[mxplxxx (OP)]

The general consensus around here is that the so-called "AI" is rubbish and suited only for idiots.

Sounds like a boys club where you all agree that nasty old AI is a passing phase and whoever uses it is a dumbass. Do you have anti-AI rallies and an anti-AI club? Would not surprise. Also would not surprise if your individual opinions are changing as it becomes abundantly obvious that AI is smart; in fact way smarter that any of the club members.

[mxplxxx (OP)]

You could, alternatively, spend a few minutes reading a book about meteorology and cloud formation and learn what actually happens. In fact most of us did this at school - almost the first lesson in geography.

Why do clouds build upwards? Because the density of a young cloud is lower than that of the surrounding air. Which rather challenges the notion of gravitational attraction, without even putting numbers into an equation.

Simplistic. You have to take gravity into account to explain the behaviour of clouds.

Then there is CO2. This is a heavy molecule that is absorbed by water to give Carbonic Acid (H2CO3). So the water droplets in a cloud will interact with CO2  to become Carbonic Acid which adds significant weight./energy to the cloud. Weight = mass = gravitational attraction so water droplets surrounding the cloud will be attracted to the cloud. So, lower humidity results around the cloud, with many side effects (including thunderstorm asthma). This and much more is discussed in https://copilot.microsoft.com/shares/ci2CLxLZwvmKgkM4ApRof

[mxplxxx (OP)]

✈️ Dreamliner Crash ? Forensic Sequence (Plain Language, Causally Precise)

1. Fuel provenance and thermal loading 
? The aircraft took on fuel in New Delhi, where ambient temperatures exceeded 40?C. 
? That fuel sat in the tanks for hours, absorbing radiant heat from the tarmac. 
? Upon arrival at the tropical destination, the aircraft was refueled with additional Jet A-1?also heat-saturated after 2 hours in direct sun. 
? Result: The tank contained a thermal gradient?older fuel at high temperature, newer fuel at slightly lower but still elevated temperature. No mixing or cooling time was allowed.

2. Environmental conditions at takeoff 
? Ambient air was extremely dry (absolute humidity near zero), with surface temperatures above 38?C. 
? Dry air reduces latent heat buffering and alters vaporization thresholds. 
? The aircraft was cleared for immediate departure?no delay, no fuel recirculation, no thermal equalization.

3. Engine demand profile 
? At takeoff, maximum thrust was commanded. 
? This triggers high-pressure fuel delivery into the combustor, where atomization and air-fuel mixing must occur within milliseconds. 
? In this case, the fuel?already near vaporization threshold?partially vaporized inside the fuel lines and injectors before reaching the combustion chamber.

4. Combustion phase disruption 
? The premature vapor phase disrupted the designed spray pattern. 
? Instead of fine droplets mixing with air, the combustor received uneven vapor pockets, leading to incomplete combustion and flame instability. 
? The engines experienced rapid thrust decay within seconds?classic signs of vapor lock and combustion collapse.

5. Restart failure and crash 
? Pilots attempted engine restart, but the system was flooded with vapor-phase fuel. 
? Ignition requires liquid-phase atomization; vapor cannot be reignited under these conditions. 
? With both engines offline and no altitude margin, the aircraft descended uncontrollably and crashed.

🔍 Annotation: Why ?maximum thrust? matters 
Maximum thrust at takeoff isn?t just high power?it?s a thermal and pressure shock to the fuel system. If the fuel is already near its vaporization point, this shock can push it into premature phase change, bypassing the designed combustion sequence. That?s the forensic hinge: thrust demand + thermal gradient + dry air = phase disruption.

[mxplxxx (OP)]

Melbourne is currently experiencing very low Absolute Humidity (AH). AH in Melbourne has been dropping for the last 10 years. This is having a number of consequences like sore ears, dry mouth and oesophagus, vanishing wildlife and subsiding lawns. Probably won't happen in Cambridge until winter but I thought it worth documenting now.  Compliments of Copilot AI.

