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737-500 missing in Indonesia

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737-500 missing in Indonesia

Old 21st Jan 2021, 21:59
  #361 (permalink)  
 
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Yes, most of us have been trained for that scenario as well. I suspect you think of MCAS which is a slightly different animal. I can see how a system that starts and stops, starts and stops can confuse everything. Which it did, but it doesn’t belong in this discussion.
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Old 21st Jan 2021, 22:12
  #362 (permalink)  
 
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youre obviously an outstanding sim pilot. Maybe too good...
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Old 21st Jan 2021, 22:16
  #363 (permalink)  
 
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ManaAdaSystem

it wouldn’t stop the engine Captain. It would raise one to whatever thrust is needed on an aircraft with a short rudder arm. It would also make it roll quickly and unexpectedly. We were vfr when it happens to us and we simultaneously got a “wind shear” caution with audible. I’m not a simulator maverick so I probably suck, however, the double startle factor of a caution with a rolling motion made for an alarming scenario that we thankfully caught. Night in a a storm, it might be kind of hairy. Then again, you trained for it so you tell us Captain.
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Old 22nd Jan 2021, 00:00
  #364 (permalink)  
 
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4runner

Does on also see sequences that vary depending on the other autos that may be trying to compensate. What about pitch. etc.
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Old 22nd Jan 2021, 02:09
  #365 (permalink)  
 
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Your scepticism is understandable, but in view of the joint teams invited to participate, one would still expect a fairly decent report within a respectable time frame.

An international team dispatched to examine the plane’s recovered data and wreckage included four representatives from the U.S. National Transportation Safety Board, four employees from Boeing, two officials from the Federal Aviation Administration, and an aircraft engineer from GE Aviation. Two investigators from Singapore’s Transport Safety Investigation Bureau are also helping with the probe in accordance with a cooperation agreement among member states that make up the Association of Southeast Asian Nations
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Old 22nd Jan 2021, 02:48
  #366 (permalink)  
 
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The autothrottle theory has a 99.9% probability of being BS.
If the authorities are seriously considering it , well.............
Boeing autothrottles do not fail to idle in climb.
You can dispatch without it.
On rare occasions they can fail to come up evenly on hitting TOGA on take-off when a clutch doesn’t engage properly, but in climb , never.
How this theory got legs is a mystery.
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Old 22nd Jan 2021, 06:06
  #367 (permalink)  
 
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https://admiralcloudberg.medium.com/...6-e8bbc6683018

A reminder, albeit on a different aircraft, of how a sluggish engine can lead to a chain of events that do not end well.
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Old 22nd Jan 2021, 06:50
  #368 (permalink)  
 
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The later pitch (not AVIAT.) in this thread seems familiar to me ... and I don't like it.
Having said that and not flying heavy iron:
I can understand not noticing split throttles timely.
I can understand not noticing a rudder input by AP (which can be ruled out due to 2 channels only?)
I cannot understand not noticing a significant aileron input by AP during wings level climb.
Maybe some 737 classic driver can elaborate on that?
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Old 22nd Jan 2021, 07:20
  #369 (permalink)  
 
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Originally Posted by 4runner View Post
it wouldnít stop the engine Captain. It would raise one to whatever thrust is needed on an aircraft with a short rudder arm. It would also make it roll quickly and unexpectedly. We were vfr when it happens to us and we simultaneously got a ďwind shearĒ caution with audible. Iím not a simulator maverick so I probably suck, however, the double startle factor of a caution with a rolling motion made for an alarming scenario that we thankfully caught. Night in a a storm, it might be kind of hairy. Then again, you trained for it so you tell us Captain.
Exactly what did I say that triggered you in this way?
You donít see a difference between a AT cutback at low altitude when in a WS, and this accident which happened during climb at 11000 ft?
Well done getting out of your incident, but an engine failure in climb should never lead to an accident. Both throttles are set to climb thrust and one that retards to idle is less severe. Fact!
I have trained engine failures in a lot of diffrent situations. Climb and cruise are two of them. Iím not an ace, Iím just a well trained pilot.
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Old 22nd Jan 2021, 07:22
  #370 (permalink)  
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ATR CLUTCH

The ADSB info shows a modest performance level of the aircraft from quite early on after takeoff. The loss of control is abrupt, as it almost always is, but the lead up to it, if due to an asymmetry in thrust is not abrupt, it has been there for a considerable time. If so, there will be some long hard looks at standards.

