Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Indonesian aircraft missing off Jakarta

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Indonesian aircraft missing off Jakarta

Old 16th Nov 2018, 07:16
  #1301 (permalink)  
 
Join Date: Apr 2009
Location: Sweden
Age: 44
Posts: 8
Originally Posted by Hi_Tech View Post
For all those questions about WHY this MCAS on B737 MAX fleet, the following link has a very nice easy to follow explanation with clear graphics written by a test pilot Bjorn Fehrm.
When you apply a lot of lipstick to an old lady like B737, something else goes wrong. Boeing had to do this change as the large engines made the aircraft stability to go wrong. Thanks Bjorn. I think it will clear up several questions about MCAS, STS, etc. in this forum.

link removed
Great explanation. Basically, bigger and more powerful donks hung further away/forward from centre of gravity. Larger nacelles potential "flipping-the-aircraft-around" effect in turns/high-AoA was then masked by undisclosed software patch which might have contributed to the crash.
One wonders why Boeing insists on keeping the basic wing unchanged. It would save them lots of headache if it could be moved up a bit (=enable GTF, make it less "flippable" etc.) (I suppose there are certification bills that prevented this, so more lipstick was applied )
Grunff is offline  
Old 16th Nov 2018, 07:54
  #1302 (permalink)  
 
Join Date: Feb 2000
Location: Alaska, PNG, etc.
Age: 56
Posts: 1,545
Originally Posted by Grunff View Post
One wonders why Boeing insists on keeping the basic wing unchanged.
Ummm, perhaps because they haven't. The wing area has grown 40% since the 100 thru 500, and the MAX wing has grown a smaller increment from the NG's
A Squared is offline  
Old 16th Nov 2018, 08:47
  #1303 (permalink)  
 
Join Date: Jan 2008
Location: australia
Posts: 114
Traditionally, aircraft designers negotiated certification rules with their regulator and, after agreed testing and analysis, senior company engineers assessed compliance. These engineers were called ''Designated Engineering Representatives'', appointed in their particular field of expertise as representatives of FAA. There were a few shameful abuses but generally the system worked.
On Boeing 787 delegation went further. It was first airliner approved under a new ''Organisation Designation Authorisation'' (ODA) arrangement, specifically intended to further reduce FAA involvement. Somehow hazardous lithium ion batteries slipped undetected through the new procedures.
NTSB was not impressed. Its Investigation Report 2014/AIR1401 concluded:
“Boeing’s electrical power system safety assessment did not consider the most severe effects of a cell internal short circuit and include requirements to mitigate related risks, and the review of the assessment by Boeing authorized representatives and Federal Aviation Administration certification engineers did not reveal this deficiency."
Boeing failed to incorporate design requirements in the 787 main and auxiliary power unit battery specification control drawing to mitigate the most severe effects of a cell internal short circuit, and the Federal Aviation Administration failed to uncover this design vulnerability as part of its review and approval of Boeing’s electrical power system certification plan and proposed methods of compliance."
"Unclear traceability among the individual special conditions, safety assessment assumptions and rationale, requirements, and proposed methods of compliance for the 787 main and auxiliary power unit battery likely contributed to the Federal Aviation Administration’s failure to identify the need for a thermal runaway certification test.”
737 Max is second Boeing certification under ODA.
In 2015 DoT Office of Inspector General Audit Report AV-2016-001 on ODA found
“...one aircraft manufacturer (presumeably Boeing) approved about 90 percent of the design decisions for all of its own aircraft"
".
... largest ODA oversight office—which is dedicated to Boeing and encompasses about 40 staff—is not currently included in FAA’s staffing model"
". .... FAA expects to add this office to the model by October 2015 and have an initial forecast available by fiscal year 2016. Until then, FAA does not know whether it has adequate staffing levels"
".....
ODA oversight team findings are often not related to high-risk issues—e.g., issues that could directly impact the potential loss of critical systems or other safety concerns"
".
... industry representatives expressed concern that FAA’s focus was often on paperwork—not on safety-critical items.”
All rather alarming

Last edited by ozaub; 16th Nov 2018 at 08:55. Reason: formatting went awry
ozaub is offline  
Old 16th Nov 2018, 09:01
  #1304 (permalink)  
 
Join Date: Aug 2003
Location: FR
Posts: 222
And how independent are EASA (and others) from the FAA? If the FAA have missed a critical issue, what are the chances that the other certification authority will catch up? I don't know how this works, just asking.

