Chernobyl
June 21, 2025, 23:56:00 GMT
permalink Post: 11908160

Quote:

Originally Posted by Lead Balloon

Perhaps my earlier post was incredible and that's what prompted the SLF's question.

Let us assume a simple, hypothetical WoW sensor arrangement: One sensor per main landing gear.

One of those sensors is indicating weight OFF wheels and the other is indicating weight ON wheels. What does the TCMA in each engine interpret that ostensibly contradictory sensor information to mean? (Note: For the time being, ignore the question whether the information is erroneous. It may be true.)

Are both engine TCMA's in the 'in the air' state, are both 'on the ground', or is one 'on the ground' and the other 'in the air'?

Given the purpose of the TCMA, I would have thought that any 'doubt' in this case would be resolved in favour of the 'on ground' state for both TCMAs.

But maybe it's the other way around. Maybe any 'doubt' would be resolved in favour of both TCMA's being in the 'in the air' state.

I have difficulty in envisaging any advantage in the TCMA system being designed such that one engine's TCMA is in the 'in the air' state and the engine's 'on the ground'.

Whichever the design and outcome, there will be benefits and there will be risks.

This was already addressed in one of tdracer's posts about the TCMA system: the air/ground decision is made by the aircraft itself (using multiple redundant inputs and voting logic), and only a single air/ground binary state is provided to the EEC(FADEC). Further, he also stated that the EEC assumes "air", as that is the safer state given the nature of its operations.

Based on this, both engines will get the same air/ground indication from the aircraft and hence will always make the same TCMA decisions (subject to their individual throttle positions and thrust outputs).

Last edited by Chernobyl; 21st June 2025 at 23:58 . Reason: Clarified the air/ground decision logic.

Subjects: None

Chernobyl
June 22, 2025, 14:48:00 GMT
permalink Post: 11908592

Quote:

Originally Posted by Lead Balloon

Thanks Chernobyl. I had understood trdracer's posts to be qualified on the basis of experience on types other than the 78, but I may be mistaken and, in any event, the 78 design may be exactly the same as those types.

I will suggest some amendments to your last sentence, though: Based on this, both engines ~~will~~ should get the same air/ground indication from the aircraft and hence ~~will~~ should always make the same TCMA decisions (subject to their individual throttle positions and thrust outputs).

Let's not lose sight of the fact that a 787 has had a TCMA 'commanded' double engine shut down, luckily only during the landing roll. That double shut down was not in circumstances of a rejected take-off where one or both engines delivered 'too much' thrust despite thrust levers being set to idle or 'low power'. Some might say incredible. But it's fact.

The best designed systems and software sometimes do strange, unexpected things even when everything is working 'properly', and even stranger things when some defect or damage occurs.

This is absolutely a fair comment (i.e., should vs will), given that we still don't know the cause of this accident. Since it appears that some highly unlikely combination of circumstances has nonetheless taken place, ruling anything out as "impossible" is unscientific at this time. Another poster above put it well: "as long as something doesn't violate the laws of physics, then it should be considered a possible cause" (I paraphrase).

Subjects: None

Chernobyl
June 29, 2025, 18:16:00 GMT
permalink Post: 11913160

Quote:

Originally Posted by MaybeItIs

There are safer batteries that are not lead-acid whales. Are the any other planes out there that need fireproof boxes and vent pipes to contain and purge burning battery fumes etc to the outside ?

[my emphasis]

To put this to rest as well - here is the Lithium battery thermal protection for what is arguably the most modern (non-Boeing) airliner out there: the Airbus A350 series.

Source: https://aircraft.airbus.com/sites/g/...irefighter.pdf

Subjects: None

Chernobyl
July 09, 2025, 22:25:00 GMT
permalink Post: 11918671

Quote:

Originally Posted by hans brinker

July 8 (Reuters) - A preliminary report into the deadly crash of an Air India jetliner in June is expected to be released by Friday, three sources with knowledge of the matter said, with one adding the probe had narrowed its focus to the movement of the plane's fuel control switches.

[emphasis added]

Quote:

Originally Posted by D Bru

Not necessarily TURIN If air India 171 was for some extraordinary reason confronted with both engines out on lift off, to switch off fuel levers and to re engage them would be the only way for a restart. For which there wasn’t altitude

D Bru : if that were actually the scenario, would they not instead be focusing on why "for some extraordinary reason [they were] confronted with both engines out on lift off", rather than having "narrowed its focus to the movement of the plane's fuel control switches", which would just be a side effect not a root cause?

But this is starting to devolve into a hamster wheel again.

Last edited by Chernobyl; 10th July 2025 at 04:32 .

