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737 Stuck Manual Trim Technique

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737 Stuck Manual Trim Technique

Old 27th May 2019, 00:12
  #121 (permalink)  
 
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Originally Posted by meleagertoo View Post
afaik, this is the first time in 60 years there's ever been an accident attributed to the previously well known jackstall shows.
does that not make you wonder just a tiny bit ?
is it not possible that had any previous accident been attributed to jackstall neither of these accidents would have happened?

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Old 27th May 2019, 00:17
  #122 (permalink)  
 
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Originally Posted by Takwis View Post
Or...

3 The MCAS inputs were barely manageable...six out of seven pilots exposed to an MCAS failure did not know what to do, and four of the seven are now dead. The problem was childsplay, however, for yanrair, 737 Driver, boofhead, and a few others... from their armchairs. Boeing built the airplane, Boeing came up with the training, Boeing concealed the existence and behavior of MCAS, and now Boeing SAYS it is fixed, even though there was nothing wrong with it in the first place.
I don't think anyone here is saying MCAS wasn't the problem and doesn't need to be fixed. However, as we all know aircraft accidents almost always have multiple causes so it is not a matter of it being an either/or fix. There has been a consistent trend over the past decade or so implicating crew skills and/or knowledge in commercial airline accidents. The skills a crew brings to a particular flight will be a direct result of their training, experience, and environment. Some of these are under the control of the pilots in question, but much of it depends on the training and corporate cultures of their employers. By laying all/most of the fault for these accidents at the feet of Boeing is, in effect, giving a pass to all the airlines out there who want to keep their pilot hiring and training costs to an absolute minimum. I seriously doubt MCAS will ever be the cause of another commercial airline hull loss, but I willing to bet that inadequately trained flight crews will be.
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Old 27th May 2019, 00:51
  #123 (permalink)  
 
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Well said

Well put Yoko1
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Old 27th May 2019, 03:39
  #124 (permalink)  
 
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Originally Posted by yoko1 View Post
We have at our disposal three separate FDR outputs (2 Lion Air, 1 Ethiopian). In each and every one of these outputs, automatic trim inputs (STS, MCAS) and pilot trim inputs are shown on separate traces. On yet another trace, stab position is shown. This is how we can tell that 1) the pilot trim was working, and 2) that this input stopped and countered MCAS every single time it was used. So yes, we actually do know.

Again, what is clear from these outputs is that at least 3 of the 5 pilots who actively controlled the aircraft during a MCAS malfunction were able to hold their own against these unwanted stab inputs. Two did not resulting in subsequent loss of control.

The issue as to why two of these pilots (particularly the Ethiopian Captain) lacked the basic flying skills the other three possessed should certainly be a key area of investigation.
It seems some people here are a bit jumping to conclusions.
Are we so sure that "we actually do know" ?
What makes you believe that they did lose control of the aircraft just for "lack of basic flying skills" ?
Of course you might be privy to facts that we don't know yet, but are we so sure that pilots with "basic flying skills" would have automatically fared better ?
I've seen so many qualified (and sometimes overconfident) pilots lose a big part of their flying skills when suddenly confronted with situation they are not trained for, that I'm getting wary of unsupported declarations.
What is unanswered to this date, is how one of those pilots with those "basic flying skills" would have clearly told the MCAS acting up from just the normal STS operation. How long would it take before the manual trim wheel becomes unmovable ?
I you do actually know, please feel free to share your information with us.
If not, well we're just in the armchair speculation realm...

Last edited by Fly Aiprt; 27th May 2019 at 03:41. Reason: Typo
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Old 27th May 2019, 05:25
  #125 (permalink)  

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The MCAS kicks in, the nose gets heavier. You pull, and trim a bit. The MCAS kicks in again, the nose gets quite heavy, you pull and trim - more, for zero forces - to negate both of the MCAS inputs. If for nothing just to relieve the muscle tension.

