5 ms·

Ok, given its flying just the core, and not the fan, why doesn't it fit in the cargo hold? I mean they wouldn't have to worry about the extra drag/etc in the ho

Ok, given its flying just the core, and not the fan, why doesn't it fit in the cargo hold? I mean they wouldn't have to worry about the extra drag/etc in the hold. It also seems odd that they would do this on a plane carrying commercial passengers since it seems more of an "experimental" modification even if the manufacture has approved it.

bragr 4y ago
It's a design feature dating back to when there were no easy ways to transport the engines. It's a perfectly cromulent way to transport a 747 engine, just uncommon these days because there are many large air freighters now (like the 747 itself). The idea was that in the early days of the 747, airlines could be self sufficient in transporting engines and their new expensive planes wouldn't get stranded.
- dotancohen 4y ago
  It should be noted in context that original the 747 could, like the 737 before it, service airfields too small to have service centers. Therefore, it was important that another 747 could ferry in all parts needed to service a potentially damaged 747 at these locations, including an entire engine. Most aircraft with such capability are identified by the inclusion of built-in stairs for passenger ingress/egress, which the 747-100 had.
  - bragr 4y ago
    The 737-200 had an optional gravel kit for unpaved runways! A few -200s still in use because of that feature
    - rkagerer 4y ago
      Neat - kind of like mid flaps for planes. Also thank you for teaching me a new word, "cromulent".
      - delsarto 4y ago
        I am dating myself but I'm old enough to have watched the Simpsons episode where this word was invented in its first airing. Maybe it is a word now, I mean it's no more or less ridiculous than other words, which somebody just made up at some point too. https://www.merriam-webster.com/words-at-play/what-does-cromulent-mean https://www.merriam-webster.com/words-at-play/what-does-crom...
        dotancohen 4y ago
        You're embiggening my perception of you.
sreevisakh 4y ago
It isn't experimental or unique even if it's rare. It has been done before. I'm not sure why this instance alone got such attention. Regarding the cargo hold problem, the aircraft wasn't carrying just the engine core. The 'pod' is most likely the engine nacelle itself. I wonder if the entire thing would fit through the cargo door (mere speculation). While it's true that the 747 was originally meant as a cargo carrier, most of it was meant to be loaded through the nose of the aircraft. The nose could be opened for this purpose and the cockpit was above the cargo area to accommodate this.
- Sakos 4y ago
  It got so much attention because it's rare. We like to read about things that seem novel and interesting. I wasn't aware the 747 had this capability until reading this article today.
- hef19898 4y ago
  Normaly the nose loading is done oy when absolutely necessary. It's a pain, takes ages and is complicated. When possible stuff is squeezed through the fuselage cargo doors. Back the day we did it with a ten foot sea container, never thought it would fit...
  - sreevisakh 4y ago
    I agree about the nose loading part. Meanwhile, how does an engine with its nacelle compare to a marine container in terms of dimensions? Would it be easier or harder to load through the fuselage doors? I also assume that they will need a fixture or container for the engine if it was to be loaded into the cargo hold.
    - jsjohnst 4y ago
      Engine is roughly 2.25m in diameter and 5.5m in length. So it would fit through the nose cone door, even with a modest fixture/container, with room to spare.
  - jsjohnst 4y ago
Gordonjcp 4y ago
It's rare to see a car pulling a trailer, but it's not experimental. The "fifth pod" thing was designed in from the start.
- StillBored 4y ago
  The trailer thing is sorta exactly why I'm uncomfortable with it. I have a truck which a few times a year I tow various trailers/etc with. Yes the truck was "designed" for this, but that doesn't mean its not eating in safety margins in many ways and is fundamentally far more dangerous for a laundry list of reasons over simply driving the truck around. The asymmetry of something that large is going to create a lot of complications that this article is glossing over with "trimming", starting with weight/balance issues (which presumably end up being a case that the opposing wing tanks need to be unbalanced/over full, and managed by the crew, etc), and unusual airframe/control surface stresses that eat into the engineering margins. So, it wouldn't be noteworthy except for the fact that they were also flying 350+ passengers at the same time. Many airline accidents are cases of confounding variables strung together. You can be assured that had anything unusual happened on that fight, that the NTSB report would have started with "The airplane was flying massively out of trim"
hollerith 4y ago
Well it is carrying the core and the nacelle. The nacelle is the bulkiest part.
jsjohnst 4y ago
The issue is the dimensions of the cargo doors. A 747 engine is approximately 2.25m in diameter and 5.5m long. Of the 4-5 different sized doors on a 747, there’s only two that it would fit through: - Front nose cone door - Main deck cargo door I believe neither would be used on a passenger airline configured 747 (could be wrong though!) and hence why the wing based fifth pod configuration was likely used.
- inferiorhuman 4y ago
  Wikipedia puts the CF6 from a 747-400 at 4.27m long, 2.69m diameter. An RB-211 looks to be a little narrower and longer. Cargolux puts the biggest rectangle that can fit through the main cargo door at 3.05m x 3.10m. So yeah you could probably fit an engine in a nacelle and fixture through the main deck door on a freighter. However your big limitation will be height at either 2.44m or 3.00m depending on where on the main deck you're checking. The lower deck (which is all you'd have available on a passenger 747) has a much lower height limit (an LD-1 has a height limit of 1.62 m). An engine's just not going to fit inside unless you're talking about something designed for oversize cargo like the Dreamlifter (747) or Beluga (A300) or Beluga XL (A330). Oversized cargo is also the main use case for the An-124/225. https://www.cargolux.com/fleet-equipment/aircraft/747-400f-specifications/ https://www.cargolux.com/fleet-equipment/aircraft/747-400f-s...
  - jsjohnst 4y ago
    > An engine's just not going to fit inside unless you're talking about something designed for oversize cargo like the Dreamlifter (747) This is in direct conflict with literally the paragraph you posted before it. You could definitely carry the RB-211 on a standard cargo version of the 747, as you yourself stated previously. It could only fit on the main deck, but the standard 747 cargo (aka not needing the guppy) definitely could do it.
    - inferiorhuman 4y ago
      Yeah there's about 0.7 m more height than a CF6. That seems like potentially not enough room for a proper fixture. In any case it's not going to fit inside a passenger 747.
deleted 4y ago
[deleted]

