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True but I have a feeling it might be designed to rip off in this situation. I'm more surprised the wing rupture didn't cause a fire/explosion because this is

True but I have a feeling it might be designed to rip off in this situation. I'm more surprised the wing rupture didn't cause a fire/explosion because this is where most of the fuel is stored.

dotBen 2y ago
Planes typically land with little fuel left (obviously enough for emergencies etc but they are practically empty, it's safer and more efficient)
- nradov 2y ago
  That's not really accurate. Commercial airliners typically land with significant reserve fuel remaining on board. If a post crash fire ignites and isn't rapidly put out then that reserve fuel will be plenty to destroy the aircraft and kill everyone who doesn't evacuate quickly. https://simpleflying.com/minimum-fuel-requirements-definitions-guide/ https://simpleflying.com/minimum-fuel-requirements-definitio...
- cperciva 2y ago
  Less than a full load certainly, but I wouldn't say "little fuel". 30 minutes fuel remaining is an automatic mayday call.
- sitharus 2y ago
  In normal operation, an aeroplane lands with enough fuel for one go-around and re-attempt at landing at the chosen airport, plus enough for diversion to their alternate, plus an additional 30 minutes of flight. If an aircraft is anticipated to land with fuel for 30 minutes or less they must make a mayday call, and there's an incident report to fill in. Yes they want to land with as little fuel as possible, but regulations require them to carry more because we know what happens when you let airlines carry less.
stouset 2y ago
I seriously, seriously doubt it. The wings are so utterly critical to flight I can’t possibly imagine any situation they’d be engineered to snap off under. Further, that’s where the fuel is and any crash involving a wing rupture is dramatically more dangerous given the risk of fire. Hell even in a crash landing like this you want the plane to stay upright and stable.
- hinkley 2y ago
  Look up stress to failure tests on commercial airplanes. They know how much peak load is supposed to be for the airframe, then they go well beyond it to see how the plane fails. Generally you want the wings to break not the fuselage. You can in a lot of situations land a plane with 1.5 wings. But once the spine cracks you’re just a ballistic object.
  - WalterBright 2y ago
    The parts are designed for "ultimate load" which is 150% of the worst case maximum load expected to ever see in service. I used to work at Boeing on the 757 stabilizer trim system. There's the design group and the stress group. I was in the design group, the stress group double checks the design work. One day the stress group called me on the carpet, and asked me why my designs consistently just barely exceeded 150%. I said I started with the ultimate load, and worked backwards to size the part. The stress groups said they prefered designs to be 10% over the ultimate load. I replied that I designed to the requirements, as adding 10% makes the airplane overweight. If they didn't like the design requirements, change them. They grumbled, but I got my way :-/ A few months later, they offered me a position on the stress group. It was a nice compliment, as they normally required a masters' degree and I only had a bachelors. I told them I was honored by the offer, but my heart was in design. Some time later, my parts were put on the torture rack to see if they passed the ultimate load test. All of them passed on the first try. I also had the privilege in being mentored by some really fine engineers at Boeing, such as J Burton Berlin and Erwin Schweizer. Am I proud of that? Yes. I love flying in the 757. Best airplane Boeing ever made. Whenever I fly in them I chat a bit with the flight crew, and they love it, too.
WalterBright 2y ago
> it might be designed to rip off in this situation It isn't on any aircraft I've heard of. Only the engines have "fuses" which allow an engine to rip itself off without taking the wing with it. The wing root is the strongest part of the airplane (because that is where the maximum forces are).
- deleted 2y ago
  [deleted]
- rdtsc 2y ago
  There are other parts like that, like the gear struts that are designed to bend and snap instead instead of puncture through the wings, or the centering mechanism on turbofan shafts that's intentionally designed to break off if a blade breaks and cause an imbalance (I think that's what you meant by a "fuse", or did you mean something that rips the engine off altogether? I had never heard of that one).
  - WalterBright 2y ago
    The "fuse" that holds the engine on the strut is a bolt or a pin that is weaker than the surrounding structure, so it will break first and the engine will fall free. If the engine loses a fan blade, it will vibrate violently and it's probably better to lose the engine. I don't know about the other two things you mention. Maybe it's a newer feature than my time :-/
    - rdtsc 2y ago
      > If the engine loses a fan blade, it will vibrate violently and it's probably better to lose the engine. That's the idea with a fan blade loss, they didn't want to just drop an engine in that case so the centering mechanism on the turbine has an intentionally weaker part is designed to snap off to allow the spinning turbine to recenter itself as opposed to vibrating the whole structure off and causing more damage. The gear thing is to prevent puncturing the fuel tanks in the wings on a hard landing. It's preferable to snap off the gear, otherwise leaking fuel has a good chance of it immediately igniting.