Is it the shared view here, that neither of the doomed crew did the above? That they all instead of a good thorough spin just made a couple of "blips" and watched the A/C in VMC hit the ground? While pulling with possibly all four hands on the yokes, fighting the 4x increased elev feel computer and still neither of them touched the rocker switches to relieve that physical pressure, save for those blips?
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Old 27th May 2019, 07:53
  #126 (permalink)  
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What the rules actually require

"It must be possible to make a smooth transition from one flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the airplane limit-load factor under any probable operating conditions"

"Approved operating procedures or conventional operating practices must be followed when demonstrating compliance with the control force limitations for short term application that are prescribed"

"When demonstrating compliance with the control force limitations for long term application that are prescribed in paragraph (d) of this section, the airplane must be in trim, or as near to being in trim as practical"

"must meet the trim requirements of this section after being trimmed, and without further pressure upon, or movement of, either the primary controls or their corresponding trim controls by the pilot or the automatic pilot"

"In the out-of-trim condition specified in paragraph (a) of this section, it must be possible from an overspeed condition at VDF/MDF to produce at least 1.5 g for recovery by applying not more than 125 pounds of longitudinal control force using either the primary longitudinal control alone or the primary longitudinal control and the longitudinal trim system. If the longitudinal trim is used to assist in producing the required load factor, it must be shown at VDF/MDF that the longitudinal trim can be actuated in the airplane nose-up direction with the primary surface loaded to correspond to the least of the following airplane nose-up control forces:

(1) The maximum control forces expected in service as specified in 25.301 and 25.397.


(2) The control force required to produce 1.5 g."


Other than the fact that the plane doesn't appear to meet these requirements, then blame the pilots at your gratuitous leisure, but know that under the conditions that the crew had, it is unreasonable to blame the pilots for the deficiencies that are evident in the certification standard, the application of the deficient certification standards, and the resultant unfortunate design choices, and finally, the reticence to train the flight crew on a known area of problematic compliance, the reason that MCAS was incorporated in the first place.

The crew are the result of the system that we have all collective responsibility for, the regulator, manufacturer, airline, TRTO's, and passengers. It is an example of the inherent resonance of the system, no particular failure was necessary by overt action, it was inherent in the assumptions of all users as to what the real world was doing, vs reality.

If you need to blame pilots for being the result of the problem, than know that it doesn't result in any increase in system safety as a consequence.

An old Persian saying:

"Arrogance is the capital stock of misfortune",
Pand-Namah Tasnif Saih Sa'di Sirazi, A Compendium of Ethics, translated from the Persian of Sheikh Sady of Shiraz, (1788)

The NTSB had the common courtesy of incorporating the human in the loop for Sully, yet now for ET and Lion it is apparent that it is only reasonable for a certain group of pilots to be considered to be human factors in the loop. That is ethically unjust and shows the inherent bias that exists in the observers and those that pass judgement from the safety of their laz-e-boys.
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Old 27th May 2019, 07:59
  #127 (permalink)  
 
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I have had this problem (runaway trim) and it was difficult to fly the airplane but I am still here so it was not impossible. I did not give up and flew the airplane to the ground with full nose down trim and because of a broken trim cable, no way to reverse the problem. I also flew the 737 for thousands of hours (although never had the trim runaway on that aircraft). I am not an "armchair" pilot and I do know how to fly and how to perform an emergency checklist. I am appalled at the lack of professionalism shown by the pilots in the two 737Max aircraft and even more appalled at the way so many on this thread are preferring to blame Boeing rather than the real cause of the tragedies because of political correctness. If they get their way they would put Boeing out of business and who would benefit then?

No aircraft is immune from failures of some type, and it is the pilot's job to fly it nevertheless and to keep the people who are placing their trust in him/her safe by at the least maintaining an average level of skill and knowledge. Which is all it takes. You don't have to be a super hero.