SITUATIONAL AWARENESS

China Eastern was an abrupt event, the problem arose and caused a quick follow on to loss of control. The crew are startled and also not necessariy aware of the problem, an SA Level 1 type failure.

CI006 engine failure in cruise resulted in a decay of performance and while the crew were deliberating, the aircraft, well above it's 3 engine ceiling, lost speed, and the APLT lateral control diminished to the point the plane rolled over. an SA Level 3 failure of the engine loss, and an SA Level 1 failure related to the APLT aileron authority and airspeed decay.

Endsley (& Jones) came up with the taxonomies of Situational Awareness (SA) failures as:
  • Level 1: failure to correctly perceive the information
  • Level 2: failure to comprehend the situation
  • Level 3: failure to project the situation into the future
Level 1 failures can be cured in time, with warning systems and good training.
Level 2 failures need well-understood warning systems (Helios type problem) and good crew training
Level 3 failures need soul searching by the selection and training and monitoring systems. They are fundamental to the humans involved and are hard to defend against, and are latent failures within our systems at all times.

Endsley evaluated ASRS reports and found that:
  • 76.3% were Level 1 SA errors,
  • 20.3% were Level 2, and
  • 3.4% were Level 3
For one major airline, I evaluated their accident and incident database and found that 97% of all reports involved SA failures of one or more of the types. The only events that did not involve an SA failure of some sort were birdstrikes, and some mechanical failures that were correctly presented, perceived and responded to. On the hull loss cases, which there were far too many, involved almost always multiple forms of SA failure. Possibly the saddest case, an SA Level 3 failure, had 34 occasions in the last 30 minutes of the CVR where the crew showed they recognized the problem, but didn't recognize the impact on their flight path management and parked a billboard on the top of a hill, killing a couple of hundred people, the crew rather surprised when they saw the goats in the clouds. When a robust, reliable countermeasure for SA Level 3 failures arises, aviation will be a lot safer.

APLT CHANNELS

Apart from the curiosity of the A340-600, the majority if not all of the APLT fitted act as 2 axis autopilots, for flight path management. Only yaw damping is usually functioning by a rudder channel, or a torsion/load relief mode as in the B74 rudder. When configured to autoland, a rudder channel may be active for runway alignment manoeuver and rollout control, and a system such as the B777 and B787 Thrust Asymmetry Computer, TAC, may function. On most the yaw damper has a limited turn coordination function as well, however essentially APLTs function in 2 axis for operations, drivers feet still have a use.
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Old 22nd Jan 2021, 07:51
  #371 (permalink)  
 
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Originally Posted by fdr View Post
When a robust, reliable countermeasure for SA Level 3 failures arises, aviation will be a lot safer.
SOPs, ECAM, TCAS, GWPS, and other technological advances have made aviation vastly safer than it was a few decades ago. The only component that cannot be improved is the human mind. While these days it is politically incorrect to state the obvious, humans are NOT born equal. Some have better cognitive abilities than others, and even that can be split into many mental and motorical skillsets that make us up as individuals. I for instance can read very fast, well above average, however my handwriting borders on the illegible even with the greatest attention. Any training program by nature is designed for the average, with a line drawn at some minimum requirements below which the less skilled will fail. However there will always be individuals with marginal performance, and it is always a huge dilemma on where to draw the line. The lesson of the past 50 years is very clear. Rather than trying to improve the human, improve the automation to make the task easier. Of course it has taken all the fun out of the job (for those in the upper skills bracket), but it made, and continues to make things a lot safer.
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Old 22nd Jan 2021, 12:27
  #372 (permalink)  
 
