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

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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 ?
 
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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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.
 
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 !)
 
106266-2d8225837ac1d2c5e77daf76c8b4fe88.jpg


I wish I could get more picture of that beast; notably the "missile opening" at the bottom. If that thing can be funded to launch missiles, then a rear-ramp variant would be more acceptable.
 
If you are talking about large fixed bases only, a ramp at the base might be doable which would remove the need for extra weight in the aircraft.
 
You mean, a ground based vehicle a bit similar to the one used when loading through the nose door ?
 
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 ?
Boeing's C-17 design (which gets referred to as the C-16 even though it was never assigned that designation) proposal was essentially an enlarged and three engined C-14. But their KC-33A entry into the ATCA (Advanced Tanker/Cargo Aircraft) competition that the KC-10 won included an ATOCA variant, where the O stood for "oversized". It would involve raising the flight deck to create a constant width and height cargo compartment and adding a kneeling nose gear.

Cargo capacities: KC-10 77 tonnes, Boeing ATCA: 110 tonnes, ATOCA: 105 tonnes, but between the kneeling nose gear and constant width/height compartment ATOCA could carry MBTs. Which means it could do most of the the C-5 mission (a bit slower since there was no rear ramp) and the tanker mission.

The KC-10 could operate from more airfields, which seems to be why it won, and has a lift capacity similar to the C-17 which can carry MBTs, but the KC-10 fuselage can't fit heavy armor. Which makes me think an ATOCA KC-33 may have been a missed opportunity.

Constant width and height and a kneeling nose gear would also make it easier to load and unload for the commercial market, so a 747-200F(O) might be a goer as well as an asset for CRAF. Maybe a subsidy to buy the aircraft in order to get it in production for CRAF.

American secret projects 3, airlifters since 1962 has the details.
 
You mean, a ground based vehicle a bit similar to the one used when loading through the nose door ?

Something like, I cannot find where but there have been similar types in the past and the is a similarity to the mobile stairs that are used in some places. Just put a ramp (Extendable) on the back of a suitable vehicle and drive it up to the aircraft.

As I see it, tech on the aircraft has to be carried which means more fuel and or less cargo.
 
It's a amazing the number of times Boeing tried to ram their 747 into USAF. Their only success of course was AF1 VC-25.

747 ICBM launchers
747 cruise missile carriers
747 flying aircraft carrier
...
747 losing to KC-10 (1979)
747 losing to C-5B (1983)
747 instead of C-17 if it was canned (1993)

And CRAF 747s, obviously.

While Lockheed stood strong with the C-5A/B for the military, Boeing in the end had a far better bargain losing CX-HLS and going civilian.
747 vs C-5: 120 to 1500.
 
Their only success of course was AF1 VC-25.

Also the four E-4B National Emergency Airborne Command Post (NEACP) aircraft and, arguably, the YAL-1 Airborne Laser (which was bought by the Air Force but never reached service).
 
If Boeing gets to develop their CX-HLS proposal, they'd be so busy doing that they wouldn't have time to work on another massive project (the 747) at the same time.
 
In an ideal world Boeing would get both - main problem would be, Boeing CX-HLS would make a bad "civilian" 747-200F and an even worse airliner.
On a different topic - at least the MC-747 shows what kind of max performance could be extracted of a reinforced 747-200F airframe.

What is also interesting is the last paragraph. 200 000 pounds air drop, single piece ?

I did some research about the comparable C-5 Galaxy record airdrops and found
a) the famous 1974 missile drop was 86 000 pounds
b) another airdrop in 1989 - nearly 200 000 pounds but split in large chunks: four 20 tons tanks and a load of paratroopers.

Is there a limit to how heavy a C-5 can air drop ? I mean an airframe or CG limit to the C-5, not the payload or parachutes.
 

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