|Quoting Swallow (Reply 1):|
Belly cargo capacity:
345: 32 LD3 containers/11 pallets and MTOW of 820,100 lb
772: 32 LD3 containers and MTOW of 656,000 lb
The 345 does not look too shabby, but I am no loadmaster!
Actually the A340-500 has a maximum capacity of 30 LD3, 18 FWD and 12 AFT...
777-200ER 32 LD3 18 FWD and 14 AFT
777-300ER 44 LD3 24 FWD and 20 AFT
The question of efficiency is answered not only by how much you can carry but what it cost you to carry it on a specific basis. Yes in a simple analysis MZFW is available but that is not the entire story. Realistically that small difference in capacity is significant and here is how.
First in terms of cargo you have to consider the useful volume after passenger baggage. Lets take TAM as an example. Their A340-500s have 267 seats. If there are no lower ULD hold crew rest a calculation of baggage space required at 100% Load Factor would be as follows 267 pax X 1.3 bags per pax = 347 bags. Assuming that baggage is loaded into LD3s, a typical LD3 is capable of containing up to 37 bags per unit. 347 bags / 37 bags per container yields 9 LD3s needed with 14 bags left that can go in the bulk. From the available ULD configurations a 6 Pallet 12 LD3 configuration will satisfy our space requirements. This configuration, using M size pallets, would leave 6 Pallets and 3 LD3 for cargo use after baggage is loaded. The useable cargo volume is nominally 81 cubic meters using rectangular counrour for the pallets and full contour for the LD3s. Given the realities of cargo space utilization the best hope would be for 80% of the maximum volume to be utilized even when all available ULD are loaded with cargo. This gives us a total loaded volume of 65 cubic meters.
Now the average density of lower deck general market cargo is around 155 Kg per cubic meter these days. 155 Kg/cum X 65 cum gives us 10,075 KG
of gross cargo weight the ULD tare of 930 Kg works out to a gross cargo load in ULD of 11,005 KG
for the Airbus. Added in with a full pax load of 25,400 KG
including baggage tare gives us a total traffic load of 36,400 KG
well under maximum payload for the route/flight time effective distance.
Now quickly through the numbers for the 777-200ER and 777-300ER with relative seating.
9 X LD3 bulk baggage
ULD Config 7 Pallets 10 LD3
Cargo Config 7 Pallets 1 LD3
Cargo Max Volume 84.5 cum
Practical cargo Volume load 67.5 cum
Net Cargo payload 10,500 Kg
Gross Cargo Payload 11,300 Kg
Total traffic load 37,000 Kg
11 X LD3 bag use
ULD Config 10 Pallets 3 LD3
Cargo Max Volume 127 cum
Practical cargo Volume load 101.5 cum
Net Cargo payload 15,700 Kg
Gross Cargo Payload 17,100 Kg
Total traffic load 46,000 Kg
Now that we have the loads lets look at efficiency
For cargo on passenger airplanes the incremental cost of operation basically boils down to the fuel used for the extra payload. At the specified range and this week's Singapore spot market price for Jet A the cost for carrying a single kilo of cargo would be as follows in US Cents.
This is only reflective of the cost in fuel to carry a kilogram of payload over and above the given passenger load. To bring things full circle, how much more could a 777-200ER/-200LR carry vs an A340-500 over a generic 5,500nm effective air distance? About 4-6% more in practical terms and the 777-300ER would do better by more than 50% against the rest. In terms of the efficiency at carrying the excess payload basically a wash between the 777-200ER/-200LR and A340-500 as any small percentage fluctuation in space utilization would defeat the differences in fuel necessary to carry the extra load. As far as the operator is really concerned they will take the extra space always, every time. To the cargo side it does not make sense to give up space for anything so the 777-200ER/LR wins by a nose in that analysis.