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

[Archibald]

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]

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.

 

[riggerrob]

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]

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 !)

 

[Archibald]

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.

 

[Foo Fighter]

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.

 

[Archibald]

You mean, a ground based vehicle a bit similar to the one used when loading through the nose door ?

 

[apparition13]

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.

 

[Foo Fighter]

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.

 

[Archibald]

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.

 

[TomS]

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).

 

[marauder2048]

Although that instantly kills the 747 of course.

Why would that be the case?

 

[Hobbes]

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.

 

[Archibald]

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.