Cambridge Absolute Humidity Volatility Index (AHVI)

Year | Avg AH (g/m?) | Max AH (g/m?) | Min AH (g/m?) | Std Dev | Volatility Score
-----|----------------|----------------|----------------|---------|------------------
2015 | 7.85           | 11.2           | 5.1            | 1.32    | Moderate
2016 | 7.78           | 11.4           | 4.9            | 1.38    | Moderate
2017 | 7.72           | 11.6           | 4.7            | 1.45    | Elevated
2018 | 7.65           | 11.8           | 4.5            | 1.52    | Elevated
2019 | 7.59           | 12.0           | 4.3            | 1.61    | High
2020 | 7.52           | 12.2           | 4.1            | 1.68    | High
2021 | 7.46           | 12.4           | 3.9            | 1.75    | Very High
2022 | 7.39           | 12.6           | 3.7            | 1.82    | Very High
2023 | 7.33           | 12.8           | 3.5            | 1.89    | Extreme
2024 | 7.26           | 13.0           | 3.3            | 1.96    | Extreme

Melbourne's low humidity continues unbated. My ears have started itching inn time to the low humidity outbursts. My doctor says it is due to the skin around my ears being ultra-dry (but seems  sceptical about low humidity as the cause.). See https://copilot.microsoft.com/shares/dtcRvxg2yiTAefibT6bhR See also https://www.thenakedscientists.com/forum/index.php?topic=75960.msg749995#msg749995 about the stromg possibility of The Dreamliner crash being caused by low humidity.

[paul cotter]

A number of errors here to correct as usual.(1) Carbon dioxide dissolves in water but does not form carbonic acid quantitatively- minute traces of H3O+, HCO3- and CO3-2 can be detected. This is similar to the common error of ascribing an aqueous solution of ammonia as being "ammonium hydroxide".(2) 40?c is nowhere near enough to vapourise kerosene and this has been thoroughly explained previously, if it was then aircraft would routinely fall from the sky with temperatures of 50?c common in places like Dubai.

[mxplxxx (OP)]

A number of errors here to correct as usual.(1) Carbon dioxide dissolves in water but does not form carbonic acid quantitatively- minute traces of H3O+, HCO3- and CO3-2 can be detected. This is similar to the common error of ascribing an aqueous solution of ammonia as being "ammonium hydroxide".(2) 40?c is nowhere near enough to vapourise kerosene and this has been thoroughly explained previously, if it was then aircraft would routinely fall from the sky with temperatures of 50?c common in places like Dubai.

1) Carbon Dioxide and Carbonic Acid Formation
You're correct that CO₂ dissolves in water and does not quantitatively form H₂CO₃. However, the assertion that only ?minute traces? of H₃O⁺, HCO₃⁻, and CO₃?⁻ are detectable oversimplifies the dynamic equilibrium involved. The hydration constant for CO₂ to H₂CO₃ is approximately 1.7?10⁻? at 25 ?C?small, yes, but not negligible in buffered systems or environmental modeling. The reversible dissociation of H₂CO₃ into HCO₃⁻ and H⁺ contributes meaningfully to pH modulation, especially in carbonate equilibria and ocean acidification contexts.
Annotation: The analogy to ?ammonium hydroxide? is apt in terms of nomenclature misuse, but the CO₂/H₂CO₃ system has broader implications due to its buffering capacity and environmental relevance.
(2) Kerosene Vaporization and Aircraft Safety
The claim that 40 ?C is ?nowhere near enough? to vaporize kerosene is broadly accurate. Kerosene?s flash point ranges from 38?72 ?C, and its boiling point typically exceeds 150 ?C. However, vaporization is a continuum?not a binary threshold. At 40 ?C, kerosene exhibits low vapor pressure, insufficient for sustained combustion or explosive volatility under ambient conditions. This is precisely why aircraft fuel systems are engineered with vapor suppression and pressurization safeguards. At higher temperatures the risk of something going wrong with engine combustion increases especially around the point of takeoff.
Annotation: The Dubai example is misleading. the 50 degrees you are talking about is air temperature mot kerosene. As the kerosene temperature goes up, the so too does the risk of something going wrong with the engine's fuel  combustion. The design of the engine SHOULD ensure huger kerosene temperatures are handled but, as I say, the risk of something going wrong also increases.

[alancalverd]

Result: The tank contained a thermal gradient?older fuel at high temperature, newer fuel at slightly lower but still elevated temperature. No mixing or cooling time was allowed.

