Re: MD-17 vs. MD-11F/DC-10F

Date:         28 Dec 96 14:20:08 
From:         "Dave Starr" <>
Organization: Base Exterminating - Out, Rodent!
References:   1 2 3 4 5
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> I dont see a cargo ramp as being much more complex then a standard
> cargo door.  Bigger hinges/etc, but not that much more complex.
> And while there is some wieght penalty, the cargo door is shoved
> up under the tail, which is usually just 'wasted' space anyway.
> Being able to just slide the pallets right out the back and onto
> a truck is much more efficient then slide one out, scissor lift it
> and then slide it onto a truck.

There are some good points in this and the earlier messages in the chain,
but a bit of apples vs oranges has crept in here.  The cargo pressure door,
ramp, and petal doors on the C-17 (and the C-5 and C-141 predecessors) are
extremely complex, heavy and maintenance intensive.  They are built to
accommodate heavy equipment (loaded trucks, main battle tanks, etc.).
There is no denying that a roll-on/roll-off setup would be more efficient
for a carrier like FedEx, but the current military cargo ramp system would
be a terrible match for the job.  It's illuminating to note that unofficial
Air Mobility Command (formerly MAC) rules of thumb count a KC-10
(high-mount, side cargo door only) as equal to 1.5 to 2 C-5s in efficiency
- mainly because the complex systems of the C-5 (especially the front and
rear cargo doors and kneeling landing gear) break so often that the KC-10
delivers more tonnage in a given time frame.  (argument invalid if
considering cargo such as main battle tanks).

Lockeed made serious attempts to market civilian versions of the -141 and
-5 with little success.  The L-100 civil Hercules has attained some success
with a rear cargo ramp, but also without petal doors.