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Andrasz

Yes, it is very clear, maintain piloting skills! Virtually every fatal accident in recent times has been caused by pilots that can't fly aeroplanes when presented with a unusual situation.
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Old 22nd Jan 2021, 12:31
  #373 (permalink)  
 
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aterpster

Jepp. I wonder how much line pilots could cope if unexpectedly faced with aerobatic maneuvering in IMC. As far as I know mainly prevention is teached. Once the ball (wing), is dropped stuff can go south in a hurry with no visual references.
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Old 22nd Jan 2021, 12:39
  #374 (permalink)  
 
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Unusual Attitude training in the sim plus a good, practiced, instrument cross-reference should cope with most thrust-roll scenarios (hypothesising here).
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Old 22nd Jan 2021, 12:43
  #375 (permalink)  
 
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EDLB

First and foremost, they should have not let it get asymmetrical. The acrobatic aspect could have easily been prevented.
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Old 22nd Jan 2021, 14:43
  #376 (permalink)  
Pegase Driver
 
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A question from someone who is not familiar with A/P-A/T technical data : is this failure scenario only possible with older A/T or are modern ones also all subject to this ? and can this also occur on Airbus where the throttles are normally not moving ? Just curious.
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Old 22nd Jan 2021, 16:11
  #377 (permalink)  
 
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It cannot happen on Airbus even if one thrust goes to idle because yaw damper will automatically try to stop the yaw although with limited authority and the spiral will be prevented by opposite aileron and spoilers. It will do a skidding turn to that side with a moderate bank. This is basic demonstration of OEI in simulator.
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Old 22nd Jan 2021, 18:08
  #378 (permalink)  
 
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As noted in previous posts, AT split is unlikely to generate a yawing moment beyond the aircraft capability. Also, this may require a significant change in thrust; e.g. recommencing climb, or intermediate level off, to result in clutch-slip.

The fin is more effective at high speed, vs thrust decrease with altitude.

The AP might have difficulty, but depending on roll power (no rudder servo), yaw - roll should be contained by the ailerons, thus maintaining heading - with slip.

LoC would require aerodynamic input; i.e. mistrimmed aircraft (no rudder or aileron AP autotrim ?). It is likely that the control indications with AP engaged would prompt the crew to add manual trim - with the AP engaged. Rudder trim might not be the first choice, particularly if the hand-wheel angle offset was large, indicating the amount of roll restoring force held by the ailerons; thus aileron trim might be applied.
All would be well until the AP ran out of authority - possible sudden disconnect, and / or the crew had to fly an out-of-trim aircraft without the normal zero-force wheel centre reference - requiring offset wheel force and position to maintain wings level.

I recall that a 737 suffered an upset, similar circumstances, but due to gross fuel imbalance during cross transfer (the aerodynamic / mass disturbance). The AP failed to fly a LNAV turn so the crew disconnected - surprise, big roll, high hand-wheel forces required to recover.
Searching (web and memory) for incident; probably UK AAIB investigation report - 20yrs ago?
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Old 22nd Jan 2021, 18:21
  #379 (permalink)  
 
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safetypee

"I recall that a 737 suffered an upset, similar circumstances, but due to gross fuel imbalance during cross transfer (the aerodynamic / mass disturbance). The AP failed to fly a LNAV turn so the crew disconnected - surprise, big roll, high hand-wheel forces required to recover.
Searching (web and memory) for incident; probably UK AAIB investigation report - 20yrs ago?"

Sounds like this one:

https://assets.publishing.service.go...pdf_501724.pdf
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Old 22nd Jan 2021, 18:41
  #380 (permalink)  
 
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safetypee

Your comments strike me as coming from one who has not flown the 737. If I’m mistaken, I apologize.

A pilot would not add aileron yaw with the A/P engaged. Asymmetric thrust can absolutely cause a roll that would exceed the ability to maintain heading.
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