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Whatif the 747-200F got a rear loading ramp ?

Archibald

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As said in the thread title. How hard would it be, technically ? On paper at least, it is possible to dig a hole into the 747 rear end: see the AAC concepts, also the cruise missiles platform...

The 747-200F flew on November 30, 1971. Over the next three decades Boeing, again and again, proposed military 747s - against the KC-10, C-5B, and C-17. And they failed.

Whatif circa 1970 Boeing put a rear loading ramp on the 747-200F - just to put some pressure on Lockheed and their much maligned C-5A ?

Whatif the (baffled by the C-5A issues) US military backed the idea through PanAm and the CRAF - https://en.wikipedia.org/wiki/Civil_Reserve_Air_Fleet ?
 

Hobbes

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Going by this drawing, the main cabin floor is about 4.5 meters above the ground. That would make the ramp very long (a 20% gradient results in a 20 m long ramp), very steep or a combination thereof. Kneeling undercarriage could mitigate this a bit.


This is why military airlifters have a high wing and trapezoidal cross-sections: both enable the main deck to be much closer to the ground.
 

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riggerrob

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747-100 was designed as a freighter, but a nose-loading freighter. That is why the cockpit is above the main passenger deck and it has a bulged fairing behind the cockpit. Initially, Boeing designated the small upper deck as a crew rest area, but marketeers got one look and sold it as an expensive, upper-class bar/lounge for first-class passengers.
Boeing later extended the upper deck to increase seating to up to 500 for short-haul flights connecting the Japanese Islands.
Nose or side-loading freighters have much lighter empty/un-loaded weights, but require dedicated ground support equipment to load cargo.

The British Hawker-Siddeley Andover was the only low-winged military transport with a tail ramp. Its main landing gear "knelt" to ease loading over the main wing spar.
I wonder how much a tail ramp adds to the empty weight of a transport?
Tail ramps also create significant drag problems. The faster the airplane the longer the "tail cone" needed to reduce drag.
 

Archibald

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Ah dang. Better to have Boeing kicking Lockheed rear end over CX-HLS in 1966 and in the first place. Although that instantly kills the 747 of course.

I wonder how much a tail ramp adds to the empty weight of a transport?
That would make the ramp very long (a 20% gradient results in a 20 m long ramp)
I would hazard: a lot of weight (for a 20 m long ramp !)
 
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