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Suitability for conversion to freighter service was actually one of the original design goals for the 747! But back then, the assumption was that passenger airl

Suitability for conversion to freighter service was actually one of the original design goals for the 747! But back then, the assumption was that passenger airlines would be transitioning not to twinjets but to supersonic planes.

Steve44 8y ago
I saw a programme about this a little while ago. That's why the cockpit and crew area is high, it allows a larger flat load area.
- dingaling 8y ago
  When Boeing stretched the upper deck for the -300 and subsequent passenger models there was resistance from the freight operators because the floor beams intruded into the main-deck volume. Not so much as to affect passengers but enough to restrict positioning of cargo. So all built-as-freighter models retain the short-deck with short hump, right up until the latest 747-8F being built today. Even though, counter intuitively, the long hump has less drag. That's also why retired long-hump passenger versions are less valued for conversion to freighters. There is no approved type mod to hack off the long hump and its structure.
  - howard941 8y ago
    > the long hump has less drag. Does that translate into less lift?
    - djrogers 8y ago
      No, planes are not designed with a significant amount of lift from their bodies (excepting lifting-body aircraft like the B2). The primary goal for the body design is to reduce drag, and let the wings produce the lift.
    - FabHK 8y ago
      I assume the fuselage drag is mostly parasitic (=wasted) drag, not induced (=lift-generating) drag.
  - Steve44 8y ago
    > Even though, counter intuitively, the long hump has less drag. Not directly related but readers may be interested in the Area Rule. This is more aimed at trans and super sonic flight so I don't think that applicable to the 747. Basically the whole area cross sections down the length of the plane needs to be smooth so when it's punching a hole in the air the compression ( volume displacement ) around it is even and this reduces drag. The generally do this by narrowing the fuselage at the places the wings and external engines are. The Blackburn Buccaneer is a good example. https://modelingmadness.com/review/viet/gb/cjabuc2b.jpg https://modelingmadness.com/review/viet/gb/cjabuc2b.jpg This looks like a decent starting point, http://www.aerospaceweb.org/question/aerodynamics/q0104.shtml http://www.aerospaceweb.org/question/aerodynamics/q0104.shtm...
compton_effect 8y ago
Also airlines are moving from the hub and spoke model to the point to point model. So the need for 747's and especially A380's for passenger service has gone way down. Plus both those planes just aren't as efficient as twinjets. In fact, it was partly the high fuel consumption of the early 747's that eventually led to Pan-Am's bankruptcy.
- deleted 8y ago
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pintxo 8y ago
If I read it correctly, the original design was for an AF cargo plane, actually. As the AF dropped the Boeing proposal, airlines asked for a larger plane, and Boeing converted the freight design into a passenger plane. So no wonder, you could so easily convert it into a cargo plane.
- gsnedders 8y ago
  AFAIK, relatively little was shared between the proposed Boeing transport and the 747. Certainly there are influences: the cockpit and the nose door are the biggest ones. I think little else was carried over, given very different mission profiles. (The winner of that competition was the C-5 Galaxy.)

Steve44 8y ago

I saw a programme about this a little while ago. That's why the cockpit and crew area is high, it allows a larger flat load area.

dingaling 8y ago
When Boeing stretched the upper deck for the -300 and subsequent passenger models there was resistance from the freight operators because the floor beams intruded into the main-deck volume. Not so much as to affect passengers but enough to restrict positioning of cargo. So all built-as-freighter models retain the short-deck with short hump, right up until the latest 747-8F being built today. Even though, counter intuitively, the long hump has less drag. That's also why retired long-hump passenger versions are less valued for conversion to freighters. There is no approved type mod to hack off the long hump and its structure.
- howard941 8y ago
  > the long hump has less drag. Does that translate into less lift?
  - djrogers 8y ago
    No, planes are not designed with a significant amount of lift from their bodies (excepting lifting-body aircraft like the B2). The primary goal for the body design is to reduce drag, and let the wings produce the lift.
  - FabHK 8y ago
    I assume the fuselage drag is mostly parasitic (=wasted) drag, not induced (=lift-generating) drag.
- Steve44 8y ago
  > Even though, counter intuitively, the long hump has less drag. Not directly related but readers may be interested in the Area Rule. This is more aimed at trans and super sonic flight so I don't think that applicable to the 747. Basically the whole area cross sections down the length of the plane needs to be smooth so when it's punching a hole in the air the compression ( volume displacement ) around it is even and this reduces drag. The generally do this by narrowing the fuselage at the places the wings and external engines are. The Blackburn Buccaneer is a good example. https://modelingmadness.com/review/viet/gb/cjabuc2b.jpg https://modelingmadness.com/review/viet/gb/cjabuc2b.jpg This looks like a decent starting point, http://www.aerospaceweb.org/question/aerodynamics/q0104.shtml http://www.aerospaceweb.org/question/aerodynamics/q0104.shtm...

compton_effect 8y ago

Also airlines are moving from the hub and spoke model to the point to point model. So the need for 747's and especially A380's for passenger service has gone way down. Plus both those planes just aren't as efficient as twinjets. In fact, it was partly the high fuel consumption of the early 747's that eventually led to Pan-Am's bankruptcy.

deleted 8y ago
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pintxo 8y ago

If I read it correctly, the original design was for an AF cargo plane, actually. As the AF dropped the Boeing proposal, airlines asked for a larger plane, and Boeing converted the freight design into a passenger plane. So no wonder, you could so easily convert it into a cargo plane.

gsnedders 8y ago
AFAIK, relatively little was shared between the proposed Boeing transport and the 747. Certainly there are influences: the cockpit and the nose door are the biggest ones. I think little else was carried over, given very different mission profiles. (The winner of that competition was the C-5 Galaxy.)