Passengers can have a shot at estimating too, provided that broad brush figures are acceptable.
Aircraft do not fly very far or very economically [if they can fly at all] “fully loaded” and with “full fuel”.
A closely guarded secret is the average customer, for example 178 people might weigh in at 19 tonnes complete with bags and a sack of mail. Salad dodging pie-eaters, every last one of them.
A substantial part of the all-up weight of a jet aircraft is the fuel. For the sake of discussion suppose the 737 burns off 1020kg/hr/eng on average long range. That is a pretty sweeping statement but let it go for the moment. Empty of useable fuel it weighs 44 tonnes, loaded with 19 tonnes takes us up to 63 tonnes.
Various stipulations govern how much fuel is needed on landing but we’ll say that this particular hypothetical flight touches down with 5 tonnes remaining. We are up at 68 tonnes already and have not even moved 2.54 centimetres.
Here is a useful reference intended for civil engineers, not pilots or flight planners.
http://www.boeing.com/commercial/air...ps/737sec3.pdf
According to this document the 737-800 has “room” for up to a further 11 tonnes before some one or other restriction is broken. Of this some 2.4 tonnes will be needed to take-off and climb and to keep figures “round” 600kg for a straight-in greaser of a landing leaving us with 8 tonnes for cruise and still have a “generous” reserve. Allowing for climb and descent of 83 and 117nm respectively the figures so far suggest you have a total range for 2000nm in still air. Coincidentally what the Boeing civil engineers’ tables come up with.
Pilots may now suck their teeth and say Hmmm. But there again remember the tables I refer to are for airport planners who are mainly interested in how big and how heavy things are likely to be, most of the time. Don’t shoot me, I am only the messenger.
Pick any permutation of normal, hot, dry, wet conditions and enjoy. If your aircraft is liable to encounter sustained icing conditions the company you fly with are most unlikely to have bought the wingletted version.
I must say 2000 metres does sound short but real life flight planning is not done on the back of a fag packet as I have done here.
This is not meant as a tutorial, just as a fun scan through some ideas and broad principles.
Best Regds
The “E”