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Comment by moralestapia | Hacker News Reader

Context: because of bad weather.

But I'm truly surprised (in a bad way) people on the ground couldn't solve the situation earlier. The plane was in an emergency situation for hours, wtf.

Also, the airport density in the UK is high, they should have been diverted since before the first attempt, as it has happened to me and thousands of flights every single day around the world.

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The incident investigation will surely focus on exactly those things. But: just like shipping aviation is at the mercy of the weather and even though the rules (which are written in plenty of blood) try to anticipate all of the ways in which things go wrong there is a line beyond which you are at risk. I've had one triple go-around in my life and it soured me on flying for a long time afterwards because I have written software to compute the amount of fuel required for a flight and I know how thin the margins are once you fail that third time. I am not going to get ahead of the investigation and speculate but I can think of at least five ways in which this could have happened, and I'm mostly curious about whether the root cause is one of those five or something completely different. Note that until there is weight on the wheels you don't actually know how much fuel remains in the tanks, there always is some uncertainty, to the pilots it may well have looked as if the tanks were already empty while they were still flying the plane. Those people must have been extremely stressed out on that final attempt to land.

There must be measurements of the fuel tanks state, right?

There are but this is not as precise as you might think due to a lot of confounding factors. Even the best flow meters are only about 0.2% accurate, and I find that seriously impressive.

Armchair quarterbacking it, but it was human error. They should have diverted sooner and been more aware of the weather.

Edit: there might also be part of Ryanair culture that contributed, but that's speculation.

That's one conclusion. But don't rule out a lot of other things that may have been a factor, for instance, they may have had a batch of bad fuel, they may have had less fuel to start with than they thought they had (this happens, it shouldn't but it does happen), the fuel indicators may have been off (you only know for sure after touch down), there may have been a leak, an engine may have been burning more than it should have. There are probably many others that I can't think of of the top off my head but there are a lot of reasons why the margins are as large as they are.

Those are all possibilities, but

https://www.flightaware.com/live/flight/RYR3418/history/2025...

They had at least an extra hour of fuel, and they landed at the third airport they tried.

Yes, that's how it should be. Something went badly wrong here. The big question is what.

I read and agree with all those options being possible. Except the "they may have had a batch of bad fuel". How would that work in your thinking? I can imagine a bad batch of fuel leading to engine damage or flameout and many other things, but it is hard for me to imagine how a bad batch would lead to not enough fuel remaining in the tank.

If you have more water in the fuel than you think you do (there always is some due to condensation in the tanks) then you might be able to reach your destination but you'll be burning more 'fuel' than your original estimate would have you believe because there is less power per unit weight of (contaminated) fuel.

This is fairly common in GA and there are cases where it has happened in scheduled flights as well. That's why fuel sampling is common practice.

Interesting. That makes sense. Thank you for the explanation!

It's supposed to be an extremely low amount and the fuel pick-ups are placed such that it should never be a problem but there have been cases where water in the fuel caused problems, including at least one notorious crash where the cause was identified to be fuel contamination.

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