Fix the real problem. The human element. Take it as a warning of what will happen if we continue to dumb down (to the lowest common denominator as has been suggested we should be doing). Maybe we should be replacing the pilots with computers. They could not do any worse.
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Old 27th May 2019, 08:29
  #128 (permalink)  
 
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Originally Posted by fdr View Post
"It must be possible to make a smooth transition from one flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the airplane limit-load factor under any probable operating conditions"

"Approved operating procedures or conventional operating practices must be followed when demonstrating compliance with the control force limitations for short term application that are prescribed"

"When demonstrating compliance with the control force limitations for long term application that are prescribed in paragraph (d) of this section, the airplane must be in trim, or as near to being in trim as practical"

"must meet the trim requirements of this section after being trimmed, and without further pressure upon, or movement of, either the primary controls or their corresponding trim controls by the pilot or the automatic pilot"

"In the out-of-trim condition specified in paragraph (a) of this section, it must be possible from an overspeed condition at VDF/MDF to produce at least 1.5 g for recovery by applying not more than 125 pounds of longitudinal control force using either the primary longitudinal control alone or the primary longitudinal control and the longitudinal trim system. If the longitudinal trim is used to assist in producing the required load factor, it must be shown at VDF/MDF that the longitudinal trim can be actuated in the airplane nose-up direction with the primary surface loaded to correspond to the least of the following airplane nose-up control forces:

(1) The maximum control forces expected in service as specified in 25.301 and 25.397.


(2) The control force required to produce 1.5 g."


Other than the fact that the plane doesn't appear to meet these requirements, then blame the pilots at your gratuitous leisure, but know that under the conditions that the crew had, it is unreasonable to blame the pilots for the deficiencies that are evident in the certification standard, the application of the deficient certification standards, and the resultant unfortunate design choices, and finally, the reticence to train the flight crew on a known area of problematic compliance, the reason that MCAS was incorporated in the first place.

The crew are the result of the system that we have all collective responsibility for, the regulator, manufacturer, airline, TRTO's, and passengers. It is an example of the inherent resonance of the system, no particular failure was necessary by overt action, it was inherent in the assumptions of all users as to what the real world was doing, vs reality.

If you need to blame pilots for being the result of the problem, than know that it doesn't result in any increase in system safety as a consequence.

An old Persian saying:

"Arrogance is the capital stock of misfortune",
Pand-Namah Tasnif Saih Sa'di Sirazi, A Compendium of Ethics, translated from the Persian of Sheikh Sady of Shiraz, (1788)

The NTSB had the common courtesy of incorporating the human in the loop for Sully, yet now for ET and Lion it is apparent that it is only reasonable for a certain group of pilots to be considered to be human factors in the loop. That is ethically unjust and shows the inherent bias that exists in the observers and those that pass judgement from the safety of their laz-e-boys.
That is a very dense statement I confess I do not know what you are trying to say, but I guess it is in defence of the pilots. I do not intend to attack those poor guys; they were obviously out of their depth and should never have been in a position to fly as crew in the first place. I would have to place the blame for that on their airline that did not see to it that their crews were qualified. It does not change the fact that both MAX accidents were pilot error, solely and completely. The failure of the MCAS was the initiator but both airplanes were flyable and the crews failed to fly them; giving up in one case and failing to control speed by reducing the throttles in the other. Any confusion was self-induced and in no way a fault of Boeing or the airplane design. Obviously if the MCAS system, which works in the background, had been explained, most pilots would not have understood and would be even more confused than they are now. There was no need to know why the trim was running away; all the crews had to do was follow the checklist. Narrowing down the MCAS system for attention after landing.

The aircraft does meet all regulatory requirements, the MCAS system was provided to make it fly like its brethren and had no effect on stall speed or handling when it was working properly and when it failed did not need any action other than as a trim failure, which is already a procedure covered in training and practiced regularly (or should have been). The MCAS failure did not bring those aircraft down; poor flying skills did that. If we don't address that as the biggest problem we will see many more failures that will kill many more people. They deserve better.

If you are suggesting that it is OK for a properly trained crew to lose control of their aircraft because they had an unusual situation on their hands then we might as well give up now and get those horses and oxen out of their stalls and hitched up to the wagons before we risk any more passengers in those dangerous sky chariots.

