|Quoting PolymerPlane (Reply 45):|
You don't even know what he uses to come up with this numbers. If you care enough to read other people's comment, widebodyphotog DOES NOT solely use the payload-chart to come up with this numbers. He actually uses computer program generally use in aviation industry to come up with this numbers, with actual flight parameters.
I think you should sit down and be more careful before criticizing one's work. Do you think you're the only one in this forum that has actually analyze his work?
I would give someone with as high of a respect rating as WBP some benefit of the doubt. I believe it was pointed out back during the 747 ADV discussions that WBP uses a good but not the best mission planning system with the best systems used by the airlines themselves. Some of the differences were pointed out between WBP and some other posters that do mission planning. (Was it Zeke?) SFC and plane performance changes throughout the flight, but the modelling done by the system varies between systems with the simpler programs having fewer stages for the climb than the fancier systems, etc. However, it is my understanding that WBP works in fleet planning where his customers are making the decisions on which planes to buy.
It appears to me that his charts are some of the best available in the public domain for many of the airlines. Of course, any analysis is limited by the available data. For example, very little data on the 350XWB performance has been made available to planners outside of Airbus. Meanwhile, a lot is known on the 330 and 777.
I think on the referenced comparision every attempt was made to match up the total payload (pax + bags + cargo + crew) were the same and the distance flown also the same so fuel consumption is comparable. Yes, at a differnent payload or range, the fuel consumptions are different. For example he compared the 777LR with the ER models and showed that the LR made economic sense to use on flights over 5,000 nm (as I recall) but not on shorter flights as its cruise is optimised but the climb portion is less efficient than the ER wing.