Posts by user "syseng68k" [Posts: 35 Total up-votes: 0 Pages: 2]

syseng68k
June 19, 2025, 12:33:00 GMT
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Post: 11905987
I guess it depends on the model, as there are three position versions where the center position is valid, but that uses a different cam profile. For the one here, just confirmed, the toggle always finds one side or the other. The cam profile is circular, and it doesn't seem possible to balance in the middle. The cam section is separate to the threaded section. Might be a press fit initially, but is also staked either side. Have seen one of these where the cam section was loose, but still not possible to override the cam. A simple, but very effective bit of design work, IMHO.

Subjects: None

syseng68k
June 19, 2025, 13:42:00 GMT
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Post: 11906029
Switch Problems

Dunno, the discussion around the switch as a failure point looks spurious to me. With that used to support the idea that a possible engine shutdown was due to the master fuel valve closing.

I don\x92t really buy that, since we don\x92t know at this stage whether the engines did in fact fully shutdown, or were commanded to spool down to idle, or other lower thrust setting, both of which would produce the same result. Thoughts ?.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Engine Failure (All)  Engine Shutdown

syseng68k
June 19, 2025, 15:43:00 GMT
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Post: 11906130
Thanks. The next question being: With both engines at idle, will there still be enough hydraulic and electrical power generated ?. Might depend also on aircraft mode, ground / air, takeoff / landing etc.

I guess the underlying point i'm digging at is that not only the fuel shutoff valve and control has authority over the engine. Many a/c subsystems will be connected together via an aircraft data bus, (or local area network, in compute terminology). and will need access to the FADEC for many reasons. Just as home wifi allows multiple users to access a shared resource, most modern complex systems are networked to supervise and share data.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FADEC

syseng68k
June 19, 2025, 15:59:00 GMT
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Post: 11906143
hans brinker:

Thanks for that. Should be obvious, I guess.

Subjects: None

syseng68k
June 20, 2025, 11:11:00 GMT
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Post: 11906846
Lead Balloon:

A bit of background on real time computing might help here. Apologies if some of this is tldr, obvious, or a simplification.. The FADEC must monitor the local environment, calculate and control, various aspects of engine operation. eg: baro pressure, temperature, fuel, speed control, overtemp, as well as respond to external commands (speed, start / stop etc) and provide operating status reports in real time, to other parts of the a/c. It really is a complex, semi autonomous system in it\x92s own right. In the old analog days, there might have been several individual hardware subsystems / black boxes, to do that, but since the advent of low cost reliable computing, more and more of that functionality has been delegated to software processes. Hardware function is abstracted into software space, a single black box replacing many. All those tasks that used separate hardware in the past, now run as individual software processes, at microsecond rate, sequentially. A sleight of hand making it appear as though there are separate computers, one for each item. Some critical tasks require microsecond response times, while others can wait seconds or longer. The way that is managed is by assigning a priority to each task, which ensures that all tasks have access to the processor as needed. Hence, the title, Real Time Systems. The task set shares processor, memory and other hardware, but there is great effort and process expended to encapsulate / isolate individual tasks, even though some of them will need to communicate with each other. Done right, that kind of system design can improve reliability due to far less hardware, and lowers cost and weight. However, it does concentrate far more design complexity into a much smaller abstract space, and needs a rigorous development process for safety critical applications.

Getting back to the point, if the TMCA function is resident on the FADEC, then it\x92s likely that it is just one software task of many running on a single set of FADEC hardware. Pretty opaque and no idea how we can begin to analyse that here. Iirc, tdracer said elsewhere that the various TMCA input qualifiers are handled by the airframe (?) , with a single yes / no input to the FADEC, but need to verify that. Really important to define what does what and where.

Last edited by syseng68k; 20th June 2025 at 13:35 . Reason: Spelling

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FADEC

syseng68k
June 20, 2025, 16:41:00 GMT
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Post: 11907124
If there is complete power loss, some or majority of the data streams would be lost, as their sources would power down.

