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

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

Old 30th Sep 2019, 22:14
  #2761 (permalink)  
 
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Originally Posted by MemberBerry View Post
Also, no matter how low friction that ball nut is, it seems what's preventing the use of the trim wheels when severely out of trim is somehow friction related.
And not the aerodynamic load on the stab ?

Hmmm.

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Old 30th Sep 2019, 22:38
  #2762 (permalink)  
 
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Originally Posted by Tomaski View Post
Yanrair is essentially correct. This aspect of the manual stab trim system has been there on the 707, 727, and the entire 737 line since inception, and it was apparently okay with the EASA and its predecessors. What changed? Well, for one thing airline training departments stopped teaching it, and general awareness of the issue was apparently lost along the way.

I've been on Boeing's most of my 30+ years in aviation, and I am very familiar with the trim system. Quite a few years back, I was actually taught the "roller coaster" technique. Somewhere along the way, the stab system in general, and runaway trim in particular, became less and less of a feature in our training syllabus. Despite the fact that runaway trim is a "memory" procedure, a pilot might see it once on initial checkout but it was not a regular feature of our normal recurrent training cycle (Stop and think about that for a moment.) In the early days of the MAX accident investigations, I was absolutely flabbergasted by the number of 737 pilots at my own airline who were unaware of many aspects of this trim system. To the extent that this was also the case at Lion Air and Ethiopian, then the pilots' reactions are more understandable.
Hi Tomaski
I am pleased that you say I am essentially correct because like you I have been flying Boeings since the sixties including the 737 most variants except Max, 707 (10 years) 757 767 747-400 and Tristar (non Boeing). I was the only pilot in UK licensed to fly the 737-400/757/767 concurrently with passengers to try and see if Boeing's claim that "they are all the same" was true! (All our pilots could fly the 757/767 concurrently despite one being twice the size of the other).
Boeing have always been annoyed by the fact that Airbus have this big advantage in commonality of handling and flight deck design. I flew that trio for a year sometimes flying a 767 in the morning and a 737 in the afternoon. It was fun and quite do-able but you had to stay so much on top of the learning and also it required 6 sim checks per annum, three Safety days, and three line checks. That was the killer. And no, I did not recommend it become the norm. For the reasons stated recently in this thread, the operation has to be capable of being flown by an average pilot - whatever that is.
I taught the 737 syllabus for twenty of those years and yes the emphasis in recent years has switched to not insisting on the full skill set which was demanded then. I find that deplorable.
My contention is that the "average" pilot skill set is now too low and needs a major revamp. It is Not the fault of the pilots and I especially mean the Lionair and ET pilots who were doing it would appear what they were trained to do, and it may not have been enough.
I get the impression from a lot of the comments I read here that some writers have only been on the 737 as a passenger and that a lot of comment is regurgitated from what is read in the media. Not from actual experience of actually doing any of this stuff. Yes, many of the commentators here are indeed professional 737 pilots too and have bags of experience. That is usually evident by the quality of the commentary.
I stand by the comments I made back just after the second crash. It was I think avoidable, especially given the publicity surrounding the first one. Every pilot I know in the UK / Ireland situation was all over that first crash report learning what they could from what they have read. And the Boeing bulletins . We learn these days more from a study of recent near accidents or actual accidents which occur daily around the world because we are unlikely to experience the actual situation in line flying due to the rarity of events. That is why Nat Geographic Air Crash Investigation is so popular with pilots who want to survive. I hope we all learned from the AF 447 how not to fly with unreliable IAS. And Turkish Airlines at AMS that an auto-thrust failure should be a non event.
but did we learn from the Lionair crash? And especially the fact that the day before it was handled to a safe landing. Two days apart. Totally different outcome. Some learning to be had there.
Quite soon, I would say within a couple of months we will see where this is going and this thread will then become quite interesting. The problem faced by the whole industry is that if pilot training is even partly to blame, then there is a massive task ahead, but do-able at a cost.
For Boeing, they would hate a situation where it might appear that the 737 requires more training than an Airbus - perish the thought. Even though a well flown 737 is probably the Panzer tank of the air - it can take a lot of failures and still flies right down to total hydraulic failure and total electrical failure and the add in two failed engines. It still flies. If you know how.
Enough idle conjecture for one night.
Talk soon.
Y
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Old 30th Sep 2019, 22:41
  #2763 (permalink)  
 
