Ryanair flight landed at Manchester airport with six minutes of fuel left • Hacker News Board

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#441

Post by minetest2048 » Sat, Oct 11, 2025, 5:56 AM UTC

alterom wrote: post #437

TZubiri wrote: post #414

Earlier quoted context omitted.

My guess is higher air density means more wind resistance, which acts as negative forward acceleration.

Not just that. Jet engines are efficient at higher speeds because the exhaust of the jet engine is fast . If the plane is going fast as well, that exhaust is more or less stationary relative to the ground. The engine works to exchange the position of the plane with the position of the air in front of it. If the plane is going slow, it's accelerating the air backwards . That's where the work is going, making the engin…

That sounds like Oberth effect in rocketry, where the faster you go the more efficient your rocket be: https://en.wikipedia.org/wiki/Oberth_effect

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#442

Post by in_cahoots » Sat, Oct 11, 2025, 5:58 AM UTC

jacquesm wrote: post #140

psunavy03 wrote: post #73

Earlier quoted context omitted.

The point is that the unions are there to allow the pilots to advocate for all kinds of safety-of-flight related things like fuel reserves, crew rest, and so forth that management would be happy to cut to save money. And to do so without fear of retaliation. And if you don't think the airlines would love to lobby Congress about the regulatory backstop, well . . .

As I wrote elsewhere in this thread I actually wrote software to estimate the amount of fuel a jet should load to comply with the rules. This was commissioned by the airline and they were scared shitless that they would ever be found to be in breach of the regulations on this aspect. It is one of those red lines that you really do not wish to cross. There are other aspects of flight where you are right but this parti…

As an aviation fan just reading this thread is quite eye-opening in terms of how much risk tolerance the average commenter has vs what is standard in the aviation community and on aviation forums. It's almost like peeking into two different worlds. I wonder if there would be any value in teaching an "engineering when lives are on the line" or "war stories from accident investigations" classes to new engineers. I feel like there's value in appreciating just how much more work goes into building a system where people's lives are at stake.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#443

Post by jacquesm » Sat, Oct 11, 2025, 6:09 AM UTC

MagicMoonlight wrote: post #433

jacquesm wrote: post #233

Earlier quoted context omitted.

No, this is what should never happen. I wrote fuel estimation software for cargo 747's and the one thing I would have never ever wanted to read is that an airliner of the company I worked for had landed with too little fuel.

Right but this is an emergency… they didn’t plan to run out of fuel

Clearly, that's why it makes the news.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#444

Post by vasco » Sat, Oct 11, 2025, 6:11 AM UTC

alterom wrote: post #437

TZubiri wrote: post #414

Earlier quoted context omitted.

My guess is higher air density means more wind resistance, which acts as negative forward acceleration.

Not just that. Jet engines are efficient at higher speeds because the exhaust of the jet engine is fast . If the plane is going fast as well, that exhaust is more or less stationary relative to the ground. The engine works to exchange the position of the plane with the position of the air in front of it. If the plane is going slow, it's accelerating the air backwards . That's where the work is going, making the engin…

I think about it like this:

Jet needs to suck air from front. If air is stopped, sucking is hard. If air is already being thrown at you, you don't even need to suck, just let it come in.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#445

Post by whycome » Sat, Oct 11, 2025, 6:12 AM UTC

scrumper wrote: post #253

whycome wrote: post #217

Earlier quoted context omitted.

I think you missed the point. Presenting information in different ways is useful (and the method of display can offer informational insights itself). And for different users it might help parse larger connections. And by using the LLM to summarize just that one facet of the problem (itinerary and sequence) and sharing it here, they’ve contributed in a meaningful way. It may not have warranted a response. But it added…

Okay that's fair. I had no issue with the contribution itself, the route summary is helpful. > And they did well enough by citing that the info came from an LLM. In terms of acknowledging AI contribution, you're damned if you do, damned if you don't. Here it's sidetracked a discussion; but transparency is better than otherwise I suppose. Perhaps it just boils down to taste - and I don't like it. Anyway, you made me t…

You also made me think. I think the problem lies in the nature of “threaded” discussions. The information was useful, but it wasn’t necessarily a “reply” to any particular comment. But, the design here leaves no other choice when adding it. It maybe doesn’t make sense as a top-level comment either. It’s almost like we need to have…side comments? Asides? Like a place to just drop in relevant tidbits and informational helpers rather than a true “comment”. Maybe it’s as simple as having a means to turn off replies to signify that a contribution was an “relevant aside”.