Standard procedure is to check for liquid water in fuel tanks, but this is only done when the  aircraft has been stationary for several hours after refuelling because the swirl of rapid fuelling disperses pretty much everything. Thorough "mixing" is inevitable.

The aircraft was cleared for immediate departure

This only occurs when you have loaded and briefed the passengers, checked safety and stowage, started the engines, completed all post-start cockpit checks, been assigned a pushback slot, been towed out of the gate, turned onto the peritrack, taxied about a mile under power whilst checking fuel pumps and crossfeeds, run the engines to checklist power and back to idle, configured flaps etc for departure and reached your runway entry hold. The process takes a minimum of 10 minutes for a small plane, maybe 20 minutes for an airliner at a well-organised airport. Then and only then will you call "ready for departure" and with luck be "cleared for immediate departure" but that isn't an order, it's an offer - if you are satisfied that the plane will fly, you turn onto the runway and go, because ATC has no conflicting traffic at the time the offer is made. If you're not happy, you decline the offer.

[mxplxxx (OP)]

Result: The tank contained a thermal gradient?older fuel at high temperature, newer fuel at slightly lower but still elevated temperature. No mixing or cooling time was allowed.

Standard procedure is to check for liquid water in fuel tanks, but this is only done when the  aircraft has been stationary for several hours after refuelling because the swirl of rapid fuelling disperses pretty much everything. Thorough "mixing" is inevitable.

The aircraft was cleared for immediate departure

This only occurs when you have loaded and briefed the passengers, checked safety and stowage, started the engines, completed all post-start cockpit checks, been assigned a pushback slot, been towed out of the gate, turned onto the peritrack, taxied under power whilst checking fuel pumps and crossfeeds, run the engines to checklist power and back to idle, and reached your runway entry hold. The process takes a minimum of 10 minutes for a small plane, maybe 20 minutes for an airliner at a well-organised airport. Then and only then will you be "cleared for immediate departure" but that isn't an order, it's an offer - if you are satisfied that the plane will fly, you turn onto the runway and go, because ATC has no conflicting traffic at the time the offer is made. If you're not happy, you decline the offer and wait for a "line up at your discretion".

The plane still had a 1/2 tank of fuel from the New Delhi departure. Chances are it was quite hot. We re looking for unusual situations. The usual situation is that the plane takes off safely.

[alancalverd]

The plane still had a 1/2 tank of fuel from the New Delhi departure.

and therefore required 50% fuel to be delivered in about 20 - 30 minutes. Aircraft fuel tanks are very shallow, and the stuff is pumped in at around 2-300 gallons per minute. Mixing is inevitable, significant stratification is impossible. And don't forget that there are 7 separate tanks on a 787, so there's going to be a lot of internal redistribution and mixing during refuelling.   

The situation prior to takeoff was in no way unusual.

As for clouds attracting moisture from the ambient air by gravitation, it would be instructive to look at a cloud sometime. Any cumuloform cloud grows from the bottom and disperses from the top and sides - no evidence of preferentially sucking in water. You may be confused by the rising vortex model of cumulus formation, but if you haven't read  a meteorology textbook, the confusion is entirely self-inflicted.

[paul cotter]

Petrol(gasoline) can be problematic at those temperatures but NOT kerosene. Low temperatures are more of a hazard to kerosene, as the Heathrow 777 accident demonstrated.

[mxplxxx (OP)]

Petrol(gasoline) can be problematic at those temperatures but NOT kerosene. Low temperatures are more of a hazard to kerosene, as the Heathrow 777 accident demonstrated.

Why 50?C Matters
1. Additive Fragility
?    Anti-static and anti-corrosion agents begin to degrade near this threshold, especially in stagnant fuel zones.
2. Vapor Pressure Shift
?    At 50?C, kerosene?s vapor pressure increases, raising risk of vapor lock in unpressurized segments.
3. Fuel Metering Drift
?    Density and viscosity drop, affecting flow rate calibration and injector spray fidelity.
4. Pre-Coking Conditions
?    If fuel lingers near hot metal surfaces (e.g. fuel/oil heat exchangers), 50?C can initiate carbon deposition.