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Originally Posted by Speed of Sound View Post


QF32 landed safely due to some excellent fault analysis, incredible workflow management, cool heads, and a lot of luck

An aircraft should be capable of being operated safely by any crew trained to minimum certified standards, not just exceptional crews.
That sounds like if QF had been flown that day by an average crew (this word is being used a lot recently) that the result would have been catastrophic. Unless all QF crews are above "average"?
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Old 30th Sep 2019, 22:46
  #2764 (permalink)  
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Originally Posted by DaveReidUK View Post
And not the aerodynamic load on the stab ?

Hmmm.
Hmmm, indeed. It's really inconceivable that friction between the jackscrew and the ball nut could even come close to the axial forces transmitted from aero loads on the stabilizer.
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Old 30th Sep 2019, 22:58
  #2765 (permalink)  
 
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Originally Posted by yanrair View Post
That sounds like if QF had been flown that day by an average crew (this word is being used a lot recently) that the result would have been catastrophic. Unless all QF crews are above "average"?
It’s been a while now but around that time, I remember a number of crews (maybe Qantas, maybe not) flew the QF32 scenario in the sim and less than half of those crews saved the plane.
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Old 30th Sep 2019, 23:13
  #2766 (permalink)  
 
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Originally Posted by yanrair View Post
Hi Tomaski
I am pleased that you say I am essentially correct because like you I have been flying Boeings since the sixties including the 737 most variants except Max, 707 (10 years) 757 767 747-400 and Tristar (non Boeing). I was the only pilot in UK licensed to fly the 737-400/757/767 concurrently with passengers to try and see if Boeing's claim that "they are all the same" was true! (All our pilots could fly the 757/767 concurrently despite one being twice the size of the other).
Boeing have always been annoyed by the fact that Airbus have this big advantage in commonality of handling and flight deck design. I flew that trio for a year sometimes flying a 767 in the morning and a 737 in the afternoon. It was fun and quite do-able but you had to stay so much on top of the learning and also it required 6 sim checks per annum, three Safety days, and three line checks. That was the killer. And no, I did not recommend it become the norm. For the reasons stated recently in this thread, the operation has to be capable of being flown by an average pilot - whatever that is.
I taught the 737 syllabus for twenty of those years and yes the emphasis in recent years has switched to not insisting on the full skill set which was demanded then. I find that deplorable.
My contention is that the "average" pilot skill set is now too low and needs a major revamp. It is Not the fault of the pilots and I especially mean the Lionair and ET pilots who were doing it would appear what they were trained to do, and it may not have been enough.
I get the impression from a lot of the comments I read here that some writers have only been on the 737 as a passenger and that a lot of comment is regurgitated from what is read in the media. Not from actual experience of actually doing any of this stuff. Yes, many of the commentators here are indeed professional 737 pilots too and have bags of experience. That is usually evident by the quality of the commentary.
I stand by the comments I made back just after the second crash. It was I think avoidable, especially given the publicity surrounding the first one. Every pilot I know in the UK / Ireland situation was all over that first crash report learning what they could from what they have read. And the Boeing bulletins . We learn these days more from a study of recent near accidents or actual accidents which occur daily around the world because we are unlikely to experience the actual situation in line flying due to the rarity of events. That is why Nat Geographic Air Crash Investigation is so popular with pilots who want to survive. I hope we all learned from the AF 447 how not to fly with unreliable IAS. And Turkish Airlines at AMS that an auto-thrust failure should be a non event.
but did we learn from the Lionair crash? And especially the fact that the day before it was handled to a safe landing. Two days apart. Totally different outcome. Some learning to be had there.
Quite soon, I would say within a couple of months we will see where this is going and this thread will then become quite interesting. The problem faced by the whole industry is that if pilot training is even partly to blame, then there is a massive task ahead, but do-able at a cost.
For Boeing, they would hate a situation where it might appear that the 737 requires more training than an Airbus - perish the thought. Even though a well flown 737 is probably the Panzer tank of the air - it can take a lot of failures and still flies right down to total hydraulic failure and total electrical failure and the add in two failed engines. It still flies. If you know how.
Enough idle conjecture for one night.
Talk soon.
Y
Some talk that the problems faced by these crews were made more difficult due to the multiple warnings and confusion caused by same. I agree that it would be tough but it is not new; all airplanes with a warning system will display all the existing problems at the same time (except for TO/LDG inhibits) and it has always been necessary for the crews to prioritize. Many accidents (including two in 1996 involving the 757) have been caused when the crews could not manage that and it would be expected that pilots and the training departments of their airlines would include this in the syllabus.

