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737-500 missing in Indonesia

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737-500 missing in Indonesia

Old 13th Feb 2021, 12:01
  #601 (permalink)  
 
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Very interesting.
We have heard here that the crew should have noticed the large control wheel movement before the AP disconnected.
The aircraft was supposed to turn right in the timeframe just before the upset. Therefore the crew would expect some amount of right control wheel movement.
I don't know the speed at which the AP put in right aileron, ie how long time passed between say 10 degrees right control wheel position and reaching 20 degrees limit position?
Should a 10 degree right control wheel position raise any alarm from the pilots when the pilots expected some level of right control wheel movement due to right turn put into the AP? If no, how much movement should raise an alarm? How long time would pass from the "alarm threshold" position until AP disconnect?
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Old 13th Feb 2021, 12:15
  #602 (permalink)  
 
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mikehallam

I thought it was the AP disconnecting that initiated the roll as the AP aileron input disappeared when it disconnected. so it could have been replaced manually by the pilot
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Old 13th Feb 2021, 16:59
  #603 (permalink)  
 
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Indonesian aviation is well known for their training deficiencies. An LCC is probably not an exception. We will always speculate...That's human nature.
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Old 14th Feb 2021, 02:47
  #604 (permalink)  
 
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BuzzBox

IIRC, the autopilot on the older vintage Boeings have limited authority so that an autopilot hardover failure is controllable and no worse than an engine failure.
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Old 14th Feb 2021, 16:14
  #605 (permalink)  
 
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The automation debate is always going to pop up but with proper training and good airmanship a pilot should be expected to be able to override the automatics and disconnect then stabilise the flight path. I would refraim from judging the crew as they have paid the ultimate price and more importantly lessons need to be learned from this accident.
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Old 14th Feb 2021, 16:57
  #606 (permalink)  
 
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Regarding the search for the CSMU.

Under present circumstances where the ULB has been dislodged from the mounting brackets on the drum-shaped stainless steel enclosure of the small (100mm OD x 100mm ?) CSMU and the (bright orange w/ reflective tape markings) CSMU has been separated from the main housing of the CVR device, are the underwater dive teams restricted to visual/tactile search methods while scouring the sea bed?

Or does submersible technology exist that is capable of locating a stainless steel component (which may be made of an SS with properties that are not strongly responsive to magnetic field detection) at some depth below the surface of the sea bed amidst a debris field made up of aluminum and other metallic objects?
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Old 15th Feb 2021, 09:44
  #607 (permalink)  
 
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That last chart looks like it was "borrowed" from the Wikipedia article https://en.wikipedia.org/wiki/PID_controller
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Old 15th Feb 2021, 19:34
  #608 (permalink)  
fdr
 
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No, it is from a controller theory textbook, and it correctly describes the curves which oddly wiki doesnt. Have another look, the wiki formulas are correct, the graphs have messed up labelling

Last edited by fdr; 15th Feb 2021 at 20:39.
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Old 15th Feb 2021, 21:18
  #609 (permalink)  
 
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Getting a full aileron deflection requires a rotation of the yoke by far enough that the crew's arms become restrictions to the immediately available aileron deflection, and a change of hand position can be required
Not on a 737, full yoke movement is available without gymnastics.
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Old 15th Feb 2021, 22:30
  #610 (permalink)  
 
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A briefing today indicates that additional divers with skills and support equipment to enable extended dive periods (Technical Divers) have been assigned to assist KNKT in the search for the CVR memory module.
.
Search for CVR Sriwijaya Air SJ182 Continues, Navy Deploys 34 Divers
By Luqman Nurhadi Arunanta
DetikNews 2021.02.15 15:19 WIB

The search for Sriwijaya Air SJ182 cockpit voice recorder (CVR) continues. The Navy also deployed 34 divers from the Underwater Dive and Rescue Service (Dislambair).

"Dislambair has prepared 34 personnel who will continue the search for CVR in support of the search operation held by KNKT," said Kadislambair Koarmada I, Marine Colonel Wahyudin Arif in his statement, Monday (2/15/2021).

"We have already done planning with KNKT including technical dives that will be carried out so that it is expected that the search can be carried out as effectively as possible taking into account the weather and the safety of the personnel in the field," he explained.

... In addition to diver personnel, the Navy has prepared safety support devices in the form of ambulance cars and Mobile Diving Chamber (MDC) that are standby there," he said.

