Halo Jaideep.I am replying from UAE.Where is your location?
My background is both Airline Commercial Planning and Flight Operations.FROM YOUR QUESTION i suspect that you are from a commercial background studying fleet evaluation and fleet planning(rather than Flight Palnning!)
I had met the term Stage Length whilst practicing Aircraft Economics(COMPARING AIRCRAFT PERFORMANCE FOR THE PURPOSES OF EVALUATION).I recommend that you search google on Aircraft Economics for a more comprehensive explanation where diagrams shall reinforce your understanding of the matter.STAGE LENGTH my friend is defined as the comprehensive distance from Taxi-out to taxi in, including all the standard STAGES of FLIGHT(Taxi out, take off, climb, cruise, step climb, descent, hold, aproach, land, and taxi -in).In IATA standards it is a Great CIRCLE TRACK DISTANCE(which by definition is the shortest distance across the earth between any selected points).This is for approximation purposes as the actual distance between city pairs may be(and most likely is) longer due to airways structure and the need to intercept best seasonal prevailing winds in the name of fuel conservation planning- where flight planing comes in to play old boy!These GC track distances are documented in a certain IATA (not ICAO!)document which for now escapes my mind but you can consult with in IATA's website.
To answer you the second question:Endurance,WHICH IS IN THE HEART OF FLIGHT(Fuel Planning in fact) for Search and rescue purposes should you exhaust your fuel supply;the search and rescue party as per your flight plan endurance declaration-shall know the furthest that you could have traversed under the prevailing atmospheric conditions! IT SHOULD-BUT DOESNT, ACCOUNT FOR YOUR LIFE SUPPORT SUPPLIES FOR ENSURING SURVIVAL IN TERMS OF NUMBER OF DAYS OF COURSE, RIGHT??
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ENDURANCE is a fuel planning problem where consideration for your still air fuel consumption rate should be compounded with the prevailing wind velocity across your selected track.The formulawhich I had read- prescribed to you by some of our colleagues does apply to general aviation light category aircraft but fuel weight burn-off tables from your transport category performance charts will have to be consulted if dealing with airline equipment.The wind velocity might have to be updated if over a long track over uninhabited regions say across Atlantic, Deserts, Polar areas via remote stations including ships.
I hope that you have gained some useful insights here.It certainly has been my pleasure to respond to your important questions.I guess your next question might be..."what is payload-range?" If I guessed correctly that you are studying aircraft performance for comercial purposes.Well
, that calls for a longer response with appropriate diagrams altogether!
cherio old chap!
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