In this case, the problem that would have to be handled first would have been to stop the airplane from diving into the ground. If that is not solved, and solved immediately, there is no need to even look at the other warnings.

The standard stab trim fault procedure (runaway trim) would have worked but this was not done in either case resulting in the loss of both aircraft and the deaths of almost 350 innocents.

How can anybody claim that this is not true? What else would a trained crew do as a first response? Pushing the nose down as a response to the stick shaker would not help, nor looking through the QRH to identify the CAS messages. If a crew cannot fly the aircraft they do not deserve to be on the flight deck and the passengers did not deserve what happened to them. Sadly (in my opinion) due to pilot error.

If we do not identify the root cause of the accidents and do something to mitigate it the same thing can happen. The design and operation of the MCAS is not a root cause; it is contributing of course but it did not cause the loss of the aircraft. That was solely caused by flight crews that did not know or could not apply the correct immediate actions for the runaway stab trim.
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Old 30th Sep 2019, 23:20
  #2767 (permalink)  
 
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Originally Posted by boofhead View Post
Some talk that the problems faced by these crews were made more difficult due to the multiple warnings and confusion caused by same. I agree that it would be tough but it is not new; all airplanes with a warning system will display all the existing problems at the same time (except for TO/LDG inhibits) and it has always been necessary for the crews to prioritize. Many accidents (including two in 1996 involving the 757) have been caused when the crews could not manage that and it would be expected that pilots and the training departments of their airlines would include this in the syllabus.

In this case, the problem that would have to be handled first would have been to stop the airplane from diving into the ground. If that is not solved, and solved immediately, there is no need to even look at the other warnings.

The standard stab trim fault procedure (runaway trim) would have worked but this was not done in either case resulting in the loss of both aircraft and the deaths of almost 350 innocents.

How can anybody claim that this is not true? What else would a trained crew do as a first response? Pushing the nose down as a response to the stick shaker would not help, nor looking through the QRH to identify the CAS messages. If a crew cannot fly the aircraft they do not deserve to be on the flight deck and the passengers did not deserve what happened to them. Sadly (in my opinion) due to pilot error.

If we do not identify the root cause of the accidents and do something to mitigate it the same thing can happen. The design and operation of the MCAS is not a root cause; it is contributing of course but it did not cause the loss of the aircraft. That was solely caused by flight crews that did not know or could not apply the correct immediate actions for the runaway stab trim.
You couldn't be more wrong. Or more proud. You blame pilot error and then end by stating we need to identify the cause. Which is it you sound so confused. Let me help. This was not simply pilot error.
have a good night
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Old 30th Sep 2019, 23:28
  #2768 (permalink)  
 
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Originally Posted by OldnGrounded View Post
Hmmm, indeed. It's really inconceivable that friction between the jackscrew and the ball nut could even come close to the axial forces transmitted from aero loads on the stabilizer.
I'm probably going to regret the following post as it is made to *** possibly *** explain why some posters are so insistant on friction- lubrication -sideloads - issues on the jackscrew

But here goes

The MD80 ( DC-9 ) crash off the coast of california investigation shoed the problem was with a worn thread- pooorly lubricated jackscrewe,

https://www.ntsb.gov/investigations/...ts/AAR0201.pdf
And this excerpt

The interior of the recovered acme nut contained no intact threads, although therewere small ridges where the worn nut thread remnants had previously been attached. Theinner diameter of those ridges was almost identical to the outer diameter of the acmescrew threads, which is consistent with the worn acme nut threads having been sheared offby the acme screw threads during airplane-nose-down trimming movements
Note this refers to an ACME screw thread as shown later in the report on page 145
page 145

Figure 20. A graphical depiction of the stages of acme nut thread wear to the point of fracture.

