The headline is about the landing, but the issue here happened at takeoff. There were 100 mph winds at the destination and this was their 4th fallback attempt and their third airport. This flight should never have taken off, the risk of multiple diversions was easily predictable, but the flight took off headed toward an airport in dangerous conditions, got diverted to a second airport that was just as dangerous, then finally to a third where conditions were so bad other flights were being cancelled (https://uk.news.yahoo.com/storm-amy-brings-flight-chaos-2019...) and where it finally landed because it was either land at that airport or land somewhere that is not at all an airport. Once this flight was in the air, disaster was more or less inevitable and we lucked into a narrow eviting window.
Ryanair flight landed at Manchester airport with six minutes of fuel left
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Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#262That is very exceptional. I've written fuel estimation software for airliners (cargo, fortunately), and the number of rules regarding go-arounds, alternates and holding time resulted in there usually being quite a bit of fuel in the tanks on landing, by design. I've never heard of '6 minutes left' in practice where it wasn't a massive issue and the investigation into how this could have happened will make for interes…
Yeah, again, I’m going to wait for the Mentour Pilot analysis on this one.
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#263Earlier 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?
I'm not an aviation expert, but generally in safety engineering, safety buffers are not simply calculated as [normal situation] * [safety factor], but [worst case scenario] * [safety factor] If you ever cut into your safety allowance, you've already fucked up. Your expected design criteria should account for all use cases, nominal or worst-case. The safety factor is there for safety, it is never intended to be used.
Yes, exactly. The day it's normal to eat into the allowance is the day we start seeing planes falling out of sky for lack of fuel again. The only way to prevent that is to treat 30 min of fuel as seriously as you would 0 minutes.
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#264That is very exceptional. I've written fuel estimation software for airliners (cargo, fortunately), and the number of rules regarding go-arounds, alternates and holding time resulted in there usually being quite a bit of fuel in the tanks on landing, by design. I've never heard of '6 minutes left' in practice where it wasn't a massive issue and the investigation into how this could have happened will make for interes…
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?
Imagine you're standing on a balcony and discover that the supports are cracked almost all the way through.
Do you shrug and say, that's why they have a safety factor, everything worked as intended? Or do you say, holy crap, I nearly died, how did this happen?
The purpose of the safety factor is to save you if things go badly wrong. The fact that it did its job doesn't mean things didn't go badly wrong. If you don't address what happened then you no longer have a safety factor.
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#265Earlier 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?
I'm not an aviation expert, but generally in safety engineering, safety buffers are not simply calculated as [normal situation] * [safety factor], but [worst case scenario] * [safety factor] If you ever cut into your safety allowance, you've already fucked up. Your expected design criteria should account for all use cases, nominal or worst-case. The safety factor is there for safety, it is never intended to be used.
This is really helpful and I think I understand now.
The approach is basically “accounting for everything that might go wrong to the best of our experience, including problems arising from the complex interactions between the airplane and supporting ground systems and processes, this is how much fuel you need in the worst case scenario. And now lets add more to give us a cushion, and we will treat consumption of this last reserve as tantamount to a crash.”
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#266Earlier quoted context omitted.
(1) The turbofan category of jet engine seems to inspire a lot of very pretty animated technical diagrams—here’s one set from a German manufacturer [0]. Now if only we could convince Bartozs Ciechanowski to take on such a subject… [1] (2) I know glider pilots who fly without any fuel at all, once aloft… sounds not unlike the 150-200km glide range that @MaxikCZ mentions at idle from cruising altitude. [0] https://aero…
Aircraft that are designed as gliders are much lighter and thus have much longer glide range than aircraft that aren't. They're so lightweight that they can climb on thermals. A 737 is not going to be able to do that, but a regular glider can't fly at 400 knots.
> thus have much longer glide range
Im gonna be a little pedantic, but the weight has surprisingly small effect on glide range, actually none of the weight affect the range directly, its all from secondary effects.
The glide is given mainly by drag and lift (so body and wing geometry), correlated to certain speed. The weight isnt in the equation at all. What weight does, is increases the speed in which the aircraft achieves this maximum glide ratio, and in higher speed you have higher drag, which finally reduces the range.
Thats why many modern gliders have water tanks in wings, to increase the weight of the glider, moving planes speed of best glide ratio higher, allowing for more efficiency at higher speeds. Its worth it if the atmospheric condition provide strong lifts. Pilot can then dump the water in flight to reduce the wing load, allowing them to land with less speed, or just keep in the air longer as thermals get weaker in the afternoon/evening
(source, I used to be a glider pilot)
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#267That is very exceptional. I've written fuel estimation software for airliners (cargo, fortunately), and the number of rules regarding go-arounds, alternates and holding time resulted in there usually being quite a bit of fuel in the tanks on landing, by design. I've never heard of '6 minutes left' in practice where it wasn't a massive issue and the investigation into how this could have happened will make for interes…
Very insightful, thanks. Glad everything was ok.
All I had to contribute was to ask if they were trying to hypermile or something?
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#268Between overworked, understaffed ATC and undertrained pilots, I'm expecting some major disasters in the coming years.
One of the problems with modern internet discourse is there is an implicit assumption that the problem of one country is automatically the problem of another country.
I think that's just Americans tbh.
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#269Earlier quoted context omitted.
I have known former air traffic controllers that won't fly certain airlines because of a notorious habit some have for queue jumping by claiming they're low on fuel. If they are low on fuel is something else, but in any case when the ATCs have noticed a pattern then something is up. This situation sounds a lot less nefarious, but it does also sound like they should have rerouted earlier.
"claiming they're low on fuel" It is almost fascinating how humans will stoop to dishonesty even in banal situations - and not just any humans, but pilots, who should be subject to at least some vetting. Maybe planes should be retrofitted as to transmit their actual fuel state including a qualified assessment in minutes to the ATC. Not just because of the cheaters, but also to warn the ATC in the rare case that some…
>If I designed such a system from scratch, "remaining fuel" would be part of my telemetry.
Careful what you wish for. I'd rather people skip the queue by pretending to be low on fuel than people skip the queue by actually being low on fuel.
Re: Ryanair flight landed at Manchester airport with six minutes of fuel left
#270> the Boeing 737-800 had just 220kg of fuel left in its tanks... enough for just five or six minutes of flying Maybe I'm just unaware, but it's crazy to me that these planes burn 40 kilograms of jet fuel per minute.
I don’t think that’s so much? A car burns 1 liter to travel 15 kilometer’ish, and carries 4 people.
An airplane burns 40 liters to travel 15 kilometers too (900 kph), but carries 160 people.
That’s about 40x more than the car, so the fuel economy per passenger is about the same.
Of course jet fuel is probably a bit more polluting, but it’s still interesting how close it is.