Edited to add: does EASA also now have a "ODA" equivalent, or do they have something to say regarding this new process.
pax2908 is offline  
Old 16th Nov 2018, 09:18
  #1305 (permalink)  
 
Join Date: Jan 2008
Location: uk
Posts: 802
Originally Posted by pax2908 View Post
And how independent are EASA (and others) from the FAA? If the FAA have missed a critical issue, what are the chances that the other certification authority will catch up? I don't know how this works, just asking.
For EASA-FAA, bilateral agreements mean that each basically rubber-stamps the other's approvals. They are, however, completely independent organisations and each has its own rubber stamp.
infrequentflyer789 is offline  
Old 16th Nov 2018, 09:31
  #1306 (permalink)  
 
Join Date: Dec 2001
Location: Leeds, UK
Posts: 281
And to weasel out any other undocumented changes made to the MAX, Boeing should offer all their employees past and present access to an anonymous whistleblowers hotline run by a third party. You can bet any similar engineering shortcuts generated lots of discussion in the company at the design stage, until Engineers got overruled by managers and commercial people.

G
groundbum is offline  
Old 16th Nov 2018, 10:31
  #1307 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,347
Originally Posted by LDRA View Post
It is quite bit more than shaky.

The way the system is architectured means if the AOA on standby side fails, it may be undetected and henced unfixed, since it is not used for function. The failure becomes latent. Now when the active control side AOA fails after, you have BOTH AOA faulty. Flight crew would have no chance to even diagnose the issue themselves.

That is why the industry standard approach is to have system detect and respond/announce to failure in real time
If the AOA on the 'standby' side fails - that is the one that is not feeding the MCAS then the result is a UAS because the ADIRUS are fed by both. When a technician gets a UAS report from the crew the first things to check (as in the first thread posts here) are pitot covers left on - or static vent blocked. But it was the AOA information that was incorrect. I would have thought an AOA disagree would lead to failing both AOAs (it is not possible in the air to detect which is right) and the ADIRUS stop using them and a warning is provided to the crew. Ideally there should be logic (discussed in the thread above) to calculate from other flight parameters the likely AOA and use that value to identify the bad AOA sensor and fail it.
Ian W is offline  
Old 16th Nov 2018, 10:32
  #1308 (permalink)  

Plastic PPRuNer
 
Join Date: Sep 2000
Location: Cape Town
Posts: 1,890
One things that stands out to a non-pilot high-hours PPruNer is that how many of these nasty incidents involve:
1) Autotrim, and (to a lesser extent),
2) Autothrottle

Mac

These highly automated aircraft are not adequately annunciating to the operator
mode-changes; their reason, and consequences/effect on other systems.

:-(
Mac the Knife is offline  
Old 16th Nov 2018, 10:37
  #1309 (permalink)  
 
Join Date: Mar 2014
Location: Auckland nz
Posts: 141
Originally Posted by LEOCh View Post
The Leeham News article is quite informative of why the MCAS is required on the MAX, and fills in some blanks. I originally thought heavier engines further forward should if anything bring COG forward (unless balanced by other modifications), creating a more longitudinally stable MAX. However the idea that at high AoA the nacelles become aerodynamic surfaces sufficient to longitudinally destabilise the aircraft is interesting. It's a big aside, but a similar problem was noted on the WWII Supermarine Spitfire. As development to more powerful engines dictated more and more propeller blade area, the non obvious effect of this as an aerodynamic surface way forward of the aerodynamic center caused degraded longitudinal stability margin.

So when you are at high AoA, your MAX may become pitch divergent (without MCAS). At the same time you are likely to be slow but with high thrust beneath the wings, pitching you upward into the stall.

One thing that keeps coming up considering how much importance the AoA signal now has in the MAX, is whether there is redundancy in the two vanes. I think the answer is not really, as many conditions (rolling, yawing!) will lead to expected AoA disagree between the two sides of the nose. A warning (i.e. stick shaker) based on a single high alpha vane is reasonable, but any kind of consensus signal from two vanes only with severe consequence for faulty data is quite problematic.

So the current two vanes are really only one sensor for the purposes of redundancy. I wonder whether to have such a high degree of reliance on a AoA signal you should incorporate three vanes on each side.

So much here but let's focus on this:

" I originally thought heavier engines further forward should if anything bring COG forward (unless balanced by other modifications),"

They were not just forward but also up. That's significant becaue the line of thrust against drag becomes way more active in pitch up, hence the need for MCAS to maintain the stability in longitudinal pitch in conditions of flight that required it.
Lord Farringdon is offline  
Old 16th Nov 2018, 10:53
  #1310 (permalink)  
 
Join Date: Feb 2000
Location: Alaska, PNG, etc.
Age: 56
Posts: 1,545
Originally Posted by Lord Farringdon View Post
They were not just forward but also up. That's significant becaue the line of thrust against drag becomes way more active in pitch up, hence the need for MCAS to maintain the stability in longitudinal pitch in conditions of flight that required it.
No, actually, raising the thrustline of underslung engines would decrease the tendency of a power application to cause a pitch-up.