HOWEVER- as has been shown and discussed for months in the 737 MAX threads, Boeing has used on 737 and following- ( and perhaps on 707-727 ) a recirculating ball "nut" on a jackscrew ( similar to that used on automobiles steering systems since the 1950's at least.
yes it does require lubrication- yes it can fail under extreme conditions- BUT it is unlikey- and VERY very low probability to fail by stripping threads or having extreme friction issues like that of the old fashioned house moving jackscrews designed to eliminate backdriving which is a design issue much more significant in the ballscrew-jackscrew

Hopefully - the above comparison will tamp/slow down the ' friction' side load- lubrication ' problem discussion with a ' new MAX " as being a significant issue in the MAX crashes.
Curious to know how many reports of a lube problem with the Boeing used ball-jackscrew system ?
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Old 30th Sep 2019, 23:59
  #2769 (permalink)  
 
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Originally Posted by Grebe View Post
Curious to know how many reports of a lube problem with the Boeing used ball-jackscrew system ?
The fact that some crews are struggling to turn the trim wheel in some situations can be classed as partly a lube problem because some of the effort that they are putting into turning the jackscrew is being lost in overcoming frictional forces caused by less than perfect lubrication.Probably not a great deal but it is some, and if I were a Boeing engineer faced with the possibility of having to retrofit 7,500 new servo motors and clutches I would be looking at every possible way to make the existing manual trim system more efficient.

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Old 1st Oct 2019, 00:06
  #2770 (permalink)  
 
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Originally Posted by Speed of Sound View Post

The fact that some crews are struggling to turn the trim wheel in some situations can be classed as partly a lube problem because some of the effort that they are putting into turning the jackscrew is being lost in overcoming frictional forces caused by less than perfect lubrication.Probably not a great deal but it is some, and if I were a Boeing engineer faced with the possibility of having to retrofit 7,500 new servo motors and clutches I would be looking at every possible way to make the existing manual trim system more efficient.
I enjoy the systems discussion as much as anyone here, however, strictly from an operator perspective, knowing how all the forces line up to create the unwelcome resistance within the manual trim system is far less important than knowing how to avoid the situation in the first place.
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Old 1st Oct 2019, 00:13
  #2771 (permalink)  
 
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Originally Posted by Speed of Sound View Post
It’s been a while now but around that time, I remember a number of crews (maybe Qantas, maybe not) flew the QF32 scenario in the sim and less than half of those crews saved the plane.
I think you also need to look at the very unique situation with QF32 where they had 2 extra very qualified ;pilots in the cockpit on that flight. this was recognized as a big reason why it was a successful end. Maybe something to be considered in relation to the earlier Lionair flight that landed safely.
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Old 1st Oct 2019, 00:36
  #2772 (permalink)  
 
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think you also need to look at the very unique situation with QF32 where they had 2 extra very qualified ;pilots in the cockpit on that flight. this was recognized as a big reason why it was a successful end. Maybe something to be considered in relation to the earlier Lionair flight that landed safely.
Not sure I agree.

The parameters of an aircraft experiencing MCAS on final approach has never been detailed/discussed by Boeing et al.
We have only heard about fixing MCAS on high speed DEP..

I have not heard of a solution for the known high speed maneuvering issues..

