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

theguardian.com

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

#431

Post by jenadine »

metalman wrote: post #66
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?

6 min, is empty, 6 min is purely theoretical, 6 min would not clear for ground handling or a test start, or a fuel system check,6 min would not do a go around. will interesting to see if they release info about what the real amount of fuel left is, and an authorative discussion on how much useable flight time was there. did they actualy make the taxi to the terminal?, or run out on the apron?

By your logic you need an infinite amount of fuel.

If you define X the amount of fuel you need after you land.

And you say that X needs to be enough to make an emergency landing.

And we define that the amount of fuel required for an emergency landing should cover the amount required for the landing operation while still having X in the tank when landed.

X > X + landing_cost

The plane already had made 3 failed attempt before and was redirected to two different airports.

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

#432

Post by jenadine »

paulddraper wrote: post #59
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?

At what point should they investigate? 0 minutes? -1 minutes?

They should investigate after the first failed landing, regardless of the amount of fuel in the tank.

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

#433

Post by MagicMoonlight »

jacquesm wrote: post #233
maccard wrote: post #204

Earlier quoted context omitted.

> this is cutting it way too fine. Either this is true, or this is why there’s a 45 minute reserve requirement. There were three failed landing attempts in two airports prior to the successful landing, and they spent almost as much time attempting to land as the scheduled flight took. Seems like this was exactly the scenario it was designed for?

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

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

#434

Post by burnt-resistor »

rappatic wrote: post #136

> 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.

Look at it (2.5 t/h) by volume (0.82 kg/L): 3 kL/h (790 gal/h) == 50 L/m (13 gal/m) == 830 mL/s (0.9 qt/s), and then divide the total flow rate by 2 for rate per engine.

Or divide the total by the number of passengers (~189) flying to consider effective fuel economy (per passenger) or 13 kg/pax/h or 3.6 g/pax/s.

They must plan to never land with less than 30 minutes of fuel, or about 1.25 t, and I'd say they should never, ever land with less than 15 minutes in their career during a pan/mayday bingo fuel emergency.

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

#435

Post by [deleted] »

TZubiri wrote: post #415
loverofhumanz wrote: post #79

Earlier quoted context omitted.

"I’m a little confused by what there is to investigate at all." You're confused why they should investigate how everyone on that flight came within minutes of dying? Something about the fuel reserves, procedures, or execution was clearly flawed.

I think the argument is that this is precisely the tail end of exceptional conditions overfueling is designed for. If it's typical to fill fuel for 4 hours on a 2 hour flight, and the flight took 4 hours. It seems like this is exactly why they overfuel to 4 hours. If this happens once every 100k flights, then it doesn't even beg the question of "why aren't we overfuelling to 4.5 hours". This is just clarifying the qu…

[deleted]

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

#436

Post by kqr »

howard941 wrote: post #347
anonymars wrote: post #294

Earlier quoted context omitted.

> often even need to brake to prevent the bike from speeding up too dangerously. Indeed, which is what the airplane would have done on its way down to land. So it's more like riding the brakes on your way down the hill, and now at the bottom when you realize you need to abort the landing, you are at low speed and it's quite an exercise to get back uphill to try again

The glider guys would always suggest a forward slip. It's a lot of fun to do. It's not taught often enough during primary training for powered airplanes.

Aren't low-speed slips something that makes planes flip upside-down when not used very carefully? (Inadvertent rudder changes corrected with opposite aileron resulting in a snap roll.)

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

#437

Post by alterom »

TZubiri wrote: post #414
mr_00ff00 wrote: post #409

Earlier quoted context omitted.

Why does it burn fuel so fast?

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 engine less efficient.

Think about it this way: if the jet airplane is tied to the ground, its engines are running at 0% efficiency, working hard to blow the air backwards. You wouldn't want to stand behind a jet engine when the plane is about to take off, when that's effectively the case.

The same applies to propeller-driven planes, of course. But those can vary the prop speed as well as propeller pitch, having more control on how fast the air is being pushed backwards. This allows the engine to be efficient at a wider ranger of speeds, particularly, at the slower range.

But the propeller has a limit of how fast it can push the air back. When the prop blades start reaching the speed of sound, weird shit starts happening [1]. So propeller-driven aircraft have a limit on speeds at which they can go efficiently.

Jet engines (turbofans when it comes to airliners) trade off low efficiency at low speed / low altitude (where the airplane is spending a small percentage of flight time) for higher efficiency at high speed / high altitude.

Variable pitch turbine fans[2] aim to address this tradeoff, but the tech has yet to catch on.

[1] https://en.wikipedia.org/wiki/Republic_XF-84H_Thunderscreech

[2] https://en.wikipedia.org/wiki/Variable_pitch_fan

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

#438

Post by amadeusw »

ant6n wrote: post #300
Aeolun wrote: post #270

Earlier quoted context omitted.

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.

The greenhouse effects of flying is about 3-5x the effect of just burning the fuel.

What do you mean by this? What else than burning the fuel contributes to the greenhouse effect?

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

#439

Post by kqr »

ktallett wrote: post #98
bluGill wrote: post #70

Earlier quoted context omitted.

Sure, but the flight was a lot longer than planed. How much extra do we need. They declared an emergency, and thus put themselves at the front of the line. They had 6 more minutes to do that touch and go around if that happened, and since they were already in a low fuel emergency they get priority and so there is enough time to do that if they needed. (edit - as others have noted, 6 minutes with high error bars, so t…

Surely the issue is more that they decided to make so many attempts to land local. There should be a max level of attempts.

There is a max level, and it is three.

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

#440

Post by kqr »

pornel wrote: post #359
rz2k wrote: post #304

Earlier quoted context omitted.

This reminds of discussions following the Fukushima disaster where one commenter claimed that it wasn't a design flaw, because it was an extraordinary circumstance. I found this appalling, because I do not at all think that was the risk profile that was sold to the public; I think people believed that it was supposed to be designed to safely survive 1000-year earthquakes and the tsunamis that they create. Likewise, I…

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.
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