Perfromance Questions...help

[Si]

1. SFC will

a) Inc if C of G is moved further forward of the C of P
b) Dec if C of G is moved further forward of the C of P
c) Not affected by C of G
d) Only be affected by C of G, if its position is behind the C of P

I know the answer but wondered if someone could give me the answer WHY.

P.S If any of u did your ATPLs at Oxford was the Performance feeback any good?

[fokker]

As a rule:

If Cof G moves aft (within limits), the tailplane is required to 'lift', contributing to overall lift required, offloading the mainplane and improving economy. A fwd CofG requires the tail surfaces to 'push down', so the mainplane has more to do and the aircraft is, overall, less efficient.

Of course, beware: a very far aft CG will render the a/c uncontrollable, ultimately. (cf the Channex F27 crash in Guernsey)

Hope this helps.