OR, the low speed stall issues experienced by the LionAir ac on final approach....(which you referenced)

cant wait for the 777MAX to start flying......
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Old 1st Oct 2019, 00:37
  #2773 (permalink)  
 
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Originally Posted by Tomaski View Post
knowing how all the forces line up to create the unwelcome resistance within the manual trim system is far less important than knowing how to avoid the situation in the first place.
Very true, however if the various authorities take a belt and braces approach to recertification of the MAX, Boeing may have to both improve training and make improvements to the manual trim system for those rare occasions when all the holes line up and for whatever reason the crew find themselves in a severely out of trim situation.
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Old 1st Oct 2019, 00:49
  #2774 (permalink)  
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Originally Posted by maxter View Post
I think you also need to look at the very unique situation with QF32 where they had 2 extra very qualified ;pilots in the cockpit on that flight. this was recognized as a big reason why it was a successful end. Maybe something to be considered in relation to the earlier Lionair flight that landed safely.
Five of 'em, altogether: PIC, FO, 2O, check pilot in training and check pilot trainer. Lots of extra brains and pairs of eyes on that flight deck.

From the ATSB report:

Crew performance

A key aim of crew resource management (CRM) is to minimise or manage crew workload. The additional flight crew that were present on the flight deck during the accident flight were resources available to provide support to the primary flight crew of the captain and first officer. The primary flight crew processed the ECAM messages and followed procedures in accordance with their training. They used other flight crew members at opportune times to share tasks not essential to flight safety and gather information to assist in their decision making. This included communication with the cabin and obtaining information in relation to the damage to the aircraft.

The operator’s training regime is structured around a prescribed number of flight crew being present in the flight deck. In this case the presence of additional flight crew members did not interfere with the primary flight crew operating in accordance with their experience and training. CRM advocates a primary flight crew’s use of all available resources including people, information and equipment. Therefore, the safe outcome of the accident flight was not only contingent on the primary and supporting flight crew but also on the efforts of the CSM and cabin crew
Emphasis added.
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Old 1st Oct 2019, 01:56
  #2775 (permalink)  
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Popping back to the clutches for a moment, do they actually slip? I thought they simply selected one input or another but crucially, left an open system for the cable drum when neither were engaged. Unless it's a known fact, I doubt the clutches would slip, especially if they run at the pre-gearbox motor rpm.

The pivot point on the H-Stabilizer. Thinking about why it's so far back, I realised that using normal airflow, the system is virtually power-assisted. The tail then flies to a point where it is neutral again. Further movement, either way, will be assisted by the airflow. Sadly, either a nut/thread failure or a rouge input will be power assisted by such an unstable system.

In answer to Mac the Knife's comment about the wheels and cables, I'd commented before it's almost as if it was Boeing ethos, a promise to pilots, that they would always have that physical connection to the Stab. It seems painfully ironic.
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Old 1st Oct 2019, 02:47
  #2776 (permalink)  
 
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Originally Posted by Tomaski View Post
I enjoy the systems discussion as much as anyone here, however, strictly from an operator perspective, knowing how all the forces line up to create the unwelcome resistance within the manual trim system is far less important than knowing how to avoid the situation in the first place.
To which I add AMEN AMEN AMEN

I had hoped my effort to explain why the friction-sideload- pivot point- stripped thread issues consistently pushed as being a significant issue is IMHO misleading would at least slow down the "explantion of what went wrong or similar needed redesign while having absolutely NO data or facts to support.

It obviously had zip effect if one looks at the posts following which re-iterate the same concepts-arguments.

Siiiighhhhhh - at least I tried with FACTS and data
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Old 1st Oct 2019, 03:59
  #2777 (permalink)  
 
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Originally Posted by Loose rivets View Post
Popping back to the clutches for a moment, do they actually slip? I thought they simply selected one input or another but crucially, left an open system for the cable drum when neither were engaged. Unless it's a known fact, I doubt the clutches would slip, especially if they run at the pre-gearbox motor rpm.
If one holds the manual trim wheel firmly while engaging the Main Electric Trim, the wheel will vibrate accompanied by a fairly noticeable ratcheting sound. I assume this is an indication that something is "slipping" back there.
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Old 1st Oct 2019, 04:59
  #2778 (permalink)  
 
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Originally Posted by Europa01 View Post

If holding the trim wheel against rotation from the stab motor stops HS movement then that is the torque at which the clutch disengages - this will be the maximum torque the stab motor can exert.
I don't think this is correct. There are a lot of posts in various threads to look through, so forgive me for being lazy and not quoting the exact one, but a while ago I did see an explanation like this:

