Now that I have scratched my head for the requisite period of time, the errors in FLEXJET's URL link reference have become clear.
The manual linked to by FLEXJET contains expressions for index and %MAC both of which contain errors which appear to have been generated by a combination of (perhaps) carelessness and typographical mistakes.
Following the reference nomenclature, the correct equation for index is
I = (W x (Sta - Ref Sta))/C + K
This has been printed in the manual incorrectly by substituting a minus sign for the multiplication sign after W, probably a simple typo. In addition the divisor line has been omitted.
The manual's logic is then a bit unusual in that the IU equation is solved for Sta which results in
Sta = Ref Sta + ((I - K) x C)/W
which is then plugged into the standard %MAC equation of
%MAC = ((Sta - LEMAC)/MAC) x 100
which gives
%MAC = ((Ref Sta + ((I - K) x C)/W - LEMAC)/MAC) x 100
which can be adjusted to read
%MAC = (Ref Sta + ((I - K) x C)/W - LEMAC)/(MAC/100)
Unfortunately, somewheres along the way
(a) I was replaced by 1
(b) the W got lost in the complexity. Interestingly, this error is in the manual but in FLEXJET's transcription the W is resurrected .. I am not too sure how that came about .. ?
Two things come out of this ..
(a) be wary of indiscriminately pinching something from the net as it might be wrong ...
(b) I wouldn't choose to go down the algebraic path chosen by this particular operator ...
Last edited by john_tullamarine; 15th Mar 2006 at 10:38.