bragr 4y ago

It's a design feature dating back to when there were no easy ways to transport the engines. It's a perfectly cromulent way to transport a 747 engine, just uncommon these days because there are many large air freighters now (like the 747 itself). The idea was that in the early days of the 747, airlines could be self sufficient in transporting engines and their new expensive planes wouldn't get stranded.

dotancohen 4y ago
It should be noted in context that original the 747 could, like the 737 before it, service airfields too small to have service centers. Therefore, it was important that another 747 could ferry in all parts needed to service a potentially damaged 747 at these locations, including an entire engine. Most aircraft with such capability are identified by the inclusion of built-in stairs for passenger ingress/egress, which the 747-100 had.
- bragr 4y ago
  The 737-200 had an optional gravel kit for unpaved runways! A few -200s still in use because of that feature
  - rkagerer 4y ago
    Neat - kind of like mid flaps for planes. Also thank you for teaching me a new word, "cromulent".
    - delsarto 4y ago
      I am dating myself but I'm old enough to have watched the Simpsons episode where this word was invented in its first airing. Maybe it is a word now, I mean it's no more or less ridiculous than other words, which somebody just made up at some point too. https://www.merriam-webster.com/words-at-play/what-does-cromulent-mean https://www.merriam-webster.com/words-at-play/what-does-crom...
      - dotancohen 4y ago
        You're embiggening my perception of you.

sreevisakh 4y ago

It isn't experimental or unique even if it's rare. It has been done before. I'm not sure why this instance alone got such attention. Regarding the cargo hold problem, the aircraft wasn't carrying just the engine core. The 'pod' is most likely the engine nacelle itself. I wonder if the entire thing would fit through the cargo door (mere speculation). While it's true that the 747 was originally meant as a cargo carrier, most of it was meant to be loaded through the nose of the aircraft. The nose could be opened for this purpose and the cockpit was above the cargo area to accommodate this.