It is not that long ago that pilots with only a few hundred (or less) hours were flying aircraft like the Lancaster and Fortress in war, with parts blown off by cannon fire. You better believe those guys did not give up. You would not have heard them blaming Boeing.
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Old 27th May 2019, 09:15
  #129 (permalink)  
 
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boofhead;

Be careful with guys like Boofhead, Yanrair and others!
Its always easy to say they should have done this or that and could have saved the aircraft easily due to better training and pilot skills!
It was the combination of failures which contributed to these accidents, beginning with AOA Sensor failure, the airspeed unreliable, stickshaker, stall warning and lots of red lights and warnings, all within a short time and in low altitude.
Then came the MCAS, which most did not know about and which was not mentioned by Boeing in the manuals.
In this situation your best strategy will fail and then you may forget or disregard things like speed or so
I bet, most of you guys couldn't save the aircrafts in this extremely complex and unexpected situation!
If you think about having the whole scenario in the simulator, early morning shift without briefing, most if not all crews would have failed to save this.
Of course now, after everybody discussed this at length you having a big advantage to the crews who lost their live.
And of course, not everbody is a Chuck Jaeger or a "Sully"
By the way, in my view the landing in the hudson was a "piece of cake" compared to the scenario of this two accidents!
In my view it is not enough by Boeing just to do some software changes, but the AOA sensor design with only two independant AOA's should have been overworked as well!
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Old 27th May 2019, 12:25
  #130 (permalink)  
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Boofhead; "The aircraft does meet all regulatory requirements, the MCAS system was provided to...."

nonsense.

The aircraft did not meet the rules under Subpart D, and that is the underlying issue. The general comments to date have been related to Subpart C, as there is a failure of the rules to provide adequate protection, just as was the case with AA587, where what was assumed by the industry was not so in reality. In all cases, a situation that requires both pilots on the controls to recover is not compliant, nor is having loads that exceed the momentary force loads to be applied by a single pilot, nor is it acceptable for the aircraft to require exceptional skill or strength.

(c) It must be shown that after any single failure of the stability augmentation system or any other automatic or power-operated system—
(1) The airplane is safely controllable when the failure or malfunction occurs at any speed or altitude within the approved operating limitations that is critical for the type of failure being considered;


must permit initial counteraction of failures of the type specified in 25.671(c) without requiring exceptional pilot skill or strength, by either the deactivation of the system, or a failed portion thereof, or by overriding the failure by movement of the flight controls in the normal sense.


and my favorite

(a) A warning which is clearly distinguishable to the pilot under expected flight conditions without requiring his attention must be provided for any failure in the stability augmentation system or in any other automatic or power-operated system which could result in an unsafe condition if the pilot were not aware of the failure. Warning systems must not activate the control systems.

Boof', you mention having control issues, so have I; I have landed a 4 engine aircraft without elevators, and I have landed an aircraft after a mid air collision. I don't believe that in either of those cases was it reasonable to have to rely on either the pilot skill or exceptionalism to survive. Both of those aircraft were military so the rules were different, however, after 20,000 additional hours on Boeings and Airbus, I don't believe that it is acceptable to rely on the pilots achieving something that has not been part of their training. Had they done so, then kudos, but don't shoot the messenger, the crews herein were the product of the training system that we have in the real world, and that is the way it is. It is not acceptable to assume that they would be a Chuck Yeager, Bob Hoover, Neil Williams or similar. What on earth do you expect from a 200hr co pilot in the way of support? What do you expect from a product of the current Part 61 syllabus, MCC shambles under FAR or EASA FCL? This is not regional, skin colour or religion based, we have just seen a fairly serviceable NG get seaplane time recorded, just as happens in Indonesia, Chukk, and various other places, including the Bahamas, etc.

