flight tests are not ‘stick free’, so the aircraft will not pitch unless the pilot fails to resist the change of stick force - change in force was the primary objective in the particular conditions. So during flight testing the difference in trim rate over time, opposed to absolute tail angle, would be perceived as a difference in stick force, except there was no lower value for comparison. The pilot would feel a change in force, and that the change (larger than necessary), meet the certification stability requirements which was the objective of MCAS.
MCAS involves stability (stick force); whereas approach to the stall 1.1 Vs is alerted with stick shake - not to be confused with the AoA failure in the accidents which generated a false stick-shake, and the stability certification requirements above 1.1 Vs, similarly comments re stalling Vs; (aircraft don’t think).

EASA generally validates FAA certifications - bilateral agreement, but can intervene at any level including flight tests; e.g NG question about trim.

Re AoA Disagree; see Boeing statement https://boeing.mediaroom.com/news-releases-statements?item=130431.
The alert alone is meaningless, has no value in determining failure or action, and even without any drill would only be relevant to the optional installation of the AoA indicators (not fitted).

[olster]

Does anyone, anywhere have any idea when the Max will return to service?

[Neufunk]

No. At this point, the Boeing 737MAX saga is in full swing, with opinions and speculations coming from left and right, without anyone actually knowing any facts.

My personal opinion is that it will return around December - January, and it will take a few months until all the airlines get back to fully using it.

[USN O6]

No. At this point, the Boeing 737MAX saga is in full swing, with opinions and speculations coming from left and right, without anyone actually knowing any facts.

My personal opinion is that it will return around December - January, and it will take a few months until all the airlines get back to fully using it.

Have no idea about the return, but "Roger That" for your most intelligent statement concerning facts.

Best,
Jim Harnes

[Bend alot]

The biggest fact is that the FAA have not been given all the facts during the certification of the MAX.

These "facts" are slowly coming to light and not from Boeing in any timely manner.

I have no doubt there are more facts yet to see the light and that is not restricted to MCAS, thing such as simulators and trim wheel forces and other items as mentioned in the media and places such as Pprune will be examined and researched by the world regulators that have been assembled.

December/January seems optimistic when considering the level of trust now given to Boeing under it's current leadership.

[Loose rivets]

High G issues? push the nose down 2.5 degrees on a high G manuever?

I think this is the main point. It doesn't hopefully succeed in pushing the nose down but loads the controls in a manner that is equivalent to such an AND input - a load that mimics the aerodynamics of a different aircraft.

In a high g manoeuvre the pilot is not lightly to suddenly let the nose attitude be ripped from his grasp but would naturally accept the stick loads being enhanced.

Real training required.

[krismiler]

Major modifications could be necessary to ensure a safe aircraft which could require a new type certificate. Boeing are caught between doing enough to restore safety but not so much that the MAX loses its Grandfather rights from the original design. Basically this is what they tried to do with MCAS and it didn’t work.

An interim measure could be to try and fit a FBW flight control system to the MAX and certify it as a new type which would be very expensive and time consuming but less so than a clean sheet design.

Unfortunately Boeing could be caught up in the trade dispute with China and unless the USA lays off on Huawei, the Chinese could refuse to accept any fix, declare the MAX unsafe and ban it from operating in their airspace. Their own narrow body is only a couple of years away from entering service and whilst not quite matching the A320/B737 its a credible enough alternative. Performance improvements will undoubtedly follow over the years as they have for most aircraft types.

[armchairpilot94116]

The biggest fact is that the FAA have not been given all the facts during the certification of the MAX.

These "facts" are slowly coming to light and not from Boeing in any timely manner.

I have no doubt there are more facts yet to see the light and that is not restricted to MCAS, thing such as simulators and trim wheel forces and other items as mentioned in the media and places such as Pprune will be examined and researched by the world regulators that have been assembled.

December/January seems optimistic when considering the level of trust now given to Boeing under it's current leadership.

My very first ride in an airplane was a rather old B737 100 series. Always liked Boeing planes and especially the 747 and the 737. With the MCAS debacle I am afraid Boeing has shown some level of incompetence or worse, deception. Not attributes I would normally associate with Boeing.

If the Max doesn't get back in the air world wide after say a year, then it could be safe to say it is over for the type. Boeing will have to revert to making the NG while it draws up plans and implements those plans for a whole new plane. The Max may be Maxed out . This is not my hope for the aircraft. I do hope they sort it all out nicely and it goes on to many decades of dependable service. I'd like to fly on one too.

[hec7or]

I do hope they sort it all out nicely and it goes on to many decades of dependable service.

complete with the 1960s 6 pack Crew Alerting system

[EIFFS]

As they all have troubles with these lqtest generation engines.
I wonder really on a 737 flight how much it saves between a stansted to barcelona flight. The only thing you read is that they are more efficient so how much more ?
I live under a flight path in belgium well not actually the flight path , but just because they are not allowed to fly over brussel that much the take off to the south and then head west and then fly around brussel to go east again to germany for example.
But I checked the noise and an old 747f doesnt make more noise then a 787 while the 787 was on a shorter trip then the 747f so the super new engines dont really do much in the improvement of noise.
So i am curious if the the leap engine compare to the old CFM56 engine really makes so much up in fuel efficiency or this is just some guy with excel sheets.

14% saving in fuel burn has been validated, I’ve done enough trips from both EDI & DUB to SWF & PVD on both new-ish NG & the MAX and the saving in fuel burn is real world real.

The MAX is quieter both internally and externally, down sides? well BRM ( bow rotor motoring) during high internal/external ambient temperature is embarrassingly slow to start the engines at between 2-3 minutes -V- 40 seconds on a standard CMF on busy ramps such as LGW, the MAX’s empty CoG is much further forward than the NG means that you have to fill rear hold first before you put anything in the front hold, so mixed operations with NG & MAX needs carefully monitoring on the ramp, on the plus side tail tipping is close to impossible on the MAX ( this will be an even bigger problem if they ever convert them to freighters with the heavy PEMCO cargo hold door)

[Falcon666]

If the Max doesn't get back in the air world wide after say a year, then it could be safe to say it is over for the type. Boeing will have to revert to making the NG while it draws up plans and implements those plans for a whole new plane. The Max may be Maxed out . This is not my hope for the aircraft. I do hope they sort it all out nicely and it goes on to many decades of dependable service. I'd like to fly on one too.

I understand there is one Airline meeting planned in the next few weeks in Germany where one point of discussion will be the possibility of changing their order of MAXs back to NGs.
It may only take one airline with a significant order of MAXs to do this , possibly kicking off a domino effect with others?

[73qanda]

complete with the 1960s 6 pack Crew Alerting system
Guaranteed 80% will work 90% of the time.