True but I have a feeling it might be designed to rip off in this situation. I'm more surprised the wing rupture didn't cause a fire/explosion because this is where most of the fuel is stored.

dotBen 2y ago

Planes typically land with little fuel left (obviously enough for emergencies etc but they are practically empty, it's safer and more efficient)

nradov 2y ago
That's not really accurate. Commercial airliners typically land with significant reserve fuel remaining on board. If a post crash fire ignites and isn't rapidly put out then that reserve fuel will be plenty to destroy the aircraft and kill everyone who doesn't evacuate quickly. https://simpleflying.com/minimum-fuel-requirements-definitions-guide/ https://simpleflying.com/minimum-fuel-requirements-definitio...
cperciva 2y ago
Less than a full load certainly, but I wouldn't say "little fuel". 30 minutes fuel remaining is an automatic mayday call.
sitharus 2y ago
In normal operation, an aeroplane lands with enough fuel for one go-around and re-attempt at landing at the chosen airport, plus enough for diversion to their alternate, plus an additional 30 minutes of flight. If an aircraft is anticipated to land with fuel for 30 minutes or less they must make a mayday call, and there's an incident report to fill in. Yes they want to land with as little fuel as possible, but regulations require them to carry more because we know what happens when you let airlines carry less.

stouset 2y ago

I seriously, seriously doubt it. The wings are so utterly critical to flight I can’t possibly imagine any situation they’d be engineered to snap off under. Further, that’s where the fuel is and any crash involving a wing rupture is dramatically more dangerous given the risk of fire. Hell even in a crash landing like this you want the plane to stay upright and stable.

hinkley 2y ago
Look up stress to failure tests on commercial airplanes. They know how much peak load is supposed to be for the airframe, then they go well beyond it to see how the plane fails. Generally you want the wings to break not the fuselage. You can in a lot of situations land a plane with 1.5 wings. But once the spine cracks you’re just a ballistic object.
- WalterBright 2y ago
  The parts are designed for "ultimate load" which is 150% of the worst case maximum load expected to ever see in service. I used to work at Boeing on the 757 stabilizer trim system. There's the design group and the stress group. I was in the design group, the stress group double checks the design work. One day the stress group called me on the carpet, and asked me why my designs consistently just barely exceeded 150%. I said I started with the ultimate load, and worked backwards to size the part. The stress groups said they prefered designs to be 10% over the ultimate load. I replied that I designed to the requirements, as adding 10% makes the airplane overweight. If they didn't like the design requirements, change them. They grumbled, but I got my way :-/ A few months later, they offered me a position on the stress group. It was a nice compliment, as they normally required a masters' degree and I only had a bachelors. I told them I was honored by the offer, but my heart was in design. Some time later, my parts were put on the torture rack to see if they passed the ultimate load test. All of them passed on the first try. I also had the privilege in being mentored by some really fine engineers at Boeing, such as J Burton Berlin and Erwin Schweizer. Am I proud of that? Yes. I love flying in the 757. Best airplane Boeing ever made. Whenever I fly in them I chat a bit with the flight crew, and they love it, too.

WalterBright 2y ago

> it might be designed to rip off in this situation It isn't on any aircraft I've heard of. Only the engines have "fuses" which allow an engine to rip itself off without taking the wing with it. The wing root is the strongest part of the airplane (because that is where the maximum forces are).

deleted 2y ago
[deleted]
rdtsc 2y ago
There are other parts like that, like the gear struts that are designed to bend and snap instead instead of puncture through the wings, or the centering mechanism on turbofan shafts that's intentionally designed to break off if a blade breaks and cause an imbalance (I think that's what you meant by a "fuse", or did you mean something that rips the engine off altogether? I had never heard of that one).
- WalterBright 2y ago
  The "fuse" that holds the engine on the strut is a bolt or a pin that is weaker than the surrounding structure, so it will break first and the engine will fall free. If the engine loses a fan blade, it will vibrate violently and it's probably better to lose the engine. I don't know about the other two things you mention. Maybe it's a newer feature than my time :-/
  - rdtsc 2y ago
    > If the engine loses a fan blade, it will vibrate violently and it's probably better to lose the engine. That's the idea with a fan blade loss, they didn't want to just drop an engine in that case so the centering mechanism on the turbine has an intentionally weaker part is designed to snap off to allow the spinning turbine to recenter itself as opposed to vibrating the whole structure off and causing more damage. The gear thing is to prevent puncturing the fuel tanks in the wings on a hard landing. It's preferable to snap off the gear, otherwise leaking fuel has a good chance of it immediately igniting.