Instrument Exams

Studying both for the FAA/IR and a UK IMC rating. The UK IMC give a
good clue to what it is. It allows flying in IMC but with limited IFR
privileges. Essentially it is a get home safe rating. UK weather is so
unpredicable that it is feasable to get caught out easily even with
the most thorough of planning.

Enough of that. Been doing test papers for the respective knowledge
tests. The FAA questions are quite straight forward and I am doing
good. Getting 75% right but will go for the test when I consistantly
get 85+%.
The IMC is a whole other ballgame where the theory can be a little bit
too much. The passmark is 72%.

Here is a fantastic question. No prizes for getting the right answer
(with explaination) but anyone fancy a go?

Given the following:
Ground speed 90kts
aircraft altitute 6000ft
VOR transmitter at mean sea level
Tan 40° = 0.839
assume 6000ft = 1nm

Theoretically, for approximately how many seconds would you expect the
morse identifier to be inaudible within the cone of silence if the
aircraft is tracking directly TO the VOR followed by its reciprical
directly away FROM the VOR?

A - 7 seconds
B - 20 seconds
C - 67 seconds
D - 100 seconds