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 Preliminary Report Relight

Chernobyl
July 13, 2025, 19:25:00 GMT
permalink Post: 11921561

Quote:

Originally Posted by AirScotia

No-one has discussed the concept of suicidal ideation, where a person may idly 'play' with ideas of how to end their life. If someone 'played' with the idea of how to end their life but make it look accidental, I think they might come up with a scenario such as this.

Ideation doesn't always result in an actual act, but if the thoughts came from life factors not being fully brought into consciousness, there may be a 'dream sequence' moment where they actually do the thing they've played with in their mind. It's not pre-planned or intentional, and the person who's acted out may not even be consciously aware they've done so.

I think what you're actually referring to are known as intrusive thoughts , not suicidal ideation. The former are generally normal and experienced even by the most sane and rational individuals. The key point in the cited reference is this: "In reality, a thought\x97even a very scary thought\x97is not an impulse." I'm not aware of any evidence that suggests that people act out intrusive thoughts -- even accidentally.

Subjects: None

Chernobyl
July 17, 2025, 17:27:00 GMT
permalink Post: 11924531

Quote:

Originally Posted by AirScotia

This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons.

Quote:

Originally Posted by Nick H.

I'm sorry to say that OhForSure's suicide theory fits well because:

[...] he may have wanted the investigators not to reach a firm conclusion of suicide so that his family would receive an insurance payout [...]

[emphasis mine]

I'm genuinely puzzled about the statements above (and many more similar examples in previous posts too numerous to count). I checked the language in my own policy (a common term life insurance policy in Canada) and it explicitly states under exclusions: "Suicide within 2 years of the effective date of coverage or reinstatement, or the date of any increase in coverage, is not covered." [again, emphasis mine] Beyond the 2 year exclusion period, suicide is considered an insured risk.

So, is everyone just presuming that insurance policies don't/won't pay out in the event of suicide? If so, I have at least one example that counters that common knowledge. Perhaps this is an exclusion in flight crew life insurance -- I don't rightly know (as simple SLF I'm not aware of those Ts & Cs). Can anyone point to an authoritative source (as opposed to just surmised knowledge) which states that a life insurance policy will not pay out in the event of suicide (past any exclusion period) and hence could be motivating factor in the decision-making of this incident? Further, it should be from an Indian life insurance company that would typically cover pilots (as this is the relevant scenario).

For further clarity: I take no position on whether this incident was triggered by intent or not. I just want to better understand whether this particular aspect may or may not have been a contributing factor.

