Take Lufthansa for instance they are getting rid of all there 747-200 freighters for all MD
-11 fleet. I work in the cargo industry so I see alot of carriers using the MD
-11. I list a few reasons please comment on them, good and bad:
1.I find the turn around times on MD
-11F are quicker than 747F
2.But I find MD
-11F are heavy on maintenance.
3.The reason why it failed in pax service it promised alot and didn't deliver mostly with payload and range. As in freighter operations you really don't see aircraft at MTOW because they usually bulk out before maximum weight. When shipping you pay for the volume weight, so a plane that can hold lets say 80 tons but has only 20 tons on board but is bulked out is still taking money in for 80 tons.
To figure out volume weight here is an example:Lets say a box is 60X60X60in and weighs 250kg.Now multiply 60X60X60=216,000 now divide that by 166=1301 now this is the VW
in lbs now take 1301 and divide by 2.2046 and that gives you 590kg now this is what the airline gets paid. So in freighter ops you dont need weight you need volume. To conclude I think this is why the MD
-11F is such a sucess in cargo