Subjects: None

syseng68k
June 21, 2025, 16:15:00 GMT
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Post: 11907880
Aerospace101:

I think tdracer said upthread, that there are two rad alt sensors, and one wow, giving three. Need to verify, `but if two out of three are in agreement, that might be enough redundancy.

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syseng68k
June 22, 2025, 17:53:00 GMT
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Post: 11908716
Musician: CVR Data

I think you will find that the cvr data is digitised before reachng the recorder, so that could be starlink as well. Can see that happening in the future, but the main obstacle to that is the cost of bandwidth and data storage. Significant to include all a/c in the sky at any given time, though the data could be compressed into packets, sent in batches.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR

syseng68k
June 22, 2025, 18:02:00 GMT
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Post: 11908722
IgnorantAndroid: Dumbfounded

Definately not true for the people i've worked with, me included, where most of us can design the hardware, and write and debug the code to run on it. Might be true of very large projects, where the software at top level is little more than an application, with the hardware an abstraction.

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syseng68k
June 22, 2025, 18:28:00 GMT
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Post: 11908743
Musician: Illegal

Wasn't aware of that, thinking only about technical aspects. The possiblity of a data leak to a third party is always there, once a system is networked in some way.

Subjects: None

syseng68k
July 12, 2025, 23:05:00 GMT
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Post: 11920910
Human Factors Design

The first thing that occurred to me, after reading the report was, how human error (if that is the case), could be designed out of the system. Two such critical switches right under the engine controls almost looks like asking for trouble, if, for example, a brain fade activated those, instead of a gear up command. One way around that would be to have 2 factor authentication for safety critical functions, an are you sure ?. For example, two switches at the opposite ends of the panel, or similar.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Human Factors

syseng68k
July 13, 2025, 00:09:00 GMT
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Post: 11920952
Remi:

Poor analogy and different context. The point being that any function so critical to flight safety should require verification, on the assumption that people make mistakes, however unintentional.

Thinking time in a high stress situation. In the case of fuel shutoff, a few more seconds to verify should not be detrimental to safety.

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syseng68k
July 14, 2025, 13:20:00 GMT
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Post: 11922191
Musicion: .Articulate a reason -

The point being, that, for any safety critical system, the more data you have to analyse why something happened, the better, and the more it can contribute to improving the system or product overall.

Subjects: None

syseng68k
July 17, 2025, 11:38:00 GMT
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Post: 11924328
Press Report

Extract from a Telegraph article this morning, is this relevant ?.

Indian media, however, reported that investigators were examining potential electrical and digital faults that could have triggered “uncommanded” actions.

“The probe will ascertain the possibility of an ‘uncommanded transition’ of the fuel control switches to the cut-off mode seconds after the lift-off,” an official aware of the investigation was reported to have said.

Just hours before take-off, a pilot flying the same aircraft from Delhi to Ahmedabad noted in the technical log a “stabiliser position transducer defect”, the newspaper said.

The stabiliser position transducer is a sensor that controls the up and down movement of the aircraft’s nose, and transmits the data to flight control systems. The official said the malfunction was checked and the engineer did the troubleshooting.

“The malfunction is a critical issue as it can trigger incorrect responses in flight control, including unintended fuel cut-off signal,” the official was quoted as saying.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches

syseng68k
July 17, 2025, 16:35:00 GMT
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Post: 11924516
Musician:

The lack of technical rigour and curiosity in this thread is disappointing. Long diatribes about switches, as if they were the only thing in the chain that could have cut off the fuel. Rumours and News, fine, but would expect a higher level of hard analysis here, especially considering the limited information presented in the initial report.

It may indeed be that the tragedy was intentional, but there is no hard evidence to show that at this stage. While there are pointers suggesting that in the report, that is how if has been written, intentionally. Here, the crew are blameless until proven at fault, beyond reasonable doubt. Call that naive if you will, but science is about gathering and following the evidence, not jumping to conclusions.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All)  Fuel Cutoff Switches