The reason for the pitch instability is the aerodynamic effects of the engine nacelles. At low (cruise) AoA the nacelles produce little or no lift, by design. At high AoA, they begin to produce lift. Because the MAX nacelles are mounted further forward, the lift produced by the nacelles at high AoA is further ahead of the wing, thus providing a pitch up tenancy. Effectively this shifts the center of lift of the wing-engine assembly further forward, whcih reduces pitch stability at high AoA, and reduce control force gradient for pitch-up control inputs.
A Squared is offline  
Old 16th Nov 2018, 11:16
  #1311 (permalink)  
 
Join Date: Jul 2007
Location: Germany
Posts: 533
Originally Posted by Mac the Knife View Post
One things that stands out to a non-pilot high-hours PPruNer is that how many of these nasty incidents involve:
1) Autotrim, and (to a lesser extent),
2) Autothrottle

Mac

These highly automated aircraft are not adequately annunciating to the operator
mode-changes; their reason, and consequences/effect on other systems.

:-(
In hindsight you can often find issues with annunciations, but it is a highly non-trivial problem. Cognitive overload is a huge issue, and a lot of effort is put into answering the questions of what information to present to the pilots at what time. Lots of pieces of information are intentionally withheld in certain phases of flight in order not to distract the pilots unnecessarily. In many cases with highly integrated electronics, a lot of this information can later be recalled on a computer display in the cockpit to assess which system are affected by a certain failure.

After the event it is often easy to say "If only the pilots had known X when Y happened! Why didn't the aircraft tell them?"

To appreciate the near-impossibility of the task of designing cockpit information systems, try to make a list of parameters which may become supremely important to know at some point. Then make a list of critical scenarios and try to cross-reference the parameters with the scenarios. You will most likely end up with dozens, if not hundreds of parameters and small events that might be extremely important to know for almost all scenarios. But with humans being cognitively limited, it is impossible to present all of them, or even a majority. A decision to limit display (or aural or tactile annunciation) to a handful of parameters must be taken, also taking into account the probability that any of these parameters may be wrong.

These day such tasks involve cognitive psychologists, human-factors and human-machine-interface specialists, perhaps even sociologists, besides engineers and pilots. But by the very nature of the problem, these decisions cannot be perfect.

Bernd
bsieker is offline  
Old 16th Nov 2018, 11:34
  #1312 (permalink)  
 
Join Date: Jul 2008
Location: Dubai
Posts: 61
Originally Posted by Lord Farringdon View Post
1. Has this been posted before? If so apologies. If no why not?


737fixer
November 14, 2018 Here is the procedure for Runaway trim from my companies MAX QRH. The revision Date is July 2017.

1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
■ ■ ■ ■
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
– – – – – – – – – – – – – –

That procedure WILL stop MCAS or any trim from operating the trim motor.



2. Was this the procedure available for Lion Air ie was it in their QRH too?
3. If it was perhaps that's the reason the other crews got out of this mess or alternatively perhaps that's why the 'possible' presence of a mech on the flight deck of the accident flight had a unwarranted influence in the outcome in that flight.
4. Plain as day the MAX will be the very last 737 series ever built. (Am I right? ) In order to achieve better fuel efficiency they fitted larger engines and turned a relatively stable frame into an unstable one and needed to 'augment' it to fly in some parts of the envelope.
5. Not telling aircrews that an augmentation system was introduced to the air frame that not only pitched the nose down in some unlikely flight regimes but also deliberately resisted the crews attempts to counteract it unless all the QRH procedures were followed to the end is really is ....well....litigious.
7.FAA certification of this frame on the basis of grandfathering systems while introducing an entirely counter intuitive system without training promulgation or QRH specifics (AD now issued) in order to meet economic requirements is ..well also litigious!!
I cannot gulp this. If the date of QRH JULY 2017 is true, why FAA had to issue AD this month and Boeing issue a special Memo to all airlines. We are living in the Fake news era. Why Fixer is not saying which airline QRH had this info?
I am not convinced about this post.
Hi_Tech is offline  
Old 16th Nov 2018, 11:42
  #1313 (permalink)  
 
Join Date: Aug 2009
Location: Seat 0A
Posts: 516


I'll do you one better, that procedure is unchanged since the classic 737!
Proof from Rev 31 of the 737 300-500 QRH straight from Boeing, dated June 14, 2013...

