Interpolation of fuel figs
 

just wondering what method people use for the "interpolation" of fuel figs in flt planning.
Eg if a ac suffers a 4% penalty for every 4000ft below it optimum, and 10% penalty at 8000ft, what would the penalty be at 5200ft below???

iv been trying to factor each one in a table eg

below by / penatly
4000 ...... 4
5000 ...... 6.5
5250 ...... 6.63
5500 ...... 6.75
6000 ...... 7
8000 ...... 10

but im not getting an accurate enough answer, is this the wrong method or just poor exicution of the correct one? any help would be appreciated.

If I was serious but the only thing available was a lookup table like that, I'd get some graphpaper, plot the curve, and read off that. (Or do the same in, say, Excel).

If playing safe, I'd just use the more conservative value either side.

If being lazy, I'd do an O-level standard linear interpolation, and round up!

G

I reckon the answer is 5.8. (((6/4)*1.2)+4)

I would agree with Piltdown Man. I dont think they would be asking for much more than that.

Was this an exam question? If so I dont think they would be expecting us to start plotting graphs!:eek: