4 ms·

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...

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...