The industry is adequate, not much better than that. You cannot bitch about a crew that is confronted with a complex issue that still confounds the manufacturer and regulator 9 months later, and state with a clear conscience that the problem begins and ends in the cockpit. If you show proof that the crew had been trained competently in runaway trim, of dealing with a stabiliser that was so far out of trim that it needed unloading to be reset, that the crew had sufficient altitude to unload a full nose down trim stab before impacting the ground, that the OEM told them of these latent defects in their aircraft design, that the airline had done so, that they had been checked to such a level?

I am angry; I am angry as I have flown Boeing products for nearly 40 years, and the only aircraft that had any discussion on stab airloads was not a Boeing. I have done out of envelope flight test of the B737 and was not aware of the issue. I am angry on behalf of the flight crew that you appear to assume should have skills well in excess of that trained and checked by the system. Personally, I have flown biplanes, WW2 aircraft, and heavy military singles as well as jets, I accept the constraints of those aircraft, as I now fly them as experimental, restricted or limited category, where the basis of their certification is understood by the words in the 21 Subpart H applicable statements. These aircraft do not provide the level of airworthiness that comes from Part 25, and that is fine.

Further comment:
The industry trains to a minimum standard, that is acceptable to the regulator. The airlines could train to higher standards, however, the competitive nature of the industry precludes undergoing astronaut type training for a regular line pilot. The line pilot gets to see components of a training matrix that covers the usual suspects, a fault with no FDE, faults with FDE and requiring reset of a system, faults that degrade performance, faults that degrade handling qualities. We get to practice ILS's which we do every day, and occasionally train on approaches that statistically end badly. We get to do RTO's, OEI's and the usual basics. Often these are assumed to be the limiting case but are not so. The pilots enter the system with varied background, from those that cleaned planes to go fly, or pumped gas for them, to those that the govt paid to do so, and those that could afford training by other funding. Sometimes the airlines HR department is the source of the feed stock and the processing of the new hire pilot. We see former military pilots in the same course as a baron pilot or a 200hr wet CPL/IR/ME ticket. The system trains these people to go fly low viz procedures down to CAT IIIB in short order, with LVTO and similar points of interest. The guys and girls generally do a credit to their background, and cope with what is thrown at them well. In many countries, they get paid less than subsistence wage and are or food stamps at that time. These people fly the high value payload, anyones loved ones from A to B in weather that includes thunderstorms, squalls, snow, hail, rain and shine. They turn up and undergo training as provided by the company. They are not responsible for what the company trains them on, they are the recipient of the training. If there is a deficiency in their training, don't blame the dead crew in the bottom of the smoking hole for not being trained to a level that would ensure that they can cope with unknown and unexpected events.

Every day around the world, the system generally works. It could be better, but making it better is not the responsibility of the 200hr copilot or 4000 Captain, they are the result of the system not the cause. If you are able to deal with every situation that may come along, then great for you. A number of pilots can do that, many will get close, and many won't deal with situations that have not been trained.

38 years of safety and accident investigation in the military and airlines, and the main takeaway IMHO is to keep things simple, and to understand that crews faced with events often do not respond as they do in the simulator.

Last edited by fdr; 27th May 2019 at 13:12.
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Old 27th May 2019, 12:43
  #131 (permalink)  
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Gosh.

That's all I could say for a moment. I don't think it's a case of having to choose between fdr and boofhead's posts, but one of again absorbing the vast width of the chasm between strongly held views.

fdr's post seems to give damning evidence that Boeing didn't come close to fulfilling the requirements but equally, boofhead shouts the truth. Nobody feels more strongly than I do for the ET FO, a kid living his dream, which suddenly turned into a nightmare. Still, it seems for one so inexperienced, he acquitted himself rather well. He'd have been a fine 3rd pilot, but to have this lad and a captain who's bulk experience seems to have been as FO on another type, then that aircraft was not carrying the much needed executives at the helm.
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Old 27th May 2019, 12:59
  #132 (permalink)  
 
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Jumbomax11 and fdf,
Thank you for your posts, which reflect sound insight and airmanship.
Many other posts here, from people who according to their published pedigree, should really know better and be a bit less affirmative in their appreciation of the deceased crews. Especially since we don't know yet what exactly happened in the cockpits.
So many crystall ball quarterbacks, even though we still don't know exactly what this MCAS function could actually do.

