Is the Breguet Range Equation Enough to Determine Aircraft Range?

[earthgoodboy]

hi all,

Im currently a aerospace engineering and I have some questions that I have been wondered about the range equation.

I just studied about the breguet range equation (R=v/sfc L/D ln(wi/wf)). The equation is pretty simple within many assumptions such as constant speed constant L/D... How can the manufacturer such as Boeing or Airbus come up with the quoted range in the aircraft's specification? Since the breguet's equation is quite ideal and far from realistic, should there be a better way to determine the range?

is there a more precised formula has been developed? or the value just comes from the flight test alone?

I also think that there are many conditions of payload/fuel load, but how come the manufacturer come up with only 1 range in the specification? what condition do they usually use?

I know there are many questions and takes long to answer, if anyone could suggest me articles or books would be already much appreciated.

thanks

 

[anorlunda]

Why should they limit themselves to a single equation?

It is easy to visualize a simulation of an airplane that takes in many factors, and that could calculate range for a particular route.

But remember that the advertized range must ignore route, weather and many other factors. I would say it is more of a marketing thing. Probably the engineers calculate a few dozen test cases, then the lawyers take the average and multiply by 0.7 as a safety factor, then the marketing people argue to multiply by 1.1.