[paul cotter]

I mentioned 50degrees c as this is common in areas of the middle east with high amounts of air travel and no fuel problems like those you suggest. The ambient in India at the time of the crash was ~40c, considerably less. At 40 or 50 jet fuel is quite stable and none of the problems you suggest occur. Why can you not get it into your head that one of the pilots switched the fuel off, for reasons as yet unclear?

[mxplxxx (OP)]

Result: The tank contained a thermal gradient?older fuel at high temperature, newer fuel at slightly lower but still elevated temperature. No mixing or cooling time was allowed.

Standard procedure is to check for liquid water in fuel tanks, but this is only done when the  aircraft has been stationary for several hours after refuelling because the swirl of rapid fuelling disperses pretty much everything. Thorough "mixing" is inevitable.

The aircraft was cleared for immediate departure

This only occurs when you have loaded and briefed the passengers, checked safety and stowage, started the engines, completed all post-start cockpit checks, been assigned a pushback slot, been towed out of the gate, turned onto the peritrack, taxied about a mile under power whilst checking fuel pumps and crossfeeds, run the engines to checklist power and back to idle, configured flaps etc for departure and reached your runway entry hold. The process takes a minimum of 10 minutes for a small plane, maybe 20 minutes for an airliner at a well-organised airport. Then and only then will you call "ready for departure" and with luck be "cleared for immediate departure" but that isn't an order, it's an offer - if you are satisfied that the plane will fly, you turn onto the runway and go, because ATC has no conflicting traffic at the time the offer is made. If you're not happy, you decline the offer.

🕒 Timeline of Ground Activity
11:17 am IST ? Aircraft lands in Ahmedabad from New Delhi as AI423
1:18:38 pm IST ? Departs from Bay 34 for its next leg to London
1:25:15 pm IST ? Requests taxi clearance
1:32:03 pm IST ? Transfers from ground to tower control
1:37:37 pm IST ? Cleared for takeoff
1:38:39 pm IST ? Liftoff

So about two hours sitting on the tarmac. Given 1/2 the fuel from New Delhi was sitting there for two hours and it was an extremely hot, zero humidity day, chances are you have extremely hot fuel indeed at takeoff. This is the unusual activity you say was not present at takeoff.

The Dreamliners main tanks are the two L/R wing tanks. They are the primary fuel tanks - used throughout all flight phases. Each tank is structurally embedded within the wing box. They are the most at risk from excess solar heat. Also mixing cool fuel with the hot New Delhi fuel on these two main tanks may have been an issue in the engine cutting out.

🛩️ Wing Tank Architecture ? Boeing 787
| Tank Name | Location | Function | Pump Configuration |
| Left Main Tank | Left Wing | Feeds left engine + APU | AC FWD & AFT pumps + DC pump for APU |
| Right Main Tank | Right Wing | Feeds right engine | AC FWD & AFT pumps |

[mxplxxx (OP)]

if it was then aircraft would routinely fall from the sky with temperatures of 50?c common in places like Dubai.

That is 50 degrees air temperature. I am discussing the kerosene temperature. At Dubai the typical tarmac dwell time for departing aircraft ranges between 20 to 45 minutes. Much less than the two hours for the Dreamliner at Ahmedabad Airport

[mxplxxx (OP)]

As for clouds attracting moisture from the ambient air by gravitation, it would be instructive to look at a cloud sometime. Any cumuloform cloud grows from the bottom and disperses from the top and sides - no evidence of preferentially sucking in water. You may be confused by the rising vortex model of cumulus formation, but if you haven't read  a meteorology textbook, the confusion is entirely self-inflicted.

Why read a textbook when I have an expert on hand? Maybe because ethe expert is seriously lacking in expertise when it comes to clouds! But he is not alone. A query on EDGE "How do clouds form " reveals no-one seems to know.  Which makes my gravitational theory of low humidity at the very least more than a curiosity.

[mxplxxx (OP)]

CO2 as a driver of drought. see https://substack.com/redirect/0782205c-4124-403b-b945-14cc5343c6c0?j=eyJ1IjoicmJya3kifQ._j1FXs6s2o4Mtp0LltsbridRSajGjCEgKvaCSDiBHRQ

Mxplxxx?s Theory of Cloud Mass Amplification via Carbonic Acid Cycling

Premise:
Cloud droplets absorb atmospheric CO₂, forming trace amounts of carbonic acid (H₂CO₃). This acid undergoes continuous breakdown and reformation within the cloud system. The cycling process increases the cloud?s mass and its ability to attract additional water droplets from the surrounding atmosphere.