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

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

It's not immediately obvious to me how such a mechanism would be designed, but I don't doubt that it is possible to design one given sufficient smarts. Can someone confirm that this is how it actually works on a 737?
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Old 1st Oct 2019, 05:24
  #2779 (permalink)  
 
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Boeing CEO and the usual blather from seattle times which uses Bloomberg from time to time
Boeing CEO sees ‘endgame’ in effort to lift grounding of 737 MAX
Sep. 30, 2019 at 9:30 am Updated Sep. 30, 2019 at 4:24 pm
By Julie Johnsson
Bloomberg

Boeing is in the “endgame” of preparing its 737 MAX to return to the commercial market after two deadly crashes prompted a global grounding more than six months ago, Chief Executive Officer Dennis Muilenburg said in an interview.

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

The CEO is also shaking up Boeing’s organizational structure to sharpen its focus on safety after the Ethiopian and Lion Air tragedies, although moves will fall short of the executive overhaul sought by some victim advocates.

“I’m very confident in the team we have,” Muilenburg said, pointing to a series of personnel changes the company has quietly made since March. The new appointments range from the head of the 737 program, to a vice president of engineering for the commercial airplane business and its supply-chain chief. “We’re always putting our best people in the toughest assignments, and that’s the case here.”
737 MAX crisis Complete coverage »

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Acting on a recommendation from the board, Muilenburg is creating a new product and services safety organization to centralize responsibilities across the company’s business and operating units. The new group will be run by Beth Pasztor, a 34-year Boeing veteran who will report to the company’s chief engineer and a new aerospace board committee.

Pasztor will have responsibility for all aspects of product safety, including investigating concerns raised anonymously by employees, Boeing said in a statement Monday. The company’s accident-investigation team, safety-review boards and engineering and technical experts who represent the Federal Aviation Administration in aircraft certification will all report to Pasztor, who previously oversaw product safety at Boeing’s jetliner division.

“Beth is a proven leader, she’s a collaborator,” Muilenburg said in an interview from the 36th-floor executive suite in the company’s Chicago office tower. He also considered external candidates before deciding that Pasztor’s deep knowledge of Boeing would give her a running start. “She, from a technical qualification standpoint, is the best.”

The CEO is under pressure to show airlines, travelers and global regulators that safety is woven into the century-old manufacturer’s designs and culture. Both have been called into question given the lapses that have prompted regulators to ground two new Boeing jetliners this decade. In 2013, the 787 Dreamliner was banned for three months after fires on two planes from lithium-ion batteries.

The company had already rung up $8.3 billion in Max-related expenses through July, and the costs of maintaining production and compensating customers are certain to grow the longer the grounding lasts.

The final steps to lifting the ban are clearly defined, and timing will be determined by the FAA, Muilenburg said. Once a final version of the flight control computer update is ready, Boeing will invite airline pilots to test-fly it in the company’s engineering simulators known as e-cabs. A separate team of pilots will review the company’s updated training material. After that FAA pilots will test the changes in a Boeing 737 MAX bristling with sensors and other flight-testing equipment.

“That’s the certification end game,” Muilenburg said. “We’re still marching to a timeline of return to service early in the fourth quarter, but I want to reiterate the timing will be determined by regulators.”

The Max hasn’t flown commercially since just after the March crash of an Ethiopian Airlines jet. A Lion Air plane went down off the coast of Indonesia in October. In both disasters, a once-obscure flight-control system went haywire, nudging the planes’ noses down until pilots were overwhelmed.

Directors last week signaled that they would closely monitor the company’s progress under Muilenburg. A new board committee is devoted to overseeing the safe design, development and production of the company’s aerospace product lineup. “Safety-related experience” will be a criteria to be considered in choosing future directors.

“This is an engineering company, it needs an engineering culture and engineering management,” aerospace analyst Richard Aboulafia said last week. “It deviated pretty far from this at the time when the Max was being developed.”

