4 ms·

>The A380-F would be able to carry 60% more volume than the 747, but only 28% more weight That sounds really short-sited on airbus. How could they not see havi

by esaym 6y ago

>The A380-F would be able to carry 60% more volume than the 747, but only 28% more weight That sounds really short-sited on airbus. How could they not see having a plane double as a freighter would mean more sales?

TylerE 6y ago
Because it wouldn't mean more sales when it can only fly into a fraction of the worlds airports - the taxiways at most airports aren't strong or wide enough. Volume isn't generally the constraint on air freight, anyway.
bigiain 6y ago
It's inevitable physics. Things get heavier with the cube of the dimensions (a 2m cube is 8 times heavier than a 1m cube in the most simplistic example). Lift is a function of wing area, which only goes up with the square of the dimensions (a stupid "cubic wing" that's a 2m cube only has 4 times as much surface area as a 1m cubic "wing. Bigger planes can fly in spite of this because they're hollow. If you start filling them up with dense stuff, they get heavier way faster than they gain wing area (and hence lift capacity). That's why big birds are rare (or flightless, like emus), ands huge flying birds don't exist. And why there's a lot of conjecture that pterosaurs didn't fly very well, perhaps more like sugar gliders (which do extended/controlled jumps from high places) rather than taking of and soaring like eagles or albatrosses.
- Hypx 6y ago
  Modern research in Azhdarchids suggests that they could indeed fly. This is in spite of the fact that they largest of them would dwarf an ostrich.
  - bigiain 6y ago
    I'm not sure anyones suggesting they couldn't fly at all, just that some researchers propose what they were capable was closer to jumping off trees or hills and gliding to the ground, rather than launching from flat ground and flapping their way across continents. Though there's at least one guy who ran some calculations for Quetzalcoatl's probable aerodynamics and came up with numbers suggesting it could fly ~10,000 miles. Other people criticise that saying it only takes into account estimates of bone/wing structure and body weight, and ignores energy requirements which reptilian metabolic possibly cannot provide. I hope they're wrong. I desperately want to believe that there once existed 35 foot wingspan "dragons" which were capable of trans continental flight :-)
    - marvin 6y ago
      Soaring birds get most of their energy from currents of rising air, not flapping their wings. So it’s plausible it did a lot of soaring over land, assuming it could get in the air under its own power. Human-built gliders can fly thousands of kilometers in one go, admittedly uncomfortably and geographically constrained. But easily hundreds of kilometers on a day with good conditions, with a good degree of navigational freedom.
    - Someone 6y ago
      “energy requirements which reptilian metabolic possibly cannot provide” https://en.wikipedia.org/wiki/Pterosaur#Pycnofibers https://en.wikipedia.org/wiki/Pterosaur#Pycnofibers: “The presence of pycnofibers strongly indicates that pterosaurs were endothermic (warm-blooded)” (Warm-blooded reptiles sort of still exist. https://www.newscientist.com/article/2074982-first-warm-blooded-lizards-switch-on-mystery-heat-source-at-will/ https://www.newscientist.com/article/2074982-first-warm-bloo...: “The surprise came when the lizards reached the reproductive time of the year, from September to December. During the cold early hours of the morning in that season, their breathing and heart rates rose and their temperatures reached as much as 10 °C above those of their burrows”)
duxup 6y ago
Once a planes hits a certain big size it looks like the math means it's probably going to generally be a passenger plane / move low density stuff only and won't be able to really compete for freight.

by esaym 6y ago

TylerE 6y ago

Because it wouldn't mean more sales when it can only fly into a fraction of the worlds airports - the taxiways at most airports aren't strong or wide enough. Volume isn't generally the constraint on air freight, anyway.

bigiain 6y ago

It's inevitable physics. Things get heavier with the cube of the dimensions (a 2m cube is 8 times heavier than a 1m cube in the most simplistic example). Lift is a function of wing area, which only goes up with the square of the dimensions (a stupid "cubic wing" that's a 2m cube only has 4 times as much surface area as a 1m cubic "wing. Bigger planes can fly in spite of this because they're hollow. If you start filling them up with dense stuff, they get heavier way faster than they gain wing area (and hence lift capacity). That's why big birds are rare (or flightless, like emus), ands huge flying birds don't exist. And why there's a lot of conjecture that pterosaurs didn't fly very well, perhaps more like sugar gliders (which do extended/controlled jumps from high places) rather than taking of and soaring like eagles or albatrosses.

Hypx 6y ago
Modern research in Azhdarchids suggests that they could indeed fly. This is in spite of the fact that they largest of them would dwarf an ostrich.
- bigiain 6y ago
  I'm not sure anyones suggesting they couldn't fly at all, just that some researchers propose what they were capable was closer to jumping off trees or hills and gliding to the ground, rather than launching from flat ground and flapping their way across continents. Though there's at least one guy who ran some calculations for Quetzalcoatl's probable aerodynamics and came up with numbers suggesting it could fly ~10,000 miles. Other people criticise that saying it only takes into account estimates of bone/wing structure and body weight, and ignores energy requirements which reptilian metabolic possibly cannot provide. I hope they're wrong. I desperately want to believe that there once existed 35 foot wingspan "dragons" which were capable of trans continental flight :-)
  - marvin 6y ago
    Soaring birds get most of their energy from currents of rising air, not flapping their wings. So it’s plausible it did a lot of soaring over land, assuming it could get in the air under its own power. Human-built gliders can fly thousands of kilometers in one go, admittedly uncomfortably and geographically constrained. But easily hundreds of kilometers on a day with good conditions, with a good degree of navigational freedom.
  - Someone 6y ago
    “energy requirements which reptilian metabolic possibly cannot provide” https://en.wikipedia.org/wiki/Pterosaur#Pycnofibers https://en.wikipedia.org/wiki/Pterosaur#Pycnofibers: “The presence of pycnofibers strongly indicates that pterosaurs were endothermic (warm-blooded)” (Warm-blooded reptiles sort of still exist. https://www.newscientist.com/article/2074982-first-warm-blooded-lizards-switch-on-mystery-heat-source-at-will/ https://www.newscientist.com/article/2074982-first-warm-bloo...: “The surprise came when the lizards reached the reproductive time of the year, from September to December. During the cold early hours of the morning in that season, their breathing and heart rates rose and their temperatures reached as much as 10 °C above those of their burrows”)

duxup 6y ago

Once a planes hits a certain big size it looks like the math means it's probably going to generally be a passenger plane / move low density stuff only and won't be able to really compete for freight.