Sakos 4y ago
It got so much attention because it's rare. We like to read about things that seem novel and interesting. I wasn't aware the 747 had this capability until reading this article today.
hef19898 4y ago
Normaly the nose loading is done oy when absolutely necessary. It's a pain, takes ages and is complicated. When possible stuff is squeezed through the fuselage cargo doors. Back the day we did it with a ten foot sea container, never thought it would fit...
- sreevisakh 4y ago
  I agree about the nose loading part. Meanwhile, how does an engine with its nacelle compare to a marine container in terms of dimensions? Would it be easier or harder to load through the fuselage doors? I also assume that they will need a fixture or container for the engine if it was to be loaded into the cargo hold.
  - jsjohnst 4y ago
    Engine is roughly 2.25m in diameter and 5.5m in length. So it would fit through the nose cone door, even with a modest fixture/container, with room to spare.
- jsjohnst 4y ago

Gordonjcp 4y ago

It's rare to see a car pulling a trailer, but it's not experimental. The "fifth pod" thing was designed in from the start.

StillBored 4y ago
The trailer thing is sorta exactly why I'm uncomfortable with it. I have a truck which a few times a year I tow various trailers/etc with. Yes the truck was "designed" for this, but that doesn't mean its not eating in safety margins in many ways and is fundamentally far more dangerous for a laundry list of reasons over simply driving the truck around. The asymmetry of something that large is going to create a lot of complications that this article is glossing over with "trimming", starting with weight/balance issues (which presumably end up being a case that the opposing wing tanks need to be unbalanced/over full, and managed by the crew, etc), and unusual airframe/control surface stresses that eat into the engineering margins. So, it wouldn't be noteworthy except for the fact that they were also flying 350+ passengers at the same time. Many airline accidents are cases of confounding variables strung together. You can be assured that had anything unusual happened on that fight, that the NTSB report would have started with "The airplane was flying massively out of trim"

hollerith 4y ago

Well it is carrying the core and the nacelle. The nacelle is the bulkiest part.

jsjohnst 4y ago

The issue is the dimensions of the cargo doors. A 747 engine is approximately 2.25m in diameter and 5.5m long. Of the 4-5 different sized doors on a 747, there’s only two that it would fit through: - Front nose cone door - Main deck cargo door I believe neither would be used on a passenger airline configured 747 (could be wrong though!) and hence why the wing based fifth pod configuration was likely used.

inferiorhuman 4y ago
Wikipedia puts the CF6 from a 747-400 at 4.27m long, 2.69m diameter. An RB-211 looks to be a little narrower and longer. Cargolux puts the biggest rectangle that can fit through the main cargo door at 3.05m x 3.10m. So yeah you could probably fit an engine in a nacelle and fixture through the main deck door on a freighter. However your big limitation will be height at either 2.44m or 3.00m depending on where on the main deck you're checking. The lower deck (which is all you'd have available on a passenger 747) has a much lower height limit (an LD-1 has a height limit of 1.62 m). An engine's just not going to fit inside unless you're talking about something designed for oversize cargo like the Dreamlifter (747) or Beluga (A300) or Beluga XL (A330). Oversized cargo is also the main use case for the An-124/225. https://www.cargolux.com/fleet-equipment/aircraft/747-400f-specifications/ https://www.cargolux.com/fleet-equipment/aircraft/747-400f-s...
- jsjohnst 4y ago
  > An engine's just not going to fit inside unless you're talking about something designed for oversize cargo like the Dreamlifter (747) This is in direct conflict with literally the paragraph you posted before it. You could definitely carry the RB-211 on a standard cargo version of the 747, as you yourself stated previously. It could only fit on the main deck, but the standard 747 cargo (aka not needing the guppy) definitely could do it.
  - inferiorhuman 4y ago
    Yeah there's about 0.7 m more height than a CF6. That seems like potentially not enough room for a proper fixture. In any case it's not going to fit inside a passenger 747.

deleted 4y ago

[deleted]