"Mobile Diving Chamber (MDC) is accompanying the navy dive team personnel as life support. So divers are psychologically calmer, if problems occur they can be dealt with quickly," he said.
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Old 16th Feb 2021, 22:12
  #611 (permalink)  
 
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Now it is the 2nd time in Indonesia a function airplane crashed because of maintance issues.
First it was the max sorry guys but really contact spray will solve it ? I never used contact spray as a repair you replace the module!
Does boeing have so much issues with connectors ?
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Old 17th Feb 2021, 12:26
  #612 (permalink)  
 
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No one knows why it crashed, but maintenance issues are unlikely. The fact is air crew should be able to diagnose and contain "normal failures". Memory items address time critical issues and the QRH is the shortest form of actions prescribed by the manufacturer. Statistically only a very small percentage of crashes are not caused by pilot error, albeit by compounding the situation by taking actions outside of the recommended or failing to diagnose the issue correctly and doing the completely wrong actions for the phase of flight. Sounds harsh, but this will be a "pilot error".
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Old 17th Feb 2021, 13:06
  #613 (permalink)  
 
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Kirks gusset

"No one knows why it crashed, but maintenance issues are unlikely."

No one knows why it crashed, but maintenance issues are unlikely to have been the primary cause.
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Old 17th Feb 2021, 17:00
  #614 (permalink)  
 
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fdr

I had another look. It's very obviously the same image with some photoshopping. The labels on the wiki graphs are correct, the ones in your copy are incorrect. You need to read the captions to the graphs.

I'm certain that someone who didn't understand the charts copied them from wikipedia and then incorrectly altered them.

It looks like your "controller theory textbook" ripped the image from here https://theautomization.com/pid-cont...detail-part-2/. I can still see remnants of the red and green caption.

https://en.wikipedia.org/wiki/PID_co...ge_with_Ki.png


Last edited by donotdespisethesnake; 17th Feb 2021 at 18:05. Reason: Now I am sure it is an incorrect copy
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Old 18th Feb 2021, 08:37
  #615 (permalink)  
 
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For the ‘split thrust lever’ or ‘asymmetric power’ views, see the HF section of the PSM+ICR report, which considers events from the Boeing Engine Malfunction database.
There are 7 throttle and 8 instrument related events in the category ‘Failure to monitor throttle position and engine parameter display.’
These might moderate some of the extreme hindsight biased expectations of human perception. People are not very good monitors, do not observe what we see as obvious after the event, are distracted, suffer fixed mindset, over-focus or react to apparently irrelevant aspects, … etc,

Selected texts;
- #1 eng. throttle retarding toward idle while #2 throttle remains at high thrust level.
- #2 eng. throttle jammed at 94% while #1 eng throttle slowly reducing power under A/T command.
- Failed to notice #2 eng throttle position when diagnosing problem in #1 eng.
- #2 eng. throttle stuck at idle during level off while #1 throttle advanced with A/T engaged; A/P holding left aileron; airplane began to bank right
- #1 eng. went sub-idle during level off at cruise and was not detected for over seven minutes; throttle split, airspeed bleed off, finally 15 degree bank when A/P could not compensate for asymmetric thrust.
- Crew failed to note that #4 eng. had gone sub idle while engines controlled by A/T.
- None of the three pilots on flight deck noticed that #2 throttle had inadvertently been displaced below full power.
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Old 18th Feb 2021, 13:54
  #616 (permalink)  
 
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Looks like Boeing are being "tactful"

https://www.reuters.com/article/us-i...-idUSKBN2AI00X


“Continual crew awareness of airplane attitude, airspeed, flight control position and thrust settings is fundamental for airplane upset prevention and can reduce the effect of startle or surprise caused by rapid unexpected changes,” the bulletin said.
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Old 18th Feb 2021, 23:30
  #617 (permalink)  
 
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That advice is basic PPL level stuff, watch your airspeed, check your pitch attitude and monitor the engine. It’s concerning that it needs to be given to pilots flying sophisticated airliners. It should be well ingrained by the time you move up from a two seater single engined trainer.
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Old 19th Feb 2021, 11:03
  #618 (permalink)  
 
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Re ‘… is basic PPL level stuff, watch your airspeed, check your pitch attitude and monitor the engine‘.
This is often repeated under the title - Monitoring; monitor everything all of the time, which of course is impossible particularly where humans are poor monitors.

The deficiency is not knowing what the priority parameters are and how these will differ according to the situation; what to monitor and when.
Also, not knowing how to monitor - the mechanism of observing; how much deviation from the norm or closeness to an extreme, rate of change, patterns involving several displays - situation awareness.

Much of this experience can be acquired from normal operation, but it requires effort to observe, relate, and remember. This is often over shadowed by less meaning-full routine tasks - calling out the norms (but do we check), and the rarity of situations requiring intervention alerted by monitoring.

We know what is right, but less so what is a deviation, we lack a database of examples of adverse situations - to be learnt, on the job knowledge.
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Old 19th Feb 2021, 23:46
  #619 (permalink)  
 
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Is there not something seriously askew with the design concept when the autopilot simply hands back the airplane in a hugely unstable configuration to the unsuspecting pilot?
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Old 20th Feb 2021, 01:20
  #620 (permalink)  
 
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sounds like at least it's predictable/correctable, so where would it get the information to pick a better trim?
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