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

Chernobyl June 21, 2025, 23:56:00 GMT permalink Post: 11908160	Quote: Originally Posted by Lead Balloon Perhaps my earlier post was incredible and that's what prompted the SLF's question. Let us assume a simple, hypothetical WoW sensor arrangement: One sensor per main landing gear. One of those sensors is indicating weight OFF wheels and the other is indicating weight ON wheels. What does the TCMA in each engine interpret that ostensibly contradictory sensor information to mean? (Note: For the time being, ignore the question whether the information is erroneous. It may be true.) Are both engine TCMA's in the 'in the air' state, are both 'on the ground', or is one 'on the ground' and the other 'in the air'? Given the purpose of the TCMA, I would have thought that any 'doubt' in this case would be resolved in favour of the 'on ground' state for both TCMAs. But maybe it's the other way around. Maybe any 'doubt' would be resolved in favour of both TCMA's being in the 'in the air' state. I have difficulty in envisaging any advantage in the TCMA system being designed such that one engine's TCMA is in the 'in the air' state and the engine's 'on the ground'. Whichever the design and outcome, there will be benefits and there will be risks. This was already addressed in one of tdracer's posts about the TCMA system: the air/ground decision is made by the aircraft itself (using multiple redundant inputs and voting logic), and only a single air/ground binary state is provided to the EEC(FADEC). Further, he also stated that the EEC assumes "air", as that is the safer state given the nature of its operations. Based on this, both engines will get the same air/ground indication from the aircraft and hence will always make the same TCMA decisions (subject to their individual throttle positions and thrust outputs). Last edited by Chernobyl; 21st June 2025 at 23:58 . Reason: Clarified the air/ground decision logic. Subjects: None
Chernobyl June 22, 2025, 14:48:00 GMT permalink Post: 11908592	Quote: Originally Posted by Lead Balloon Thanks Chernobyl. I had understood trdracer's posts to be qualified on the basis of experience on types other than the 78, but I may be mistaken and, in any event, the 78 design may be exactly the same as those types. I will suggest some amendments to your last sentence, though: Based on this, both engines ~~will~~ should get the same air/ground indication from the aircraft and hence ~~will~~ should always make the same TCMA decisions (subject to their individual throttle positions and thrust outputs). Let's not lose sight of the fact that a 787 has had a TCMA 'commanded' double engine shut down, luckily only during the landing roll. That double shut down was not in circumstances of a rejected take-off where one or both engines delivered 'too much' thrust despite thrust levers being set to idle or 'low power'. Some might say incredible. But it's fact. The best designed systems and software sometimes do strange, unexpected things even when everything is working 'properly', and even stranger things when some defect or damage occurs. This is absolutely a fair comment (i.e., should vs will), given that we still don't know the cause of this accident. Since it appears that some highly unlikely combination of circumstances has nonetheless taken place, ruling anything out as "impossible" is unscientific at this time. Another poster above put it well: "as long as something doesn't violate the laws of physics, then it should be considered a possible cause" (I paraphrase). Subjects: None
Chernobyl June 29, 2025, 18:16:00 GMT permalink Post: 11913160	Quote: Originally Posted by MaybeItIs There are safer batteries that are not lead-acid whales. Are the any other planes out there that need fireproof boxes and vent pipes to contain and purge burning battery fumes etc to the outside ? [my emphasis] To put this to rest as well - here is the Lithium battery thermal protection for what is arguably the most modern (non-Boeing) airliner out there: the Airbus A350 series. Source: https://aircraft.airbus.com/sites/g/...irefighter.pdf Subjects: None
Chernobyl July 09, 2025, 22:25:00 GMT permalink Post: 11918671	Quote: Originally Posted by hans brinker July 8 (Reuters) - A preliminary report into the deadly crash of an Air India jetliner in June is expected to be released by Friday, three sources with knowledge of the matter said, with one adding the probe had narrowed its focus to the movement of the plane's fuel control switches. [emphasis added] Quote: Originally Posted by D Bru Not necessarily TURIN If air India 171 was for some extraordinary reason confronted with both engines out on lift off, to switch off fuel levers and to re engage them would be the only way for a restart. For which there wasn’t altitude D Bru : if that were actually the scenario, would they not instead be focusing on why "for some extraordinary reason [they were] confronted with both engines out on lift off", rather than having "narrowed its focus to the movement of the plane's fuel control switches", which would just be a side effect not a root cause? But this is starting to devolve into a hamster wheel again. Last edited by Chernobyl; 10th July 2025 at 04:32 . 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 Preliminary Report Relight
Chernobyl July 13, 2025, 19:25:00 GMT permalink Post: 11921561	Quote: Originally Posted by AirScotia No-one has discussed the concept of suicidal ideation, where a person may idly 'play' with ideas of how to end their life. If someone 'played' with the idea of how to end their life but make it look accidental, I think they might come up with a scenario such as this. Ideation doesn't always result in an actual act, but if the thoughts came from life factors not being fully brought into consciousness, there may be a 'dream sequence' moment where they actually do the thing they've played with in their mind. It's not pre-planned or intentional, and the person who's acted out may not even be consciously aware they've done so. I think what you're actually referring to are known as intrusive thoughts , not suicidal ideation. The former are generally normal and experienced even by the most sane and rational individuals. The key point in the cited reference is this: "In reality, a thought\x97even a very scary thought\x97is not an impulse." I'm not aware of any evidence that suggests that people act out intrusive thoughts -- even accidentally. Subjects: None
Chernobyl July 17, 2025, 17:27:00 GMT permalink Post: 11924531	Quote: Originally Posted by AirScotia This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons. Quote: Originally Posted by Nick H. I'm sorry to say that OhForSure's suicide theory fits well because: [...] he may have wanted the investigators not to reach a firm conclusion of suicide so that his family would receive an insurance payout [...] [emphasis mine] I'm genuinely puzzled about the statements above (and many more similar examples in previous posts too numerous to count). I checked the language in my own policy (a common term life insurance policy in Canada) and it explicitly states under exclusions: "Suicide within 2 years of the effective date of coverage or reinstatement, or the date of any increase in coverage, is not covered." [again, emphasis mine] Beyond the 2 year exclusion period, suicide is considered an insured risk. So, is everyone just presuming that insurance policies don't/won't pay out in the event of suicide? If so, I have at least one example that counters that common knowledge. Perhaps this is an exclusion in flight crew life insurance -- I don't rightly know (as simple SLF I'm not aware of those Ts & Cs). Can anyone point to an authoritative source (as opposed to just surmised knowledge) which states that a life insurance policy will not pay out in the event of suicide (past any exclusion period) and hence could be motivating factor in the decision-making of this incident? Further, it should be from an Indian life insurance company that would typically cover pilots (as this is the relevant scenario). For further clarity: I take no position on whether this incident was triggered by intent or not. I just want to better understand whether this particular aspect may or may not have been a contributing factor. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR

Posts by user "Chernobyl" [Posts: 6 Total up-votes: 0 Pages: 1]