posted on Sep, 7 2007 @ 04:39 PM
Originally posted by RichardPrice
Even taking into account the above posts, there are a huge number of other factors that determine a planes range:
- airframe efficiency
- time of day
- angle of attack
What may be deceptive about Breguet's equation is that most of these factors are actually included. Airframe efficiency is included in Cl/Cd,
temperature and time of day are included in the atmospheric density, and angle of attack would actually be determined by the weight of the aircraft,
the velocity, the atmospheric conditions, the lift coefficient, and the wing area. Note that there is some optimal cruise speed that hasn't been
addressed by Breguet's equation, that's a separate issue.
Things like payload would be included in the gross and dry weights, and the fuel would be factored into the specific fuel consuption. A better fuel
will provide a better (lower) specific fuel consuption. Of course there are all kinds of other factors that influence it, and it's not necessarily
trivial to even estimate it for a given engine.
The trick is getting a good estimate for things like Cl/Cd, specific fuel consumption, propeller efficiency, and so on. There are a number of
"hidden" factors, some of them can be easy to determine, some not, but if you can come up with a good estimate of the terms in Breguet's equation,
and if you can handle the assumptions made, it will give you a good estimate of the aircraft range, and I think that's all this guy needs. I'm not
sure he realized the rabbit hole he was going down by asking a seemingly simple question, but that's life I guess.