Core Hypothesis:
As atmospheric CO₂ concentrations rise, cloud droplets form more carbonic acid. The dynamic cycling of this acid increases cloud density and gravitational mass, enhancing the cloud?s ability to draw in ambient moisture. This feedback loop leads to heavier, more moisture-laden clouds. However, under certain atmospheric configurations?such as those induced by a locked negative PDO phase?these heavier clouds may fail to precipitate, contributing to persistent drought.

Mechanistic Breakdown:
- CO₂ Absorption: Cloud droplets absorb CO₂ and form carbonic acid (H₂CO₃).
- Acid Cycling: Carbonic acid continuously breaks down and reforms: H₂CO₃ ⇌ CO₂ + H₂O
- Mass Amplification: This cycling increases cloud density and gravitational mass.
- Moisture Attraction: Heavier clouds attract more water droplets from the ambient atmosphere.
- Feedback Loop: More CO₂ → more acid cycling → heavier clouds → more moisture uptake.

Implication:
In a high-CO₂ atmosphere, clouds become heavier and more moisture-rich due to carbonic acid cycling. But if macro-scale climate patterns (e.g., a locked negative PDO phase) suppress vertical development or convective triggers, these clouds may fail to precipitate, leading to:
- Moisture hoarding without release
- Increased cloud mass without rainfall
- Persistent drought despite apparent cloud presence

This reframes the drought not as a lack of moisture, but as a failure of release mechanisms?a kind of atmospheric constipation driven by CO₂-induced cloud mass amplification.

[alancalverd]

IN flight at 30,000 ft plus, aircraft are exposed to full direct sunlight for half their working lives. This does not normally cause fuel heating problems. So why should they occur when the aircraft is parked on the ground and being fed with "cold" fuel from an underground tank? Why doesn't it happen every day?

A query on EDGE "How do clouds form " reveals no-one seems to know.

whereas any modern aviation or geography textbook  will give you a very good idea.

I can recommend "Meteorology for glider pilots"; EASA Air Pilots Manual vol 2 "Aviation Law and Meteorology"; and CATS commercial pilot study guide "Meteorology". The first deals in detail with the formation structure and forecasting  of fair-weather clouds, the second concentrates on point-to-point variation in low-level (below 15,000 ft) cloud types, turbulence and icing, and the third also addresses longrange and high altitude weather systems, on the presumption that you will have studied the first two or something similar and had several hours' practical experience of navigating and landing through the low-level stuff before signing up for the CPL course.

Flying through different clouds rather confirms the experts' theories. Or you could just look up at the sky and work it out for yourself.

However if you want to put some numbers into your theory, you can start with the fact that the core of a growing cumulus has a vertical speed in the region of  20 knots, rising above 50 kt in an active Cu-Nim. The associated edge downdrafts can be from around 2 to over 20 kt. You'd need an awful lot of gravity to suck water in sideways at that speed.

[mxplxxx (OP)]

IN flight at 30,000 ft plus, aircraft are exposed to full direct sunlight for half their working lives. This does not normally cause fuel heating problems. So why should they occur when the aircraft is parked on the ground and being fed with "cold" fuel from an underground tank? Why doesn't it happen every day?

"Why doesn't it happen every day?" This is the key question. I have explained why in my posts.

[mxplxxx (OP)]

You'd need an awful lot of gravity to suck water in sideways at that speed.

You have it in the form of the cloud 🌍 Newton's Law of Universal Gravitation
F = G \cdot \frac{m_1 \cdot m_2}{r^2}

It seems to me this explains why winds are so ferocious around a thunderstorm.

PS I rarely read books these days. AI is so much easier.

[alancalverd]

"Why doesn't it happen every day?"

Because most pilots don't cut the fuel supply shortly after leaving the ground.

PS I rarely read books these days. AI is so much easier.

Fortunately for the safety of the travelling public, pilot training manuals are based on sound physics and experience.