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

Indonesian aviation is well known for their training deficiencies. An LCC is probably not an exception. We will always speculate...That's human nature.

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.

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?

That last chart looks like it was "borrowed" from the Wikipedia article https://en.wikipedia.org/wiki/PID_controller

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

Not on a 737, full yoke movement is available without gymnastics.

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.
.

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 ?

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".

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.

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

https://cimg0.ibsrv.net/gimg/pprune....524b536e1a.png

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.

Looks like Boeing are being "tactful"

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

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.

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.

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?

sounds like at least it's predictable/correctable, so where would it get the information to pick a better trim?

Exactly one of the objectives of the 25.1329 amendment that the 737 does not have to comply with, thanks to a deficient 21.101 Changed Product Rule

etudiant, a pedantic clarification of your design concept.
The design requirements for large aircraft specify limits for autopilot performance (FAR / CS 25).
Generally any single autopilot malfunction (not the same as A/T) should not result in the aircraft being ‘significantly’ out of ‘trim’ - vs ‘huge’ and ‘unstable’.
The descriptive term ‘significantly’ involves subjective interpretation of what a suitably qualified pilot without need of special skills / knowledge or strength will be able to manage.

The aircraft requirements do not specifically consider combinations of systems, except within the overall requirement for an adequate level of safety (usually a numerical probability).
The level of safety for interacting malfunctions - A/T or engine, and autopilot, often depend human intervention (subjective probability).
With A/T malfunction the autopilot may struggle. However, because the resultant flight path is not caused by an autopilot malfunction, the certification aspects of the combined effects with engine malfunction may use pilot awareness and action to meet the required level of safety.

Whereas aircraft have to meet design requirements (hard science), no such requirement exists for humans.
The human contribution is usually judged subjectively (soft science) - non numerical probability, a certification opinion, an assumption about human performance in a given situation.

Many accidents and events involve the human contribution. Increasingly outcomes are inappropriately attributed to error or individual’s ability; neither has meaning in certification, nor in operational investigation.
All that might be concluded is that there appears to be a mismatch of certification expectations of crews’ contribution, and that achieved in the situation encountered; where the situation must also consider the technical malfunction.

We cannot tell if certification has misjudged crews’ abilities to respond, or that crews’ abilities were sufficient, have changed, or situations have evolved, more prevalent, including a range of interacting contributing factors, aircraft / system age, maintenance, airworthiness safety monitoring.
The interaction of quantitative and qualitative assessments cannot be judged in isolation because of the complexity of the overall situation: -
‘ seriously askew’ - yes, a mismatch between the situation as perceived by the crew and subsequent (in)action, and the assumptions of these by certification before the event, or as reviewed with hindsight after the event.