Hola ClipperCargo -
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For the 727, the above figures are correct, as well as the 747.
But think of some factors with a multiple-stop 747 cargo aircraft.
And is your 747 cargo a "real freighter"...?
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There are mainly 2 types of freighters for the 747, if 200 or 400 does not matter.
What matters is this. Real 747 freighters have a NCD nose cargo door.
They can load pallets from the front nose door (with reduced height).
Reduced height due to the upper deck floor being on the loading path.
And they also have a SCD side cargo door, in the rear of the fuselage.
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A NCD "nose loader" 747F is a nice machine at times.
Especially to carry long pipes for the oil industry.
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Freighters converted from former 747 passenger airplanes only have the SCD side cargo door.
Their designation is 747-200SF (for "special freighter").
The pallets in the main (rear) part of the cabin can be higher than those loaded from the nose.
But you might also have to play "musical chair" with your pallets along the route.
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Example -
You are to load some heavy pallets in the mid-cabin position.
Not all pallet positions can accommodate the heavier pallets.
So you have to locate pallets accordingly.
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Example -
Where (along the route) are they to be loaded, or offloaded.
Maybe a few pallets need to be moved (or even taken out) to move others in and out.
Then, be careful with balance on the ground and always install a tail skid.
Or you might soon have a 747 on its tail with a nose up as a DC-3...
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So yes, you could onload/offload pallets in 60 minutes in a 747.
But in some cases, might take you 90 minutes, and lots of planning.
A fly-along loadmaster always recommended, besides a A&P mechanic.
If you do not know it, a 747-200F has a max payload of some 110 metric tonnes.
With full tanks, you could only load about 60 metric tonnes.
For pounds, multiply metric tonnes by 2205.
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Nice of you to use "Clipper" - makes my PanAm heart beat.
Happy contrails, and happy 2009.