And maybe Boeing didn't quite know either before the crashes.
300+ flight test hours seems quite a long time to correct a simple "it's just the pilots" event. Things might not be so straightforward after all...
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Old 27th May 2019, 14:01
  #133 (permalink)  
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I don't want to leave this mornng's session having given the impression I'm biased to one 'side' or another. I'm not. I'm certain that Boeing will be held accountable for numerous shortfalls, but I'm equally certain the basic flying ability of some modern crews is woefully inadequate. They are just pressing on with their careers as best they can, it's the system that's wrong.
I can not imagine being in command of the MAX without the kind of background I had. Masses of empty sectors, and flying with people who loved to find out just what the aircraft would do. Neither of these scenarios happen much these days. Bums in seats and an electronic prefect connected to the fleet manager's office - where the SOP's line the shelves. Not my world, and not a background that can be simulated by a box on stilts.
In later copies of Handling the Big Jets, Davis (more or less) pleaded for crews to have an aircraft that they could throw around. A big stable electronic office teaches little.
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Old 27th May 2019, 15:02
  #134 (permalink)  
 
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Originally Posted by FlightDetent View Post
The MCAS kicks in, the nose gets heavier. You pull, and trim a bit. The MCAS kicks in again, the nose gets quite heavy, you pull and trim - more, for zero forces - to negate both of the MCAS inputs. If for nothing just to relieve the muscle tension.

Is it the shared view here, that neither of the doomed crew did the above? That they all instead of a good thorough spin just made a couple of "blips" and watched the A/C in VMC hit the ground? While pulling with possibly all four hands on the yokes, fighting the 4x increased elev feel computer and still neither of them touched the rocker switches to relieve that physical pressure, save for those blips?
(My boold in above, times are approximate due to FDR presentation).
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.

Above is not "blips" those occurred only at end when electric trim was re-activated.
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Old 27th May 2019, 15:49
  #135 (permalink)  
 
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Loose rivets, # 135,
Your certainty about the technical aspects is not necessarily the same certainty about pilot performance. Technology, aircraft design, and manufacture, can be judged against hard requirements, whilst humans have no published requirements for their ‘construction’, and where output performance is judged by other, ill-defined humans, in situations seldom related to extreme events.

Returning to the thread topic - trim runway procedure. It appears that knowledge of the procedure and training has decreased in recent years, with new variant aircraft. Yet technical views (# 105 737 Stuck Manual Trim Technique) question the increasing difficulty or effectiveness of the procedure in these newer variants.
These together with the lack of definitive response with quantifying line experience, only add to the unknowns in this topic.
Many test flights, revised revisions of the proposed modification, identification of a simulator discrepancy, and an external review of the procedure across previous variants.

Little or no certainty in any of these.

Not exactly the distinction between science and fiction; but not to judge a book (or person) by its cover




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Old 27th May 2019, 16:38
  #136 (permalink)  
 
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But.......who will write the reports? National authorities of the affected airlines.

Who are, of course, not "western".

The number of posts on these pages from boofhead, 737 Driver, yanrair et al., making the same point over and over again, must now be in the hundreds. (737 Driver averaged four-plus posts a day in his meteoric career, then abruptly vanished without a cry.) The accident aircraft were "flyable". Yes, but they quite clearly became less flyable by the second, as long as the crews failed to do the right thing. The crews did not follow correct procedures, Well, they were confronted with a rapidly worsening defect that they'd never been trained to recognize. Properly trained, competent pilots, not "children of the magenta line" should have coped anyway. Really? The simple fact is that as automated aircraft and simulator training have proliferated, and as the number of hours required to enter the right seat has declined, air safety has improved. The final accident reports will be a whitewash, err "westernwash". Hmm, cui bono here?