But yes, in a perfectly meta way, I think we’ve both thought more about the nature and design of web comments and information and the implications of LLM-assisted chat ‘augmentation’. (All those AI summaries forced upon us in every site is probably the worse implementation of this!)

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#446

Post by jacquesm » Sat, Oct 11, 2025, 6:12 AM UTC

cpncrunch wrote: post #362

nostrademons wrote: post #128

Earlier quoted context omitted.

With 100mph winds I could easily see the 30 min reserve being eaten up by the flight from Edinburgh to Manchester. It's 178 miles! It takes a good 15-20 minutes to cross that distance when flying normally, add ascent & descent time and the landing pattern and you're easily at 24 minutes. Edit: in other comments here, it seems like Edinburgh to Manchester is a 45 minute flight. So yeah, they could easily have been out…

Yeah, although it depends what the alternate was in the flight plan. It may have been Manchester. Although I think its more likely it was Edinburgh, which in the circumstances was too optimistic. Too much concern about the minimal costs of fuel tankering to add a bit more gas? Or saving time by not refuelling? Ive never flown on Ryanair and dont intend to.

The flight plans I've seen accounted for two alternates, not one, a significant time in a holding pattern and up to three go-arounds. This was for cargo 747s and a while ago so chances are the regulations have changed by now, also, it may have been due to the kind of cargo.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#447

Post by jacquesm » Sat, Oct 11, 2025, 6:15 AM UTC

henryfjordan wrote: post #293

appreciatorBus wrote: post #290

Earlier quoted context omitted.

Depends if our goal is to have zero aircraft crashes. If the goal is zero, then for any given parameter, you have to define a margin of safety well before crash territory and treat breaching that margin as seriously as if there had been a crash. Similarly planes are kept 5 nautical miles apart horizontally, and if they get closer than that, you guessed it - investigation. Ofc planes could come within inches and every…

We shouldn't aim for 0 crashes due to low fuel though. How many deaths does carrying around 3x fuel than what you reasonably need contribute to via extra pollution? We should aim for 1 every 10-100 years or something reasonable like that.

At 3x the number of deaths would be 0 because there would be no more flights.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#448

Post by jacquesm » Sat, Oct 11, 2025, 6:17 AM UTC

kqr wrote: post #440

pornel wrote: post #359

Earlier quoted context omitted.

It's also a communication problem, because labels like "100-year/1000-year event" are easily misunderstood. * they're derived from an estimated probability of the event (independently) happening each year. It doesn't mean that it won't happen for n years. The probability is the same every year. * the probabilities are estimates, trying to predict extreme outliers. Usually from less than 100s of years of data, using s…

I find a useful exercise is to have a cheat sheet of historic flood heights in some area, tell someone the first record high, ask them how high they would make the levee and how long they think it would last. Peoples' sense for extremal events is bad.

That's a great exercise. Where I live a lot of people died because in the past we were not able to make that guess correctly. A lot was learned, at great expense.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#449

Post by jacquesm » Sat, Oct 11, 2025, 6:19 AM UTC

nucleardog wrote: post #424

abtinf wrote: post #40

Earlier quoted context omitted.

Naively as an outsider, this situation seems like everything worked as intended? On a nominally 2h45m flight, they spent an extra 2 hours in the air, presumably doing doing fuel intensive altitude changing maneuvers, and were eventually able to land safely with their reserves almost exhausted. I’m a little confused by what there is to investigate at all. How much fuel should they have landed with?

Thirty minutes. If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call. Mayday is a term enshrined in law. It is only to be used when people will die if you do not receive help. In the US, calling it inappropriately can be punished with up to 10 years in jail and a $250k fine. It's protected in this way bec…

What is fascinating about this whole discussion is that the general world of software development is so far away from actual engineering that all of these basics require painstaking explanation.

Re: Ryanair flight landed at Manchester airport with six minutes of fuel left

#450

Post by jacquesm » Sat, Oct 11, 2025, 6:20 AM UTC

jenadine wrote: post #428

nucleardog wrote: post #424

Earlier quoted context omitted.

Thirty minutes. If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call. Mayday is a term enshrined in law. It is only to be used when people will die if you do not receive help. In the US, calling it inappropriately can be punished with up to 10 years in jail and a $250k fine. It's protected in this way bec…

> If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call. From the article, they did issue a mayday call, when the closest airport was presumably Edinburgh. Then they flew to Manchester and landed.

There must have been a very good reason to do that.