This is not only the age of 'fake news', but more importantly the age of people publishing things, be it in the media, or 'just' on a forum somewhere on the internet, without knowing what they are talking about or doing a minimum amount of research beforehand. Thats why I wrote a few posts ago that all this talk about the 'shocking revelation' that Boeing is 'withholding information' about MCAS is absolutely silly - especially since we still don't know what happened to this particular plane.
STBYRUD is offline  
Old 16th Nov 2018, 11:47
  #1314 (permalink)  
 
Join Date: Mar 2009
Location: Phoenix, AZ USA
Age: 62
Posts: 0
Originally Posted by PashaF View Post
Hm... 5 minutes of struggle is an evidence if you look at it from psychological point of view.
Several minutes are the exact timetable needed to go through emergency checklist and only after that the pilots were free to start thinking on their own.
What would they do? We also know that it was virtually impossible to pinpoint an electronic component as the source of disaster, and moreover, modern pilots are not comfortable with fuse boxes melding.
I assume that they attempted to use manual wheels to adjust the trim, presumably, while applying their combine muscular power.
Can we also assume that electric motor was keep trimming in opposite direction?
If so, this man versus machine struggle could end with only one (not that unusual) scenario. Control cable snapped and machine was left to trim as it wishes.
Why do you assume blindly that you have "five minutes of struggle". Since normal pitch and power settings would generate a climb it's much more likely that the decision to maintain level flight was intentional for reasons unknown until the CVR is recovered. The initial flight profile was almost identical to the flight the previous evening but instead of continuing to climb out it appears that a decision was made to level off (in preparation to return?)...If/when the CVR is recovered I believe it's very likely that the interaction of the technician and the flight crew will be a critical aspect of the tragedy and crucial to understand why they broke from established procedures for dealing with the perceived issue.
SLFinAZ is offline  
Old 16th Nov 2018, 11:56
  #1315 (permalink)  
 
Join Date: Mar 2014
Location: Auckland nz
Posts: 141
Post Deleted
Lord Farringdon is offline  
Old 16th Nov 2018, 12:07
  #1316 (permalink)  
 
Join Date: Jul 2008
Location: Dubai
Posts: 61
Sorry. I did not mean your post was fake news. I was only pointing out an anomaly with 737Fixer's post, and why I cannot gulp it.
Hi_Tech is offline  
Old 16th Nov 2018, 12:24
  #1317 (permalink)  
 
Join Date: Jul 2014
Location: St. Petersbourg
Age: 35
Posts: 37
Originally Posted by SLFinAZ View Post
Why do you assume blindly that you have "five minutes of struggle". Since normal pitch and power settings would generate a climb it's much more likely that the decision to maintain level flight was intentional for reasons unknown until the CVR is recovered. The initial flight profile was almost identical to the flight the previous evening but instead of continuing to climb out it appears that a decision was made to level off (in preparation to return?)...If/when the CVR is recovered I believe it's very likely that the interaction of the technician and the flight crew will be a critical aspect of the tragedy and crucial to understand why they broke from established procedures for dealing with the perceived issue.
Well, it is clear that initial event was followed by a period of controllable flight. Were this period ended with initial event degradation or another catastrophic event is a mystery so far.
As for technician-crew interactions, i don't think there were any. Technical guy mission (most logically) was not consulting but observation.
PashaF is offline  
Old 16th Nov 2018, 12:44
  #1318 (permalink)  
 