Why all this repetition? I am tempted to listen to the advice of that great strategist Auric Goldfinger: Once is happenstance, twice is coincidence, and...
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Old 27th May 2019, 17:32
  #137 (permalink)  
 
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Originally Posted by safetypee View Post


Returning to the thread topic - trim runway procedure. It appears that knowledge of the procedure and training has decreased in recent years, with new variant aircraft. Yet technical views (# 105 737 Stuck Manual Trim Technique) question the increasing difficulty or effectiveness of the procedure in these newer variants.
For those that performed trim runaway training in the sim, how was the exercice organized ?
Did the flight sim instructor throw in a surprise trim runaway in the middle of some other procedure, or was it just a matter of "now to the runaway trim", "Top, run the runaway drill !", "Good show, next exercice..." ?
Not exactly the same thing, is it ?
Additionally, any runaway would result in some degree of out-of-trim, otherwise that would not be a runaway. What degree of mistrim did you find manageable with the wheels ?
There must be a limit, albeit in the sim ?



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Old 27th May 2019, 17:43
  #138 (permalink)  
 
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Originally Posted by LowObservable View Post

Yes, but they quite clearly became less flyable by the second, as long as the crews failed to do the right thing.
I would suggest that you have this backwards. The longer the pilots flew through this malfunction (i.e. by applying trim with the yoke switch to counteract MCAS), the easier it was to understand what was going on. After about the 20th or 30th time you have to put in nose up trim only to watch MCAS put in nose down trim, I think even the most minimally trained crew could figure out that perhaps turning off the trim cutout switches was the reasonable course of action. The first Lion Air crew got this right. The Captain of the second Lion Air got this right until he turned the aircraft over to his First Officer and mistakenly assumed that the FO would continue to offset the MCAS inputs. The Ethiopian flight seems to be the true anomaly with a Captain who was by all appearances uncomfortable with hand flying and an FO who really didn't have the experience to jump in there and assist the Captain.

The simple fact is that as automated aircraft and simulator training have proliferated, and as the number of hours required to enter the right seat has declined, air safety has improved.
While the overall safety stats has improved, crew errors are becoming an increasing factor in the accidents that do occur. Some of this is due to the same human factors that have been around since the Wright Brothers, but some can be attributable to an increasing reliance on automation as a substitute, as opposed to a compliment, to basic flying skills. The fact that Ethiopian Civil Aviation Authority had no problem granting a 160-hour pilot a license to act as First Officer in a 737 ought to give everyone pause.
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Old 27th May 2019, 20:11
  #139 (permalink)  
 
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On the subject of trim, I saw that the FAA/EASA information on thumb switches on the MAX, which are trim limited, and that operations at the edge of the envelope would need to be manually trimmed.

Why would there need to be a limit on the thumb switch?
Smythe is offline  
Old 27th May 2019, 20:23
  #140 (permalink)  
 
Join Date: Jan 2004
Location: Far West Wessex
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While the overall safety stats has improved, crew errors are becoming an increasing factor in the accidents that do occur.

The preponderance of the evidence, it's true, is that the modern, automated and multiply-redundant airplane breaks less often than its tab-and-cable ancestor. Also, since the 1950s, we've stopped expanding the commercial airplane's flight envelope and focused on making it more reliable and more efficient. We have not re-engineered the human being in the same way.

Nonetheless, there's no evidence that the rate of catastrophic "crew errors" (see below) relative to the number of flight cycles has increased. That suggests that the "magenta line" theory of declining skills may be flawed.

Moreover, what people call a "crew error" usually isn't. It's an indication that crew selection, training and maintenance of competency fell short of what was required to handle an off-nominal situation, and it's consequently related to the degree of abnormality that faced the mishap crew.

Now, I am not sure that even the FTFA-fundies here would argue that the unwarned-against activation of MCAS - a running-in-background gadget that commandeered the most powerful effector on the airplane - wasn't quite severely abnormal. And did it occur on a highly automated airplane? Negatory, sir. It afflicted a Topsy-developed hybrid of a simple 1960s servo-mechanical jet with a 21st-century digital overlay.
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