The U.S. National Transportation Safety Board last week called for a renewed focus on how a cacophony of flight-deck alerts can distract and overwhelm pilots. The agency’s report on the Max tragedies also provided clues to one of the mysteries of the disasters: how Boeing safety assessments for a software-system linked to the crashes could still comply with FAA design principles.
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Boeing’s simulator tests of the so-called MCAS system focused on pilots’ response to indications that a motor on the horizontal stabilizer was moving the plane’s nose down without their input.

But the hazard tests never examined specific failure modes that could cause MCAS to kick on — including failure of a key sensor that tripped multiple cockpit warnings and bewildered pilots on the Lion Air and Ethiopian Airlines flights.

Boeing, following recommendations from the board last week, will have the company’s tens of thousands of engineers report to the company’s chief engineer, Greg Hyslop. That will promote a more consistent approach to meeting operational priorities, while enabling senior managers to spot and elevate talented engineers, Boeing said. The move mirrors an earlier restructuring of finance professionals, who now report directly to Boeing Chief Financial Officer Greg Smith.

Muilenburg said he doesn’t expect the structural shift to substantially change the day-to-day work of those carrying out design and testing. But connecting the technical experts to other engineers across the company will create a new, informal network they can consult when problems crop up, he said.

He is also expanding Boeing’s safety-management system and safety-review boards, which are now led by senior executives, including Hyslop and business division chiefs. Boeing has also invested in enhanced flight simulation and computing capabilities. Software engineers in recent weeks have run 390,000 flight hours — the equivalent of flying 45 years — on the 737 MAX.

In addition, the company is already pouring money into researching the design of future flight decks to account for human factors.
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Old 1st Oct 2019, 05:33
  #2780 (permalink)  
 
Join Date: Dec 2018
Location: 8th floor
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Originally Posted by DaveReidUK View Post
And not the aerodynamic load on the stab ?
I believe it is the aerodynamic load causing it, but indirectly. I believe the aerodynamic loads on the stabilizer and the elevator cause increased friction between the nut and the jack screw.

Originally Posted by Grebe View Post
I think (member berry ) meant to say --Mentour's video it was getting harder **** and harder to trim ANU *** since the 'problem' to correct was severe AND made so by simulating ( MCAS ) which trimmed AND at a faster rate than yoke switch trims ANU. And of course maybe the same problem with the opposite ANU runaway ?
No, I didn't mean that. My original comment is accurate. To replicate the behavior of MCAS the FO was trimming manually AND (because with the flaps up the electric trim can't move the stab AND as much as MCAS can), and it was becoming harder and harder to trim AND. At 2.5 units from full AND trim it was almost impossible to trim further AND. Then, to see what the pilots on the Ethiopian flight might have experienced, the FO briefly tried to revert the AND trim he applied earlier, so he started trimming ANU. That was also impossible. So basically at 2.5 units from full AND the manual trim wheels became stuck, they couldn't be moved in either direction in that simulator.

Originally Posted by Europa01 View Post
I note your reply on the clutch thanks. My logic for my description of the clutch /trim wheel / stab motor went like this:-

If holding the trim wheel against rotation from the stab motor stops HS movement then that is the torque at which the clutch disengages - this will be the maximum torque the stab motor can exert.

In a simple system, where the electric motor would be connected directly to the cable drum, you would be correct. But the electric motor is not connected directly to the cable drum, it's connected to it through the gear box, so there are two torques involved:

- between the aft cable drum and the gearbox (close to 0 if the trim wheels in the cockpit are allowed to move freely, even if the electric motor is active)
- between the electric motor and the gearbox (this one will be high when the electric motor is active, and the aerodynamic load on the stabilizer is large).

What I was saying is that it is the torque between the aft cable drum and the gear box which causes the clutch between the electric motor and the gearbox to disconnect. So, if you don't touch the trim wheels, the clutch shouldn't disconnect. This is designed to give the trim wheels authority over the electric motor. Of course the electric motor has additional protections to prevent it from being over torqued and overheating, but those protections are independent from what I've described above.

Last edited by MemberBerry; 1st Oct 2019 at 06:52.
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