Join Date: Apr 2008
Location: The sunny side
Posts: 30
Originally Posted by ozaub View Post
Traditionally, aircraft designers negotiated certification rules with their regulator and, after agreed testing and analysis, senior company engineers assessed compliance. These engineers were called ''Designated Engineering Representatives'', appointed in their particular field of expertise as representatives of FAA. There were a few shameful abuses but generally the system worked.
On Boeing 787 delegation went further. It was first airliner approved under a new ''Organisation Designation Authorisation'' (ODA) arrangement, specifically intended to further reduce FAA involvement. Somehow hazardous lithium ion batteries slipped undetected through the new procedures.
NTSB was not impressed. Its Investigation Report 2014/AIR1401 concluded:
“Boeing’s electrical power system safety assessment did not consider the most severe effects of a cell internal short circuit and include requirements to mitigate related risks, and the review of the assessment by Boeing authorized representatives and Federal Aviation Administration certification engineers did not reveal this deficiency."
Boeing failed to incorporate design requirements in the 787 main and auxiliary power unit battery specification control drawing to mitigate the most severe effects of a cell internal short circuit, and the Federal Aviation Administration failed to uncover this design vulnerability as part of its review and approval of Boeing’s electrical power system certification plan and proposed methods of compliance."
"Unclear traceability among the individual special conditions, safety assessment assumptions and rationale, requirements, and proposed methods of compliance for the 787 main and auxiliary power unit battery likely contributed to the Federal Aviation Administration’s failure to identify the need for a thermal runaway certification test.”
737 Max is second Boeing certification under ODA.
In 2015 DoT Office of Inspector General Audit Report AV-2016-001 on ODA found
“...one aircraft manufacturer (presumeably Boeing) approved about 90 percent of the design decisions for all of its own aircraft"
".
... largest ODA oversight office—which is dedicated to Boeing and encompasses about 40 staff—is not currently included in FAA’s staffing model"
". .... FAA expects to add this office to the model by October 2015 and have an initial forecast available by fiscal year 2016. Until then, FAA does not know whether it has adequate staffing levels"
".....
ODA oversight team findings are often not related to high-risk issues—e.g., issues that could directly impact the potential loss of critical systems or other safety concerns"
".
... industry representatives expressed concern that FAA’s focus was often on paperwork—not on safety-critical items.”
All rather alarming
A rather negative view of the systems being introduced by ODA, which assumes it will be worse than before.

A certifying authority either has to: use its own staff to verify every compliance document provided by the manufacturer, or; approve designees at the manufacturer to do some of this work, or; issue an approval to the manufacturer to self-comply some of this work. No certifying authority in the world uses the 1st method, as it would require a huge staff at a huge cost and puts no trust at all in the manufacturer. The FAA uses the second method, where employees of the manufacturer hold designations to do work on behalf of the FAA - not exactly an independent system as the designee wears two hats, but is a proven and safe system. Now in addition the designee system is further formalized and overseen by the FAA under the ODA system. EASA uses the third method, where the manufacturer holds an approval and is made responsible for its actions, has to have procedures in place, has to use independent Certification Verification Engineers to double check its own work, and is audited by EASA. Both the FAA and EASA are increasing the 'privileges' of the manufacturer based on risk philosophy; what is the point of the authority wasting its time on checking low risk and mundane items when it should be focusing its direct involvement on higher risk certification items - get the ODA or the DOA to do the mundane work to allow the authority to concentrate on safety issues.

These systems are known to be safe, but no system can ever be infallible as there is always people involved........
FiveGirlKit is offline  
Old 16th Nov 2018, 13:19
  #1319 (permalink)  
 
Join Date: Jul 2013
Location: Within AM radio broadcast range of downtown Chicago
Age: 67
Posts: 225
FiveGirlKit: "...rather negative view of the systems being introduced by ODA, which assumes it will be worse than before"

Just to amplify the explanation, in a limited context - the type certification of the 787 batteries proceeded under a Special Condition, which (IIRC) FAA uses for relatively new and advanced kinds of technologies. Seems logical that if an extension or modification of existing airworthiness type certification rules and regulations is needed because of new "stuff" being used in the airplane, tbe regulator is wise to acknowledge, and rely upon, expertise in the manufacturer - subject to proper agency-company interaction at all times.

Not trying to steer anyone into thread drifts, yet at the same time, heaping dirt on certification processes overall is imho quite premature - and too little is known as yet to start aligning this tragedy with the 787 battery problems.
WillowRun 6-3 is offline  
Old 16th Nov 2018, 13:21
  #1320 (permalink)  
 
Join Date: Jul 2003
Location: An Island Province
Posts: 1,116
Re checklist for trim runaway. The top line states the condition as ‘uncommanded’ trim movement. But in the MAX, at any time that MCAS is active, then the trim can move, being perceived ‘as uncommanded’; what then should a crew do ?

Even with detailed knowledge of the system, trim movement in a high workload situation demanding close attention at low speed, manoeuvring, or increasing thrust environment, the crew may not have sufficient mental capacity to recall the nuances of a complex sub system to judge normal or abnormal MCAS operation.

Associated system alerts can aid recognition of a failed state, but such assessment requires effortful thought in a time critical situation. The task has added complexity of opposing cues such as stick shaker requiring nose down pitch, airspeed comparison do nothing, or trimmed condition increasingly nose-down requiring urgent nose-up intervention.
Add to that the possibility of different annunciations or pilot interpretations across flight deck - what then CRM !

A complex, tight-coupled, intractable system, often cited as central themes in hazardous conditions.



alf5071h is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.